IPAC2016 - Classification: 07 Accelerator Technology / T14 Vacuum Technology

Paper	Title	Page
TUOCB01	First Commissioning of the SuperKEKB Vacuum System	1086
	Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui KEK, Ibaraki, Japan
	The SuperKEKB, an electron-positron collider with asymmetric energies in KEK, has started the first commissioning with beams this year. One of major tasks in the commissioning is the beam scrubbing of new beam pipes in order to increase the beam lifetime and to decrease the background noise of the particle detector in the coming physics run. The temperatures and the vacuum pressures of new vacuum components, such as the bellows chambers, gate valves and the beam collimators, should be checked in this run. The decrease rate in the vacuum pressure are measured to estimate the vacuum scrubbing effect. Reported here will be the results obtained during the first commissioning and the present status of the vacuum system.
	Slides TUOCB01 [2.526 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUOCB02	Low Secondary Electron Yield of Laser Treated Surfaces of Copper, Aluminium and Stainless Steel	1089
	R. Valizadeh, P. Goudket, O.B. Malyshev, B.S. Sian, S. Wang STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom M.D. Cropper, S. Wang Loughborough University, Loughborough, Leicestershire, United Kingdom P. Goudket Cockcroft Institute, Warrington, Cheshire, United Kingdom B.S. Sian UMAN, Manchester, United Kingdom N. Sykes Micronanics Laser Solution Center, Didcot, United Kingdom
	Funding: STFC Reduction of SEY was achieved by surface engineering through laser ablation with a laser operating at • = 355 nm. It was shown that the SEY can be reduced to near or below 1 on copper, aluminium and 316LN stainless steel. The laser treated surfaces show an increased surface resistance, with a wide variation in resistance found de-pending on the exact treatment details. However, a treated copper surface with similar surface resistance to aluminium was produced.
	Slides TUOCB02 [94.339 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMB025	The Effect of Magnetic Field on the Secondary Electron Yield in the Ultra-High Vacuum Environment	3281
	J. Wang, Y. Wang, W. Wei, Y.H. Xu, B. Zhang, T. Zhang, Y.X. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	A secondary electron emission measurement system has been designed and used to study the secondary electron emission (SEE) of different materials with an independently adjustable energy of 50 eV to 5 keV at National Synchrotron Radiation Laboratory. Here, we obtained the characteristics of the SEE yield from Pd film coatings, under the condition of magnetic field and without magnetic field. Then it was analysed that the effect of magnetic field on the secondary electron yield in the ultra-high vacuum environment. The results show that magnetic field shielding is critical to avoid the influence of magnetic field during secondary electron yield (SEY) measurements.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMB026	Research on Low Secondary Electron Yield Materials for Future Accelerators	3284
	J. Wang, Y. Wang, W. Wei, Y.H. Xu, B. Zhang, T. Zhang, Y.X. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	For future accelerators, such as SPPC (SEYmax <1.2), the build-up of electron cloud generated in the beam pipes considerably affect the stability of particle beams. Therefore, it is critical to look for steady and low secondary electron yield (SEY) material for future high intensity accelerators.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY001	Design and R&D for the SPring-8 Upgrade Storage Ring Vacuum System	3651
	M. Oishi, T. Bizen, H. Ohkuma, M. Shoji, S. Takahashi, K. Tamura, Y. Taniuchi JASRI/SPring-8, Hyogo-ken, Japan
	Conceptual design report for the SPring-8 upgrade project (SPring-8-II) was published in November of 2014. Vacuum system for the targeted storage ring should handle some fateful boundary conditions, such as miniaturization of vacuum chamber and increase in number of photon absorbers resulting from the multi-bend achromat configuration. Furthermore, reuse of the existing tunnel brings the severe packing factor issue of vacuum components and the time constraints issue of one-year blackout. Considering the above circumstances, a concept of 12-m long vacuum chamber with welded integral structure was proposed to omit in-situ baking. The 12-m long chamber will be evacuated to ultra-high vacuum by ex-situ baking followed by NEG activation, and moved to the tunnel with special thin gate valves at both ends. Recently, the chamber material has been changed from aluminum alloy to stainless steel (SS) from the viewpoints of elimination of aluminum-SS transition space, beam vibration suppression, and superior outgassing property. Trial production of SS chamber is proceeding to establish appropriate manufacturing processes, while focusing on the accuracy of dimension and magnetic permeability.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY002	Fabrication of Ferrite-Copper Block by Spark Plasma Sintering (SPS)	3654
