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  • richardmitnick 3:01 pm on November 20, 2021 Permalink | Reply
    Tags: "Europe’s space agency dreams of launching its own astronauts amid ambitious ‘Accelerator’ plans", Science Magazine   

    From Science Magazine: “Europe’s space agency dreams of launching its own astronauts amid ambitious ‘Accelerator’ plans” 

    From Science Magazine

    19 Nov 2021
    Daniel Clery

    1
    The European Space Agency would like to bring a sample of Saturn’s icy moon Enceladus back to Earth as part of the search for life elsewhere in the universe. Credit: JPL/Caltech-NASA (US)/ Space Science Institute.

    The European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) wants to push the pedal to the metal in its efforts to exploit the cosmos. Ministers from ESA’s 22 member states today put their names to a manifesto that calls for prioritizing three urgent initiatives, dubbed “Accelerators,” aimed at tackling the climate crisis, responding to natural disasters, and protecting spacecraft from orbital debris and damaging space weather. The manifesto aims to speed up plans for a “digital twin of our planet”—an all-encompassing computer model of the entire Earth system—to help figure out how to eliminate greenhouse gas emissions by 2050.

    “In times of unprecedented challenges facing Europe and the world at large, it is the moment to contribute with bold, shared ambitions to solutions enabled by space,” write the ministers, who met in Matosinhos, Portugal.

    The Matosinhos Manifesto spells out the three initiatives, which it says could “speed up the use of space to solve today’s biggest challenges.” The document—which uses the terms “accelerator” or “accelerating” 16 times in its four pages—includes no specific funding pledges. But it does contain two tentative missions proposals. One is that Europe consider developing its own system for launching astronauts into space. (European astronauts currently fly on craft launched elsewhere.) The other is that ESA send a probe to an icy moon of Jupiter or Saturn and return to Earth with samples. The goal of that mission, ESA Director General Josef Aschbacher told a press conference today, is to answer the question: “Is there life out there?”

    Unlike The National Aeronautics and Space Agency(US), ESA does not have to deal with annual uncertainties about its budget; it gets multiyear spending commitments from its members. But every few years ESA must get 22 governments to come to a consensus on future spending. Its next budget-setting meeting is in November 2022, and today’s gathering was an opportunity for Aschbacher, in the director’s chair since March, to lay out his vision.

    The three Accelerators are a big component. The first proposes enhancing the use of data from Earth-observing satellites to tackle the climate crisis, as well as building a digital replica of the planet, which would allow forecasters to predict floods, fires, and droughts days or even years in advance, as well as assessing the impacts of the heating climate. The second calls for making better use of imagery and other data collected from space to deal with natural disasters, such as the floods and wildfires that ravaged Europe this year. The third envisions new ways to defend crewed and robotic spacecraft from space junk orbiting Earth, and from blasts of radiation and charged particles from the Sun.

    ESA already has vigorous programs in all these areas, but the manifesto asserts that “right now is the moment to contribute with bold, shared ambitions to solutions enabled by space.”

    In proposing that Europe develop its own crewed spacecraft, Aschbacher pointed out that currently only the United States, Russia, and China—plus possibly India soon—can launch astronauts into orbit. “It’s a political decision,” he said, “but does Europe want its own capability?”

    Europe has toyed with this idea before. In 1987 it approved the development of the Hermes spaceplane, like a miniature version of NASA’s Shuttle, that would be launched on top of an Ariane 5 rocket. Spiraling costs, and Russian Space Agency offers of cheap rides in Soyuz craft, led to its cancelation in 1992.

    ESA is now developing plans for missions to visit icy moons of the gas giant planets [Science] as part of its Voyage 2050 science program. But Aschbacher suggested that, because of the desire to discover possible life in the Solar System, those plans should be expedited and that any mission should bring samples home.

    Planetary scientist Athena Coustenis of The Paris Observatory [Observatoire de Paris – PSL Centre de recherche en astronomie et astrophysique](FR) says European teams are focusing on a visit to Enceladus, a moon of Saturn with a liquid water ocean just below its surface. The NASA-ESA Cassini mission flew past Enceladus multiple times and sampled hydrocarbon-laden water thrown up from its surface.

    National Aeronautics and Space Administration(US)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ASI Italian Space Agency [Agenzia Spaziale Italiana](IT) Cassini Spacecraft.

    It is “currently the most viable candidate for a habitable environment in the outer Solar System,” she says. (NASA, in contrast, is targeting Jupiter’s moon Europa.)

    To bring a piece of Enceladus back to Earth, European researchers hope to use similar techniques to those in the upcoming NASA-ESA Mars sample return mission [Science]. From “a sample return we will learn much more about habitable conditions in the undersurface liquid water ocean of the moon,” Coustenis says.

    Whether Europe will ultimately come up with the money to realize the space agency’s need for speed, however, won’t be known until a year from now at the earliest.

    See the full article here .


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  • richardmitnick 10:12 pm on November 10, 2021 Permalink | Reply
    Tags: "Is the end in sight for famous dark matter claim?", ANAIS-112 detector, , COSINE-100 Dark Matter Experiment, DAMA Dark Matter experiment, , , Science Magazine   

    From Science Magazine: “Is the end in sight for famous dark matter claim?” 

    From Science Magazine

    10 Nov 2021
    Adrian Cho

    New data cast more doubt on controversial result from the DAMA experiment and an alternative explanation of it emerges.

    1
    Dark matter particles should generate flashes of light in the COSINE experiment’s sodium iodide crystals. It aims to test a similar experiment’s dark matter claim.Credit: CHANG HYON HA.

    The drama of the world’s most controversial dark matter claim may have reached its last act, if not its final scene. For 2 decades, physicists with an experiment called DAMA have claimed that particles of dark matter—the unseen stuff whose gravity appears to bind our galaxy—are bumping into atomic nuclei in their subterranean particle detector, even as other dark matter hunts come up empty. Now, physicists with a detector called COSINE-100, designed to mimic DAMA, present the most direct refutation yet of the findings. And in 2020, theorists identified a way in which the DAMA signal could have arisen inadvertently in the team’s analysis.

    Yale COSINE-100 at Yangyang underground laboratory in South Korea

    The DAMA team rejects both claims. Rita Bernabei, a physicist at Tor Vergata University of Rome [Università degli Studi di Roma “Tor Vergata”](IT) and DAMA’s leader, declined to be interviewed. But she dismissed the new explanation in an email: “We have already demonstrated that the assumptions there reported are untenable and the conclusions are worthless.”

    The Milky Way is thought to whirl within a vast cloud of dark matter, which could consist of hypothetical weakly interacting massive particles (WIMPs). As the Solar System orbits the galactic center at 225 kilometers per second, Earth presumably plows into a wind of WIMPs. Because our planet also orbits the Sun at 30 kilometers per second, the wind should strengthen slightly when Earth is moving in the same direction as the Sun, in June, and abate when it’s moving the opposite way, in December.

    DAMA physicists have long claimed to see this yearly cycle in their detector, which now contains 25 10-kilogram crystals of thallium-doped sodium iodide. Each crystal produces a flash of light when a particle pings a nucleus. The DAMA team says that, in a low-energy range that corresponds to WIMPs, the number of collisions has gone up and down each year since observations began in 1995.

    Other detectors see no such thing. But those experiments use different target materials. So groups have built sodium iodide detectors that can test the DAMA result in an apples-to-apples comparison. One is COSINE , which comprises eight crystals totaling 100 kilograms and has been taking data since 2016 in South Korea’s subterranean Yangyang Laboratory. Since 2018, COSINE has improved its sensitivity 100-fold, says Hyun Su Lee, the team’s co-spokesperson and a particle physicist at Institute for Basic Science of Korea [기초과학연구원](KR). But in 1.7 years of data, they see no sign of WIMPs, the researchers report today in Science Advances.

    There’s a caveat. The new COSINE analysis does not look for the annual cycle in the event rate, but simply for an excess number of low-energy events. That tiny signal would appear on top of a much larger background of events caused by ordinary particle radiation from sources both inside and outside the crystals. So the analysis depends on researchers’ ability to model the subtle details of those backgrounds, Bernabei notes.

    COSINE is not the only experiment testing the DAMA result, however. The ANAIS-112 detector contains nine sodium iodide crystals with a total mass of 112 kilograms and has been taking data in Spain’s Canfranc Underground Laboratory since 2017.

