The Bevalac extraction time was increased from 1 to a maximum of 9.5 seconds, thus increasing the synchrotron duty factor and the data rate for experiments by a factor of 2-3, depending on the magnetic field. This slow rate of extraction required improved control of beam time structure, since magnet ripple remained approximately constant while the spill rate was decreased. Measurements of spill structure for the long spill are presented. Changes made to the accelerator systems are described, as well as tuning procedures found to be necessary, and the ultimate hardware limits found for the spill length

Until July of 1992, the maximum length of the Bevalac flattop was 2 seconds, limiting the beam spill to 1.5 seconds. The normal running condition was a 1.5 second flattop, with a 1.0 second beam spill. If we define the duty factor as the spill length (in time) divided by the synchrotron pulse length, that is, the percentage of time the Bevalac can deliver beam to experiments, the duty factor for the 1.5 second flattop ranged from 17% (at full field, i.e., 12575 G) to 25% (low field). The purpose of the Long Flattop Project was to increase the length of the flattop, thus increasing the duty factor of the machine, and its efficiency for experiments. This has been done, with resultant increase in the duty factor and experimental data rate. It is now possible to run with duty factor of about 80% for low fields, falling to about 60% at 10 kG, and 34% at full field. This report documents what was done, and its limitations. It should be noted that increasing the length of the beam spill is only possible if the source can produce more beam per pulse than is usable by the experimenter. Experimenters running at full intensity with a short flattop (1.5 seconds) cannot benefit from a longer flattop. This paper describe the changes that have been made to Bevalac systems to make the long flattop possible, the limits put on the length of the flattop by existing hardware, and the procedure for tuning for the long flattop.

The time structure of the Bevalac beam spill has been measured for spills with and without feedback. A filter across the magnet has reduced spill ripple near 170 Hz. Low-frequency spill structure has been improved by removing the scintillator used for feedback from the vacuum chamber, detecting instead radiation generated by collisions of beam particles with a wire chamber. Pulse-to-pulse variation of the circulating beam intensity has been reduced, and continuous tunability of the intensity introduced, by using a feedback system. This system reduces the RF bucket height to spill beam until the proper intensity is reached.<>

It is noted that demand for relativistic heavy-ion beams at the Bevalac has increased dramatically in the past two years. To keep pace, the Bevalac makes use of five injectors, precise guide field control, present beam transport line tunes, nine nuclear science target areas, and three biology/radiotherapy areas, along with elegant computer control algorithms, to achieve high operating efficiency. Routine operation includes as many as ten ion/energy/beamline changes per day, 15 major nuclear science experiments each year, and radiotherapy on nearly a daily basis, with biology experiments operating biweekly. High operating efficiency and low failure rates combine to produce high annual research hours

This handbook is intended as an aid for tuning the external particle beam (EPB) lines at the Lawrence Berkeley Laboratory's Bevalac. The information contained within will be useful to the Bevalac's Main Control Room and experimenters alike. First, some general information is given concerning the EPB lines and beam optics. Next, each beam line is described in detail: schematics of the beam line components are shown, all the variables required to run a beam transport program are presented, beam envelopes are given with wire chamber pictures and magnet currents, focal points and magnifications. Some preliminary scaling factors are then presented which should aid in choosing a given EPB magnet's current for a given central Bevalac field. Finally, some tuning hints are suggested.

Beams of accelerated heavy ions can now be delivered as one-second-long DC pulses with minimal fluctuations in instantaneous flux. Pulse duration can be held constant to within 1% while keeping a high non-varying extraction efficiency which minimizes pulse-to-pulse position shift in the extracted beam. In addition, differing beam intensities over several orders of magnitude can be delivered. Computer adjustment of all measurement and control devices results in linear operation over three orders of magnitude of beam intensity. Control of beam structure is accomplished by a unique combination of dual slope integrators and phase forward "predictive" circuits in the feedback loop.

Heavy ion radiobiology has been integrated successfully into the research program at the Bevatron/Bevalac for the past several years. During the 1979-1980 year radiotherapy trials have been conducted side-by-side with the demanding program of heavy ion nuclear science research at this national facility. Careful attention is given to the scheduling of research on the SuperHILAC and Bevatron/Bevalac so that the nuclear science and biomedical programs at the Bevatron/Bevalac and the program at the SuperHILAC are served to maximum effect. Efforts to maximize the researchers' time have resulted in hardware, software, and operating improvements that offer a total machine availability of about 90% and a user availability of about 80%. Fast beam switching and beam sharing permit virtually simultaneous use of the Bevatron/Bevalac by two or more users. Current beam delivery systems will be augmented in FY81 to provide two ion energies per Bevatron/Bevalac pulse.

We present results of the first attempts to accelerate partially stripped heavy ions in the Bevatron. Experiments were performed for hydrogen-like argon and neon ions, and, although the survival time of these ions in the 10-7 torr Bevatron vacuum was not sufficient to achieve full energy, valuable charge-changing cross section information was obtained.

The performance of the Bevalac is reported. The Bevalac uses the LBL SuperHILAC as the heavy ion injector to the Bevatron. Ion species up to 40A have been accelerated to energies of 1.9 GeV/A at modest intensity. Neon has been accelerated to 2.1 GeV/A at an intensity of 4·1010 particles per pulse. The modifications to the SuperHILAC and Bevatron are briefly reviewed and the computer control system is described. Results of the first phase of operation and plans for further improvements are reported.