L. Snydstrup

The Brookhaven muon storage ring magnet

Abstract The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous g-value a μ (=(g−2)/2) to the very high precision of 0.35 parts per million and thus requires a storage ring magnet with great stability and homogeniety. A superferric storage ring with a radius of 7.11 m and a magnetic field of 1.45 T has been constructed in which the field quality is largely determined by the iron, and the excitation is provided by superconducting coils operating at a current of 5200 A. The storage ring has been constructed with maximum attention to azimuthal symmetry and to tight mechanical tolerances and with many features to allow obtaining a homogenous magnetic field. The fabrication of the storage ring, its cryogenics and quench protection systems, and its initial testing and operation are described.

The Brookhaven National Laboratory electron beam ion source for RHIC

As part of a new heavy ion preinjector that will supply beams for the Relativistic Heavy Ion Collider and the National Aeronautics and Space Administration Space Radiation Laboratory, construction of a new electron beam ion source (EBIS) is now being completed. This source, based on the successful prototype Brookhaven National Laboratory Test EBIS, is designed to produce milliampere level currents of all ion species, with q/m=(1/6)-(1/2). Among the major components of this source are a 5 T, 2-m-long, 204 mm diameter warm bore superconducting solenoid, an electron gun designed to operate at a nominal current of 10 A, and an electron collector designed to dissipate approximately 300 kW of peak power. Careful attention has been paid to the design of the vacuum system, since a pressure of 10(-10) Torr is required in the trap region. The source includes several differential pumping stages, the trap can be baked to 400 C, and there are non-evaporable getter strips in the trap region. Power supplies include a 15 A, 15 kV electron collector power supply, and fast switchable power supplies for most of the 16 electrodes used for varying the trap potential distribution for ion injection, confinement, and extraction. The EBIS source and all EBIS power supplies sit on an isolated platform, which is pulsed up to a maximum of 100 kV during ion extraction. The EBIS is now fully assembled, and operation will be beginning following final vacuum and power supply tests. Details of the EBIS components are presented.

RHIC EBIS: basics of design and status of commissioning

RHIC EBIS will be used for producing multicharged ions from helium to uranium using primary ions from various external ion sources. The EBIS is followed by an RFQ and short linac, forming the new preinjector which will produce beams used for physics at RHIC and the NASA Space Radiation Laboratory, The design of RHIC EBIS is based on the BNL Test EBIS, which was a successful 10A electron current prototype. Improvements have been made in the RHIC EBIS design to increase the capacity of the ion trap, repetition frequency of operation, electron current, acceptance for injected ions, and improve vacuum conditions in the ionization region. RHIC EBIS has been assembled and installed in its final position. Commissioning is now underway to reach its project parameters. The results of this commissioning stage are presented.

The Brookhaven muon (g-2) storage ring high voltage quadrupoles

The design, construction, and operation of the electrostatic quadrupoles used in the muon ðg � 2Þ experiment E821 of BNL are described in detail. A new lead design allowed the construction of a very reliable system which could operate for hundreds of thousands pulses with no sparking. The new design also made possible the elimination of systematic errors associated with the E; B fields generated by the low energy trapped electrons present in Penning traps under medium vacuum conditions. r 2003 Elsevier Science B.V. All rights reserved.

Design parameters for gas-cooled electrical leads of the g-2 magnets

This report presents the design parameters for a pair of 5300 A gas-cooled electrical leads for the g-2 solenoids and a pair of 2850 A leads for the inflector magnet. The lead design parameters are derived from a scale analysis of two one-dimensional, thermo-fluid-electro-quasi-coupled, and non-linear differential equations. The analysis may apply to general gas-cooled electrical lead design. As an illustration, these design parameters are applied to multi-tube gas-cooled leads that are proposed for the g-2 solenoid magnet system. Multiple electrical current carrying tubes and multiple gas flow cooling channels will increase the lead current capacity and lead efficiency for enhanced heat transfer and low flow pressure drop.

