07 Accelerator Technology
T14 Vacuum Technology
Paper Title Page
MOZGBE4 Overview of Fabrication Techniques and Lessons Learned with Accelerator Vacuum Windows 51
 
  • C.R. Ader, M.W. McGee, L.E. Nobrega, E.A. Voirin
    Fermilab, Batavia, Illinois, USA
 
  Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
Vacuum thin windows have been used in Fermilab's accelerators for decades and typically have been overlooked in terms of their criticality and fragility. Vacuum windows allow beam to pass through while creating a boundary between vacuum and air or high vacuum and low vacuum areas. The design of vacuum windows, including titanium and beryllium windows, will be discussed as well as fabrication, testing, and operational concerns. Failure of windows will be reviewed as well as safety approaches to mitigating failures and extending the lifetimes of vacuum windows. Various methods of calculating the strengths of vacuum windows will be explored, including FEA.
 
slides icon Slides MOZGBE4 [2.155 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBE4  
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MOZGBE5 Results on the FCC-hh Beam Screen at the KIT Electron Storage Ring KARA 55
 
  • L.A. Gonzalez, V. Baglin, P. Chiggiato, C. Garion, M. Gil Costa, R. Kersevan
    CERN, Geneva, Switzerland
  • I. Bellafont, F. Pérez
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • S. Casalbuoni, E. Huttel
    KIT, Eggenstein-Leopoldshafen, Germany
 
  Funding: * The European Circular Energy-Frontier Collider Study (EuroCirCol) project has received funding from the European Union's Horizon 2020 research and innovation programme under grant No 654305.
In the framework of the EuroCirCol collaboration* (work package 4 "Cryogenic Beam Vacuum System"), the fabrication of 3 FCC-hh beam-screen (BS) prototypes has been carried out with the aim of testing them at room temperature at the Karlsruhe Institute of Technology (KIT) 2.5 GeV electron storage ring KARA (KArlsruhe Research Accelerator). The 3 BS prototypes will be tested on a beamline installed by the collaboration, named as BEam Screen TEstbench EXperiment (BESTEX). KARA has been chosen because its synchrotron radiation (SR) spectrum, photon flux and power, match the one foreseen for the 50+50 TeV FCC-hh proton collider. Each of the 3 BS prototypes, 2 m in length, implement a different design feature: 1) baseline design (BD), with electro-deposited copper and no electron-cloud (EC) mitigation features; 2) BD with set of distributed cold-sprayed anti-EC clearing electrodes; 3) BD with laser-ablated anti-EC surface texturing. We present here the results obtained so far at BESTEX and the comparison with extensive montecarlo simulations of the expected outgassing behavior under synchrotron radiation.
The information herein only reflects the views of its authors and the European Commission is not responsible for any use that may be made of the information.
 
slides icon Slides MOZGBE5 [4.318 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOZGBE5  
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TUZGBE3 Towards Implementation of Laser Engineered Surface Structures for Electron Cloud Mitigation 1220
 
  • M. Sitko, V. Baglin, S. Calatroni, P. Chiggiato, B. Di Girolamo, E. Garcia-Tabares Valdivieso, M. Taborelli
    CERN, Geneva, Switzerland
  • A. Abdolvand, D. Bajek, S. Wackerow
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • M. Colling, T.J. Jones, P.A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  The LHC operation has proven that the electron cloud could be a significant limiting factor in machine performance, in particular for future High Luminosity LHC (HL-LHC) beams. Electron clouds, generated by electron multipacting in the beam pipes, leads to beam instabilities and beam-induced heat load in cryogenic systems. Laser Engineered Surface Structures (LESS) is a novel surface treatment which changes the morphology of the internal surfaces of vacuum chambers. The surface modification results in a reduced secondary electron yield (SEY) and, consequently, in the eradication of the electron multipacting. Low SEY values of the treated surfaces and flexibility in choosing the laser parameters make LESS a promising treatment for future accelerators. LESS can be applied both in new and existing accelerators owing to the possibility of automated in-situ treatment. This approach has been developed and optimised for the LHC beam screens in which the electron cloud has to be mitigated before the HL-LHC upgrade. We will present the latest steps towards the implementation of LESS.  
slides icon Slides TUZGBE3 [1.825 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBE3  
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WEPMF032 Experimental Studies on Secondary Electron Emission Characteristics for Chamber Materials of Accelerators 2425
 
