Alan S. Fisher

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  • North-Holland, Research Sectiona, K Batchelor, I Ben-Zvi, R C Fernow, J Fischer +20 others
  • 2002
The Brookhaven Accelerator Test Facility (ATF) uses a photocathode rf gun to provide a high-brightness electron beam intended for FEL and laser acceleration experiments. The rf gun consists of 1-,' cells driven at 2856 MHz in 7r-mode with a maximum cathode field of 100 MV/m. To achieve long lifetimes, our photocathode development concentrates on robust(More)
SLAC has two electron accelerators, the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests (FACET), providing high-charge, high-peak-current, femtosecond electron bunches. These characteristics are ideal for generating intense broadband terahertz (THz) pulses via coherent transition radiation. For LCLS and FACET(More)
Single-cycle terahertz fields generated by coherent transition radiation from a relativistic electron beam are used to study the high field optical response of single crystal GaAs. Large amplitude changes in the sub-band-gap optical absorption are induced and probed dynamically by measuring the absorption of a broad-band optical beam generated by transition(More)
Evidence of beam loading due to distributed injection in Plasma Wakefield Accelerator experiments carried out at the FACET facility at SLAC during the year 2012 is presented. The source of the injected charge is tunnel ioniza-tion of Rb + inside the wake, which occurs along the length of the interaction at each minima of envelope betatron oscillation. Rb(More)
Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron(More)
We demonstrate the use of intense, quasi-half-cycle THz pulses, with an associated electric field component comparable to intramolecular electric fields, to direct the reaction coordinate of a chemical reaction by stimulating the nuclear motions of the reactants. Using a strong electric field from a THz pulse generated via coherent transition radiation from(More)
We show through experiments and supporting simulations that propagation of a highly relativistic and dense electron bunch through a plasma can lead to distributed injection of electrons, which depletes the accelerating field, i.e., beam loads the wake. The source of the injected electrons is ionization of the second electron of rubidium (Rb II) within the(More)
  • George Bekefi, Abraham Bers, Flora Y F Chu, Bruno Coppi, Thomas H Dupree, Elias P Gyftopoulos +94 others
  • 2009
Introduction In order to produce negative hydrogen or deuterium ion beams, the output of a positive ion source must undergo charge exchange with neutral atoms such as cesium. The maximum efficiency of this process is 217 for 800-eV H + interacting with cesium.1 It has been suggested that by optically exciting the cesium, the efficiency can be improved. 2(More)