IPAC2012 - List of Keywords (site)

Paper	Title	Other Keywords	Page
MOPPC012	Reliability and Intervention Management for the LHC	controls, radiation, status, feedback	148
	K. Foraz, J.R. Cook, J. Coupard, B. Daudin, J. De Jonghe, F. B. Dos Santos Pedrosa, E.R. Fuentes, C. Garino, K. Golikov, S. Grillot, M.R. Jaekel, P. Sollander CERN, Geneva, Switzerland
	Since 2010, CERN has entered a mode of continuous operation of the LHC and its injectors, which implies the continuous operation of all the infrastructure and support systems. High reliability of the machines is crucial to meet the physics goals. This high reliability must be accompanied by a fast restart after programmed stops. Since 2010, an important effort has been put in place, to ease the coordination process during the programmed stops and to reinforce the management of the interventions (preparation, approval, follow-up, traceability, closure). This paper describes the difficulties from the first year related to this coordination, and the impact on operation. The tools developed for the management of the interventions, their assets and the effect on the reliability of the LHC will also be presented and discussed.

MOPPC081	Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field	electron, cavity, simulation, dipole	325
	G.V. Romanov, V.S. Kashikhin Fermilab, Batavia, USA
	In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low-Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of an RF cavity with beryllium windows in a solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to the RF electric field significantly modifies the performance of RF cavities. However, the magnetic field in a Helical Cooling Channel has a strong dipole component in addition to a solenoidal one. The dipole component essentially changes electron motion in a cavity compared to a pure solenoidal case, making dark current less focused at field emission sites. The simulation of a dark current dynamic in HCC performed with CST Studio Suite is presented in this paper.

MOPPC086	Accelerator Simulation - Beyond High Performance Computing	lattice, target, simulation, emittance	340
	S. James, G.M. Jung, B.C. Li, K. Muriki, H. Nishimura, Y. Qin, K. Song, C. Sun LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Accelerator modeling and simulation studies heavily rely on High Performance Computing (HPC). Public Cloud computing has opened a new service horizon for HPC by offering an on-demand, Virtual Private Cloud (VPC). Previously, we investigated using Amazon HPC public Cloud for lattice optimization applications and evaluated performance. In this research, we use the Amazon VPC technology to extend local HPC resources to provide a seamless, hybrid, and secure environment when the demand for computing capacity spikes. C. Sun et al., "HPC Cloud Applied to Lattice Optimization," Proc. PAC2011, New York, WEP151, p. 1767 (2011).

TUPPD069	Schottky-Enabled Photoemission and Dark Current Measurements - Toward an Alternate Approach to Fowler-Nordheim Plot Analysis	gun, laser, photon, cathode	1563
	E.E. Wisniewski, W. Gai, J.G. Power ANL, Argonne, USA H. Chen, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C.-X. Tang, L.X. Yan, Y. You TUB, Beijing, People's Republic of China A. Grudiev, W. Wuensch CERN, Geneva, Switzerland E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA
	Field-emitted dark current, a major gradient-limiting factor in RF cavities, is usually analyzed via Fowler-Nordheim (FN) plots. Traditionally, field emission is attributed to geometrical perturbations on the bulk surface whose field enhancement factor (beta) and the emitting area (A) can be extracted from the FN plot. Field enhancement factors extracted in this way are typically much too high (1 to 2 orders of magnitude) to be explainable by either the geometric projection model applied to the measured surface roughness or by field enhancement factors extracted from Schottky-enabled photoemission measurements. We compare traditional analysis of FN plots to an alternate approach employing local work function variation. This is illustrated by comparative analysis of recent dark current and Schottky-enabled photoemission data taken at Tsinghua S-band RF gun. We conclude by describing a possible experimental plan for discrimination of variation of local work function vs. local field enhancement.

TUPPP009	Status of the PETRA III Upgrade	undulator, shielding, radiation, vacuum	1620
	M. Bieler, K. Balewski, W. Drube, J. Keil, A. Kling DESY, Hamburg, Germany
	Since 2010 PETRA III, a third generation light source at DESY, has been running as a user facility, with all 14 undulator beam lines operational since autumn 2011. In order to fulfill the request for more beam time after the shut down of DORIS at the end of 2012, it was decided to add two additional halls at PETRA III, each housing 5 additional beam lines. Next to these two new halls about 100 m of the accelerator will be completely remodeled to install additional undulators. The upgrade should be accomplished during a 6 month shut down in 2013. In order to minimize this down time, it was decided to keep the existing accelerator tunnel in place. This has impact both on the mechanical connection between the accelerator and the experimental floor and on the design of the optical beam lines in the tunnel. In this paper the layout of the upgraded accelerator will be shown. The design status of the major components for the upgrade will be presented.

