IPAC2012 - Classification: 07 Accelerator Technology and Main Systems / T16 Pulsed Power Technology

Paper	Title	Page
THPPC061	A 12 kV, 1 kHz, Pulse Generator for Breakdown Studies of Samples for CLIC RF Accelerating Structures	3431
	R.H. Soares, M.J. Barnes, S. Calatroni, J.W. Kovermann, W. Wuensch CERN, Geneva, Switzerland
	Compact Linear Collider (CLIC) RF structures must be capable of sustaining high surface electric fields, in excess of 200 MV/m, with a breakdown (BD) rate below 3×10^-7 breakdowns/pulse/m. Achieving such a low rate requires a detailed understanding of all the steps involved in the mechanism of breakdown. One of the fundamental studies is to investigate the statistical characteristics of the BD rate phenomenon at very low values to understand the origin of an observed dependency of the surface electric field raised to the power of 30. To acquire sufficient BD data, in a reasonable period of time, a high repetition rate pulse generator is required for an existing d.c. spark system at CERN. Following BD of the material sample the pulse generator must deliver a current pulse of several 10’s of Amperes for ~2 μs. A high repetition rate pulse generator has been designed, built and tested; this utilizes pulse forming line technology and employs MOSFET switches. This paper describes the design of the pulse generator and presents measurement results.

THPPD059	Conductive EMI Reduction to Kicker Magnet Power Supply in NSRRC	3647
	Y.-H. Liu, J.-C. Chang, C.S. Chen, H.H. Chen, J.-R. Chen NSRRC, Hsinchu, Taiwan
	The purpose of this paper is to estimate and reduce the conductive Electromagnetic Interference (EMI) from kicker magnet power supply in TLS. A LISN system was conducted to measure the EMI spectrum of kicker power supply. The EMI noise exceeded FCC standards in some frequency range especially during kicker firing. Reducing EMI level by using different EMI filters were applied. Double pi filter was more efficient than single pi filter. After using filter, the conducted EMI could diminish lower than FCC class B. The experimental results will provide useful information to future TPS pulsed magnet design.

THPPD067	Performance of Kicker Pulsers for TPS Project	3665
	C.-S. Fann, C.-T. Chen, K.T. Hsu, S.Y. Hsu, J.C. Huang, K.-K. Lin, K.-B. Liu, H.M. Shih, K.L. Tsai NSRRC, Hsinchu, Taiwan
	A set of kicker power suppliers has been designed and fabricated for storage ring beam injection of the Taiwan Photon Source (TPS) project. In order to fulfill the requirements, the performance of the designed units has been bench tested and the results are examined. The matching in four pulsers, the pulse-to-pulse stability and the time jitter are specified according to the beam injection requirements. The engineering evaluation and the measurement results are briefly discussed.

THPPD069	Adjustable Pulse Duration Fast Kicker for the CRYRING Storage Ring	3671
	J.-P. Lavieville, P. Lebasque SOLEIL, Gif-sur-Yvette, France W. Beeckman, O. Cosson Sigmaphi, Vannes, France
	The CRYRING storage ring of the Manne Siegbahn Laboratory (MSL, Stockholm) shall be moved to become part of FLAIR accelerators complex in Darmstadt to be used for deceleration of antiprotons and charged ions. That needs an upgrade to adapt it to the full energy range (30MeV – 0.13 MeV) of its future exploitation. SIGMAPHI, in close collaboration with SOLEIL light Source, is in charge of new fast injection and extraction magnets kickers and their pulsed power supplies. The injection will be done at maximum energy (30 MeV) while the extraction need to cover the full energy range (30 MeV – 0.13 MeV) that requires a continuous adjustment capability on the pulse duration and on the deviation amplitude. The development made specifically for the CRYRING kickers is based on a new design involving two different pulsed power supplies, each one managing either the fast rise time or the current flat top. Using solid state switches allows adapting simultaneously the pulse duration and its amplitude. This contribution presents the specific scheme and the development of a kicker system working up to 20 kV with pulse duration from 1.62 μs to 16.3 μs with transient times less than 300 ns.

THPPD070	Design of High Power Pulse Modulator for Driving of Twystron used in S-band Linear Accelerator	3674
	V. Aslani, F. AbbasiDavani, F. Ghasemi, M.Sh. Shafiee sbu, Tehran, Iran
	This design related to an s-band linear accelerator that the main tube and buncher of it have been made. RF power supply is used in this accelerator tube made up of a Twystron with 2.5 MW peak power and frequency band width 2.9~3.1 GHz. This paper offers the design of modulator for this RF amplifier. This modulator design uses solid-state method and is under construction with specification of ; Adjustable voltage from 0 to 120 kV, adjustable pulse width 2 until7μsecond, adjustable repetition rate 80-120 Hz ,ripple less than0.25% and efficiency up 80 percent. This system designed with series of 6 modules that each of them provides 5kV and IGBT switches that transform the voltage on the pulse transformer.

