TUPP04
FRIB, East Lansing, Michigan, USA
Beam loss is an ever-present issue in accelerators and can lead to degraded beam quality, activation, and machine damage. It is crucial to be able to pinpoint the source of beam loss so that the cause can be addressed. Towards this end, beam loss studies were performed at the Facility for Rare Isotope Beams (FRIB) in which beam spills were simulated at various locations within the accelerator. Beam spills were achieved by adjusting the magnetic fields or turning off selected RF cavities. This defocused or moved the beam such that particles impacted the walls, apertures, and other surfaces in the beam transport volume, creating measurable radiation. Losses were monitored on a suite of detectors including neutron detectors, pressurized ion chambers, and halo monitor rings. These data were used in conjunction with calculated beam profiles and statistical analyses in order to correlate loss detection patterns with beam spill location.
TUPP08
MSU, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
Capacitive pickups such as beam position monitors (BPMs), are sensitive to the electric field distribution produced by the beam. For relativistic fields, the fields are flattened therefore they well represent the longitudinal bunch shape. However, for non-relativistic beam, ß<0.1, the field at the pickups can extend past the bunch which affects the measurements from the BPM. This effect from non-relativistic fields is currently accounted for with theory and simulations, however a test stand is also desired that can replicate the field distribution and the bunch velocity. To accomplish this a test stand using a helical transmission line was designed and constructed which propagates with phase velocity of ~0.03c. Presented are measurements of the phase velocity, dispersion, and impedance of the helical transmission line and compared to simulations and theory. Also demonstrated is the ability for the helical transmission line to propagate pulses with minimal deformation and the fields from the helix well represent a particle bunch.
TUPP20
MSU, East Lansing, Michigan, USA
FRIB, East Lansing, Michigan, USA
Capacitive Beam Position Monitors (BPMs) are broadband pickups. For measurements of RF bunched beams, however, they typically use narrowband filters to measure one harmonic of the beam current to reduce noise and simplify the signal processing. If several harmonics are measured simultaneously, the longitudinal bunch shape, in principle, may also be measured. This can be accomplished by recording the waveforms from the BPMs with an oversampling measurement scheme before the narrowband analysis is applied. In order to reconstruct the bunch shape, the measured spectra should be corrected for non-relativistic effects, cable attenuation and filtering, and the geometry and impedance of the BPM pick up. These corrections are discussed as well as the procedure for calibrating the BPM system for measuring multiple harmonics. Measurements are presented that were taken in the medium energy beam transport line and the first linac section at the Facility for Rare Isotope Beams and are compared to simulations and measurements with a fast Faraday cup. Resolution and uncertainties of the reported bunch length measurements are described.