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  • richardmitnick 1:38 pm on March 20, 2020 Permalink | Reply
    Tags: "Tiny double accelerator recycles energy", A miniature double particle accelerator that can recycle some of the laser energy fed into the system to boost the energy of the accelerated electrons a second time., Center for Free-Electron laser Science (CFEL), DESY,   

    From DESY via phys.org: “Tiny double accelerator recycles energy” 

    DESY
    From DESY

    via


    phys.org

    1
    Proof of concept for cascaded terahertz accelerator using long pulses. The mini-accelerator uses terahertz radiation that can be recycled for a second stage of acceleration. Credit: DESY, Science Communication Lab.

    A team of DESY scientists has built a miniature double particle accelerator that can recycle some of the laser energy fed into the system to boost the energy of the accelerated electrons a second time. The device uses narrowband terahertz radiation which lies between infrared and radio frequencies in the electromagnetic spectrum, and a single accelerating tube is just 1.5 centimetres long and 0.79 millimetres in diameter. Dongfang Zhang and his colleagues from the Center for Free-Electron laser Science (CFEL) at DESY present their experimental accelerator in the journal Physical Review X.

    The miniature size of the device is possible due to the short wavelength of terahertz radiation. “Terahertz-based accelerators have emerged as promising candidates for next-generation compact electron sources,” explains Franz Kärtner, Lead Scientist at DESY and head of the CFEL group that built the device. Scientists have successfully experimented with terahertz accelerators before, which could enable applications where large particle accelerators are just not feasible or necessary. “However, the technique is still in an early stage, and the performance of experimental terahertz accelerators has been limited by the relatively short section of interaction between the terahertz pulse and the electrons,” says Kärtner.

    For the new device, the team used a longer pulse comprising many cycles of terahertz waves. This multicycle pulse significantly extends the interaction section with the particles. “We feed the multicycle terahertz pulse into a waveguide that is lined with a dielectric material”, says Zhang. Within the waveguide, the pulse’s speed is reduced. A bunch of electrons is shot into the central part of the waveguide just in time to travel along with the pulse. “This scheme increases the interaction region between the terahertz pulse and the electron bunch to the centimetre range—compared to a few millimetres in earlier experiments,” reports Zhang.

    The device did not produce a large acceleration in the lab. However, the team could prove the concept by showing that the electrons gain energy in the waveguide. “It is a proof of concept. The electrons’ energy increased from 55 to about 56.5 kilo electron volts,” says Zhang. “A stronger acceleration can be achieved by using a stronger laser to generate the terahertz pulses.”

    The set-up is mainly designed for the non-relativistic regime, meaning the electrons have speeds that are not so close to the speed of light. Interestingly, this regime enables a recycling of the terahertz pulse for a second stage of acceleration. “Once the terahertz pulse leaves the waveguide and enters the vacuum, its speed is reset to the speed of light,” explains Zhang. “This means, the pulse overtakes the slower electron bunch in a couple of centimetres. We placed a second waveguide at just the right distance that the electrons enter it together with the terahertz pulse which is again slowed down by the waveguide. In this way, we generate a second interaction section, boosting the electrons’ energies further.”

    In the lab experiment, only a small fraction of the terahertz pulse could be recycled this way. But the experiment shows that recycling is possible in principle, and Zhang is confident that the recycled fraction can be substantially increased. Nicholas Mattlis, senior scientist and the team leader of the project in the CFEL group, emphasises: “Our cascading scheme will greatly lower the demand on the required laser system for electron acceleration in the non-relativistic regime, opening new possibilities for the design of terahertz-based accelerators.”

    See the full article here .


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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 2:13 pm on November 21, 2019 Permalink | Reply
    Tags: , , , , , DESY, H.E.S.S. Čerenkov Telescope Array located on the Cranz family farm Göllschau in Namibia near the Gamsberg, MAGIC Čerenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia La Palma Spain))   

    From DESY: “Gamma-Ray Bursts with record energy” 

    DESY
    From DESY

    2019/11/20

    First detection of the cosmic monster explosions with ground-based gamma-ray telescopes.

    The strongest explosions in the universe produce even more energetic radiation than previously known: Using specialised telescopes, two international teams have registered the highest energy gamma rays ever measured from so-called gamma-ray bursts, reaching about 100 billion times as much energy as visible light. The scientists of the H.E.S.S. and MAGIC telescopes present their observations in independent publications in the journal Nature.

    A very-high-energy component deep in the γ-ray burst afterglow; The H.E.S.S. collaboration Nature

    Teraelectronvolt emission from the γ-ray burst GRB 190114C; The MAGIC collaboration Nature

    These are the first detections of gamma-ray bursts with ground-based gamma-ray telescopes. DESY plays a major role in both observatories, which are operated under the leadership of the Max Planck Society.

    H.E.S.S. Čerenkov Telescope Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg searches for cosmic rays, altitude, 1,800 m (5,900 ft)

    MAGIC Čerenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia, La Palma, Spain)), Altitude 2,396 m (7,861 ft)

    Gamma-ray bursts (GRB) are sudden, short bursts of gamma radiation happening about once a day somewhere in the visible universe. According to current knowledge, they originate from colliding neutron stars or from supernova explosions of giant suns collapsing into a black hole. “Gamma-ray bursts are the most powerful explosions known in the universe and typically release more energy in just a few seconds than our Sun during its entire lifetime – they can shine through almost the entire visible universe,” explains David Berge, head of gamma-ray astronomy at DESY. The cosmic phenomenon was discovered by chance at the end of the 1960s by satellites used to monitor compliance with the nuclear test ban on Earth.

    Since then, astronomers have been studying gamma-ray bursts with satellites, as Earth’s atmosphere very effectively absorbs gamma rays. Astronomers have developed specialised telescopes that can observe a faint blue glow called Čerenkov light that cosmic gamma rays induce in the atmosphere, but these instruments are only sensitive to gamma rays with very high energies. Unfortunately, the brightness of gamma-ray bursts falls steeply with increasing energy. Čerenkov telescopes have identified many sources of cosmic gamma rays at very high energies, but no gamma-ray bursts. Satellites, on the other hand, have much too small detectors to be sensitive to the low brightness of gamma-ray bursts at very high energies. So, it was effectively unknown, if the monster explosions emit gamma rays also in the very-high-energy regime.