THPPD071	A Compact Switching Power Supply utilizing SiC-JFET for the Digital Accelerator	3677
	K. Okamura, T. Iwashita, K. Takayama, M. Wake KEK, Ibaraki, Japan K. Takaki, M. Toshiya Iwate university, Morioka, Iwate, Japan
	New induction synchrotron system using an induction cell has been developed and constructed at KEK. We refer to the accelerator using the induction acceleration system combined with digitally controlled PWM power supply as Digital Accelerator. In that system, the switching power supply is one of the key devices which realize digital acceleration. The requirements of the switching power supply are high voltage (2 kV) and high repetition frequency (1 MHz). In the present system, we used series connected MOSFETs as the switching device. However, series connection gives large complexity and less reliability. Among the various switching devices, a SiC-JFET is the promising candidates because it has ultrafast switching speed and voltage blocking capability. Therefore, we have developed a new device to substitute existing silicon MOSFET and succeeded to operate with 1 MHz – 1 kV – 27 A condition*. Then we designed and constructed a ultra compact full bridge switching power supply utilizing those devices as a next step. Design and test results will be presented in the conference. T. Iwashita et al., KEK Digital Accelerator, Phys. Rev. ST-AB 14, 071302 (2011) K. Takayama et al., in Proc. of IPAC’11, pp 1920-1922 * K. Okamura et al., in Proc. of IPAC’11, pp 3400-3402

THPPD072	Performance Optimization of the Stacked-Blumlein	3680
	L.W. Zhang, J. Li, W.D. Wang CAEP/IFP, Mainyang, Sichuan, People's Republic of China Y. Li CAEP, Mainyang, Sichuan, People's Republic of China
	Funding: This work was supported by the National Natural Science Foundation of China (11035004) For the applications of the Dielectric Wall Accelerator (DWA), the stacked Blumlein pulse generator comprised of parallel-plate transmission lines is being developed. The peak output voltage of the stacked Blumlein will be much lower than expected due to the parasitic coupling among the individual pulse forming lines of the Blumlein stack. The finite difference time domain method is used to model the stacked Blumlein structure and determine the outputs. We present the optimization of a 20-Blumleins-stack in this paper. The results for different structures are discussed.

THPPD073	Development and Management of the Modulator System for PLS-II 3.0 GeV Electron Linac	3683
	S.H. Kim, J.Y. Huang, S.J. Kwon, B.-J. Lee, Y.J. Moon, S.H. Nam, S.S. Park, S. Shin PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: This work is supported by MEST(Ministry of Education, Science and Technology) and POSCO(Pohang Steel and Iron Company). The Pohang Accelerator Laboratory (PAL) had started the upgrade project (called PLS-II) of the Pohang Light Source (PLS) from 2009 for increasing its energy from 2.5 GeV to 3 GeV and changing the operation mode from fill-up to top-up mode. Top-up mode operation requires high energy stability of the linac beam and machine reliability in the linac modulator systems. For providing the additional 0.5 GeV energy from the 2.5 GeV PLS linac, we added four units of the modulator system. We have two different types of the pulse modulator system for using existing pulse modulators, thyristor control type, in the upgrade project (PLS-II). The two types are thyristor control type and inverter power type. In the thyristor control type, a de-Qing system controls the modulator pulse forming network (PFN) charging voltage stability, and in the inverter power supply type, CCPS provides highly stable charging voltage to the modulator. We will present development and management of the pulse modulator system for obtaining machine reliability and stability from 3.0 GeV linac.

THPPD074	Effect of a Metallized Chamber upon the Field Response of a Kicker Magnet: Simulation Results and Analytical Calculations	3686
	M.J. Barnes, M.G. Atanasov, T. Fowler, T. Kramer, T. Stadlbauer CERN, Geneva, Switzerland
	Metallized racetrack vacuum chambers will be used in the pulsed magnets of the Austrian cancer therapy and research facility, MedAustron. It is important that the metallization does not unduly degrade field rise and fall times or the flattop of the field pulse in the pulsed magnets. This was of particular concern for a tune kicker magnet, which has a specified rise and fall time of 100 ns. The impact of the metallization, upon the transient field response, has been determined by finite element method (FEM) simulations: the dependency of the field response to the metallization thickness and resistivity are presented. Formulae for the field response, which permit the use of a ramped transient excitation current, are presented: thus the coating thickness and resistivity can be determined which result in a maximum permissible field attenuation and delay for a given current rise time. In addition, results of simulations of the effect of a magnetic brazing collar, located between the ceramic vacuum chamber and flange, are reported.