  • Y. Jiao, Z. Duan, W.B. Liu, Y.D. Liu
    IHEP, Beijing, People's Republic of China
  • Liu. S. Liu
    Institute of High Energy Physics (IHEP), People's Republic of China
  • P.C. Wang
    DNSC, Dongguan, People's Republic of China
 
  Funding: National Natural Science Foundation of China (11275221) and Key Laboratory Foundation of Particle Acceleration Physics &Technology (Y5294106TD)
Secondary electron emission (SEE) of surface is origin of multipacting effect which could seriously deteriorate beam quality and even perturb the normal operation of particle accelerators. Experimental measurements on secondary electron yield (SEY) on different materials and coating have been developed in many accelerator laboratory. In fact, the SEY is just one parameter of secondary electron emission characteristics which include spatial and energy distribution of emitted electrons. A novel experimental apparatus was set up in China Spallation Neutron Source (CSNS) and innovative measurement methods were applied to obtain the whole characteristics of SEE. With some traditional accelerator chamber materials such as Cu, Al, TiN, SEY dependence on primary electron energy and beam injection angle, spatial and energy distribution of emitted secondary electrons were achieved with this measurement apparatus. This contribution also tries to give all the experimental results a reasonable theoretical analysis.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF032  
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WEPMF055 The REGAE Accelerator Vacuum System 2493
 
  • S. Lederer, K. Flöttmann, L. Lilje, N. Plambeck
    DESY, Hamburg, Germany
 
  Since 2011 the Relativistic Electron Gun for Atomic Exploration (REGAE) is operated at DESY in Hamburg. The accelerator consists mainly of a high gradient S-band RF-gun, which generates ultra-low emittance electron bunches, and an S-band RF-buncher cavity for bunch compression. In this contribution we describe the vacuum system of the REGAE accelerator. We will cover design aspects, applied cleaning and installation procedures as well as operation experience over the last years.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF055  
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WEPMF057 PETRA III Vacuum System - Experiences from the First Decade of Operation 2499
 
  • L. Lilje, R. Bospflug, N. Plambeck
    DESY, Hamburg, Germany
 
  In 2008 the construction of the PETRA III vacuum system started. A year later the first photons were delivered to initial experiments and in 2010 the user operation started. In this paper the operation of the vacuum system will be reviewed. Some of the lessons learned in the initial phase will be presented as well as the main upgrades since then. By now the vacuum system has shown a very high reliability and shows no significant impact on the availability of the machine.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF057  
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WEPMF087 LHC Injectors Upgrade Project: Outlook of the Modifications to the Super Proton Synchrotron (SPS) Vacuum System and Impact on the Operation of the Carbon-Coated Vacuum Chambers 2589
 
  • C. Pasquino, G. Bregliozzi, P. Chiggiato, P. Cruikshank, A. Farricker, A. Harrison, J. Perez Espinos, J.A.F. Somoza, M. Taborelli, C. Vollinger
    CERN, Geneva, Switzerland
 
  Aiming at doubling the beam intensity and reducing the beam emittance, significant modifications of the LHC and its injector chain will take place during Long Shutdown 2 (LS2), starting from 2019. The LIU project (LHC Injector Upgrade), in the specific, touches Linac4, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS) as well as the heavy ion chain. During LS2, important changes will take place mainly in the Long Straight Sections of the SPS to host a newly conceived dumping system, upgraded RF cavities and upgraded extraction channels. Additionally, the vacuum chambers of the main bending and focusing magnets as well as vacuum drifts will be coated with amorphous carbon in order to reduce the dynamic pressure effects induced by multipacting. The modifications to the different vacuum sectors will be described in details as well as the impact on operation of amorphous carbon coated sectors that have been already deposited.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF087  
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WEPMF090 Upgrade of the CMS Experimental Beam Vacuum During LS2 2596
 
  • J.S. Sestak, G. Bregliozzi, P. Chiggiato, C. Di Paolo
    CERN, Geneva, Switzerland
 