TUPPR004	ILC Conventional Facility in Asian Sites	linac, radiation, HLRF, cryogenics	1816
	A. Enomoto, M. Miyahara KEK, Ibaraki, Japan
	The international linear collider (ILC) is on a stage of preparing technical design report (TDR). Through value engineering to reduce civil construction costs, the tunnel configuration was changed from double- tunnel scheme to single. The double-tunnel schme accomodates superconducting accelerator modules and their power supplies indipendently. This is a very natural scheme for setting an accelerator and its power supply nearby and for preventing radiation damage of the power supply. However, the single-tunnel scheme was proposed to reduce cost, and to avoid such radiation problem three kinds of high-level (HLRF) RF systems are proposed. We report the comparison of ILC main linac costs and construction schedules between eight cases for combinations of diferent tunnel excavation methods and HLRF systems; then, we report the potential facility design for the Asian sites.

WEPPC083	Tunable 28 MHz Superconducting Cavity for RHIC	cavity, niobium, superconducting-cavity, superconducting-RF	2405
	C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA S.A. Belomestnykh, I. Ben-Zvi BNL, Upton, Long Island, New York, USA
	Funding: This research has been supported by a Department of Energy Small Business Innovative Research Phase II grant through the Nuclear Physics program office, contract #DE-SC0001215. Replacement of the normal conducting 28 MHz accelerating cavities in the RHIC ring with superconducting structures offers a number of advantages for the machine operation, including reduction of the number of cavities required and improved HOM performance. A prototype folded quarter wave structure is under construction at Niowave, Inc. to meet this need. This novel cavity geometry achieves the very low resonant frequency required with a relatively compact structure, and can provide the large tuning range required (~1% of the cavity frequency). Progress of the cavity fabrication will be presented along with room temperature RF measurements.

WEPPC096	Exploring the Effect of AL2O3 ALD Coating on a High Gradient ILC Single-Cell Cavity	cavity, niobium, SRF, electron	2441
	G.V. Eremeev, A-M. Valente-Feliciano, A.T. Wu JLAB, Newport News, Virginia, USA D. Gu ODU, Norfolk, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Encouraged by work at Argonne National Lab, we investigated atomic layer deposition technique for high gradient superconducting RF cavities at JLab with an ALD coating system of Old Dominion University located on the JLab site. The goal of this study was to look into the possibility of coating a dielectric layer on top of RF niobium surface at a lower temperature of 120 C as compared to ANL coatings at 200 C in order to preserve niobium pentooxide on niobium surface. The initial coatings showed complete, but non-uniform coatings of the surface with several areas exhibiting discoloration, which was probably due to the temperature variation during coatings. The initial coating showed a high RF losses, which were improved after discolored areas on the beam tubes were removed with HF rinse of the beam tubes only. The best result was 2·10⁹ low field Q0 and Eacc = 18 MV/m limited by available power.

WEPPD013	Status of the Vacuum System in J-PARC RCS	vacuum, ion, proton, electron	2522
	J. Kamiya, Y. Hikichi, M. Kinsho, M. Nishikawa, N. Ogiwara, T. Yanagibashi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	In the vacuum system of J-PARC Rapid cycling synchrotron (RCS), we use beam pipes and bellows whose materials are vacuum fired at 700~850 oC in order to eliminate atoms in their bulk who are origin of outgassing. Until now, beam power has been increased up to 300 kW. Pressure in synchrotron beam line increased when the high power beam was accelerated. However, increment of pressure has reduced during the continuous beam operation. It is because the molecules, which adsorb on surface of the wall of the vacuum chambers, desorb by an ion bombardment and a heat generation due to an eddy current. Because the atoms in the bulk is eliminated, desorption of the molecules, which adsorb on the surface, means the reduction of the outgassing from the wall. In this presentation, we will report the past situation of the vacuum system during the beam operation. In addition, we also show the status after the Great East Japan Earthquake.