    Three years of data show no annual cycle in low-energy events, ANAIS researchers reported on 27 May in Physical Review D. However, the uncertainties were slightly too high to rule out the DAMA signal, says María Luisa Sarsa, a physicist at The University of Zaragoza | Universidad de Zaragoza](ES) and ANAIS co-leader.

    If the DAMA signal isn’t real, “The field of particle physics owes itself to find out what DAMA is seeing,” says Reina Maruyama, a nuclear particle physicist at Yale University (US) and co-spokesperson for COSINE. And last year, Dario Buttazzo, a theorist at the Pisa section of The National Institute for Nuclear Physics[Institutio Nzaionale di Fisica Nucleare](IT), and colleagues identified a way in which the DAMA team might have inadvertently created the annual cycle.

    DAMA researchers collect data in yearlong runs. To make the variation in each run stand out, they subtract the average rate over the year from the event rate measured each day. But if the event rate steadily rises or falls year after year, the subtraction can turn a steady trend into an oscillation, Buttazzo says. For example, if the rate were increasing by 1% every year, DAMA’s method would produce a signal that begins each run at –0.5% and ends each run at +0.5%.

    “If you do the analysis like DAMA was doing it, and if the background has a particular feature, then you could have such an effect,” says Buttazzo, whose group reported its analysis in the Journal of High Energy Physics on 21 April 2020. But he cautions that because DAMA hasn’t published its data, “we cannot know if this effect is actually there or not.”

    Still, the COSINE and ANAIS papers suggest the issue could be important. The ANAIS detector’s total event rate is decreasing steadily as short-lived radioactive nuclei in the crystals decay away, says María Lucía Martínez Pérez, a physicist at the University of Zaragoza and co-leader of the team. COSINE sees a similar steady decline, Lee says.

    Closure could come soon. In weeks, COSINE will release a 3-year annual cycle analysis, Lee says. ANAIS’s Sarsa says that by next summer, “We expect to have a high-impact publication with the average rate measured over the year with all 5 years of data.” That may be enough data, she says, to bring the curtain down on the DAMA claim.

    See the full article here .


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  • richardmitnick 3:56 pm on September 1, 2021 Permalink | Reply
    Tags: "Fate of giant telescopes in the balance as U.S. astronomers debate priorities", European Southern Observatory(EU) ELT, Giant Magellan Telescope (GMT), , Science Magazine, Thirty Meter Telescope (TMT)   

    From Science Magazine: “Fate of giant telescopes in the balance as U.S. astronomers debate priorities” 

    From Science Magazine

    1 Sep 2021
    Daniel Clery

    1
    The Giant Magellan Telescope (left) and the Thirty Meter Telescope, shown in artists’ concepts, are making a joint pitch for federal funding.GIANT MAGELLAN TELESCOPE/GMTO CORPORATION; TMT INTERNATIONAL OBSERVATORY.

    Roughly every 10 years since the 1960s, U.S. astronomers have provided a valuable show of consensus to U.S. funding agencies and Congress by agreeing on which questions and new facilities are critical to the field. But the current “decadal survey,” known as Astro2020 and scheduled to be published at any time, faces a particularly knotty question, one that could settle whether the United States stays in the front rank of ground-based observing. Should The National Science Foundation (NSF)(US) come to the rescue of two struggling private projects to build giant optical telescopes in exchange for a chunk of observing time?

    The future of the Giant Magellan Telescope (GMT) and the Thirty Meter Telescope (TMT) likely depends on whether the survey recommends that NSF spend what sources put at $1.8 billion to support a recently forged partnership between the projects. If it does, other proposals could lose out, such as a ­continent-spanning radio array and detectors for neutrinos and other cosmic particles. (Space missions are ranked separately.)

    Understandably, astronomers are divided. The GMT-TMT proposal “is critical for the field to thrive,” says John O’Meara, chief scientist of the W. M. Keck Observatory. With Europe pushing ahead with its own giant telescope, “If a federal partnership does not happen, I believe that the U.S., which has been the international leader in the field of astronomy for a century, will pass that role on to Europe,” says Wendy Freedman of The University of Chicago (US). [This is what happened with High Energy Physics when in 1993 California pulled out of support for the Superconducting Super Collider and momentum passed to CERN in Geneva.]

    [A bit of complexity: The TMT is Northern Hemisphere, the GMT and the ELT are both Southern Hemisphere. So the TMT is not “competing” with either of the other two giant telescopes.]

    But Richard Ellis of University College London (UK), former director of the Caltech Palomar Observatory (US), believes rescuing both telescopes would cost “too much money and would eclipse so many other things.”

    For ground-based optical astronomers giant telescopes with mirrors about 30 meters across are the obvious next step after the huge advances made with today’s 10-meter scopes. O’Meara says there is no other way to image an Earth-like planet around a red dwarf star, for example. “No matter how tricky you get, the laws of physics overrule you,” he says. “Aperture is king.”

    Telescope designers have been planning such behemoths since the 1990s, and the European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte](EU) (CL) is laying the foundations for its 39-meter Extremely Large Telescope (ELT) on the summit of Cerro Armazones in Chile, with first light due in 2027. But divisions over technology and funding have hampered the two U.S.-led projects. The TMT, to be built in Hawaii by the California Institute of Technology (US) and The University of California (US), will have a honeycomb mirror built of 492 hexagonal segments. In contrast, the GMT, led by The Carnegie Institution for Science, will arrange six 8.4-meter mirrors around a seventh, giving the Chile-based telescope an aperture of 24.5 meters. The projects had early talks about joining forces, but “there was no desire to abandon their telescopes,” Ellis says. “Once money started flowing, it was impossible to merge.”

    The 2000 decadal survey rated a giant segmented-mirror telescope (essentially the TMT) as the No. 1 U.S. priority in ground-based projects. NSF started discussions with the TMT about partnership in the project, but backed away after the GMT objected. In the 2010 decadal a giant ground-based scope dropped to No. 3, behind a large survey telescope and an instrument innovation program—a decision that essentially killed federal involvement for another 10 years.

    “That really damaged the momentum of the project,” says Garth Illingworth of The University of California-Santa Cruz (US).

    Both projects set out to raise their own funds, but neither has sufficient money so far. The TMT has also faced continued opposition, including legal challenges, from Native Hawaiians to building such a large structure on Mauna Kea, which they consider sacred.

    For the current decadal, the projects have finally united into a two-telescope package that would give all U.S. astronomers access to at least 25% of the observing time in exchange for the $1.8 billion (a figure that is not officially confirmed). This deal, dubbed US-ELT, would give U.S. astronomers an advantage over Europeans: front rank telescopes in both the Northern and Southern hemispheres. “The U.S. really does need [giant telescopes] to follow up on other investments on the ground and in space,” Illingworth says.

    Those include the James Webb Space Telescope (JWST), set for launch later this year [late by ten years, originally to be launched in 2011].

    The JWST should revolutionize astronomy by picking out objects including the earliest galaxies with its pin-sharp infrared eyes, but fine-grained spectrometers on the ground will be needed to follow up on some discoveries. Then there is NSF’s Vera C. Rubin Observatory in Chile, a survey telescope that from 2023 will carry out a census of the sky nearly every night, identifying thousands of objects demanding closer investigation.

    “It would be an admission of defeat to let Europe take over this area,” Illingworth says.

    Others say the U.S. giants are too far behind to avoid that outcome, and the costs are prohibitive. “How can you make a sales pitch for two telescopes when the rest of the world has one?” Ellis asks. Astronomers also worry about the consequences of funding US-ELT for projects such as a next-generation upgrade of the Very Large Array Radio Telescope (ngVLA) in New Mexico into a continent-spanning network of 263 dishes.

    “The ngVLA is no silly idea, it’s something we must do,” O’Meara says. The science cases behind upgrading the U Wisconsin IceCube Neutrino Observatory(US) at the South Pole and building a next-generation detector for the cosmic microwave background radiation are similarly compelling.

    The decadal may also decide that U.S. astronomy doesn’t need to pursue an endless quest for ever-greater expanses of glass on the ground. Some astronomers think the greatest potential for discovery lies in modest new telescopes, or upgrades of older ones, with multiobject spectrographs that can scrutinize thousands of objects at once. “It’s a different vision,” says Ray Carlberg of The University of Toronto (CA), and one that requires a team-based approach more familiar to particle physicists. “So much more science can be done with large groups of collaborators working together on a range of projects,” says Jennifer Marshall of The Texas A&M University (US), College Station, project scientist of the proposed [?] Mauna Kea Spectroscopic Explorer.