THPPD075	Design and Measurements of a Fast High-voltage Pulse Generator for the MedAustron Low Energy Transfer Line Fast Deflector	3689
	T. Fowler, M.J. Barnes, T. Kramer, F. Müller, T. Stadlbauer CERN, Geneva, Switzerland
	MedAustron, a centre for ion-therapy and research, will comprise an accelerator facility based on a synchrotron for the delivery of protons and light ions for cancer treatment. The Low Energy Beam Transfer line (LEBT) to the synchrotron contains an electrostatic fast deflector (EFE) which, when energized, deviates the continuous beam arriving from the ion source onto a Faraday Cup: the specified voltage is ±3.5 kV. De-energizing the EFE for variable pulse durations from 500 ns up to d.c. allows beam passage for multi-turn injection into the synchrotron. To maintain beam quality in the synchrotron, the EFE pulse generator requires rise and fall times of less than 300 ns between 90 % of peak voltage and a ±1 V level. To achieve this, a pulsed power supply (PKF), with high voltage MOSFET switches connected in a push-pull configuration, will be mounted in close proximity to the deflector itself. A fast, large dynamic range monitoring circuit will verify switching to the ±1 V level and subsequent flat bottom pulse quality. A prototype will be installed in the injector test stand in 2012; this paper presents the design and first measurements of the PKF and its monitoring circuit.

THPPD076	Evaluation of Components for the High Precision Inductive Adder for the CLIC Damping Rings	3692
	J. Holma, M.J. Barnes CERN, Geneva, Switzerland
	The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the extraction kickers of the CLIC damping rings are particularly demanding: the flattop of the output pulse must be 160 ns duration, 12.5 kV and 250 A, with a combined ripple and droop of not more than ±0.02 %. An inductive adder allows the use of different modulation techniques and is therefore a very promising approach to meeting the specifications. In addition to semiconductors working in their saturated region, semiconductors working in their linear region are needed for applying analogue modulation techniques. Simulations have been carried out to define component specifications for the inductive adder: this paper reports the results of tests and measurements of various components.

THPPD077	ISIS Injector 2 MW Pulsed RF System Power Supply Upgrade	3695
	R.J. Anderson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom M. Keelan STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
	The ISIS pulsed neutron and muon source uses a 4-stage 70 Mev linear accelerator powered by TH116 triode valves. The TH116 anode supply capacitor banks have until recently been supplied by conventional 6-pulse silicon controlled rectifier (SCR) bridges delivering up to 40 kV at 5 A direct current. This dated system has become increasingly difficult to maintain. Early trials of an upgraded system using modern, compact, capacitor charging, switch mode supplies (SMPSs) resulted in severe supply power quality issues due to the pulsed nature of the current demanded from the capacitor banks. Measurements and Spice simulations of the old and replacement supplies allowed the power quality issues to be investigated and an additional external-to-the-SMPS regulator control loop to be developed. The new SMPSs operating with the additional control loop have been tested successfully on several of the linear accelerator stages and are now in continuous operational use. The process of replacing all the original SCR 6-pulse bridges is now well advanced and the operational benefits for ISIS are becoming evident.

THPPD078	Cold Cathode Thyratron Based High-voltage Kicker Generators at the Duke Accelerators: Six Year Experience	3698
	V. Popov, S.F. Mikhailov, P.W. Wallace, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant #DE-FG02-97ER41033. The performance of the Duke storage ring based light sources, the Duke storage ring FEL and High Intensity Gamma-ray Source (HIGS), has been greatly improved since 2007 as the result of operating a new full-energy, top-off booster injector (0.18 - 1.2 GeV), allowing fixed energy operation of the storage ring (0.25 - 1.2 GeV). The injection/extraction kicker system is one of the key components of the accelerator facility which determines efficiency and reliability of the light source operation. Pseudo-Spark Switches(PSS), also known as cold cathode thyratrons, are the critical components of the high voltage pulse generators for kickers. More than six years of operation has allowed us to study the lifetime issue for the 10 kA class devices. Recently, we have tested the next generation cold cathode thyratron, with one installed in one of our storage ring kicker high voltage generators. In the present paper we will also present preliminary test results of this new thyratron and the required modifications of its triggering driver to improve its performance.

