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  • 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

    DESY/FLASH

    H1 detector at DESY HERA ring

    DESY DORIS III

     
  • richardmitnick 2:21 pm on January 21, 2019 Permalink | Reply
    Tags: DESY, DESY’s next major project PETRA IV “Next Generation” will be a high-resolution X-ray microscope, , Leading X-ray and nano researchers meet in Hamburg, PETRA III   

    From DESY: “Leading X-ray and nano researchers meet in Hamburg” 

    DESY
    From DESY

    2019/01/21

    Industry fair accompanies user meetings of Hamburg research light sources

    From Wednesday on, around 1100 leading X-ray researchers and nanoscientists from 30 nations will meet in Hamburg. The participants belong to the large circle of users of the DESY X-ray light sources PETRA III and FLASH as well as the European XFEL X-ray laser opened in 2017, and they will discuss new results, investigation possibilities, and the further development of the research light sources. In recent years, the Hamburg metropolitan region has developed into a worldwide unique centre for research into the nanocosmos: With a unique combination of large-scale research facilities, new materials can be explored at the atomic level, the structure and dynamics of medically relevant biomolecules can be understood, chemical reactions can be filmed, and the interior of stars and planets can be simulated in the laboratory.

    1
    The user meetings are very popular forums for exchange and discussion on nanocosmos research. Credit: European XFEL, Axel Heimke

    “It is the largest gathering of its kind in the world. The high and still increasing number of participants from Germany and from abroad shows the extraordinary importance of photon sources in Hamburg for a broad interdisciplinary use. I am particularly pleased that many high-tech companies are taking part in these meetings,” says Prof. Helmut Dosch, Chairman of the DESY Board of Directors. “The users’ meetings are unique opportunities to celebrate the achievements, challenges, and highlights that have taken place at European XFEL over the last year, and to start new collaborations with our users and industrial partners,” adds European XFEL Managing Director Prof. Robert Feidenhans’l.

    The scientific light sources at DESY and European XFEL are used every year by more than 2500 guest researchers from all over the world, and once every year, the users gather in Hamburg.


    European XFEL campus

    In the past few years, these users’ meetings have been registering record numbers of participants. “The nanocosmos holds the keys to solving numerous current challenges, such as climate-friendly energy supply, tailor-made medicines, or new types of data storage,” emphasizes DESY Research Director for Photon Science, Prof. Edgar Weckert. “Our user community is continually growing and diversifying, and we are pleased so many will join us to discuss the world-class research going on here,” says Prof. Serguei Molodtsov, Scientific Director of European XFEL.

    The focus this year will include the first year of operation of the European XFEL and the plans to upgrade DESY’s X-ray ring PETRA III to the ultimate 3D X-ray microscope, PETRA IV.

    DESY Petra III

    Since the start of the European XFEL’s user operation in September 2017, more than 500 researchers have performed experiments at the facility’s first two experiment stations. Two more experiment stations became available for researchers at the end of 2018, and the final two stations of the facility’s initial configuration, comprising six stations, are scheduled to start operation in the first half of 2019. With them, operational capacity at the new facility will have tripled in less than two years’ time, with the range of possible experiments likewise growing. The first published results show the potential of the unique, ultrafast pulse rate of the European XFEL for investigations of atomic structure and biomolecular dynamics.

    DESY’s next major project, PETRA IV “Next Generation”, will be a high-resolution X-ray microscope, with which the inner structure of samples in their natural environment can be observed on all size scales, from millimeters to tenths of a nanometer. It will provide images of processes in the nanocosmos with several hundredfold finer details than is possible today, thus reaching the limits of what is physically possible. “The instruments at European XFEL and DESY complement each other optimally, so that together we can already offer our users a vast range of possibilities for exploring the atomic structure and dynamics of different materials at a range of time scales. PETRA IV will complete the portfolio and add even more opportunities – all together, the research done at our facilities can change the way we see the world around us,” says Feidenhans’l.

    In more than 30 plenary lectures and 18 satellite workshops, as well as on more than 350 scientific posters, the participants of this year’s meetings will exchange information on new developments for three days from Wednesday to Friday. At an accompanying industrial fair, around 80 companies will be presenting their highly specialised products for cutting-edge research.

    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 11:54 am on December 27, 2018 Permalink | Reply
    Tags: , Astroparticle physics to become research division at DESY, , , , DESY, , ,   

    From DESY: “Astroparticle physics to become research division at DESY” 

    DESY
    From DESY

    1
    Cosmic particle accelerators like blazars (artist’s impression) are typical objects for multimessenger astronomy. Credit: DESY, Science Communication Lab

    Key focus on multimessenger astronomy

    DESY is expanding its activities for the exploration of the universe. As the new year begins, the research centre, which is a member of the Helmholtz Association, is setting up a new research division for astroparticle physics. The director in charge of astroparticle physics will be Christian Stegmann, who is also the head of DESY’s Zeuthen site. This means that in future DESY will have four research divisions: Accelerators, Photon Science, Particle Physics and Astroparticle Physics.

    “Astroparticle physics has developed extremely rapidly in recent years, both at an international level and at DESY. With the establishment of the new research division, we are driving this development further forward,” explains Helmut Dosch, the chairman of DESY’s Board of Directors. “Over the coming years, DESY’s site in Zeuthen is going to be expanded to become an international centre for astroparticle physics. These steps will be a boost for astroparticle physics throughout Germany.”

