IPAC2015 - Classification: 7: Accelerator Technology / T14

Paper	Title	Page
MOBD1	Preliminary Design of the High-Luminosity LHC Beam Screen with Shielding	60
	C. Garion, V. Baglin, R. Kersevan CERN, Geneva, Switzerland
	A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, they have to shield the cold mass from physics debris coming from the nearby beam collision points. To such purpose, energy absorbers made of tungsten alloy are installed onto the beam screen in the vacuum system. In this contribution, the proposed mechanical design is shown; it covers different thermomechanical aspects such as the behaviour during a magnet quench and the heat transfer from the tungsten absorbers to the cooling tubes. Assembly and manufacturing tolerances are also considered to evaluate the impact on the aperture. Results obtained with a short prototype assembly test are discussed.
	Slides MOBD1 [3.089 MB]
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WEPMA003	Vacuum System Design for the Sirius Storage Ring	2744
	R.M. Seraphim, O.R. Bagnato, R.O. Ferraz, H.G. Filho, G.R. Gomes, M. Nardin, R.F. Oliveira, B.M. Ramos, A.R.D. Rodrigues, M.B. Silva, T.M. da Rocha LNLS, Campinas, Brazil
	Sirius is a 3 GeV 4th-generation light source under construction by the Brazilian Synchrotron Light Laboratory (LNLS). Sirius will have a low emittance storage ring, 0.28 nm-rad, based on 20 cells of a highly compact lattice – 5-bend achromat (5BA). This lattice concept leaves very little space for components and therefore requires narrow vacuum chambers with tight mechanical tolerances. Most of the storage ring vacuum chambers will be made of OFS copper and have a circular cross section with inner diameter of 24 mm and a wall thickness of 1 mm. The unused synchrotron radiation will be distributed along the water cooled walls of the chambers. Due to the small conductance of the chambers, the vacuum pumping will be based on distributed concept and then non-evaporable getter (NEG) coating will be extensively used, with more than 95% of the chambers being coated. In this paper, we present an overview of the storage ring vacuum system and the main vacuum chambers fabrication developments.
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WEPMA034	Bakeout Concept for the HESR at FAIR	2832
	H. Jagdfeld, N. Bongers, P. Chaumet, F.M. Esser, F. Jordan, F. Klehr, G. Langenberg, U. Pabst, L. Semke FZJ, Jülich, Germany
	Forschungszentrum Jülich has taken the leadership of a consortium being responsible for the design of the High-Energy Storage Ring (HESR) going to be part of the FAIR project at GSI. The HESR is designed for antiprotons but can be used for heavy ion experiments as well. Therefore the vacuum is expected to be 10^-11 mbar or better. To achieve this also in the curved sections where 44 bent dipole magnets with a length of around 4.5 m will be installed, NEG coated dipole chambers will be used to reach the needed pumping speed and capacity. For activation of the NEG-material a bakeout system must be installed. The bakeout concept including the layout of the control system and the systematization of the heater packages for all components of the vacuum system are presented. Also the special design of the heater jackets inside the dipole will be shown where the geometrical parameters are very critical and space is very limited. The results of the simulation of temperature distribution in the dipole iron are compared to temperature measurements carried out at a testbench with different layouts of the heater jackets. The final design of the dipole heater jackets will be illustrated.
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WEPMA059	Degassing of Kicker Magnet by In-situ Bake-out Method	2911
	J. Kamiya, Y. Hikichi, M. Kinsho, N. Ogiwara JAEA/J-PARC, Tokai-mura, Japan
	New method of in-situ degassing of the kicker magnet in the beam line has been developed. The heater and heat shielding panels are installed in the vacuum chamber in this method. The heater was designed considering the maintainability. The graphite was selected as the heater and the high melting point metals were used as the reflectors just near the heater. The thermal analysis and the temperature measurement with the designed heater was performed. The ideal temperature distribution for the kicker degassing was obtained. The outgassing of the graphite during rising the temperature was measured. The result showed that the outgassing was extremely suppressed by the first heating. This means the outgassing of the graphite heater was negligible as long as it is used in the beam line without exposure to the air.
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WEPMN021	Design and Research of Secondary Electron Emission Test Equipment with Low Electron Energy	2970
	Y.H. Xu, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, B. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	In particle accelerators, the secondary electrons resulting from the interaction between particles and vacuum chamber have a great impact on beam quality. Especially for positron, proton and heavy ion accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. We have studied the secondary electron emission (SEE) of metal used for accelerators. A secondary electron emission measurement system with low electron energy has been designed and used to measure the SEE yield of metal and non-evaporable getter materials. With the equipment, we have obtained the characteristic of the SEE yield of stainless steel and oxygen free copper (OFC).