	Y. Suetsugu, T. Ishibashi, S. Terui KEK, Ibaraki, Japan H. Ishizaki, A. Kimura, T. Sawhata Metal Technology Co. Ltd., Ibaraki, Japan
	A ferrite has been well known as an effective material for absorbing electromagnetic waves. Various types of the ferrite blocks have been actually used in accelerator fields as the higher-order modes (HOMs) absorbers in the vacuum beam pipes. However, one of difficulties in using the ferrite is to bond it to the beam pipes with a sufficient adhesive force, and to assure the contact with a high thermal conductivity in vacuum. The brazing or Hot Isostatic Pressing (HIP) is not so easy owing to a low thermal expansion rate and a relatively low tensile strength of the ferrite. We established a method of fabricating a ferrite block bonded to copper by spark plasma sintering (SPS). The ferrite powders are directly sintered on a copper block in the SPS process together with some metals to relax the thermal stress between them. The sintered ferrite-copper block can be brazed or welded to other metal blocks, or directly on the beam pipes. Here reported are R&D results of the fabrication method, and some experimental results on the properties of the ferrite-copper block.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY003	Design of the RISP Vacuum Systems	3657
	D. Jeon, J.H. Cho, K.B. Lim, H.J. Son, J. Song, S.W. Yoon IBS, Daejeon, Republic of Korea H.S. Choi, T. Ha PAL, Pohang, Republic of Korea S.R. In KAERI, Daejon, Republic of Korea B.C. Kim, K.P. Kim, K.M. Kim, Y.S. Kim NFRI, Republic of Korea
	The vacuum requirement of the RISP heavy ion accel-erator facility has been derived that meets the beam loss requirement and the vacuum system design is carried out using the 3D Molflow+ code verifying the vacuum re-quirement. We used realistic outgassing values of the materials of the vacuum chambers and beam pipes. We are designing detailed vacuum system specification and configuration including pumps, gate valves, and vacuum gauges along with the interlock system and differential pumping stations.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY006	Analysis and Testing of a New RF Bridge Concept as an Alternative to Conventional Sliding RF Fingers in LHC	3660
	J. Perez Espinos, C. Garion CERN, Geneva, Switzerland
	RF fingers are used as transition elements in beam vacuum line interconnections to ensure the continuity of the vacuum system wall within acceptable beam stability requirements. The RF fingers must absorb and compensate longitudinal, angular and transversal misalignments due to both thermal effects, during bake-out or cooldown processes, and mechanical movements during assembly, alignment, commissioning and operation phases. The new RF bridge concept is based on a deformable thin-walled structure in copper beryllium, which fulfils the above requirements without the need of sliding contacts. Mechanical tests have been carried out to characterize the response and the lifetime of such a component under different loading conditions. In addition, finite element models have been used to estimate the behaviour. The influence of different material grades and heat treatments on the reliability is presented. The paper includes a detailed analysis of the prototyping and testing phases that have led to a final design of the system, qualified on a dedicated test bench, for the collimator vacuum modules of LHC.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY007	Vacuum Performance of Amorphous Carbon Coating at Cryogenic Temperature with Presence of Proton Beams	3663
	R. Salemme, V. Baglin, G. Bregliozzi, P. Chiggiato CERN, Geneva, Switzerland
	Amorphous carbon (a-C) coating is the baseline electron multipacting mitigation strategy proposed for the Inner Triplets (IT) in the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). As of 2014, the COLD bore EXperiment (COLDEX) is qualifying the performance of a-C coating at cryogenic temperature in a LHC type cryogenic vacuum system. In this paper, the experimental results following a cryogenic vacuum characterization of a-C coating in the 5 to 150 K temperature range are reviewed. We discuss the dynamic pressure rise, gas composition, dissipated heat load and electron activity observed within an accumulated beam time of 9 Ah. The results of dedicated experiments including pre-adsorption of different gas species (H2, CO) on the a-C coating are discussed. Based of phenomenological modeling, up-to-date secondary emission input parameters for a-C coatings are retrieved for electron cloud build-up simulations. Finally, first implications for the HL-LHC ITs design are drawn.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY008	Mechanical and Vacuum Stability Studies for the LHC Experiments Upgrade	3667
