MC7: Accelerator Technology
T14 Vacuum Technology
Paper Title Page
TUPMP003 Development of Remote Handleable Axially Decoupled Radiation Resistant Vacuum Seal 1233
 
  • R.R. Nagimov, Y. Bylinskii, L. Egoriti, A. Gottberg, G.W. Hodgson, A.N. Koveshnikov, D. Yosifov
    TRIUMF, Vancouver, Canada
 
  Funding: ARIEL is funded by the Canada Foundation for Innovation (CFI), the Provinces of AB, BC, MA, ON, QC, and TRIUMF. TRIUMF receives federal funding via a contribution agreement with the NRC of Canada.
Advanced Rare IsotopE Laboratory (ARIEL) facility is a major expansion of TRIUMF’s rare isotope research program. Aiming to triple the production of rare isotopes, ARIEL facility includes the new electron linac driver and two target stations for electron and proton beams. Particularities of ARIEL target stations design define the requirements for vacuum interfaces with both primary electron and proton beamlines and rare-isotope beamlines. None of the existing products fully met the requirements, driving the development of custom vacuum interfaces. The design of new vacuum seals is driven both by unique design specifications (limited amount of allowed axial forces, extreme radiation resistance, remote handleability and high repeatability) as well as limitations of the proposed design of beamline infrastructure in the target hall (limited available space and the choice of materials for certain components). This paper discusses preliminary results of the vacuum seal development and presents first results of prototype testing.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP003  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP004 Dynamic Pressure in the LHC - Influence of Ions Induced by Ionization of Residual Gas by Both the Proton Beam and the Electron Cloud 1236
SUSPFO006   use link to see paper's listing under its alternate paper code  
 
  • S. Bilgen, C. Bruni, B. Mercier, G. Sattonnay
    LAL, Orsay, France
  • V. Baglin
    CERN, Geneva, Switzerland
 
  Funding: work supported by FCC project (CERN & LAL-CNRS-IN2P3)
Ultra-High Vacuum is an essential requirement to reach design performances in high-energy particle colliders. For the future HL-LHC or FCC study, the understanding of the beam interactions with the vacuum chamber is fundamental to provide solutions to mitigate the pressure rises induced by electronic, photonic and ionic molecular desorption. Studies were performed on the ions, produced by molecular ionization generated by the proton beam and the electron cloud, and stimulating molecular desorption by the surface bombardment. In-situ measurements were carried out, on the LHC Vacuum Pilot Sector (VPS)*, to monitor the dynamic pressure, and to collect the electrical signals due to the electron cloud and to the ions interacting with the vacuum chamber walls. Experimental measurements of electrical signals recorded by copper electrodes were compared to calculations taking into account both the Secondary Electron Yield of copper and electron energy distribution. Finally, it seems that copper electrodes were not fully conditioned and an ion current could be estimated.
* THE LHC VACUUM PILOT-SECTOR PROJECT
B. Henrist, V. Baglin, G. Bregliozzi, and P. Chiggiato, CERN, Geneva, Switzerland
Proceedings of IPAC2014, Dresden, Germany.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP004  
About • paper received ※ 01 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP007 DYVACS (DYnamic VACuum Simulation) Code: Calculation of Gas Density Profiles in Presence of Electron Cloud 1244
 
  • G. Sattonnay, S. Bilgen, B. Mercier
    LAL, Orsay, France
  • V. Baglin
    CERN, Meyrin, Switzerland
 
  The computation of residual gas density profiles in particle accelerators is an essential task to optimize beam pipes and vacuum system design. In a hadron collider such as the LHC, the beam induces dynamic effects due to ion, electron and photon-stimulated gas desorption. The well-known VASCO* code developed at CERN in 2004 (and then PyVASCO**) is already used to estimate vacuum stability and density profiles in steady state conditions. Nevertheless, some phenomena are not taken into account such as the ionization of residual gas by the electron clouds. Therefore, we propose an upgrade of this code by introducing electron cloud maps*** to estimate the electron density and the ionization of gas by electrons, leading to an increase of both electron- and ion-induced desorption. Results obtained with the new code (called DYVACS for DYnamic VACuum Simulation) will be compared to pressure measurements in the VPS sector**** of the LHC.
* A. Rossi, Tech. Rep., LHC Proj. Note 341
** I. Aichinger, et al arXiv:1707.07525
*** T. Demma et al Phys. Rev. Acceler. and Beams 10, 114401 (2007)
**** B. Henrist et al, Proc. IPAC2014, Dresden
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP007  
About • paper received ※ 15 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP013 New Design of Vacuum Chambers for Radiation Shield Installation at Beam Injection Area of J-PARC RCS 1255
 
