IPAC2011 - List of Keywords (high-voltage)

Paper	Title	Other Keywords	Page
MOPC046	CaCo: A Cavity Combiner for IOTs Amplifiers	cavity, simulation, storage-ring, HOM	181
	B. Bravo, F. Mares, F. Pérez, P. Sanchez CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain M.L. Langlois ESRF, Grenoble, France
	The ALBA storage ring uses six room temperature cavities; each one fed by two 80 kW IOTs amplifiers at 499.654 MHz. The power of the pair of transmitters is combined by a cavity combiner, CaCo. One of the design requirements of CaCo was that it continued working safely and with a good efficiency in the case of an IOT failure (asymmetrical mode). During the first asymmetric full power tests, in May 2010, with an active IOT and the other passive, the result was dramatic, the passive IOT broke in two parts after few hours of operation. This paper presents the experimental results and the electromagnetic field simulations of the asymmetrical operation mode of CaCo, i.e. one active IOT and the other passive, and analyze why the ceramic of the output tube of the passive IOT broke during the first performance of this mode. Also, it reports a possible solution to solve this problem.

MOPC090	Tuner Performance in the S1-global Cryomodule	cavity, controls, cryomodule, coupling	286
	R. Paparella, A. Bosotti, C. Pagani INFN/LASA, Segrate (MI), Italy C. Albrecht, K. Jensch, L. Lilje DESY, Hamburg, Germany S. Barbanotti, Y.M. Pischalnikov, W. Schappert Fermilab, Batavia, USA H. Hayano, E. Kako, S. Noguchi, N. Ohuchi, Y. Yamamoto KEK, Ibaraki, Japan
	S1-Global is a collaborative effort of INFN, DESY, FNAL, SLAC and KEK, in the framework of the ILC global collaboration. For this project two cryomodules, 6 meter long and hosting four SC cavities each, were realized and successfully cold tested at KEK-STF. Three different cavity tuning systems, provided with fast tuning capability through piezoelectric actuators (piezo), were installed, and fully characterized in static and dynamic operation: Blade Tuner from INFN/FNAL, Saclay Tuner from DESY, Slide Jack Tuner from KEK. Finally, Lorenz Force Detuning (LFD) active compensation has been successfully achieved during high power cavity tests in pulsed RF regime, where active control of the LFD disturbance up to Hz-level residual detuning has been achieved with each type of tuning system up to the maximum gradient of each cavity. The installation procedures, together with the relevant results and their analyses are summarized in the paper.

MOPC142	25 Year Performance Review of the SLAC 5045 S-Band Klystron	klystron, cathode, linac, linear-collider	409
	A. Jensen, A.S. Beebe, M.V. Fazio, A.A. Haase, E.N. Jongewaard, C. Pearson, D.W. Sprehn, A.E. Vlieks, L.E. Whicker SLAC, Menlo Park, California, USA
	Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515. The SLAC 5045 S-band klystron has proven to be a remarkably reliable high peak power tube. Originally developed in the 1980’s as an upgraded RF power source for the Stanford Linear Collider, it has continually powered the SLAC linac in support of numerous programs in particle physics and photon science. The large number of tubes built and operated (more than 800) coupled with accumulated running statistics over the last 25+ years represents an unprecedented wealth of operational experience for high pulse power klystrons in accelerator applications. Mean time between failures has continued to rise during this period and is frequently in excess of 100,000 hours during the last several years. Lifetime statistics as well as some important failure modes are presented and examined here.

MOPS029	Experiments with a Fast Chopper System for Intense Ion Beams	ion, electron, space-charge, simulation	664
	H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner IAP, Frankfurt am Main, Germany
	Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

TUPC096	Solid-state Marx Generator Driven Einzel Lens Chopper	ion, ECRIS, acceleration, extraction	1233
	K. Takayama, T. Arai KEK, Ibaraki, Japan T. Adachi, K.W. Leo Sokendai, Ibaraki, Japan A. Tokuchi Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan
	A new type of pulse chopper called an Einzel lens chopper* is described. The Einzel lens, placed immediately after an electron cyclotron resonance ion source, is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time. The barrier pulse is switched on only when a beam pulse is required. When the barrier pulse is off, the DC voltage across the Einzel lens reflects ions back upstream with almost zero velocity. The device has been actually used as a chopper for the KEK Digital Accelerator, which is a small-scale induction synchrotron employing no a large injector and capable of providing a wide variety of ions, has been constructed at KEK*. A He ion beam of 50 micro-ampere was chopped in 5 micro-sec with rise/fall time of 40 nsec. T.Adachi et al., “A Solid-State Marx Generator Driven Einzel Lens Chopper”, submitted to Appl. Phys. Lett. ** T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011.