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WEPMN022	Optimization Design of Ti Cathode in Ceramic Pipe Film Coating Based on the Simulation Result of CST	2973
	J. Wang, L. Fan, Y.Z. Hong, X.T. Pei, Y. Wang, W. Wei, Y.H. Xu, B. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	The injection chamber at Hefei Light Source II (HLS II) consists of four ceramic vacuum chambers whose inner surface were coated with TiN thin film. The cross section of ceramic pipes is special racetrack structure. In order to improve the uniformity of the film, the structure of the cathode Ti plate needed to be optimized. In this article, CST PARTICLE STUDIOTM software had been used to simulate the influence of different target structure on discharge electric field distribution and electrons trajectories. Furthermore, the reliability of the simulation were analysed compared with the experimental results. Also, we put forward the optimization design of Ti cathode structure which could satisfy the requirement of uniformity of the thin film.
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WEPMN023	Vacuum System of the Storage Ring of HLS-II	2976
	Y. Wang, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, W. Wei, B. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	HLS storage-ring has been operated for more than twenty-five years. In 2014 we began to upgrade the machine, which is called HLS-II. The emittance is reduced to 40 nmrad, five insertion devices are added and the injection energy increases to 800MeV. Now the machine commissioning has already been completed. The typical life time is 300 mins at 300mA, 800MeV. The average pressure of static and dynamic vacuum are below 2×10^-8 Pa and 1.2×10-7 Pa respectively. The design, installation and commissioning of the vacuum system of the storage ring are detailedly stated in this paper.
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WEPMN028	Preliminary Mechanical Design of Ceramic Pipe Film Coating Equipment at Hefei Light Source II	2988
	J. Lu NPU, Xi'an Shaanxi, People's Republic of China L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, Y.H. Xu, B. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Ceramic vacuum chambers are important components of the injection chamber at Hefei Light Source II (HLS II). The length of each Ceramic vacuum chamber is 350 mm and their inner surface is coated with TiN thin film whose properties are low secondary electron yield (SEY), good electrical conductivity, stability of performance, ability to block hydrogen permeation. Considering that the cross section of Ceramic pipe is racetrack structure, Ti plate was chose as the cathode to improve TiN thin film deposition rate. Meanwhile, the authors designed a motor drive magnetron sputtering film coating equipment to obtain uniform TiN film.
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WEPHA003	Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown	3100
	V. Bencini, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, C. Yin Vallgren CERN, Geneva, Switzerland
	During the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+.
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WEPHA004	Present Quality Assurance for the LHC Beam Vacuum System and its Future Improvement	3103
	J. Sestak, V. Baglin, G. Bregliozzi, P. Chiggiato CERN, Geneva, Switzerland
	During the Long Shutdown 1 (LS1), the LHC beam vacuum system was upgraded to minimize dynamic vacuum effects like stimulated desorption and beam-induced electron multipacting. A quality assurance plan was mandatory due to the demanding vacuum performance and the limited access to the equipment during the following operation period. Laboratory assessment tests and underground interventions were performed following well-defined and approved procedures. All vacuum related activities were documented and written reports stored in dedicated databases. Quality controls were performed to find mechanical, cabling and equipment functionality non-conformities. Possible issues were identified, classified and tracked in a non-conformity database for future corrective actions. This contribution give an overview of the quality assurance policy followed during the LS1 and the non-conformities reported after quality control. Possible future improvements are also discussed.
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WEPHA005	Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules	3106
	C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan CERN, Geneva, Switzerland
	Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.
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WEPHA006	Recommissioning of the COLDEX Experiment at CERN	3109
	R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis CERN, Geneva, Switzerland
	COLDEX (Cold bore Experiment), installed in the Super Proton Synchrotron (SPS) at CERN, is a test vacuum sector used in 2001-2004 to validate the Large Hadron Collider (LHC) cryogenic vacuum system with LHC type proton beams. Its cryostat houses a 2.2 m long copper perforated beam screen surrounded by a stainless steel cold bore, both individually temperature controlled down to 5 and 3 K, respectively. In the framework of the development for the High Luminosity upgrade of the LHC (HL-LHC), COLDEX has been re-commissioned in 2014. The objective of this re-commissioning is the validation of the performance of amorphous carbon coatings at cryogenic temperature with LHC type beams. The existing COLDEX beam screen has been dismounted and carbon coated, while a complete overhaul of the vacuum, cryogenic and control systems has been carried out. This contribution describes the phases of re-commissioning and reviews the current experimental set-up. An overview of the possible measurements with COLDEX, in view of its HL-LHC experimental program, is also presented.