  • J. Kamiya, K. Kotoku, Y. Shobuda, T. Takayanagi, K. Yamamoto, T. Yanagibashi
    JAEA/J-PARC, Tokai-mura, Japan
  • K. Horino, N. Miki
    Nippon Advanced Technology Co., Ltd., Tokai, Japan
 
  One of the issues in the J-PARC 3 GeV rapid cycling synchrotron is the high residual radiation dose around the beam injection point. A radiation shield is necessary to reduce radiation exposure of workers when maintenance is performed there. A space to install the radiation shield should be secured by newly designing a structure of the vacuum chamber at the injection point and the alumina ceramics beam pipes for the shift bump magnets. To make the space for the shield, the chamber is lengthened along the beam line and the cross-sectional shape is changed from circle to rectangle. The displacement and inner stress of the vacuum chamber due to atmospheric pressure was evaluated to be enough small by the calculation. For the ceramics beam pipe’s rf-shield, the damping resistor was effective to reduce the induced modulation voltages by the pulsed magnetic field.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP013  
About • paper received ※ 29 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP018 Feasibility Tests of a Vacuum System for SPring-8-II 1272
 
  • K. Tamura, T. Bizen, M. Masaki, H. Ohkuma, M. Oishi, M. Shoji, S. Takahashi, Y. Taniuchi
    JASRI, Hyogo, Japan
  • T. Bizen, M. Oishi, S. Takahashi
    RIKEN SPring-8 Center, Hyogo, Japan
 
  For SPring-8-II, the major upgrade of SPring-8, a test half-cell including permanent/electro magnets and a vacuum system was constructed, and hardware feasibility tests have been performed since 2017. Features of the SPring-8-II vacuum system are 1) introduction of the concept of a stainless steel 12 m-long integral chamber (LIC) with a welded structure, and 2) adoption of ex-situ baking of the chamber. The 12 m LIC with a narrow aperture, flangeless structure and a minimum number of bellows was designed so that the vacuum system could be installed without interference with the magnets of a narrow bore diameter aligned on girders with a severe packing factor. For replacement of the existing system with a new one in a short black-out period, the 12 m LIC is planned to be moved into the accelerator tunnel with keeping ultra-high vacuum (UHV) by closing thin gate valves at both ends, after evacuation to UHV by ex-situ baking and NEG activation. This presentation will overview the vacuum system, mainly the 12 m LIC, developed for the test half-cell, and describe the vacuum performance and the result of the assembly test conducted with the permanent/electro magnets.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP018  
About • paper received ※ 15 May 2019       paper accepted ※ 17 May 2019       issue date ※ 21 June 2019  
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TUPMP019 Vacuum Performance of the NEG-coated Chamber for U#19 at PF-ring 1276
 
  • Y. Tanimoto, T. Honda, X.J. Jin, T. Nogami, R. Takai, M. Yamamoto
    KEK, Ibaraki, Japan
 