THPPD079	Compact, High Current, High Voltage Solid State Switches for Accelerator Applications	3701
	H.D. Sanders, S.C. Glidden APP, Freeville, USA
	Most switches used for high current, high voltage accelerator applications are vacuum or gas switches, such as spark gaps and thyratrons. Recently, high voltage IGBT based switches have become common, but are limited in current and are not compact. This paper will describe a compact, high current, high voltage solid state switch. These switches have been tested to 50kV, to greater than 12kA, to greater than 50kA/μs, to 360Hz, and to 3x10⁸ pulses, without failure. They have been used in accelerators to drive klystrons and kickers, and have been used as crowbars while offering advantages over thyratron switches for cost, lifetime, size and weight. The switches are based on series connected fast thyristors with 3cm² die in a 20cm² package. This package is more compact than TO-200 Puk sized devices, and does not require compression for proper operation. Each package is rated for 4kV, 14kA and 30kA/μs. One example, a 48kV switch which includes the trigger and snubber circuits, fits in a volume of 200mm x 85mm x 65mm, and requires only a fiber-optic trigger input. Such switches have been used on SRS and EMMA at Daresbury Laboratory in the UK, and at several US national laboratories.

THPPD081	Droop Compensation for the High Voltage Converter Modulators at the Spallation Neutron Source	3704
	G. Patel, D.E. Anderson, D.J. Solley, M. Wezensky ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725 The Spallation Neutron Source (SNS) has been in operation since 2006 and has demonstrated up to 1 MW of beam power. At 1MW, the High Voltage Converter Modulators (HVCMs) are delivering 11MW pulsed power to the Klystrons for 1185us at 60 Hz. The pulsed output of the modulator has a substantial voltage droop. The future operational goals of the accelerator involve delivering 1.4 MW to the target. This implies an increase in the output pulse width of the HVCM, resulting in loss of RF control from inadequate control margin for LLRF systems due to modulator voltage reduction at the end of pulse. Initially, the HVCM was designed with a pulse width modulation scheme for droop compensation but early operations revealed this technique unreliable for full power operation. Increasing the output voltage of the modulator would likely compromise system reliability. This paper proposes the use of alternate modulation schemes to address the voltage droop. The effect of frequency modulation and phase shift modulation on output pulse is studied and concludes by selecting an optimum modulation algorithm to be implemented. Experimental results will also be presented.

THPPD082	A Novel Solid-State Marx Modulator Topology with Voltage Droop Self-Compensation	3707
	P. Chen, M. Lundquist, D. Yu DULY Research Inc., Rancho Palos Verdes, California, USA
	Funding: Work supported by U.S. Department of Energy SBIR grant no. DE-FG02-08ER85052. Solid-state Marx modulators are preferred over conventional modulators in accelerators and radar applications because of their high flexibility, high reliability and long life. However, voltage droop is a notable issue. A novel topology of solid-state Marx modulators is described in this paper for raising their electric energy utilization ratios (EEURs). The new Marx modulator incorporates a buck regulator circuit into each Marx cell and adopts a higher charge voltage than that of application. The topology allows Marx cells to store more electric energy and utilize the energy more efficiently than others. Initial theoretical analysis and preliminary experiments show that solid-state Marx modulators constructed with this topology and under proper control of the stepwise energy release are able to significantly enhance their EEURs. The cost effective Marx modulators with compact energy storage sizes will resolve the issue of voltage droop when they are used in high power, long pulse applications.

THPPD083	Analysis of Kicker Noise Induced Beam Emittance Growth	3710
	W. Zhang, L. A. Ahrens, I. Blackler, M. Blaskiewicz, J.M. Brennan, W. Fischer, H. Hahn, H. Huang, N.A. Kling, M. Lafky, G.J. Marr, K. Mernick, J.-L. Mi, M.G. Minty, C. Naylor, T. Roser, J. Sandberg, T.C. Shrey, B. Van Kuik, A. Zelenski BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Over the last few years, physicists have suspected the presence of noise acting on the RHIC beams observable as occasional emittance growth at high beam energies. While the noise was sporadic in the past, it became more persistent during the run-11 setup period. An investigation diagnosed the source as originating from the RHIC abort 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.

THPPD084	Analysis of Beam Loss Induced Abort Kicker Instability	3713
	W. Zhang, L. A. Ahrens, W. Fischer, H. Hahn, J.-L. Mi, C. Pai, J. Sandberg, Y. Tan BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. 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.

THPPD085	Research and Development of RHIC Injection Kicker Upgrade with Nano Second FID Pulse Generator	3716
	W. Zhang, W. Fischer, H. Hahn, C.J. Liaw, C. Pai, J. Sandberg, J.E. Tuozzolo BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Our recent effort to test a 50 kV, 1 kA, 50 ns pulse width, 10 ns pulse rise time FID pulse generator with 250 ft transmission cable, resistive load, and existing RHIC injection kicker magnet has produced unparalleled result. This is the very first attempt to drive a high strength fast kicker magnet with a nanosecond 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.

