[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.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2014; 763:610 - 673. DOI:10.1016/j.nima.2014.03.067 · 1.22 Impact Factor
[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.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2014; 743:56–67. DOI:10.1016/j.nima.2013.11.102 · 1.22 Impact Factor
[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: 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: 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 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.
Pulsed Power Conference (PPC), 2013 19th IEEE; 06/2013
[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.
Pulsed Power Conference (PPC), 2013 19th IEEE; 06/2013
[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.
Pulsed Power Conference (PPC), 2013 19th IEEE; 06/2013
[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.
Pulsed Power Conference (PPC), 2013 19th IEEE; 06/2013
[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: 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: 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: 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: 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.
[Show abstract][Hide abstract] ABSTRACT: Accelerator main dipole magnet system magnetic field regulation depends on its transmission line characteristic properties and its power supply system regulations. In addition, the main magnet AC power transformer configuration has indirect impact on the field quality of dipole magnet. A large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide uniform dipole fields when powered. When all dipole magnets are linked together in a synchrotron, they become a coupled pair of very high order complex ladder networks due to magnet parasitic capacitance, leakage resistance, and conductor resistance. In this study, we present multiphase transformer effect and harmonic response analysis of AGS main magnet system.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we propose a simplified model for easy estimation of design parameters and quick analysis of fast pulsed inductive adder modulators. Analytical method is used to deduct the simplified circuit model. This model offers an easy way to understand the behavior of the inductive-adder modulator circuits and provides designers a helpful tool to estimate critical parameters such as pulse rise time, system impedance, number of adder stages, etc. Computer simulations demonstrate that parameter estimation based on simplified circuit model is fairly accurate as compared to original circuit. Further more, this approach can be used in early stage of system development to assist the feasibility study of the project and to aid geometry selection and parameter selection of critical components.
IEEE Transactions on Dielectrics and Electrical Insulation 09/2007; 14(4-14):913 - 920. DOI:10.1109/TDEI.2007.4286525 · 1.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The two rings in the Relativistic Heavy Ion Collider (RHIC) require a total of 933 power supplies to supply current to highly inductive superconducting magnets. Failure statistics for the RHIC power supplies will be presented for the last three RHIC runs. The failures of the power supplies will be analyzed. The statistics associated with the power supply failures will be presented. Comparisons of the failure statistics for the last three RHIC runs will be shown. Improvements that have increased power supply availability will be discussed. Further improvements to increase the availability of the power supplies will also be discussed.