  At the Photon Factory storage ring (PF-ring) in KEK, a new APPLE-II type elliptically polarizing undulator (U#19) was installed in October 2018. The U#19 vacuum chamber is 4.1 meters in length, and the beam channel with a 15x90 elliptical profile and two cooling-water channels alongside were formed by extrusion of A6060-T6 aluminum alloy. The inner surface of the beam channel is coated with a Ti-Zr-V Non-Evaporable Getter (NEG) thin film, as it has a high effective pumping speed and a low Photon Stimulated Desorption (PSD) yield. After the installation of the U#19, the neighboring uncoated chambers and vacuum components were baked out at 200 °C for 44 hours, and then the NEG coating was activated at 160 °C for 48 hours. As a result, the pressures in the neighboring chambers reached as low as 10-8 Pa. The conditioning of the vacuum chambers with irradiation of Synchrotron radiation evolved favorably as had been expected by a combined simulation of Synrad and Molflow, leading to a satisfactory recovery of the beam lifetime. Vacuum performance of the NEG-coated chamber was assessed especially by means of a residual gas analysis, and the properties of the NEG film were characterized by surface analyses including SEM, EDX, and XRD.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP019  
About • paper received ※ 16 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP021 Comparison of TiZrV Non-evaporable Getter Films Deposited by DC Magnetron Sputtering or Quantitative Deposition 1283
SUSPFO057   use link to see paper's listing under its alternate paper code  
 
  • X.Q. Ge, W. Li, J.Q. Shao, S. Wang, Y.G. Wang, Y. Wang, W. Wei, B. Zhang, Y.X. Zhang
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  Ti-Zr-V non-evaporable getter (NEG) films have been widely used in vacuum chambers of various accelerators since their discovery. Recently, we have used a new method called ’quantitative deposition’ to deposit Ti-Zr-V NEG films on nichrome substrates. The surface morphology and surface chemical bonding information were collected by scanning electron microscopy. Although the film deposited by DC magnetron sputtering has more uniform grain growth, smoother grain boundaries and higher porosity, the two films all have porous network structure and can be used as getter films.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP021  
About • paper received ※ 24 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP029 Establishing a Laser Treatment to Suppress the Secondary Electron Emission 1303
SUSPFO071   use link to see paper's listing under its alternate paper code  
 
  • Y.G. Wang, X.Q. Ge, X.T. Pei, S.W. Wang, Y. Wang, B. Zhang, B.L. Zhu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  Laser treatment has a significant inluent on suppressing the secondary electron emission(SEE). The new synchrotron radiation light source, the Hefei Advanced Light Source(HALS) has a strict requirement on the SEE. In this paper, we used a 355nm laser to process copper sample. After the laser treatment, the secondary electron yield(SEY) reduced from 2.05 to 0.86. We used the scanning electron microscope(SEM) to analysis the surface of sample after the laser treatment.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP029  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP031 Research on Secondary Electron Emission Characteristics of Diamond-like Carbon Thin Films 1306
SUSPFO081   use link to see paper's listing under its alternate paper code  
 
  • Y.X. Zhang, X.Q. Ge, W. Li, J.Q. Shao, S. Wang, Y.G. Wang, Y. Wang, W. Wei, B. Zhang, B.L. Zhu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  In modern particle accelerators, the build-up of electron cloud is a main limiting factor for the achievement of high-quality beam. Among the techniques to mitigate it, coating the internal walls of the beam pipes with a thin film which has a low secondary electron yield (SEY) is considered to be one of the most effective means. From several earlier studies, it was found that diamond-like carbon (DLC) thin films are potential coatings. This paper is mainly about the research on secondary electron emission characteristics of DLC thin films. The secondary electron emission (SEE) tests were done at temperature of 298 K and vacuum pressure of 2×10-9 Torr. Here, we obtained the characteristics of the SEE from DLC film coatings with different thickness under ultrahigh-vacuum (UHV) conditions. The maximum secondary electron yield (SEY), δmax, of the DLC thin films under different primary electron doses were also obtained, respectively.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP031  
About • paper received ※ 26 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP033 Design of the Neutron Imaging Differential Pumping Line at LLNL 1312
 
  • J.A. Caggiano, D. Castronovo, P. Fitsos, D.J. Gibson, J. Hall, M.S. Johnson, R.A. Marsh, B. Rusnak
    LLNL, Livermore, California, USA
 
  Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
The neutron imaging system at LLNL is a radiographic capability for imaging objects with fast, quasi-monoenergetic neutrons at ≤1mm spatial resolution. The neutron production source is a deuteron beam (4 or 7 MeV) incident upon a rotating, high-pressure, windowless, pure-deuterium gas target. The windowless nature of the target combined with the high pressure leads to significant gas leakage upstream of the neutron production target. This leakage degrades the imaging quality by (1) increasing the depth-of-field blurring and (2) increasing the beam diameter and divergence in the transverse direction via angular straggling in the residual gas. To mitigate these effects, and guided by bench tests and simulations, we designed a differential pumping line (DPL) to ensure the highest quality imaging system. The system consists of three primary stages (chambers), each separated by carefully shaped apertures. These apertures can be long and thin with low-angle tapers due to the high quality of the beam optics (convergence at the target < 5mrad) and low emittance of the beam (~5 pi mm-mrad). The primary cascaded roots pumps are sized to remove >99% of the incoming mass flow in each stage, ensuring that by the third stage furthest from the target, turbomolecular pumps are able to operate in a nominal ~mTorr range. We anticipate full system testing with helium in mid 2019.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP033  
About • paper received ※ 30 April 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP035 Design of the Vacuum System of the FCC-ee Electron-Positron Collider 1319
 
  • R. Kersevan, C. Garion
    CERN, Geneva, Switzerland
 
  The Future Circular Collider (FCC) Design Study includes the twin storage ring (FCC-ee) where electrons and positrons are stored and made to collide inside two detectors. The vacuum system of FCC-ee must be designed in order to deal with a lower-energy (45.6 GeV), high-current (1390 mA) Z-pole machine and at a later stage with a higher-energy (182.5 GeV) low-current (5.4 mA). The former machine is the most challenging one from the point of view of vacuum, since the photon-stimulated desorption (PSD) generated by the copious synchrotron radiation (SR) fans is quite large. While several concepts have been considered at the beginning, the design retained for the Conceptual Design Report (CDR) is one where the cross-section of the vacuum chamber (VC) in the arcs is a scaled-down version of the one implemented in the SUPERKEKB collider. Contrary to SUPERKEKB tough, the SR fans are absorbed by many short absorbers, with average spacing of 5.8 m. This allow a localization of the PSD gas load and to place lumped pumps in front of the SR absorbers, to maximize the pumping efficiency. The VC design is compatible with the design of the common-yoke dipoles and quadrupoles. The VC material is copper alloy. Optimization of the pressure profiles has been carried out by means of extensive coupled montecarlo simulations, for SR and molecular flow. For the higher energy versions of the machine, for which the SR spectra are characterized by critical energies well above the Compton edge, the localized absorbers facilitate also shielding the tunnel and any radiation-sensitive machine components from X-ray photon damage, by installing short high-Z material around the absorbers. The major features of the CDR relevant for vacuum will be highlighted in the paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP035  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP036 Results on the FCC-hh Beam Screen Sawtooth at the Kit Electron Storage Ring Kararesults on the Fcc-Hh Beam Screen Sawtooth at the Kit Electron Storage Ring Kara 1323
 
  • L.A. Gonzalez, V. Baglin, I. Bellafont, P. Chiggiato, C. Garion, 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 the FCC-hh beam screen (BS) prototype has been carried out with the aim of testing it at room temperature on the Karlsruhe Institute of Technology (KIT) 2.5 GeV electron storage ring KARA (KArlsruhe Research Accelerator) light source. The BS prototype was 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 quite well the one foreseen for the 50+50 TeV FCC-hh proton collider. The BS prototype (2 m in length) was manufactured according to the base line design (BD) of the FCC-hh BS. It implements a saw-tooth profile designed to absorb the SR generated at the bending magnets. Also, a laser-ablated anti-electron cloud surface texturing [2] was applied at the BS inner walls. We present here the results obtained at BESTEX and the comparison of the results obtained during irradiation of the saw-tooth profile at different geometric configurations.
This activity has been carried out in the framework of the EuroCirCol* collaboration (work package 4 "Cryogenic Beam Vacuum System").
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP036  
About • paper received ※ 13 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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TUPMP037 Recent Developments of Monte-Carlo Codes Molflow+ and Synrad+ 1327
 