    Astroparticle physics studies high-energy particles from outer space that originate in high-energy phenomena such as supernova explosions and active galactic nuclei. It aims to gain a fundamental understanding of the role of high-energy particles and processes involved in the evolution of the universe, thereby providing important foundations for the search for dark matter and physics beyond the Standard Model of particle physics. It is now possible, for the first time, to measure all the different cosmic messengers – from cosmic rays, through gamma radiation and cosmic neutrinos, to gravitational waves – and to combine this information with observations made in classical astronomy, to paint a new picture of the high-energy universe. The emerging field of such combined observations of different “messengers” is called multimessenger astronomy.

    Within astroparticle physics, DESY is currently concentrating on the study of cosmic gamma radiation and high-energy neutrinos from outer space. Neutrinos are lightweight elementary particles that can easily penetrate entire stars and therefore offer a glimpse of regions that are opaque to light and other types of electromagnetic radiation. Both gamma-ray and neutrino astronomy are exceedingly dynamic fields of research, and DESY is one of the leading institutes involved in large international observatories such as the future Cherenkov Telescope Array, CTA, and in upgrading the IceCube Neutrino Observatory at the South Pole. Theoretical astroparticle physics is responsible for the important task of interpreting the data provided by the various different cosmic messengers, and to describe how they are connected.

    Cherenkov Telescope Array, http://www.isdc.unige.ch/cta/ at Cerro Paranal, located in the Atacama Desert of northern Chile searches for cosmic rayson Cerro Paranal at 2,635 m (8,645 ft) altitude, 120 km (70 mi) south of Antofagasta; and at at the Instituto de Astrofisica de Canarias (IAC), Roque de los Muchachos Observatory in La Palma, Spain

    U Wisconsin ICECUBE neutrino detector at the South Pole

    Within the new astroparticle physics research division, a particular scientific focus lies with the multimessenger programme. Apart from the scientific activities, DESY is setting up an international graduate school for promoting young talents in multimessenger astronomy, sponsored by the Helmholtz Association, in collaboration with partners which include the Humboldt University in Berlin, the University of Potsdam and Israel’s Weizmann Institute.

    Stegmann is convinced that, “We are on the threshold of a golden age in multimessenger astronomy. And the breath-taking speed with which spectacular findings have been made in recent years means that launching the new research division of astroparticle physics is a step into the future for DESY. I am very pleased to be in charge of this very active division and to be supervising the next results as its director, results that will contribute to our understanding of the structure of matter, from the universe down to the tiniest elementary particles, and to continuing to develop science in Germany.”

    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 8:15 am on August 14, 2018 Permalink | Reply
    Tags: DESY, , PITZ accelerator-Photo Injector Test facility at DESY's Zeuthen site, Plasma-based particle acceleration   

    From DESY: “World record – Low-draft electron bunches drive high plasma wakes” 

    DESY
    From DESY

    2018/08/13

    Scientists at DESY have achieved a milestone towards the usability of novel, plasma-based particle accelerators. Using the electron beam of the PITZ accelerator, the Photo Injector Test facility at DESY’s Zeuthen site, DESY physicist Frank Stephan and his group, as part of the LAOLA collaboration, accelerated electrons in a plasma wake with an enhanced ratio between acceleration of the witness and deceleration of the driver beam. This so-called transformer ratio defines the achievable energy gain in such a plasma accelerator. Their results are now being published in the journal Physical Review Letters.

    1
    DESY – PITZ – Deutsches Elektronen-Synchrotron DESY The Photo Injector Test Facility at the DESY location in Zeuthen

    2
    The plasma cell used for the experiments. The glass tube is ten centimetres long, about seven centimetres are visible here. Credit: DESY, Gregor Loisch

    Plasma-based particle acceleration is a novel accelerator technology which utilizes the possibility to achieve accelerating field strengths in a plasma which exceed those of conventional accelerators by three orders of magnitude. In the case of the Plasma Wakefield Acceleration scheme, a pair of two electron bunches are shot into an ionized gas (plasma) where the first, highly energetic “driver”-bunch drives a plasma wake. The second, “witness” bunch, which trails the first one with about five picoseconds (millionth of a millionth second) delay, is accelerated in the plasma wake like a surfer who rides the wake of a boat.

    The electrons which drive the plasma wake are being decelerated in the process and act as the energy source for the acceleration. The ratio between acceleration and deceleration is the above-mentioned transformer ratio. A high transformer ratio corresponds to a boat, that slides lightly through the water but creates a high wake at its stern. For the electron beams that have been used in plasma wakefield experiments so far, the transformer ratio is limited to 2. The experiments at PITZ aimed at breaking this limit, which was possible by using the specially formed electron bunches that are available at PITZ. Using the flexible photocathode laser of the facility, the researchers were able to investigate plasma acceleration by asymmetric, triangularly shaped driver bunches for the first time. With this crucial improvement, a transformer ratio of 4.6 was measured, exceeding previous experiments significantly.

    3
    The simulation of the beam plasma interaction shows the driver beam electrons (red), the witness beam electrons (green) and the accelerating plasma wakefield (colored surface). Credit: DESY, Gregor Loisch

    “Application of our technique could reduce the length of a future plasma accelerator by more than half”, says Gregor Loisch, lead author of the study. “Now that we know that such high transformer ratios are generally possible, we’ll refine our methods to achieve this at higher accelerating fields.”

