Beam chopper for the low-energy undulator test line (LEUTL) in the APS

Abstract

'9700 South Cass Avenue, Argonne, Illinois 60439 USAThe high voltage operation requires special attentl nd @gj+ --.to insulation for reliability and safety. Also the age short pulse operation requires good elec shielding for noise suppression. For this purpose, but not shown in the figure, an aluminum shroud will also be installed around the chopper assembly. A water-cooled copper beam dump with a vertical slot for beam passage is placed in the downstream 2.75" Conflat flange. The design specifications of the chopper system components are shown in Table I. AbstracrThe low-energy undulator test line ILEUTL) is being built and will be tested with a short beam pulse from an rf gun in the Advanced Photon Source (APS) at the Argonne National Laboratory. In the LEUTL a beam chopper is used after the rf gun to deflect the unwanted beam to a beam dump. The beam chopper consists of a permanent magnet and an electric deflector that can compensate for the magnetic deflection. A 30-kV pulsed power supply is used for the electric deflector. The chopper subsystem was assembled and tested for beamline installation. The electncal and beam properties of the chopper assembly are presented.

The Linac Extension Area at the Advanced Photon Source

“…To limit the beam current in the linac, fail-safe beam choppers are installed immediately downstream of the electron guns [39][40][41]. The choppers function as a Wien filter [42]: a constant magnetic field is present, which deflects the beam to a dump unless a pulsed electric field kicks the beam to pass the filter.…”

Experimental performance of an E×B chopper system

“…It is, to our knowledge, the first time that this concept is used to chop ion beams. However, a similar concept was previously employed to reduce the duty cycle of a low-energy electron beam for the Low-Energy Undulator Test Line (LEUTL) in the Advanced Photon Source (APS) at Argonne National Laboratory [28].…”

Microbunching of thermionic cathode rf gun beams in the Advanced Photon Source s-band linac

“…Our interest was to measure the charge of each micropulse within the macropulse structure from the chopper-gated [4], TC-rf gun [5][6][7]. The extraction of charge from the TC rf gun involves high-power rf applied to the cathode; thus, the extracted charge comes in a series of micropulses.…”