  • R. Kersevan, M. Ady
    CERN, Geneva, Switzerland
 
  Molflow+ and Synrad+ are Monte Carlo simulation tools for ultra-high vacuum and synchrotron radiation, respectively. Over the years they have become a common tool for designing and analysing the vacuum system of particle accelerators. This contribution gives a short summary about new features added since IPAC-14*. Some highlights: In traditional Monte Carlo simulations, one simulated ’virtual’ particle represents a given number of physical molecules or photons. This is a weakness where the pressure or flux of the simulated system spans across multiple orders of magnitude. Synrad now supports low flux mode, a weighed Monte Carlo technique where the represented number of photons is reduced at every reflection, providing significantly better statistics at low flux regions. As for Molflow+, angle maps allow recording the molecules, directional distribution at any point, and then desorb a reduced gas quantity according to the recording. In linear systems, this allows iterative simulations that have been proven to treat systems up to 7 orders of magnitude of pressure difference. Without the new technique the computing time would be prohibitively slow on desktop computers, which is what most users of the two codes use. Both codes now have a built-in geometry builder that allows creating simple models through a set of 3D operations, and modifying those imported from CAD tools. Molflow+ has recently become open source, and it has been made compatible with, and tested on different versions of Linux and macOS. Examples of application of Molflow+ to novel Beam Gas Curtain detector and the design of the FCC-ee vacuum system will be given, alongside with some benchmarking runs against data published in literature.
* M. Ady, R. Kersevan, "Introduction to the Latest Version of the Test-particle Monte Carlo Code Molflow+", Proc. IPAC’14, Dresden, Germany, June 2014, pp. 2348-2350.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP037  
About • paper received ※ 13 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP038 Summary of Modelling Studies on the Beam Induced Vacuum Effects in the FCC-hh 1331
 
  • I. Bellafont, R. Kersevan, L. Mether
    CERN, Geneva, Switzerland
 
  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.
EuroCirCol is a conceptual design study of a Future Circular Collider (FCC-hh) which aims to expand the current energy and luminosity frontiers that the LHC has established. The vacuum chamber of this 50 TeV, 100 km collider, will have to cope with unprecedented levels of synchrotron radiation power for proton colliders, dealing simultaneously with a tighter magnet aperture. Since the high radiation power and photon flux will release large amounts of gas into the system, the difficulty to keep a low level of residual gas density increases considerably compared with the LHC. This article presents a study of the beam induced vacuum effects for the FCC-hh novel conditions, the different phenomena which, owing to the presence of the beam, have an impact on the vacuum level of the accelerator. To achieve this, a novel beam screen has been proposed, featuring specific mitigating measures aimed at dealing with the beam induced effects. It is concluded that thanks to the new beam screen design, the vacuum level in the FCC-hh shall be adequate, allowing to reach the molecular density requirement of better than 1015 H2/m3 with baseline beam parameters within the first months of conditioning.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP038  
About • paper received ※ 10 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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TUPMP041 Preliminary Design of RF-Shielded Bellows 1341
 
  • Y.T. Huang, C.K. Chan, C.-C. Chang, C.M. Cheng, P.J. Chou, Y.C. Yang
    NSRRC, Hsinchu, Taiwan
 
  A new design of RF-shielded bellows is proposed for the TPS to alleviate wake field effects and Joule heating resulting from contact resistance at the contact interface of sliding two dissimilar metals. Most efforts are put into controlling corrosion which is regarded as the main cause of electrical contact degradation. Rh-Au is chosen as a mating interface because they are stable under high temperature condition. Experimental tests are made to find an effective plating thickness of Rh and Au and to determine a suitable normal load applicable on the Rh-Au interface. A preliminary design of RF-shielded bellows that can sustain thousands of cycles during their lifetime is under testing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP041  
About • paper received ※ 06 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP042 The Beam Cleaning Analysis for the TPS Vacuum System 1344
 
  • Y.C. Yang, C.K. Chan, C.-C. Chang, A.Y. Chen, J.-Y. Chuang, C.H. Huang
    NSRRC, Hsinchu, Taiwan
 
