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  • richardmitnick 3:20 pm on August 16, 2021 Permalink | Reply
    Tags: "Table-top electron camera catches ultrafast dynamics of matter", , , DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE), Electron diffraction is one way to investigate the inner structure of matter., , , , , , Terahertz radiation, The accelerator components-here a bunch compressor-can be a hundred times smaller., The scientists fired bunches with roughly 10000 electrons each at a silicon crystal that was heated by a short laser pulse., The system is perfectly synchronised since it is using just one laser for all steps: generating; manipulating; measuring; and compressing the electron bunches., Typically ultrafast electron diffraction (UED) uses bunch lengths-or exposure times-of some 100 femtoseconds which is 0.1 trillionths of a second.   

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) : “Table-top electron camera catches ultrafast dynamics of matter” 

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE)

    2021/08/13

    DESY team demonstrates first Terahertz enhanced electron diffractometer.
    Scientists at DESY have built a compact electron camera that can capture the inner, ultrafast dynamics of matter. The system shoots short bunches of electrons at a sample to take snapshots of its current inner structure and is the first such electron diffractometer that uses Terahertz radiation for pulse compression. The developer team around DESY scientists Dongfang Zhang and Franz Kärtner from the CFEL Center for Free-Electron Laser Science [Zentrum für Freie-Elektronen-Laserwissenschaft] (DE) validated their Terahertz-enhanced ultrafast electron diffractometer with the investigation of a silicon sample and present their work in the first issue of the journal Ultrafast Science, a new title in the Science group of scientific journals.

    1
    The system fits on a lab table. It is adjusted with the help of an optical laser (green). Credit: DESY, Timm Rohwer.

    Electron diffraction is one way to investigate the inner structure of matter. However, it does not image the structure directly. Instead, when the electrons hit or traverse a solid sample, they are deflected in a systematic way by the electrons in the solid’s inner lattice. From the pattern of this diffraction, recorded on a detector, the internal lattice structure of the solid can be calculated. To detect dynamic changes in this inner structure, short bunches of sufficiently bright electrons have to be used. “The shorter the bunch, the faster the exposure time,” says Zhang, who is now a professor at Shanghai Jiao Tong University [海交通大学](CN). “Typically ultrafast electron diffraction (UED) uses bunch lengths-or exposure times-of some 100 femtoseconds which is 0.1 trillionths of a second.”

    Such short electron bunches can be routinely produced with high quality by state-of-the-art particle accelerators. However, these machines are often large and bulky, partly due to the radio frequency radiation used to power them, which operates in the Gigahertz band. The wavelength of the radiation sets the size for the whole device. The DESY team is now using Terahertz radiation instead with roughly a hundred times shorter wavelengths. “This basically means, the accelerator components-here a bunch compressor-can be a hundred times smaller, too,” explains Kärtner, who is also a professor and a member of the cluster of excellence “CUI: Advanced Imaging of Matter“ at the University of Hamburg [Universität Hamburg](DE).

    2
    Schematic set-up of the Terahertz Ultrafast Electron Diffractometer. Credit: DESY, Dongfang Zhang.

    For their proof-of-principle study, the scientists fired bunches with roughly 10,000 electrons each at a silicon crystal that was heated by a short laser pulse. The bunches were about 180 femtoseconds long and show clearly how the crystal lattice of the silicon sample quickly expands within a picosecond (trillionths of a second) after the laser hits the crystal. “The behaviour of silicon under these circumstances is very well known, and our measurements fit the expectation perfectly, validating our Terahertz device,” says Zhang. He estimates that in an optimised set-up, the electron bunches can be compressed to significantly less than 100 femtoseconds, allowing even faster snapshots.