    The 20-strong decadal committee, after a delay of more than 6 months because of the COVID-19 pandemic, should soon deliver its verdict, bringing joy to some and misery to others. “You need really big pockets” to build giant telescopes, Carlberg says. “The only people who can build them now are nations or consortia of nations.”

    See the full article here .


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  • richardmitnick 7:54 pm on August 31, 2021 Permalink | Reply
    Tags: "Tiny diamond mirrors could smooth out already revolutionary x-ray lasers", , , , Science Magazine, , ,   

    From Science Magazine: “Tiny diamond mirrors could smooth out already revolutionary x-ray lasers” 

    From Science Magazine

    27 Aug 2021
    Adrian Cho

    Ambitious recycling scheme would make giant accelerator-driven machines work more like ordinary lasers.

    Twelve years ago, physicists turned on the first x-ray laser, and since then it and several others around the world have proved themselves revolutionary probes of materials and molecules. But the devices, called x-ray free-electron lasers (XFELs), are only partially laserlike. In contrast to the pure, single-wavelength light emitted by conventional lasers, they produce noisy, chaotic beams. Now, physicists are developing a scheme that would enlist perfect diamond mirrors to make the x-ray pulses much more like ordinary laser beams and even more useful.

    With two facilities now racing to stage proof-of-principle experiments as early as 2023, would-be users are taking notice. “I’m excited about the potential of this,” says Serena DeBeer, a chemist at the MGP Institute for Chemical Energy Conversion [MPG Institut für chemische Energieumwandlung (DE), who says the beams could be used to study the inner workings of enzymes as they catalyze reactions. But realizing such sophisticated XFELs may take 10 years and won’t be easy, warns Harald Sinn, an x-ray physicist at the European XFEL: “There are nightmares ahead.”

    A conventional laser consists of a light-emitting material sitting between two mirrors. The carefully spaced mirrors form a cavity that resonates with light of the desired wavelength, just as an organ pipe rings with sound of a specific pitch. As the light passes back and forth through the material, it stimulates the stuff to produce more photons of the same wavelength, amplifying the light until a wave of identical photons marching in quantum mechanical lockstep—a laser beam—shines through one mirror, which is purposefully made imperfectly reflective.

    This scheme won’t work for x-rays. Physicists lack both an obvious radiating material and, until recently, mirrors that will reflect x-rays at large enough angles to form a resonating cavity. So they use a particle accelerator to fire a bunch of electrons down a vacuum pipe and through long trains of magnets called undulators, which shake the electrons side to side so they radiate x-ray photons. The light then travels along with the electrons and pushes them into microbunches, which wiggle in unison and radiate far more strongly, producing a burst of x-rays just femtoseconds long.

    The first free-electrion laser flicked on in the 1970s, producing much longer wavelength microwaves. It was not until 2009 that physicists at DOE’s SLAC National Accelerator Laboratory (US) achieved the feat for “hard” x-rays, when they used the lab’s 3-kilometer-long linear accelerator to fire up the world’s first XFEL, the Linac Coherent Light Source (LCLS).

    Other countries have since built a half-dozen XFELS.

    As with ordinary laser beams, x-rays from an XFEL arrive in smooth fronts, like ocean waves across a beach. A single XFEL pulse can scatter off a nanometer-size crystal and reveal its atomic structure, even as it blows the crystal to bits. Biologists have used XFELs to determine the structures of myriad proteins and other molecules that won’t form crystals big enough to be studied at less intense x-ray sources. But because an XFEL uses fluctuations in the density of the electron beam to begin to generate x-rays, one pulse varies from another in intensity, and each pulse has a wide and randomly distributed spectrum of wavelengths.

    To squelch such noise, physicists have turned to an idea kicked around for decades, says Kwang-Je Kim, an accelerator physicist at DOE’s Argonne National Laboratory (US). “People talked about it from time to time over drinks, but it was party conversation,” he says. “Nobody did any serious calculations” until the late 2000s, when Kim and others tackled the issue.

    A gem of an idea to smooth out x-rays

    In an x-ray free-electron laser (XFEL), an undulator magnet shakes a bunch of energetic electrons sideways so they emit x-rays. The x-rays push the electrons into subbunches that, radiating in concert, then generate a noisy tsunami of x-rays. A twist on the concept could produce more consistent, smoother x-ray pulses.

    The idea is to extract part of the x-ray pulse generated by one bunch of electrons and feed it back to the entrance of the undulators just in time to overlap with the next bunch of electrons. The recirculated x-rays would serve as a seed that causes the electrons to radiate more predictably. In repeated cycles, the x-ray pulses should become very pure and smooth, with a spread of wavelengths only 1/1000th as wide as ordinary XFEL pulses.

    The plan requires very special mirrors, however. X-rays blast through most material, but for 100 years, physicists have known that a perfect crystal should reflect x-rays at certain angles, depending on the x-rays’ energy and the crystal’s structure and orientation, as the x-rays diffract off parallel planes of atoms in the crystal. The crystal also acts as a filter, as it reflects x-rays in a narrow range of wavelengths. Such crystal mirrors remained an aspiration until 2010, when Yuri Shvyd’ko, an x-ray physicist at Argonne, and colleagues showed small synthetic diamonds can reflect x-rays with 99% efficiency. Fortunately, an XFEL’s beam is less than 100 micrometers wide. “You don’t need a large crystal,” Shvyd’ko says. “You need a perfect crystal of small size.”

    The scheme also requires a linear accelerator with a high repetition rate, to ensure the x-ray beam encounters a fresh bunch of electrons each time it rounds its circuit of mirrors. SLAC’s original accelerator is way too slow, firing 120 times a second. The European XFEL runs at 2.2 million cycles a second, so a cavity just 136 meters long would synchronize the x-rays with the electron bunches. SLAC is installing an accelerator that will run at 1 million cycles per second starting in 2022.

    To test the essential elements for a cavity-based XFEL, physicists from Argonne, SLAC, and the Japanese lab Spring-8 plan to use four crystal mirrors to build a 66-meter-long cavity around seven LCLS undulators. By fiddling with SLAC’s current accelerator, they will shoot two bunches of electrons separated by 220 nanoseconds through the undulators and hope to show that recirculating x-rays from the first bunch make the second bunch radiate more efficiently. The system should be up and running in 2023, says Gabriel Marcus, an accelerator physicist at SLAC. Researchers at the European XFEL plan to implement a slightly different design by 2024. They hope to send up to 2700 electron bunches through the undulators and watch the laser beam grow stronger and smoother with each pass.

    Patrick Rauer, an x-ray physicist at The University of Hamburg [Universität Hamburg](DE) who has modeled the European XFEL project on a computer, cautions that the scheme will require extraordinary precision, with the millimeter-size diamonds aligned to a few millionths of a degree. “It’s a major problem,” Rauer says. “This is going to very difficult.” Ilya Agapov, an accelerator physicist at the DESY Electron Synchrotron[ Deütsches Elektronen-Synchrotron](DE), says that even harder will be maintaining the alignment as circulating x-rays heat the mirrors.

    Still, potential users foresee major benefits. For example, Christian Gutt of The University of Siegen [Universität Siegen](DE) has used the European XFEL to study how proteins in solution diffuse and cluster on time scales as short as nanoseconds by studying correlations in the patterns of x-rays diffracted by the proteins. Those patterns would be far sharper with a cavity-based XFEL, he says. “That would be a game changer for us.”

    With its extremely narrow spectrum, a cavity-based XFEL might even serve to control the quantum states of atomic nuclei much as atomic physicists now control the states of atoms with visible light, says Linda Young, an atomic physicist at Argonne. “It’s very wild,” she says. All it will take is a few mirrors—and a lot of hard work.

    See the full article here .


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  • richardmitnick 9:02 pm on August 17, 2021 Permalink | Reply
    Tags: "With explosive new result laser-powered fusion effort nears ‘ignition’", , , Science Magazine   

    From Science Magazine: “With explosive new result laser-powered fusion effort nears ‘ignition’” 

    From Science Magazine

    Aug. 17, 2021
    Daniel Clery

    1
    An artist’s rendering shows how the National Ignition Facility’s 192 beams enter an eraser-size cylinder of gold and heat it from the inside to produce x-rays, which then implode the fuel capsule at its center to create fusion. Credit: DOE’s Lawrence Livermore National Laboratory.