	J. Sestak, G. Bregliozzi, P. Chiggiato CERN, Geneva, Switzerland
	In April 2015, the Large Hadron Collider (LHC) has entered its second operational period that will last for 3 years with expected end of the operations at the beginning of 2019. Afterward, the LHC will undergo a long shutdown (LS2) for upgrade and maintenance. The four LHC experiments, ATLAS, ALICE, CMS and LHCb, will experience an important upgrade too. From the design point of view, the LS2 experimental beam vacuum upgrade requires multi-disciplinary approach: based on the geometrical envelope defined by experiment, the vacuum chambers size and shape must be optimized. This included Monte Carlo pressure profile simulations and vacuum stability studies in order to meet the specific pressure requests in the interaction region. Together with vacuum studies the structural analysis are performed in order to optimise chambers thickness and position of the operational and maintenance supports. The material selection for vacuum chambers in the experimental area follows the CERN ALARA (as low as reasonably achievable) principle. This paper gives an overview of the LS2 experimental vacuum sectors upgrades. The most extensive design studies, done for the two experiments CMS and ALICE are discussed in detail.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY009	Coaxial Wire Method Adapted to Weakly Coupled Resonator Mode for LHC RF Fingers Evaluation	3670
	C. Vollinger, F. Caspers, T. Kaltenbacher CERN, Geneva, Switzerland
	In high intensity particle accelerators, RF contact fingers are commonly used to carry the beam induced image current. In addition, they reduce beam impedance by shielding the outer bellows required to compensate mechanical displacements between components. In order to assess the resulting beam impedance from a specific bellow/RF finger configuration, RF measurements are routinely carried out. During these measurements, it was observed that cavity modes in the volume between the fingers and the bellow undulation arise. These resonances occur at significantly higher frequencies than the expected frequency range of interest. Due to their broadband nature, the tails of the imaginary part of these resonances reach into the lower frequency range of interest where it contributes to the beam coupling impedance of the device. For proper evaluation of this contribution, a time domain delay technique in TDT (time domain transmissiometry) was used in order to overcome shortcomings that arise if the classical coaxial wire method is applied to these structures. We present the theory of our method and discuss it in view of the data measured on deformable fingers that were studied for the LHC.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY010	LHC Beam Vacuum Evolution During 2015 Machine Operation	3673
	C. Yin Vallgren, G. Bregliozzi, P. Chiggiato CERN, Geneva, Switzerland
	The LHC successfully returned to operation in April, 2015 after almost 2 years of Long Shutdown 1 (LS1) for various upgrade and consolidation programs. During 2015 operation, the LHC operated for more than 1000 fills. The 2015 LHC proton physics ended with 2244 bunches per beam circulating with 25 ns bunch spacing at top energy of 6.5 TeV. This paper summarizes the dynamic vacuum observations in different locations along the LHC during dedicated fills as well as during physics runs with both 50 ns and 25 ns bunch spacing. The causes for the dynamic pressure rises are investigated and are presented. A clear beam conditioning effect is observed, as well as a so-called de-conditioning effect. Furthermore, for the experimental areas, the dynamic pressure evolution is also presented.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY011	Chamber Upgrade for EPU48 in TPS	3676
	I.C. Sheng, C.K. Chan, C.-C. Chang, C.M. Cheng, Y.T. Cheng, J. -Y. Chuang, Y.M. Hsiao, Y.T. Huang, C. Shueh, L.H. Wu, I.C. Yang NSRRC, Hsinchu, Taiwan
	Due to high total power and power density in Taiwan Photon Source (TPS) of EPU48 (Elliptical Polarized Undulator) in double minimum sector, we fabricate a new Aluminum vacuum chamber to increase sufficient room for synchrotron radiation to pass through without damage the storage ring chamber. A new method of in-site replacement of bending chamber is also presented, the result of this replacement procedure shows that it is very cost-effective as well as good UHV vacuum quality.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY013	Laser-Beam Welding for a TPS Beam-Position Monitor	3679
	Y.T. Huang, C.-C. Chang, J.-R. Chen, G.-Y. Hsiung, S-N. Hsu NSRRC, Hsinchu, Taiwan