Paper

Title

Page

A 12 kV, 1 kHz, Pulse Generator for Breakdown Studies of Samples for CLIC RF Accelerating Structures

3431

R.H. Soares, M.J. Barnes, S. Calatroni, J.W. Kovermann, W. Wuensch
CERN, Geneva, Switzerland

Compact Linear Collider (CLIC) RF structures must be capable of sustaining high surface electric fields, in excess of 200 MV/m, with a breakdown (BD) rate below 3×10^-7 breakdowns/pulse/m. Achieving such a low rate requires a detailed understanding of all the steps involved in the mechanism of breakdown. One of the fundamental studies is to investigate the statistical characteristics of the BD rate phenomenon at very low values to understand the origin of an observed dependency of the surface electric field raised to the power of 30. To acquire sufficient BD data, in a reasonable period of time, a high repetition rate pulse generator is required for an existing d.c. spark system at CERN. Following BD of the material sample the pulse generator must deliver a current pulse of several 10’s of Amperes for ~2 μs. A high repetition rate pulse generator has been designed, built and tested; this utilizes pulse forming line technology and employs MOSFET switches. This paper describes the design of the pulse generator and presents measurement results.

THPPD059

Conductive EMI Reduction to Kicker Magnet Power Supply in NSRRC

3647

Y.-H. Liu, J.-C. Chang, C.S. Chen, H.H. Chen, J.-R. Chen
NSRRC, Hsinchu, Taiwan

The purpose of this paper is to estimate and reduce the conductive Electromagnetic Interference (EMI) from kicker magnet power supply in TLS. A LISN system was conducted to measure the EMI spectrum of kicker power supply. The EMI noise exceeded FCC standards in some frequency range especially during kicker firing. Reducing EMI level by using different EMI filters were applied. Double pi filter was more efficient than single pi filter. After using filter, the conducted EMI could diminish lower than FCC class B. The experimental results will provide useful information to future TPS pulsed magnet design.

THPPD067

Performance of Kicker Pulsers for TPS Project

3665

C.-S. Fann, C.-T. Chen, K.T. Hsu, S.Y. Hsu, J.C. Huang, K.-K. Lin, K.-B. Liu, H.M. Shih, K.L. Tsai
NSRRC, Hsinchu, Taiwan

A set of kicker power suppliers has been designed and fabricated for storage ring beam injection of the Taiwan Photon Source (TPS) project. In order to fulfill the requirements, the performance of the designed units has been bench tested and the results are examined. The matching in four pulsers, the pulse-to-pulse stability and the time jitter are specified according to the beam injection requirements. The engineering evaluation and the measurement results are briefly discussed.

THPPD069

Adjustable Pulse Duration Fast Kicker for the CRYRING Storage Ring

3671

J.-P. Lavieville, P. Lebasque
SOLEIL, Gif-sur-Yvette, France
W. Beeckman, O. Cosson
Sigmaphi, Vannes, France

The CRYRING storage ring of the Manne Siegbahn Laboratory (MSL, Stockholm) shall be moved to become part of FLAIR accelerators complex in Darmstadt to be used for deceleration of antiprotons and charged ions. That needs an upgrade to adapt it to the full energy range (30MeV – 0.13 MeV) of its future exploitation. SIGMAPHI, in close collaboration with SOLEIL light Source, is in charge of new fast injection and extraction magnets kickers and their pulsed power supplies. The injection will be done at maximum energy (30 MeV) while the extraction need to cover the full energy range (30 MeV – 0.13 MeV) that requires a continuous adjustment capability on the pulse duration and on the deviation amplitude. The development made specifically for the CRYRING kickers is based on a new design involving two different pulsed power supplies, each one managing either the fast rise time or the current flat top. Using solid state switches allows adapting simultaneously the pulse duration and its amplitude. This contribution presents the specific scheme and the development of a kicker system working up to 20 kV with pulse duration from 1.62 μs to 16.3 μs with transient times less than 300 ns.

THPPD070

Design of High Power Pulse Modulator for Driving of Twystron used in S-band Linear Accelerator

3674

V. Aslani, F. AbbasiDavani, F. Ghasemi, M.Sh. Shafiee
sbu, Tehran, Iran

This design related to an s-band linear accelerator that the main tube and buncher of it have been made. RF power supply is used in this accelerator tube made up of a Twystron with 2.5 MW peak power and frequency band width 2.9~3.1 GHz. This paper offers the design of modulator for this RF amplifier. This modulator design uses solid-state method and is under construction with specification of ; Adjustable voltage from 0 to 120 kV, adjustable pulse width 2 until7μsecond, adjustable repetition rate 80-120 Hz ,ripple less than0.25% and efficiency up 80 percent. This system designed with series of 6 modules that each of them provides 5kV and IGBT switches that transform the voltage on the pulse transformer.