    Especially the high achievable accelerating field strength makes plasma acceleration one of the most promising candidates for novel particle accelerators. Increasing the field strength allows to shrink the acceleration length at constant acceleration energy, which would reduce the cost for building and operating such a future facility.

    The studies performed at PITZ, could allow to also shrink the energy of the required conventional driver beam accelerator and reduce the costs further.

    Today, only few facilities in the world are capable of producing the flexible electron beams needed for this. Other crucial assets of the research accelerator PITZ besides its bunch shaping capabilities are the various diagnostics to accurately measure the electron beams and the possibility to supply sufficient beam time for such accelerator experiments.

    In addition to increasing the relatively moderate acceleration field strength of currently 3.6 megavolts per metre (MV/m), the scientists will focus on improving the bunch shaping flexibility in further studies.

    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 9:56 am on May 28, 2018 Permalink | Reply
    Tags: CALICE collaboration, Calorimeter systems, Calorimeters measure the energy of passing particles from a collision, DESY, Hadronic calorimeter, , ,   

    From DESY: “Detector prototype sees beam” 

    DESY
    From DESY

    Optimised from top to bottom: new calorimeter produces good results in the test beam.

    1
    The calorimeter was assembled at DESY. Image: DESY

    2
    Test beam crew at CERN. Image: Jiri Kvasnicka, Prag

    Particle physics will always need calorimeters, so particle physicists are always trying to optimise, tweak and update their calorimeter systems for the best possible measurements. The CALICE collaboration plays a leading role in this, and their most recent prototype for a hadronic calorimeter has just been completed and is currently at CERN for a round of tests in the test beam.

    The project leaders are Katja Krüger and Felix Sefkow from DESY, who coordinated the development and production of all parts for the new prototype. They made sure it all came together in the detector lab at DESY and used the local expertise of many different groups to check that it worked wand set off with it to CERN. And it’s not only DESY electronics expertise that was involved: the calorimeter made the journey packaged in neat crates designed and custom-made by the DESY carpenters.

    The calorimeter prototype, whose role it is to measure the energy of passing particles from a collision, consists of 38 layers of 72 by 72 centimetres of active material. 22 000 scintillator tiles, each with its own silicon photomultiplier (SiPM), measure the passing particles, and in contrast to previous prototypes everything is included in the structure: photosensors, readout chips, LEDs for calibration, voltage adjustment, trigger, storage, amplifiers, energy and time digitisers, you name it. All of the data recorded by the detectors leaves the structure via one neat cable – just like it would have to if it were part of a complete high-energy physics particle detector where there’s no space for racks and lots of cables.

    2
    Representation of particles in the detector. No image credit.

    Coordinator Felix Sefkow explains what makes this calorimeter so special. “It’s got the 4D position information and timing of an imaging detector and it’s a calorimeter at the same time.” The new prototype is the culmination of years of developing and testing various technologies and combinations of technologies in labs and test beams to find the optimal system combinations and use the latest developments from semi-conductor industry. With its mature technology it could in principle be installed in a detector for the ILC tomorrow. So far things have gone well in the test beam that just finished after two weeks at CERN.

    Assembly of the detector had started in October last year with the participation of many groups around the world, using mass-production technologies. The scintillator tiles themselves were injection-moulded in Russia, automatically wrapped like candies in Hamburg and glued onto electronics boards by a robot in Mainz. The complex boards were assembled at DESY, using ASICs from the OMEGA group at Palaiseau, tested in Wuppertal, and SiPMs from Japan, characterised in Heidelberg.

    The DAQ was a common effort of Bristol, Prague and DESY physicists. Board production went on until January, after which they were calibrated, tested and integrated into the calorimeter structure at DESY. The Max-Planck-Group Munich contributed to mechanics and gave the software a strong boost. And before being packed up into boxes for the CERN beam time the setup already recorded its first cosmic muon events.

    Installation in CERN’s SPS beam line H2 went smoothly, the detector worked out of the box and recorded tens of millions of muon, electron and pion events. “Online data quality looks good”, summarises Krüger.

    The CALICE SiPM-on-Tile technology, developed under DESY lead, is so versatile that it will also be used in the LHC’s CMS detector for the high-luminosity upgrade and is under consideration for a future neutrino detector in the United States.

    See the full article here .


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

    Please help promote STEM in your local schools.
    stem
    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.

     
  • richardmitnick 3:42 pm on May 5, 2018 Permalink | Reply
    Tags: , , , DESY, , Freeze-framing nanosecond movements of nanoparticles, , ,   

    From DESY: “Freeze-framing nanosecond movements of nanoparticles” 

    DESY
    From DESY

    2018/05/03
    No writer credit

    New method allows to monitor fast movements at hard X-ray lasers.

    A team of scientists from DESY, the Advanced Photon Source APS and National Accelerator Laboratory SLAC, both in the USA, have developed and integrated a new method for monitoring ultrafast movements of nanoscopic systems.

    Argonne APS

    SLAC LCLS

    With the light of the X-ray laser LCLS at the research center SLAC in California, they took images of the movements of nanoparticles taking only the billionth of a second (0,000 000 001 s).