    Scientists have tried for many years, to catch a gamma-ray burst with Čerenkov telescopes. Then suddenly, between summer 2018 and January 2019, two international teams of astronomers, both involving DESY scientists, detected gamma rays from two GRB events for the first time from the ground. On 20 July 2018, faint afterglow emission of GRB 180720B in the gamma-ray regime was observed with the 28-metre telescope of the High-Energy Stereoscopic System H.E.S.S. in Namibia. On 14 January 2019, bright early emission from GRB 190114C was detected by the Major Atmospheric Gamma Imaging Čerenkov (MAGIC) telescopes on La Palma, and immediately announced to the astronomical community.

    Both observations were triggered by gamma-ray satellites of the US space agency NASA that monitor the sky for gamma-ray bursts and send automatic alerts to other gamma-ray observatories upon detection. “We were able to point to the region of origin so quickly that we could start observing only 57 seconds after the initial detection of the explosion,” reports Cosimo Nigro from the MAGIC group at DESY, who was in charge of the observation shift at that time. “In the first 20 minutes of observation, we detected about thousand photons from GRB 190114C.”

    MAGIC registered gamma-rays with energies between 200 and 1000 billion electron volts (0.2 to 1 teraelectronvolts). “These are by far the highest energy photons ever discovered from a gamma-ray burst,” says Elisa Bernardini, leader of the MAGIC group at DESY. For comparison: visible light is in the range of about 1 to 3 electron volts.

    The rapid discovery allowed to quickly alert the entire observational community. As a result, more than twenty different telescopes had a deeper look at the target. This allowed to pinpoint the details of the physical mechanism responsible for the highest-energy emission, as described in the second paper led by the MAGIC collaboration. Follow-up observations placed GRB 190114C at a distance of more than four billion light years. This means, its light travelled more than four billion years to us, or about a third of the current age of the universe.

    GRB 180720B, at a distance of six billion light years even further away, could still be detected in gamma rays at energies between 100 and 440 billion electron volts long after the initial blast. “Surprisingly, the H.E.S.S. telescope observed a surplus of 119 gamma quanta from the direction of the burst more than ten hours after the explosion event was first seen by satellites,” says Stefan Ohm, head of the H.E.S.S. group at DESY.

    “The detection came quite unexpected, as gamma-ray bursts are fading fast, leaving behind an afterglow which can be seen for hours to days across many wavelengths from radio to X-rays, but had never been detected in very-high-energy gamma rays before,” adds DESY theorist Andrew Taylor, who contributed to the H.E.S.S. analysis. “This success is also due to an improved follow-up strategy in which we also concentrate on observations at later times after the actual star collapse.”

    The detection of gamma-ray bursts at very high energies provides important new insights into the gigantic explosions. “Having established that GRBs produce photons of energies hundreds of billion times higher than visible light, we now know that GRBs are able to efficiently accelerate particles within the explosion ejecta,” says DESY researcher Konstancja Satalecka, one of the scientists coordinating GRB searches in the MAGIC collaboration. “What’s more, it turns out we were missing approximately half of their energy budget until now. Our measurements show that the energy released in very-high-energy gamma-rays is comparable to the amount radiated at all lower energies taken together. That is remarkable!”

    To explain how the observed very-high-energy gamma rays are generated is challenging. Both groups assume a two-stage process: First, fast electrically charged particles from the explosion cloud are deflected in the strong magnetic fields and emit so-called synchrotron radiation, which is of the same nature as the radiation that can be produced in synchrotrons or other particle accelerators on Earth, for example at DESY. However, only under fairly extreme conditions would the synchrotron photons from the explosion be able to reach the very high energies observed. Instead, the scientists consider a second step, where the synchrotron photons collide with the fast particles that generated them, which boosts them to the very high gamma-ray energies recorded. The scientists call the latter step inverse Compton scattering.

    Observation of inverse Compton emission from a long γ-ray burst; The MAGIC CollaborationNature

    “For the first time, the two instruments have measured gamma radiation from gamma-ray bursts from the ground,” concludes Berge. “These two groundbreaking observations have established gamma-ray bursts as sources for terrestrial gamma-ray telescopes. This has the potential to significantly advance our understanding of these violent phenomena.” The scientists estimate that up to ten such events per year can be observed with the planned Čerenkov Telescope Array (CTA), the next generation gamma-ray observatory. The CTA will consist of more than 100 individual telescopes of three types that will be built at two locations in the northern and southern hemispheres. DESY is responsible for the construction of the medium-sized telescopes and will host CTA’s Science Data Management Centre on its campus in Zeuthen. CTA observations are expected to start in 2023 at the earliest.

    ________________________________________
    Background information

    The detection of the very high-energy gamma rays on Earth was achieved with specialised telescopes that do not observe the cosmic gamma rays directly, but rather their effect on Earth’s atmosphere: When an energetic cosmic gamma ray hits Earth’s atmosphere, it shatters molecules and atoms.

    This process creates an avalanche of particles called an air shower.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

    The shower particles are so energetic that they move faster through the air than light – although not faster than light in a vacuum, which according to Albert Einstein’s theory of relativity is the absolute upper speed limit. The result is a bluish glow, a kind of optical counterpart to the supersonic bang. This Čerenkov light, named after its discoverer, can be observed by Čerenkov telescopes such as those of the H.E.S.S. and MAGIC observatories or the planned CTA.

    The H.E.S.S. observations were first announced at the CTA science symposium in May 2019. The MAGIC observations were distributed in an Astronomers’ Telegram (ATel) on 14 January 2019.

    The H.E.S.S. consortium consists of more than 250 researchers from 41 institutes in 12 countries. The MAGIC consortium brings together 280 members from 37 institutes in 12 countries. The MAGIC group at DESY is partially funded by a grant from the Helmholtz Association for excellent women researchers.

    ________________________________________

    See the full article here .


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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 2:37 pm on October 28, 2019 Permalink | Reply
    Tags: A decisive function for the young field of multi-messenger astronomy (MMA)., DESY, New insights into high-energy phenomena such as supernova explosions; colliding neutron stars and active black holes., The satellite will search for the origin of the heavy chemical elements., The UV camera which DESY is developing and building will be the heart of the telescope., ULTRASAT satellite, ULTRASAT will study the sky in the ultraviolet range (220 to 280 nanometres wavelength) of the electromagnetic spectrum.,   

    From DESY: “UV Satellite Will Open New View on Exploding Stars and Black Holes” 

    DESY
    From DESY

    2019/10/28

    DESY to build 100-megapixel camera for Israeli space telescope.