THPPD071

A Compact Switching Power Supply utilizing SiC-JFET for the Digital Accelerator

3677

K. Okamura, T. Iwashita, K. Takayama, M. Wake
KEK, Ibaraki, Japan
K. Takaki, M. Toshiya
Iwate university, Morioka, Iwate, Japan

New induction synchrotron system using an induction cell has been developed and constructed at KEK*. We refer to the accelerator using the induction acceleration system combined with digitally controlled PWM power supply as Digital Accelerator**. In that system, the switching power supply is one of the key devices which realize digital acceleration. The requirements of the switching power supply are high voltage (2 kV) and high repetition frequency (1 MHz). In the present system, we used series connected MOSFETs as the switching device. However, series connection gives large complexity and less reliability. Among the various switching devices, a SiC-JFET is the promising candidates because it has ultrafast switching speed and voltage blocking capability. Therefore, we have developed a new device to substitute existing silicon MOSFET and succeeded to operate with 1 MHz – 1 kV – 27 A condition***. Then we designed and constructed a ultra compact full bridge switching power supply utilizing those devices as a next step. Design and test results will be presented in the conference.
* T. Iwashita et al., KEK Digital Accelerator, Phys. Rev. ST-AB 14, 071302 (2011)
** K. Takayama et al., in Proc. of IPAC’11, pp 1920-1922
*** K. Okamura et al., in Proc. of IPAC’11, pp 3400-3402

THPPD072

Performance Optimization of the Stacked-Blumlein

3680

L.W. Zhang, J. Li, W.D. Wang
CAEP/IFP, Mainyang, Sichuan, People's Republic of China
Y. Li
CAEP, Mainyang, Sichuan, People's Republic of China

Funding: This work was supported by the National Natural Science Foundation of China (11035004)
For the applications of the Dielectric Wall Accelerator (DWA), the stacked Blumlein pulse generator comprised of parallel-plate transmission lines is being developed. The peak output voltage of the stacked Blumlein will be much lower than expected due to the parasitic coupling among the individual pulse forming lines of the Blumlein stack. The finite difference time domain method is used to model the stacked Blumlein structure and determine the outputs. We present the optimization of a 20-Blumleins-stack in this paper. The results for different structures are discussed.

THPPD073

Development and Management of the Modulator System for PLS-II 3.0 GeV Electron Linac

3683

S.H. Kim, J.Y. Huang, S.J. Kwon, B.-J. Lee, Y.J. Moon, S.H. Nam, S.S. Park, S. Shin
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: This work is supported by MEST(Ministry of Education, Science and Technology) and POSCO(Pohang Steel and Iron Company).
The Pohang Accelerator Laboratory (PAL) had started the upgrade project (called PLS-II) of the Pohang Light Source (PLS) from 2009 for increasing its energy from 2.5 GeV to 3 GeV and changing the operation mode from fill-up to top-up mode. Top-up mode operation requires high energy stability of the linac beam and machine reliability in the linac modulator systems. For providing the additional 0.5 GeV energy from the 2.5 GeV PLS linac, we added four units of the modulator system. We have two different types of the pulse modulator system for using existing pulse modulators, thyristor control type, in the upgrade project (PLS-II). The two types are thyristor control type and inverter power type. In the thyristor control type, a de-Qing system controls the modulator pulse forming network (PFN) charging voltage stability, and in the inverter power supply type, CCPS provides highly stable charging voltage to the modulator. We will present development and management of the pulse modulator system for obtaining machine reliability and stability from 3.0 GeV linac.

THPPD074

Effect of a Metallized Chamber upon the Field Response of a Kicker Magnet: Simulation Results and Analytical Calculations

3686

M.J. Barnes, M.G. Atanasov, T. Fowler, T. Kramer, T. Stadlbauer
CERN, Geneva, Switzerland

Metallized racetrack vacuum chambers will be used in the pulsed magnets of the Austrian cancer therapy and research facility, MedAustron. It is important that the metallization does not unduly degrade field rise and fall times or the flattop of the field pulse in the pulsed magnets. This was of particular concern for a tune kicker magnet, which has a specified rise and fall time of 100 ns. The impact of the metallization, upon the transient field response, has been determined by finite element method (FEM) simulations: the dependency of the field response to the metallization thickness and resistivity are presented. Formulae for the field response, which permit the use of a ramped transient excitation current, are presented: thus the coating thickness and resistivity can be determined which result in a maximum permissible field attenuation and delay for a given current rise time. In addition, results of simulations of the effect of a magnetic brazing collar, located between the ceramic vacuum chamber and flange, are reported.

