M. Knott

Initial Test of a Proton Radiographic System

Protons have a well defined range in matter. A detector, therefore, placed near the end of range of a monoenergetic proton beam becomes a very sensitive measure of changes in the mass of material which the beam has traversed. This property of protons can be exploited in a variety of ways to make radiographs of solid objects. The experimental radiography system we have built to use with the 200 MeV booster synchrotron of the Zero Gradient Synchrotron (ZGS) is described. In addition, there is a brief description of a more elegant system which would operate with a suitable source such as the proton diagnostic accelerator proposed by R. Martin.

Tune Control Improvements on the Rapid Cycling Synchrotron

The as-built lattice of the Rapid Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. A set of octupole magnets and programmable power supplies with similar dynamic qualities have been constructed and installed to control the anticipated high intensity transverse instability. This system will be operational in the spring of 1981.

High Energy Polarized Deuterons at the Argonne National Laboratory Zero Gradient Synchrotron

Modifications made on the ZGS to allow the acceleration of polarized deuterons and the operational experiences with the first production run with this beam are described.

Computer-Based Visualization and Manipulation of Orbit Warps in the Zero Gradient Synchrotron (ZGS)

The low energy orbit warps in the ZGS are corrected by eight current-regulated single-turn kicker windings. The currents regulated in these coils can be set individually by the operators through a central digital control system. Since large first harmonic warps are produced by small current changes in single coils, blind, individual adjustment of the eight currents is seldom productive. This paper describes a computer program and interactive graphic display system which allow accelerator operators to visualize the effects of single or multiple kicker coil current changes. The display provides numeric as well as graphic representation of the orbit warp produced. Localized orbit bumps can be inserted by specifying location and size. The program can be used for offline visualization purposes only, or optionally the desired currents can be introduced immediately by the computer.

Multiplexing Digitized Beam Information for Accelerator Users and Operators

As the list of digitized data signals required by accelerator users and operators grows, it becomes more economical to use serial-input/ multiple-output multiplex receivers at the user/ operator control station than it is to increase the number of coaxial cables used to supply parallel data. Increasingly, on-line computers are used to operate and monitor particle accelerators and since the digitized beam data is most naturally generated sequentially, a multiplexing system becomes doubly desirable. The Central Computer Control Group of the Argonne National Laboratory Zero Gradient Synchrotron (ZGS) has designed and constructed a system using a multiplex receiver called CUPID, an acronym for Computed Pulse Information Decoder. Using two lines of serial input, CUPID generates one master scalar reset pulse and input signals for up to 31 scalars.

Conceptual Design of the Argonne 6-GeV Synchrotron Light Source

The Argonne National Laboratory Synchrotron Light Source Storage Ring is designed to have a natural emittance of 6.5 × 10-9 m for circulating 6-GeV positrons. Thirty of the 32 long straight sections, each 6.5-m long, will be available for synchrotron light insertion devices. A circulating positron current of 300 mA can be injected in about 8 min. from a booster synchrotron operating with a repetition time of 1.2 sec. The booster synchrotron will contain two different rf systems. The lower frequency system (38.97 MHz) will accept positrons from a 360-MeV linac and will accelerate them to 2.25 GeV. The higher frequency system (350.76 MHz) will accelerate the positrons to 6 GeV. The positrons will be produced from a 300-MeV electron beam on a tungsten target. A conceptual layout is shown in Fig. 1. Related papers on the Argonne Synchrotron Light Source may be found in references 1-3.

On-Line Computer Monitoring and Optimization of a Multiple Target Proton Beam Line

Operation, tuning and monitoring of the multiple target external proton beam (EPB) at the Zero Gradient Synchrotron (ZGS) is described. Instrumentation presently installed permits continuous, nondestructive, quantitative, on-line computer monitoring of beam spot size, position, and intensity at each experimenters target or any desired location. The capability of a rapid emittance measurement also is provided. This measurement serves as input to computer programs, described elsewhere, which calculates the emittance and the necessary quadrupole settings for required beam profiles along the beam line. As a check, the resulting beam profiles are instantly measurable at appropriate locations and any necessary final adjustments to provide more exact required conditions are then accomplished.

Omnibus-A Multiprogramming Executive System for the Zero Gradient Synchrotron Control Computer

As the digital computer undergoes increasing utilization as an on-line evaluation and feedback control device for an accelerator, it becomes necessary to provide it with a multiprogramming executive software system. The system should be capable of accommodating several on-line control functions simultaneously so that these functions can be developed independently. The system should also provide for general purpose off-line utilization, such as new program development, to proceed simultaneously with and unimpeded by the continuous operation of the accelerator. OMNIBUS, the multiprogramming executive system now in use with the Zero Gradient Synchrotron (ZGS) control computer, incorporates these features and several others not found in commercially available multiprogramming systems. OMNIBUS obtains data for the various control programs from locations and at specific times requested by the programs and also provides the control link; either by modifying the program stored in the timing system of the synchrotron, or by direct transmission of timing pulses or digitalinformation to the accelerator. The system provides for operator modification of the various control programs and communications with them without interrupting their on-line control or monitoring functions.

Beam Stability in a 6 GeV Synchrotron Light Source

Future synchrotron radiation sources designed to produce low emittance electron beams for wigglers and undulators will present beam position control problems essentially similar to those encountered by users of existing accelerators,1,2 however tolerances will be tighter due to: 1) the small emittance (7× 10-9 mrad) proposed for the electron beam and the correspondingly small emittances (sizes) of secondary photon beams, 2) the sensitivity of the electron beam closed orbit to quadrupole motion and dipole roll, 3) the high power levels associated with undulator and wiggler beams which will permit (and probably require) high precision and stability of the photon beam position measurements, in addition, 4) the large number of users on the roughly sixty beam lines will demand beams capable of producing the best experimental results. For the present paper, we assume the accelerator control function, which would initially involve making and coordinating all changes, would eventually evolve to setting and verifying the limits of user control: within these limits the beam position would be controlled by users. This paper describes the effects of motion of beam components (quads, rf cavities and dipoles) on the beam and considers the properties of a compensation system from the perspective of users. The system departs from standard practice in considering active perturbation of the electron beam to verify beam corrections. The effects of local closed orbit perturbations to direct undulator beams at different experimental setups are also considered.

A Mini-Compuiter Based Digital RF Control System for the ZGS

The systen includes a h igh-resolut ion, f ield-dependent RF frequency program generator, an optically coupled digital-to-frequency converter, and a fast-sampling frequency monitoring section. The frequency program originates as a 500 point field-indexed table of frequencies. Off-set, gain, non-linearity correct ion, and operator control are provided by software. Linear interpolation between break-points is accomplished by dedicated arithmetic logic to provide frequency updates as often as every 20¿ s. An optically coupled digital-to-analog, (D-A) converter controls the 4 to 14 MHz output of the RF section. The output frequency is monitored by a fast sampling, high accuracy logic system, whose output is fed back to the computer for comparison to the desired program.