J. Claus

A Magnetic Beam Position Monitor

We give the theory and describe the execution of the magnetic beam position monitors in use in the AGS injection line. These are strictly linear devices of very low impedance with a rise time of the order of 1 ?sec. They do not require electronics close to the device and have been constructed to withstand considerable radiation. Their construction is simple and not critical.

Computer Programs for AGS Injection

Since the injection system of the AGS requires very tight control over many parameters, computer programs were written to achieve this. One program initiates an emittance measurement device and reduces its output data to provide the characteristics of the linac beam. The second program utilizes these results to set six quadrupoles and four bending magnets so that requested beam parameters are obtained at the inflector exit. A third program measures the circulating beam and attempts to maximize it by adjustment of quadrupoles and bending magnets. These programs and our experience in using them on-line are described.

On Improving the Chromatic Effects of Storage Rings with Antisymmetric Insertions

High luminosity storage rings require good chromatic behavior for beams with large momentum spreads. This requires that the effects of half-integer structure resonances for off-momentum particles be minimized. We show that a lattice with antisymmetric insertions can be so designed that the driving term for the half-integer structure resonance is suppressed by cancellation of successive pairs of highbeta multiplets. Hence, even though the periodicity is half that of a lattice with symmetric insertions, the chromatic properties are similar.

Incoherent Transverse Space Charge Effects during Injection, RF Capture and Early Acceleration in AGS

After a review of the present situation in the AGS incoherent space charge effects in respectively the just injected beam, the coasting beam and the bunched beam are considered. Numerical estimates of shifts and spreads in betatron frequencies are given. The ratio of peak to average azimuthal densities in bunched beams is calculated for parabolic and uniform initial energy distributions. It is concluded that the intensity limit of the AGS is probably set by loss of particles out of vertical betatron phase via resonances and coupling in the early bunched beam.

The RHIC Lattice

An antisymmetric lattice for the proposed Relativistic Heavy Ion Collider at Brookhaven National Laboratory is presented, which has been designed to have (1) an energy range from 7 GeV/amu up to 100 GeV/amu; (2) a good tunability of ß* and betatron tune; (3) freedom in the choice of crossing angle between beams; and (4) capability of operating unequal species, for example, proton on gold. Suppression of structure resonances is achieved by a proper choice of the phase advances across the insertion and the arc cells.

Reduction of Losses in Linacs for Protons or Heavy Ions

It is necessary to minimize the beam losses in linacs for high average currents in order to avoid serious problems due to radiation damage, dissipation and radio activation of the accelerators structure. A large part of the losses in existing linacs is due to incomplete bunching of the injected beam. Proposed improvements generally appear to be deficient in one or more respects if applied to linacs with conventional frequencies, injection energies and current densities. By preceding the linac proper with an accelerating structure and an energy analyzer, it becomes possible to separate the particles that remained outside the buckets from those that are inside so that they can be dumped in a controlled manner.

Extraction for ISABELLE

The design specifications for ISABELLE, a superconducting proton storage ring facility under construction at Brookhaven National Laboratory call for circulating beam intensities of up to 6 x 1014 protons at 400 GeV energy in each ring. The energy stored in the beam is 41 Megajoules, an order of magnitude more than what has been dealt with in the past. This beam energy cannot be safely disposed of within the confines of the ISABELLE lattice if damage to the dump or quenching of the superconducting magnets is to be avoided. Therefore the full intensity beam must be extracted from the storage rings under all circumstances of emergency or routine beam disposal. Beam losses in excess of 10-3 of the full beam can jeopardize the extraction components and lead to magnet quenching as well. In this note we summarize a conceptual design of the extraction system and discuss the major constraints which lead to the parameters chosen.

Intensity and Energy Spread at Injection in Proton Synchrotrons

Injection and capture in strong focusing proton synchrotrons often involves multiturn stacking in horizontal betatron phase space followed by some approximation of adiabatic capture. The energy spread in the coasting beam is usually relatively small so that the bunches are tight. Local space charge densities may be sufficiently high temporarily to limit intensity. An increase in the energy spread before capture, obtained by a dynamic variation of the energy in the beam to be injected as is done in some weak focusing installations rather than by an increase of its energy spread, should help to alleviate this limitation.

Particle Loss during Adiabatic Capture

In synchrotrons the horizontal betatron acceptance decreases during rf capture and early acceleration because the energy spread increases. We consider this loss of acceptance and propose a method for minimizing it. Consequences of application to the AGS at Brookhaven are presented. It appears that a low energy spread in the injected beam and low rates of acceleration early in the cycle are favorable.