WEPPD015	Saturation Behaviour of the LHC NEG Coated Beam Pipes	vacuum, simulation, injection, insertion	2525
	G. Bregliozzi, V. Baglin, J.M. Jimenez, G. Lanza, T. Porcelli CERN, Geneva, Switzerland
	In the CERN Large Hadron Collider (LHC), about 6 km of the UHV beam pipe are at room temperature and serve as experimental or utility insertions. TiZrV non-evaporable getter (NEG) coating is used to maintain the design pressure during beam operation. Molecular desorption due to dynamic effects is stimulated during protons operation at high intensity. This phenomenon produces an important gas load from the vacuum chamber walls which could lead to a partial or total saturation of the NEG coating. To keep the design vacuum performances and to schedule technical interventions for NEG re-activation, it is necessary to take in account all these aspects and to regularly evaluate the saturation level of the NEG coating. Experimental studies in a typical LHC vacuum sector were conducted in order to identify the best method to assess the saturation level of the beam pipe. Partial saturation of the NEG was performed and the effects in the variations of pressure reading, effective pumping speed, transmission and capture probability are analysed. Finally, based on these results, a detailed analysis of the NEG coating saturation level of some area of the LHC is presented and analysed.

WEPPD024	A Study of Vacuum Pressure in TPS Cells	photon, vacuum, electron, controls	2552
	L.H. Wu, J.-R. Chen, C.M. Cheng, G.-Y. Hsiung, C.S. Huang, Huang, Y.T. Huang NSRRC, Hsinchu, Taiwan
	Recently, the type-2 and type-3 TPS cells are installed and pumped down into vacuum status. The pumping down curves of the type-2 and type-3cells, including R03, R06, R07, R10, and R11, are recorded after on-site welding and after assembling without leakage, individually. In the R03, R06, R07, R10 cells, the pumping down curve after assembling without leakage is a little higher than that after on-site welding. In those four cells, the pumping down curve after assembling all vacuum components and pumps is similar. However, in the R11 cell, it was found that the pumping down curve after assembling without leakage is almost along that of after on-site welding. The slope of pumping down curve near 1 hour in the R11 cell is -1.52, while that in the R10 cell is -1.39. It means that the vacuum pressure in the R11 cell is apparently improved. It is confirmed that the vacuum chambers are cleaned by the same process and the assembling components are similar. Besides, the photon stopper chambers are all pre-baked to 200 oC for the same time. We try to investigate the residual gas analysis (RGA) data to find the true reasons.

WEPPD042	The Grounding System at TPS	synchrotron, emittance, insertion, controls	2606
	T.-S. Ueng, J.-C. Chang, J.-R. Chen, Y.-C. Lin NSRRC, Hsinchu, Taiwan
	An elaborately designed grounding system has been installed under the TPS construction site. The ground grid was installed sector by sector to comply with the building construction schedule. The ground resistance measurement of each sector was carried out right after the grid installation. The final ground resistance measurement for the whole grounding system was performed also right after its completion. The measured ground resistances of each sector were used to estimate the final TPS ground resistance, and it was compared to the final TPS ground measurement result. Also, the analysis with computer software is used to justify it. The low impedance of TPS grounding system, < 0.15 ohm, is to insure the safety of TPS personnel and instrumentation, also, to reduce the noise of electronic devices.

WEPPD082	Characterization of Photocathode Damage during High Current Operation of the Cornell ERL Photoinjector	ion, gun, vacuum, linac	2717
	J.M. Maxson, S.S. Karkare Cornell University, Ithaca, New York, USA I.V. Bazarov, S.A. Belomestnykh, L. Cultrera, D.S. Dale, J. Dobbins, B.M. Dunham, K. Finkelstein, R.P.K. Kaplan, V.O. Kostroun, Y. Li, X. Liu, F. Löhl, B. Pichler, P. Quigley, D.H. Rice, K.W. Smolenski, M. Tigner, V. Veshcherevich, Z. Zhao CLASSE, Ithaca, New York, USA
	The Cornell ERL Photoinjector prototype has recently demonstrated successful operation at 20 mA for 8 hours using a bi-alkali photocathode grown on a Si substrate. The photocathode film was grown off center, and remained relatively undamaged; however, upon removal from the gun, the substrate at the gun electrostatic center displayed significant visible damage. Here we will describe not only the parameters of that particular high current run, but a suite of post-operation surface morphology and crystallographic measurements, including X-ray fluorescence, X-ray diffraction, contact profilometry, scanning electron microscopy, performed about the damage site and photocathode film. The data indicate violent topological changes to the substrate surface, as well as significant induced crystallographic strain. Ion back-bombardment is proposed as a possible mechanism for damage, and a simple model for induced crystal strain is proposed (as opposed to ion induced sputtering), and is shown to have good qualitative agreement with the spatial distribution of damage.