	The TPS beam-position monitor has two feedthroughs in one flange structure. The hermetic seal was formed with laser-beam welding (LBW). Nd-YAG LBW was adopted to weld a button electrode with a feedthrough; CO2 LBW served for a feedthrough and a flange, Fig. 1. A robotic arm was used for Nd-YAG LBW so that it could accomplish the complicated geometry of the welded joint. Although the CO2 laser was not coordinated with a robotic arm, fixtures were made to implement a circular welded joint the same as welding the feedthrough into a flange. For not only Nd-YAG but also CO2 LBW, the cover gas is the major key that avoids oxidation from atmospheric oxygen and maintains shiny weld beads. Taguchi methods were exploited to find the appropriate parameters for the Nd-YAG pulsed laser, for instance, the laser power, pulse-filling time, frequency etc.. This paper presents the process and details of laser-beam welding of two types for a beam-position monitor. Laser beam weld, Nd-YAG, CO2, POWER, filling time, beam position monitor
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY014	Study of the Non-evaporable Ti-Zr-V Films Grown on Different Materials	3682
	L.H. Wu, C.M. Cheng, Y.T. Huang, S.Y. Perng, I.C. Sheng, C. Shueh NSRRC, Hsinchu, Taiwan
	The non-evaporable (NEG) Ti-Zr-V films were coated on the different vacuum-chamber materials, including the extruded aluminum samples (Al), the extruded seamless stainless steel samples (S.S.), CuCrZr alloys, and oxygen-free copper (OFC) plates. The NEG films were fabricated by using the direct current (DC) sputtering method. The secondary electron microscopy images showed that the morphology of NEG films was different on these various substrates. The thermal analysis (TA) presented that exothermic reaction happened by heating the samples.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY015	Measurement of the Pressure in the TPS Booster Ring	3685
	C.M. Cheng, C.K. Chan, G.-Y. Hsiung, Y.T. Huang, I.C. Sheng, L.H. Wu, I.C. Yang NSRRC, Hsinchu, Taiwan
	The booster ring of Taiwan Photon Source (TPS) is designed to provide full energy injection 3 GeV ramped up from 150 MeV with a small beam emittance. It is a synchrotron accelerator of circumference 496.8 m. The vacuum chamber through the magnets is made of thin stainless-steel tube extruded to an elliptical cross section of inner diameters 35 mm and 20 mm, and thickness 0.7 mm. The other chambers have standard 35CF round tube. The vacuum system was baked in the first installation. Because the residual stress of the stainless-steel elliptical tubing caused the magnetic field to become unstable, all elliptical tubing was removed for annealing to proceed, and reinstalled without baking. The ultimate pressure and data for the residual gas are shown as follows.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY016	Graphene Coating for the Reduction of the Secondary Electron Yield	3688
	B.S. Sian, G.X. Xia, G.L. Yu UMAN, Manchester, United Kingdom I. Kinloch, L. Lin, V. Valles University of Manchester, Manchester, United Kingdom O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom O.B. Malyshev, R. Valizadeh, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Secondary electron emission is a limiting factor for a performance of many instruments ranging from small gauges and detectors to waveguides and charged particle accelerators. There have been several methods of reducing this effect, e.g. the method of using a material with a low Secondary Electron Yield (SEY) or thin film coating with such a low SEY material. This paper describes the effect of SEY mitigation with graphene coatings on aluminium substrate. The maximum SEY (dmax) was decreased from 2.4 for bare aluminium to 1.4 with a graphene coating. Measurements were taken using an electron gun and a Faraday cup, the electron energies varied between 80 eV and 1 keV with a bias of -18 V on the sample. Other biases of -3, -5, -9, -25, -50 and -75 V were also tested however there was no effect on the SEY.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY018	Benchmarking and Calibration of Monte Carlo Vacuum Simulations with SynRad and MolFlow+	3695
	J.A. Carter ANL, Argonne, Ilinois, USA
	The APS-Upgrade project is using SynRad and MolFlow+ to evaluate the vacuum system design for the future 6 GeV, 200 mA APS-Upgrade storage ring. The goal of this work is to explore PSD outgassing predictions from the two programs in order to build confidence in pressure calculations for the APS-U storage ring vacuum system. A study is performed on calibrating PSD measurements for aluminum vacuum chambers and then applying them to APS-U vacuum system calculations. The study reveals that a PSD measurement may not reveal a single unique behavior for a vacuum material and that multiple sources should be considered for vacuum calculations.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

