Recirculating Accelerator Studies.
Abstract
Results of stability calculations for three types of high current betatron (modified betatron, stellatron, solenoidal lens betatron) are presented. For the modified betatron, stability is strongly dependent on the internal poloidal rotation frequency of the beam. When this frequency is close to zero, high-mode numbers are easily stabilized. For the NRL betatron parameters, the beam is predicted to become unstable when it accelerates above 1 MeV. For a 10 kA beam, several kiloamps remain circulating after saturation of the instability. High energy simulations of the modified betatron show saturation without loss of current. Calculations for the stellatron show that background ions have a strong stabilizing effect on the negative mass instability, due to increased transverse focusing. The energy threshold for onset of instability agrees with experimental observation. An electromagnetic three wave interaction is found to occur in the stellatron. Its growth rate can be very large, but parameters can be chosen to move it to short wavelengths where thermal effects should stabilize it. An anlaytic dispersion relation for the solenoidal lens betatron is obtained using a multiple length scaled averaging method. The betatron is predicted to be stable at and slightly above its injection energy. Simulation for higher energy show a strong instability which substrates with some loss of current. Simulations of 10 kA beams in a solenoidal lens betatron show similar results, suggesting that most of the current can survive the instability.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 02, 1987
- Accession Number
- ADA182021
Entities
People
- Brendan B. Godfrey
- Thomas P. Hughes