    More than a decade ago, the world’s most energetic laser started to unleash its blasts on tiny capsules of hydrogen isotopes, with managers promising it would soon demonstrate a route to limitless fusion energy. Now, the National Ignition Facility (NIF) has taken a major leap toward that goal. Last week, a single laser shot sparked a fusion explosion from a peppercorn-size fuel capsule that produced eight times more energy than the facility had ever achieved: 1.35 megajoules (MJ)—roughly the kinetic energy of a car traveling at 160 kilometers per hour. That was also 70% of the energy of the laser pulse that triggered it, making it tantalizingly close to “ignition”: a fusion shot producing an excess of energy.

    “After many years at 3% of ignition, this is superexciting,” says Mark Herrmann, head of the fusion program at Lawrence Livermore National Laboratory, which operates NIF.

    NIF’s latest shot “proves that a small amount of energy, imploding a small amount of mass, can get fusion. It’s a wonderful result for the field,” says physicist Michael Campbell, director of the Laboratory for Laser Energetics (LLE) at the University of Rochester (US).

    “It’s a remarkable achievement,” adds plasma physicist Steven Rose, co-director of the Centre for Inertial Fusion Studies at Imperial College London (UK). “It’s made me feel very cheerful. … It feels like a breakthrough.”

    And it is none too soon, as years of slow progress have raised questions about whether laser-powered fusion has a practical future. Now, according to LLE Chief Scientist Riccardo Betti, researchers need to ask: “What is the maximum fusion yield you can get out of NIF? That’s the real question.”

    Fusion, which powers stars, forces small atomic nuclei to meld together into larger ones, releasing large amounts of energy. Extremely hard to achieve on Earth because of the heat and pressure required to join nuclei, fusion continues to attract scientific and commercial interest because it promises copious energy, with little environmental impact.

    Yet among the many approaches being investigated, none has yet generated more energy than was needed to cause the reaction in the first place. Large doughnut-shaped reactors called tokamaks, which use magnetic fields to cage a superhot plasma for long enough to heat nuclei to fusion temperatures, have long been the front-runners to achieve a net energy gain.

    But the giant $25 billion ITER project in France is not expected to get there for more than another decade, although private fusion companies are promising faster progress.

    NIF’s approach, known as inertial confinement fusion, uses a giant laser housed in a facility the size of several U.S. football fields to produce 192 beams that are focused on a target in a brief, powerful pulse—1.9 MJ over about 20 nanoseconds. The aim is to get as much of that energy as possible into the target capsule, a diminutive sphere filled with the hydrogen isotopes deuterium and tritium mounted inside a cylinder of gold the size of a pencil eraser. The gold vaporizes, producing a pulse of x-rays that implodes the capsule, driving the fusion fuel into a tiny ball hot and dense enough to ignite fusion. In theory, if such tiny fusion blasts could be triggered at a rate of about 10 per second, a power plant could harvest energy from the high-speed neutrons produced to generate electricity.

    When NIF launched, computer models predicted quick success, but fusion shots in the early years only generated about 1 kilojoule (kJ) each. A long effort to better understand the physics of implosions followed and by last year shots were producing 100 kJ. Key improvements included smoothing out microscopic bumps and pits on the fuel capsule surface, reducing the size of the hole in the capsule used to inject fuel, shrinking the holes in the gold cylinder so less energy escapes, and extending the laser pulse to keep driving the fuel inward for longer. The progress was sorely needed, as NIF’s funder, the National Nuclear Security Administration, was reducing shots devoted to ignition in favor of using its lasers for other experiments simulating the workings of nuclear weapons.

    Earlier this year, combining those improvements in various ways, the NIF team produced several shots exceeding 100 kJ, including one of 170 kJ. That result suggested NIF was finally creating a “burning plasma,” in which the fusion reactions themselves provide the heat for more fusion—a runaway reaction that is key to getting higher yields. Then, on 8 August, a shot generated the remarkable 1.35 MJ. “It was a surprise to everyone,” Herrmann says. “This is a whole new regime.”

    Exactly which improvements had the greatest impact and what combination will lead to future gains will take a while to unravel, Herrmann says, because several were tweaked at once in the latest shot. “It’s a very nonlinear process. That’s why it’s called ignition: It’s a runaway thing,” he says. But, “This gives us a lot more encouragement that we can go significantly farther.”

    Herrmann’s team is a long way from thinking about fusion power plants, however. “Getting fusion in a laboratory is really hard, getting economic fusion power is even harder,” Campbell says. “So, we all have to be patient.” NIF’s main task remains ensuring the United States’s nuclear weapons stockpile is safe and reliable; fusion energy is something of a sideline. But reaching ignition and being able to study and simulate the process will also “open a new window on stewardship,” Herrmann says, because uncontrolled fusion powers nuclear weapons.

    Herrmann admits that, when he got a text last week from colleagues saying they’d gotten an “interesting” result from the latest shot, he was worried something might be wrong with the instruments. When that proved not to be the case, “I did open a bottle of champagne.”

    See the full article here .


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  • richardmitnick 4:12 pm on July 25, 2021 Permalink | Reply
    Tags: "This is the first mini particle accelerator to power a laser", , , , Physicists in China used a small “plasma wakefield accelerator” to power a type of laser called a free-electron laser (FEL)., Science Magazine, Shanghai Institute of Optics and Fine Mechanics-[http://english.siom.cas.cn/] (SIOM) (CN), ,   

    From Shanghai Institute of Optics and Fine Mechanics via Science Magazine: “This is the first mini particle accelerator to power a laser” 

    1

    From Shanghai Institute of Optics and Fine Mechanics

    via

    Science Magazine

    Jul. 25, 2021
    Adrian Cho

    1

    From the laser and gas target (left) to the undulators (blue) and electromagnetic spectrometer (right), the novel free-electron laser measures just 12 meters in length. Credit: Shanghai Institute of Optics and Fine Mechanics (CN).

    For 2 decades, physicists have strived to miniaturize particle accelerators—the huge machines that serve as atom smashers and x-ray sources. That effort just took a big step, as physicists in China used a small “plasma wakefield accelerator” to power a type of laser called a free-electron laser (FEL). The 12-meter-long FEL isn’t nearly as good as its kilometers-long predecessors. Still, other researchers say the experiment marks a major advance in mini accelerators.

    “A lot of [scientists] will be looking at this like, ‘Yeah, that’s very impressive!’” says Jeroen van Tilborg, a laser-plasma physicist at the DOE’s Lawrence Berkeley National Laboratory (US) who was not involved in the work. Ke Feng, a physicist at the Shanghai Institute of Optics and Fine Mechanics (SIOM) who worked on the new FEL, isn’t claiming it’s ready for applications. “Making such devices useful and miniature is always our goal,” Feng says, “but there is still a lot of work to do.”

    Particle accelerators are workhorses in myriad fields of science, blasting out fundamental particles and generating intense beams of x-rays for studies of biomolecules and materials. Such accelerators stretch kilometers in length and cost $1 billion or more. That’s because within a conventional accelerator, charged particles such as electrons can gain energy only so quickly. Grouped in compact bunches, the particles zip through a vacuum pipe and pass through cavities that resonate with microwaves. Much as an ocean wave propels a surfer, these microwaves push the electrons and increase their energy. However, if the oscillating electric field in the microwaves grows too strong, it will set off damaging sparks. So, the particles can gain a maximum of about 100 megaelectron volts (MeV) of energy per meter of cavity.

    To accelerate particles in shorter distances, physicists need stronger electric fields. Firing a pulse of laser light into a gas such as helium is one way to generate them. The light rips electrons from the atoms, creating a tsunami of ionization that moves through the gas, followed by a wake of rippling electrons that produces an extremely strong electric field. That wakefield can scoop up electrons and accelerate them to 1000 MeV in just a few centimeters.

    Physicists hoping to harness wakefields have shown they can generate very short, intense bursts of electrons. But within a burst, the energies of those electrons typically vary by a few percent, too much for most practical applications. Now, SIOM physicist Wentao Wang, Feng, and colleagues have improved the output of their plasma wakefield accelerator enough to do something potentially useful with it: power an FEL.

    In an FEL, physicists fire electrons down a vacuum pipe and through a line devices called undulators. Within an undulator, small magnets above and below the beam pipe lined up like teeth, with the north poles of neighboring magnets alternating up and down. As electrons pass through the undulators, the rippled magnetic field shakes them back and forth, causing them to emit light. As the light builds up and travels along with the bunch of electrons, it pushes back on the electrons and separates them into sub-bunches that then radiate in concert to amplify the light into a laser beam.

    The world’s first x-ray laser, at SLAC National Accelerator Laboratory, is an FEL powered by the lab’s famous 3-kilometer long linear accelerator.