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WEPHA007	Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment	3112
	R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan CERN, Geneva, Switzerland
	Extrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs.
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WEPHA009	Propagation of Radioactive Contaminants Along the Isolde Beamline	3115
	R. Kersevan, M. Ady, A. Dorsival, A. Gottberg, M. Maietta, G. Vandoni CERN, Geneva, Switzerland
	The vacuum system of RIB facilities is entirely hermetical, with storage of effluents and controlled release to atmosphere after a decay time. In Isolde, distributed primary pumping is sectorized in three parts, but all effluents are conveyed together in a unique tank. Thus, highly contaminated gas from the target and front end may be mixed with less contaminated gas from the beam transfer lines. This study aims at analysing and quantifying the distribution and propagation of neutral rare gas radioactive isotopes along the Isolde beam-line by numerical simulation (steady-state and time resolved Test-Particle Monte-Carlo, Molflow+) and experimental means. The time-resolved Monte-Carlo integrates decay time for the propagating species. To measure the distribution of contaminants, sampling filters are installed at the exhaust of the vacuum turbo-molecular pumps. Comparison between simulation and experiment shows excellent agreement, confirming the pertinence of the Monte-Carlo tool to radioactive species propagation. The filtering effect of magnetic sectors, the RFQ Cooler, and Buncher on the propagating neutral isotopes are quantified.
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WEPHA010	The Vacuum System of the Extra-Low Energy Antiproton Decelerator ELENA at CERN	3119
	R. Kersevan CERN, Geneva, Switzerland
	The Extra-Low ENergy Antiproton decelerator (ELENA) project is under way since 2011. In the past 3 years, it has considerably evolved into a detailed design for the ring and the transfer lines. It is a small machine, ~30 m in circumference, with a rather tight specification for the average pressure seen by the anti-proton beams injected by the anti-proton decelerator (AD). The average pressure in ELENA must be limited to 4x10^-12 mbar (H2-equivalent) in order to limit the charge-exchange losses during the rather long deceleration process (several tens of seconds), during which the energy of the beam is reduced and the electron-cooler is used twice in order to decrease the transverse emittance of the anti-proton beam. This paper will discuss the design of the chambers of the injection line, extraction line and the ring. It will also mention the actual status of the vacuum system for the transfer lines to the experiments, LNE, which are under finalisation. The results of detailed 3D simulations made with the test-particle montecarlo code Molflow+ will be discussed, alongside with the choice for the pumping system, mainly distributed NEG-coatings and integrated NEG/ion-pumps.
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WEPHA011	Photodesorption and Electron Yield Measurements of Thin Film Coatings for Future Accelerators	3123
	R. Kersevan, M. Ady, P. Chiggiato CERN, Geneva, Switzerland T. Honda, Y. Tanimoto KEK, Tsukuba, Japan
	The performance of future accelerators could be limited by electron cloud phenomena and high photodesorption yields. For such a reason, the study of secondary electron and photodesorption yields of vacuum materials is essential. The eradication or mitigation of both secondary electron and molecule desorption could strongly reduce the beam scrubbing time and increase the availability of nominal beams for experiments. Surface modifications with the desired characteristics can be achieved by thin-film coatings, in particular made of amorphous carbon and non-evaporable getters (NEG). In the framework of a new collaboration, several vacuum chambers have been produced, and different coatings on each of them have been applied. The samples were then irradiated at KEK’s Photon Factory with SR light of 4 keV critical energy during several days, allowing the measurement of the photodesorption yield as a function of the photon dose. This paper presents the experiment and briefly summarizes the preliminary photodesorption and photoelectron yield data of different coatings. The results can be used for future machine design with similar conditions, such as the FCC-hh.
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WEPHA012	Synchrotron Radiation Distribution and Related Outgassing and Pressure Profiles for the HL-LHC Final Focus Magnets	3127
	R. Kersevan CERN, Geneva, Switzerland
	The HL-LHC final focus area, from D2 to the interaction point, has been modelled based on the latest vacuum chamber geometry and orbits. The synchrotron radiation (SR) fans are computed using the Monte Carlo code SYNRAD⁺, in the dipole approximation regime. The angular and energy dependence of the reflectivity of the copper surfaces is considered, as well as the surface roughness. Once the SR distributions are computed, they are converted into outstanding profiles by using data available in literature. The test-particle Monte Carlo code Molflow+ is then used and the related pressure profiles and gas density distribution are computed. This allows an optimization of the pattern of the perforations on the tungsten-shielded beam screen proposed for this area. It is shown that the resultant gas density is below the limit dictated by the ATLAS and CMS detectors.