First Commissioning of the SuperKEKB Vacuum System

1086

Y. Suetsugu, H. Hisamatsu, T. Ishibashi, K. Kanazawa, K. Shibata, M. Shirai, S. Terui
KEK, Ibaraki, Japan

The SuperKEKB, an electron-positron collider with asymmetric energies in KEK, has started the first commissioning with beams this year. One of major tasks in the commissioning is the beam scrubbing of new beam pipes in order to increase the beam lifetime and to decrease the background noise of the particle detector in the coming physics run. The temperatures and the vacuum pressures of new vacuum components, such as the bellows chambers, gate valves and the beam collimators, should be checked in this run. The decrease rate in the vacuum pressure are measured to estimate the vacuum scrubbing effect. Reported here will be the results obtained during the first commissioning and the present status of the vacuum system.

Slides TUOCB01 [2.526 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUOCB02

Low Secondary Electron Yield of Laser Treated Surfaces of Copper, Aluminium and Stainless Steel

1089

R. Valizadeh, P. Goudket, O.B. Malyshev, B.S. Sian, S. Wang
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
M.D. Cropper, S. Wang
Loughborough University, Loughborough, Leicestershire, United Kingdom
P. Goudket
Cockcroft Institute, Warrington, Cheshire, United Kingdom
B.S. Sian
UMAN, Manchester, United Kingdom
N. Sykes
Micronanics Laser Solution Center, Didcot, United Kingdom

Funding: STFC
Reduction of SEY was achieved by surface engineering through laser ablation with a laser operating at • = 355 nm. It was shown that the SEY can be reduced to near or below 1 on copper, aluminium and 316LN stainless steel. The laser treated surfaces show an increased surface resistance, with a wide variation in resistance found de-pending on the exact treatment details. However, a treated copper surface with similar surface resistance to aluminium was produced.

Slides TUOCB02 [94.339 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMB025

The Effect of Magnetic Field on the Secondary Electron Yield in the Ultra-High Vacuum Environment

3281

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

A secondary electron emission measurement system has been designed and used to study the secondary electron emission (SEE) of different materials with an independently adjustable energy of 50 eV to 5 keV at National Synchrotron Radiation Laboratory. Here, we obtained the characteristics of the SEE yield from Pd film coatings, under the condition of magnetic field and without magnetic field. Then it was analysed that the effect of magnetic field on the secondary electron yield in the ultra-high vacuum environment. The results show that magnetic field shielding is critical to avoid the influence of magnetic field during secondary electron yield (SEY) measurements.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMB026

Research on Low Secondary Electron Yield Materials for Future Accelerators

3284

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

For future accelerators, such as SPPC (SEYmax <1.2), the build-up of electron cloud generated in the beam pipes considerably affect the stability of particle beams. Therefore, it is critical to look for steady and low secondary electron yield (SEY) material for future high intensity accelerators.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY001

Design and R&D for the SPring-8 Upgrade Storage Ring Vacuum System

3651

M. Oishi, T. Bizen, H. Ohkuma, M. Shoji, S. Takahashi, K. Tamura, Y. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan

Conceptual design report for the SPring-8 upgrade project (SPring-8-II) was published in November of 2014. Vacuum system for the targeted storage ring should handle some fateful boundary conditions, such as miniaturization of vacuum chamber and increase in number of photon absorbers resulting from the multi-bend achromat configuration. Furthermore, reuse of the existing tunnel brings the severe packing factor issue of vacuum components and the time constraints issue of one-year blackout. Considering the above circumstances, a concept of 12-m long vacuum chamber with welded integral structure was proposed to omit in-situ baking. The 12-m long chamber will be evacuated to ultra-high vacuum by ex-situ baking followed by NEG activation, and moved to the tunnel with special thin gate valves at both ends. Recently, the chamber material has been changed from aluminum alloy to stainless steel (SS) from the viewpoints of elimination of aluminum-SS transition space, beam vibration suppression, and superior outgassing property. Trial production of SS chamber is proceeding to establish appropriate manufacturing processes, while focusing on the accuracy of dimension and magnetic permeability.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY002