THPPP043	Installation of 100-MeV Proton Linac for PEFP	linac, proton, DTL, klystron	3832
	Y.-S. Cho, S. Cha, J.S. Hong, J.-H. Jang, D.I. Kim, H.S. Kim, H.-J. Kwon, B.-S. Park, J.Y. Ryu, K.T. Seol, Y.-G. Song, S.P. Yun KAERI, Daejon, Republic of Korea
	Funding: This work was supported by the Ministry of Education, Science and Technology of the Korean Government. The Proton Engineering Frontier Project (PEFP) at Korea Atomic Energy Research Institute (KAERI) is developing a 100-MeV proton linac in order to supply 20-MeV and 100-MeV proton beams to users for proton beam application. The linac consists of a 50-keV injector, a 3-MeV radio frequency quadrupole (RFQ) and a 100-MeV drift tube linac (DTL). The operation of the 20-MeV part of linac at Daejeon site was finished on November 2011. It was disassembled and moved to the Gyeongju site for installation as a low energy part of the linac. We completed the fabrication and test of the accelerating structures. The installation of the proton linac started in December 2011 at the new project site. The user service is scheduled for 2013 through the beam commissioning in 2012. This work summarized the installation status of the proton linac.

THPPP045	Five Year Operation of the 20-MeV Proton Accelerator at KAERI	linac, proton, ion-source, ion	3838
	H.-J. Kwon, Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, B.-S. Park, J.Y. Ryu, K.T. Seol, Y.-G. Song, S.P. Yun KAERI, Daejon, Republic of Korea
	Funding: This work was supported by the Ministry of Science and Technology of the Korean Government. A 20-MeV proton linear accelerator has been operating since 2007 by Proton Engineering Frontier Project (PEFP) at Korea Atomic Energy Research Institute (KAERI), Daejeon site. The performance test of the accelerator itself has been done with limited operating conditions. In addition, the 20-MeV accelerator was used as a test bench of the 100-MeV accelerator components. Besides the machine study itself, it supplied proton beams to more than 1600 samples for users. The 20-MeV accelerator was disassembled at the end of 2011 and will be installed at Gyeong-Ju site as an injector for the 100-MeV linac in 2012. In this paper, the 5 year operation experiences of the 20-MeV linac at Daejeon site are summarized and the technical issues are discussed.

THPPR025	Operational Efficiency of the AIRIX Accelerator Since its Commissioning	electron, high-voltage, vacuum, induction	4017
	H. Dzitko, V. Bernigaud, A. Georges, B. Gouin, G. Grandpierre, M. Mouillet CEA, Pontfaverger-Moronvilliers, France L. Buche, Y. Collet, S. Combacon, G. Gobert, R. Nicolas, R. Reynaud CEA/DAM/DIF, Arpajon, France
	AIRIX is a high current (19 MeV, 2 kA) electron linear induction accelerator used as a 60 ns single shot X-ray source for hydrodynamic experiments. As single shot experiments are performed, the best performances and a high reliability level must be met for each experiment. This accelerator has been running for hydroshot experiments since 2000 and several thousands electron and X-ray beams have been produced so far. The functioning time of the AIRIX machine in the CEA/Moronvilliers test site is now coming to its end. From mid-2012, it will be then refurbished, dismounted and moved to another CEA test site. This paper draws up the report of AIRIX operations over this long eleven-year period. Maintenance policy, relative cost efficiency, reliability and performance results of the AIRIX accelerator over this period are dealt with and discussed.