TUPC178	Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun	laser, cathode, vacuum, gun	1443
	R.R. Mammei, M. Poelker, R. Suleiman JLAB, Newport News, Virginia, USA J.L. McCarter UVa, Charlottesville, Virginia, USA T. Rao, J. Smedley 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. DOE Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10^-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.

TUPS004	Enhanced High-voltage Holding under Vacuum by Field Induced Adsorption of Gas on Metal Surfaces	vacuum, electron, cathode, plasma	1524
	A. Simonin, L. Christin, L. Doceul, F. Faisse, F. Villecroze, H. de Esch CEA, St Paul Lez Durance, France
	*The energy of future neutral beam injector heating systems of fusion power plants ranges from 1 to 2 MeV. The beam line and the reactor chamber are under vacuum, while all the electrical components (power supplies) are connected to the injector via a long pressured (SF6) high-voltage (1-2 MV) transmission line. The bushing is a key component that ensures the barrier between the transmission line and the injector under vacuum; the design of this component is very challenging as it faces several stringent constraints due to the nuclear environment, in which high-voltage holding, mechanical stresses, and radiations are combined. Moreover, it is a high-voltage feed-through that allows supply of the accelerator electrodes with electrical power, active water cooling, and gas. In this paper, a new high-voltage bushing concept based on experimental findings previously obtained in the laboratory is presented. The main advantages of the concept is a reduction of the electron field emission under vacuum, which is an issue for conventional bushings, a reduction in size, and mechanical simplification of the device resulting in cost reduction and greater reliability."

TUPS079	Construction of a Novel Compact High Voltage Electrostatic Accelerator	vacuum, target, ion, ion-source	1722
	P. Beasley, O. Heid Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany
	A compact demonstrator system based on a Cockcroft-Walton (or Greinacher) cascade has been successfully built and tested. The concept has been developed using modern materials and a different design philosophy, which in turn can then enable this novel configuration to operate at much higher voltage gradients. This paper explores the progress made over the past 18 months and future plans to utilise the technology to develop one such concept for an energy efficient 10MV, 100μA, tandem proton accelerator, with a <2m2 footprint. The development of such a compact high voltage particle accelerator, with high current capability has the potential to access a wide range of commercial opportunities outside the laboratory.

TUPS082	The LEBT Chopper for the Spiral 2 Project	controls, ion, vacuum, target	1731
	A.C. Caruso, F. Consoli, G. Gallo, D. Rifuggiato, E. Zappalà INFN/LNS, Catania, Italy M. Di Giacomo GANIL, Caen, France A. Longhitano ALTEK, San Gregorio (CATANIA), Italy
	The Spiral 2 driver uses a slow chopper situated in the common section of the low energy beam transport line to change the beam intensity, to cut off the beam in case of critical loss and to avoid hitting the wheel structure of rotating targets. The device has to work up to 10 kV, 1 kHz repetition frequency rate and its design is based on standard power circuits, custom alarm board and vacuum feed-through. The paper summarizes the design principles and describes the test results of the final device which has been installed on the beam line test bench.

TUPS093	Automatic Measurement System for Electrical Verification of the LHC Superconducting Circuits	pick-up, instrumentation, superconducting-magnet, dipole	1756
	A. Kotarba, M. Bednarek, P. Jurkiewicz, J. Ludwin, M. Talach IFJ-PAN, Kraków, Poland R. Mompo CERN, Geneva, Switzerland
	In the LHC machine, superconducting magnet circuits are used on a very large scale. The circuits, more than 1600, are all equipped with a complex set of instrumentation required for safe operation and diagnostics. The length of many circuits exceed 3 km. Due to risks of accidental damages during transport and assembly or misconnection of the circuits’ auxiliary components, it is necessary to perform an Electrical Quality Assurance (ELQA) campaign after every major intervention on a circuit and also after each thermal cycle of the machine. In order to be able to perform reliable tests on a circuit within a short time frame, a highly extensible automated mobile test system was designed and built. Four of these instruments were successfully used during the Hardware Commissioning phases of the LHC. This paper describes the hardware solutions used in the test system.

