[show abstract][hide abstract] ABSTRACT: 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.
The Review of scientific instruments 02/2010; 81(2):02A509. · 1.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: A gas fluorescence beam profile monitor has been implemented at the relativistic heavy ion collider (RHIC) using the polarized atomic hydrogen gas jet, which is part of the polarized proton polarimeter. RHIC proton beam profiles in the vertical plane of the accelerator are obtained as well as measurements of the width of the gas jet in the beam direction. For gold ion beams, the fluorescence cross section is sufficiently large so that profiles can be obtained from the residual gas alone, albeit with long light integration times. We estimate the fluorescence cross sections that were not known in this ultrarelativistic regime and calculate the beam emittance to provide an independent measurement of the RHIC beam. This optical beam diagnostic technique, utilizing the beam induced fluorescence from injected or residual gas, offers a noninvasive particle beam characterization and provides visual observation of proton and heavy ion beams.
The Review of scientific instruments 11/2008; 79(10):105103. · 1.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: A hydrogen jet polarimeter was developed for the RHIC accelerator to improve the process of measuring polarization. Particle beams intersecting with gas molecules can produce light by the process known as luminescence. This light can then be focused, collected, and processed giving important information such as size, position, emittance, motion, and other parameters. The RHIC hydrogen jet polarimeter was modified in 2005 with specialized optics, vacuum windows, light transport, and a new camera system making it possible to monitor the luminescence produced by polarized protons intersecting the hydrogen beam. This paper describes the configuration and preliminary measurements taken using the RHIC hydrogen jet polarimeter as a luminescence monitor.
[show abstract][hide abstract] ABSTRACT: 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 , 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.
Review of Modern Physics 01/2007; 10(2). · 44.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: The polarized hydrogen Jet target at RHIC continues its mission to provide absolute calibration for the polarized proton beam polarimeters at RHIC. Data were collected at incoming beam momenta of 100, 24, and 32 GeV/c respectively. The statistical and systematic accuracy of the jet data at 100 GeV/c achieved its goal of statistical accuracy of measuring the beam polarization to 3% in Run 5. Attempts at reducing the jet systematic uncertainty due to molecular hydrogen are also described.
[show abstract][hide abstract] ABSTRACT: A new ion pre-injector line is currently under design at Brookhaven National Laboratory (BNL) for the Relativistic Heavy Ion Collider (RHIC) and the NASA Space Radiation Laboratory (NSRL). Collectively, this new line is referred to as the EBIS project. This pre-injector is based on an Electron Beam Ion Source (EBIS), a Radio Frequency Quadrupole (RFQ) accelerator, and a linear accelerator. The new EBIS will be able to produce a wide range of heavy ion species as well as rapidly switching between species. To aid in operation of the pre-injector line, a suite of diagnostics is currently proposed which includes faraday cups, current transformers, profile monitors, and a pepperpot emittance measurement device.
[show abstract][hide abstract] ABSTRACT: The Brookhaven 200MeV linac is a multipurpose machine used to inject low intensity polarized protons for RHIC (Relativistic Heavy Ion Collider), as well as to inject high intensity protons to BLIP (Brookhaven Linac Isotope Producer), a medical isotope production facility. If high intensity protons were injected to RHIC by mistake, administrative radiation limits could be exceeded or sensitive electronics could be damaged. In the past, the changeover from polarized proton to high intensity proton operation has been a lengthy process, thereby never allowing the two programs to run simultaneously. To remedy this situation and allow concurrent operation of RHIC and BLIP, an active interlock system has been designed to monitor current levels in the AGS using two current transformers with fail safe circuitry and associated electronics to inhibit beam to RHIC if high intensity currents are detected.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
[show abstract][hide abstract] ABSTRACT: The secondary particle focusing horn for the AGS neutrino experiment proposal is a high current and high current density device. The peak current of horn is 300 kA. At the smallest area of horn, the current density is near 8 kA/mm<sup>2</sup>. At very high current density, a few kA/mm<sup>2</sup>, the electromigration phenomena will occur. Momentum transfer between electrons and metal atoms at high current density causes electromigration. The reliability and lifetime of focusing horn can be severely reduced by electromigration. In this paper, we discuss issues such as device reliability model, incubation time of electromigration, and lifetime of horn.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