Paper

Title

Other Keywords

Page

MOPPC012

Reliability and Intervention Management for the LHC

controls, radiation, status, feedback

148

K. Foraz, J.R. Cook, J. Coupard, B. Daudin, J. De Jonghe, F. B. Dos Santos Pedrosa, E.R. Fuentes, C. Garino, K. Golikov, S. Grillot, M.R. Jaekel, P. Sollander
CERN, Geneva, Switzerland

Since 2010, CERN has entered a mode of continuous operation of the LHC and its injectors, which implies the continuous operation of all the infrastructure and support systems. High reliability of the machines is crucial to meet the physics goals. This high reliability must be accompanied by a fast restart after programmed stops. Since 2010, an important effort has been put in place, to ease the coordination process during the programmed stops and to reinforce the management of the interventions (preparation, approval, follow-up, traceability, closure). This paper describes the difficulties from the first year related to this coordination, and the impact on operation. The tools developed for the management of the interventions, their assets and the effect on the reliability of the LHC will also be presented and discussed.

MOPPC081

Simulation of RF Cavity Dark Current in Presence of Helical Magnetic Field

electron, cavity, simulation, dipole

325

G.V. Romanov, V.S. Kashikhin
Fermilab, Batavia, USA

In order to produce muon beam of high enough quality to be used for a Muon Collider, its large phase space must be cooled several orders of magnitude. This task can be accomplished by ionization cooling. Ionization cooling consists of passing a high-emittance muon beam alternately through regions of low-Z material, such as liquid hydrogen, and very high accelerating RF cavities within a multi-Tesla solenoidal focusing channel. But first high power tests of an RF cavity with beryllium windows in a solenoidal magnetic field showed a dramatic drop in accelerating gradient due to RF breakdowns. It has been concluded that external magnetic fields parallel to the RF electric field significantly modifies the performance of RF cavities. However, the magnetic field in a Helical Cooling Channel has a strong dipole component in addition to a solenoidal one. The dipole component essentially changes electron motion in a cavity compared to a pure solenoidal case, making dark current less focused at field emission sites. The simulation of a dark current dynamic in HCC performed with CST Studio Suite is presented in this paper.

MOPPC086

Accelerator Simulation - Beyond High Performance Computing

lattice, target, simulation, emittance

340

S. James, G.M. Jung, B.C. Li, K. Muriki, H. Nishimura, Y. Qin, K. Song, C. Sun
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Accelerator modeling and simulation studies heavily rely on High Performance Computing (HPC). Public Cloud computing has opened a new service horizon for HPC by offering an on-demand, Virtual Private Cloud (VPC). Previously, we investigated using Amazon HPC public Cloud for lattice optimization applications and evaluated performance*. In this research, we use the Amazon VPC technology to extend local HPC resources to provide a seamless, hybrid, and secure environment when the demand for computing capacity spikes.
* C. Sun et al., "HPC Cloud Applied to Lattice Optimization," Proc. PAC2011, New York, WEP151, p. 1767 (2011).

TUPPD069

Schottky-Enabled Photoemission and Dark Current Measurements - Toward an Alternate Approach to Fowler-Nordheim Plot Analysis

gun, laser, photon, cathode

1563

E.E. Wisniewski, W. Gai, J.G. Power
ANL, Argonne, USA
H. Chen, Y.-C. Du, Hua, J.F. Hua, W.-H. Huang, C.-X. Tang, L.X. Yan, Y. You
TUB, Beijing, People's Republic of China
A. Grudiev, W. Wuensch
CERN, Geneva, Switzerland
E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA

Field-emitted dark current, a major gradient-limiting factor in RF cavities, is usually analyzed via Fowler-Nordheim (FN) plots. Traditionally, field emission is attributed to geometrical perturbations on the bulk surface whose field enhancement factor (beta) and the emitting area (A) can be extracted from the FN plot. Field enhancement factors extracted in this way are typically much too high (1 to 2 orders of magnitude) to be explainable by either the geometric projection model applied to the measured surface roughness or by field enhancement factors extracted from Schottky-enabled photoemission measurements. We compare traditional analysis of FN plots to an alternate approach employing local work function variation. This is illustrated by comparative analysis of recent dark current and Schottky-enabled photoemission data taken at Tsinghua S-band RF gun. We conclude by describing a possible experimental plan for discrimination of variation of local work function vs. local field enhancement.