    SLAC LCLS

    In their experiments now published in the journal Nature Communications they overcame the slowness of present-day two-dimensional X-ray detectors by splitting individual laser flashes of LCLS, delaying one half of it by a nanosecond and recording a single picture of the nanoparticle with these pairs of X-ray pulses. The tunable light splitter for hard X-rays which the scientists developed for these experiments enables this new technique to monitor movements of nanometer size fluctuations down to femtoseconds and at atomic resolution. For comparison: modern synchrotron radiation light sources like PETRA III at DESY can typically measure movements on millisecond timescales.

    DESY Petra III interior

    1
    Scheme of the experiment: An autocorrelator developed at DESY splits the ultrashort X-ray laser pulses into two equal intensity pulses which arrive with a tunable delay at the sample. The speckle pattern of the sample is collected in a single exposure of the 2-D detector (picture: W. Roseker/DESY).

    he intense light flashes of X-ray lasers are coherent which means that the waves of the monochromatic laser light propagate in phase to each other. Diffracting coherent light by a sample usually results in a so-called speckle diffraction pattern showing apparently randomly ordered light spots. However, this speckle is also a map of the sample arrangement, and movements of the sample constituents result in a different speckle pattern.

    For their experiments the researchers developed a special optical setup – a so-called optical autocorrelator – capable of splitting 100 femtosecond long XFEL pulses into two sub-pulses, deviate them into separated detours and recombining their paths with a tunable time delay between zero and a few nanoseconds. These pairs of XFEL pulses hit the sample with the tuned delay, spotting the sample´s structure at the two exposure times. The sum of both speckle pictures was recorded by a two-dimensional photon detector within one exposure time. The trick: If the constituents of the sample move during the two illuminations, the speckle pattern changes, resulting in an integrated picture of less contrast at the detector. The contrast is a measure on how strong the photon intensity varies on the detector. However, the intensity and especially the intensity difference measured at the detector are very weak. In their experiments the researchers had to work with only some 1000 detected photons on the one-million-pixels size detector.

    “Such type of experiments has been done for much slower movements of nanoparticles at storage ring light sources,” explains first author Wojciech Roseker from DESY. “But now, the high coherence and intensity of the X-ray laser light at XFELs open up the opportunity to get pictures bright enough to provide reasonable information about quick movements in the nanosecond to femtosecond regime.”

    In their work the researchers around Roseker used a suspension of two nanometers size gold particles undergoing Brownian motion. The experiment was in perfect agreement with the theoretical predictions thus proving not only the performance of the autocorrelator setup but also the validity of the data analysis procedure, demonstrating the first successful experiment of this kind. One of the challenges in this experiment, carried out at the XCS experimental station at LCLS, was to autocorrelate thousands of extremely weak double shot 2D images which was achieved with the help of a newly developed maximum likelihood analysis technique.

    “This experiment paves the way to dynamics experiments of materials on atomic length and femtosecond-nanosecond timescales,” explains Gerhard Grübel, head of the DESY FS-CXS group. “Split-pulse X-ray Photon Correlation Spectroscopy (XPCS) can potentially track atomic scale fluctuations in liquid metals, multi-scale dynamics in water, heterogeneous dynamics about the glass transition, and atomic scale surface fluctuations.” Additionally, time-domain XPCS at FEL sources, especially at the European XFEL, is well suited for studying fluctuations in non-equilibrium processes that go beyond time-averaged structural descriptions.


    DESY European XFEL


    European XFEL

    This will allow the elucidation of dynamics of ultrafast magnetization processes and can address open questions concerning photo-induced phonon dynamics and phase transitions.

    See the full article here .

    Please help promote STEM in your local schools.

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    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.

     
  • richardmitnick 4:37 pm on April 6, 2018 Permalink | Reply
    Tags: , , , DESY, , , , ,   

    From DESY: “Electron beams that chop themselves” 

    DESY
    DESY

    2018/04/06

    First experimental proof of self-modulation of particle bunches.

    1
    View through the plasma cell along the flight path of the electron beam. Visible in the middle is the pink glow of the plasma. Credit: DESY, Johannes Engel.

    In a multi-national effort a team of researchers from DESY, the Lawrence Berkeley National Laboratory (LBNL) and other institutes have demonstrated a remarkable feature of self-organisation in a particle beam that can be of great use for a future generation of compact accelerators: Using the high quality electron beam at DESY’s PITZ facility, the scientists could show that long electron bunches can chop themselves into a row of shorter bunches when they fly through a cloud of electrically charged gas, called a plasma.

    At the same time the electrons’ energies were seen to be modulated along each bunch. These results are the experimental proof of a novel plasma acceleration concept pursued by the AWAKE (Advanced Wakefield Experiment) collaboration at the European particle physics lab CERN in Geneva. The team led by DESY scientist Matthias Groß presents its findings in the journal Physical Review Letters.

    Particle accelerators at the energy frontier like the Large Hadron Collider (LHC) at CERN are extremely costly to build and operate.

    LHC

    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Nevertheless there is strong interest to increase available beam energies even further to refine the standard model of particle physics and discover physics beyond. Plasma wakefield accelerators could be the answer to this problem. Today’s bulky structures could be replaced with millimetre-sized plasmas enabling several orders of magnitude stronger acceleration.

