Author: Gover, A.
Paper Title Page
TUP007 Spectral Limits and Frequency Sum-rule of Current and Radiation Noise Measurement 362
  • A. Gover, R. Ianconescu
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • A. Nause
    UCLA, Los Angeles, USA
  Funding: This research was supported by a grant from the United States-Israel Binational Science Foundation(BSF), Jerusalem, ISRAEL
The current noise spectrum of an electron beam is generally considered white and expressed by the shot-noise formula (eI0). It is possible to control the spectral energy of a random electron beam current by longitudinal space charge microdynamics and dispersive transport. Both noise suppression (relative to eI0)[1,2] and noise enhancement[3] have been demonstrated, exhibiting sub/super-Poissonian particle distribution statistics, respectively. We present a general theory for the current noise of an e-beam and its radiation emission in the entire spectrum. The measurable current noise spectrum is not white. It is cut-off at high frequencies, limited by the measurement length and the beam axial momentum spread (fundamentally limited by quantum uncertainty). We show that under certain conditions the current noise spectrum satisfies a frequency sum-rule: exhibiting noise enhancement in one part of the spectrum when suppressed at another part and vice versa. The spontaneous emission (radiation noise) into a single radiation mode or single direction in any scheme (OTR, Undulator etc.) is sub-radiant when the beam current is sub-Poissonian and vice versa, but the sum-rule does not apply.
TUP064 Narrow Linewidth, Chirp-Control and Radiation Extraction Optimization in an Electrostatic Accelerator FEL Oscillator 509
  • H. S. Marks, A. Gover, H. Kleinman, J. Wolowelsky
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  • D. Borodin, M. Einat, M. Kanter, Y. Lasser, Yu. Lurie
    Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
  In recent years the electrostatic accelerator FEL based in Ariel has undergone many upgrades. By varying the accelerating potential the resonator allows lasing between 95-110 GHz. It is now possible to remotely control the output reflectivity of the resonator and thereby vary both the power built up in the resonator and that emitted. This has allowed fine control over the power for different user experiments. A voltage ramping device has been installed at the resonator/wiggler to correct drops in voltage which occur due to electrons striking the walls of the beam line. This has allowed stable pulses of just over 50 μs with a chirp rate of ~80 kHz/μs.  
TUP081 Configuration and Status of the Israeli THz Free Electron Laser 553
  • A. Friedman, N. Balal, V.L. Bratman, E. Dyunin, Yu. Lurie, E. Magori
    Ariel University, Ariel, Israel
  • A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  Funding: This project is funded in part by Israel Ministry of Defense.
A THz FEL is being built in Ariel University. This project is a collaboration between Ariel University, and Tel Aviv University. Upon completion it is intended to become a user facility. The FEL is based on a compact photo cathode gun (60 cm) that will generate an electron beam at energies of 4.5 - 6.5 MeV. The pulses are planned to be of 300 pico Coulomb for a single pulse, and of up to 1.5 nano Coulomb for a train of pulses. The FEL is designed to emit radiation between 1 and 5 THz. It is planned to operate in the super radiance regime. The configuration of the entire system will be presented, as well as theoretical and numerical results for the anticipated output of the FEL, which is in excess of 150 KW instantaneous power. The bunching of the electron bean will be achieved by mixing two laser beams on the photo-cathode. The compression of the beam will be achieved be introducing an energy chierp to the beam and passing it through a helical chicane. We plan on compressing the single pulse to less than 150 femto seconds. The status of the project at the time of the conference will be presented.
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