  Commissioning for the TPS, a low-emittance 3-GeV synchrotron ring, started in December 2014 and is now currently operating in top-up mode at 400mA for users. Until the last machine shut down in December 2018, a total beam dose of 4919 Ah was accumulated and the beam cleaning effect decreased the dynamic pressure to 1.5×10-11 Pa/mA. During past years operation, several vacuum chambers were replaced to improve vacuum performance and avoid exposure to synchrotron radiation from insertion devices. In this paper, the beam cleaning evolution of new vacuum sections will be discussed and compared with experience in the rest of the storage ring. A particular cleaning evolution could be predicted and can be referenced for machine shutdown planning in the future.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP042  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP044 Special Aluminum Gasket Sealing of Non-circular Profile Flanges for the Accelerator UHV Systems 1347
 
  • G.Y. Hsiung
    NSRRC, Hsinchu, Taiwan
 
  Most of the beam ducts for the accelerators are not regularly the circular profile. Unfortunately, the conflat (CF-) flanges and the gaskets with non-circular profile were not commercially available. Besides, additional RF-contact bridges between the flanges must be built in for mitigating the impedance from the flange-gaps. In this presentation, various types of the aluminum (Al-) gaskets designed for the non-circular profile Al-flanges for the accelerator ultrahigh vacuum (UHV) systems are introduced. The surface of the Al-flange is flat to accommodate the special Al-gasket with knife edges for the sealing. Both the flange and gasket are manufactured by the oil-free Ethanol-CNC-machining process that any non-circular profile, e.g. rectangular, race-track, key-hole, etc., flanges can be precisely produced. The inner diameters of the gasket just suits those of the flanges that the impedance from the gap is significantly reduced. The flanges and gaskets after oil-free machining can be assembled immediately without any chemical cleaning. The experimental results for the as-mentioned non-circular profile Al-flanges reveal the UHV quality at pressure < 20 nPa after vacuum baking.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP044  
About • paper received ※ 15 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP050 Conceptual Design of the Diamond-II Vacuum System 1362
 
  • M.P. Cox, C. Burrows, A.G. Day, J. A. Dymoke-Bradshaw, R.K. Grant, N.P. Hammond, X. Liu, A.G. Miller, H.S. Shiers, N. Warner
    DLS, Oxfordshire, United Kingdom
 
  The conceptual design of the vacuum system for the Diamond-II storage ring upgrade is described. Due to the small vessel cross section, typically 20 mm inside diameter (ID), and the consequent conductance limitation, distributed pumping is provided by non-evaporable getter (NEG) coating supplemented by ion pumps at high gas load locations. In-situ bakeout is incorporated to allow rapid recovery from both planned vacuum interventions and unplanned vacuum events. The vacuum vessels are constructed mainly from copper alloy while stainless steel is used in regions of AC magnets requiring low electrical conductivity. The proposed layout, engineering and build sequence of the vacuum system are described along with gas flow simulations confirming the vacuum performance advantages of NEG-coated vessels compared with uncoated vessels.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP050  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP051 MULTIPACTOR SUPPRESSION BY LASER ABLATION SURFACE ENGINEERING FOR SPACE APPLICATIONS 1365
 
  • R. Valizadeh, A.N. Hannah, O.B. Malyshev, B.S. Sian
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • J.S. Colligon
    University of Huddersfield, Huddersfield, United Kingdom
  • Y. Dan
    Hitachi High-Technologies Corp., Ibaraki-ken, Japan
  • V. R. Dhanak
    The University of Liverpool, Liverpool, United Kingdom
  • J. Mutch
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • B.S. Sian
    UMAN, Manchester, United Kingdom
  • N. Sykes
    Micronanics Laser Solution Center, Didcot, United Kingdom
 
  Developing a surface with low Secondary Electron Yield (SEY) is one of the main ways of mitigating electron cloud and beam-induced electron multipacting in high-energy charged particle accelerators and space-borne RF equipment for communication purposes. In this study we report on the secondary electron yield (SEY) measured from silver coated aluminium alloy as-received and after laser ablation surface engineering (LASE). Analysis shows the SEY can be reduced by 43% using LASE. EDX and SEM analysis shows it is possible to reduce the SEY whilst maintaining the original surface composition.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP051  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPMP054 Investigations on Cryopanels in the Room Temperature Heavy Ion Synchrotron SIS18 1372
 