    To accelerate an electron bunch in this way the plasma electrons are separated from the plasma molecules, forming a so-called plasma wakefield that creates an immense accelerating field. The separation of electrons and molecules in the plasma can be achieved through a high-energy bunch of charged particles. Using proton bunches is very attractive since sufficient energy can be stored in a proton beam to drive a plasma accelerator and generate electron bunches with energies in the LHC regime of tera-electronvolts (TeV) in a single stage. The AWAKE experiment is hosted by CERN to investigate this promising scheme. However, proton bunches as they are generated in today’s accelerators are much too long to be useful in plasma accelerators. Therefore, the generation of suitable proton bunches from a conventional accelerator is a key issue for the AWAKE setup.

    CERN AWAKE

    CERN AWAKE

    2
    A self-modulated electron bunch. Credit: DESY

    This task can be accomplished by utilising the so-called self-modulation instability. In this case a plasma wave is initiated at or near the front of the bunch and the resulting electric fields lead to the desired re-organisation of the particle bunches in the beam. This self-modulation effect was described in theory and simulation, but so far only indirect indications were observed in experiment. This is where the unique capabilities of the PITZ facility comes into play, explains group leader Frank Stephan: “The combination of a flexible photocathode laser, high electron beam quality and excellent diagnostics made it possible to demonstrate this effect unambiguously for the first time.” The measurements showed that an incident long electron bunch split itself into three smaller bunches.

    1
    DESY PITZ

    ”The breakthrough results described in our manuscript can be scaled directly to the proton regime and thus open the path to validate the self-modulation scheme towards the next-generation of high-energy physics accelerators at CERN,” emphasises main author Matthias Groß. “Our positive results show that the self-modulation can be practically used in experiments and that unwanted effects like beam hosing, which tend to destroy particle bunches, can be kept under control. This experimental data has been eagerly anticipated in the plasma wakefield accelerator community, especially by the AWAKE collaboration, for several years. The presented achievement is a further example where a plasma wakefield theory based prediction is directly validated in experiment. And looking ahead, our special cross shaped plasma cell which was utilized to gain these results may be of great interest to other groups working on beam-driven plasma wakefield acceleration as well.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 2:58 pm on December 8, 2017 Permalink | Reply
    Tags: DESY, Novel Lenses Enable X-ray Microscopy With Record Resolution, The new lenses consist of over 10 000 alternating layers of a new material combination, These lenses consist of alternating layers of two different materials with nanometre thickness   

    From DESY: “Novel Lenses Enable X-ray Microscopy With Record Resolution” 

    DESY
    DESY

    2017/12/07
    No writer credit

    DESY team generates X-ray focus below 10 nanometres diameter.

    1
    The silica shell of the diatom Actinoptychus senarius, measuring only 0.1 mm across, is revealed in fine detail in this X-ray hologram recorded at 5000-fold magnification with the new lenses. The lenses focused an X-ray beam to a spot of approximately eight nanometres diameter – smaller than a single virus – which then expanded to illuminate the diatom and form the hologram. Credit: DESY/AWI, Andrew Morgan/Saša Bajt/Henry Chapman/Christian Hamm

    Scientists at DESY have developed novel lenses that enable X-ray microscopy with record resolution in the nanometre regime. Using new materials, the research team led by DESY scientist Saša Bajt from the Center for Free-Electron Laser Science (CFEL) has perfected the design of specialised X-ray optics and achieved a focus spot size with a diameter of less than ten nanometres.

    3
    Center for Free-Electron Laser Science (CFEL)

    A nanometre is a millionths of a millimetre and is smaller than most virus particles. The researchers report their work in the journal Light: Science and Applications . They successfully used their lenses to image samples of marine plankton.

    Modern particle accelerators provide ultra-bright and high-quality X-ray beams. The short wavelength and the penetrating nature of X-rays are ideal for the microscopic investigation of complex materials. However, taking full advantage of these properties requires highly efficient and almost perfect optics in the X-ray regime. Despite extensive efforts worldwide this turned out to be more difficult than expected, and achieving an X-ray microscope that can resolve features smaller than 10 nm is still a big challenge.

    Due to their unique properties X-rays cannot be focused as easily as visible light. One way is to use specialised X-ray optics called multilayer Laue lenses (MLLs). These lenses consist of alternating layers of two different materials with nanometre thickness. They are prepared with a coating process called sputter deposition. In contrast to conventional optics, MLLs do not refract light but work by diffracting the incident X-rays in a way that concentrates the beam on a small spot. To achieve this, the layer thickness of the materials has to be precisely controlled. The layers must gradually change in thickness and orientation throughout the lens. The focus size is proportional to the smallest layer thickness in the MLL structure.

    To meet the required precision, Bajt’s team combined a novel fabrication process with detailed understanding of the material properties, which often vary with layer thickness. The new lenses consist of over 10 000 alternating layers of a new material combination, tungsten carbide and silicon carbide. “The selection of the right material pair was critical for the success,” emphasises Bajt. “It does not exclude other material combinations but it is definitely the best we know now.”

    To focus an X-ray beam in the vertical and horizontal directions it has to pass through two perpendicularly oriented lenses. By using this set-up, a spot size of 8.4 nanometres by 6.8 nanometres was measured at the Hard X-ray Nanoprobe experimental station at the National Synchrotron Light Source NSLS II at Brookhaven National Laboratory in the U.S.