TUPS097	In-situ Experiments of Vacuum Discharge using Scanning Electron Microscopes	electron, vacuum, ion, site	1765
	T. Muranaka, V.G. Ziemann Uppsala University, Uppsala, Sweden T. Blom, K. Leifer Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
	Funding: This work is supported by the 7th European Framework Program EuCARD under grant number 227579 Fundamental understandings of vacuum discharge mechanisms and involving surface damage is an indispensable for CLIC feasibility study. We have been conducting dc experiments inside a Scanning Electron Microscope (SEM) at Uppsala university in order to investigate localised breakdown phenomena. By using a SEM, we achieve the resolution of the electron probe in the few-nm range, which is of great advantage as the surface roughness of the polished accelerating structures is in the same scale. The high accelerating field of 1 GV/m is realised by biasing an electrode with 1 kV set above the sample with a gap of sub μm. Furthermore, a second SEM equipped with a Focused Ion Beam (FIB) is used to modify the topography of sample surfaces thus the geometrical dependence of field emissions and vacuum discharges could be studied. The FIB can be used for the surface damage analysis as well. We have demonstrated subsurface damage observations by using FIB to sputter a rectangular recess into the sample in the breakdown region. Those powerful surface analysis techniques can be productively applied to the study of fatigue in prototype accelerating structures.

WEPZ004	Solid Pulse Transforming Line for DWA	impedance, coupling, simulation, induction	2769
	L. Zhang CAEP/IFP, Mainyang, Sichuan, People's Republic of China
	This paper introduces the research work about solid pulse transforming line for dielectric wall accelerator(DWA). We will discuss the impedence of the solid pulse transforming line due to different material. Some research of PCSS(photoconductive semiconductor switch),which was used for DWA, will also be described.

THOBB01	Evaluation of Performance, Reliability, and Risk for High Peak Power RF Sources from S-band through X-band for Advanced Accelerator Applications	klystron, linac, focusing, electron	2882
	M.V. Fazio, C. Adolphsen, A. Jensen, C. Pearson, D.W. Sprehn, A.E. Vlieks, F. Wang SLAC, Menlo Park, California, USA M.V. Fazio LANL, Los Alamos, New Mexico, USA
	Historically linear accelerator development and the choice of frequency have been driven by the availability of RF power sources. This is also true at the present time and is particularly significant as new accelerators are being conceived and planned over a wide frequency range for FEL light sources and other applications. This paper evaluates the current state of the technology for high peak power RF sources from S-band through X-band including reliability and the facility risk incurred for applications demanding high availability and decades-long operation.
	Slides THOBB01 [2.326 MB]

THPC147	TPS SR Kicker Prototype Installation Status*	kicker, injection, storage-ring, vacuum	3230
	Y.-H. Liu, C.K. Chan, C.-S. Chen, Y.L. Chu, K.H. Hsu, H.P. Hsueh, C.K. Kuan, C.Y. Kuo, C.-S. Yang NSRRC, Hsinchu, Taiwan
	The purpose of this paper is to illustrate the installation sequence of TPS SR kicker. Because of adding the rotation function in row direction, the position of every component of kicker must be very precise. The kicker magnet and EMI enclosure were fastened on the rotation motor plate which could rotate ±3.0 mrad. The ceramic chamber remain fixed on the bottom plate in order to let the bellow stress free during rotation. After installation, the inductance measurement and the high voltage breakdown test were also tested. The experimental results showed the good uniformity and reached the expected request. The field mapping and EMI prevention schemes will be tested in the future.