  Starting from December 2018, the Large Hadron Collider (LHC) is going to interrupt its physic operations for more than two years within the period called second long shutdown (LS2). The Compact Muon Solenoid (CMS) experiment will undergo the biggest upgrade of its experimental beam vacuum system since the first operations in 2008. The new experimental vacuum layout should comply with demanding structural, vacuum, integration and physics requirements. Moreover, the new layout should be compatible with foreseen engineering changes of the detector and the machine during the upgrade phase of High-Luminosity LHC in LS3. This paper gives an overview of the CMS LS2 experimental vacuum sectors upgrades. Both design and production phase of the new vacuum layout is discussed in detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMF090  
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WEPMG005 First Beam Test of Laser Engineered Surface Structures (LESS) at Cryogenic Temperature in CERN SPS Accelerator 2616
 
  • R. Salemme, V. Baglin, S. Calatroni, P. Chiggiato, B. Di Girolamo, E. Garcia-Tabares Valdivieso, B. Jenninger, L. Prever-Loiri, M. Sitko
    CERN, Geneva, Switzerland
  • A. Abdolvand, S. Wackerow
    University of Dundee, Nethergate, Dundee, Scotland, United Kingdom
  • R. Salemme
    ITER Organization, St. Paul lez Durance, France
 
  Electron cloud mitigation is an essential requirement for accelerators of positive particles with high intensity beams to guarantee beam stability and limited heat load in cryogenic systems. Laser Engineered Surface Structures (LESS) are being considered, within the High Luminosity upgrade of the LHC collider at CERN (HL-LHC), as an option to reduce the Secondary Electron Yield (SEY) of the surfaces facing the beam, thus suppressing the elec-tron cloud phenomenon. As part of this study, a 2.2 m long Beam Screen (BS) with LESS has been tested at cryogenic temperature in the COLD bore EXperiment (COLDEX) facility in the SPS accelerator at CERN. In this paper, we describe the manufacturing procedure of the beam screen, the employed laser treatment technique and discuss our first observations in COLDEX confirming electron cloud suppression.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPMG005  
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WEPML028 NEG Coated Vacuum Chambers and Bake-Out-Concept for the HESR at FAIR 2745
 
  • H. Jagdfeld, N.B. Bongers, J. Böker, P. Chaumet, F.M. Esser, F. Jordan, F. Klehr, G. Langenberg, D. Prasuhn, L. Semke, R. Tölle
    FZJ, Jülich, Germany
  • A. Mauel, G. Natour, U. Pabst
    Forschungszentrum Jülich GmbH, Central Institute of Engineering, Electronics and Analytics, Jülich, Germany
 
  The High-Energy Storage Ring (HESR) is part of the international Facility for Antiproton and Ion Research (FAIR) at GSI Darmstadt. Forschungszentrum Jülich (IKP and ZEA-1) is responsible for the design and installation of the HESR. The HESR is designed for antiprotons and heavy ion experiments as well. Therefore the vacuum is required to be 10-11 mbar or better. To achieve this extreme high vacuum (XHV), NEG coated chambers will be used in combination with common vacuum pumps to reach the needed pumping speed and capacity everywhere in the accelerator ring. For activation of the NEG material a bake-out system will be developed and installed. A bake-out test bench was used for checking the achievable end pressure and developing the bake-out system for the NEG coated chambers of the HESR. The results of the tests and the bake-out concept including the layout of the control system are presented. In addition, the temperature distribution of the dedicated heater jackets inside the dipole and quadrupole magnets are shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML028  
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WEPML029 Vacuum System of the HESR at FAIR, Status of Tests, Layout and Manufacturing 2748
 
  • F.M. Esser, N.B. Bongers, J. Böker, P. Chaumet, R. Gebel, R. Greven, S. Hamzic, H. Jagdfeld, F. Klehr, B. Laatsch, G. Langenberg, D. Marschall, A. Mauel, G. Natour, D. Prasuhn, L. Reifferscheidt, M. Schmitt, L. Semke, R. Tölle
    FZJ, Jülich, Germany
 
  The Research Center Jülich is leading a consortium being responsible for the design and manufacturing of the High-Energy Storage Ring (HESR) which is part of the FAIR project in Darmstadt, Germany. The HESR is designed for antiprotons within a momentum range of 1.5-15 GeV/c but can also be used for heavy ion experiments. Therefore the vacuum quality is expected to be 10-11 mbar or better which is a great challenge on the overall vacuum layout as well as on the surface quality of the chambers and beam tubes. Whereas all bent dipole chambers are installed, the manufacturing of the pumping bodies with integrated RF meshes as well as several diagnostic chambers are in the focus of investigation. To validate the intended pumping concept of both the bake-out arc sections and the non-bakable straight sections, final tests at the operational test benches are planned. In parallel, the purchasing of valves and first pumps will be prepared. The actual layout of the HESR vacuum system and its components will be presented as well as the progress of manufacturing of several vacuum chambers. The latest experimental test results will be presented also.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML029  
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WEPML057 First Commissioning of Vacuum System of Positron Damping Ring for SuperKEKB 2826
 
