THICCC001
KEK, Ibaraki, Japan
Sokendai, Ibaraki, Japan
Toshiba, Tokyo, Japan
The beam halo control is of a great importance to attain high intensity beams. Thus, its detailed treatment is indispensable for the stable and safe operation. A systematic beam halo study was established at the KEK Compact ERL (cERL) since machine commissioning in spring 2015 in order to understand the beam halo formation and to have the stable and safe operation. The results of halo simulations have given a reasonable explanation of the low bunch charge (0.2-0.3 pC) beam profiles evaluated during the measurement. Thus, vertical beam halos observed at cERL are supposed to be due to the longitudinal bunch tails transferred into the transverse plane. Tails are mainly produced by the cathode response on the laser excitation. Further, when a beam passing the rf cavity off-center it experiences rf field kicks. The beam tilt could be a complex effect of the steering coils and cavities misalignments. During spring 2017 commissioning the bunch charge was increased up to 40 pC. In present study we are challenging to describe how the space charge effect acts on the beam halo profiles, and how the halo formation mechanisms change in this connection.
Institut Theorie Elektromagnetischer Felder, TU Darmstadt, Darmstadt, Germany
IKP, Mainz, Germany
The Institute for Nuclear Physics (KPH) at Mainz is building a multi-turn energy recovery linear accelerator, the Mainz Energy-recovering Superconducting Accelerator (MESA), to deliver a CW beam at 105 MeV with short pulses, high current and small emittance for physics experiments with an internal target. Space charge effects potentially cause beam quality degradation for medium energy beams in smaller machines like MESA. As beam quality preservation is a major concern in an ERL during recirculation. We present a study on Microbunching Instability (MBI) caused by Longitudinal Space Charge (LSC) in MESA. Our results demonstrate the impact of the MESA arc lattice design on the development of Microbunching Instability.
THICCC003
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
QST, Tokai, Japan
We have developed a DC gun test stand at National Institutes for Quantum Radiological Science and Technology (QST) for high current electron beam generation. The gun test stand consists of an alkali antimonide photocathode preparation chamber, a DC gun with a 250kV-50mA Cockcroft Walton high voltage power supply, and beam line with a water cooled beam dump to accommodate 1.5 kW beam power. We successfully fabricated a Cs3Sb photocathode with quantum efficiency of 5.8 % at 532 nm wavelength and generated 150 keV beam with current up to 4.3 mA with 500 mW laser at 532 nm wavelength. Unfortunately, we encountered a vacuum incident during beam transport of high current beam and the development has been halted. We will fix the vacuum problem and restart the gun development as soon as possible.
THICCC004
TRIUMF, Vancouver, Canada