    A new space telescope will open up an unprecedented view of the universe in ultraviolet light: The ULTRASAT satellite will provide fundamental new insights into high-energy phenomena such as supernova explosions, colliding neutron stars and active black holes, all of which can also generate gravitational waves and act as cosmic particle accelerators. On Monday in Rehovot, Israel, the President of the Helmholtz Association, Otmar D. Wiestler, and the Director of the Helmholtz centre DESY, Helmut Dosch, agreed with the Weizmann Institute of Science on a cooperation for German participation in the Israeli-led project. DESY will build the 100-megapixel UV camera for the space telescope. For the project, DESY is working with the German Aerospace Center DLR, which also is a member of the Helmholtz Association.

    Weizmann Institute Campus

    “Helmholtz has had many excellent scientific collaborations with Israeli partners for decades. Together with the Weizmann Institute of Science, we are now taking another important step in the field of astrophysics. I am extremely pleased about this,” said Helmholtz President Otmar D. Wiestler. “The cooperation on the ULTRASAT space telescope has the potential to create a completely new basis for the detection of gravitational waves and related astrophysical events, at the highest international level.”

    DESY Director Helmut Dosch added: “We have a long and fruitful cooperation with a number of Israeli partners. We are now continuing this success story with our participation in Weizmann Institute of Science’s challenging satellite project.” DESY’s Research Director for Astroparticle Physics, Christian Stegmann, emphasised: “ULTRASAT offers us unique insights into the high-energy universe. With the camera for the telescope, DESY will be able to combine and contribute its outstanding expertise in detector development for astroparticle physics and X-ray physics.”

    ULTRASAT will study the sky in the ultraviolet range (220 to 280 nanometres wavelength) of the electromagnetic spectrum and have a particularly large field of view of 225 square degrees – about 1200 times as large as the full moon appears in our sky. “This unique configuration will help us answer some of the big questions in astrophysics,” said Eli Waxman, principal investigator of ULTRASAT at the Weizmann Institute of Science.

    2
    Collage of the satellite with typical observation targets like supernova explosions (top left), merging neutron stars (bottom left) and active black holes (top right). Photomontage: DESY, with material from NASA and Weizmann Institute of Science

    For example, the satellite will search for the origin of the heavy chemical elements. Apart from the lightest elements like hydrogen and helium, the elements were almost exclusively created by nuclear fusion in the cosmos. Stars produce their energy from this nuclear fusion, but this only works up to iron. The fusion of heavier elements such as lead or gold costs energy. Their synthesis takes place in the most powerful processes in the universe, such as the explosion of a star as a supernova or the collision of two neutron stars – the nuclei of burnt-out suns that have collapsed under their own weight to such an extent that they have a density like a gigantic atomic nucleus. Every gold atom on Earth and in the rest of the cosmos comes from an exploding sun or from a neutron star crash.

    “We want to understand exactly how the elements are produced and how they are distributed,” explains David Berge, Lead Scientist at DESY. Both, supernova explosions and neutron star collisions can be followed particularly well in UV light, as Berge points out. “The direct phase of a supernova in the first minutes, hours and days is mainly seen in the UV. During this time, the UV light contains characteristic signatures that indicate the predecessor star.” Later, a shockwave breaks out of the hot fireball, within which charged subatomic particles are also accelerated to high energies. “The satellite can therefore help us to understand the origin of such cosmic particle accelerators,” says Berge. “We also want to find out which type of star explodes in which kind of supernova.”

    ULTRASAT is particularly sensitive to high-energy phenomena. “Everything that gets extremely hot shines brightly in the UV light,” reports DESY researcher Rolf Bühler, project manager for the UV camera. This includes active black holes, which absorb matter from their environment and also accelerate particles, and colliding neutron stars. The observation of neutron star crashes can not only provide information about element synthesis in the cosmos, but is also of great importance for gravitational wave research. “If gravitational waves are registered by merging neutron stars, their position can so far only be coarsely resolved on the basis of the gravitational wave data,” explains Bühler. “ULTRASAT can orient itself to the target region within a maximum of 30 minutes and, thanks to its large field of view, can then determine the exact position almost immediately.”

    3
    Infographic: DESY, Sven Stein

    The satellite thus has a decisive function for the young field of multi-messenger astronomy (MMA), which studies the universe via various messengers such as cosmic particles, gravitational waves and electromagnetic radiation and forms a new area of research at DESY. With its large field of view, the satellite will have a particularly large section of the sky in view and will thus also be able to detect unknown objects that suddenly flare up in the UV range.

    With a total weight of only 160 kilograms and a volume of less than one cubic metre, ULTRASAT (Ultraviolet Transient Astronomy Satellite) is a small scientific satellite. The Weizmann Institute of Science and the Israeli Space Agency ISA share funding and management. The launch is scheduled for 2023. The space telescope will then collect data for three years. It will be put in a high orbit about 35,000 kilometres above Earth’s surface. This guarantees that disturbances from the ultraviolet background radiation, which Earth’s atmosphere reflects from the sun, are negligible and allows large areas of the sky to be surveyed. UV radiation can only be observed from orbit because it is largely absorbed and reflected by the atmosphere.

    The UV camera, which DESY is developing and building, will be the heart of the telescope. It will have a UV-sensitive sensor area of nine by nine centimetres and a resolution of 100 megapixels. With these parameters, the developers are breaking new ground: A UV space camera with such a resolution and sensitivity has never been built before. For the camera, DESY experts in astroparticle physics work together with specialists in detector development from the field of research with synchrotron radiation. With this project, DESY is contributing about 5 million euros to the satellite, which will cost about 70 million euros in total.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 11:43 am on October 28, 2019 Permalink | Reply
    Tags: ALPS-II, , , , DESY,   

    From DESY: “Dark Matter search enters new chapter” 

    DESY
    From DESY

    2019/10/27

    First magnet installed for the ALPS-II experiment at DESY.

    1
    Artist’s impression of the ALPS II experiment. Image: DESY, Scicom Lab

    1
    The ALPS I experiment laboratory surrounded by superconducting HERA dipole magnet.

    The international ALPS II (“Any light particle search”) collaboration installed the first of 24 superconducting magnets today, marking the start of the installation of a unique particle physics experiment to look for dark matter. Located at the German research centre DESY in Hamburg, it is set to start taking data in 2021 by looking for dark matter particles that literally make light shine through a wall, thus providing clues to one of the biggest questions in physics today: what is the nature of dark matter?

