Experience with the low energy demonstration accelerator (LEDA) halo experiment beam instrumentation

Abstract

A 52 quadrupole-magnet FODO lattice has been assembled and operated at the Los Alamos National Laboratory. The purpose of this lattice is to provide a platform to measure the resulting beam halo as the first four magnets of the lattice produce various mismatch conditions. These data are then compared with particle simulations so that halo formation mechanisms may be better understood. The lattice is appended to the LEDA 6.7-MeV radio frequency quadrupole (RFQ) and is followed by a short high-energy beam transport (HEBT) that safely dumps the beam into a 670-kW beam stop. Beam diagnostic instruments are interspersed within the lattice and HEBT. The primary instruments for measuring the beam halo are nine interceptive devices that acquire the beam's horizontal and vertical projected particle density distributions out to approximately 10 5 :1 dynamic range. These distributions are acquired using both traditional wire scanners and water-cooled graphite scraping devices. The lattice and HEBT instrumentation set also includes position, bunched-beam current, pulsed current, and beam loss measurements. This paper briefly describes and details the operation of each instrument, compares measured data from the different types of instruments, and refers to other detailed papers.

Upgrade to initial BPM electronics module and beamline components for calibration of the LEDA beam position measurements

“…The addition of the attenuator characterization files decreased system error. The calibration test routine showed that the total absolute errors for horizontal and vertical position are well within specified tolerance [1]. …”

“…First, it provides information that allows the centering of the beam in the HEBT and into the beamstop. Secondly, it allows verification of the quadrupole magnetic field settings by offsetting the beam position from magnetic lattice center [1].…”

“…These data were taken from BPM 29 that was one of the BPMs showing the smallest level of error. See [1] for an example using one of the lattice BPMs with the highest level of relative error. From the Figure 3 it is seen that both the horizontal and vertical maximum errors were below 0.025 mm over the 1 to 100 ma operating range of the accelerator.…”

Low-Energy Demonstration Accelerator (LEDA) test results and plans

“…This channel (Fig. 4) contains 52 singlet quadrupole magnets, ten x-y steering magnet pairs, ten stripline beam position monitors, nine x-y beam profile monitors (each unit contains a wire scanner and two halo scrapers as described in [25]), five PMT-based beam-loss monitors, and three AC current toroids [26]. The HS/WS diagnostic device [25] records the beam profile with~10…”

Analog front-end electronics for beam position measurement on the beam halo measurement

“…Several of the problems encountered with that system have been corrected, as well as new capabilities added, with the resultant system being presented here. Currently the LEDA accelerator is configured to conduct a beam halo experiment.Beam diagnostics include fifteen beam position monitors in the 52-quadrupole magnet focusingdefocusing (FODO) lattice, along with wire scanners, beam-loss monitors and current monitors [7]. The nature of the experiment places a requirement for additional dynamic range on the BPM electronics.…”