Proton Beams:

Discussion in 'General Science & Technology' started by paddoboy, Sep 30, 2016.

  1. paddoboy Valued Senior Member

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    Researchers generate proton beams using a combination of nanoparticles and laser light
    September 30, 2016

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    The Texas Petawatt laser pulse (red) is focused onto a levitating microsphere target. The immense laser-intensity causes the fierce explosion of the microsphere, thereby generating potentially useful energetic ions from an ultra-small source (blue). Credit: Tobias Ostermayr
    Light, when strongly concentrated, is enormously powerful. Now, a team of physicists led by Professor Jörg Schreiber from the Institute of Experimental Physics – Medical Physics, which is part of the Munich-Centre for Advanced Photonics (MAP), a Cluster of Excellence at LMU Munich, has used this energy source with explosive effect. The researchers focus high-power laser light onto beads of plastic just a few micrometers in size. The concentrated energy blows the nanoparticles apart, releasing radiation made up of positively charged atoms (protons). Such proton beams could be used in future for treating tumors, and in advanced imaging techniques. Their findings appear in the journal Physical Review E.

    At Texas Petawatt Lasers in Austin, Texas, the LMU physicists concentrated laser light so strongly on plastic nanobeads that these essentially exploded. In the experiment, approximately one quadrillion billion photons (3 times 1020 photons) were focused onto microspheres of about 500 nanometers in diameter. Each bead consists of about 50 billion carbon and hydrogen atoms and is held in suspension by the electromagnetic fields of a so-called "Paul trap", where the laser beam can irradiate them.



    Read more at: http://phys.org/news/2016-09-proton-combination-nanoparticles-laser.html#jCp
     
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  3. paddoboy Valued Senior Member

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    http://journals.aps.org/pre/abstract/10.1103/PhysRevE.94.033208

    Proton acceleration by irradiation of isolated spheres with an intense laser pulse:

    ABSTRACT
    We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2–3×1020Wcm−2. With a laser focal spot size of 10μm full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3μm. Maximum proton energies of ∼25 MeV are achieved for targets matching the focal spot size of 10μm in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.

     
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  5. timojin Valued Senior Member

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    Did the beam crossed the diameter if the sphere ?
    How was the beam formed , were not the proton scattered ?
     
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  7. paddoboy Valued Senior Member

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    The researchers focus high-power laser light onto beads of plastic just a few micrometers in size. The concentrated energy blows the nanoparticles apart, releasing radiation made up of positively charged atoms (protons). Such proton beams could be used in future for treating tumors, and in advanced imaging techniques. Their findings appear in the journal Physical Review E.


    At Texas Petawatt Lasers in Austin, Texas, the LMU physicists concentrated laser light so strongly on plastic nanobeads that these essentially exploded. In the experiment, approximately one quadrillion billion photons (3 times 1020 photons) were focused onto microspheres of about 500 nanometers in diameter. Each bead consists of about 50 billion carbon and hydrogen atoms and is held in suspension by the electromagnetic fields of a so-called "Paul trap", where the laser beam can irradiate them.

    Read more at: http://phys.org/news/2016-09-proton-combination-nanoparticles-laser.html#jCp
     

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