    Researchers in Europe and Japan have also built large x-ray FELs. But by shooting the electron beam from their plasma wakefield accelerator through a chain of three 1.5-meter-long undulators, the SIOM team has made an FEL small enough to fit into a long room.

    To make that possible, SIOM physicists had to shrink the spread in the electrons’ energy to 0.5%. They succeeded by optimizing the laser and the gas target to better control the electrons’ acceleration send them more smoothly down the vacuum pipe, Wang says. Teams in the United States and Europe have explored more complex schemes for filtering out electrons of a specific energy, but the SIOM team took a simpler approach, van Tilborg says. “Everything is just a little better optimized,” he says.

    Others had used plasma wakefield accelerators to coax light out of undulators before. But Wang and colleagues demonstrated amplification, showing the light’s intensity increases 100-fold in the third undulator, they report this week in Nature. “This a huge step forward,” says Agostino Marinelli, an accelerator physicist at DOE’s SLAC National Accelerator Laboratory (US).

    The tiny FEL is a far cry from its bigger brethren, which generate beams billions of times brighter than other x-ray sources, with an energy spread as low as 0.1%. The new FEL produces much fainter pulses of longer wavelength ultraviolet light with an energy spread of 2%. SLAC researchers are also upgrading the LCLS to produce millions of pulses per second; the novel FEL can produce 5 per second.

    Reaching x-ray wavelengths with the device will be difficult, Marinelli predicts. “These are very impressive results, but I would be very careful of extrapolating this to x-ray energies,” Still, the SIOM team says that’s their goal. “It is hard to say how long it will take to reach the hard x-ray wavelengths, maybe a decade or longer,” says Ruxin Li, an SIOM physicist and team member. “We look forward to that day.”

    See the full article here.

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  • richardmitnick 8:30 am on July 21, 2021 Permalink | Reply
    Tags: "Stellar explosion could be a failed supernova giving birth to a black hole", , , , , , Science Magazine,   

    From Science Magazine: “Stellar explosion could be a failed supernova giving birth to a black hole” 

    From Science Magazine

    Jul. 20, 2021
    Jonathan O’Callaghan

    1
    The strange “Cow” explosion, the right hand of two bright spots below and to the right of the galactic center, may be an odd variety of supernova.
    R. MARGUTTI/W. M. Keck Observatory, MaunaKea, Hawai’i (US)/Wikimedia Commons (CC-BY)

    When a massive star reaches the end of its life, it can explode as a supernova, leaving behind a dense remnant in the form of a neutron star or black hole. We typically can’t see these objects because supernovae tend to occur in distant galaxies, making their remnants hard to spot. But astronomers now say they’ve seen one inside a rare failed stellar explosion.

    The result hasn’t yet been peer reviewed. If the finding is correct, it would be “one of the very first times we’ve seen direct evidence for a star collapsing and forming one of these compact objects,” says Anna Ho, an astrophysicist at the University of California-Berkeley (US), who was not involved in the work.

    In 2018, astronomers spotted a new type of stellar explosion inside a comparatively close galaxy, 200 million light-years away. Dubbed AT2018cow, but informally known as “the Cow,” the event was both much brighter and faster—reaching its peak brightness in just days before dimming 3 weeks later—than a regular supernova, defying explanation. Scientists’ best guess for the cause of the bright blip, known as a fast blue optical transient (FBOT), was that the interior of a star collapsed to become a neutron star or black hole before a true supernova could form. The result was a “central engine”—a rapidly spinning object inside the outer layers of the star. Scientists think powerful jets of matter coming from the neutron star or black hole burst through the outer shells of material, making the object appear extremely bright.

    Now, in a preprint on the server Research Square, scientists report spotting such an object inside the Cow. Using a telescope on the International Space Station called the Neutron Star Interior Composition Explorer [NICER], the scientists observed x-ray light emitted by the Cow for 60 days following the explosion.

    After precisely timing the arrival of the photons, they calculated that the object producing the light was spinning once every 4.4 milliseconds.

    “This rapid periodicity is hinting that the x-ray source is compact and small,” says Brian Metzger, an astrophysicist at Columbia University (US) and a co-author on the study. Because the rotation stayed constant at 4.4 milliseconds, even after billions of observed spins, a black hole explanation is more likely than a neutron star, he adds, because a neutron star’s rotation speed would be expected to decrease over time.

    Daniel Perley, an astrophysicist at Liverpool John Moores University (UK), calls the finding “very exciting.” If correct, it would rule out other possible explanations for the Cow, including the idea that its light comes from a larger, intermediate-mass black hole devouring a star. “Whatever is producing these x-rays must be extremely compact, on the scale of kilometers, which essentially rules out a large black hole and points strongly in favor of the central engine models,” he says.

    Three events similar to the Cow have been spotted since 2018, most recently “the Camel” in 2020, but none is as close or bright as the Cow, making comparison difficult. Metzger calls the Cow a “Rosetta Stone event” that could be useful in interpreting more of these failed supernovae. “It’s a nearby event that we can hope to understand,” he says. “And if this is telling us this is a black hole, then every time we see an FBOT in the distant universe, we will know that was a black hole that formed.”

    See the full article here .


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  • richardmitnick 9:03 pm on July 15, 2021 Permalink | Reply
    Tags: "Exploding stars may have assaulted ancient Earth", 1999 The era of supernova geochemistry had begun [see PRL article link included]., ASM: accelerator mass spectrometer at TUM, , , , , Iron-60 forged in the cores of large stars-which has a half-life of 2.6 million years and is not made naturally on Earth., Kilonovae, , Science Magazine, ,   

    From Science Magazine: “Exploding stars may have assaulted ancient Earth” 

    From Science Magazine

    Jul. 15, 2021
    Daniel Clery

    1

    The Crab nebula is the remains of a supernova more than 6000 light-years away—too far to harm Earth.
    National Aeronautics Space Agency (US); European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU); J. Hester and A. Loll/Arizona State University (US).

    For our Australopithecus ancestors who roamed Africa 2.5 million years ago, the bright new star in the sky surely would have aroused curiosity. As luminous as the full Moon, it would have cast shadows at night and been visible during the day. As the supernova faded over the following months, it probably also faded from memory. But it left other traces, now coming to light.

    Over the past 2 decades, researchers have found hundreds of radioactive atoms, trapped in seafloor minerals, that came from an ancient explosion marking the death of a nearby star. Its fusion fuel exhausted, the star had collapsed, generating a shock wave that blasted away its outer layers in an expanding ball of gas and dust so hot that it briefly glowed as bright as a galaxy—and ultimately showered Earth with those telltale atoms.

    Erupting from hundreds of light-years away, the flash of x-rays and gamma rays probably did no harm on Earth.

    But the expanding fireball also accelerated cosmic rays—mostly nuclei of hydrogen and helium—to close to the speed of light. These projectiles arrived stealthily, decades later, ramping up into an invisible fusillade that could have lasted for thousands of years and might have affected the atmosphere—and life.

    In a flurry of studies and speculation, astronomers have sketched out their potential effects. A cosmic ray barrage might have boosted mutation rates by eroding Earth’s protective ozone layer and generating showers of secondary, tissue-penetrating particles. Tearing through the atmosphere, the particles would have also created pathways for lightning, perhaps kindling a spate of wildfires. At the same time, atmospheric reactions triggered by the radiation could have led to a rain of nitrogen compounds, which would have fertilized plants, drawing down carbon dioxide. In that way, the celestial event could have cooled the climate and helped initiate the ice ages 2.5 million years ago, at the start of the Pleistocene epoch. Even taken together, the effects are “not like the dinosaur extinction event—it’s more subtle and local,” says Brian Thomas, an astronomer at Washburn University (US) who has studied the earthly effects of cosmic catastrophes for nearly 2 decades.

    Few astronomers are suggesting that the supernovae caused any great extinction at the time, and even fewer paleontologists are ready to believe them. “Death from space is always really cool,” says Pincelli Hull, a paleontologist at Yale University (US). “The evidence is interesting but has not quite really reached the threshold to incorporate into my mental register.”

    Yet the supernova hunters believe other blasts, more distant in time, went off closer to Earth. And they think these supernovae could explain some extinction events that lack customary triggers such as volcanic outbursts or asteroid impacts. Adrian Melott, an astronomer at the University of Kansas-Lawrence (US), who explores how nearby cosmic cataclysms might affect Earth, says it’s time to more carefully probe Earth’s history for ancient supernova strikes. Not only will that help astrophysicists understand how the blasts shaped the neighborhood of the Solar System and seeded it with heavy elements, but it could also give paleontologists a new way to think about bouts of global change. “This is new and unfamiliar,” Melott says. “It will take time to be accepted.”