  • K. Shibata, H. Hisamatsu, T. Ishibashi, K. Kanazawa, M. Shirai, Y. Suetsugu, S. Terui
    KEK, Ibaraki, Japan
 
  To satisfy the requirements of high beam quality for positron injection into the SuperKEKB main ring, a new damping ring (DR) is constructed in an upgraded injector system. The DR is a racetrack-shaped storage ring with a circumference of 135.5 m, in which the 1.1 GeV positron beam is stored for 40 ms to damp the emittance. The maximum stored beam current is 70.8 mA. Required beam lifetime due to residual gas scattering is longer than 1000 s and the average pressure should be lower than 10-5 Pa. Non-evaporable getter (NEG) pumps are mainly used, and the average effective pumping speed for CO is expected to be 0.013 m3s−1m-1 immediately after NEG activation. The beam pipes are made of aluminum alloy, and have antechambers to deal with synchrotron radiation (critical energy 0.8-0.9 keV, total power 7.2 kW) in arc sections, which are effective in reducing the electron cloud and the impedance of the beam pipes. As additional countermeasures against the electron cloud effect, TiN coating and grooved surfacing are also adopted. The commissioning of the DR will commence at the beginning of 2018. The status of the vacuum system of the DR during the first commissioning will be reported.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML057  
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WEPML058 Observation of Pressure Bursts in the SuperKEKB Positron Ring 2830
 
  • S. Terui, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, Y. Suetsugu
    KEK, Ibaraki, Japan
 
  The SuperKEKB is an electron-positron collider with asymmetric energies in KEK aiming an extremely high luminosity of 8x1035 cm-2 s-1 using a nano-beam scheme. In the Phase 1 commissioning from February to June, 2016, the vacuum system of the main ring worked well as a whole at stored beam currents of approximately 1 A. However, the localized pressure bursts accompanied by beam losses were observed in the positron ring. The beam loss monitors triggered beam aborts, and the phenomena has became an obstacle to the beam commissioning. These pressure bursts were frequently observed from the early stage of the commissioning. Most of the pressure bursts occurred near or inside of aluminum-alloy beam pipes in dipole magnets, which have grooved surface at the top and bottom sides. The various observations indicates that the most probable cause of this phenomenon was the collision between the dusts dropped from the grooves and the circulating positron beam. We report the properties and the probable causes of the pressure bursts, and the possible mitigation methods. Some results of the countermeasures taken prior to the ongoing Phase-2 commissioning will be also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML058  
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WEPML059 Status of the SuperKEKB Vacuum System in the Phase-2 Commissioning 2833
 
  • Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui
    KEK, Ibaraki, Japan
 
  The SuperKEKB is an electron-positron collider with asymmetric energies in KEK aiming an extremely high luminosity of 8.0·1035 /cm2/s. In the Phase-1 commissioning from February to June, 2016, the vacuum system of the main ring worked well as a whole at stored beam currents of approximately 1 A. However, several problems were found for the future commissioning, and various countermeasures were taken against these problems during the shutdown period before starting the Phase-2 commissioning. For example, permanent magnets were placed around the beam pipe to suppress the electron cloud effect in the positron ring. Other than these works, new beam pipes for the collision point, the super-conducting final focusing magnets and the positron beam injection region were installed in the main ring. Additional six beam collimators were installed for reducing background noise of the particle detector. Furthermore, the vacuum system for new damping ring for the positron beam was constructed. Reported here will be the present status of the vacuum system of the main ring, and major results of the countermeasures taken prior to the Phase-2 commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML059  
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WEPML072 Gas Permeability Measurement of Graphene Films 2856
 
  • P.C. Wang, X. Sun
    DNSC, Dongguan, People's Republic of China
  • Liu. S. Liu
    Institute of High Energy Physics (IHEP), People's Republic of China
  • C. Meng, H. Wang, D.H. Zhu
    IHEP, Beijing, People's Republic of China
 
