J. Sandberg

Brookhaven National Laboratory, New York City, New York, United States

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Publications (88)7.01 Total impact

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    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 [1]. 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.
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    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 [1]. 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.
    Particle Accelerator Conference 2013 (PAC2013), Pasadena, CA; 01/2014
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    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 [1]. 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.
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    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.
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    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.
    01/2014; 743:56–67.
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    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; 01/2013
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    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; 01/2013
  • Y. Tan, J.-L. Mi, J. Ritter, J. Sandberg, W. Zhang
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    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; 01/2013
  • J. Mi, Y. Tan, J. Ritter, W. Zhang, J. Sandberg
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    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; 01/2013
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    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.
    01/2012;
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    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.
    01/2012;
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    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.
    01/2012;
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    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.
    09/2011
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    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.
    01/2011;
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    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.
    01/2010;
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    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.
    01/2009;
  • W. Zhang, J. Sandberg, I. Marneris
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    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.
    IEEE Transactions on Applied Superconductivity 07/2008; · 1.20 Impact Factor
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    W. Zhang, W. Ng, C. Pai, J. Sandberg, Y. Tan, Y. Tian
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    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; · 1.36 Impact Factor
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    W. Zhang, W. Eng, C. Pai, J. Sandberg, Y. Tan, Y. Tian
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    ABSTRACT: We have recently developed a simplified model and a set of simple formulas for inductive voltage adder design. This model reveals the relationship of output waveform parameters and hardware designs. A computer simulation has demonstrated that parameter estimation based on this approach is accurate as compared to an actual circuit. This approach can be used in early stages of project development to assist feasibility study, geometry selection in engineering design, and parameter selection of critical components. In this paper, we give the deduction of a simplified model. Among the estimation formulas we present are those for pulse rise time, system impedance, and number of stages. Examples are used to illustrate the advantage of this approach. This approach is also applicable to induction LINAC design.
    Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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    W. Zhang, I. Marneris, J. Sandberg
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    ABSTRACT: A main magnet chain forms a pair of transmission lines. Pulse-reflection-caused voltage and current differentiation throughout the magnet chain can have adverse effect on main magnet field quality. This effect is associated with magnet system configuration, coupling efficiency, and parasitic parameters. A better understanding of this phenomenon will help us in new design and existing system upgrade. In this paper, we exam the transmission line effect due to different input functions as well as configuration, coupling, and other parameters.
    Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007