    BNL NSLS II

    The focus size is what sets the resolution of the X-ray microscope. The resolution of the new lenses is about five times better than achievable with typical state-of-the-art lenses.

    2
    For imaging investigations, two perpendicularly oriented lenses focus the X-ray beam into a small spot. The object under investigation (not shown here) can then be placed into the optical path and its image recorded by the detector. Credit: DESY, Andrew Morgan/Saša Bajt

    “We produced the world’s smallest X-ray focus using high efficiency lenses,” says Bajt. Due to their penetrating nature, X-rays would usually pass straight through the lens materials. Such rays obviously do not contribute to the focus, and thus a long-term goal has been to produce lens structures that enhance the interaction with X-rays, to direct a high fraction into the focus. The new lenses have an efficiency of more than 80 per cent. This high efficiency is achieved with the layered structures that make up the lens and which act like an artificial crystal to diffract X-rays in a controlled way.

    The high efficiency achieved here demonstrates the very high level of control in the production of the necessary nanometre structures. This accuracy allows projection imaging over a large range of magnifications as demonstrated by tests of the novel lenses. At beamline P11 of DESY’s X-ray source PETRA III the scientists produced high-resolution holograms of Acantharea, single-celled Radiolaria belonging to marine plankton and the only organisms known to form skeletons from the mineral strontium sulfate (SrSO4) or celestite.

    DESY Petra III

    Bajt’s team has also used the new lenses to image the biomineralized shells of marine planktonic diatoms. These single-celled organisms have intricate shells, which are highly complex stable but also lightweight constructions. They consist of nanostructured silica, which was observed in two dimensional analyses with electron microscopes before. Most likely because of this structuring, the strength of the silica is exceptionally high – ten times higher than that of construction steel – although it is produced under low temperature and pressure conditions.

    “We hope that the novel X-ray optics will soon make it possible to image these nanostructures in 3D. This will enable us to model and understand the high mechanical performance of these shells and help us to develop new, environmentally friendly and high performance materials,” says Christian Hamm from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), who provided the samples and is a co-author of this study.

    The new lenses can be used in a wide range of applications including nano-resolution imaging and spectroscopy. “These MLLs open up new and exciting opportunities in X-ray science. They can be designed for different energies and used with coherent sources, such as X-ray free-electron lasers,” says Bajt. “This great achievement would not have been possible without a wonderful team with expertise in X-ray optics and theory, nanofabrication, material science, data processing and instrumentation. Since we now know how to optimise the lens design, our work paves the way to ultimately reach the goal of one nanometre resolution in X-ray microscopy.”

    Scientists from DESY, the University of Hamburg, the National Science Foundation BioXFEL Science and Technology Center in the U.S., Arizona State University in the U.S., the University of Bialystok in Poland, Brookhaven National Laboratory in the U.S., and Alfred Wegener Institute in Germany were involved in this study. CFEL is a cooperation of DESY, the University of Hamburg and the German Max Planck Society.

    Reference:
    X-ray focusing with efficient high-NA multilayer Laue lenses; Saša Bajt et al.;Light: Science and Applications (accepted article preview; 25,6MB, slow server!)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 12:01 pm on June 19, 2017 Permalink | Reply
    Tags: , , DESY, , First atomic structure of an intact virus deciphered with an X-ray laser, ,   

    From DESY: “First atomic structure of an intact virus deciphered with an X-ray laser” 

    DESY
    DESY

    2017/06/19

    Groundbreaking experimental method will speed up protein analysis substantially.

    1
    Surface structure of the bovine enterovirus 2, the three virus proteins are colour coded. Credit: Jingshan Ren, University of Oxford

    An international team of scientists has for the first time used an X-ray free-electron laser to unravel the structure of an intact virus particle on the atomic level. The method used dramatically reduces the amount of virus material required, while also allowing the investigations to be carried out several times faster than before. This opens up entirely new research opportunities, as the research team lead by DESY scientist Alke Meents reports in the journal Nature Methods.

    In the field known as structural biology, scientists examine the three-dimensional structure of biological molecules in order to work out how they function. This knowledge enhances our understanding of the fundamental biological processes taking place inside organisms, such as the way in which substances are transported in and out of a cell, and can also be used to develop new drugs.

    “Knowing the three-dimensional structure of a molecule like a protein gives great insight into its biological behaviour,” explains co-author David Stuart, Director of Life Sciences at the synchrotron facility Diamond Light Source in the UK and a professor at the University of Oxford. “One example is how understanding the structure of a protein that a virus uses to ‘hook’ onto a cell could mean that we’re able to design a defence for the cell to make the virus incapable of attacking it.”

    X-ray crystallography is by far the most prolific tool used by structural biologists and has already revealed the structures of thousands of biological molecules. Tiny crystals of the protein of interest are grown, and then illuminated using high-energy X-rays. The crystals diffract the X-rays in characteristic ways so that the resulting diffraction patterns can be used to deduce the spatial structure of the crystal – and hence of its components – on the atomic scale. However, protein crystals are nowhere near as stable and sturdy as salt crystals, for example. They are difficult to grow, often remaining tiny, and are easily damaged by the X-rays.