  Graphene has extremely high strength and thermal conductivity, which can possibly be used for high-power beam window in accelerator. In this paper, gas permeabilities of different graphene films have been measured by the permeation measurement facility. According to the results, the possibility of the graphene-made beam windows will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML072  
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THPAL056 Vibration Measurements in the TPS Vacuum System 3772
 
  • Y.C. Yang, C.K. Chan, C.-C. Chang, C.S. Chen, J. -Y. Chuang, Y.M. Hsiao, C.C. Liang, Y.Z. Lin
    NSRRC, Hsinchu, Taiwan
 
  The Taiwan Photon Source (TPS) is currently operated in top-up mode for users. In order to improve the stability of the synchrotron light source, vibrations related to the vacuum system have been investigated and improved by turning off pumping systems and reducing the flow rate in chamber cooling water circuits. In this paper, vibrations in different vacuum chambers with normal cooling water condition were investigated, their sources were recorded and clarified and properties of different materials for water tubes were also compared.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL056  
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THPAL057 Development of the Aluminum Beam Duct for the Ultra-Low Emittance Light Source 3775
 
  • G.-Y. Hsiung, J.-R. Chen, C.M. Cheng, S-N. Hsu, H.P. Hsueh, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
  • J.-R. Chen
    National Tsing Hua University, Hsinchu, Taiwan
 
  The future light source with ultra-low emittance, typically < 500 pm rad, requests the beam duct with inner aperture < 20 mm for the electron storage ring. Besides, the cross section of the beam duct must be kept smooth for lowering the impedance. The aluminum extruded beam duct of 10 mm inside and 1 ~ 2 m in length was developed for this purpose. The beam duct was machined in ethanol to obtain a clean surface for a lower thermal outgassing rate. To mitigate the impedance of the flange connection, a special designed diamond-edge gasket and the aluminum flange without knife edge were developed. The inner diameters of both flange and gasket, 10 mm, are the same as that of beam duct. The sealing of the gasket has been proved leak-tight. The ultimate pressure and the thermal outgassing rate of the beam duct has achieved < 2.0·10-10 Torr and < 1.4·10-13 Torr l/(s cm2), respectively after baking. Those results fulfill both the ultrahigh vacuum and lowest impedance are applicable for the next generation ultra-low emittance light source.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL057  
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THPAL058 Effect of Ozonated Water Cleaning on Photon Stimulated Desorption in a Stainless Steel Chamber 3778
 
  • C.M. Cheng, C.K. Chan, C.-C. Chang, Y.T. Cheng, J. -Y. Chuang, G.-Y. Hsiung, L.H. Wu, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
 
  Aluminium vacuum chambers cleaned with ozonated water show a reduction of residual carbon and lower surface outgassing rate after baking. We would like to investigate if stainless steel chambers show similar ef-fects. A stainless steel test chamber was cleaned by stand-ard chemical cleaning only and then compared with an-other one after immersion in 30ppm ozonated water for thirty minutes. Both samples were baked, then photon exposed and the photon desorption yields were deter-mined by vacuum gauges and residual gas analysers at the TLS 19B beamline. The test results on photon stimulated desorption yields and partial pressure variations with and without ozonated water cleaning of the stainless steel tubes will be discussed in some detail.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL058  
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THPAL059 TEMPERATURE ISSUES OF THE TPS BPMS 3781
 
  • Y.T. Huang, C.-C. Chang, C.M. Cheng, P.J. Chou, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
 
  Since the TPS is capable to operate at higher currents, long-term 400mA conditioning runs were conducted. Current-dependent temperature data of BPMs were collected and analysed for both, aluminium and stainless steel BPM chambers. To better understand beam coupling effects in different types of TPS BPMs, electromagnetic and thermal simulation models were established. In this paper, we discuss associated results of such studies.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL059  
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THPAL069 Simulation of a 10 mm Diameter Cascaded Plasma Window 3812
 
  • P.P. Gan, S. Huang, Y.R. Lu, S.Z. Wang, K. Zhu
    PKU, Beijing, People's Republic of China
 
  As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL069  
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THPAL076 Experimental Methods for the Assessment of NEG Pumps Working in Dust-Sensitive Environments 3828
 
  • T. Porcelli, E. Maccallini, P. Manini, M. Mura, M.F. Urbano
    SAES Getters S.p.A., Lainate, Italy
 
