J. Flanz

Simulations of Half and Third Integer Resonant Extraction from a One-GeV Pulse Stretcher Ring

In the past few years, the pulse stretcher ring (PSR) concept has emerged as a viable method for extending the duty factor of pulsed linacs. The viability is a result of considerations such as cost and expected extracted beam quality. A few of the projects emphasize high average extracted beam intensity. This is accomplished through a high injection frequency (1 kHz) and relatively high injected peak currents (greater than or equal to80mA). To enhance the injection efficiency, the number of turns of injection are minimized so the ring is long and there are fewer turns for extraction. There is considerable experience with beam extraction over large numbers of turns from synchrotrons, but time uniform extraction over fewer turns has not been treated as thoroughly. In this paper, some of the extraction calculations made for the proposed MIT-Bates One-GeV Pulse Stretcher Ring are discussed. The theory used for the simulation procedure will be reviewed, the results summarized, and some points of operational interest mentioned.

A cryogenic tritium target system for nuclear physics experiments

Abstract A cryogenic tritium ( 3 H 2 ) gas target system was constructed and used for a program of electron scattering studies. The 3 H 2 was supplied and safely stored as solid U 3 H 3 . For the experiments, it was transferred to a thin walled cylindrical cell, where it was exposed to 25 μA electron beams with energies up to 800 MeV. During operation, the target cell contained 115000 Ci of tritium at 225 psia and 45 K. Multiple safety enclosures surrounded both target and gas transfer systems. A microprocessor-based control and monitoring system presented target parameters to the operators, identifying those out of range. The target system operated safely and effectively for about 2000 h, enabling completion of comprehensive elastic and elastic electron scattering study of the three nucleon system.

Trinucleon Threshold Electrodisintegration

Inclusive inelastic electron scattering cross sections for 3H and 3He were measured for excitation energies below 18 MeV. For six values of the three-momentum transfer q in the range 0.88 < q < 2.87 fm−1, longitudinal and transverse response functions were determined. The experimental data are in good agreement with two recent calculations. One uses variational ground-state wave functions and the orthogonal correlated states method to describe the two- and three-body breakup channels. The other uses bound and continuum Faddeev wave functions for a simple central potential. The inclusion of final-state interactions (FSI) in the Faddeev continuum is found to be very important; inclusion of FSI changes the response functions in the threshold kinematics by a large amount, yielding excellent agreement with the data.

RF System for a 1 GeV Pulse Stretcher Ring

A design study has been completed for the RF system of a pulse stretcher ring to be operated in conjunction with the Bates Linear Accelerator (BLA). The 390m circumference ring is to operate from 300 MeV to 1 GeV, with 80 mA injected current and 1 msec extraction time. The stretcher ring is for nuclear physics research and has radiation damping time and quantum lifetime long compared to the extraction time. The special requirements of the RF system have been considered. Dynamic behavior at the fundamental frequency has been investigated by computer simulation. Higher-order mode impedance limitation has been specified by an investigation of transverse multi-bunch multi-turn instabilities.