J. Wei

Transverse phase space painting for SNS accumulator ring injection

The results of investigation and comparison of a series of transverse phase space painting schemes for the injection of the SNS accumulator ring is reported. In this computer simulation study, the focus is on the creation of closed orbit bumps that give desired distributions at the target. Space charge effects such as tune shift, emittance growth and beam losses are considered. The results of pseudo end-to-end simulations from the injection to the target through the accumulator ring and the Ring to Target Beam Transfer (RTBT) system are presented and discussed.

Field quality evaluation of the superconducting magnets of the Relativistic Heavy Ion Collider

In this paper, we first present the procedure established to evaluate the field quality, quench performance, and alignment of the superconducting magnets manufactured for the Relativistic Heavy Ion Collider (RHIC), and then discuss the strategies used to improve the field quality and to minimize undesirable effects by sorting the magnets. The field quality of the various RHIC magnets is briefly summarized.

Focusing and matching properties of the AtR transfer line

The AGS to RHIC (AtR) beam transfer line has been constructed and will be used to transfer beam bunches from the AGS machine into the RHIC machine which is presently under construction at BNL. The original design of the AtR line has been modified. This article presents the optics of the various sections of the existing AtR beam line, as well as the matching capabilities of the AtR line to the RHIC machine.

RHIC sextant test: accelerator systems and performance

One sextant of the RHIC Collider was commissioned in early 1997 with beam. We describe here the performance of the accelerator systems during the test, such as the magnet and power supply systems, instrumentation subsystems and application software. We also describe a ramping test without beam that took place after the commissioning with beam. Finally, we analyze the implications of accelerator systems performance and their impact on the planning for RHIC installation and commissioning.

Injection choice for Spallation Neutron Source ring

Injection is key in the low-loss design of high-intensity proton facilities like the Spallation Neutron Source (SNS). During the design of both the accumulator and the rapid-cycling-synchrotron version of the SNS, extensive comparison has been made to select injection scenarios that satisfy SNSs low-loss design criteria. This paper presents issues and considerations pertaining to the final choice of the SNS injection systems.

RHIC sextant test-physics and performance

This paper presents beam physics and machine performance results of the Relativistic Heavy Ion Collider (RHIC) Sextant and AGS-to-RHIC (AtR) transfer line during the Sextant Test in early 1997. Techniques used to measure both machine properties (difference orbits, dispersion, and beamline optics) and beam parameters (energy, intensity, transverse and longitudinal emittances) are described. Good agreement was achieved between measured and design lattice optics. The gold ion beam quality was shown to approach RHIC design requirements.

Observation of Electron-Ion Effects at RHIC Transition

Electron cloud is found to be a serious obstacle on the upgrade path of the Relativistic Heavy Ion Collider (RHIC). At twice the design number of bunches, electron-ion interactions cause significant instability, emittance growth, and beam loss along with vacuum pressure rises when the beam is accelerated across the transition.

Beam dump optics for the spallation neutron source

The Spallation Neutron Source accelerator complex will have three beam dumps for beam tuning and for the collection of controlled losses. The linac and extraction beam dumps will be used for beam tuning purposes and are designed for 7.5 kW of beam power. The optics issues for these dumps are i) the beam size at the vacuum window which is near the last quadrupole and ii) guaranteeing the beam size at the dump due to multiple scattering in the presence of potentially large variations in the linac and accumulator ring emittances. The injection dump will collect the partially stripped H0 ions as well as H- ions which have miss the foil and is designed to absorb up to 200 kW of beam power. The closed orbit for these ions are much different in the injection area and have to be collected in the injection beam dump with a certain beam size

Evolution of the Spallation Neutron Source Ring Lattice

Requirements of minimum beam loss for hand‐on maintenance and flexibility for future operations are essential for the lattice design of the Spallation Neutron Source (SNS) accumulator ring. During the past seven years, the lattice has evolved from an all‐FODO to a FODO/doublet hybrid, the circumference has been increased to accommodate for a higher energy foreseen with a super‐conducting RF linac, and the layout has evolved from an α‐ to an Ω‐ geometry. Extensive studies are performed to determine working points that accommodate injection painting and minimize beam losses due to space charge and resonances. In this paper, we review the evolution of the SNS ring lattice and discuss the rationales.

Electron cloud observations and cures in RHIC

Since 2001 RHIC has experienced electron cloud effects, which have limited the beam intensity. These include dynamic pressure rises - including pressure instabilities, tune shifts, a reduction of the stability threshold for bunches crossing the transition energy, and possibly incoherent emittance growth. We summarize the main observations in operation and dedicated experiments, as well as countermeasures including baking, NEG coated warm beam pipes, solenoids, bunch patterns, anti-grazing rings, pre-pumped cold beam pipes, scrubbing, and operation with long bunches. This article is a short version of [1].