THPO023	Ageing of Airix Accelerating Units	controls, vacuum, pulsed-power, monitoring	3391
	A. Georges, H. Dzitko, B. Gouin, M. Mouillet CEA, Arpajon, France
	Airix is a linear accelerator producing a 60ns, 2kA, 19MeV electron beam. It has been operated in a single shot mode by the “Commissariat à l’Energie Atomique et aux Energies Alternatives” (CEA) for flash X-ray radiography purposes for 10 years. Its modular architecture increases the beam energy by quarter of a megavolt step: each cell delivers a 75ns impulsion of 250kV amplitude. Our aim is to guarantee a minimum lifetime for the cells and their pulse driver. To achieve it, we are operating a test-bed at a moderately low repetition rate (a couple of pulses per minute) for tens of thousands of pulses. Afterwards, we will run a series of both non-destructive and destructive analysis to identify the most stressed parts, and, if necessary, the means of increasing the cell lifetime. This paper describes the test-bed: a pair of cells and its driver, and the first results of these ageing tests.

THPO027	Novel Switching Power Supply utilizing SiC-JFET and its Potential for the Digital Accelerator	power-supply, induction, synchrotron, extraction	3400
	K. Okamura, T. Iwashita, K. Takayama, M. Wake KEK, Ibaraki, Japan K. Ise Tohoku Electric Power Co., Sendai, Japan Y. Osawa SUN-A Corporation, Miyoshi-City, Japan K. Takaki Iwate university, Morioka, Iwate, Japan
	Funding: Japan Science and Technology Agency 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 and obtained successful operation. However, series connection gives large complexity and less reliability. Among the various switching devices, a SiC-JFET is the promising candidates that substitute existing silicon MOSFET because it has ultrafast switching speed and voltage blocking capability. Therefore, we have started to develop new device in collaboration with device manufacturers. Switching and heat removal performance of the newly developed SiC-JFET and a future plan will be presented at the conference. T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011. ** K. Ise et al., IEEE Trans. Plasma Sci., pp. 730-736 (2011).

THPO036	Final Layout and Test Results of the Disconnect Switch for ALS Storage Ring RF System Power Supply	power-supply, klystron, vacuum, fibre-optics	3421
	S. Kwiatkowski, K.M. Baptiste, J. Julian, M.E. Kennedy LBNL, Berkeley, California, USA J. Miszczak SLCJ, Warsaw, Poland
	Funding: Work supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division, of the Department of Energy under contract No. DE-AC02-05CH11231. ALS is the 1.9 GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. The new RF system, which is now under construction will use two TH 2161B 300kW klystrons to power two single cell RF cavities. In the new design the existing conventional crow-bar klystron protection system will be replaced with the fast disconnect switch. The switch consist 24 high voltage IGBTs connected in series, equipped with static and dynamic balancing systems. The main advantage of using this new technology is faster action and virtually no stress for the components of the high voltage power supply. This paper will show the final lay-out and the test results of the production unit.

THPS002	Progress of the 2 MeV Electron Cooler Development for COSY-Jülich/HESR	electron, solenoid, dipole, proton	3427
	J. Dietrich, V. Kamerdzhiev FZJ, Jülich, Germany M.I. Bryzgunov, A.D. Goncharov, V.M. Panasyuk, V.V. Parkhomchuk, V.B. Reva, D.N. Skorobogatov BINP SB RAS, Novosibirsk, Russia
	The 2 MeV electron cooling system for COSY-Jülich was proposed to further boost the luminosity even in presence of strong heating effects of high-density internal targets. The project is funded since mid 2009. The design and construction of the cooler is accomplished in cooperation with the Budker Institute of Nuclear Physics in Novosibirsk, Russia. The 2 MeV cooler is also well suited in the start up phase of the High Energy Storage Ring (HESR) at FAIR in Darmstadt. It can be used for beam cooling at injection energy and is intended to test new features of the high energy electron cooler for HESR. The infrastructure necessary for the operation of the cooler in the COSY ring (radiation shielding, cabling, water cooling etc.) is established. The electron beam commissioning at BINP Novosibirsk is scheduled to start at May of 2011. First results are reported. Final commissioning at COSY-Jülich is planned for the end of 2011.