    “X-ray lasers have opened up a new path to protein crystallography, because their extremely intense pulses can be used to analyse even extremely tiny crystals that would not produce a sufficiently bright diffraction image using other X-ray sources,” adds co-author Armin Wagner from Diamond Light Source. However, each of these microcrystals can only produce a single diffraction image before it evaporates as a result of the X-ray pulse. To perform the structural analysis, though, hundreds or even thousands of diffraction images are needed. In such experiments, scientists therefore inject a fine liquid jet of protein crystals through a pulsed X-ray laser, which releases a rapid sequence of extremely short bursts. Each time an X-ray pulse happens to strike a microcrystal, a diffraction image is produced and recorded.

    This method is very successful and has already been used to determine the structure of more than 80 biomolecules. However, most of the sample material is wasted. “The hit rate is typically less than two per cent of pulses, so most of the precious microcrystals end up unused in the collection container,” says Meents, who is based at the Center for Free-Electron Laser Science (CFEL) in Hamburg, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. The standard method therefore typically requires several hours of beamtime and significant amounts of sample material.

    3
    Micrograph of the microstructured chip, loaded with crystals for the investigation. Each square is a tiny crystal. Credit: Philip Roedig, DESY

    n order to use the limited beamtime and the precious sample material more efficiently, the team developed a new method. The scientists use a micro-patterned chip containing thousands of tiny pores to hold the protein crystals. The X-ray laser then scans the chip line by line, and ideally this allows a diffraction image to be recorded for each pulse of the laser.

    The research team tested its method on two different virus samples using the LCLS X-ray laser at the SLAC National Accelerator Laboratory in the US, which produces 120 pulses per second.

    SLAC/LCLS

    They loaded their sample holder with a small amount of microcrystals of the bovine enterovirus 2 (BEV2), a virus that can cause miscarriages, stillbirths, and infertility in cattle, and which is very difficult to crystallise.

    In this experiment, the scientists achieved a hit rate – where the X-ray laser successfully targeted the crystal – of up to nine per cent. Within just 14 minutes they had collected enough data to determine the correct structure of the virus – which was already known from experiments at other X-ray light sources – down to a scale of 0.23 nanometres (millionths of a millimetre).

    “To the best of our knowledge, this is the first time the atomic structure of an intact virus particle has been determined using an X-ray laser,” Meents points out. “Whereas earlier methods at other X-ray light sources required crystals with a total volume of 3.5 nanolitres, we managed using crystals that were more than ten times smaller, having a total volume of just 0.23 nanolitres.”

    This experiment was conducted at room temperature. While cooling the protein crystals would protect them to some extent from radiation damage, this is not generally feasible when working with extremely sensitive virus crystals. Crystals of isolated virus proteins can, however, be frozen, and in a second test, the researchers studied the viral protein polyhedrin that makes up a viral occlusion body for up to several thousands of virus particles of certain species. The virus particles use these containers to protect themselves against environmental influences and are therefore able to remain intact for much longer times.

    4
    Schematic of the experimental set-up: The chip loaded with nanocrystals is scanned by the fine X-ray beam (green) pore by pore. Ideally, each crystal produces a distinctive diffraction pattern. Credit: Philip Roedig, DESY

    For the second test, the scientist loaded their chip with polyhedrin crystals and examined them using the X-ray laser while keeping the chip at temperatures below minus 180 degrees Celsius. Here, the scientists achieved a hit rate of up to 90 per cent. In just ten minutes they had recorded more than enough diffraction images to determine the protein structure to within 0.24 nanometres. “For the structure of polyhedrin, we only had to scan a single chip which was loaded with four micrograms of protein crystals; that is orders of magnitude less than the amount that would normally be needed,” explains Meents.

    “Our approach not only reduces the data collection time and the quantity of the sample needed, it also opens up the opportunity of analysing entire viruses using X-ray lasers,” Meents sums up. The scientists now want to increase the capacity of their chip by a factor of ten, from 22,500 to some 200,000 micropores, and further increase the scanning speed to up to one thousand samples per second. This would better exploit the potential of the new X-ray free-electron laser European XFEL, which is just going into operation in the Hamburg region and which will be able to produce up to 27,000 pulses per second.

    European XFEL

    Furthermore, the next generation of chips will only expose those micropores that are currently being analysed, to prevent the remaining crystals from being damaged by scattered radiation from the X-ray laser.

    Researchers from the University of Oxford, the University of Eastern Finland, the Swiss Paul Scherrer Institute, the Lawrence Berkeley National Laboratory in the US and SLAC were also involved in the research. Diamond scientists have collaborated with the team at DESY, with much of the development and testing of the micro-patterned chip being done on Diamond’s I02 and I24 beamlines.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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.

     
  • richardmitnick 1:44 pm on May 31, 2017 Permalink | Reply
    Tags: , , DESY, ,   

    From SLAC: “The World’s Most Powerful X-ray Laser Beam Creates ‘Molecular Black Hole’” 


    SLAC Lab

    May 31, 2017
    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    When the X-rays blast electrons out of one atom, stripping it from the inside out, it steals more from its neighbors – a new insight that could help advance high-res imaging of whole viruses, bacteria and complex materials.

