C. W. Potts

Negative Hydrogen Ion Injection into the Zero Gradient Synchrotron

In October 1976 the Zero Gradient Synchrotron (ZGS) became the first high energy proton synchrotron to use charge exchange injection in routine operations. Conversion to H- injection has been very successful, yielding record high beam intensities within the first month of use and normal (> 90%) operating efficiencies within the second month. This report discusses briefly the history of H- at the ZGS, the hardware uniquely associated with charge exchange injection and our operational experience during the first two months of H- injection.

A New Diagnostic System for Studying the Injector and Injection at the Zero Gradient Synchrotron (ZGS)

The SFC system provides detailed information about the injector beam and the capture and early acceleration cycle of the ZGS more rapidly and accurately than was previously possible. The system was an important part of the retuning program after the titanium vacuum chamber installation. The SFCs a-re frequently employed in maintaining stable ZGS operation with intense beams.

Status Report on the Rapid Cycling Synchrotron

The Rapid Cycling Synchrotron (RCS), originally designed as an injection energy booster for the Zero Gradient Synchrotron (ZGS), operated under constraints imposed by ZGS operation until December 1979. Once these restraints were removed, the RCS made rapid strides toward its near term goals of 8 ¿A of protons for Argonne National Laboratorys Intense Pulsed Neutron Source program. Reliable 30 Hz operation was achieved in the spring of 1980 with beams as high as 2 × 1012 protons per pulse and weekly average intensities of over 6 ¿A on target. These gains resulted from better injection matching, more efficient RF turnon and dynamic chromaticity control. A high intensity small diameter synchrotron, such as the RCS, has special problems with loss control which dictate prudence during intensity improvement activities. The studies and equipment leading to the intensity gains are discussed.

Injection and Acceleration of Protons in the Zero Gradient Synchrotron (ZGS) by Stripping H Ions

The booster injector program for the ZGS requires the stripping of H ions at 50 MeV as the source of protons in the booster accelerator. 1, 2 Using the former Cornell 2. 2 GeV electron synchrotron as a prototype booster, the injection of protons by stripping negative hydrogen ions in a poly-paraxylene thin film has already been demonstrated at the ZGS. 3 A brightness multiplication factor of 100 has been achieved. The limiting factor is the scattering of the circulating protons in the stripping foil.

Performance of the Intense Pulsed Neutron Source Accelerator System

The Intense Pulsed Neutron Source (IPNS) facility has now been operating in a routine way for outside users since November 1, 1981. From that date through December of 1982, the accelerator system was scheduled for neutron science for 4500 hours. During this time the accelerator achieved its short-term goals by delivering about 380,000,000 pulses of beam totaling over 6 × 1020 protons. The changes in equipment and operating practices that evolved during this period of intense running are described. The intensity related instability threshold was increased by a factor of two and the accelerator beam current has been ion source limited. Plans to increase the accelerator intensity are also described. Initial operating results with a new H- ion source are discussed.

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.

Beam Intensity Increases at the Intense Pulsed Neutron Source Accelerator

The Intense Pulsed Neutron Source (IPNS) accelerator system has managed a 40% increase in time average beam current over the last two years. Currents of up to 15.6 ¿A (3.25 × 1012 protons at 30 Hz) have been successfully accelerated and cleanly extracted. Our high current operation demands low loss beam handling to permit hands-on maintenance. Synchrotron beam handling efficiencies of 90% are routine. A new H- ion source which was installed in March of 1983 offered the opportunity to get above 8 ¿A but an instability caused unacceptable losses when attempting to operate at 10 ¿A and above. Simple techniques to control the instabilities were introduced and have worked well. These techniques are discussed below. Other improvements in the regulation of various power supplies have provided greatly improved low energy orbit stability and contributed substantially to the increased beam current. These improvements are discussed in a paper1 presented at this conference.

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.

A Pulsed Quadrupole System for Preventing Depolarization

A pair of pulsed quadrupoles spaced 180° apart in the Zero Gradient Synchrotron (ZGS) ring was installed to prevent the depolarization of polarized protons during acceleration in the ZGS. These quadrupoles must produce a 50-G/in gradient over a useful aperture of 2 in vertically and 10 in radially. The pulse must have a 10-?s rise time and a 2?-ms flattop. They must be pulsed up to ten times during the 1?-s ZGS acceleration period. The computer calculations and the mechanical and electrical design and fabrication of the quadrupoles and their power supply will be described.

Study of the RF Capture Process in the Argonne Rapid Cycling Synchrotron

The 500-MeV Rapid Cycling Synchrotron (RCS) guide field is energized by a dc-biased, 30 Hz sinusoidal ac power supply, and the field strength varies between 2.81-9.81 kG. During the acceleration period, the ¿ varies in a half-sine function from zero to a maximum of 670 kG/s and back to zero. Although the average ¿ during injection is not equal to zero, efficient capture has been obtained experimentally by adjustment of the RF voltage program and the injection timing. In this paper, we describe a simulation study of the capture process in order to understand the experimental results.