Fabrication of Ferrite-Copper Block by Spark Plasma Sintering (SPS)

3654

Y. Suetsugu, T. Ishibashi, S. Terui
KEK, Ibaraki, Japan
H. Ishizaki, A. Kimura, T. Sawhata
Metal Technology Co. Ltd., Ibaraki, Japan

A ferrite has been well known as an effective material for absorbing electromagnetic waves. Various types of the ferrite blocks have been actually used in accelerator fields as the higher-order modes (HOMs) absorbers in the vacuum beam pipes. However, one of difficulties in using the ferrite is to bond it to the beam pipes with a sufficient adhesive force, and to assure the contact with a high thermal conductivity in vacuum. The brazing or Hot Isostatic Pressing (HIP) is not so easy owing to a low thermal expansion rate and a relatively low tensile strength of the ferrite. We established a method of fabricating a ferrite block bonded to copper by spark plasma sintering (SPS). The ferrite powders are directly sintered on a copper block in the SPS process together with some metals to relax the thermal stress between them. The sintered ferrite-copper block can be brazed or welded to other metal blocks, or directly on the beam pipes. Here reported are R&D results of the fabrication method, and some experimental results on the properties of the ferrite-copper block.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY003

Design of the RISP Vacuum Systems

3657

D. Jeon, J.H. Cho, K.B. Lim, H.J. Son, J. Song, S.W. Yoon
IBS, Daejeon, Republic of Korea
H.S. Choi, T. Ha
PAL, Pohang, Republic of Korea
S.R. In
KAERI, Daejon, Republic of Korea
B.C. Kim, K.P. Kim, K.M. Kim, Y.S. Kim
NFRI, Republic of Korea

The vacuum requirement of the RISP heavy ion accel-erator facility has been derived that meets the beam loss requirement and the vacuum system design is carried out using the 3D Molflow+ code verifying the vacuum re-quirement. We used realistic outgassing values of the materials of the vacuum chambers and beam pipes. We are designing detailed vacuum system specification and configuration including pumps, gate valves, and vacuum gauges along with the interlock system and differential pumping stations.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY006

Analysis and Testing of a New RF Bridge Concept as an Alternative to Conventional Sliding RF Fingers in LHC

3660

J. Perez Espinos, C. Garion
CERN, Geneva, Switzerland

RF fingers are used as transition elements in beam vacuum line interconnections to ensure the continuity of the vacuum system wall within acceptable beam stability requirements. The RF fingers must absorb and compensate longitudinal, angular and transversal misalignments due to both thermal effects, during bake-out or cooldown processes, and mechanical movements during assembly, alignment, commissioning and operation phases. The new RF bridge concept is based on a deformable thin-walled structure in copper beryllium, which fulfils the above requirements without the need of sliding contacts. Mechanical tests have been carried out to characterize the response and the lifetime of such a component under different loading conditions. In addition, finite element models have been used to estimate the behaviour. The influence of different material grades and heat treatments on the reliability is presented. The paper includes a detailed analysis of the prototyping and testing phases that have led to a final design of the system, qualified on a dedicated test bench, for the collimator vacuum modules of LHC.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY007

Vacuum Performance of Amorphous Carbon Coating at Cryogenic Temperature with Presence of Proton Beams

3663

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

Amorphous carbon (a-C) coating is the baseline electron multipacting mitigation strategy proposed for the Inner Triplets (IT) in the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). As of 2014, the COLD bore EXperiment (COLDEX) is qualifying the performance of a-C coating at cryogenic temperature in a LHC type cryogenic vacuum system. In this paper, the experimental results following a cryogenic vacuum characterization of a-C coating in the 5 to 150 K temperature range are reviewed. We discuss the dynamic pressure rise, gas composition, dissipated heat load and electron activity observed within an accumulated beam time of 9 Ah. The results of dedicated experiments including pre-adsorption of different gas species (H2, CO) on the a-C coating are discussed. Based of phenomenological modeling, up-to-date secondary emission input parameters for a-C coatings are retrieved for electron cloud build-up simulations. Finally, first implications for the HL-LHC ITs design are drawn.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY008

