Microwave measurements and beam dynamics simulations of the BNL/SLAC/UCLA emittance-compensated 1.6-cell photocathode rf gun

Dennis T. Palmer; Roger H. Miller; Herman Winick; Xi Jie Wang; Kenneth Batchelor; Martin H. Woodle; Ilan Ben-Zvi

doi:10.1117/12.221609

25 September 1995 Microwave measurements and beam dynamics simulations of the BNL/SLAC/UCLA emittance-compensated 1.6-cell photocathode rf gun

Dennis T. Palmer, Roger H. Miller, Herman Winick, Xi Jie Wang, Kenneth Batchelor, Martin H. Woodle, Ilan Ben-Zvi

Author Affiliations +

Proceedings Volume 2522, Electron-Beam Sources and Charged-Particle Optics; (1995) https://doi.org/10.1117/12.221609
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

A dedicated low energy (2 to 10 MeV) experimental beam line is now under construction at Brookhaven National Laboratory/Accelerator Test Facility (BNL/ATF) for photocathode RF gun testing and photoemission experiments. Microwave measurements of the 1.6 cell photocathode RF gun have been conducted along with beam dynamics simulations of the emittance compensated low energy beam. These simulations indicate that the 1.6 cell photocathode RF gun in combination with solenoidal emittance compensation will be capable of producing a high brightness beam with a normalization rms emittance of (epsilon) _n,rms approximately equals 1 (pi) mm mrad. The longitudinal accelerating field E_z has been measured as a function of azimuthal angle in the full cell of the cold test model for the 1.6 cell BNL/SLAC/UCLA #3 S-band RF Gun using a needle rotation/frequency perturbation technique. These measurements were conducted before and after symmetrizing the full cell with a vacuum pump out port and an adjustable short. Two different waveguide to full cell coupling schemes were studied. Experimental and theoretical studies of the field balance versus mode separation were conducted. The dipole mode of the full cell using the (theta) - coupling scheme is an order of magnitude less severe before symmetrization than the Z- coupling scheme. The multi-pole contribution to the longitudinal field asymmetry are calculated using standard Fourier series techniques for both coupling schemes. The Panofsky- Wenzel theorem is used in estimating the transverse emittance due to the multipole components of E_z. Detailed beam dynamics simulations were performed for the 1.6 cell photocathode RF gun injector using a solenoidal emittance compensation technique. The design of the experimental line along with a proposed experimental program using the 1.6 cell photocathode RF gun developed by the BNL/SLAC/UCLA RF gun collaboration is presented. This experimental program includes measurements of beam loading caused by dark current, higher order mode field measurements, integrated and slice emittance measurements using a pepper-pot and RF kicker cavity.

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Dennis T. Palmer, Roger H. Miller, Herman Winick, Xi Jie Wang, Kenneth Batchelor, Martin H. Woodle, and Ilan Ben-Zvi "Microwave measurements and beam dynamics simulations of the BNL/SLAC/UCLA emittance-compensated 1.6-cell photocathode rf gun", Proc. SPIE 2522, Electron-Beam Sources and Charged-Particle Optics, (25 September 1995); https://doi.org/10.1117/12.221609

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