[show abstract][hide abstract] ABSTRACT: Thermodynamic studies have been performed for the beam target and focusing horn system to be used in a very long baseline neutrino oscillation experiment . A 2mm rms beam spot with power deposition of over 18 KW presents challenging material and engineering solutions to this project. Given that the amount of heat transferred by radiation alone from the target to the horn is quite small, the primary mechanism is heat removal by forced convection in the annular space between the target and the horn. The key elements are the operating temperature of the target, the temperature of the cooling fluid and the heat generation rate in the volume of the target that needs to be removed. These working parameters establish the mass flow rate and velocity of the coolant necessary to remove the generated heat. Several cooling options were explored using a carbon-carbon target and aluminum horn. Detailed analysis, trade studies and simulations were performed for cooling the horn and target with gaseous helium as well as water.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
[show abstract][hide abstract] ABSTRACT: Table 1: AGS Proton Driver Parameters. Total beam power 1 MW Beam energy 28 GeV Average beam current Cycle time Number of protons per fill Number of bunches per fill Protons per bunch Injection turns Repetition rate Pulse length Chopping rate Linac average/peak current 42 µA 400 msec 0.9 x 10 14 24 0.4 x10 13 230 2.5 Hz 0.72 msec 0.75 20 / 30 mA A very long base line super neutrino beam facility is needed to determine the neutrino mixing amplitudes accurately, as well as measure the CP violation phase angle. This is possible due to the long distance and wideband nature of the neutrino beam for the observation of several oscillations from one species of the neutrino to the other. BNL plans to upgrade the AGS proton beam from the current 0.14 MW to higher than 1.0 MW and beyond for such a neutrino facility which consists of three major subsystems. First is a 1.2 GeV superconducting linac (SCL) to replace the booster as injector for the AGS, second is the performance upgrade for the AGS itself for the higher intensity and repetition rate, and finally is the target and horn system for the neutrino production. The major contribution for the higher power is from the increase of the repetition rate of the AGS from 0.3 Hz to 2.5 Hz, with moderate increase in the intensity. Present injection into the AGS requires the accumulation of four Booster loads in the AGS which takes about 0.6 sec, and is therefore not suited for high average beam power operation. To reduce the injection time to about 1 msec, the booster will be replaced by a 1.2GeV linac. The injection linac consists of the existing warm linac of 200 MeV and a new superconducting linac to 1.2 GeV. The multi-turn injection from a source of 28 mA and 720 µsec pulse width is sufficient to accumulate 0.9×10 14 particle per pulse in the AGS. The minimum ramp time of the AGS to full energy is presently 0.5 sec. This must be reduced to 0.2 sec to reach the required repetition rate of 2.5 Hz to deliver the required 1 MW beam to the target. The design consideration to achieve high intensity and low losses for the linac and the AGS will be reviewed. The target-horn design for high power operation and easy maintenance will also be presented.
[show abstract][hide abstract] ABSTRACT: 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.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
[show abstract][hide abstract] ABSTRACT: A new experimental facility being at built at BNL will take advantage of heavy-ion beams from the AGS Booster for radiation effects studies of importance for the Space Program. A large dynamic range response is necessary to accommodate a wide variety of species (protons to gold) and energies (100 MeV/amu to 1.3 GeV/amu). The instrumentation proposed for extraction control and transport diagnostics will include phosphor screens with video cameras, segmented wire ionization chambers, ion chambers, and scintillators. Design and development of these systems will be presented.
[show abstract][hide abstract] ABSTRACT: At Brookhaven National Laboratory there is an R&D program to
design an Electron Beam Ion Source (EBIS) for use in a compact ion
injector to be developed for the Relativistic Heavy Ion Collider (RHIC).
The BNL effort is directed at developing an EBIS with intensities of
3×10<sup>9</sup> particles/pulse of ions such as Au<sup>35+</sup>
and U<sup>45+</sup>, and requires an electron beam on the order of 10 A.
The construction of a test stand (EBTS) with the full electron beam
power and 1/3 the length of the EBIS for RHIC is nearing completion.
Initial commissioning of the EBTS was made with pulsed electron beams of
duration <1 ms and current up to 13 A. Details of the EBTS
construction, results of the pulse tests, and preparations for DC
electron beam tests are presented
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
[show abstract][hide abstract] ABSTRACT: A fundamental power coupler (FPC) is designed to provide fast tuning the 56MHz SRF cavity in RHIC. The FPC will be inserted from one of the chemical cleaning ports at the rear end of the cavity with magnetic coupling to the RF field. The size and the location of the FPC are decided based on the required operational external Q of the cavity. The cavity is beam driven, and the FPC is designed with variable coupling that would cover a range of power levels. It is thermally isolated from the base temperature of the cavity, which is 4.2K. A 1kW power amplifier will be used to close an amplitude control feedback loop. In this paper, we discuss the coupling factor of the FPC with the chosen design.