    On top of its reduced size, the Terahertz electron diffractometer has another advantage that might be even more important to researchers: “Our system is perfectly synchronised since we are using just one laser for all steps: generating; manipulating; measuring; and compressing the electron bunches, producing the Terahertz radiation and even heating the sample,” Kärtner explains. Synchronisation is key in this kind of ultrafast experiments. To monitor the swift structural changes within a sample of matter like silicon, researchers usually repeat the experiment many times while delaying the measuring pulse a little more each time. The more accurate this delay can be adjusted, the better the result. Usually, there needs to be some kind of synchronisation between the exciting laser pulse that starts the experiment and the measuring pulse, in this case the electron bunch. If both, the start of the experiment and the electron bunch and its manipulation are triggered by the same laser, the synchronisation is intrinsically given.

    In a next step, the scientists plan to increase the energy of the electrons. Higher energy means the electrons can penetrate thicker samples. The prototype set-up used rather low-energy electrons and the silicon sample had to be sliced down to a thickness of just 35 nanometres (millionths of a millimetre). Adding another acceleration stage could give the electrons enough energy to penetrate 30 times thicker samples with a thickness of up to 1 micrometre (thousandth of a millimetre), as the researchers explain. For even thicker samples, X-rays are normally used. While X-ray diffraction is a well established and hugely successful technique, electrons usually do not damage the sample as quickly as X-rays do. “The energy deposited is much lower when using electrons,“ explains Zhang. This could prove useful when investigating delicate materials.

    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 German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) 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.

    [/caption]

     
  • richardmitnick 10:44 am on July 5, 2021 Permalink | Reply
    Tags: "Chasing cosmic particles with radio antennas in Greenland's ice", , DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE), , The Radio Neutrino Observatory - RNO-G   

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) : “Chasing cosmic particles with radio antennas in Greenland’s ice” 

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE)

    2021/07/02

    Pioneering project listens for neutrinos from outer space.

    1
    The first station of the network on the Greenland ice. The red flags mark underground antennas powered by solar panels (dark rectangles). Credit: Cosmin Deaconu/Radio Neutrino Observatory in Greenland-U Chicago (US). The Radio Neutrino Observatory – RNO-G – will be built in Greenland to search for ultra-high energy neutrinos.

    2
    The phased array as deployed in the Askaryan Radio Array-U Wisconsin (US) at the South Pole. The main trigger of RNO-G will be an updated version of this technology.

    3
    The Aero6gen unit was temporarily put up on a 20′ tower; afterward the turbine was to be retrograded, and the tower sections were reused on the Whisper turbine at Site 2. In the foreground on the box is a 235W PV panel, not yet mounted.

    3
    The layout for each of the 37 planned clusters.

    4
    A schematic diagram of how ARA detects and analyzes neutrino interactions.

    Briefly, ARA uses radio antennas to detect nanosecond-long radio pulses from high-energy neutrinos. These are believed to be produced by ultra-high-energy cosmic rays, perhaps emanating from supermassive black holes in nearby active galactic nuclei. ARA uses the Askaryan effect, whereby charged particles can similarly emit radio or microwave radiation. By comparison, IceCube utilizes the Cherenkov effect, where charged particles moving faster than the phase velocity of light can emit light radiation. Because ARA looks for high-energy particles, a larger array is required than that of IceCube.

    6
    Schematic layout of the equipment.

    5
    The revised site layout for the Askaryan Radio Array (ARA) for the 2011-12 season.

    In Greenland’s ice sheet, a set-up unlike any other in the world will in future be listening for extremely elusive particles from space. The Radio Neutrino Observatory in Greenland-U Chicago (US) is a pioneering project that relies on a new method of detecting very high-energy cosmic neutrinos using radio antennas. The scientists involved in the project have now installed the first antenna stations in the ice at the Summit Station research facility.

    “Neutrinos are extremely elusive, ultralight elementary particles,” explains DESY physicist Anna Nelles, one of the initiators of the project. “These particles are created in vast quantities in space, especially during high-energy processes like those that take place in cosmic particle accelerators. But they are very difficult to detect because they hardly ever react with matter. From the Sun alone, some 60 billion neutrinos pass completely unnoticed through a speck on Earth the size of a fingernail – every second.”