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WEPHA019	Development and Production of Non-evaporable Getter Coatings for MAX IV	3145
	P. Costa Pinto, B. Bártová, B. Holliger, S. Marques Dos Santos, V. Nistor, A. Sapountzis, M. Taborelli, I. Wevers CERN, Geneva, Switzerland J. Ahlbäck, E. Al-Dmour, M.J. Grabski, C. Pasquino MAX-lab, Lund, Sweden
	MAX IV is presently under construction at Lund, Sweden, and the first beam for the production of synchrotron radiation is expected to circulate in 2016. The whole set of 3-GeV ring beam pipes is coated with Ti-Zr-V Non Evaporable Getter (NEG) thin film in order to fulfil the average pressure requirement of 1x10^-9 mbar, despite the compact magnet layout and the large aspect ratio of the vacuum chambers. In this work, we present the optimisations of the coating process performed at CERN to coat different geometries and mechanical assembling used for the MAX IV vacuum chambers; the morphology of the thin films is analysed by Scanning Electron Microscopy; the composition and thickness is measured by Energy Dispersive X-ray analysis; the activation of the NEG thin film is monitored by X-ray Photoemission Spectroscopy; the vacuum performance of the coated beam pipes is evaluated by the measurement of hydrogen sticking coefficient. The results of the coating production characterisation for the 84 units coated at CERN are presented.
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WEPHA020	Titanium Coating of Ceramics for Accelerator Applications	3148
	W. Vollenberg, P. Costa Pinto, B. Holliger, A. Sapountzis, M. Taborelli CERN, Geneva, Switzerland
	Titanium thin films can be deposited on ceramics, in particular alumina, without adherence problems. Even after air exposure their secondary electron yield is low compared to alumina and can be further reduced by conditioning or beam scrubbing. In addition, depending on the film thickness, titanium provides different surface resistances that fulfil requirements of ceramics in particle accelerators. Titanium thin films (MOhm square range) are used to suppress electron multipacting and evacuate charges from ceramic surfaces. Thicker films (5-25 Ω square range) are applied to lower the surface resistance so that the beam impedance is reduced. In this contribution, we present the results of a development aimed at coating 2-meter long alumina vacuum chambers with a uniform surface resistivity by a dedicated DC magnetron sputtering configuration.
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WEPHA046	Outgassing Analysis During Transport for 14m Long Arc-Cell Vacuum Chambers of the Taiwan Photon Source	3219
	L.H. Wu, C.K. Chan, C.H. Chang, C.-C. Chang, S.W. Chang, Y.P. Chang, B.Y. Chen, J.-R. Chen, Z.W. Chen, C.M. Cheng, G.-Y. Hsiung, S-N. Hsu, H.P. Hsueh, C.S. Huang, Y.T. Huang, T.Y. Lee, I.C. Yang NSRRC, Hsinchu, Taiwan J.-R. Chen National Tsing Hua University, Hsinchu, Taiwan
	An outgassing analysis during transportation for the large, 14-m-long, ultra-high-vacuum aluminum arc-cell chambers of the Taiwan Photon Source (TPS) was performed using residual gas analysis (RGA). Each cell was baked to 150 °C in the laboratory to achieve ultra-high vacuum. Under pumping by primarily ion pumps (IP) and non-evaporable getter (NEG) pumps, the cells obtained pressures of 6.4×10^-9 Pa on average, and the main residual gas was H2. Here, vacuum pressure measurements and residual gas analyses were performed in situ while a cell chamber was being transported. It was found that the vibration of the arc-cell vacuum chamber caused the pressure to rise abruptly; in this case, the main outgassing gas was CH4. Once the arc cell had been fully installed, the vacuum pressure gradually decreased to the original vacuum pressure because of the pumping effect of the ion gauges.
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WEPHA048	Behavior of Vacuum Pressure in TPS Vacuum System	3222
	I.C. Yang, C.K. Chan, C.-C. Chang, B.Y. Chen, J.-R. Chen, C.M. Cheng, J. -Y. Chuang, G.-Y. Hsiung, C.K. Kuan, C.C. Liang, I.C. Sheng, L.H. Wu NSRRC, Hsinchu, Taiwan
	Taiwan Photon source (TPS) is in its first stage commissioning in 2014-2015. The vacuum systems of TPS were installed for commissioning since August 2014. After four months performance testing and subsystem integration, the commissioning of booster ring began on 12 December and then the first 3 GeV beam was stored on 31 December. 100mA beam current, 35Ah accumulated beam dose was archived in March 2015 before machine shut down. The average pressure in storage ring is 2.8×10^-8 Pa before commissioning, rising to 1.33×10-7 Pa with 100mA beam current. In 35Ah accumulated beam dose, the target of beam cleaning effect has reached to 8.92×10-10 Pa/mA. The vacuum performance, experience and events during commissioning will be presented in this paper.
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WEPWI024	Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source	3540
	M.L. Stutzman, P.A. Adderley, M. Poelker JLab, Newport News, Virginia, USA M.A. Mamun Old Dominion University, Norfolk, Virginia, USA
	Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.
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WEPWI033	Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples	3558
	M. Basovic, S. Popović, M. Tomovic, L. Vušković ODU, Norfolk, Virginia, USA F. Čučkov, A. Samolov University of Massachusetts Boston, Boston, Massachusetts, USA
	Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.
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Paper