    1
    In this illustration, an ultra-intense X-ray laser pulse from SLAC’s Linac Coherent Light Source knocks so many electrons out of a molecule’s iodine atom (right) that the iodine starts pulling in electrons from the rest of the molecule (lower left), like an electromagnetic version of a black hole. Many of the stolen electrons are also knocked out by the laser pulse; then the molecule explodes. (DESY/Science Communication Lab)

    When scientists at the Department of Energy’s SLAC National Accelerator Laboratory focused the full intensity of the world’s most powerful X-ray laser on a small molecule, they got a surprise: A single laser pulse stripped all but a few electrons out of the molecule’s biggest atom from the inside out, leaving a void that started pulling in electrons from the rest of the molecule, like a black hole gobbling a spiraling disk of matter.

    Within 30 femtoseconds – millionths of a billionth of a second – the molecule lost more than 50 electrons, far more than scientists anticipated based on earlier experiments using less intense beams or isolated atoms. Then it blew up.

    The results, published today in Nature, give scientists fundamental insights they need to better plan and interpret experiments using the most intense and energetic X-ray pulses from SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser.

    SLAC/LCLS

    Experiments that require these ultrahigh intensities include attempts to image individual biological objects, such as viruses and bacteria, at high resolution. They are also used to study the behavior of matter under extreme conditions, and to better understand charge dynamics in complex molecules for advanced technological applications.

    “For any type of experiment you do that focuses intense X-rays on a sample, you want to understand how it reacts to the X-rays,” said Daniel Rolles of Kansas State University. “This paper shows that we can understand and model the radiation damage in small molecules, so now we can predict what damage we will get in other systems.”

    Like Focusing the Sun Onto a Thumbnail

    The experiment, led by Rolles and Artem Rudenko of Kansas State, took place at LCLS’s Coherent X-ray Imaging instrument (CXI). It delivers X-rays with the highest possible energies achievable at LCLS, known as hard X-rays, and records data from samples in the instant before the laser pulse destroys them.

    How intense are those X-ray pulses?

    “They are about a hundred times more intense than what you would get if you focused all the sunlight that hits the Earth’s surface onto a thumbnail,” said LCLS staff scientist and co-author Sebastien Boutet.

    For this study, researchers used special mirrors to focus the X-ray beam into a spot just over 100 nanometers in diameter – about a hundredth the size of the one used in most CXI experiments, and a thousand times smaller than the width of a human hair. They looked at three types of samples: individual xenon atoms, which have 54 electrons each, and two types of molecules that each contain a single iodine atom, which has 53 electrons.

    Heavy atoms around this size are important in biochemical reactions, and researchers sometimes add them to biological samples to enhance contrast for imaging and crystallography applications. But until now, no one had investigated how the ultra-intense CXI beam affects molecules with atoms this heavy.

    X-rays Trigger Electron Cascades

    The team tuned the energy of the CXI pulses so they would selectively strip the innermost electrons from the xenon or iodine atoms, creating “hollow atoms.” Based on earlier studies with less energetic X-rays, they thought cascades of electrons from the outer parts of the atom would drop down to fill the vacancies, only to be kicked out themselves by subsequent X-rays. That would leave just a few of the most tightly bound electrons. And, in fact, that’s what happened in both the freestanding xenon atoms and the iodine atoms in the molecules.

    But in the molecules, the process didn’t stop there. The iodine atom, which had a strong positive charge after losing most of its electrons, continued to suck in electrons from neighboring carbon and hydrogen atoms, and those electrons were also ejected, one by one.

    Rather than losing 47 electrons, as would be the case for an isolated iodine atom, the iodine in the smaller molecule lost 54, including the ones it grabbed from its neighbors – a level of damage and disruption that’s not only higher than would normally be expected, but significantly different in nature.

    Results Feed Into Theory to Improve Experiments

    “We think the effect was even more important in the larger molecule than in the smaller one, but we don’t know how to quantify it yet,” Rudenko said. “We estimate that more than 60 electrons were kicked out, but we don’t actually know where it stopped because we could not detect all the fragments that flew off as the molecule fell apart to see how many electrons were missing. This is one of the open questions we need to study.”

    For the data analyzed to date, the theoretical model provided excellent agreement with the observed behavior, providing confidence that more complex systems can now be studied, said LCLS Director Mike Dunne. “This has important benefits for scientists wishing to achieve the highest-resolution images of biological molecules to inform the development of better pharmaceuticals, for example,” he said. “These experiments will also guide the development of a next-generation instrument for the LCLS-II upgrade project, which will provide a major leap in capability due to the increase in repetition rate from 120 pulses per second to 1 million.”

    SLAC LCLS-II

    The theory work for the study was led by Robin Santra of the Center for Free-Electron Laser Science at DESY and the University of Hamburg in Germany. Other research institutions contributing to the study were Tohoku University in Japan; Max Planck Institute for Nuclear Physics, Max Planck Institute for Medical Research, Hamburg Center for Ultrafast Imaging and the National Metrology Institute (PTB) in Germany; the University of Science and Technology in Beijing; Aarhus University in Denmark; Sorbonne University in France; the DOE’s Argonne National Laboratory and Brookhaven National Laboratory; the University of Chicago; and Northwestern University. Funding for the research came from the DOE Office of Science and from the German Research Foundation (DFG).

    See the full article here .

    Please help promote STEM in your local schools.

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    SLAC Campus
    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.
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