Brookhaven National Laboratory electron beam test stand

The main purpose of the electron beam test stand (EBTS) project at the Brookhaven National Laboratory is to build a versatile device to develop technologies that are relevant for a high intensity electron beam ion source (EBIS) and to study the physics of ion confinement in a trap. The EBTS will have all the main attributes of EBIS: a 1-m-long, 5 T superconducting solenoid, electron gun, drift tube structure, electron collector, vacuum system, ion injection system, appropriate control, and instrumentation. Therefore it can be considered a short prototype of an EBIS for a relativistic heavy ion collider. The drift tube structure will be mounted in a vacuum tube inside a “warm” bore of a superconducting solenoid, it will be at room temperature, and its design will employ ultrahigh vacuum technology to reach the 10−10 Torr level. The first gun to be tested will be a 10 A electron gun with high emission density and magnetic compression of the electron beam.

Cryogenics for the muon g-2 superconducting magnet system

Abstract The g-2 muon storage ring magnet system consists of four large superconductingsolenoids that are up to 15.1 m in diameter[1,2]. In addition there is a 1.8 meter long actively shielded inflector dipole that is to guide the beam into the storage ring. The g-2 superconducting magnets will be cooled using forced two-phase helium in tubes that is provided from the J-T circuit of a 625 W refrigerator. The two-phase helium flows from the refrigerator J-T circuit through a heat exchanger in a storage dewar that acts as a phase separator and a buffer for helium returning from the magnets. The g-2 magnet cooling system consists of three parallel two-phase helium flow circuits that provide cooling to. the four large superconducting solenoids, the current interconnects between the solenoids with the 5300 A solenoid gas cooled electrical leads, and the inflector dipole with its 2850 A gas cooled electrical leads.

Cryogenic tests of the g-2 superconducting solenoid magnet system

SC-HAG 525 LBL-37S02 CRYOGENIC TESTS OF THE g-2 SUPERCONDUCTING SOLENOID MAGNET SYSTEM L. X. Jia, J. R. Cullen Jr., A. J. Esper, R. E. Meier C. Pai, L. Snydstrup and T. Tallerico, Brookhaven National Laboratory Upton, NY 11973 M. A. Green E. O. Lawrence Berkeley National Laboratory Uni versity of California Berkeley, CA 94720 July 1995 * This work was performed at the Lawrence Berkeley Laboratory and at Brookhaven National Laboratory with the support of the Director of the Office of Energy Research, Office of High Energy and Nuclear Physics, High Energy Physics Division, United States Department of Energy under BNL contract number DE-AC02-76CHOOOI6 and LBL contract number DE-AC03-76SF00098.

An Ultra-Precise Storage Ring for the Muon g — 2 Measurement

An ultra precise 3 GeV/c storage ring with a 14.5 kG super-ferric magnet is under construction at the Brookhaven AGS for the measurement of the muon anomalous magnetic moment to 0.35 PPM accuracy. This requires a magnetic field which is constant to ≈ 1 PPM and is known sufficiently well that the magnetic field integral averaged over the muon orbits can be calculated to 0.1 PPM. First the magnetic field will be statically shimmed by various techniques. Pole face winding will be used for final small static and dynamic corrections. Very elaborate NMR field monitoring techniques are required. A “movable trolley” located inside the vacuum chamber and the electrostatic focusing quadrupoles will measure the field throughout the muon storage volume. The trolley “siding” is 180˚ from the injection point where no electric quadrupoles are located. Injection can be interrupted so the trolley can circle the ring. Also ≈ 200 NMR probes located outside the vacuum chamber monitor the field during physics running and control the pole face windings. The very large (≈ 15 m diameter) superconducting coils (SC) are designed. Test winding will soon commence. Orders for the magnet steel can now be placed. R and D on various pulsed and SC dc injection methods is ongoing.

Electron gun and collector simulations for RHIC EBIS at BNL

Based on the successful experience of the Brookhaven National Laboratory test electron beam ion sources (EBIS), the relativistic heavy ion collider (RHIC) EBIS design utilizes a 10 A electron beam to produce the required ion source output intensity of 3.4×109 of Au32+ ions per 10–40 μs pulse. In order to provide increased cathode lifetime and reliability at the required 10 A, and accommodate future upgrades of RHIC EBIS ion intensity, it is desirable to upgrade the electron gun. Simulations have been made for a new electron gun and electron collector capable of generating and dissipating an electron beam with current up to 20 A. The method of forming the electron beam using magnetic compression and inverse magnetron geometry of the electron gun are the same as has been tested successfully on the electron beam test stand. The new gun has higher perveance and partially shielded spherical cathode. A bell-shaped radial current density distribution with reduced current density on a periphery of the beam, combi...