    “It is very exciting to see the project that many of us have been working on for so many years finally taking shape in the tunnel,” ALPS-II spokesman Axel Linder from DESY said. “When installation and commissioning proceed as planned we will be able to start the search in the first half of 2021.”

    Dark matter is one of the greatest mysteries in physics. Observations and calculations of the motion of stars in galaxies, for example, show that there must be more matter in the Universe than we can account for with matter particles known today. In fact, dark matter must make up 85 % of all the matter in the Universe. However, currently we don’t know what it is. But we know that it does not interact with regular matter and is essentially invisible, so that it is called “dark”.

    There are several theories that try to explain the nature of dark matter and the particles it may consist of. One of these theories states that dark matter consists of very light-weight particles with very specific properties. One example is the axion which was originally postulated to explain aspects of the strong interaction, one of the fundamental forces of nature. There are also puzzling astrophysical observations such as discrepancies in the evolution of stellar systems, which might also be explained by the existence of axions or axion-like particles.

    This is where ALPS II comes in. It is designed to create and detect those axions. A strong magnetic field can make axions switch to photons and vice versa. “This bizarre property was already exploited in the initial ALPS I experiment which we ran from 2007 to 2010. Despite its limited size, it achieved the world-wide best sensitivities for these kinds of experiments,” said Benno Willke, the leader of the ALPS and of the laser development group at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and at the Institute for Gravitational Physics at Leibniz Universität of Hannover.

    ALPS II is being set up in a straight tunnel section of DESY’s former particle physics accelerator HERA.

    DESY HERA , 1992 to 2007

    Twenty-four superconducting accelerator magnets, twelve on either side of a wall, house two 120-metre-long optical cavities. A powerful and intricate laser system produces light that is amplified by the cavity inside the magnetic field and will, to a very small fraction, convert into dark matter particles. A light-blocking barrier – a wall – separates the second compartment of ALPS II, but this wall is no hurdle for axions and similar particles that can easily pass through it. In the second cavity dark matter particles would convert back into light. The tiny signal will be picked up by dedicated detection systems.

    The more than 1,000-fold improvement in sensitivity of ALPS II is made possible by the increased length of the magnet strings but also by significant advances in optical technologies. “These advances emerged from the work on gravitational wave interferometers such as GEO600 and LIGO, and nicely show how technological advances in one area enable progress in others,” said Co-Spokesperson Guido Mueller from the University of Florida in Gainesville.

    ALPS II is also an example of recycling in research: it does not only reuse a stretch of tunnel that once housed DESY’s flagship particle accelerator, but it also reuses the very magnets that drove protons around the ring until 2007. These magnets needed to be reengineered to fit the ALPS purposes: the slight bend needed in an accelerator ring had to be removed to allow photons to propagate through them.

    The ALPS II collaboration consists of some 25 scientists from these institutes: DESY, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and the Institute for Gravitational Physics at Leibniz Universität of Hannover, the Johannes Gutenberg-Universität Mainz, the University of Florida in Gainesville, and Cardiff University. Beyond that, the collaboration is supported by partners worldwide like the National Metrology Institute (PTB) in Germany and the National Institute of Standards and Technology in the USA. The experiment is mainly funded by DESY, the Heising-Simons Foundation, the US National Science Foundation, the German Volkswagen Stiftung and German Research Foundation (DFG).

    At DESY, ALPS II might be just the first experiment within a new strategic approach to tackle dark matter. “International collaborations are preparing the IAXO experiment to search for axions emitted by the Sun as well as the MADMAX detector, which will look directly for axions as constituents of the local dark matter surrounding us”, explained Joachim Mnich, DESY’s director for particle physics.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 7:52 am on September 24, 2019 Permalink | Reply
    Tags: Buckminsterfullerenes-buckyballs, DESY,   

    From SLAC and DESY: “Breaking up buckyballs is hard to do” 

    From SLAC National Accelerator Lab

    DESY
    From DESY

    4

    September 23, 2019
    Ali Sundermier

    How molecular footballs burst in an X-ray laser beam.

    As reported in Nature Physics, an international research team observed how soccer ball-shaped molecules made of carbon atoms burst in the beam of an X-ray laser. The molecules, called buckminsterfullerenes – buckyballs for short ­– consist of 60 carbon atoms arranged in alternating pentagons and hexagons like the leather coat of a soccer ball. These molecules were expected to break into fragments after being bombarded with photons, but the researchers watched in real time as buckyballs resisted the attack and delayed their break-up.

    1
    An illustration shows how soccer ball-shaped molecules called buckyballs ionize and break up when blasted with an X-ray laser. A team of experimentalists and theorists identified chemical bonds and charge transfers as crucial factors that significantly delayed the fragmentation process by about 600 millionths of a billionth of a second. (Greg Stewart/SLAC National Accelerator Laboratory)

    2
    Computer simulated evolution of a C60 molecule at 0, 60 and 240 femto seconds after the X-ray flash. Credit: DESY, Zoltan Jurek

    “Buckyballs are well suited as a simple model system for biomolecules,” explains Robin Santra, who is a lead scientist at DESY at the Center for Free-Electron Laser Science (CFEL) and a physics professor at the Universität Hamburg. “Since they consist of only one type of atom and have a symmetrical structure, they can be well represented in theory and experiment. This is a first step before the investigation of molecules from different types of atoms.”

    The team was led by Nora Berrah, a professor at the University of Connecticut, and included researchers from the Department of Energy’s SLAC National Accelerator Laboratory and the Deutsches Elektronen-Synchrotron (DESY) in Germany. The researchers focused their attention on examining the role of chemical effects, such as chemical bonds and charge transfer, on the buckyball’s fragmentation.

    Using X-ray laser pulses from SLAC’s Linac Coherent Light Source (LCLS) [below], the team showed how the bursting process, which takes only a few hundred femtoseconds, or millionths of a billionth of a second, unfolds over time. The results will be important for the analysis of sensitive proteins and other biomolecules, which are also frequently studied using bright X-ray laser flashes, and they also strengthen confidence in protein analysis with X-ray free-electron lasers (XFELs).

    “This investigation uncovered for the first time the persistence of the molecular structure, which thwarted fragmentation over a timescale of hundreds of femtoseconds” Berrah says. “With the dawn of several new XFELs in the world, the findings lay the foundation for a deeper understanding of XFEL-induced radiation damage, which will have a strong impact on biomolecular imaging.”

