[Show abstract][Hide abstract] ABSTRACT: The Spallation Neutron Source (SNS) was designed and constructed by a collaboration of six U.S. Department of Energy national laboratories. The SNS accelerator system consists of a 1 GeV linear accelerator and an accumulator ring providing 1.4 MW of proton beam power in microsecond-long beam pulses to a liquid mercury target for neutron production. The accelerator complex consists of a front-end negative hydrogen-ion injector system, an 87 MeV drift tube linear accelerator, a 186 MeV side-coupled linear accelerator, a 1 GeV superconducting linear accelerator, a 248-m circumference accumulator ring and associated beam transport lines. The accelerator complex is supported by ~ 100 high-power RF power systems, a 2 K cryogenic plant, ~ 400 DC and pulsed power supply systems, ~ 400 beam diagnostic devices and a distributed control system handling ~ 100,000 I/O signals. The beam dynamics design of the SNS accelerator is presented, as is the engineering design of the major accelerator subsystems.
Full-text · Article · Nov 2014 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: To compensate for the beam–beam effects from the proton–proton interactions at the two interaction points IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC), we are constructing two electron lenses (e-lenses) that we plan to install in the interaction region IR10. Before installing them, the electron gun, collector, instrumentation were tested and the electron beam properties were qualified on an electron lens test bench. We will present the test results and discuss our measurement of the electron beam current and of the electron gun perveance. We achieved a maximum current of 1 A with 5 kV energy for both the pulsed- and the DC-beam (which is a long turn-by-turn pulse beam). We measured beam transverse profiles with an yttrium aluminum garnet (YAG) screen and pinhole detector, and compared those to simulated beam profiles. Measurements of the pulsed electron beam stability were obtained by measuring the modulator voltage.
No preview · Article · Apr 2014 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
[Show abstract][Hide abstract] ABSTRACT: In the 2012 RHIC heavy ion run, we collided uraniumuranium
(U-U) ions at 96.4 GeV/nucleon and copper-gold
(Cu-Au) ions at 100 GeV/nucleon for the first time in
RHIC. The new Electron-Beam Ion Source (EBIS) was
used for the first time to provide ions for the RHIC physics
program. After adding the horizontal cooling, 3-D stochastic
cooling became operational in RHIC for the first time,
which greatly enhanced the luminosity. With a double
bunch merging technique in the Booster and AGS, the
bunch intensities of Cu and Au ions in RHIC surpassed
their projections. Both PHENIX and STAR detectors
reached their integrated luminosity goals for both U-U and
Cu-Au collisions. In this article we review the machine
improvements and performances in this run.
[Show abstract][Hide abstract] ABSTRACT: In the 2013 RHIC polarized-proton run, it was found that the intensity of the RHIC bunch had reached a limit due to the head-on beam-beam interaction at intensity of 2x10 11 , as we expected from our simulations . To overcome this limitation, we have planned to implement two electron lenses for beam-beam compensation. During and after the 2013 RHIC run, some e-lens systems were commissioned. The effect of the e-lens warm solenoids on the protons orbit was observed and corrected by orbit feedback. The blue electron-lens system was fully tested, except for the superconducting magnet; the electron beam was propagated from the gun to the collector, and most of the instrumentation for the blue e-lens was commissioned. The straightness of the superconducting solenoid #2 field was measured for the first time. The installation of the yellow e-lens system and two superconducting magnets are underway.
[Show abstract][Hide abstract] ABSTRACT: We conduct a proof-of-the-principle experiment of coherent electron cooling (CEC), that potentially wil significantly boost the luminosity of high-energy, high-intensity hadron colliders . Herein, we discuss the current status of the experimental equipment, detailing our first tests of the electron gun and the results of magnetic measurements of the wiggler prototype. We describe the current status of the design, and our near-future plans.
[Show abstract][Hide abstract] ABSTRACT: We are preparing for the proof-of-the-principle experiment of coherent electron cooling (CeC), to test the technique with a potential of significant boost in luminosity of high-energy, high-intensity hadron colliders . In this paper, we report on the progress with the procurement, testing and installing the experimental equipment, including the first tests of the electron gun and the magnetic measurements of the wiggler prototype. We describe the current design, the status of the project, as well as, our plans.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: A high voltage modulator has been built and tested at Brookhaven National Laboratory. Its function is to drive the gun anode of the RHIC Electron Lens(elens). It is capable of outputting a square wave of 10kV and a continuous rep rate of 80kHz. The pulse width is continuously adjustable from 500ns to DC. The rise time and the fall time (10%-90%) are under 50ns.