    Astronomers believe a few supernovae go off in the Milky Way every century. By the law of averages, a handful must have exploded very close to Earth—within 30 light-years—during its 4.5-billion-year lifetime, with potentially catastrophic effects. Even blasts as far as 300 light-years away should leave traces in the form of specks of dust blown out in the shell of debris known as a supernova remnant. When physicist Luis Alvarez set out in the 1970s with his geologist son Walter Alvarez to study the sediment layers associated with the dinosaurs’ extinction 65 million years ago, they were expecting to find supernova dust. Instead, they found iridium, an element that is rare on Earth’s surface but abundant in asteroids.

    The Alvarezes didn’t have the tools to look for supernova dust, in any case. Because Earth is already largely made of elements forged in supernovae billions of years ago, before the Sun’s birth, most traces of more recent explosions are undetectable. Not all of them, however. In the 1990s, astrophysicists realized supernova dust might also deposit radioactive isotopes with half-lives of millions of years, far too short to have been around since Earth’s birth. Any that are found must come from geologically recent sprinklings. One key tracer is iron-60 forged in the cores of large stars-which has a half-life of 2.6 million years and is not made naturally on Earth.

    In the late 1990s, Gunther Korschinek, an astroparticle physicist at the Technical University of Munich [Technische Universität München] (DE), decided to look for it, partly because the university had a powerful accelerator mass spectrometer (ASM) suited to the task. After ionizing a sample, an ASM boosts the charged particles to high energies and shoots them through a magnetic field. The field bends their path onto a string of detectors; the heaviest atoms are deflected least because of their greater momentum.

    Separating atoms of iron-60 from the similarly hefty but differently charged nickel-60 is especially challenging, but TUM’s ASM, built in 1970, is one of the few in the world powerful enough to tease them apart.

    Korschinek also needed the right sample: a geologic deposit laid down over millions of years in which an iron signal might stand out. Antarctic ice cores wouldn’t work: they only go back a couple of million years or so. Most ocean sediments accumulate so fast that any iron-60 is diluted to undetectable levels. Korschinek ended up using a ferromanganese crust dredged from a North Pacific seamount by the German research ship Valdivia in 1976. These crusts grow on patches of seabed where sediments can’t settle because of a slope or currents. When the pH of the water is just right, metal atoms selectively precipitate out of the water, slowly building up a mineral crust at the rate of a few millimeters every million years.

    Korschinek and his team sliced their sample up into layers of different ages, chemically separated out the iron, and fired the atoms through their mass spectrometer. They found 23 atoms of iron-60 among the thousands of trillions of atoms of normal iron, with the highest abundance from a time less than 3 million years ago, the team reported in Physical Review Letters in 1999. The era of supernova geochemistry had begun. “We were the first ones to start experimental studies,” Korschinek says.

    Others followed. Iron-60 was found in ocean crusts from other parts of the world and even in ocean sediment microfossils, remains of living things that, helpfully for the supernovae hunters, had taken up and concentrated iron in their bodies. Most results pointed to a local supernova between 2 million and 3 million years ago—with hints of a second one a few million years earlier.

    Although the remnants from these blasts have long since swept past Earth, a drizzle of the atoms they blew out continues. In 2019, Korschinek’s team ran iron from a half-ton of fresh Antarctic snow through its ASM and found a handful of iron-60 atoms, which he estimates fell to Earth in the past 20 years. Another team found a smattering of the atoms in cosmic rays detected by NASA’s Advanced Composition Explorer at a position partway between the Sun and Earth.

    Researchers have even found iron-60 in lunar soil brought back by the Apollo missions. “The Moon confirmed that it was not just some Earth-based phenomenon,” says astronomer Adrienne Ertel of the University of Illinois, Urbana-Champaign (US).

    2
    To detect trace ions, an Australian accelerator fired samples through a magnet.
    Tim Wetherell/Research School of Physics/Australian National University (AU).

    Dieter Breitschwerdt is trying to trace the iron to its source in the sky. When the astronomer at the Technical University of Berlin [Technische Universität Berlin](DE) learned of Korschinek’s results, he was studying the local bubble, a region of space around the Solar System swept clear of most of its gas and dust. Supernovae were the likely brooms, and so he began to track gangs of stars in the Solar System’s neighborhood to see whether any passed close enough to the Sun to deposit iron-60 on Earth when some of their members exploded.

    Using data from Hipparcos, a European star-mapping satellite, Breitschwerdt looked for clumps of stars on common trajectories and rewound the clock to see where they would have been millions of years ago.

    Two clumps, now a part of the Scorpius-Centaurus OB Association (Sco OB2), seemed to be in the perfect spot—300 light-years from Earth—about 2.5 million years ago. “It looked like a miracle,” he says. The odds of a detonation at the right time were good. Core-collapse supernovae take place in massive stars. Based on the ages and masses of the 79 stars remaining in the clumps, Breitschwerdt estimates that a dozen former members exploded as supernovae in the past 13 million years.

    Visible evidence for these supernovae in Sco OB2 is long gone: Supernova remnants dissipate after about 30,000 years, and the black holes or neutron stars they leave behind are challenging to spot. But the arrival direction of the iron dust could, in theory, point back to its source. Samples from the sea floor provide no directional information because wind and ocean currents move the dust as it settles. On the Moon, however, “there is no atmosphere, so where it hits is where it stops,” says UIUC astronomer Brian Fields. Because it spins, the Moon cannot provide longitudinal direction, but if more iron-60 was detected at one of the poles than at the equator, for example, that could support Breitschwerdt’s Sco OB2 as the source. Fields and several colleagues want to test that idea and have applied to NASA for samples of lunar soil, to be collected and returned by any future robotic or human missions.

    Korschinek’s team now has a rival in the hunt for supernova iron: a group led by Anton Wallner, a former postdoc of Korschinek’s, who has used an upgraded ASM at Australian National University (AU) to analyze several ferromanganese crusts dredged off the Pacific Ocean floor by a Japanese mining company. “Now we pushed Munich,” Wallner says.

    This year, in Science Advances[sorry, no link] Wallner’s team probed the timing of the recent supernovae more precisely than ever by slicing a crust sample into 24 1-millimeter-thick layers, each representing 400,000 years. “It’s never been done before with this time resolution,” says Wallner, now at the Helmholtz Center Dresden-Rossendorf [Helmholtz-Zentrum Dresden-Rossendorf](DE). The 435 iron-60 atoms they extracted pinned the most recent supernova at 2.5 million years ago and confirmed the hints of an earlier one, which they pegged at 6.3 million years ago. Comparing the abundance of iron-60 in the crust with models of how much a supernova produces, the team estimated the distance of these supernovae as between 160 and 320 light-years from Earth.

    Wallner’s team also found 181 atoms of plutonium-244, another radioactive isotope, but one that may have been forged in the supernova blast itself rather than in the precursor star, like iron-60. But its source is hotly debated: Some researchers think plutonium-244 is tough for supernovae to make in any great amounts. Instead, they see it as the product of collisions between neutron stars—cinders left behind by supernovae [Science].

    These collisions, called kilonovae, are 100 times rarer than supernovae, but are much more efficient at making the heaviest elements. “Neutron star mergers have an easy time making plutonium,” says Rebecca Surman, an astrophysicist at the University of Notre Dame. “For supernovae it’s much harder.”

    Surman still sees a role for supernovae. She takes the reported seafloor plutonium-244 as a sign that a kilonova, deep in the past, dusted our interstellar neighborhood with heavy elements. When the two recent supernovae went off, their expanding remnants may have swept up and delivered some of that interstellar plutonium-244 along with their own iron-60, she speculates. Korschinek, however, says it will take more data on the plutonium signal and its timing to convince him that multiple rare events happened so near and so recently.

    Beyond dusting Earth with rare nuclei, what impact might nearby supernovae have had? In 2016, a team led by Melott and Thomas estimated the flux of various forms of light and cosmic rays likely to reach Earth from an explosion 300 light-years away. Writing in The Astrophysical Journal Letters, they concluded that the most energetic, potentially damaging photons—x-rays or gamma rays—would have minimal impact. “There is not a lot of high energy radiation,” Thomas says. They suggested a few weeks of the bright light would have little more impact than disrupting sleep patterns.