    What follows then is not an actual explosion,” explains the scientist. “Instead, the buckyballs dissolve comparatively slowly. Carbon atoms gradually evaporate – with many more neutral ones than electrically charged ones, which was surprising.” Since the fragmentation of the buckyballs on this time scale is not explosive but happens gradually, the researchers speak of the evaporation of the atoms. The experimental data could only be meaningfully interpreted with the help of theoretical modelling of the process.

    “Typically, about 25 neutral and only 15 electrically charged carbon atoms fly out of the molecule,” Santra explains. “The rest form fragments of several atoms.” The whole process takes about 600 femtoseconds. This is still unimaginably short by human standards, but extremely long for structural analysis with X-ray lasers. “In the typically 20 femtoseconds of an X-ray laser flash, the atoms move a maximum of 0.1 nanometers – that is in the range of individual atom diameters and smaller than the measurement accuracy of structural analysis.” One nanometer is one millionth of a millimeter.

    For the structural analysis of proteins, researchers usually grow small crystals from the biomolecules. The bright X-ray laser flash is then diffracted at the crystal lattice and generates a typical diffraction pattern from which the crystal structure and with it the spatial structure of the individual proteins can be calculated. The spatial structure of a protein reveals details about its exact function. The protein crystals are very sensitive and evaporate through the X-ray laser flash. However, previous investigations had shown that the crystal remains intact long enough to generate the diffraction image before evaporation and thus to reveal its spatial structure.

    The new study now confirms that this is also the case with individual molecules that are not bound in a crystal lattice. “Our findings with buckyballs are likely to play a role in most other molecules,” Santra emphasises. Since many biomolecules are notoriously difficult to crystallise, researchers hope to be able to determine the structure of ensembles of non-crystallised proteins or even individual biomolecules with X-ray lasers in the future. The results obtained now lay the foundation for a deeper understanding and quantitative modelling of the radiation damage in biomolecules induced by X-ray laser flashes, the scientists write.

    The study also involved researchers from Imperial College London; University of Gothenburg in Sweden; University of Texas; Synchrotron SOLEIL in France; Kansas State University; Tohoku University in Japan; State University of New York at Potsdam; and Max Planck Institute for Nuclear Physics, Max Born Institute and University of Hamburg, all in Germany.

    See the full article here .
    See the full DESY article here .


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    Please help promote STEM in your local schools.

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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 4:25 pm on July 16, 2019 Permalink | Reply
    Tags: , DESY, Michigan State University, , , ,   

    From U Wisconsin IceCube Collaboration: A Flock of Articles on NSF Grant to Upgrade IceCube 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    From From U Wisconsin IceCube Collaboration

    From U Wisconsin: “UW lab gears up for another Antarctic drilling campaign”

    With news that the National Science Foundation (NSF) and international partners will support an upgrade to the IceCube neutrino detector at the South Pole, the UW–Madison lab that built the novel drill used to bore mile-deep holes in the Antarctic ice is gearing up for another drilling campaign.

    The UW’s Physical Sciences Laboratory (PSL), which specializes in making customized equipment for UW–Madison researchers, will once again lead drilling operations. The $37 million upgrade announced this week (July 16, 2019) will expand the IceCube detector by adding seven new strings of 108 optical modules each to study the basic properties of neutrinos, phantom-like particles that emanate from black holes and exploding stars, but that also cascade through Earth’s atmosphere as a result of colliding subatomic particles.

    1
    “It takes a crew of 30 people to run this 24/7. It’s the people that make it work,” says Bob Paulos, director of the Physical Sciences Lab. Photo: Bryce Richter

    See the full article here .

    From U Wisconsin: “IceCube: Antarctic neutrino detector to get $37 million upgrade”

    2
    The IceCube Neutrino Observatory is located at NSF’s Amundsen-Scott South Pole Station. Management and operation of the observatory is through the Wisconsin IceCube Particle Astrophysics Center at UW–Madison. Raffaela Busse, IceCube / NSF

    IceCube, the Antarctic neutrino detector that in July of 2018 helped unravel one of the oldest riddles in physics and astronomy — the origin of high-energy neutrinos and cosmic rays — is getting an upgrade.

    This month, the National Science Foundation (NSF) approved $23 million in funding to expand the detector and its scientific capabilities. Seven new strings of optical modules will be added to the 86 existing strings, adding more than 700 new, enhanced optical modules to the 5,160 sensors already embedded in the ice beneath the geographic South Pole.

    The upgrade, to be installed during the 2022–23 polar season, will receive additional support from international partners in Japan and Germany as well as from Michigan State University and the University of Wisconsin–Madison. Total new investment in the detector will be about $37 million.

    See the full article here .

    From Niels Bohr Institute: “A new Upgrade for the IceCube detector”

    3
    Illustration of the IceCube laboratory under the South Pole. The sensors detecting neutrinos are attached to the strings lowered into the ice. The upgrade will take place in the Deep Core area. Illustration: IceCube/NSF

    Neutrino Research:

    The IceCube Neutrino Observatory in Antarctica is about to get a significant upgrade. This huge detector consists of 5,160 sensors embedded in a 1x1x1 km volume of glacial ice deep beneath the geographic South Pole. The purpose of the installation is to detect neutrinos, the “ghost particles” of the Universe. The IceCube Upgrade will add more than 700 new and enhanced optical sensors in the deepest, purest ice, greatly improving the observatory’s ability to measure low-energy neutrinos produced in the Earth’s atmosphere. The research in neutrinos at the Niels Bohr Institute, University of Copenhagen is led by Associate Professor Jason Koskinen

    See the full article here .

    From Michigan State University: “Upgrade for neutrino detector, thanks to NSF grant”

    5
    The IceCube Neutrino Observatory, the Antarctic detector that identified the first likely source of high-energy neutrinos and cosmic rays, is getting an upgrade. Courtesy of IceCube

    The IceCube Neutrino Observatory, the Antarctic detector that identified the first likely source of high-energy neutrinos and cosmic rays, is getting an upgrade.

    The National Science Foundation is upgrading the IceCube detector, extending its scientific capabilities to lower energies, and bridging IceCube to smaller neutrino detectors worldwide. The upgrade will insert seven strings of optical modules at the bottom center of the 86 existing strings, adding more than 700 new, enhanced optical modules to the 5,160 sensors already embedded in the ice beneath the geographic South Pole.