TUPPP009

Status of the PETRA III Upgrade

undulator, shielding, radiation, vacuum

1620

M. Bieler, K. Balewski, W. Drube, J. Keil, A. Kling
DESY, Hamburg, Germany

Since 2010 PETRA III, a third generation light source at DESY, has been running as a user facility, with all 14 undulator beam lines operational since autumn 2011. In order to fulfill the request for more beam time after the shut down of DORIS at the end of 2012, it was decided to add two additional halls at PETRA III, each housing 5 additional beam lines. Next to these two new halls about 100 m of the accelerator will be completely remodeled to install additional undulators. The upgrade should be accomplished during a 6 month shut down in 2013. In order to minimize this down time, it was decided to keep the existing accelerator tunnel in place. This has impact both on the mechanical connection between the accelerator and the experimental floor and on the design of the optical beam lines in the tunnel. In this paper the layout of the upgraded accelerator will be shown. The design status of the major components for the upgrade will be presented.

TUPPR004

ILC Conventional Facility in Asian Sites

linac, radiation, HLRF, cryogenics

1816

A. Enomoto, M. Miyahara
KEK, Ibaraki, Japan

The international linear collider (ILC) is on a stage of preparing technical design report (TDR). Through value engineering to reduce civil construction costs, the tunnel configuration was changed from double- tunnel scheme to single. The double-tunnel schme accomodates superconducting accelerator modules and their power supplies indipendently. This is a very natural scheme for setting an accelerator and its power supply nearby and for preventing radiation damage of the power supply. However, the single-tunnel scheme was proposed to reduce cost, and to avoid such radiation problem three kinds of high-level (HLRF) RF systems are proposed. We report the comparison of ILC main linac costs and construction schedules between eight cases for combinations of diferent tunnel excavation methods and HLRF systems; then, we report the potential facility design for the Asian sites.

WEPPC083

Tunable 28 MHz Superconducting Cavity for RHIC

cavity, niobium, superconducting-cavity, superconducting-RF

2405

C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA
S.A. Belomestnykh, I. Ben-Zvi
BNL, Upton, Long Island, New York, USA

Funding: This research has been supported by a Department of Energy Small Business Innovative Research Phase II grant through the Nuclear Physics program office, contract #DE-SC0001215.
Replacement of the normal conducting 28 MHz accelerating cavities in the RHIC ring with superconducting structures offers a number of advantages for the machine operation, including reduction of the number of cavities required and improved HOM performance. A prototype folded quarter wave structure is under construction at Niowave, Inc. to meet this need. This novel cavity geometry achieves the very low resonant frequency required with a relatively compact structure, and can provide the large tuning range required (~1% of the cavity frequency). Progress of the cavity fabrication will be presented along with room temperature RF measurements.

WEPPC096

Exploring the Effect of AL2O3 ALD Coating on a High Gradient ILC Single-Cell Cavity

cavity, niobium, SRF, electron

2441

G.V. Eremeev, A-M. Valente-Feliciano, A.T. Wu
JLAB, Newport News, Virginia, USA
D. Gu
ODU, Norfolk, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Encouraged by work at Argonne National Lab, we investigated atomic layer deposition technique for high gradient superconducting RF cavities at JLab with an ALD coating system of Old Dominion University located on the JLab site. The goal of this study was to look into the possibility of coating a dielectric layer on top of RF niobium surface at a lower temperature of 120 C as compared to ANL coatings at 200 C in order to preserve niobium pentooxide on niobium surface. The initial coatings showed complete, but non-uniform coatings of the surface with several areas exhibiting discoloration, which was probably due to the temperature variation during coatings. The initial coating showed a high RF losses, which were improved after discolored areas on the beam tubes were removed with HF rinse of the beam tubes only. The best result was 2·10⁹ low field Q0 and Eacc = 18 MV/m limited by available power.

WEPPD013

Status of the Vacuum System in J-PARC RCS

vacuum, ion, proton, electron

2522

J. Kamiya, Y. Hikichi, M. Kinsho, M. Nishikawa, N. Ogiwara, T. Yanagibashi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

In the vacuum system of J-PARC Rapid cycling synchrotron (RCS), we use beam pipes and bellows whose materials are vacuum fired at 700~850 oC in order to eliminate atoms in their bulk who are origin of outgassing. Until now, beam power has been increased up to 300 kW. Pressure in synchrotron beam line increased when the high power beam was accelerated. However, increment of pressure has reduced during the continuous beam operation. It is because the molecules, which adsorb on surface of the wall of the vacuum chambers, desorb by an ion bombardment and a heat generation due to an eddy current. Because the atoms in the bulk is eliminated, desorption of the molecules, which adsorb on the surface, means the reduction of the outgassing from the wall. In this presentation, we will report the past situation of the vacuum system during the beam operation. In addition, we also show the status after the Great East Japan Earthquake.

