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Successful operation of the BNL EBIS with electron current up to 10 A provides optimism that EBIS operation with even higher electron current should be possible. We are now considering key aspects of the design for an EBIS operating with electron current 20 A. Several technical problems need to be resolved, including generation of a 20 A electron beam and dissipation of this electron beam power on the electron collector. Since we already have a tested concept of electron beam generation with the gun immersed in a magnetic field and subsequent purely magnetic compression of the electron beam, it makes sense to develop the new electron gun with immersed cathode but with higher perveance. To distribute the electron beam power on the surface of the electron collector more evenly, the emission current density from the cathode can be made bell-shaped with minimum close to zero on the periphery of the electron beam. With the already high requirements to the emission current density, and since such shaping of the electron beam makes these requirements even higher, perhaps the only available cathode material that can satisfy these requirements is IrCe. The problems of power dissipation on the electron collector (EC) include heat removal with cooling water and fatigue of the EC material. The first step in the EC design was electron beam transmission simulation with the goal to reduce `spikes' of power density on EC surface as much as possible. With the geometry of EC thus defined, the conditions of heat exchange for several modes of EBIS operation have been analyzed and cooling parameters, which provide adequate heat removal were found. The last step was stress analysis of several EC materials with ANSYS to find the material suitable for this application. Details of the 20 A electron gun and collector are presented.

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.

The muon g-2 experiment at Brookhaven has successfully completed two exploratory runs using pion injection and direct muon injection for checkout and initial data taking. The main components of the experiment, which include the pion beam line, the superconducting storage ring and inflector magnets, the muon kicker and the lead-scintillating fiber calorimeters have been satisfactorily commissioned. First results on the anomalous magnetic moment of the positive muon from pion injection are in good agreement with previous experimental results for a(mu+) and a(mu-) from CERN and of comparable accuracy (13 ppm). Analysis of the 1998 muon injection run is in progress and expected to improve the precision to about 4 ppm. A first production run is scheduled for January 1999 with the goal of reaching the 1 ppm error level.

The g-2 experiment dipole consists of a single 48 turn, 15.1 meter diameter outer solenoid and a pair of 24 turn inner solenoids, 13.4 meters in diameter. The inner solenoids are hooked in series and are run at a polarity that is opposite that of the outer solenoid, thus creating a dipole field in the space between the inner and outer solenoids. The dipole flux is returned by a C shaped continuous iron yoke. The superconducting solenoid coils are closely coupled to the solenoid mandrels and as such are subject to quench back. This report presents the results of various tests on the g-2 magnet system operating within its iron return yoke. These tests include quench back time constant measurements for the inner and outer solenoids and measurements of the response of the two-phase forced cooled helium cryogenic system to magnet quenches. The overall effectiveness of the g-2 magnet quench protection system was measured.

A US-Japan collaboration for the high energy physics experiment DeeMe requires a multi GVA high deflection strength fast kicker system. A set of high current, high voltage and high power generators are going to drive a series of kicker magnets to deflect passing beam. Brookhaven researchers have been invited to conduct a conceptual design study for this challenging project. The basic option consists of a set of identical modulators, low impedance transmission lines, and large aperture high inductance kicker magnets. Each modulator shall be capable of driving the kicker magnet with an 8kA to 10kA pulsed current. A desired fast pulse fall time of 300 to 400 ns is the most challenging part of the design because of the high inductance magnetic load. The after pulse floor ripple tolerance is 5% or best achievable. Pulse repetition rate is 25Hz continuously. We have evaluated a wide range of pulsed power technology options and concluded that the requirement is beyond the state of the art for fast kicker technology. However, a near perfect solution is possible. We proposed several options in the conceptual design for the best achievable technical solution. In this paper, we present the technology overview, design comparisons, and the areas requiring advanced research and development effort.

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...

The g-2 muon storage ring at Brookhaven National Laboratory consists of four large superconducting solenoids. The two outer solenoids, which are 15.1 meters in diameter, share a common cryostat. The two inner solenoids, which are 13.4 meters in diameter, are in separate cryostats. The two 24 turn inner solenoids are operated at an opposite polarity from the two 24 turn outer solenoids. This generates a dipole field between the inner and outer solenoids. The flux between the solenoids is returned through a C shaped iron return yoke that also shapes the dipole field. The integrated field around the 14 meter diameter storage ring must be good to about 1 part in one million over the 90 mm dia. circular cross section where the muons are stored, averaged over the azimuth. When the four solenoids carry their 5300 A design current, the field in the 18 centimeter gap between the poles is 1.45 T. When the solenoid operates at its design current 5.5 MJ is stored between the poles. The solenoids were wound on site at Brookhaven National Laboratory. The cryostats were built around the solenoid windings which are indirectly cooled using two-phase helium. >

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.

The four electron stripping stages leading to fully stripped gold ions in the Relativistic Heavy Ion Collider (RHIC) are briefly described. The third stripper, which removes 46 electrons from the ${\mathrm{Au}}^{31+}$ ions leading to heliumlike ${\mathrm{Au}}^{77+}$, offers the greatest challenges in terms of energy loss and induced energy spread. These problems are described in detail as well as recent advances in the design and performance of this stripper. Measurements performed with several carbon and aluminum strippers show general agreement with a semiempirical model but small systematic deviations suggest that some model adjustments may be in order. The best performance is predicted and obtained with a combined carbon-aluminum foil system. Measurements showing the enhanced performance in the alternating gradient synchrotron are described. The stripper that removes the last two electrons has also been improved and the results of relevant calculations and measurements are presented.

