Mark Q. Barton

Ion trapping with asymmetric bunch filling of the NSLS VUV ring

Abstract In electron storage rings, the performance can be limited by ions formed in the residual gas and trapped by the beam potential. At NSLS it has been found that the effect is less severe if the beam is filled with a sequence of full bunches followed by a gap of empty buckets. The calculations of this paper show that this improved performance is expected based on a simple extension of the usual ion trapping model.

Initial Performance of the AGS Slow External Beam

The internal beam of the Brookhaven AGS has been extracted by exciting the third-integral nonlinear resonance at a horizontal tune of ?H = 8-2/3. The extraction efficiency is approximately 80% and the spill duration ~ 300 to 400 ms. The beam has been extracted over the energy range 20 to 29 GeV. Preliminary measurements of horizontal and vertical emittance give EH ? 0.036 ? in.-mrad and EV ? 0.09 ? in.-mrad. Intensity modulation of the spill is presently about 40%.

High Intensity Beam Instabilities in the Brookhaven AGS

Transverse resistive wall instabilities and longitudinal reactive wall instabilities have both been observed in the Brookhaven AGS. Recently an instability has been observed characterized by individual coherent phase oscillations of the twelve beam bunches. This instability is believed to be caused by high frequency resonance modes in the rf cavities introduced by recent modifications. A simple analysis shows that voltages induced in these parasitic resonances by the beam can couple the phase oscillations of the individual bunches. A normal mode analysis of the system predicts unstable normal modes with properties similar to the observations. Modifications to the rf cavities to suppress these undesirable effects have been devised.

Acceleration of Heavy Ions in the AGS

It is possible to use the Brookhaven AGS as a heavy ion machine by adding a cyclotron to the Tandem and using this combination as injector. An intermediate step for lighter ions might consist of injecting the Tandem beam directly into the AGS. In either case, quite high intensities should be possible.

A Study for a 6 GeV Undulator Based Synchrotron Radiation Source

A partial study for a 6 GeV undulator based synchrotron radiation source for production of high brightness undulator radiation, in the Å, is presented. The basic lattice adopted for the storage ring is a hybrid FODO Chasman-Green lattice, making use of gradient in the dipoles. We discuss also the e beam current limits and the injection parameters.

Heavy Ion Collisions in a Collider at BNL

Heavy ions accelerated in the AGS can be injected into CBA providing colliding beams up to 400 Q/A Gev/amu. Luminosities approaching 1028/cm2sec. should be achievable even though the ions must be accelerated through phase transition. More current might be stacked by using a special ¿T jump method to avoid the excessive radial aperture usage at transition.

Coalescence of bunches in a synchrotron to change acceleration harmonic number

Abstract The accelerating harmonic number in an ion accelerator can be reduced by half during acceleration by generating an rf waveform which is a composite of the initial frequency and the lower harmonic frequency. The computer simulation described in this paper shows how the rf bunches are combined.

Panel: Computer Control Application of an On-Line Computer to Accelerator Studies

The use of an on-line computer to expedite accelerator studies may be one of its most important applications. This report is a discussion of some of the types of problems for which computer assistance is of value and describes some implications on the configuration.

Panel Discussion on Computer Control

The panelists made short oral presentations, based on the prepared remarks included below, describing the systems they use and the ways the configurations were determined by the particular requirements at each laboratory. Most of the session was an informal discussion, roughly organized about system configuration, reliability, closed-loop control and software. The session was closed with Madsens discussion relating computer control to accelerator physics, from his prepared statement.