  • L.H.J. Bozyk, S. Aumüller, P.J. Spiller
    GSI, Darmstadt, Germany
 
  The heavy ion synchrotron SIS18 at GSI will serve as injector ring for the FAIR-facility and provide high intensity heavy ion beams. The operation of such beams requires the usage of low charge states, which have high cross sections for ionization. To overcome this issue, many upgrade measure have been realized in the past decade, such as the installation of an ion catcher system with low desorption surfaces and coating 65% of the circumference of SIS18 with NEG to lower the static gas pressure. Since the vacuum dynamics during operation prevent the achievement of the intensity goals for FAIR, new concepts have to be developed, to increase the beam intensity. One idea is the installation of additional pumping speed in the form of cryogenic surfaces. Heavy residual gas components, which have the highest ionization cross sections can be cryopumped at moderate temperatures, i.e. already at 50-80 K. In fact, the only typical residual gas component which can not be pumped via cryosorption in this temperature regime is Hydrogen, which has a factor 50 lower ionization cross sections than Argon, the heaviest residual gas component. In this paper, we present a study of the integration of cryopanels into the vacuum chambers of SIS18.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP054  
About • paper received ※ 13 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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TUPMP056 LANSCE Vacuum System Improvements in the Last ~10 Years 1375
 
  • T. Tajima, J.E. Bernal, M.J. Borden, J.P. Chamberlin, F.A. Martinez, J.F. O’Hara, A. Poudel, K.A. Stephens
    LANL, Los Alamos, New Mexico, USA
 
  Funding: DOE/NNSA
The Los Alamos Neutron Science Center (LANSCE) accelerator started its operation in 1972. To mitigate the vulnerability due to old equipment and to restore the 120 Hz operation capability we lost a while ago, we have gone through a refurbishment / risk mitigation project since 2007. This paper summarizes the improvements in the vacuum systems in the last ~10 years and shows some data on the downtimes caused by vacuum failures. The refurbished equipment is significantly more maintainable and will contribute to extend the life of this old accelerator, but it has been a challenge to reduce the downtime. Some examples that caused a long downtime will be described.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP056  
About • paper received ※ 24 May 2019       paper accepted ※ 26 May 2019       issue date ※ 21 June 2019  
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TUPGW108 Characterization of NEG Coatings for SLS 2.0 1662
 
  • M.M. Dehler, A. Citterio
    PSI, Villigen PSI, Switzerland
  • S. Alberti, J.P. Hogge
    SPC-EPFL, Lausanne, Switzerland
  • M. Hahn, H.P. Marques
    ESRF, Grenoble, France
  • X.Y. Liu
    USTC/NSRL, Hefei, Anhui, People’s Republic of China
 
  To limit desorption and ameliorate pumping of the narrow 20 mm aperture vacuum chamber of SLS2.0, it is planned to fully coat it with nonevaporable getter (NEG) material. NEG coating can be produced with different structural characteristics, from dense films to columnar growth, with corresponding distinct electrical properties affecting the machine impedance and the instability threshold of the accelerator. In order to evaluate and characterize the coating process for geometries similar to the SLS chamber, we measured the resonance properties of coated and uncoated shorted waveguide pieces. First tests were done with standard X band waveguides at 12 and 7 GHz. Test setups using elliptical cross sections are in preparation, also for higher frequencies allowing the characterization of thin NEG layers. The final goal is to have a standardized process to test of samples coated by external producers. We describe the setups and first results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW108  
About • paper received ※ 10 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPGW109 Conceptual Design of Vacuum Chamber for SPS-II Storage Ring 1666
 
  • T. Phimsen, S. Chaichuay, N. Juntong, P. Klysubun, S. Prawanta, P. Sudmuang, P. Sunwong
    SLRI, Nakhon Ratchasima, Thailand
  • R. Deepan, A. Khamkham
    Suranaree University of Technology, Nakhon Ratchasima, Thailand
 