THPPD075

Design and Measurements of a Fast High-voltage Pulse Generator for the MedAustron Low Energy Transfer Line Fast Deflector

3689

T. Fowler, M.J. Barnes, T. Kramer, F. Müller, T. Stadlbauer
CERN, Geneva, Switzerland

MedAustron, a centre for ion-therapy and research, will comprise an accelerator facility based on a synchrotron for the delivery of protons and light ions for cancer treatment. The Low Energy Beam Transfer line (LEBT) to the synchrotron contains an electrostatic fast deflector (EFE) which, when energized, deviates the continuous beam arriving from the ion source onto a Faraday Cup: the specified voltage is ±3.5 kV. De-energizing the EFE for variable pulse durations from 500 ns up to d.c. allows beam passage for multi-turn injection into the synchrotron. To maintain beam quality in the synchrotron, the EFE pulse generator requires rise and fall times of less than 300 ns between 90 % of peak voltage and a ±1 V level. To achieve this, a pulsed power supply (PKF), with high voltage MOSFET switches connected in a push-pull configuration, will be mounted in close proximity to the deflector itself. A fast, large dynamic range monitoring circuit will verify switching to the ±1 V level and subsequent flat bottom pulse quality. A prototype will be installed in the injector test stand in 2012; this paper presents the design and first measurements of the PKF and its monitoring circuit.

THPPD076

Evaluation of Components for the High Precision Inductive Adder for the CLIC Damping Rings

3692

J. Holma, M.J. Barnes
CERN, Geneva, Switzerland

The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat, high-voltage pulses. The specifications for the extraction kickers of the CLIC damping rings are particularly demanding: the flattop of the output pulse must be 160 ns duration, 12.5 kV and 250 A, with a combined ripple and droop of not more than ±0.02 %. An inductive adder allows the use of different modulation techniques and is therefore a very promising approach to meeting the specifications. In addition to semiconductors working in their saturated region, semiconductors working in their linear region are needed for applying analogue modulation techniques. Simulations have been carried out to define component specifications for the inductive adder: this paper reports the results of tests and measurements of various components.

THPPD077

ISIS Injector 2 MW Pulsed RF System Power Supply Upgrade

3695

R.J. Anderson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
M. Keelan
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

The ISIS pulsed neutron and muon source uses a 4-stage 70 Mev linear accelerator powered by TH116 triode valves. The TH116 anode supply capacitor banks have until recently been supplied by conventional 6-pulse silicon controlled rectifier (SCR) bridges delivering up to 40 kV at 5 A direct current. This dated system has become increasingly difficult to maintain. Early trials of an upgraded system using modern, compact, capacitor charging, switch mode supplies (SMPSs) resulted in severe supply power quality issues due to the pulsed nature of the current demanded from the capacitor banks. Measurements and Spice simulations of the old and replacement supplies allowed the power quality issues to be investigated and an additional external-to-the-SMPS regulator control loop to be developed. The new SMPSs operating with the additional control loop have been tested successfully on several of the linear accelerator stages and are now in continuous operational use. The process of replacing all the original SCR 6-pulse bridges is now well advanced and the operational benefits for ISIS are becoming evident.

THPPD078

Cold Cathode Thyratron Based High-voltage Kicker Generators at the Duke Accelerators: Six Year Experience

3698

V. Popov, S.F. Mikhailov, P.W. Wallace, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant #DE-FG02-97ER41033.
The performance of the Duke storage ring based light sources, the Duke storage ring FEL and High Intensity Gamma-ray Source (HIGS), has been greatly improved since 2007 as the result of operating a new full-energy, top-off booster injector (0.18 - 1.2 GeV), allowing fixed energy operation of the storage ring (0.25 - 1.2 GeV). The injection/extraction kicker system is one of the key components of the accelerator facility which determines efficiency and reliability of the light source operation. Pseudo-Spark Switches(PSS), also known as cold cathode thyratrons, are the critical components of the high voltage pulse generators for kickers. More than six years of operation has allowed us to study the lifetime issue for the 10 kA class devices. Recently, we have tested the next generation cold cathode thyratron, with one installed in one of our storage ring kicker high voltage generators. In the present paper we will also present preliminary test results of this new thyratron and the required modifications of its triggering driver to improve its performance.