[Show abstract][Hide abstract] ABSTRACT: We present in this paper our research and development of accelerator fast kicker with a solid state FID pulse generator. This is the first attempt to test a high strength fast kicker with a nano-second high pulse power generator for large hadron accelerators and colliders. The FID pulse generator features a 10 ns pulse rise time (2%-98%), 30ns pulse fall time, 50 ns flat top pulse duration, 100 Hz repetition rate, and peak amplitude of 50 kV and 1.0 kA. We have successfully tested the system with long length transmission cable, RHIC injection kicker magnet, matched and mismatched resistive load. The pulse generator is ultra compact and its size is comparable to a digital oscilloscope. The existing RHIC injection kicker system has four oil filled tri-axial Blumlein generators occupying a floor space of about 1000 square feet. A set of four FID pulse generators would fit into a single rack. It has a potential space saving of 50 to 100 times. Another advantage is its ultra fast current slew rate surpassing the thyratron and traditional modulator system. The technology is impressive and results are encouraging.
[Show abstract][Hide abstract] ABSTRACT: In order to increase the polarized proton luminosities, a new E-LENS system will be installed in RHIC tunnel. One of the key parts of this project is achieve a fast rise time for elens electron gun. The electron gun is driven by a fast high voltage rise time and high pulse repetition rate anode modulator. This paper will discuss some details of the modulator design concept and its simulation, problems during the test, modulator scheme modification and new modulator scheme prototype test results. Meanwhile, some test diagrams, prototype pictures and measured waveforms will be shown in the paper. The prototype test has reached the specification requirement of the modulator. The output high voltage is 10 kV, HV pulse rise and fall time is about 50nS (10%-90%) and the pulse repetition rate has reached 80 kHz.
[Show abstract][Hide abstract] ABSTRACT: Our recent effort to test a 50 kV, 1 kA, 50 ns pulse width, 10 ns pulse rise time FID pulse generator with a 250 ft transmission cable, resistive load, and existing RHIC injection kicker magnet has produced unparalleled results. This is the very first attempt to drive a high strength fast kicker magnet with a nano second high pulsed power (50 MVA) generator for large accelerator and colliders. The technology is impressive. We report here the result and future plan of RHIC Injection kicker upgrade.
[Show abstract][Hide abstract] ABSTRACT: To compensate for the beam-beam effects from the proton-proton interactions at IP6 andIP8 in the Relativistic Heavy Ion Collider (RHIC), we are fabricating two electron lensesthat we plan to install at RHIC IR10. Before installing the e-lenses, we are settingup thee-lens test bench to test the electron gun, collector, GS1 coil, modulator, partial controlsystem, some instrumentation, and the application software. Some elens power supplies, theelectronics for current measurement will also be qualified on test bench. The test benchalso was designed for measuring the properties of the cathode and the profile of the beam.In this paper, we introduce the layout and elements of the e-lens test bench; and wediscuss its present status towards the end of this paper.
[Show abstract][Hide abstract] ABSTRACT: Through more than a decade of operation, we have noticed the phenomena of beam loss induced kicker instability in the RHIC beam abort systems. In this study, we analyze the short term beam loss before abort kicker pre-fire events and operation conditions before capacitor failures. Beam loss has caused capacitor failures and elevated radiation level concentrated at failed end of capacitor has been observed. We are interested in beam loss induced radiation and heat dissipation in large oil filled capacitors and beam triggered thyratron conduction. We hope the analysis result would lead to better protection of the abort systems and improved stability of the RHIC operation.
[Show abstract][Hide abstract] ABSTRACT: Over the last few years, physicists have occasionally observed the presence of noise acting on the RHIC beams leading to emittance growth at high beam energies. While the noise was sporadic in the past, it became persistent during the Run-11 setup period. An investigation diagnosed the source as originating from the RHIC dump kicker system. Once identified the issue was quickly resolved. We report in this paper the investigation result, circuit analysis, measured and simulated waveforms, solutions, and future plans.
[Show abstract][Hide abstract] ABSTRACT: Following the Fiscal Year (FY) 2010 (Run-10) Relativistic Heavy Ion Collider (RHIC) Au+Au run, RHIC experiment upgrades sought to improve detector capabilities. In turn, accelerator improvements were made to improve the luminosity available to the experiments for this run (Run-11). These improvements included: a redesign of the stochastic cooling systems for improved reliability; a relocation of 'common' RF cavities to alleviate intensity limits due to beam loading; and an improved usage of feedback systems to control orbit, tune and coupling during energy ramps as well as while colliding at top energy. We present an overview of changes to the Collider and review the performance of the collider with respect to instantaneous and integrated luminosity goals. At the conclusion of the FY 2011 polarized proton run, preparations for heavy ion run proceeded on April 18, with Au+Au collisions continuing through June 28. Our standard operations at 100 GeV/nucleon beam energy was bracketed by two shorter periods of collisions at lower energies (9.8 and 13.5 GeV/nucleon), continuing a previously established program of low and medium energy runs. Table 1 summarizes our history of heavy ion operations at RHIC.