Mechanical and Vacuum Stability Studies for the LHC Experiments Upgrade

3667

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

In April 2015, the Large Hadron Collider (LHC) has entered its second operational period that will last for 3 years with expected end of the operations at the beginning of 2019. Afterward, the LHC will undergo a long shutdown (LS2) for upgrade and maintenance. The four LHC experiments, ATLAS, ALICE, CMS and LHCb, will experience an important upgrade too. From the design point of view, the LS2 experimental beam vacuum upgrade requires multi-disciplinary approach: based on the geometrical envelope defined by experiment, the vacuum chambers size and shape must be optimized. This included Monte Carlo pressure profile simulations and vacuum stability studies in order to meet the specific pressure requests in the interaction region. Together with vacuum studies the structural analysis are performed in order to optimise chambers thickness and position of the operational and maintenance supports. The material selection for vacuum chambers in the experimental area follows the CERN ALARA (as low as reasonably achievable) principle. This paper gives an overview of the LS2 experimental vacuum sectors upgrades. The most extensive design studies, done for the two experiments CMS and ALICE are discussed in detail.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY009

Coaxial Wire Method Adapted to Weakly Coupled Resonator Mode for LHC RF Fingers Evaluation

3670

C. Vollinger, F. Caspers, T. Kaltenbacher
CERN, Geneva, Switzerland

In high intensity particle accelerators, RF contact fingers are commonly used to carry the beam induced image current. In addition, they reduce beam impedance by shielding the outer bellows required to compensate mechanical displacements between components. In order to assess the resulting beam impedance from a specific bellow/RF finger configuration, RF measurements are routinely carried out. During these measurements, it was observed that cavity modes in the volume between the fingers and the bellow undulation arise. These resonances occur at significantly higher frequencies than the expected frequency range of interest. Due to their broadband nature, the tails of the imaginary part of these resonances reach into the lower frequency range of interest where it contributes to the beam coupling impedance of the device. For proper evaluation of this contribution, a time domain delay technique in TDT (time domain transmissiometry) was used in order to overcome shortcomings that arise if the classical coaxial wire method is applied to these structures. We present the theory of our method and discuss it in view of the data measured on deformable fingers that were studied for the LHC.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY010

LHC Beam Vacuum Evolution During 2015 Machine Operation

3673

C. Yin Vallgren, G. Bregliozzi, P. Chiggiato
CERN, Geneva, Switzerland

The LHC successfully returned to operation in April, 2015 after almost 2 years of Long Shutdown 1 (LS1) for various upgrade and consolidation programs. During 2015 operation, the LHC operated for more than 1000 fills. The 2015 LHC proton physics ended with 2244 bunches per beam circulating with 25 ns bunch spacing at top energy of 6.5 TeV. This paper summarizes the dynamic vacuum observations in different locations along the LHC during dedicated fills as well as during physics runs with both 50 ns and 25 ns bunch spacing. The causes for the dynamic pressure rises are investigated and are presented. A clear beam conditioning effect is observed, as well as a so-called de-conditioning effect. Furthermore, for the experimental areas, the dynamic pressure evolution is also presented.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY011

Chamber Upgrade for EPU48 in TPS

3676

I.C. Sheng, C.K. Chan, C.-C. Chang, C.M. Cheng, Y.T. Cheng, J. -Y. Chuang, Y.M. Hsiao, Y.T. Huang, C. Shueh, L.H. Wu, I.C. Yang
NSRRC, Hsinchu, Taiwan

Due to high total power and power density in Taiwan Photon Source (TPS) of EPU48 (Elliptical Polarized Undulator) in double minimum sector, we fabricate a new Aluminum vacuum chamber to increase sufficient room for synchrotron radiation to pass through without damage the storage ring chamber. A new method of in-site replacement of bending chamber is also presented, the result of this replacement procedure shows that it is very cost-effective as well as good UHV vacuum quality.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY013

Laser-Beam Welding for a TPS Beam-Position Monitor

3679

Y.T. Huang, C.-C. Chang, J.-R. Chen, G.-Y. Hsiung, S-N. Hsu
NSRRC, Hsinchu, Taiwan