  NEG pumps have been widely adopted by many accelerator facilities since decades. However, their use in dust-sensitive areas - such as superconductive radio frequency (SRF) cavities - has always been limited by concerns about accidental dust emission, which could induce detrimental field emission. As future machines will necessarily rely on highly-efficient SRF cavities, able to supply very high accelerating gradients, requirements in terms of particle release from vacuum components (e.g., pumps and valves) are becoming more and more stringent. At the same time, achieving stable ultra-high vacuum conditions is crucial, as condensed residual gas might also be a potential source of field emission. At present, a unified standard procedure to assess dust generation and propagation along a machine is still missing and discussions are ongoing in the vacuum community. Recent experimental measurements demonstrated the compatibility of sintered NEG pumps with ultra-clean environments, due to their intrinsic very low dust release. In parallel, in-situ tests performed at different accelerator facilities showed absence of dust contamination from NEGs and no impact on cavities efficiency.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL076  
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THPAL092 Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples 3862
 
  • O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • Sirvinskaite, R. Sirvinskaite
    Loughborough University, Loughborough, Leicestershire, United Kingdom
 
  The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL092  
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THPAL098 Pumping Properties of Single Metal Zirconium Non-Evaporable Getter Coating 3869
 
  • Sirvinskaite, R. Sirvinskaite, M.D. Cropper, M.D. Cropper
    Loughborough University, Loughborough, Leicestershire, United Kingdom
  • A.N. Hannah, O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
 
  Non-evaporable getter (NEG) coating has been used for years in many particle accelerator facilities due to its evenly distributed pumping speed, low thermal outgassing, and low photon and electron stimulated desorption yields. We have previously demonstrated that quaternary Ti-Zr-Hf-V coating deposited from an alloy wire has the lowest desorption yields, the highest sticking probability and sorption capacity. In this work, we explore the single element targets which are widely available and can be produced in a form of a wire that is easy to apply for a uniform coating of various shapes of vacuum chamber. Single metal Zr coatings have been tested to find a more efficient and cheaper way of producing the NEG-coated vacuum chambers. Two samples coated with Zr of dense and columnar structure were analysed and results of the pumping properties are reported. The results show that pure Zr coating could be an economic solution, despite not being as effective as can be achieved with quaternary NEG film. It shows that columnar Zr coating can be activated and reaches full pumping capacity at 160°C. This is close to the activation temperature of Ti-Zr-Hf-V and lower than that for the widely used ternary Ti-Zr-V alloy.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL098  
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THPAL106 Heating Unit Controller at NSRC SOLARIS 3885
 
  • W.T. Kitka, P. Bulira, P. Czernecki, M.K. Fa'owski, K. Kubal, P. Kurdziel, A.M. Marendziak, M.P. Nowak, M. Ostoja-Gajewski, M. Rozwadowski, K. Wawrzyniak, Z. Zbylut
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
 
  Solaris is a third generation light source constructed at the Jagiellonian University in Kraków, Poland. The machine was designed by the MAX IV Laboratory team. Commissioning of the machine was accomplished at 2016 April and now synchrotron operate in decay mode. Two beamlines PEEM/XAS and UARPES were installed and now are being commissioned. Three more PHELIX, XMCD and diagnostic beamline have received funding and it will be installed and commissioned in range of next few years. The SOLARIS Heating Unit Controller (HUC) was designed to perform bake-out process of new installed vacuum systems. It will allow to perform activation process of undulator vacuum chamber inner coated with NEG layer and also activation process of NEG strips installed in dipole vacuum chambers. HUC is able to control independently up to six 2 kW temperature channels and two current channels. System was built based on Allen-Bradley PLC and Tango Controls. Easy access to the device is provided by the GUI design based on Taurus framework.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL106  
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THPAL107 Three Years of Operational Experience With the Solaris Vacuum System 3888
 
  • A.M. Marendziak, M. Rozwadowski, T. Sobol, M.J. Stankiewicz, A.I. Wawrzyniak
    Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
 
  Solaris, a 1.5 GeV third generation synchrotron light source, was commissioned in 2016 April and is currently operated in decay mode. Two beamlines PEEM/XAS and UARPES were installed and now are being commis-sioned. Three more PHELIX, XMCD and diagnostic beamlines have received funding and will be installed and commissioned in next few years. With total accumu-lated beam dose near to 690 A.h and three orders of mag-nitude reduction of outgassing the design goal of 500 mA beam current and electron energy of 1.5 GeV has been achieved. As the beam current was increased, a few vacu-um problems were encountered, including vacuum leaks in RF and arc sectors and unexpected pressure bursts near photon absorbers. Lessons learned and operational expe-rience will be presented and discussed in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL107  
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THPAL133 LASE Surfaces for Mitigation of Electron Cloud in Accelerators 3958
SUSPL084   use link to see paper's listing under its alternate paper code  
 