Paper

Title

Other Keywords

Page

MOPC046

CaCo: A Cavity Combiner for IOTs Amplifiers

cavity, simulation, storage-ring, HOM

181

B. Bravo, F. Mares, F. Pérez, P. Sanchez
CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
M.L. Langlois
ESRF, Grenoble, France

The ALBA storage ring uses six room temperature cavities; each one fed by two 80 kW IOTs amplifiers at 499.654 MHz. The power of the pair of transmitters is combined by a cavity combiner, CaCo. One of the design requirements of CaCo was that it continued working safely and with a good efficiency in the case of an IOT failure (asymmetrical mode). During the first asymmetric full power tests, in May 2010, with an active IOT and the other passive, the result was dramatic, the passive IOT broke in two parts after few hours of operation. This paper presents the experimental results and the electromagnetic field simulations of the asymmetrical operation mode of CaCo, i.e. one active IOT and the other passive, and analyze why the ceramic of the output tube of the passive IOT broke during the first performance of this mode. Also, it reports a possible solution to solve this problem.

MOPC090

Tuner Performance in the S1-global Cryomodule

cavity, controls, cryomodule, coupling

286

R. Paparella, A. Bosotti, C. Pagani
INFN/LASA, Segrate (MI), Italy
C. Albrecht, K. Jensch, L. Lilje
DESY, Hamburg, Germany
S. Barbanotti, Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, USA
H. Hayano, E. Kako, S. Noguchi, N. Ohuchi, Y. Yamamoto
KEK, Ibaraki, Japan

S1-Global is a collaborative effort of INFN, DESY, FNAL, SLAC and KEK, in the framework of the ILC global collaboration. For this project two cryomodules, 6 meter long and hosting four SC cavities each, were realized and successfully cold tested at KEK-STF. Three different cavity tuning systems, provided with fast tuning capability through piezoelectric actuators (piezo), were installed, and fully characterized in static and dynamic operation: Blade Tuner from INFN/FNAL, Saclay Tuner from DESY, Slide Jack Tuner from KEK. Finally, Lorenz Force Detuning (LFD) active compensation has been successfully achieved during high power cavity tests in pulsed RF regime, where active control of the LFD disturbance up to Hz-level residual detuning has been achieved with each type of tuning system up to the maximum gradient of each cavity. The installation procedures, together with the relevant results and their analyses are summarized in the paper.

MOPC142

25 Year Performance Review of the SLAC 5045 S-Band Klystron

klystron, cathode, linac, linear-collider

409

A. Jensen, A.S. Beebe, M.V. Fazio, A.A. Haase, E.N. Jongewaard, C. Pearson, D.W. Sprehn, A.E. Vlieks, L.E. Whicker
SLAC, Menlo Park, California, USA

Funding: This work was supported by the U.S. Department of Energy under contract DE-AC03-76SF00515.
The SLAC 5045 S-band klystron has proven to be a remarkably reliable high peak power tube. Originally developed in the 1980’s as an upgraded RF power source for the Stanford Linear Collider, it has continually powered the SLAC linac in support of numerous programs in particle physics and photon science. The large number of tubes built and operated (more than 800) coupled with accumulated running statistics over the last 25+ years represents an unprecedented wealth of operational experience for high pulse power klystrons in accelerator applications. Mean time between failures has continued to rise during this period and is frequently in excess of 100,000 hours during the last several years. Lifetime statistics as well as some important failure modes are presented and examined here.

MOPS029

Experiments with a Fast Chopper System for Intense Ion Beams

ion, electron, space-charge, simulation

664

H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner
IAP, Frankfurt am Main, Germany

Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

TUPC096

Solid-state Marx Generator Driven Einzel Lens Chopper

ion, ECRIS, acceleration, extraction

1233

K. Takayama, T. Arai
KEK, Ibaraki, Japan
T. Adachi, K.W. Leo
Sokendai, Ibaraki, Japan
A. Tokuchi
Pulsed Power Japan Laboratory Ltd., Kusatsu-shi Shiga, Japan

A new type of pulse chopper called an Einzel lens chopper* is described. The Einzel lens, placed immediately after an electron cyclotron resonance ion source, is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time. The barrier pulse is switched on only when a beam pulse is required. When the barrier pulse is off, the DC voltage across the Einzel lens reflects ions back upstream with almost zero velocity. The device has been actually used as a chopper for the KEK Digital Accelerator, which is a small-scale induction synchrotron employing no a large injector and capable of providing a wide variety of ions, has been constructed at KEK**. A He ion beam of 50 micro-ampere was chopped in 5 micro-sec with rise/fall time of 40 nsec.
* T.Adachi et al., “A Solid-State Marx Generator Driven Einzel Lens Chopper”, submitted to Appl. Phys. Lett.
** T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011.