  The SPS-II is a 3 GeV ultralow emittance light source which is now under studied and designed by Thailand Synchrotron Light Research Institute (SLRI). The SPS-II storage ring is based on Double-Triple Bend Achromat (DTBA) cell with a circumference of 321.3 m aiming for horizontal emittance of less than 1 nm-rad. The compact lattice leaves narrow space for vacuum components. The small gap between poles of the magnets requires narrow vacuum chambers and limits the conductance of the chambers. The chambers will be made by stainless steel with a thickness of 1.5 mm. the cross section of beam duct is 40 mm × 16 mm elliptical shape. The bending chamber is designed as a long triangular chamber such that photon absorber can be installed as far from the light source as possible to lower the power density of the heat load. The overview of designed vacuum system for the SPS-II is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW109  
About • paper received ※ 14 May 2019       paper accepted ※ 18 May 2019       issue date ※ 21 June 2019  
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WEXXPLS2 Accelerator Vacuum Windows: A Review of Past Research and a Strategy for the Development of a New Design for Improved Safety and Longevity for Particle Accelerators 2237
 
  • C.R. Ader, M.L. Alvarez, J.S. Batko, R. Campos, M.W. McGee, A.C. Watts
    Fermilab, Batavia, Illinois, USA
 
  Funding: Fermi National Accelerator Laboratory
Vacuum window research continues at Fermilab and this paper will examine cost effective, consistent designs which can have a significant impact on accelerator laboratories in terms of safety and cost. Issues such as the design, materials, analysis, testing and fabrication are addressed, including beam scattering and materials cost-benefit analysis and examining potential material substitutes for beryllium. A previous research paper has examined current fabrication and design techniques and also failure modes at Fermi, and this paper focuses on emerging and novel technologies for vacuum window fabrication. Many different paths have been taken by High Energy Physics (HEP) Laboratories throughout the world with varying success. The history of vacuum window development is extensive and not well defined, and a matrix of the research already completed on materials and joint design for vacuum windows will be shown. This report finally includes a treatise for vacuum window technology and a view towards emerging designs and materials and discusses future advances of research such as fabrication techniques including additive manufacturing and ultrasonic welding. Further exploration into these would prove beneficial to developing vacuum windows that are safer and stronger while being more transparent to the beam.
 
slides icon Slides WEXXPLS2 [3.139 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEXXPLS2  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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WEXXPLS3 Is it Possible to Use Additive Manufacturing for Accelerator UHV Beam Pipes? 2240
 
  • G. Sattonnay, M. Alves, S. Bilgen, B.J. Bonnis, A. Gonnin, D. Grasset, S. Jenzer, F. Letellier-Cohen, B. Mercier, E. Mistretta
    LAL, Orsay, France
  • F. Brisset
    ICMMO, Orsay, France
 
  Funding: Work supported by a grant from IN2P3/CNRS, program I3D metal
Recently, additive manufacturing (AM) has revolutionized mechanical engineering by allowing the quick production of mechanical components with complex shapes. AM by selective laser melting (SLM) is an advanced manufacturing process which uses lasers to melt metal powders one layer at a time to produce final 3D components. This technology could be also used to make Ultra High Vacuum components. Therefore, we investigated in this work the reproducibility of AM 316L stainless steel properties for different specimen supplied by several manufacturers with the same SLM process. Clearly, the microstructure and therefore the mechanical properties of the investigated AM samples are different as a function of manufacturers: indeed, they are largely influenced by processing parameters, which produces heterogeneous and anisotropic microstructures that differ from traditional wrought counterparts. Samples were also submitted to bake cycles at high temperature, in order to check the structural stability of material properties after heat treatments. The outgassing rates and the secondary emission yield of vacuum components constructed from AM 316L were also measured. Finally, the possibility to use AM for accelerator beam pipes will be discussed.
 
slides icon Slides WEXXPLS3 [9.009 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEXXPLS3  
About • paper received ※ 01 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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