Title

Page

Preliminary Design of the High-Luminosity LHC Beam Screen with Shielding

60

C. Garion, V. Baglin, R. Kersevan
CERN, Geneva, Switzerland

A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, they have to shield the cold mass from physics debris coming from the nearby beam collision points. To such purpose, energy absorbers made of tungsten alloy are installed onto the beam screen in the vacuum system. In this contribution, the proposed mechanical design is shown; it covers different thermomechanical aspects such as the behaviour during a magnet quench and the heat transfer from the tungsten absorbers to the cooling tubes. Assembly and manufacturing tolerances are also considered to evaluate the impact on the aperture. Results obtained with a short prototype assembly test are discussed.

Slides MOBD1 [3.089 MB]

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WEPMA003

Vacuum System Design for the Sirius Storage Ring

2744

R.M. Seraphim, O.R. Bagnato, R.O. Ferraz, H.G. Filho, G.R. Gomes, M. Nardin, R.F. Oliveira, B.M. Ramos, A.R.D. Rodrigues, M.B. Silva, T.M. da Rocha
LNLS, Campinas, Brazil

Sirius is a 3 GeV 4th-generation light source under construction by the Brazilian Synchrotron Light Laboratory (LNLS). Sirius will have a low emittance storage ring, 0.28 nm-rad, based on 20 cells of a highly compact lattice – 5-bend achromat (5BA). This lattice concept leaves very little space for components and therefore requires narrow vacuum chambers with tight mechanical tolerances. Most of the storage ring vacuum chambers will be made of OFS copper and have a circular cross section with inner diameter of 24 mm and a wall thickness of 1 mm. The unused synchrotron radiation will be distributed along the water cooled walls of the chambers. Due to the small conductance of the chambers, the vacuum pumping will be based on distributed concept and then non-evaporable getter (NEG) coating will be extensively used, with more than 95% of the chambers being coated. In this paper, we present an overview of the storage ring vacuum system and the main vacuum chambers fabrication developments.

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WEPMA034

Bakeout Concept for the HESR at FAIR

2832

H. Jagdfeld, N. Bongers, P. Chaumet, F.M. Esser, F. Jordan, F. Klehr, G. Langenberg, U. Pabst, L. Semke
FZJ, Jülich, Germany

Forschungszentrum Jülich has taken the leadership of a consortium being responsible for the design of the High-Energy Storage Ring (HESR) going to be part of the FAIR project at GSI. The HESR is designed for antiprotons but can be used for heavy ion experiments as well. Therefore the vacuum is expected to be 10^-11 mbar or better. To achieve this also in the curved sections where 44 bent dipole magnets with a length of around 4.5 m will be installed, NEG coated dipole chambers will be used to reach the needed pumping speed and capacity. For activation of the NEG-material a bakeout system must be installed. The bakeout concept including the layout of the control system and the systematization of the heater packages for all components of the vacuum system are presented. Also the special design of the heater jackets inside the dipole will be shown where the geometrical parameters are very critical and space is very limited. The results of the simulation of temperature distribution in the dipole iron are compared to temperature measurements carried out at a testbench with different layouts of the heater jackets. The final design of the dipole heater jackets will be illustrated.

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WEPMA059

Degassing of Kicker Magnet by In-situ Bake-out Method

2911

J. Kamiya, Y. Hikichi, M. Kinsho, N. Ogiwara
JAEA/J-PARC, Tokai-mura, Japan

New method of in-situ degassing of the kicker magnet in the beam line has been developed. The heater and heat shielding panels are installed in the vacuum chamber in this method. The heater was designed considering the maintainability. The graphite was selected as the heater and the high melting point metals were used as the reflectors just near the heater. The thermal analysis and the temperature measurement with the designed heater was performed. The ideal temperature distribution for the kicker degassing was obtained. The outgassing of the graphite during rising the temperature was measured. The result showed that the outgassing was extremely suppressed by the first heating. This means the outgassing of the graphite heater was negligible as long as it is used in the beam line without exposure to the air.

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WEPMN021

Design and Research of Secondary Electron Emission Test Equipment with Low Electron Energy

2970

Y.H. Xu, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

In particle accelerators, the secondary electrons resulting from the interaction between particles and vacuum chamber have a great impact on beam quality. Especially for positron, proton and heavy ion accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. We have studied the secondary electron emission (SEE) of metal used for accelerators. A secondary electron emission measurement system with low electron energy has been designed and used to measure the SEE yield of metal and non-evaporable getter materials. With the equipment, we have obtained the characteristic of the SEE yield of stainless steel and oxygen free copper (OFC).

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WEPMN022

Optimization Design of Ti Cathode in Ceramic Pipe Film Coating Based on the Simulation Result of CST

2973

J. Wang, L. Fan, Y.Z. Hong, X.T. Pei, Y. Wang, W. Wei, Y.H. Xu, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

The injection chamber at Hefei Light Source II (HLS II) consists of four ceramic vacuum chambers whose inner surface were coated with TiN thin film. The cross section of ceramic pipes is special racetrack structure. In order to improve the uniformity of the film, the structure of the cathode Ti plate needed to be optimized. In this article, CST PARTICLE STUDIOTM software had been used to simulate the influence of different target structure on discharge electric field distribution and electrons trajectories. Furthermore, the reliability of the simulation were analysed compared with the experimental results. Also, we put forward the optimization design of Ti cathode structure which could satisfy the requirement of uniformity of the thin film.

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WEPMN023

Vacuum System of the Storage Ring of HLS-II

2976

Y. Wang, L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, W. Wei, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

HLS storage-ring has been operated for more than twenty-five years. In 2014 we began to upgrade the machine, which is called HLS-II. The emittance is reduced to 40 nmrad, five insertion devices are added and the injection energy increases to 800MeV. Now the machine commissioning has already been completed. The typical life time is 300 mins at 300mA, 800MeV. The average pressure of static and dynamic vacuum are below 2×10^-8 Pa and 1.2×10-7 Pa respectively. The design, installation and commissioning of the vacuum system of the storage ring are detailedly stated in this paper.

