| Paper |
Title |
Other Keywords |
Page |
| MOP026 |
Positron Source from X-rays Emitted by Plasma Betatron Motion
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positron, electron, plasma, ion |
94 |
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- D. K. Johnson, C. E. Clayton, C. Huang, C. Joshi, W. Lu, K. A. Marsh, W. B. Mori, M. Zhou
UCLA, Los Angeles, California
- C. D. Barnes, I. Blumenfeld, F.-J. Decker, P. Emma, M. J. Hogan, R. Ischebeck, R. H. Iverson, N. A. Kirby, P. Krejcik, C. L. O'Connell, R. Siemann, D. R. Walz
SLAC, Menlo Park, California
- S. Deng, T. C. Katsouleas, P. Muggli, E. Oz
USC, Los Angeles, California
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A new method for generating positrons has been proposed that uses betatron X-rays emitted by an electron beam in a high-K plasma wiggler. The plasma wiggler is an ion column produced by the head of the beam when the peak beam density exceeds the plasma density. The radial electric field of the beam blows out the plasma electrons transversely, creating an ion column. The focusing electric field of the ion column causes the beam electrons to execute betatron oscillations about the ion column axis. At the proper plasma density, this leads to synchrotron radiation in the 1-50 MeV range. These photons strike a thin (.5Xo), high-Z target and create electron-positron pairs. A computational model was written and matched with experimental results taken at the Stanford Linear Accelerator Center. This model was then used to design a more efficient positron source, giving positron yields of 0.44 positrons/electron, a number that is close to the target goal of 1-2 positrons/electron for future positron sources.
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| TUP014 |
Electron Signal Detection for the Beam-Finder Wire of the Linac Coherent Light Source Undulator
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electron, undulator, scattering, simulation |
274 |
| |
- J. Wu, P. Emma
SLAC, Menlo Park, California
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The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) based on the final kilometer of the Stanford Linear Accelerator. The tight tolerances for positioning the electron beam close to the undulator axis calls for the introduction of Beam Finder Wire (BFW) device. A BFW device close to the upstream end of the undulator segment and a quadrupole close to the down stream end of the undulator segment will allow a beam-based undulator segment alignment. Based on the scattering of the electrons on the BFW, we can detect the electron signal in the main dump bends after the undulator to find the beam position. We propose to use a threshold Cherenkov counter for this purpose. According to the signal strength at such a Cherenkov counter, we then suggest choice of material and size for such a BFW device in the undulator.
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| TUP044 |
Shunt Impedance Measurement of the APS BBC Gun
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impedance, cathode, gun, electron |
346 |
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- Y.-E. S. Sun, J. W. Lewellen
ANL, Argonne, Illinois
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The Advanced Photon Source (APS) ballistic bunch compression (BBC) injector is presently in use as a beam source for a number of experiments, including THz generation, beam position monitor testing for the Linac Coherent Light Source (LCLS), novel cathode testing, and radiation therapy source development. The APS BBC gun uses three independently powered and phased rf cavities, one cathode cell and two full cells, to provide beam energies from 2 – 10 MeV with variable energy spread, energy chirp, and, to an extent, bunch duration. The shunt impedance of an rf accelerator determines how effectively the accelerator can convert supplied rf power to accelerating gradient. The calculation of the shunt impedance can be complicated if the beam energy changes substantially during its transit through a cavity, such as in a cathode cell. We present the results of direct measurements of the shunt impedance of the APS BBC gun on an individual cavity basis, including the cathode cell, as well as report on achieved gradients. We also present a comparison of the measured shunt impedance with theoretical values calculated from the rf models of the cavities.
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| TH2004 |
Nuclear Photo-Science and Applications with Thomson-Radiated Extreme X-Ray (T-REX) Sources
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laser, electron, scattering, brightness |
546 |
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- C. P.J. Barty, R. Beach, D. J. Gibson, C. Hagmann, F. V. Hartemann, E. P. Hartouni, J. Hernandez, M. Johnson, I. Jovanovic, J. Klay, D. P. McNabb, R. Norman, M. Shverdin, C. Siders, R. Soltz, P. O. Stoutland, A. M. Tremaine
LLNL, Livermore, California
- J. B. Rosenzweig
UCLA, Los Angeles, California
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The Thomson scattering of picosecond and femtosecond duration laser pulses off of low emittance electron beams is an effective method of producing mono-chromatic, MeV-range gamma-rays with unprecedented peak brightness. With peak brightness at 1 MeV > 15 orders of magnitude beyond 3rd generation synchrotrons, these sources open the possibility for a host of new nuclear applications based on photons. In this presentation an overview of the requisite photo-gun, short pulse laser and linear accelerator technologies required for production of high brightness gamma-rays will be presented. Potential applications of these unique sources of radiation will be discussed with particular emphasis given to the excitation and use of nuclear resonance fluorescence (NRF) for isotope detection and imaging of special nuclear materials of importance to homeland security.
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