WEPPD015

Saturation Behaviour of the LHC NEG Coated Beam Pipes

vacuum, simulation, injection, insertion

2525

G. Bregliozzi, V. Baglin, J.M. Jimenez, G. Lanza, T. Porcelli
CERN, Geneva, Switzerland

In the CERN Large Hadron Collider (LHC), about 6 km of the UHV beam pipe are at room temperature and serve as experimental or utility insertions. TiZrV non-evaporable getter (NEG) coating is used to maintain the design pressure during beam operation. Molecular desorption due to dynamic effects is stimulated during protons operation at high intensity. This phenomenon produces an important gas load from the vacuum chamber walls which could lead to a partial or total saturation of the NEG coating. To keep the design vacuum performances and to schedule technical interventions for NEG re-activation, it is necessary to take in account all these aspects and to regularly evaluate the saturation level of the NEG coating. Experimental studies in a typical LHC vacuum sector were conducted in order to identify the best method to assess the saturation level of the beam pipe. Partial saturation of the NEG was performed and the effects in the variations of pressure reading, effective pumping speed, transmission and capture probability are analysed. Finally, based on these results, a detailed analysis of the NEG coating saturation level of some area of the LHC is presented and analysed.

WEPPD024

A Study of Vacuum Pressure in TPS Cells

photon, vacuum, electron, controls

2552

L.H. Wu, J.-R. Chen, C.M. Cheng, G.-Y. Hsiung, C.S. Huang, Huang, Y.T. Huang
NSRRC, Hsinchu, Taiwan

Recently, the type-2 and type-3 TPS cells are installed and pumped down into vacuum status. The pumping down curves of the type-2 and type-3cells, including R03, R06, R07, R10, and R11, are recorded after on-site welding and after assembling without leakage, individually. In the R03, R06, R07, R10 cells, the pumping down curve after assembling without leakage is a little higher than that after on-site welding. In those four cells, the pumping down curve after assembling all vacuum components and pumps is similar. However, in the R11 cell, it was found that the pumping down curve after assembling without leakage is almost along that of after on-site welding. The slope of pumping down curve near 1 hour in the R11 cell is -1.52, while that in the R10 cell is -1.39. It means that the vacuum pressure in the R11 cell is apparently improved. It is confirmed that the vacuum chambers are cleaned by the same process and the assembling components are similar. Besides, the photon stopper chambers are all pre-baked to 200 oC for the same time. We try to investigate the residual gas analysis (RGA) data to find the true reasons.

WEPPD042

The Grounding System at TPS

synchrotron, emittance, insertion, controls

2606

T.-S. Ueng, J.-C. Chang, J.-R. Chen, Y.-C. Lin
NSRRC, Hsinchu, Taiwan

An elaborately designed grounding system has been installed under the TPS construction site. The ground grid was installed sector by sector to comply with the building construction schedule. The ground resistance measurement of each sector was carried out right after the grid installation. The final ground resistance measurement for the whole grounding system was performed also right after its completion. The measured ground resistances of each sector were used to estimate the final TPS ground resistance, and it was compared to the final TPS ground measurement result. Also, the analysis with computer software is used to justify it. The low impedance of TPS grounding system, < 0.15 ohm, is to insure the safety of TPS personnel and instrumentation, also, to reduce the noise of electronic devices.

WEPPD082

Characterization of Photocathode Damage during High Current Operation of the Cornell ERL Photoinjector

ion, gun, vacuum, linac

2717

J.M. Maxson, S.S. Karkare
Cornell University, Ithaca, New York, USA
I.V. Bazarov, S.A. Belomestnykh, L. Cultrera, D.S. Dale, J. Dobbins, B.M. Dunham, K. Finkelstein, R.P.K. Kaplan, V.O. Kostroun, Y. Li, X. Liu, F. Löhl, B. Pichler, P. Quigley, D.H. Rice, K.W. Smolenski, M. Tigner, V. Veshcherevich, Z. Zhao
CLASSE, Ithaca, New York, USA