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WEPMN028

Preliminary Mechanical Design of Ceramic Pipe Film Coating Equipment at Hefei Light Source II

2988

J. Lu
NPU, Xi'an Shaanxi, People's Republic of China
L. Fan, Y.Z. Hong, X.T. Pei, J. Wang, Y. Wang, W. Wei, Y.H. Xu, B. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

Ceramic vacuum chambers are important components of the injection chamber at Hefei Light Source II (HLS II). The length of each Ceramic vacuum chamber is 350 mm and their inner surface is coated with TiN thin film whose properties are low secondary electron yield (SEY), good electrical conductivity, stability of performance, ability to block hydrogen permeation. Considering that the cross section of Ceramic pipe is racetrack structure, Ti plate was chose as the cathode to improve TiN thin film deposition rate. Meanwhile, the authors designed a motor drive magnetron sputtering film coating equipment to obtain uniform TiN film.

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WEPHA003

Measurement of NEG Coating Performance Variation in the LHC after the First Long Shutdown

3100

V. Bencini, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan, C. Yin Vallgren
CERN, Geneva, Switzerland

During the Long Shutdown 1 (LS1) of the Large Hadron Collider, 90% of the Non-Evaporable Getter (NEG) coated beam pipes in the Long Straight Sections (LSS) were vented to undertake the planned upgrade and consolidation programmes. After each intervention, an additional bake-out and NEG activation were performed to reach the vacuum requirements. An analysis of the coating performance variation after the additional activation cycle has been carried out by using ultimate pressure and pressure build-up measurements. In addition, laboratory measurements have been carried out to mimic the LHC coated beam pipe behaviour. The experimental data have been compared with calculation obtained by Molflow+.

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WEPHA004

Present Quality Assurance for the LHC Beam Vacuum System and its Future Improvement

3103

J. Sestak, V. Baglin, G. Bregliozzi, P. Chiggiato
CERN, Geneva, Switzerland

During the Long Shutdown 1 (LS1), the LHC beam vacuum system was upgraded to minimize dynamic vacuum effects like stimulated desorption and beam-induced electron multipacting. A quality assurance plan was mandatory due to the demanding vacuum performance and the limited access to the equipment during the following operation period. Laboratory assessment tests and underground interventions were performed following well-defined and approved procedures. All vacuum related activities were documented and written reports stored in dedicated databases. Quality controls were performed to find mechanical, cabling and equipment functionality non-conformities. Possible issues were identified, classified and tracked in a non-conformity database for future corrective actions. This contribution give an overview of the quality assurance policy followed during the LS1 and the non-conformities reported after quality control. Possible future improvements are also discussed.

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WEPHA005

Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules

3106

C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.

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WEPHA006

Recommissioning of the COLDEX Experiment at CERN

3109

R. Salemme, V. Baglin, F. Bellorini, G. Bregliozzi, K. Brodzinski, P. Chiggiato, P. Costa Pinto, P. Gomes, A. Gutierrez, V. Inglese, B. Jenninger, R. Kersevan, E. Michel, M. Pezzetti, B. Rio, A. Sapountzis
CERN, Geneva, Switzerland

COLDEX (Cold bore Experiment), installed in the Super Proton Synchrotron (SPS) at CERN, is a test vacuum sector used in 2001-2004 to validate the Large Hadron Collider (LHC) cryogenic vacuum system with LHC type proton beams. Its cryostat houses a 2.2 m long copper perforated beam screen surrounded by a stainless steel cold bore, both individually temperature controlled down to 5 and 3 K, respectively. In the framework of the development for the High Luminosity upgrade of the LHC (HL-LHC), COLDEX has been re-commissioned in 2014. The objective of this re-commissioning is the validation of the performance of amorphous carbon coatings at cryogenic temperature with LHC type beams. The existing COLDEX beam screen has been dismounted and carbon coated, while a complete overhaul of the vacuum, cryogenic and control systems has been carried out. This contribution describes the phases of re-commissioning and reviews the current experimental set-up. An overview of the possible measurements with COLDEX, in view of its HL-LHC experimental program, is also presented.

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WEPHA007

Amorphous Carbon Coatings at Cryogenic Temperatures with LHC Type Beams: First Results with the COLDEX Experiment

3112

R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Extrapolations of electron cloud data from the Large Hadron Collider (LHC) Run 1 to the High Luminosity upgrade (HL-LHC) beam parameters predict an intolerable increase of heat load on the beam screens of the inner triplets. Amorphous carbon (a-C) coating of the beam screen surface is proposed to reduce electron cloud production, thereby minimising its dissipated power. To validate this solution, the COLDEX experiment has been re-commissioned. Such equipment mimics the performance of the LHC cold bore and beam screen cryogenic vacuum system in presence of LHC beams in the Super Proton Synchrotron (SPS). The main objective of the study is the performance evaluation of a-C coatings while operating the beam screen in the 10 to 60 K temperature range and cold bore below 3 K. This paper reviews the status of COLDEX and the results obtained during its first experimental runs.