    The ultralight elementary particles are sometimes called ghost particles because they have no trouble passing straight through walls, the Earth and even entire stars. “This property makes them interesting for astrophysicists because they can be used to look inside exploding stars or merging neutron stars, for example, from which no light can reach us,” explains Nelles, who is also a professor at Friedrich–Alexander University Erlangen–Nürnberg [Friedrich-Alexander-Universität Erlangen-Nürnberg] (DE). “Also, neutrinos can be used to track down natural cosmic particle accelerators.”

    On extremely rare occasions, however, a neutrino does in fact interact with matter when it happens to bump into an atom as it passes through – the Greenland ice sheet, for instance. Such rare collisions produce an avalanche of secondary particles, many of which are electrically charged, unlike the neutrino. This cascade of charged secondary particles emits radio waves that can be picked up by the antennas.

    7
    Summit Station is situated in the middle of the ice sheet. Credit: Cosmin Deaconu/ RNO-G.

    “The advantage of using radio waves is that ice is fairly transparent to them,” explains DESY physicist Christoph Welling, who is currently in Greenland as part of the project team. “This means we can detect radio signals over distances of several kilometres.” The greater the range, the larger the volume of ice that can be monitored, and the greater the chances of detecting one of the rare neutrino collisions. “RNO-G will be the first large-scale radio neutrino detector,” says Welling. Previous smaller-scale experiments had already shown that it is possible to use radio waves to detect cosmic particles.

    Overall, the scientists plan to install 35 antenna stations, each 1.25 kilometres apart, around Summit Station on the mighty Greenland ice sheet. Nevertheless, it could take months or even years before the observatory records a signal. “Neutrino research calls for patience,” explains Nelles. “Capturing high-energy neutrinos is an incredibly rare event. But when you do catch one, it reveals an enormous amount of information.” The researchers are also already thinking ahead to the next step, because the next radio neutrino observatory is planned literally at the other end of the world, augmenting the IceCube neutrino telescope at the South Pole.

    IceCube neutrino detector interior.


    There, an international consortium, which includes DESY, has installed some 5000 sensitive optical detectors to depths of several kilometres inside the Antarctic ice. These photomultipliers are looking out for a faint bluish flash of light, which is also produced by the energetic secondary particles from one of the rare neutrino collisions as they race through the subterranean ice. Using this technique, IceCube has already succeeded in making some spectacular observations of neutrinos arriving from the vicinity of a gigantic black hole or shattered star, for example. The visible light from the subterranean secondary particles cannot be tracked over such long distances in the ice as radio waves. However, the photomultipliers make up for this by responding to cosmic neutrinos with lower energies.

    “The higher the energy, the rarer the neutrinos become, which means you need larger detectors,” explains DESY scientist Ilse Plaisier, who also is part of the installation team in Greenland. “The two systems complement each other perfectly: IceCube’s grid of optical detectors registers neutrinos with energies of up to about a quadrillion electron volts, while the array of radio antennas will be sensitive to energies from about ten quadrillion to a hundred quintillion electron volts.” The electron volt is widely used as an energy unit in particle physics. One hundred quintillion electron volts roughly corresponds to the energy of a squash ball travelling at 130 kilometres per hour – but in the case of a neutrino, that energy is concentrated in a single subatomic particle that is a quintillion quintillion times lighter than a squash ball.

    The first stage of installing the equipment for this pioneering project is due to continue until mid-August, and carrying this out during the pandemic has been a huge logistical challenge: teams have had to spend several weeks quarantined at various locations before arriving at Summit Station, to avoid introducing the coronavirus. RNO-G will remain on the Greenland ice sheet for at least five years. The individual stations can operate autonomously, powered by solar panels, and will be connected with each other via a wireless network. Based on their operation, radio antennas are planned to be added to the IceCube neutrino detector at the South Pole as part of its Generation 2 expansion (IceCube-Gen2).

    “Detecting radio signals from high-energy neutrinos is a very promising way of significantly increasing the energy range we can access, and thus opening this new window to the cosmos even further,” says Christian Stegmann, DESY’s Director of Astroparticle Physics. “We are pursuing this path via initial test structures in Greenland, and will then go on to install radio antennas at the South Pole as part of IceCube-Gen2.”