TUPC178

Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun

laser, cathode, vacuum, gun

1443

R.R. Mammei, M. Poelker, R. Suleiman
JLAB, Newport News, Virginia, USA
J.L. McCarter
UVa, Charlottesville, Virginia, USA
T. Rao, J. Smedley
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. DOE
Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10^-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam.

TUPS004

Enhanced High-voltage Holding under Vacuum by Field Induced Adsorption of Gas on Metal Surfaces

vacuum, electron, cathode, plasma

1524

A. Simonin, L. Christin, L. Doceul, F. Faisse, F. Villecroze, H. de Esch
CEA, St Paul Lez Durance, France

*The energy of future neutral beam injector heating systems of fusion power plants ranges from 1 to 2 MeV. The beam line and the reactor chamber are under vacuum, while all the electrical components (power supplies) are connected to the injector via a long pressured (SF6) high-voltage (1-2 MV) transmission line. The bushing is a key component that ensures the barrier between the transmission line and the injector under vacuum; the design of this component is very challenging as it faces several stringent constraints due to the nuclear environment, in which high-voltage holding, mechanical stresses, and radiations are combined. Moreover, it is a high-voltage feed-through that allows supply of the accelerator electrodes with electrical power, active water cooling, and gas. In this paper, a new high-voltage bushing concept based on experimental findings previously obtained in the laboratory is presented. The main advantages of the concept is a reduction of the electron field emission under vacuum, which is an issue for conventional bushings, a reduction in size, and mechanical simplification of the device resulting in cost reduction and greater reliability."

TUPS079

Construction of a Novel Compact High Voltage Electrostatic Accelerator

vacuum, target, ion, ion-source

1722

P. Beasley, O. Heid
Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany

A compact demonstrator system based on a Cockcroft-Walton (or Greinacher) cascade has been successfully built and tested. The concept has been developed using modern materials and a different design philosophy, which in turn can then enable this novel configuration to operate at much higher voltage gradients. This paper explores the progress made over the past 18 months and future plans to utilise the technology to develop one such concept for an energy efficient 10MV, 100μA, tandem proton accelerator, with a <2m2 footprint. The development of such a compact high voltage particle accelerator, with high current capability has the potential to access a wide range of commercial opportunities outside the laboratory.

TUPS082

The LEBT Chopper for the Spiral 2 Project

controls, ion, vacuum, target

1731

A.C. Caruso, F. Consoli, G. Gallo, D. Rifuggiato, E. Zappalà
INFN/LNS, Catania, Italy
M. Di Giacomo
GANIL, Caen, France
A. Longhitano
ALTEK, San Gregorio (CATANIA), Italy

The Spiral 2 driver uses a slow chopper situated in the common section of the low energy beam transport line to change the beam intensity, to cut off the beam in case of critical loss and to avoid hitting the wheel structure of rotating targets. The device has to work up to 10 kV, 1 kHz repetition frequency rate and its design is based on standard power circuits, custom alarm board and vacuum feed-through. The paper summarizes the design principles and describes the test results of the final device which has been installed on the beam line test bench.

TUPS093

Automatic Measurement System for Electrical Verification of the LHC Superconducting Circuits

pick-up, instrumentation, superconducting-magnet, dipole

1756

A. Kotarba, M. Bednarek, P. Jurkiewicz, J. Ludwin, M. Talach
IFJ-PAN, Kraków, Poland
R. Mompo
CERN, Geneva, Switzerland

In the LHC machine, superconducting magnet circuits are used on a very large scale. The circuits, more than 1600, are all equipped with a complex set of instrumentation required for safe operation and diagnostics. The length of many circuits exceed 3 km. Due to risks of accidental damages during transport and assembly or misconnection of the circuits’ auxiliary components, it is necessary to perform an Electrical Quality Assurance (ELQA) campaign after every major intervention on a circuit and also after each thermal cycle of the machine. In order to be able to perform reliable tests on a circuit within a short time frame, a highly extensible automated mobile test system was designed and built. Four of these instruments were successfully used during the Hardware Commissioning phases of the LHC. This paper describes the hardware solutions used in the test system.

