1 Electron Accelerators and Applications
1G Other Electron Accelerators
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MO3A03 Spaceborne Electron Accelerators 32
 
  • J.W. Lewellen, C.E. Buechler, G.E. Dale, N.A. Moody, D.C. Nguyen
    LANL, Los Alamos, New Mexico, USA
 
  High-power electron beam generators in space will enable the studies of solar and space physics, specifically the interrogation of magnetic connection between the magnetosphere and ionosphere. This study plans to map the magnetic connection between the magnetosphere and ionosphere, using a satellite equipped with an electron beam accelerator that can create a spot in the ionosphere, observable by optical and radar detectors on the ground. To date, a number of spacecraft carrying low-power, <50-keV DC electron beam sources have been launched to study the upper ionosphere. The overall instrument weight will likely be dominated by the weight of the energy storage, the RF power amplifiers and the accelerator structure. We present the notional concept of a quasi-CW, C-band electron accelerator with 1-MeV beam energy, 10-mA beam current, and requiring 40 kW of prime power during operation. Our novel accelerator concept includes the following features: individually powered cavities driven by 6-GHz high-electron mobility transistors (HEMT), passively cooled accelerator structures with heat pipe technology, and active frequency control for operating over a range of temperatures.  
slides icon Slides MO3A03 [3.191 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-MO3A03  
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TH3A01 Making Molecular Movie with MeV Electrons 725
 
  • X. Shen, X.J. Wang
    SLAC, Menlo Park, California, USA
 
  SLAC launched the Ultrafast Electron Diffraction and Imaging (UED&UEM) initiative with the objective of developing the world leading ultrafast electron scattering instrumentation, complementary to the X-ray Free Electron Laser - Linac Coherent Light Source (LCLS). SLAC has developed a UED setup at the Accelerator Structure Test Area (ASTA), with the goal of providing MeV, 100-femtosecond-scale electron pulses to support an ultrafast science program [1]. The first UED ultrafast science experiment published in Nano Letters, where large amplitude wrinkles of monolayer MoS2 generated by the light pulse' more than 15 percent of the layer's thickness, was observed. This is the first time anyone has visualized these ultrafast atomic motions. Ultrafast MeV electrons also made it possible the direct measurement of phonon occupations as energy is transferred from electrons into the lattice in laser-heated gold (APL). The rotational wavepacket dynamics of laser-aligned nitrogen molecules were captured in gas-phase electron diffraction experiment using MeV electrons. We achieved an unprecedented combination of 100-fs (rms) temporal resolution and sub-Angstrom (0.76 Å) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule(Nature Communications).
[1] S. Weathersby, et al., Rev. Sci. Instrum. 86, 073702 (2015).
 
slides icon Slides TH3A01 [6.518 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-TH3A01  
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THPLR012 Beam-Loading Compensation of a Multi-Bunch Electron Beam by Using RF Amplitude Modulation in Laser Undulator Compact X-Ray Source (LUCX) 867
 
  • M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
  • K. Sakaue
    Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
  • M. Washio
    Waseda University, Tokyo, Japan
 
  Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source via laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. In here, a multi-bunch electron beam is generated by a 3.6cell photo-cathode RF-gun and accelerated to 18-24MeV by a 12cell booster. And then 6-10 keV X-rays are generated by LCS between the beam and a laser pulse stored in a 4-mirror planar optical cavity. Our aim is to take a phase contrast image with Talbot interferometer within a few minutes at present. The target flux of X-ray is 1.7x107 photons/pulse with 10% bandwidth. For an electron beam, the target of the intensity is 500nC/pulse with 1000 bunches at 30 MeV. Presently, we have achieved the generation of 24MeV beam with total charge of 600nC in 1000bunches. The energy difference is within 1.3% peak to peak. The beam-loading is compensated by delta T method and amplitude modulation(AM) of the RF pulse*. However there is the energy difference at the RF-gun. It is assumed that this causes the reduction of the X-ray flux due to change of the focused beam size. To reduce the energy difference, AM is also applied to the RF pulse for the gun. We will show the results of the beam-loading compensation and the generation of X-rays.
* Y. Yokoyama et al. , Proceedings IPAC2011, TUPC059 (2011).
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR012  
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THPLR013 LEETCHI: The High Current Electron Source for the CLIC Drive Beam Injector 870
 
  • K. Pepitone, S. Döbert
    CERN, Geneva, Switzerland
  • B. Cadilhon, B. Cassany, J. Gardelle
    CEA, LE BARP cedex, France
 
  LEETCHI is a source which will produce 140 keV, 5 A, 140 μs electron beams at a repetition rate of 50 Hz. The shot to shot and flat top current stability of this drive beam injector for CLIC has to be better than 0.1% and a geometrical emittance of 14 mm mrad is expected. The development of a high voltage modulator, to achieve those requirements, is ongoing. A small test stand has been built which allows to diagnose and dump the beam produced by the thermionic cathode. The thermionic cathode is equipped with a grid which will allow us to control the current and eventually to have a feedback on the flattop shape. The beam dump, made of graphite, has been designed using two different codes, the Monte Carlo code GEANT4 to simulate the energy deposition and ANSYS used to simulate the thermal resistance of the graphite due to the long pulse duration. The geometry has been optimized with the ray tracing code EGUN and the 2D PIC-code MAGIC. All these simulations allowed us to optimize the geometry of the gun and to develop diagnostics which must survive to the heat deposition. Finally, the first electrical measurements of the beam will be presented.  
poster icon Poster THPLR013 [19.847 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR013  
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THPLR014 Laser-Driven Dielectric Nano-Beam Accelerator for Radiation Biology Researches 873
 
  • K. Koyama, M. Yoshida
    KEK, Ibaraki, Japan
  • Z. Chen, H. Okamoto
    The University of Tokyo, Tokyo, Japan
  • M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
 
  Funding: This work was partly supported by JSPS KAKENHI (B)(Grant-in-Aid for Scientific Research) Grant Number 15H03595.
Since a laser-driven dielectric accelerator (LDA) is most likely to deliver a nano-beam with a small scale device, a combination of the LDA and a biological cell observation device such as a fluorescence microscope seems to be a powerful tool for radiation biology researches. The LDA consists of single or a pair of binary-blazed transmission grating. In case of normal incidence, a grating constant must be the same with a laser wavelength to synchronize with the electron and an acceleration field. Although demonstration experiments have been published from SLAC and MPQ, there are many problems to be solved, especially in the non-relativistic energy region. A crucial problem is to make it clear whether electrons are accelerated with negligibly small wiggling or lateral shift. We are simulating at various conditions with the aid of CST-code. We also analyze an oblique incidence (OI) scheme for the efficient acceleration of slow electron. The OI-scheme enables to use the grating of larger grating constant. Adoption of the large grating constant makes it easy to fabricate the grating. Besides analytical works, we are making gratings and developing an Yb-doped fiber laser for the acceleration experiment. Gratings of two different materials, a glass silica and crystal silica, were fabricated by the e-beam lithography technique.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2016-THPLR014  
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