K.D. Jacobs

The MIT-Bates South Hall Ring

The MIT-Bates Linear Accelerator Center is in the process of constructing an electron storage ring. The 190-m ring will be used for internal target experiments with stored beams. It will also be used as a pulse stretcher to provide external beams with high duty factors. The present design incorporates a low beta region with a beta /sub x/ of 1 m and a 4.5 m-space between ring quadrupoles at the internal target location. The ring will contain up to 80 mA using two turn injection. Extraction using a one-half integer resonance will produce up to 50 mu A with a duty factor over 80%. Injection will occur at 1 kHz. Design extracted beam properties include an energy spread of 0.04% and an emittance as low as 0.01 pi mm-mr.<<ETX>>

Emittance measurements at the Bates linac

An emittance measuring system has been installed at the Bates Linear Accelerator Center. The system consists of three wire scanners used to measure the electron beam profile, and a microcomputer for data acquisition and processing. The scanner measures the horizontal and vertical beam size with a possible resolution of 25 mu m. The horizontal and vertical beam phase spaces can then be determined. Results of measurements are presented. Calculations relating the theoretical accuracy of the emittance measurements to the distance separating the scanners and to the beam waists location and size are also presented. Another technique for measuring emittance has also been used. This technique involves using a wire scanner to measure the beam size at a fixed location, as a function of the strength of an upstream quadrupole.<<ETX>>

Stripline beam position monitor for the MIT-Bates South Hall Ring

The MIT-Bates South Hall Ring (SHR) is an electron storage ring currently being commissioned. It is designed to operate at an RF frequency of 2856 MHz with all of the 1812 buckets filled and a circulating current of 80 mA or greater. This leads to a small charge per bunch and the requirement for beam position monitors. Since there will be 31 such monitors in the vacuum system, it is important to suppress trapped modes which may excite coupled bunch instabilities. The stripline monitor built for the SHR is a stainless steel structure, designed to be manufactured using standard machining techniques and commercial feedthroughs. With proper 50 Ohm matching and a geometry derived from insight from MAFIA calculations, the monitor was constructed having a nearly flat RF response up through 10 GHz over the range of measurement. The stripline electronics allows the measurements with 0.1 mm resolution, maintains orbital harmonics information past the 10th harmonic, and operates over a dynamic range of 1 mA to greater than 80 mA of beam current.<<ETX>>

The beam profile measurement system at the Bates linac

A linac beam profile measurement system using wire scanners has been implemented at the Bates Linear Accelerator Center. Obtaining an optimum linac focussing solution is facilitated by the system. A nearly noninvasive beam size measurement is made of the two beams which are accelerated simultaneously in the recirculating linac. The wire scanners mechanical accuracy is near one mil. Beam size measurements are reproducible to a few mils.<<ETX>>

Commissioning the MIT-Bates South Hall Ring

The South Hall Ring at the MIT-Bates Linear Accelerator Center is a 1 GeV electron ring for nuclear physics experiments. It is designed to operate in two modes: as a pulse stretcher to deliver high duty factor beams to external targets, and as a storage ring for internal target experiments. To date we have injected beam into the ring using one and two-turn injection, stored beam with a lifetime of several minutes, and achieved early results performing half-integer resonant extraction from the ring in pulse stretcher mode. Experience in commissioning the ring is presented. Future plans for extraction, improved storage and backgrounds, and spin control and measurement in the ring, are also discussed.

Status of the MIT-Bates South Hall Ring commissioning

This work discusses commissioning of the injection line, the Energy Compression System and the South Hall Ring. Future plans are considered.<<ETX>>

Energy compression system design for the MIT-Bates Accelerator Center

The purpose of the energy compression system (ECS) is to reduce the energy spread of the beam from the linear accelerator. The benefits of the ECS will be to provide a beam with an energy spread lower than that currently available; to reduce the energy centroid shifts from operating fluctuations in the accelerator, and to ensure a beam energy spread commensurate with the requirements of the South Hall Ring (SHR), currently under construction. The last includes minimizing the required RF power for pulse stretcher and storage mode applications. The ECS is to operate with both single pass and recirculated beams.<<ETX>>

Instability calculations for the MIT-Bates South Hall Ring

Instability growth rates and thresholds have been calculated for the MIT-Bates South Hall Ring. Both single bunch and coupled bunch instabilities have been investigated. For single bunch effects, a broadband impedance budget has been developed. Numerical estimates of the impedances of ring components were made, and required to be within the budget. As part of this, the difficulty of fitting computed loss parameters to those derived from the usual broadband impedance model were studied. The authors conclude single bunch instabilities should not be a problem. However, coupled bunch instabilities are a serious concern, since all 1812 of the 2856 MHz RF buckets around the ring are filled.<<ETX>>

Instrumentation at the Bates Linear Accelerator Center

The beam diagnostic systems which are under development at the Bates Accelerator Center of MIT are introduced. Some of the system which have been installed will be described. (AIP)

Real time dispersion measurements at the MIT Bates linac

The MIT-Bates Linear Accelerator Center comprises a 1 GeV electron linac/recirculator system, beam lines to two main experimental halls, and a pulse stretcher/storage ring. Proper tuning of the beam requires the transverse dispersion to be zero, or some specified non-zero value, at all locations along the beam lines. Dispersion measurements are made by correlating beam positions measured by BPMs, with energy measurements made using a BPM in a region of known non-zero dispersion. Data are acquired continuously from the BPMs and displayed on a graphical user interface in real time. This allows the accelerator operators to set dispersion quadrupoles and sextupoles so that the first and second order position and angle dispersions have their correct values at all points along the beam line. Details of the system design and operation are presented.