TUPS097

In-situ Experiments of Vacuum Discharge using Scanning Electron Microscopes

electron, vacuum, ion, site

1765

T. Muranaka, V.G. Ziemann
Uppsala University, Uppsala, Sweden
T. Blom, K. Leifer
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden

Funding: This work is supported by the 7th European Framework Program EuCARD under grant number 227579
Fundamental understandings of vacuum discharge mechanisms and involving surface damage is an indispensable for CLIC feasibility study. We have been conducting dc experiments inside a Scanning Electron Microscope (SEM) at Uppsala university in order to investigate localised breakdown phenomena. By using a SEM, we achieve the resolution of the electron probe in the few-nm range, which is of great advantage as the surface roughness of the polished accelerating structures is in the same scale. The high accelerating field of 1 GV/m is realised by biasing an electrode with 1 kV set above the sample with a gap of sub μm. Furthermore, a second SEM equipped with a Focused Ion Beam (FIB) is used to modify the topography of sample surfaces thus the geometrical dependence of field emissions and vacuum discharges could be studied. The FIB can be used for the surface damage analysis as well. We have demonstrated subsurface damage observations by using FIB to sputter a rectangular recess into the sample in the breakdown region. Those powerful surface analysis techniques can be productively applied to the study of fatigue in prototype accelerating structures.

WEPZ004

Solid Pulse Transforming Line for DWA

impedance, coupling, simulation, induction

2769

L. Zhang
CAEP/IFP, Mainyang, Sichuan, People's Republic of China

This paper introduces the research work about solid pulse transforming line for dielectric wall accelerator(DWA). We will discuss the impedence of the solid pulse transforming line due to different material. Some research of PCSS(photoconductive semiconductor switch),which was used for DWA, will also be described.

THOBB01

Evaluation of Performance, Reliability, and Risk for High Peak Power RF Sources from S-band through X-band for Advanced Accelerator Applications

klystron, linac, focusing, electron

2882

M.V. Fazio, C. Adolphsen, A. Jensen, C. Pearson, D.W. Sprehn, A.E. Vlieks, F. Wang
SLAC, Menlo Park, California, USA
M.V. Fazio
LANL, Los Alamos, New Mexico, USA

Historically linear accelerator development and the choice of frequency have been driven by the availability of RF power sources. This is also true at the present time and is particularly significant as new accelerators are being conceived and planned over a wide frequency range for FEL light sources and other applications. This paper evaluates the current state of the technology for high peak power RF sources from S-band through X-band including reliability and the facility risk incurred for applications demanding high availability and decades-long operation.

Slides THOBB01 [2.326 MB]

THPC147

TPS SR Kicker Prototype Installation Status*

kicker, injection, storage-ring, vacuum

3230

Y.-H. Liu, C.K. Chan, C.-S. Chen, Y.L. Chu, K.H. Hsu, H.P. Hsueh, C.K. Kuan, C.Y. Kuo, C.-S. Yang
NSRRC, Hsinchu, Taiwan

The purpose of this paper is to illustrate the installation sequence of TPS SR kicker. Because of adding the rotation function in row direction, the position of every component of kicker must be very precise. The kicker magnet and EMI enclosure were fastened on the rotation motor plate which could rotate ±3.0 mrad. The ceramic chamber remain fixed on the bottom plate in order to let the bellow stress free during rotation. After installation, the inductance measurement and the high voltage breakdown test were also tested. The experimental results showed the good uniformity and reached the expected request. The field mapping and EMI prevention schemes will be tested in the future.