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WEPHA009

Propagation of Radioactive Contaminants Along the Isolde Beamline

3115

R. Kersevan, M. Ady, A. Dorsival, A. Gottberg, M. Maietta, G. Vandoni
CERN, Geneva, Switzerland

The vacuum system of RIB facilities is entirely hermetical, with storage of effluents and controlled release to atmosphere after a decay time. In Isolde, distributed primary pumping is sectorized in three parts, but all effluents are conveyed together in a unique tank. Thus, highly contaminated gas from the target and front end may be mixed with less contaminated gas from the beam transfer lines. This study aims at analysing and quantifying the distribution and propagation of neutral rare gas radioactive isotopes along the Isolde beam-line by numerical simulation (steady-state and time resolved Test-Particle Monte-Carlo, Molflow+) and experimental means. The time-resolved Monte-Carlo integrates decay time for the propagating species. To measure the distribution of contaminants, sampling filters are installed at the exhaust of the vacuum turbo-molecular pumps. Comparison between simulation and experiment shows excellent agreement, confirming the pertinence of the Monte-Carlo tool to radioactive species propagation. The filtering effect of magnetic sectors, the RFQ Cooler, and Buncher on the propagating neutral isotopes are quantified.

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WEPHA010

The Vacuum System of the Extra-Low Energy Antiproton Decelerator ELENA at CERN

3119

R. Kersevan
CERN, Geneva, Switzerland

The Extra-Low ENergy Antiproton decelerator (ELENA) project is under way since 2011. In the past 3 years, it has considerably evolved into a detailed design for the ring and the transfer lines. It is a small machine, ~30 m in circumference, with a rather tight specification for the average pressure seen by the anti-proton beams injected by the anti-proton decelerator (AD). The average pressure in ELENA must be limited to 4x10^-12 mbar (H2-equivalent) in order to limit the charge-exchange losses during the rather long deceleration process (several tens of seconds), during which the energy of the beam is reduced and the electron-cooler is used twice in order to decrease the transverse emittance of the anti-proton beam. This paper will discuss the design of the chambers of the injection line, extraction line and the ring. It will also mention the actual status of the vacuum system for the transfer lines to the experiments, LNE, which are under finalisation. The results of detailed 3D simulations made with the test-particle montecarlo code Molflow+ will be discussed, alongside with the choice for the pumping system, mainly distributed NEG-coatings and integrated NEG/ion-pumps.

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WEPHA011

Photodesorption and Electron Yield Measurements of Thin Film Coatings for Future Accelerators

3123

R. Kersevan, M. Ady, P. Chiggiato
CERN, Geneva, Switzerland
T. Honda, Y. Tanimoto
KEK, Tsukuba, Japan

The performance of future accelerators could be limited by electron cloud phenomena and high photodesorption yields. For such a reason, the study of secondary electron and photodesorption yields of vacuum materials is essential. The eradication or mitigation of both secondary electron and molecule desorption could strongly reduce the beam scrubbing time and increase the availability of nominal beams for experiments. Surface modifications with the desired characteristics can be achieved by thin-film coatings, in particular made of amorphous carbon and non-evaporable getters (NEG). In the framework of a new collaboration, several vacuum chambers have been produced, and different coatings on each of them have been applied. The samples were then irradiated at KEK’s Photon Factory with SR light of 4 keV critical energy during several days, allowing the measurement of the photodesorption yield as a function of the photon dose. This paper presents the experiment and briefly summarizes the preliminary photodesorption and photoelectron yield data of different coatings. The results can be used for future machine design with similar conditions, such as the FCC-hh.

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WEPHA012

Synchrotron Radiation Distribution and Related Outgassing and Pressure Profiles for the HL-LHC Final Focus Magnets

3127

R. Kersevan
CERN, Geneva, Switzerland

The HL-LHC final focus area, from D2 to the interaction point, has been modelled based on the latest vacuum chamber geometry and orbits. The synchrotron radiation (SR) fans are computed using the Monte Carlo code SYNRAD⁺, in the dipole approximation regime. The angular and energy dependence of the reflectivity of the copper surfaces is considered, as well as the surface roughness. Once the SR distributions are computed, they are converted into outstanding profiles by using data available in literature. The test-particle Monte Carlo code Molflow+ is then used and the related pressure profiles and gas density distribution are computed. This allows an optimization of the pattern of the perforations on the tungsten-shielded beam screen proposed for this area. It is shown that the resultant gas density is below the limit dictated by the ATLAS and CMS detectors.

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WEPHA019

Development and Production of Non-evaporable Getter Coatings for MAX IV

3145

P. Costa Pinto, B. Bártová, B. Holliger, S. Marques Dos Santos, V. Nistor, A. Sapountzis, M. Taborelli, I. Wevers
CERN, Geneva, Switzerland
J. Ahlbäck, E. Al-Dmour, M.J. Grabski, C. Pasquino
MAX-lab, Lund, Sweden

MAX IV is presently under construction at Lund, Sweden, and the first beam for the production of synchrotron radiation is expected to circulate in 2016. The whole set of 3-GeV ring beam pipes is coated with Ti-Zr-V Non Evaporable Getter (NEG) thin film in order to fulfil the average pressure requirement of 1x10^-9 mbar, despite the compact magnet layout and the large aspect ratio of the vacuum chambers. In this work, we present the optimisations of the coating process performed at CERN to coat different geometries and mechanical assembling used for the MAX IV vacuum chambers; the morphology of the thin films is analysed by Scanning Electron Microscopy; the composition and thickness is measured by Energy Dispersive X-ray analysis; the activation of the NEG thin film is monitored by X-ray Photoemission Spectroscopy; the vacuum performance of the coated beam pipes is evaluated by the measurement of hydrogen sticking coefficient. The results of the coating production characterisation for the 84 units coated at CERN are presented.