    The upgrade will include two new types of sensor modules, which will be tested for a ten-times-larger future extension of IceCube – IceCube-Gen2. The modules to be deployed in this first extension will be two to three times more sensitive than the ones that make up the current detector. This is an important benefit for neutrino studies, but it becomes even more relevant for planning the larger IceCube-Gen2.

    The $37 million extension, to be deployed during the 2022-23 polar field season, has now secured $23 million in NSF funding. Last fall, the upgrade office was set up, thanks to initial funding from NSF and additional support from international partners in Japan and Germany as well as from Michigan State University and the University of Wisconsin-Madison.

    See the full article here .

    From U Wisconsin IceCube: “The IceCube Upgrade: An international effort”

    The IceCube Upgrade project is an international collaboration made possible not only by support from the National Science Foundation but also thanks to significant contributions from partner institutions in the U.S. and around the world. Our national and international collaborators play a huge role in manufacturing new sensors, developing firmware, and much more. Learn more about a few of our partner institutions below.

    8
    The Chiba University group poses with one of the new D-Egg optical detectors. Credit: Chiba University

    Chiba University is responsible for the new D-Egg optical detectors, 300 of which will be deployed on the new Upgrade strings. A D-Egg is 30 percent smaller than the original IceCube DOM, but its photon detection effective area is twice as large thanks to two 8-inch PMTs in the specially designed egg-shaped vessel made of UV-transparent glass. Its up-down symmetric detection efficiency is expected to improve our precision for measuring Cherenkov light from neutrino interactions. The newly designed flasher devices in the D-Egg will also give a better understanding of optical characteristics in glacial ice to improve the resolution of arrival directions of cosmic neutrinos.

    See the full article here .

    From DESY: “Neutrino observatory IceCube receives significant upgrade”

    6
    Deep down in the perpetual ice of Antarctica IceCube watches out for a faint bluish glow that indicates a rare collision of a cosmic neutrino within the ice. Artist’s concept: DESY, Science Communication Lab

    Particle detector at the South Pole will be expanded to comprise a neutrino laboratory

    The international neutrino observatory IceCube at the South Pole will be considerably expanded in the coming years. In addition to the existing 5160 sensors, a further 700 optical modules will be installed in the perpetual ice of Antarctica. The National Science Foundation in the USA has approved 23 million US dollars for the expansion. The Helmholtz Centres DESY and Karlsruhe Institute of Technology (KIT) are supporting the construction of 430 new optical modules with a total of 5.7 million euros (6.4 million US dollars), which will turn the observatory into a neutrino laboratory. IceCube, for which Germany with a total of nine participating universities and the two Helmholtz Centres is the most important partner after the USA, had published convincing indications last year of a first source of high-energy neutrinos from the cosmos.

    See the full article here .

    See the full articles above .

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    Please help promote STEM in your local schools.

    Stem Education Coalition
    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

     
  • richardmitnick 11:02 am on July 11, 2019 Permalink | Reply
    Tags: , , DESY, , , Terahertz accelerators,   

    From DESY: “Experimental mini-accelerator achieves record energy” 

    DESY
    From DESY

    11 July 2019

    1
    Coupled terahertz device significantly improves electron beam quality

    Scientists at DESY have achieved a new world record for an experimental type of miniature particle accelerator: For the first time, a terahertz powered accelerator more than doubled the energy of the injected electrons. At the same time, the setup significantly improved the electron beam quality compared to earlier experiments with the technique, as Dongfang Zhang and his colleagues from the Center for Free-Electron Laser Science (CFEL) at DESY report in the journal Optica. “We have achieved the best beam parameters yet for terahertz accelerators,” said Zhang.

    “This result represents a critical step forward for the practical implementation of terahertz-powered accelerators,” emphasized Franz Kärtner, who heads the ultrafast optics and X-rays group at DESY. Terahertz radiation lies between infrared and microwave frequencies in the electromagnetic spectrum and promises a new generation of compact particle accelerators. “The wavelength of terahertz radiation is about a hundred times shorter than the radio waves currently used to accelerate particles,” explained Kärtner. “This means that the components of the accelerator can also be built to be around a hundred times smaller.” The terahertz approach promises lab-sized accelerators that will enable completely new applications for instance as compact X-ray sources for materials science and maybe even for medical imaging. The technology is currently under development.

    Since terahertz waves oscillate so fast, every component and every step has to be precisely synchronized. “For instance, to achieve the best energy gain, the electrons have to hit the terahertz field exactly during its accelerating half cycle,” explained Zhang. In accelerators, particles usually do not fly in a continuous beam, but are packed in bunches. Because of the fast-changing field, in terahertz accelerators these bunches have to be very short to ensure even acceleration conditions along the bunch.

    “In previous experiments the electron bunches were too long”, said Zhang. “Since the terahertz field oscillates so quickly, some of the electrons in the bunch were accelerated, while others were even slowed down. So, in total there was just a moderate average energy gain, and, what is more important, a wide energy spread, resulting in what we call poor beam quality.” To make things worse, this effect strongly increased the emittance, a measure for how well a particle beam is bundled transversally. The tighter, the better – the smaller the emittance.

    To improve the beam quality, Zhang and his colleagues built a two-step accelerator from a multi-purpose device they had developed earlier: The Segmented Terahertz Electron Accelerator and Manipulator (STEAM) can compress, focus, accelerate and analyze electron bunches with terahertz radiation. The researchers combined two STEAM devices in line. They first compressed the incoming electron bunches from about 0.3 millimetres in length to just 0.1 millimetres. With the second STEAM device, they accelerated the compressed bunches. “This scheme requires control on the level of quadrillionths of a second, which we achieved,“ said Zhang “This led to a fourfold reduction of the energy spread and improved the emittance sixfold, yielding the best beam parameters of a terahertz accelerator so far.”

    The net energy gain of the electrons that were injected with an energy of 55 kiloelectron volts (keV) was 70 keV. “This is the first energy boost greater than 100 percent in a terahertz powered accelerator,” emphasised Zhang. The coupled device produced an accelerating field with a peak strength of 200 million Volts per metre (MV/m) – close to state-of-the-art strongest conventional accelerators. For practical applications this still has to be significantly improved. “Our work shows that even a more than three times stronger compression of the electron bunches is possible. Together with a higher terahertz energy, acceleration gradients in the regime of gigavolts per metre seem feasible,” summarized Zhang. “The terahertz concept thus appears increasingly promising as a realistic option for the design of compact electron accelerators.”