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • O.B. Malyshev, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  Vacuum chamber surface characteristics such as the photon and secondary electron yields (PEY and SEY) are critical parameters in the formation of an electron cloud, a serious problem that limits the performance of proton and positron accelerators. A few years ago it was discovered by the Vacuum Solutions Group at Daresbury laboratory that Laser Ablation Surface Engineering (LASE) could provide surfaces with SEY<1 [1,2]. The LASE surfaces are considered as a baseline solution for electron cloud miti-gation in the Future Circular Collider (FCC). However, these surfaces are undergoing further optimisation for the FCC application. While keeping SEY<1 the surfaces should meet the following criteria: Low outgassing, Low particulate generation and low surface resistance. In this paper we will report a number of new surfaces created using the LASE technique with different laser parameters (wavelength, scan speed, pitch, repetition rate, power, and pulse length) and their effect on the SEY, surface re-sistance and vacuum properties, etc  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL133  
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THPMK125 Development of Non-Evaporable Getter (NEG) Coatings on Small Diameter Vacuum Chambers for Diffraction-Limited Storage Ring 4611
 
  • S. Wang, Y.Z. Hong, R. Huang, X.T. Pei, Y. Wang, W. Wei, B. Zhang, S.C. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Design of the fourth generation Diffraction-Limited Storage Ring reduces aperture of vacuum chambers to a few centimeters. To satisfy the small aperture, the intense photon bombardment and the requirement of low pressure, most of the beam pipes need to be deposited with Ti-Zr-V nonevaporable getter (NEG) thin films. NEG can provide distributed pumping and low gas desorption and allow to achieve low pressure in narrow and conductance limited chambers. In this paper, Ti-Zr-V thin film was deposited by DC magnetron sputtering using Ti-Zr-V alloy target. The morphology and thickness of Ti-Zr-V are characterized by Scanning Electron Microscopy (SEM). The average grain size is evaluated using X-ray diffraction (XRD). The composition and the corresponding chemical bonding of the thin film are analyzed by X-ray Photoelectron Spectroscopy (XPS). Finally, the adhesion between the film and substrate and the vacuum performance are evaluated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK125  
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THPML128 Production and Secondary Electron Yield Test of Amorphous Carbon Thin Film 4980
 
  • Y.X. Zhang, X.Q. Ge, S.W. Wang, Y. Wang, W. Wei, B. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Amorphous carbon (a-C) thin film applied to vacuum chambers of high-energy particle accelerators can decrease secondary electron yield(SEY)and suppress electron-cloud effectively. A dc magnetron sputtering apparatus to obtain a-C film has been designed. With the equipment, a-C thin film can be deposited on the inner face of stainless steel pipes ultimately which is uniform and high-quality. Meanwhile, it is found that a-C has a low SEY<1.2 measured by the secondary electron emission measurement set-up in the National Synchrotron Radiation Laboratory. The result indicates that a-C is an ideal material for modern accelerators.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML128  
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THPML129 Deposition and Characterization of TiZrHfV films by DC Magnetron Sputtering 4983
 
  • X.Q. Ge, T.L. He, X.T. Pei, Y.G. Wang, Y. Wang, W. Wei, B. Zhang, Y.X. Zhang
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  The new generation of accelerators places higher demands on the surfaces of vacuum chamber materials. Search for low secondary electron yield (SEY) materials and an effective vacuum chamber surface treatment process, which can effectively reduce the electronic cloud effect, are important early works for the new generation of accelerators. In this work, we revealed the SEY characteristics of Ti-Zr-Hf-V NEG films and Ti-Zr-V NEG films which were deposited on Si (111) substrates using direct current magnetron sputtering method. The surface morphology and surface chemical bonding information were collected by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). With the same parameters, the maximum SEY of Ti-Zr-Hf-V NEG films and Ti-Zr-V NEG films are 1.24 and 1.51, respectively. These results are of great significance for the next-generation particle accelerators.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML129  
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