B. DeVito

Cooling High Intensity Atomic Hydrogen Beams to Liquid Heliumi Temperatures

An atomic hydrogen source, designed to operate in the viscous flow range, has been built at BNL. A unique feature of this source is a miniature gap between a teflon tube which guides the beam and an accommodator which cools it. Across this gap a stepfunction in temperature, with the teflon temperature exceeding 100°K and the accommodator temperature below 8°K, was successfully maintained. This configuration collimates the beam enough to prevent significant diffusive losses without subjecting it to the temperature range of high recombination. Initial results with an orifice of only one-tenth the dissociator aperture are indicative of particle density in the beam of well above 1010 cm-3.

Polarized ion source development at Brookhaven

The present AGS polarized hydrogen ion source is discussed. Topics described in details are cold atomic beam, spin selection and focusing, and ring magnetron ionizer. The performance of the 6 K neutral hydrogen beam source has exceeded expectations. The necessary improvements to make an operational source for the polarized ion beams for the AGS experiments will be made.(AIP)

BNL intense polarized H− source progress

Components are being developed which will eventually be part of a high‐current polarized H− source. An atomic beam has been cooled to 6 K, resulting in a most probable velocity of approximately 680 m/s and a forward flux of about 3×1020 H0/sr/s. Focusing of this beam with a superconducting solenoid was unsuccessful at high H0 densities due to H0‐H0 scattering. A permanent magnet sextupole is now being tested. An ionizer based on the charge exchange of the polarized H0 with ≊150‐eV D− has also been studied.

AGS Injector Beam Monitoring System

The performance of the AGS depends critically on the linac beam characteristics such as beam intensity, proton momentum, momentum spread and beam transverse phase space distribution. These parameters are measured by pulse deflection of the 50 MeV proton beam into a separate analyzing channel in which continuous beam analysis and monitoring is possible without interruption of regular AGS operation. In addition to a general description of the linac-synchrotron beam transport and analyzing system, details of the momentum spread and monitoring system are presented.

The BNL polarized H− ion source development program

Polarized protons have been available for acceleration in the AGS for the high energy physics program since 1984. The polarized H− source, PONI‐1, has routinely supplied a 0.4 Hz, 400 μsec pulse having a nominal intensity of 40 μA. Polarization is ∼80% out of the ion source. After PONI‐1 became operational, a program was initiated to develop a more intense source based on a cold ground state atomic beam source, followed by ionization of the polarized H° beam by D− charge exchange. Various phases of this work have been fully reported elsewhere, and only a summary is given here.

Recent developments in the BNL intense polarized H− source program

A program to develop a high intensity polarized H− ion beam for injection into the AGS is under way at this laboratory. The approach we are following is essentially the polarization and ionization of a very cold and intense atomic hydrogen beam. This paper reports on the magnetic focusing of the cold atomic hydrogen beam we have produced.

The new BNL polarized negative ion source

A new ground state source of negative hydrogen ions with polarized nuclei (H−) is being developed at BNL. Extensive developmental research has been aimed at improving each element of (H−) production: cold H° beam, spin selection and focusing magnets, and ionizer. These elements have recently been integrated into a source. A first test with the accommodator nozzle cooled only to liquid nitrogen temperatures resulted in 5 μA of H−. Tests at liquid helium temperatures are now beginning.

Studies of Quench Propagation in a Superconducting Window Frame Magnet

During the testing of a meter long, superconducting window frame magnet, information from many spontaneously generated quenches have been recorded by an on-line computer system. Nearly every layer in an eleven layer dipole had a voltage tap and for some layers this subdivided into two halves. This allowed us to study development of the quenches in some detail. Knowledge of the resistances throughout the magnet also allowed the temperature distributions in the superconducting windings to be determined. A qualitative picture of the quench was developed and quantitative values of quench propagaton velocities were compared to heat transfer calculations.

The Brookhaven 50-MeV Linac RF Multiport System

A new high power RF system has been installed at the Brookhaven 50-MeV linac to accelerate the higher beam intensities now available from an improved preinjector. Use has been made of the previous efforts of many people to reach a final flexible system design. Initial system operation to date has increased by a factor of two the linac output current intensity while obtaining an energy spread comparable to the one observed for lower currents.