Space-charge distortion in the Brookhaven Ionization Profile Monitor
An Ionization Profile Monitor (IPM) has been in use at the Brookhaven Alternating Gradient Synchrotron for several years to measure the horizontal and vertical profiles of the circulating beam. The device, which collects ions from the interaction of the beam with residual gas molecules, gives a fast, non-destructive readout, measuring the entire beam profile in a short time interval. It covers a large dynamic range, from less than 10/sup 10/ to over 2 x 10/sup 13/ protons per pulse, when the signal level is adjusted by controlling the local gas pressure and the integrating time. It can see changes in the beam with a time resolution of about 0.1 ms, except at low intensities where longer integration times are needed to get sufficient signal strength. However, the forces due to the space-charge of the circulating beam cause the ions to move in a curved path to the collector, distorting the profile and changing the measured beam size. In the worst situation at the AGS - high current beams at high energy, when the size has damped down to less than 2mm rms width - this distortion is substantial and must be understood and corrected, if possible, to properly interpret the measured beam sizes. This paper develops a model for this distortion, and formulas for correcting it. It is shown that the distortion is more severe than originally recognized, and that accurate quantitative measurements at the highest beam densities in the AGS are not possible. At lower densities, however, the correction is small and the IPM can give a good beam size measurement.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6610546
- Report Number(s):
- BNL-39487; CONF-870302-80; ON: DE87007644
- Resource Relation:
- Conference: Particle accelerator conference, Washington, DC, USA, 16 Mar 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BEAM MONITORS
ACCURACY
BEAM PROFILES
BROOKHAVEN AGS
COMPUTERIZED SIMULATION
MONTE CARLO METHOD
SPACE CHARGE
ACCELERATORS
CYCLIC ACCELERATORS
MEASURING INSTRUMENTS
MONITORS
SIMULATION
SYNCHROTRONS
430200* - Particle Accelerators- Beam Dynamics
Field Calculations
& Ion Optics