TechSource, Santa Fe, New Mexico
LANL, Los Alamos, New Mexico
SLAC, Menlo Park, California
Recent beam physics studies on the two-stream e-p instability at LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Experimental results will be presented on various characteristics of electron cloud obtain from experiments using this diagnostic and compared with simulations. Results include data on flux and energy spectra of electrons striking the vacuum chamber, the line density and lifetime of electrons trapped in the quadrupole after the beam has been extracted as well as evidence regarding electrons ejected from the magnet during passage of the proton beam.
LANL, Los Alamos, New Mexico
The LANSCE linac simultaneously provides both H+ and H- beams to several user facilities. The Weapons Neutron Research (WNR) user facility is configured to accept the H- beam with a typical pulse pattern of one linac micro-pulse every 1.8 microseconds. To produce this pulse spacing a slow-wave chopper located in the 750 keV injector beam transport is employed to intensity modulate the beam. The beam is subsequently bunched at both 16.77 MHz and 201.25 MHz prior to entering the 100 MeV drift tube linac. One downside of the chopping process is that the majority of the beam produced by the ion source during the WNR macro-pulses is discarded. By applying a longitudinal bunching action immediately following the ion source, simulations have shown that some of this discarded beam can be used to increase the charge in these micro-pulses. Recently, we began an effort to develop this buncher by superimposing 16.77 MHz RF voltage on one of the HVDC electrodes in the 80 kV column located inside H- Cockcroft-Walton dome. This paper describes the beam dynamics simulations, design and implementation of the rf hardware and the results of tests performed with the system.
LANL, Los Alamos, New Mexico
LANL, Los Alamos, New Mexico
Presently, the Los Alamos National Laboratory is in the process of planning a refurbishment of various sub-systems within its Los Alamos Neutron Science Center accelerator facility. A part of this LANSCE facility refurbishment will include some replacement of and improvement to existing older beam diagnostics instrumentation. While plans are still being discussed, some instrumentation that is under improvement or replacement consideration are beam phase and position measurements within the 805-MHz side-coupled cavity linac, slower wire profile measurements, typically known as wire scanners, and possibly additional installation of fast ionization-chamber loss monitors. This paper will briefly describe the requirements for these beam measurements, what we have done thus far to answer these requirements, and some of the technical issues related to the implementation of these instrumentation.