THPO023

Ageing of Airix Accelerating Units

controls, vacuum, pulsed-power, monitoring

3391

A. Georges, H. Dzitko, B. Gouin, M. Mouillet
CEA, Arpajon, France

Airix is a linear accelerator producing a 60ns, 2kA, 19MeV electron beam. It has been operated in a single shot mode by the “Commissariat à l’Energie Atomique et aux Energies Alternatives” (CEA) for flash X-ray radiography purposes for 10 years. Its modular architecture increases the beam energy by quarter of a megavolt step: each cell delivers a 75ns impulsion of 250kV amplitude. Our aim is to guarantee a minimum lifetime for the cells and their pulse driver. To achieve it, we are operating a test-bed at a moderately low repetition rate (a couple of pulses per minute) for tens of thousands of pulses. Afterwards, we will run a series of both non-destructive and destructive analysis to identify the most stressed parts, and, if necessary, the means of increasing the cell lifetime. This paper describes the test-bed: a pair of cells and its driver, and the first results of these ageing tests.

THPO027

Novel Switching Power Supply utilizing SiC-JFET and its Potential for the Digital Accelerator

power-supply, induction, synchrotron, extraction

3400

K. Okamura, T. Iwashita, K. Takayama, M. Wake
KEK, Ibaraki, Japan
K. Ise
Tohoku Electric Power Co., Sendai, Japan
Y. Osawa
SUN-A Corporation, Miyoshi-City, Japan
K. Takaki
Iwate university, Morioka, Iwate, Japan

Funding: Japan Science and Technology Agency
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 and obtained successful operation. However, series connection gives large complexity and less reliability. Among the various switching devices, a SiC-JFET is the promising candidates that substitute existing silicon MOSFET because it has ultrafast switching speed and voltage blocking capability**. Therefore, we have started to develop new device in collaboration with device manufacturers. Switching and heat removal performance of the newly developed SiC-JFET and a future plan will be presented at the conference.
* T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011.
** K. Ise et al., IEEE Trans. Plasma Sci., pp. 730-736 (2011).

THPO036

Final Layout and Test Results of the Disconnect Switch for ALS Storage Ring RF System Power Supply

power-supply, klystron, vacuum, fibre-optics

3421

S. Kwiatkowski, K.M. Baptiste, J. Julian, M.E. Kennedy
LBNL, Berkeley, California, USA
J. Miszczak
SLCJ, Warsaw, Poland

Funding: Work supported by the Director, Office of Science, Office of Basic Energy Sciences, Materials Science and Engineering Division, of the Department of Energy under contract No. DE-AC02-05CH11231.
ALS is the 1.9 GeV third generation synchrotron light source which has been operating since 1993 at Berkeley National Lab. The new RF system, which is now under construction will use two TH 2161B 300kW klystrons to power two single cell RF cavities. In the new design the existing conventional crow-bar klystron protection system will be replaced with the fast disconnect switch. The switch consist 24 high voltage IGBTs connected in series, equipped with static and dynamic balancing systems. The main advantage of using this new technology is faster action and virtually no stress for the components of the high voltage power supply. This paper will show the final lay-out and the test results of the production unit.

THPS002

Progress of the 2 MeV Electron Cooler Development for COSY-Jülich/HESR

electron, solenoid, dipole, proton

3427

J. Dietrich, V. Kamerdzhiev
FZJ, Jülich, Germany
M.I. Bryzgunov, A.D. Goncharov, V.M. Panasyuk, V.V. Parkhomchuk, V.B. Reva, D.N. Skorobogatov
BINP SB RAS, Novosibirsk, Russia

The 2 MeV electron cooling system for COSY-Jülich was proposed to further boost the luminosity even in presence of strong heating effects of high-density internal targets. The project is funded since mid 2009. The design and construction of the cooler is accomplished in cooperation with the Budker Institute of Nuclear Physics in Novosibirsk, Russia. The 2 MeV cooler is also well suited in the start up phase of the High Energy Storage Ring (HESR) at FAIR in Darmstadt. It can be used for beam cooling at injection energy and is intended to test new features of the high energy electron cooler for HESR. The infrastructure necessary for the operation of the cooler in the COSY ring (radiation shielding, cabling, water cooling etc.) is established. The electron beam commissioning at BINP Novosibirsk is scheduled to start at May of 2011. First results are reported. Final commissioning at COSY-Jülich is planned for the end of 2011.