    Cosmic rays—the particles accelerated to near light speed by shock waves in the supernova’s expanding fireball—are another story. Because they are charged, they can be deflected away from Earth by galactic magnetic fields. But the local bubble is thought to be mostly devoid of fields, so cosmic rays from just 300 light-years away would have a relatively clean shot.

    The atmosphere would have been subjected to a drawn-out barrage, Melott and Thomas found. “The ramp up is a slow process, decades at least,” Thomas says, reaching a peak about 500 years after the supernova flash and causing a 10-fold increase in ionization of atmospheric gas that would persist for 5000 years. Using an atmospheric chemistry model developed by NASA, they estimated that chemical changes caused by the ionization would deplete ozone by about 7% or more in places and would boost the creation of fertilizing nitrogen oxide compounds by 30%. The resulting surge in plants might be enough to cool the climate and usher in the Pleistocene.

    The cosmic rays weren’t done yet. When high-energy particles hit the upper atmosphere, they create cascades of secondary particles. Most fizzle out in further collisions, but muons—heavy short-lived cousins of electrons—keep going. Creatures on Earth’s surface would receive triple the normal radiation dose—equivalent to one or two CT scans per year. “An enhanced risk [of cancer], but not radiation poisoning,” Thomas says. Overall, the team thought the effects were “not catastrophic” but could be detectable in the fossil record if, for example, certain vulnerable species disappeared while others survived.

    In Astrobiology in 2019, Melott and two colleagues found that if the supernova exploded just 150 light-years away, rather than 300, the muon radiation would have hit marine animals surprisingly hard. Water blocks most particles that rain down from the sky, but muons can penetrate up to 1 kilometer. Marine creatures, normally shielded from nearly all radiation, would experience the largest relative increase in dose and suffer the most. This chimes with an extinction of marine megafauna at the start of the Pleistocene epoch, only recently identified in the fossil record.

    Then, last year, supernova proponents suggested a similar scenario could explain a major extinction event 359 million years ago, at the end of the Devonian period. A team led by John Marshall of the University of Southampton (UK) had found that the spores of fernlike plants from the time suddenly became misshapen and dark, blaming the changes on ultraviolet radiation. The team didn’t invoke an astronomical cause. But writing in the PNAS, astronomers saw the possible signature of a nearby supernova. They suggested a blast maybe just 60 light-years away could have drenched Earth in ultraviolet by depleting the ozone layer. “It’s pretty speculative,” admits co-author John Ellis, a theorist at King’s College London (UK), as it is currently impossible to identify the radioactive fingerprints of a supernova that far back.

    In a 2020 paper in The Journal of Geology, Melott and Thomas took a bigger speculative leap. They noted that by ripping electrons from air molecules, secondary cosmic rays would have created pathways for lightning, making storms more likely, which would not only generate more nitrogen compounds but also spark wildfires. Intriguingly, a layer of soot has been found in the rock record in some parts of the world at the start of the Pleistocene. Melott and Thomas went on to suggest that those supernova-induced forest fires may have pushed early humans out of the trees and onto the savanna, leading to bipedalism, larger brain size, and everything that followed. “It’s fascinating to say that a supernova 2.5 million years ago means we are talking now via Skype,” Korschinek says.

    Such scenarios don’t sit well with paleontologists. “Timing is the trivial answer to everything,” Hull says. “There’s always something happening when things become extinct.” Besides, she says, the transition to the Pleistocene “doesn’t stand out as needing an explanation.” She says other events around that time could have had more impact on the global climate, such as the closing of the isthmus of Panama, which profoundly changed ocean circulation.

    To make their case, she says, astronomers need to pin down the timing of the ancient supernovae more precisely. They “need to measure more crusts.” But hunting for supernova traces is not getting any easier. In 2019 TUM closed its AMS, leaving only ANU with an accelerator powerful enough to separate iron-60.

    In contrast, rarer isotopes such as plutonium-244 could enable researchers to look further back in time, but they require an AMS that emphasizes sensitivity rather than raw power, and Wallner says only a few in the world are up to the job. He has secured funding to build a new AMS facility in Dresden, Germany, specializing in the heaviest elements, that should be open by 2023. To renew the hunt for iron-60, his team has also made a pitch for national funding to build a new high-energy AMS, which could be up and running in 7 years.

    For astronomers, a sudden flash of light in the sky today would be the best chance to see how supernova affects Earth. But the odds are slim that we will see a light show like the one that may have dazzled our distant ancestors. Betelgeuse, a restive red giant likely to blow up sometime in the next 100,000 years, has settled down in recent months, and in any case, it lies more than 500 light-years away. Sco OB2 is now heading away from the Sun. And using data from Hipparcos’s successor, Europe’s Gaia mission, Breitschwerdt has tracked another 10 clumps of stars.

    “None are coming closer,” he says. “The future”—for Earth, not the supernovae—“is bright.”

    See the full article here .


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  • richardmitnick 4:03 pm on July 14, 2021 Permalink | Reply
    Tags: "To catch deep-space neutrinos astronomers lay traps in Greenland’s ice", Because they are not charged the neutrinos travel to Earth as straight as an arrow., Neutrinos are notoriously reluctant to interact with matter which allows trillions to pass through you every second without any notice., Particle astrophysics, Placing hundreds of radio antennas on the ice surface and dozens of meters below it., RNO-G The Radio Neutrino Observatory in Greenland led by the University of Chicago (US) the Free University of Brussels [Vrije Universiteit Brussel](BE) and DESY Electron Synchrotron[ Deütsches Elekt, Science Magazine, They hope to trap elusive particles known as neutrinos at higher energies than ever before., , UHE's: ultra–high-energy cosmic rays   

    From Science Magazine: “To catch deep-space neutrinos astronomers lay traps in Greenland’s ice” 

    From Science Magazine

    Jul. 14, 2021
    Daniel Clery

    1
    Flags mark the locations of antennas designed to detect radio pulses from neutrino collisions in the ice.
    CHRISTOPH WELLING/RNO-G COLLABORATION/ DESY Electron Synchrotron[ Deütsches Elektronen-Synchrotron](DE)

    High on Greenland’s ice sheet, researchers are drilling boreholes this week. But they are not earth scientists seeking clues to the past climate. They are particle astrophysicists, searching for the cosmic accelerators responsible for the universe’s most energetic particles. By placing hundreds of radio antennas on the ice surface and dozens of meters below it, they hope to trap elusive particles known as neutrinos at higher energies than ever before. “It’s a discovery machine, looking for the first neutrinos at these energies,” says Cosmin Deaconu of the University of Chicago (US), speaking from Greenland’s Summit Station.

    Detectors elsewhere on Earth occasionally register the arrival of ultra–high-energy (UHE) cosmic rays, atomic nuclei that slam into the atmosphere at speeds so high that a single particle can pack as much energy as a well-hit tennis ball. Researchers want to pinpoint their sources, but because the nuclei are charged, magnetic fields in space bend their paths, obscuring their origins.

    That’s where neutrinos come in. Theorists believe that as UHE cosmic rays set out from their sources, they spawn so-called cosmogenic neutrinos as they collide with photons from the cosmic microwave background, which pervades the universe. Because they are not charged the neutrinos travel to Earth as straight as an arrow. The difficulty comes in catching them. Neutrinos are notoriously reluctant to interact with matter which allows trillions to pass through you every second without any notice. Huge volumes of material have to be monitored to capture just a handful of neutrinos colliding with atoms.

    The largest such detector is the IceCube Neutrino Observatory in Antarctica, which watches for flashes of light from neutrinoatom collisions across 1 cubic kilometer of ice beneath the South Pole.
    ______________________________________________________________________________________________________________
    U Wisconsin IceCube neutrino observatory

    ______________________________________________________________________________________________________________

    Since 2010, IceCube has detected many deep space neutrinos, but only a handful—with nicknames including Bert, Ernie, and Big Bird—that have energies approaching 10 petaelectronvolts (PeV), the expected energy of cosmogenic neutrinos, says Olga Botner, an IceCube team member at Uppsala University [ Uppsala universitet] (SE). “To detect several neutrinos with even higher energies within a reasonable time, we need to monitor vastly larger volumes of ice.”

    One way to do that is to take advantage of another signal generated by a neutrino impact: a pulse of radio waves. Because the waves travel up to 1 kilometer within ice, a widely spaced array of radio antennas near the surface can monitor a much larger volume of ice, at a lower cost, than IceCube, with its long strings of photon detectors deep in the ice. The Radio Neutrino Observatory Greenland (RNO-G), led by the University of Chicago, the Free University of Brussels, and the German accelerator center DESY, is the first concerted effort to test the concept.