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WEPHA020

Titanium Coating of Ceramics for Accelerator Applications

3148

W. Vollenberg, P. Costa Pinto, B. Holliger, A. Sapountzis, M. Taborelli
CERN, Geneva, Switzerland

Titanium thin films can be deposited on ceramics, in particular alumina, without adherence problems. Even after air exposure their secondary electron yield is low compared to alumina and can be further reduced by conditioning or beam scrubbing. In addition, depending on the film thickness, titanium provides different surface resistances that fulfil requirements of ceramics in particle accelerators. Titanium thin films (MOhm square range) are used to suppress electron multipacting and evacuate charges from ceramic surfaces. Thicker films (5-25 Ω square range) are applied to lower the surface resistance so that the beam impedance is reduced. In this contribution, we present the results of a development aimed at coating 2-meter long alumina vacuum chambers with a uniform surface resistivity by a dedicated DC magnetron sputtering configuration.

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WEPHA046

Outgassing Analysis During Transport for 14m Long Arc-Cell Vacuum Chambers of the Taiwan Photon Source

3219

L.H. Wu, C.K. Chan, C.H. Chang, C.-C. Chang, S.W. Chang, Y.P. Chang, B.Y. Chen, J.-R. Chen, Z.W. Chen, C.M. Cheng, G.-Y. Hsiung, S-N. Hsu, H.P. Hsueh, C.S. Huang, Y.T. Huang, T.Y. Lee, I.C. Yang
NSRRC, Hsinchu, Taiwan
J.-R. Chen
National Tsing Hua University, Hsinchu, Taiwan

An outgassing analysis during transportation for the large, 14-m-long, ultra-high-vacuum aluminum arc-cell chambers of the Taiwan Photon Source (TPS) was performed using residual gas analysis (RGA). Each cell was baked to 150 °C in the laboratory to achieve ultra-high vacuum. Under pumping by primarily ion pumps (IP) and non-evaporable getter (NEG) pumps, the cells obtained pressures of 6.4×10^-9 Pa on average, and the main residual gas was H2. Here, vacuum pressure measurements and residual gas analyses were performed in situ while a cell chamber was being transported. It was found that the vibration of the arc-cell vacuum chamber caused the pressure to rise abruptly; in this case, the main outgassing gas was CH4. Once the arc cell had been fully installed, the vacuum pressure gradually decreased to the original vacuum pressure because of the pumping effect of the ion gauges.

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WEPHA048

Behavior of Vacuum Pressure in TPS Vacuum System

3222

I.C. Yang, C.K. Chan, C.-C. Chang, B.Y. Chen, J.-R. Chen, C.M. Cheng, J. -Y. Chuang, G.-Y. Hsiung, C.K. Kuan, C.C. Liang, I.C. Sheng, L.H. Wu
NSRRC, Hsinchu, Taiwan

Taiwan Photon source (TPS) is in its first stage commissioning in 2014-2015. The vacuum systems of TPS were installed for commissioning since August 2014. After four months performance testing and subsystem integration, the commissioning of booster ring began on 12 December and then the first 3 GeV beam was stored on 31 December. 100mA beam current, 35Ah accumulated beam dose was archived in March 2015 before machine shut down. The average pressure in storage ring is 2.8×10^-8 Pa before commissioning, rising to 1.33×10-7 Pa with 100mA beam current. In 35Ah accumulated beam dose, the target of beam cleaning effect has reached to 8.92×10-10 Pa/mA. The vacuum performance, experience and events during commissioning will be presented in this paper.

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WEPWI024

Vacuum Characterization and Improvement for the Jefferson Lab Polarized Electron Source

3540

M.L. Stutzman, P.A. Adderley, M. Poelker
JLab, Newport News, Virginia, USA
M.A. Mamun
Old Dominion University, Norfolk, Virginia, USA

Operating the JLab polarized electron source with high reliability and long lifetime requires vacuum near the XHV level (<=1x10^-12 Torr). This paper describes ongoing vacuum research at Jefferson Lab including characterization of outgassing rates for surface coatings and heat treatments, ultimate pressure measurements, investigation of pumping including an XHV cryopump, and characterization of ionization gauges in this pressure regime.

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WEPWI033

Effects of Plasma Processing on Secondary Electron Yield of Niobium Samples

3558

M. Basovic, S. Popović, M. Tomovic, L. Vušković
ODU, Norfolk, Virginia, USA
F. Čučkov, A. Samolov
University of Massachusetts Boston, Boston, Massachusetts, USA

Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is to show the effect of plasma processing on the SEY of Nb. The setup measures the secondary electron energy distribution at various incident angles as measured between the electron beam and the surface of the sample. The goal is to determine the SEY on non-treated and plasma treated surface of electron beam welded samples. Here we describe the experimental setup, plasma treatment device, and fabrication and processing of the Nb samples.

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