    More than a dozen partners are involved in the pioneering project, including the University of Chicago (US), Free University of Amsterdam [Vrije Universiteit Amsterdam] (NL), Pennsylvania State University (US), the University of Wisconsin-Madison (US) and DESY.

    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 German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) 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.

     
  • richardmitnick 11:20 pm on June 3, 2021 Permalink | Reply
    Tags: "Front-row view reveals exceptional cosmic explosion", , , , DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE), GRB 190829A 29 August 2019., , X-rays from the GRB were detected by NASA's Swift satellite in Earth's orbit., Čerenkov Telescope Astronomy   

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) :Women in STEM-Sylvia Zhu and Edna Ruiz-Velasco “Front-row view reveals exceptional cosmic explosion” 

    From DESY German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE)

    Observation challenges established theory of gamma-ray bursts in the universe

    Scientists have gained the best view yet of the brightest explosions in the universe: A specialised observatory in Namibia has recorded the most energetic radiation and longest gamma-ray afterglow of a so-called gamma-ray burst (GRB) to date. The observations with the High Energy Stereoscopic System (H.E.S.S.) challenge the established idea of how gamma-rays are produced in these colossal stellar explosions which are the birth cries of black holes, as the international team reports in the journal Science.

    1
    Artist’s impression of a relativistic jet of a gamma-ray burst (GRB), breaking out of a collapsing star, and emitting very-high-energy photons. Credit: DESY, Science Communication Lab.

    “Gamma-ray bursts are bright X-ray and gamma-ray flashes observed in the sky, emitted by distant extragalactic sources,” explains DESY scientist Sylvia Zhu, one of the authors of the paper. “They are the biggest explosions in the universe and associated with the collapse of a rapidly rotating massive star to a black hole. A fraction of the liberated gravitational energy feeds the production of an ultrarelativistic blast wave. Their emission is divided into two distinct phases: an initial chaotic prompt phase lasting tens of seconds, followed by a long-lasting, smoothly fading afterglow phase.”

    On 29 August 2019 the satellites Fermi and Swift detected a gamma-ray burst in the constellation of Eridanus.

    The event, catalogued as GRB 190829A according to its date of occurrence, turned out to be one of the nearest gamma-ray bursts observed so far, with a distance of about one billion lightyears. For comparison: The typical gamma-ray burst is about 20 billion lightyears away. “We were really sitting in the front row when this gamma-ray burst happened,” explains co-author Andrew Taylor from DESY. The team caught the explosion’s afterglow immediately when it became visible to the H.E.S.S. telescopes. “We could observe the afterglow for several days and to unprecedented gamma-ray energies,” reports Taylor.

    2
    X-rays from the GRB were detected by NASA’s Swift satellite in Earth’s orbit. Very-high-energy gamma rays entered the atmosphere and initiated air showers that were detected by H.E.S.S. from the ground (artist’s impression). Credit: DESY, Science Communication Lab.

    The comparatively short distance to this gamma-ray burst allowed detailed measurements of the afterglow’s spectrum, which is the distribution of “colours” or photon energies of the radiation, in the very-high energy range. “We could determine GRB 190829A’s spectrum up to an energy of 3.3 tera-electronvolts, that’s about a trillion times as energetic as the photons of visible light,” explains co-author Edna Ruiz-Velasco from the MPG Institute for Nuclear Physics [MPG Institut für Kernphysik] (DE) in Heidelberg. “This is what’s so exceptional about this gamma-ray burst – it happened in our cosmic backyard where the very-high-energy photons were not absorbed in collisions with background light on their way to Earth, as it happens over larger distances in the cosmos.”