    The achieved progress is also central for the ERC funded project AXSIS (frontiers in Attosecond X-ray Science: Imaging and Spectroscopy) at CFEL, which pursues short pulse X-ray spectroscopy and imaging of complex biophysical processes, where the short X-ray pulses are generated with THz based electron accelerators. CFEL is a joint venture of DESY, the University of Hamburg and the Max Planck Society.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 12:02 pm on June 18, 2019 Permalink | Reply
    Tags: "Four decades of gluons", , DESY, Forty years ago in 1979 experiments at the DESY laboratory in Germany provided the first direct proof of the existence of gluons, Gluons are the carriers of the strong force that “glue” quarks into protons neutrons and other particles known collectively as hadrons., John Ellis   

    From CERN: “Four decades of gluons” 

    Cern New Bloc

    Cern New Particle Event


    From CERN

    18 June, 2019
    Ana Lopes

    1
    A three-jet event detected by the TASSO detector at DESY (Image: Oxford PPU)

    Forty years ago, in 1979, experiments at the DESY laboratory in Germany provided the first direct proof of the existence of gluons – the carriers of the strong force that “glue” quarks into protons, neutrons and other particles known collectively as hadrons. This discovery was a milestone in the history of particle physics, as it helped establish the theory of the strong force, known as quantum chromodynamics.

    The results followed from an idea that struck theorist John Ellis while walking in CERN’s corridors in 1976. As Ellis recounts, he was walking over the bridge from the CERN cafeteria back to his office, turning the corner by the library, when it occurred to him that “the simplest experimental situation to search directly for the gluon would be through production via bremsstrahlung in electron–positron annihilation”. In this process, an electron and a positron (the electron’s antiparticle) would annihilate and would occasionally produce three “jets” of particles, one of which being generated by a gluon radiated by a quark–antiquark pair.

    Ellis and theorists Mary Gaillard and Graham Ross then went on to write a paper titled “Search for Gluons in e+-e– Annihilation” in which they described a calculation of the process and showed how the PETRA collider at DESY and the PEP collider at SLAC would be able to observe it. Ellis then visited DESY, gave a seminar about the idea and talked to experimentalists preparing to work at PETRA.

    A couple of years later, and following more papers by Ellis, Gaillard and other theorists, PETRA was being commissioned and getting into the energy range required to test this theory. Soon after, at the International Neutrino Conference in Bergen, Norway, on 18 June 1979, researchers presented a three-jet collision event that had just been detected by the TASSO experiment at PETRA.

    At the European Physical Society conference at CERN a couple of weeks later, the TASSO collaboration presented several three-jet events and results of analyses that showed that the gluon had been discovered. One month later, in August 1979, three other experiments at PETRA showed similar events that lent support to TASSO’s findings.

    Find out more about the discovery in DESY’s coverage of the 40-year anniversary, in Ellis’ account, and in this 2004 CERN Courier article.

    See the full article here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Meet CERN in a variety of places:

    Quantum Diaries
    QuantumDiaries

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS

    CERN ATLAS Image Claudia Marcelloni CERN/ATLAS


    ALICE

    CERN/ALICE Detector


    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN map

    CERN LHC Grand Tunnel

    CERN LHC particles

     
  • richardmitnick 12:24 pm on June 13, 2019 Permalink | Reply
    Tags: , , , Compact particle accelerators, DESY,   

    From DESY: “Laser trick produces high-energy terahertz pulses” 

    DESY
    From DESY

    2019/06/13

    Milestone for compact particle accelerators.

    A team of scientists from DESY and the University of Hamburg has achieved an important milestone in the quest for a new type of compact particle accelerator. Using ultra-powerful pulses of laser light, they were able to produce particularly high-energy flashes of radiation in the terahertz range having a sharply defined wavelength (colour). Terahertz radiation is to open the way for a new generation of compact particle accelerators that will find room on a lab bench. The team headed by Andreas Maier and Franz Kärtner from the Hamburg Center for Free-Electron Laser Science (CFEL) is presenting its findings in the journal Nature Communications. CFEL is jointly run by DESY, the University of Hamburg and the Max Planck Society.

    1
    From the colour difference of two slightly delayed laser flashes (left) a non-linear crystal generates an energetic terahertz pulse (right). Credit: DESY, Lucid Berlin

    The terahertz range of electromagnetic radiation lies between the infrared and microwave frequencies. Air travellers may be familiar with terahertz radiation from the full-body scanners used by airport security to search for objects hidden beneath a person’s garments. However, radiation in this frequency range might also be used to build compact particle accelerators. “The wavelength of terahertz radiation is about a thousand times shorter than the radio waves that are currently used to accelerate particles,” says Kärtner, who is a lead scientist at DESY. “This means that the components of the accelerator can also be built to be around a thousand times smaller.” The generation of high-energy terahertz pulses is therefore also an important step for the AXSIS (frontiers in Attosecond X-ray Science: Imaging and Spectroscopy) project at CFEL, funded by the European Research Council (ERC), which aims to open up completely new applications with compact terahertz particle accelerators.

    However, chivvying along an appreciable number of particles calls for powerful pulses of terahertz radiation having a sharply defined wavelength. This is precisely what the team has now managed to create. “In order to generate terahertz pulses, we fire two powerful pulses of laser light into a so-called non-linear crystal, with a minimal time delay between the two,” explains Maier from the University of Hamburg. The two laser pulses have a kind of colour gradient, meaning that the colour at the front of the pulse is different from that at the back. The slight time shift between the two pulses therefore leads to a slight difference in colour. “This difference lies precisely in the terahertz range,” says Maier. “The crystal converts the difference in colour into a terahertz pulse.”

    The method requires the two laser pulses to be precisely synchronised. The scientists achieve this by splitting a single pulse into two parts and sending one of them on a short detour so that it is slightly delayed before the two pulses are eventually superimposed again. However, the colour gradient along the pulses is not constant, in other words the colour does not change uniformly along the length of the pulse. Instead, the colour changes slowly at first, and then more and more quickly, producing a curved outline. As a result, the colour difference between the two staggered pulses is not constant. The difference is only appropriate for producing terahertz radiation over a narrow stretch of the pulse.