[show abstract][hide abstract] ABSTRACT: Relativistic Heavy Ion Collider (RHIC) beams are subject to Intra-Beam Scattering (IBS) that causes an emittance growth in all three-phase space planes. The only way to increase integrated luminosity is to counteract IBS with cooling during RHIC stores. A stochastic cooling system for this purpose has been developed, it includes moveable pick-ups and kickers in the collider that require precise motion control mechanics, drives and controllers. Since these moving parts can limit the beam path aperture, accuracy and reliability is important. Servo, stepper, and DC motors are used to provide actuation solutions for position control. The choice of motion stage, drive motor type, and controls are based on needs defined by the variety of mechanical specifications, the unique performance requirements, and the special needs required for remote operations in an accelerator environment. In this report we will describe the remote motion control related beam line hardware, position transducers, rack electronics, and software developed for the RHIC stochastic cooling pick-ups and kickers.
[show abstract][hide abstract] ABSTRACT: The EBIS Project at Brookhaven National Laboratory will replace the Tandem Van de Graaff accelerators with an Electron Beam Ion Source, an RFQ, and short linac, as the heavy ion preinjector for RHIC. This project, jointly funded by DOE and NASA, will provide a modern preinjector which will have increased flexibility in providing beams to the various programs running simultaneously, will be capable of providing beams not presently available for RHIC and the NASA Space Radiation Laboratory, and will be simpler and less costly to operate. Presently in the first year of the four- year project, the detailed design is nearly complete, and some major procurements have been placed. The overall status of the project is presented, as well as some unique features in the design, and discussion of the R&D using the prototype EBIS.
[show abstract][hide abstract] ABSTRACT: A new luminescence beam profile monitor is realized in the polarized hydrogen gas jet target at the Relativistic Heavy Ion Collider (RHIC) facility. In addition to the spin polarization of the proton beam being routinely measured by the hydrogen gas jet, the luminescence produced by beam-hydrogen excitation leads to a strong Balmer series lines emission. A selected hydrogen Balmer line is spectrally filtered and imaged to produce the transverse RHIC proton beam shape with unprecedented details on the RHIC beam profile. Alternatively, when the passage of the high energy RHIC gold ion beam excited only the residual gas molecules in the beam path, sufficient ion beam induced luminescence is produced and the transverse gold ion beam profile is obtained. The measured transverse beam sizes and the calculated emittances provide an independent confirmation of the RHIC beam characteristics and to verify the emittance conservation along the RHIC accelerator. This optical beam diagnostic technique by making use of the beam induced fluorescence from injected or residual gas offers a truly noninvasive particle beam characterization, and provides a visual observation of proton and heavy ion beams. Combined with a longitudinal bunch measurement system, a 3-dimensional spatial particle beam profile can be reconstructed tomographically.
[show abstract][hide abstract] ABSTRACT: At each injection period during RHIC's operation, the beam's frequency sweeps across a wide range, and some of its harmonics will cross the frequency of the 56MHz SRF cavity. To avoid excitation of the cavity at these times, we designed a fundamental damper for the quarter-wave resonator to damp the cavity heavily. The power extracted by the fundamental damper should correspond to the power handling ability of the system at all stages. In this paper, we discuss the power output from the fundamental damper when it is fully extracted, inserted, and any intermediate point. A Fundamental Damper (FD) will greatly reduce the cavity's Q factor to 300 during the acceleration phase of the beam. However, when the beam is at store and the FD is removed, the cavity is excited by both the yellow and the blue beams at 2 x 0.3A to attain the required 2MV voltage across its gap. The cavity then is operated to increase the luminosity of the RHIC experiments. Table 1 lists the parameters of the FD. Figure 1 shows the configuration of the FD fully inserted into the 56MHz SRF cavity; this complete insertion is defined as the start location (0cm) of FD simulation, an assumption we make throughout this paper. The power consumed by the cavity while maintaining the beam's energy and its orbit is compensated by the 28MHz accelerating cavities in the storage ring. The power dissipation of the external load is dynamic with respect to the position of the FD during its extraction. As a function of the external Q and the EM field in the cavity, the power should peak with the FD at a certain vertical location. Our calculation of the power extracted is detailed in the following sections. Figure 2 plots the frequency change in the cavity, and the external Q against the changes in position of the FD. The location of the FD is selected carefully such that the frequency will approach the designed working point from the lower side only. The loaded Q of the cavity is 223 when the FD is fully inserted. The simulation was carried out with Microwave Studio 2010.