    The team could follow the afterglow up to three days after the initial explosion. The result came as a surprise: “Our observations revealed curious similarities between the X-ray and very-high energy gamma-ray emission of the burst’s afterglow,” reports Zhu. Established theories assume that the two emission components must be produced by separate mechanisms: the X-ray component originates from ultra-fast electrons that are deflected in the strong magnetic fields of the burst’s surroundings. This “synchrotron” process is quite similar to how particle accelerators on Earth produce bright X-rays for scientific investigations.

    However, according to existing theories it seemed very unlikely that even the most powerful explosions in the universe could accelerate electrons enough to directly produce the observed very-high-energy gamma rays via this synchrotron process. This is due to a “burn-off limit”, which is determined by the balance of acceleration and cooling of particles within an accelerator. Producing very-high-energy gamma rays through synchrotron radiation requires electrons with energies well beyond the burn-off limit. Instead, current theories assume that in a gamma-ray burst, fast electrons collide with synchrotron photons and thereby boost them to gamma-ray energies in a process dubbed synchrotron self-Compton.

    3
    Artist’s impression of very-high-energy photons from a GRB entering Earths’ atmosphere and initiating air showers that are being recorded by the H.E.S.S. telescopes. Credit: DESY, Science Communication Lab.

    But the observations of GRB 190829A’s afterglow now show that both components, X-ray and gamma ray, faded in sync. Also, the gamma-ray spectrum clearly matched an extrapolation of the X-ray spectrum. Together, these results are a strong indication that X-rays and very-high-energy gamma rays in this afterglow were produced by the same mechanism. “It is rather unexpected to observe such remarkably similar spectral and temporal characteristics in the X-ray and very-high energy gamma-ray energy bands, if the emission in these two energy ranges had different origins,” says co-author Dmitry Khangulyan from Rikkyo University [立教大学](JP) in Tokyo. This poses a challenge for the synchrotron self-Compton origin of the very-high energy gamma-ray emission.

    The far-reaching implication of this possibility highlights the need for further studies of very-high energy GRB afterglow emission. GRB 190829A is only the fourth gamma-ray burst detected at very high energies from the ground. However, the earlier detected explosions occurred much farther away in the cosmos and their afterglow could only be observed for a few hours each and not to energies above 1 tera-electronvolts (TeV). “Looking to the future, the prospects for the detection of gamma-ray bursts by next-generation instruments like the Čerenkov Telescope Array that is currently being built in the Chilean Andes and on the Canary Island of La Palma look promising,” says H.E.S.S. spokesperson Stefan Wagner from Observatory at Königstuhl[Landessternwarte Königstuhl] at Ruprecht Karl University of Heidelberg [Ruprecht-Karls-Universität Heidelberg] (DE).

    “The general abundance of gamma-ray bursts leads us to expect that regular detections in the very-high energy band will become rather common, helping us to fully understand their physics.”

    More than 230 scientists from 41 institutes in 15 countries (Namibia, South Africa, Germany, France, the UK, Ireland, Italy, Austria, the Netherlands, Poland, Sweden, Armenia, Japan, China and Australia), comprising the international H.E.S.S. collaboration, contributed to this research. H.E.S.S. is a system of five Imaging Atmospheric Čerenkov Telescopes that investigates cosmic gamma rays. The name H.E.S.S. stands for High Energy Stereoscopic System, and is also intended to pay homage to Victor Franz Hess, who received the Nobel Prize in Physics in 1936 for his discovery of cosmic radiation. H.E.S.S. is located in Namibia, near the Gamsberg mountain, an area well known for its excellent optical quality. Four H.E.S.S. telescopes went into operation in 2002/2003, the much larger fifth telescope – H.E.S.S. II – is operational since July 2012, extending the energy coverage towards lower energies and further improving sensitivity. In 2015-2016, the cameras of the first four H.E.S.S. telescopes were fully refurbished using state of the art electronics and in particular the NECTAr readout chip designed for the next big experiment in the field, the Čerenkov Telescope Array (CTA), for which the data science management centre will be hosted by DESY on its Zeuthen site.

    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 German Electron Synchrotron [Deütsches Elektronen-Synchrotron] (DE) 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.

    [/caption]

     
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