    That was a big obstacle towards creating high-energy terahertz pulses,” as Maier reports. “Because straightening the colour gradient of the pulses, which would have been the obvious solution, is not easy to do in practice.” It was co-author Nicholas Matlis who came up with the crucial idea: he suggested that the colour profile of just one of the two partial pulses should be stretched slightly along the time axis. While this still does not alter the degree with which the colour changes along the pulse, the colour difference with respect to the other partial pulse now remains constant at all times. “The changes that need to be made to one of the pulses are minimal and surprisingly easy to achieve: all that was necessary was to insert a short length of a special glass into the beam,” reports Maier. “All of a sudden, the terahertz signal became stronger by a factor of 13.” In addition, the scientists used a particularly large non-linear crystal to produce the terahertz radiation, specially made for them by the Japanese Institute for Molecular Science in Okazaki.

    “By combining these two measures, we were able to produce terahertz pulses with an energy of 0.6 millijoules, which is a record for this technique and more than ten times higher than any terahertz pulse of sharply defined wavelength that has previously been generated by optical means,” says Kärtner. “Our work demonstrates that it is possible to produce sufficiently powerful terahertz pulses with sharply defined wavelengths in order to operate compact particle accelerators.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior


    DESY Petra III

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 5:05 pm on April 15, 2019 Permalink | Reply
    Tags: , , , , , DESY, When an asteroid passes in front of a star the resulting diffraction pattern can reveal the star's angular size   

    From DESY: “Asteroids help scientists to measure the diameters of far away stars” 

    DESY
    From DESY

    2019/04/15

    New technique doubles resolution of angular size measurements.

    Using the unique capabilities of telescopes specialised on cosmic gamma rays, scientists have measured the smallest apparent size of a star on the night sky to date. The measurements with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) reveal the diameters of a giant star 2674 light-years away and of a sun-like star at a distance of 700 light-years.

    CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory,Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

    The study establishes a new method for astronomers to determine the size of stars, as the international team led by Tarek Hassan from DESY and Michael Daniel from the Smithsonian Astrophysical Observatory (SAO) reports in the journal Nature Astronomy.

    2
    When an asteroid passes in front of a star, the resulting diffraction pattern (here greatly exaggerated) can reveal the star’s angular size. Credit: DESY, Lucid Berlin

    Almost any star in the sky is too far away to be resolved by even the best optical telescopes. To overcome this limitation, the scientists used an optical phenomenon called diffraction to measure the star’s diameter. This effect illustrates the wave nature of light, and occurs when an object, such as an asteroid from our own solar system, passes in front of a star. “The incredibly faint shadows of asteroids pass over us everyday,” explained Hassan. “But the rim of their shadow isn’t perfectly sharp. Instead, wrinkles of light surround the central shadow, like water ripples.” This is a general optical phenomenon called a diffraction pattern and can be reproduced in any school lab with a laser hitting a sharp edge.

    The researchers used the fact that the shape of the pattern can reveal the angular size of the light source. However, different from the school lab, the diffraction pattern of a star occulted by an asteroid is very hard to measure. “These asteroid occultations are hard to predict,” said Daniel. “And the only chance to catch the diffraction pattern is to make very fast snapshots when the shadow sweeps across the telescope.” Astronomers have measured the angular size of stars this way that were occulted by the moon. This method works right down to angular diameters of about one milliarcsecond, which is about the apparent size of a two-cent coin atop the Eiffel Tower in Paris as seen from New York.

    However, not many stars in the sky are that “big”. To resolve even smaller angular diameters, the team employed Cherenkov telescopes. These instruments normally watch out for the extremely short and faint bluish glow that high-energy particles and gamma rays from the cosmos produce when they encounter and race through Earth’s atmosphere. Cherenkov telescopes do not produce the best optical images. But thanks to their huge mirror surface, usually segmented in hexagons like a fly’s eye, they are extremely sensitive to fast variations of light, including starlight.

    Using the four large VERITAS telescopes at the Fred Lawrence Whipple Observatory in Arizona, the team could clearly detect the diffraction pattern of the star TYC 5517-227-1 sweep past as it was occulted by the 60-kilometre asteroid Imprinetta on 22 February 2018. The VERITAS telescopes allowed to take 300 snapshots every second. From these data, the brightness profile of the diffraction pattern could be reconstructed with high accuracy, resulting in an angular, or apparent, diameter of the star of 0.125 milliarcseconds. Together with its distance of 2674 light-years, this means the star’s true diameter is eleven times that of our sun. Interestingly, this result categorises the star whose class was ambiguous before as a red giant star.

    The researchers repeated the feat three months later on 22 May 2018, when asteroid Penelope with a diameter of 88 kilometres occulted the star TYC 278-748-1. The measurements resulted in an angular size of 0.094 milliarcseconds and a true diameter of 2.17 times that of our sun. This time the team could compare the diameter to an earlier estimate based on other characteristics of the star that had placed its diameter at 2.173 times the solar diameter – an excellent match, although the earlier estimate was not based on a direct measurement.

    “This is the smallest angular size of a star ever measured directly,” Daniel emphasised. “Profiling asteroid occultations of stars with Cherenkov telescopes delivers a ten times better resolution than the standard lunar occultation method. Also, it is at least twice as sharp as available interferometric size measurements.” The uncertainty of these measurements are about ten per cent, as the authors write. “We expect this can be notably improved by optimising the set-up, for example narrowing the wavelength of the colours recorded,” said Daniel. Since different wavelengths are diffracted differently, the pattern is smeared out if too many colours are recorded at the same time.

    “Our pilot study establishes a new method to determine the true diameter of stars,” Hassan summarised. The scientists estimate that suitable telescopes could view more than one asteroid occultation per week. “Since the same star looks smaller the farther away it is, moving to smaller angular diameters also means extending the observation range,” explained Hassan. “We estimate that our method can analyse stars up to ten times as far away as the standard lunar occultation method allows. All together, the technique can deliver enough data for population studies.”

    The Harvard-Smithsonian Center for Astrophysics, the University of California at Los Angeles and at Santa Cruz, the Columbia University in New York, the University of Potsdam, the Iowa State University, the Purdue University, the University of Minnesota, the California State University, the National University of Ireland at Galway, the McGill University in Montreal, the University of Delaware, the University of Iowa, the University of Utah, the DePauw University in Greencastle, the University College Dublin, the University of Wisconsin-Madison, the Cork Institute of Technology, the University of Alabama, the University of Chicago, the Universidad Complutense de Madrid, the University of Durham and DESY contributed to this research.

    See the full article here .


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    Please help promote STEM in your local schools.

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    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

    DESY Petra III interior

    DESY Petra III

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    H1 detector at DESY HERA ring

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