T. Russ

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>>

The Bates pulse stretcher ring control system design

The design of the control system for MITs pulse stretcher ring is described. Heavy use is made of standard hardware and software elements. Particular emphasis is given to the design of a true distributed system, one that can expand both at the data acquisition/control and at the data processing end. For this purpose, a method is proposed to avoid increasing the traffic on the network when adding more computers. Issues related to real-time response and user interfaces are also treated. Measurements to data are summarized.<<ETX>>

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.

A table driven database and applications generator for accelerator control systems

The proposed system of describing ring data should make it easy for the user to do high-level application development by hiding details behind logical naming schemes. It will guarantee system-wide configuration data integrity by keeping it defined in one place, in the central database. The decrease in dependence on skilled computer personnel to maintain this information is well worth the added cost in computer hardware required to support it.<<ETX>>

Measurements of quadrupole magnets for the MIT-Bates SHR

Results of measurements on 24 of the 128 new quadrupole magnets for the pulse storage/stretcher ring currently under construction at the MIT-Bates Accelerator Center are presented. At the outset it was decided to measure excitation curves for every quadrupole, and at the same time have enough sensitivity to extract the harmonic content. Measurements indicate that one can remeasure a quadrupoles strength and reproduce the value of (B/sub o/L/sub eff//a) versus current to better than 0.1%. Measurements also indicate that one can reserve the polarity of a quadrupoles remnant field by repeated cycling between 0 and 150 A, and obtain the same results (to the 0.1% level) as were obtained previously.<<ETX>>

A distributed power-supply controller using the BITBUS interface

Abstract A distributed controller for high-stability magnet power supplies was developed using the BITMUS interface. It has the dual function of providing an interface to a remotely located control system and upgrading the regulation loop of commercial power supplies. The controller consists of two boards: a digital subsystem, which provides the BITBUS interface together with control, status and interlock functions, and an analogue subsystem, which integrates a high-stability digitally controlled voltage reference, a shunt and error amplifier and three 16-bit analogue-to-digital converters for reading back power-supply current and voltage values. Complete galvanic isolation between the digital and analogue subsystems enhances common-mode noise rejection and avoids ground return currents. Hardware and software aspects of the controller and its control-system driver are discussed. Performance data are presented for a series of such controllers connected to the MIT-Bates Pulse Stretcher Ring control system

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>>

Fast TEM kicker with MOSFET solid state driver

The design of a fast transverse electromagnetic (TEM) kicker for use in the Bates Pulse Stretcher Ring is described. It provides a 1-mrad/m kick for a 1-GeV electron beam, with transition times below 25 ns and a 1% flat top. The +or-10 kV driver uses a switching technique based on MOSFET power transistors that allow complete control over the kicker timing and simplifies the construction greatly. Calculations show that the reliability of such a driver is orders of magnitude better than that provided by present designs.<<ETX>>

BPM data acquisition system for the Bates pulse stretcher ring

A beam positioning monitoring system is being developed. It will include approximately 30 stripline monitors distributed around the South Hall Ring. These BPMs (beam positioning monitoring systems) will be sampled by flash analog-to-digital converts operating at 40 MSPS. Each ADC (analog-to-digital converter) is connected to a FIFO that can be read by the CPU (a SparcStation in a single VME slot, running SunOS) and transferred via Ethernet to the central control system, after some local processing. Hardware and software operation of the prototype are described.<<ETX>>