THPPD079

Compact, High Current, High Voltage Solid State Switches for Accelerator Applications

3701

H.D. Sanders, S.C. Glidden
APP, Freeville, USA

Most switches used for high current, high voltage accelerator applications are vacuum or gas switches, such as spark gaps and thyratrons. Recently, high voltage IGBT based switches have become common, but are limited in current and are not compact. This paper will describe a compact, high current, high voltage solid state switch. These switches have been tested to 50kV, to greater than 12kA, to greater than 50kA/μs, to 360Hz, and to 3x10⁸ pulses, without failure. They have been used in accelerators to drive klystrons and kickers, and have been used as crowbars while offering advantages over thyratron switches for cost, lifetime, size and weight. The switches are based on series connected fast thyristors with 3cm² die in a 20cm² package. This package is more compact than TO-200 Puk sized devices, and does not require compression for proper operation. Each package is rated for 4kV, 14kA and 30kA/μs. One example, a 48kV switch which includes the trigger and snubber circuits, fits in a volume of 200mm x 85mm x 65mm, and requires only a fiber-optic trigger input. Such switches have been used on SRS and EMMA at Daresbury Laboratory in the UK, and at several US national laboratories.

THPPD081

Droop Compensation for the High Voltage Converter Modulators at the Spallation Neutron Source

3704

G. Patel, D.E. Anderson, D.J. Solley, M. Wezensky
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725
The Spallation Neutron Source (SNS) has been in operation since 2006 and has demonstrated up to 1 MW of beam power. At 1MW, the High Voltage Converter Modulators (HVCMs) are delivering 11MW pulsed power to the Klystrons for 1185us at 60 Hz. The pulsed output of the modulator has a substantial voltage droop. The future operational goals of the accelerator involve delivering 1.4 MW to the target. This implies an increase in the output pulse width of the HVCM, resulting in loss of RF control from inadequate control margin for LLRF systems due to modulator voltage reduction at the end of pulse. Initially, the HVCM was designed with a pulse width modulation scheme for droop compensation but early operations revealed this technique unreliable for full power operation. Increasing the output voltage of the modulator would likely compromise system reliability. This paper proposes the use of alternate modulation schemes to address the voltage droop. The effect of frequency modulation and phase shift modulation on output pulse is studied and concludes by selecting an optimum modulation algorithm to be implemented. Experimental results will also be presented.

THPPD082

A Novel Solid-State Marx Modulator Topology with Voltage Droop Self-Compensation

3707

P. Chen, M. Lundquist, D. Yu
DULY Research Inc., Rancho Palos Verdes, California, USA

Funding: Work supported by U.S. Department of Energy SBIR grant no. DE-FG02-08ER85052.
Solid-state Marx modulators are preferred over conventional modulators in accelerators and radar applications because of their high flexibility, high reliability and long life. However, voltage droop is a notable issue. A novel topology of solid-state Marx modulators is described in this paper for raising their electric energy utilization ratios (EEURs). The new Marx modulator incorporates a buck regulator circuit into each Marx cell and adopts a higher charge voltage than that of application. The topology allows Marx cells to store more electric energy and utilize the energy more efficiently than others. Initial theoretical analysis and preliminary experiments show that solid-state Marx modulators constructed with this topology and under proper control of the stepwise energy release are able to significantly enhance their EEURs. The cost effective Marx modulators with compact energy storage sizes will resolve the issue of voltage droop when they are used in high power, long pulse applications.

THPPD083

Analysis of Kicker Noise Induced Beam Emittance Growth

3710

W. Zhang, L. A. Ahrens, I. Blackler, M. Blaskiewicz, J.M. Brennan, W. Fischer, H. Hahn, H. Huang, N.A. Kling, M. Lafky, G.J. Marr, K. Mernick, J.-L. Mi, M.G. Minty, C. Naylor, T. Roser, J. Sandberg, T.C. Shrey, B. Van Kuik, A. Zelenski
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Over the last few years, physicists have suspected the presence of noise acting on the RHIC beams observable as occasional emittance growth at high beam energies. While the noise was sporadic in the past, it became more persistent during the run-11 setup period. An investigation diagnosed the source as originating from the RHIC abort 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.

THPPD084

Analysis of Beam Loss Induced Abort Kicker Instability

3713

W. Zhang, L. A. Ahrens, W. Fischer, H. Hahn, J.-L. Mi, C. Pai, J. Sandberg, Y. Tan
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
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.

THPPD085

Research and Development of RHIC Injection Kicker Upgrade with Nano Second FID Pulse Generator

3716

W. Zhang, W. Fischer, H. Hahn, C.J. Liaw, C. Pai, J. Sandberg, J.E. Tuozzolo
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Our recent effort to test a 50 kV, 1 kA, 50 ns pulse width, 10 ns pulse rise time FID pulse generator with 250 ft transmission cable, resistive load, and existing RHIC injection kicker magnet has produced unparalleled result. This is the very first attempt to drive a high strength fast kicker magnet with a nanosecond 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.