The Cornell ERL Photoinjector prototype has recently demonstrated successful operation at 20 mA for 8 hours using a bi-alkali photocathode grown on a Si substrate. The photocathode film was grown off center, and remained relatively undamaged; however, upon removal from the gun, the substrate at the gun electrostatic center displayed significant visible damage. Here we will describe not only the parameters of that particular high current run, but a suite of post-operation surface morphology and crystallographic measurements, including X-ray fluorescence, X-ray diffraction, contact profilometry, scanning electron microscopy, performed about the damage site and photocathode film. The data indicate violent topological changes to the substrate surface, as well as significant induced crystallographic strain. Ion back-bombardment is proposed as a possible mechanism for damage, and a simple model for induced crystal strain is proposed (as opposed to ion induced sputtering), and is shown to have good qualitative agreement with the spatial distribution of damage.

THPPP043

Installation of 100-MeV Proton Linac for PEFP

linac, proton, DTL, klystron

3832

Y.-S. Cho, S. Cha, J.S. Hong, J.-H. Jang, D.I. Kim, H.S. Kim, H.-J. Kwon, B.-S. Park, J.Y. Ryu, K.T. Seol, Y.-G. Song, S.P. Yun
KAERI, Daejon, Republic of Korea

Funding: This work was supported by the Ministry of Education, Science and Technology of the Korean Government.
The Proton Engineering Frontier Project (PEFP) at Korea Atomic Energy Research Institute (KAERI) is developing a 100-MeV proton linac in order to supply 20-MeV and 100-MeV proton beams to users for proton beam application. The linac consists of a 50-keV injector, a 3-MeV radio frequency quadrupole (RFQ) and a 100-MeV drift tube linac (DTL). The operation of the 20-MeV part of linac at Daejeon site was finished on November 2011. It was disassembled and moved to the Gyeongju site for installation as a low energy part of the linac. We completed the fabrication and test of the accelerating structures. The installation of the proton linac started in December 2011 at the new project site. The user service is scheduled for 2013 through the beam commissioning in 2012. This work summarized the installation status of the proton linac.

THPPP045

Five Year Operation of the 20-MeV Proton Accelerator at KAERI

linac, proton, ion-source, ion

3838

H.-J. Kwon, Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, B.-S. Park, J.Y. Ryu, K.T. Seol, Y.-G. Song, S.P. Yun
KAERI, Daejon, Republic of Korea

Funding: This work was supported by the Ministry of Science and Technology of the Korean Government.
A 20-MeV proton linear accelerator has been operating since 2007 by Proton Engineering Frontier Project (PEFP) at Korea Atomic Energy Research Institute (KAERI), Daejeon site. The performance test of the accelerator itself has been done with limited operating conditions. In addition, the 20-MeV accelerator was used as a test bench of the 100-MeV accelerator components. Besides the machine study itself, it supplied proton beams to more than 1600 samples for users. The 20-MeV accelerator was disassembled at the end of 2011 and will be installed at Gyeong-Ju site as an injector for the 100-MeV linac in 2012. In this paper, the 5 year operation experiences of the 20-MeV linac at Daejeon site are summarized and the technical issues are discussed.

THPPR025

Operational Efficiency of the AIRIX Accelerator Since its Commissioning

electron, high-voltage, vacuum, induction

4017

H. Dzitko, V. Bernigaud, A. Georges, B. Gouin, G. Grandpierre, M. Mouillet
CEA, Pontfaverger-Moronvilliers, France
L. Buche, Y. Collet, S. Combacon, G. Gobert, R. Nicolas, R. Reynaud
CEA/DAM/DIF, Arpajon, France

AIRIX is a high current (19 MeV, 2 kA) electron linear induction accelerator used as a 60 ns single shot X-ray source for hydrodynamic experiments. As single shot experiments are performed, the best performances and a high reliability level must be met for each experiment. This accelerator has been running for hydroshot experiments since 2000 and several thousands electron and X-ray beams have been produced so far. The functioning time of the AIRIX machine in the CEA/Moronvilliers test site is now coming to its end. From mid-2012, it will be then refurbished, dismounted and moved to another CEA test site. This paper draws up the report of AIRIX operations over this long eleven-year period. Maintenance policy, relative cost efficiency, reliability and performance results of the AIRIX accelerator over this period are dealt with and discussed.