The TPS beam-position monitor has two feedthroughs in one flange structure. The hermetic seal was formed with laser-beam welding (LBW). Nd-YAG LBW was adopted to weld a button electrode with a feedthrough; CO2 LBW served for a feedthrough and a flange, Fig. 1. A robotic arm was used for Nd-YAG LBW so that it could accomplish the complicated geometry of the welded joint. Although the CO2 laser was not coordinated with a robotic arm, fixtures were made to implement a circular welded joint the same as welding the feedthrough into a flange. For not only Nd-YAG but also CO2 LBW, the cover gas is the major key that avoids oxidation from atmospheric oxygen and maintains shiny weld beads. Taguchi methods were exploited to find the appropriate parameters for the Nd-YAG pulsed laser, for instance, the laser power, pulse-filling time, frequency etc.. This paper presents the process and details of laser-beam welding of two types for a beam-position monitor.
Laser beam weld, Nd-YAG, CO2, POWER, filling time, beam position monitor

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY014

Study of the Non-evaporable Ti-Zr-V Films Grown on Different Materials

3682

L.H. Wu, C.M. Cheng, Y.T. Huang, S.Y. Perng, I.C. Sheng, C. Shueh
NSRRC, Hsinchu, Taiwan

The non-evaporable (NEG) Ti-Zr-V films were coated on the different vacuum-chamber materials, including the extruded aluminum samples (Al), the extruded seamless stainless steel samples (S.S.), CuCrZr alloys, and oxygen-free copper (OFC) plates. The NEG films were fabricated by using the direct current (DC) sputtering method. The secondary electron microscopy images showed that the morphology of NEG films was different on these various substrates. The thermal analysis (TA) presented that exothermic reaction happened by heating the samples.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY015

Measurement of the Pressure in the TPS Booster Ring

3685

C.M. Cheng, C.K. Chan, G.-Y. Hsiung, Y.T. Huang, I.C. Sheng, L.H. Wu, I.C. Yang
NSRRC, Hsinchu, Taiwan

The booster ring of Taiwan Photon Source (TPS) is designed to provide full energy injection 3 GeV ramped up from 150 MeV with a small beam emittance. It is a synchrotron accelerator of circumference 496.8 m. The vacuum chamber through the magnets is made of thin stainless-steel tube extruded to an elliptical cross section of inner diameters 35 mm and 20 mm, and thickness 0.7 mm. The other chambers have standard 35CF round tube. The vacuum system was baked in the first installation. Because the residual stress of the stainless-steel elliptical tubing caused the magnetic field to become unstable, all elliptical tubing was removed for annealing to proceed, and reinstalled without baking. The ultimate pressure and data for the residual gas are shown as follows.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY016

Graphene Coating for the Reduction of the Secondary Electron Yield

3688

B.S. Sian, G.X. Xia, G.L. Yu
UMAN, Manchester, United Kingdom
I. Kinloch, L. Lin, V. Valles
University of Manchester, Manchester, United Kingdom
O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
O.B. Malyshev, R. Valizadeh, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Secondary electron emission is a limiting factor for a performance of many instruments ranging from small gauges and detectors to waveguides and charged particle accelerators. There have been several methods of reducing this effect, e.g. the method of using a material with a low Secondary Electron Yield (SEY) or thin film coating with such a low SEY material. This paper describes the effect of SEY mitigation with graphene coatings on aluminium substrate. The maximum SEY (dmax) was decreased from 2.4 for bare aluminium to 1.4 with a graphene coating. Measurements were taken using an electron gun and a Faraday cup, the electron energies varied between 80 eV and 1 keV with a bias of -18 V on the sample. Other biases of -3, -5, -9, -25, -50 and -75 V were also tested however there was no effect on the SEY.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY018

Benchmarking and Calibration of Monte Carlo Vacuum Simulations with SynRad and MolFlow+

3695

J.A. Carter
ANL, Argonne, Ilinois, USA

The APS-Upgrade project is using SynRad and MolFlow+ to evaluate the vacuum system design for the future 6 GeV, 200 mA APS-Upgrade storage ring. The goal of this work is to explore PSD outgassing predictions from the two programs in order to build confidence in pressure calculations for the APS-U storage ring vacuum system. A study is performed on calibrating PSD measurements for aluminum vacuum chambers and then applying them to APS-U vacuum system calculations. The study reveals that a PSD measurement may not reveal a single unique behavior for a vacuum material and that multiple sources should be considered for vacuum calculations.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)