A part of a new EBIS-based heavy ion preinjector, the low energy beam transport (LEBT) section between the high current EBIS and the RFQ is a challenging design, because it must serve many functions. In addition to the requirement to provide an efficient matching between the EBIS and the RFQ, this line must serve as a fast "switchyard", allowing singly charged ions from external sources to be transported into the EBIS trap region, and extracted, highly charged ions to be deflected to off-axis diagnostics (time-of-flight or emittance). The space charge of the 5-10 mA extracted heavy ion beam is a major consideration in the design, and the space charge force varies for different ion beams having Q/m from 1-0.16. The line includes electrostatic lenses, spherical and parallel-plate deflectors, magnetic solenoid, and diagnostics for measuring current, charge state distributions, emittance, and profile. A prototype of this beamline has been built, and results of tests are presented.

Errors in delivering a uniformly distributed radiation dose to biological and material samples exposed to charged particle beams are a significant problem for experimenters. In this paper, we discuss data collected on the uniform beam distributions produced for NASA’s Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), using a method that was conceived theoretically and tested experimentally at BNL. This method [N. Tsoupas et al., Nucl. Sci. Eng. 126, 71 (1997)NSENAO0029-5639] of generating uniform beam distributions on a plane normal to the beam’s direction relies only on magnetically focusing the transported beam; no collimation of the beam is required or any other type of interaction of the beam with materials other than the target material. The method compares favorably with alternative methods of producing such distributions, and it can be applied to the entire energy spectrum of charged particle beams that are delivered to the NSRL’s experiments by the Booster for the Alternating Gradient Synchrotron at BNL.

The new EBIS preinjector at BNL will accelerate ions from the EBIS source with specific mass to charge ratio of up to 6.25, from 17 keV/u to 2000 keV/u to inject into the Booster synchrotron, expanding experimental possibilities for RHIC and NASA experiments. The properties of the RFQ and IH accelerators and the status of the project will be discussed.

An electron beam ion source (EBIS), capable of producing high charge states and high beam currents of any heavy ion species in short pulses, is ideally suited for injection into a synchrotron. An EBIS-based, high current, heavy ion preinjector is now being built at Brookhaven to provide increased capabilities for the Relativistic Heavy Ion Collider (RHIC), and the NASA Space Radiation Laboratory (NSRL). Benefits of the new preinjector include the ability to produce ions of any species, fast switching between species to serve the simultaneous needs of multiple programs, and lower operating and maintenance costs. A state-of-the-art EBIS, operating with an electron beam current of up to 10 A, and producing multi-milliamperes of high charge state heavy ions, has been developed at Brookhaven, and has been operating very successfully on a test bench for several years. The present performance of this high- current EBIS is presented, along with details of the design of the scaled-up EBIS for RHIC, and the status of its construction. Other aspects of the project, including design and construction of the heavy ion RFQ, Linac, and matching beamlines, are also mentioned.

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.

Work is continuing on the development of an Electron Beam Ion Source (EBIS) which could be used as part of a new heavy ion injector for RHIC. On a test EBIS, we have operated with an electron beam current of up to 1.14 A, and have extracted ions such as Tl/sup 41+/, Xe/sup 26+/, Ar/sup 14+/, N/sup 7+/, and Na/sup 7+/. Recent experimental results are reported. In addition, we discuss plans for a new electron beam test stand that is now being built. This will allow operation with electron currents of 10 A, as well as testing of a warm-bore superconducting magnet system, methods for fast extraction of ions, and possible off-axis collection of the electron beam.

The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous g-value a(mu) ( = (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. (C) 2001 Elsevier Science B.V. All rights reserved.

Brookhaven's AGS Booster is the injector for the AGS. It is being modified to send resonant extracted heavy ions to a new beam line, the Booster Applications Facility (BAF). The design of the resonant extraction system for BAF was described previously. This note will give a more detailed description of the system and describe the predicted resonant beam time structure. We will describe tune space manipulations necessary to extract the resonant beam at the maximum Booster rigidity, schemes for performing resonant extraction, and describe the modifications required to perform bunched beam extraction to the BAF facility.

The muon (g−2) experiment at Brookhaven has just completed a 3-month run for checkout and initial data-taking. In the first two months beam was taken in a parasitic mode where one out of ten AGS pulses was delivered for commissioning of the beam line, quadrupoles, detectors, and data acquisition system. This was followed by four weeks of dedicated data collection. The main components of the experiment, which include the pion/muon beam line, the superconducting inflector, the superferric storage ring with its pulsed electric quadrupoles and magnetic field measurement system, and the detector system based on lead-scintillating fiber electron calorimeters, have been satisfactorily commissioned. The muon (g−2) precession frequency is clearly seen as a large signal. It is estimaed that over 25×106 decay positrons with energies greater than 1.5 GeV have been detected.

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.

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 {approx} 300 kW of peak power. Careful attention has been paid to the design of the vacuum system, since a pressure of 10{sup -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. Themore » 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.« less

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.

Brookhaven's AGS Booster has been modified to deliver slow extracted beam to a new beam line, the NASA Space Radiation Laboratory (NSRL). This facility was constructed in collaboration with NASA for the purpose of performing radiation effect studies for the NASA space program. The design of the resonant extraction system has been described. A more detailed description, which includes predictions of the slow extracted beam time structure has been described. In this report we present results of the system commissioning and performance.