    When complete in 2023, it will have 35 stations, each comprising two dozen antennas, covering a total area of 40 square kilometers. The team installed the first station last week near the U.S.-run Summit Station, at the apex of the Greenland Ice Sheet, and has moved on to its second. The environment is remote and unforgiving. “If you didn’t bring something you can’t get it shipped quickly,” Deaconu says. “You have to make do with what you have.”

    The cosmogenic neutrinos the team hopes to capture are thought to emanate from violent cosmic engines. The most likely power sources are supermassive black holes that gorge on material from their surrounding galaxies. IceCube has traced two deep space neutrinos with energies lower than Bert, Ernie, and Big Bird to galaxies with massive black holes—a sign they are on the right track. But many more neutrinos at higher energies are needed to confirm the link.

    In addition to pinpointing the sources of UHE cosmic rays, researchers hope the neutrinos will show what those particles are made of. Two major instruments that detect UHE cosmic rays differ over their composition. Data from the Telescope Array in Utah suggest they are exclusively protons, whereas the Pierre Auger Observatory in Argentina suggests heavier nuclei are mixed among the protons. The energy spectrum of the neutrinos spawned by those particles should differ depending on their composition—which in turn could offer clues to how and where they are accelerated.

    RNO-G just might catch enough neutrinos to reveal those telltale energy differences, says Anna Nelles of Friedrich Alexander University Erlangen-Nürnberg, one of the project leaders, who estimates that RNO-G might catch as many as three cosmogenic neutrinos per year. But, “If we’re unlucky,” she says, detections might be so scarce that scoring just one would take tens of thousands of years.

    Even if RNO-G proves to be a waiting game, it is also a testbed for a much larger radio array, spread over 500 square kilometers, planned as part of an IceCube upgrade. If cosmogenic neutrinos are out there, the second generation IceCube will find them and resolve the question of what they are. “It could be flooded with neutrinos, 10 per hour,” Nelles says. “But we have to be lucky.”

    RNO-G The Radio Neutrino Observatory in Greenland led by the University of Chicago (US) the Free University of Brussels [Vrije Universiteit Brussel](BE) and DESY Electron Synchrotron[ Deütsches Elektronen-Synchrotron](DE)

    See the full article here .


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  • richardmitnick 7:25 pm on May 11, 2021 Permalink | Reply
    Tags: "‘Something went wrong.’ Some astronomers feel left out of European road map", adioNet – Radio Astronomy in Europe (EU), APPEC-Astroparticle Physics European Consortium (EU), Astronet, Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020) (US), OPTICON-Optical Infrared Coordination Network for Astronomy, Science Magazine   

    From Science Magazine: “‘Something went wrong.’ Some astronomers feel left out of European road map” 

    From Science Magazine

    May. 11, 2021
    Daniel Clery

    1
    A 2008 Astronet road map called for the European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).. Some astronomers are upset by the group’s latest effort. Credit: ESO [Observatoire européen austral][Europäische Südsternwarte] (EU).

    For more than 1 year, Astronet, a group of more than 50 astronomers, has labored to draw up priorities for the next 2 decades of European astronomy. A partial draft plan, released in February, lists the field’s most pressing scientific questions, such as how primordial gases coalesced into the first stars and galaxies and whether the atmospheres of exoplanets betray signs of life. To answer them, the plan calls for new facilities including the Einstein Telescope, a gravitational wave detector to be built in a network of underground tunnels; antennas installed on the radio-quiet far side of the Moon; and a fleet of orbiting telescopes to probe exoplanet atmospheres.

    But some are unhappy with what the draft plan left out—particularly in radio and gamma ray astronomy, as well as the study of high-energy particles from space. “Something went wrong,” says Leonid Gurvits, a radio astronomer at the Delft University of Technology [Technische Universiteit Delft] (NL). “It’s not anyone’s intention, it just happened in this unfortunate way.” Astronet organizers say the drafts were not intended to be exhaustive and later revisions will reflect the roughly 200 comments received before a 1 May deadline.

    Astronet mirrors the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020) (US), which since the 1960s has provided funding agencies and legislators with infrastructure priorities—essentially a wish list of big telescopes and space missions. The current iteration in the United States, known as Astro2020, is expected to release its report in the coming months. It was put together by more than 150 committee and panel members with input from hundreds of submitted white papers as well as dozens of virtual meetings and town halls.

    In its first incarnation, Astronet aimed for something similarly comprehensive, producing a science vision in 2007 and the following year, a road map of facilities and missions. It endorsed efforts now under construction including the Extremely Large Telescope, the Square Kilometre Array, and several space missions.

    Astronet was set up under the auspices of the European Union in 2005 with a 4-year budget of €2.5 million. After updating its vision and road map in 2015, the European Union cut off funding. But the group continued with support of a few tens of thousands of euros per year from funding bodies in eight nations plus the ESO [Observatoire européen austral][Europäische Südsternwarte] (EU). The Astronet board, made up of funding agency representatives, decided this time to produce “something more precise, direct, and to the point,” says board chair Colin Vincent of the STFC [Science & Technology Facilities Council] (UK). The new report, he says, aimed to answer, “What are the science questions, where are we now, and what do we need to progress over the next 20 years?”

    Astronet formed panels of as many as 12 researchers in each of five fields, ranging from the origin and evolution of the universe to understanding the Solar System and conditions for life. It also formed a panel covering computing and another for outreach, education, and diversity. COVID-19 thwarted plans to gather input at town hall meetings. The panels did not solicit white papers but instead drafted reports from their own experience. Drafts reports from the five subject panels were posted on the Astronet website for comments; the computing and workforce reports are still being drafted. The plan was to “throw them out there and see what the community makes of them,” Vincent says. After the comment period closed, Astronet planned virtual town halls and revisions before final release before the end of the year.

    Not everyone was impressed by this approach. Although Astronet tried to get the word out to astronomers across Europe, some complained they only heard about the draft reports 1 month or less before the deadline for comments. “It came totally out of the blue. Most people didn’t know about it,” says radio astronomer Heino Falcke of Radboud University [Radboud Universiteit](NL). “Everyone’s screaming: ‘What’s going on?’” Gurvits says. RadioNet – Radio Astronomy in Europe (EU), a network representing radio astronomy, requested an extension to the comments deadline but was declined.

    Others have complained about what they see as glaring omissions in the draft reports. According to Andreas Haungs of the KIT Karlsruhe Institute of Technology [Karlsruher Institut für Technologie] (DE), who heads the APPEC-Astroparticle Physics European Consortium (EU), the drafts don’t sufficiently credit the work done by astronomers using high-energy gamma rays, neutrinos, or gravitational waves. “I don’t think it really worked,” he says. Falcke says the report contains “not a single word” on the Event Horizon Telescope, which in 2019 produced the first image of a black hole’s shadow. “This is almost an embarrassment,” he says.

    Gerry Gilmore of the University of Cambridge’s (UK) Institute of Astronomy, head of the OPTICON-Optical Infrared Coordination Network for Astronomy | OPTICON Project | H2020 | CORDIS | European Commission (EU) network of optical and infrared astronomers, counters that the Astronet reports are “discussion documents, the start of a conversation.” Vincent also defends the process. “The important thing was to get people to respond. That’s the point of the consultation,” he says, acknowledging that the drafts may have appeared parochial to some. He says the subject panels are revising their drafts, and in June, the EAS European Astronomical Society (EU) will hold an open meeting to discuss those revisions, with further iterations continuing over the summer.

    Astronet has a difficult task. Europe already has the European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), which launches many space telescopes, and the ESO, which manages a group of top optical telescopes in Chile. With independent budgets, funded directly by national governments, those agencies autonomously work out their own long-term strategies. Linda Tacconi of the MPG Institute for extraterrestrial Physics [Max-Planck-Institut für außerirdische Physik] (DE), who is leading Voyage 2050 – Cosmos (EU), ESA’s latest science planning process, says it has been slowed by COVID-19. “Therefore, Voyage 2050 could not be included in the Astronet report,” she says.

    That leaves Astronet to bring some order to the disconnected groups of astronomers who aren’t covered by those two agencies. Dealing with so many national funders isn’t easy either, Vincent says. “A prescriptive approach wouldn’t be as successful,” he says. “We need a common understanding on what is needed and [national agencies] can make a variety of responses on what to bring to the party.”

    See the full article here .


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    Please help promote STEM in your local schools.

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