[Show abstract][Hide abstract] ABSTRACT: A horizontal tune jump system has been installed to overcome the horizontal intrinsic spin resonances, which requires jumping the horizontal tune 0.04 units 82 times, 41 up and 41 down. Two quadruple magnets have been installed in AGS ring to perform this. The pulsed magnet current ranges from about 140A near injection to about 1400A later. The current pulse rise and fall time are around 100uS and flat tops time is around 4mS. These quadruples have separated supplies. This tune jump pulse power supply employees all semiconductor parts as well as the main switches. During dummy load and magnet testing, the test results showed that the power supply could meet the specification. This article will describe some details of power supply simulation, design and testing. Some test waveforms and pictures are presented in this paper.
[Show abstract][Hide abstract] ABSTRACT: We present a design of the ion Rapid Cycling Medical Synchrotron (iRCMS) for carbon/proton cancer therapy facility. The facility design, produced at Brookhaven National Laboratory (BNL) at the Collider Accelerator Department (CAD), with BEST Medical International, Inc., will be able to treat the cancer patients with carbon, lighter ions and protons. The low energy injector system accelerates ions and protons to the kinetic energy of 8 MeV/u. It consists of a laser driven ion source (for either fully stripped carbon ions or protons), matching solenoid, Radio-Frequency Quadrupole (RFQ) and linac. The 8 MeV beam is injected into a fast cycling synchrotron (iRCMA). The lattice design is a racetrack, with zero dispersion with two parallel straight sections. There are 24 combined function magnets in the two arcs with a bending radius of ~5 meters and maximum magnetic field of B max ~1.3 T. The acceleration is performed with a frequency of 30 Hz up to required energy for the treatment with a maximum depth of 27 cm with the spot scanning technique. The maximum energy for carbon ions is 400 MeV/u. Ions are extracted in a single turn and fed to different beam lines for patient treatment.
[Show abstract][Hide abstract] ABSTRACT: This power supply was designed and developed at Brookhaven National Laboratory (BNL) as part of a new ion preinjector system called EBIS (Electron Beam Ion Source). It consists of a charging power supply, a capacitor bank, a discharge and recovery circuit and control circuits. The output is fed through cables into a solenoid magnet. The magnet's inductance is 1.9mH. The maximum charging voltage is 1000V. The power supply output is a half sine wave of 13ms duration. The repetition rate is 5Hz. The power supply output can be set to any value between 250A and 1900A in one second in order to accommodate the varying species of ions specified by different machine users.
[Show abstract][Hide abstract] ABSTRACT: Since the last successful RHIC Au+Au run in 2007 (Run-7), the RHIC experiments have made numerous de-tector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant in-crease in luminosity is essential. In Run-7 RHIC achieved an average store luminosity of < L >= 12 × 10 26 cm −2 s −1 by operating with 103 bunches (out of 111 possible), and by squeezing to β * = 0.85 m. This year, Run-10, we achieved < L >= 20 × 10 26 cm −2 s −1 , which put us an order of magnitude above the RHIC design luminosity. To reach these luminosity levels we decreased β * to 0.75 m, operated with 111 bunches per ring, and reduced longitudi-nal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF control system, and separated transition crossing times in the two rings. We present an overview of the changes and the results of Run-10 performance.
[Show abstract][Hide abstract] ABSTRACT: In order to cross more rapidly the 82 weak spin resonances caused by the horizontal tune and the partial snakes, we plan to jump the horizontal tune 82 times during the acceleration of polarized protons. The current in the magnets creating this tune jump will rise in 100 s, hold flat for about 4 ms and fan to zero in 100 s. Laminated beam transport quadrupole magnets have been recycled by installing new two turn coils and longitudinal laminated pole tip shims that reduce inductance and power supply current. The power supply uses a high voltage capacitor discharge to raise the magnet current, which is then switched to a low voltage supply, and then the current is switched back to the high voltage capacitor to zero the current. The current in each of the magnet pulses must match the order of magnitude change in proton momentum during the acceleration cycle. The magnet, power supply and operational experience are described.