IPAC2022 - Classification: MC7: Accelerator Technology / T14: Vacuum Technology

Paper	Title	Page
TUIXSP1	Recent Achievements in the NEG Technology in Application to Coating Vacuum Chambers of Constrained Geometries
	O. Omolayo, G. Wang LBNL, Berkeley, California, USA
	ALS/ALS-U has invested great deal of effort into development of NEG technology to reduce the dependency of the next generation light sources on conventional vacuum pumps. In this presentation, we will focus on summarizing advances in design of vacuum systems with the use of NEG, including coating of chambers with small (6mm D) cross-section. In our recent experiments at ALS-U we succeeded to extend our coating techniques up to 4 m long undulator chambers. We will review experience in NEG technology acquired by several accelerator facilities.
	Slides TUIXSP1 [10.888 MB]
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUOXSP1	Origin and Mitigation of the Beam-Induced Surface Modifications of the LHC Beam Screens	780
	V. Petit, P. Chiggiato, M. Himmerlich, S. Marinoni, H. Neupert, M. Taborelli, L.J. Tavian CERN, Meyrin, Switzerland
	All over Run 2, the LHC beam-induced heat load on the cryogenic system exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpected high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. The inner copper surface of high and low heat load beam screens, extracted during the Long Shutdown 2, was analysed. On the low heat load ones, the surface was covered with the native Cu2O oxide, while on the high heat load ones CuO dominated at surface, and it exhibited a very low carbon coverage. Such chemical modifications increase the SEY and inhibit a proper conditioning of the affected surfaces. Following this characterisation, the mechanisms for CuO build-up in the LHC beam pipe were investigated on a newly commissioned cryogenic system allowing electron irradiation, surface chemical characterisation by X-ray Photoelectron Spectroscopy and SEY measurements on samples held below 15 K. In parallel, curative solutions against the presence of CuO in the LHC beam screens were explored, which could be implemented in-situ to recover a proper conditioning and lower the beam-induced heat load.
	Slides TUOXSP1 [2.669 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP1
About •	Received ※ 17 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK029	Role of Surface Chemistry in Conditioning of Materials in Particle Accelerators	2829
	G. Sattonnay, S. Bilgen, S. Della Negra, D. Longuevergne, B. Mercier, I. Ribaud Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
	For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon and ion desorption and beam instabilities induced by ion and electron clouds is a major issue. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations in particle accelerators, leading to modifications of: outgassing rates, stimulated desorption processes and a decrease of secondary emission yields (SEY). To understand the role of the surface chemistry of air exposed materials in the electron conditioning process, typical air exposed materials used in particle accelerators : thin film coatings (NEG and TiN), copper (and its oxides Cu2O and CuO) and Niobium were conditioned by low energy electron irradiation for a better understanding of Ecloud effect. First, SEY was measured to understand the changes of surface conditioning upon particle irradiation; then, surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between the surface chemistry and the conditioning phenomenon will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK029
About •	Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 05 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK032	A Vacuum System for the Milliampere Booster	2833
	R.G. Heine, C.L. Lorey KPH, Mainz, Germany
	The Milliampere Booster (MAMBO) is the injector linac for the Mainz Energy-recovering Superconducting Accelerator MESA. MESA is a multi-turn energy recovery linac with beam energies in the 100 MeV regime currently designed and built at Institut für Kernphysik (KPH) of Johannes Gutenberg-Universität Mainz. The main accelerator consists of two superconducting Rossendorf type modules, while the injector MAMBO relies on normal conducting technolgy. The MAMBO RF cavities are bi-periodic pi/2 structures that are about 2m long, each. In this paper we present the results of Molflow+ simulations of several setups of the vacuum system for MAMBO that differ in number of pumps, pumping speed and diameter of the pumping ports that are connected to the DN40 beam pipe.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK032
About •	Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 24 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK034	Vacuum System Performance of the 3 GeV Electron Storage Ring at MAX IV Laboratory	2836
	M.J. Grabski, E. Al-Dmour, S.M. Scolari MAX IV Laboratory, Lund University, Lund, Sweden
	The 3 GeV electron storage ring at MAX IV laboratory is the first synchrotron light source with compact multi-bend achromat (MBA) magnet lattice to achieve ultra-low emittance. The vacuum system of the accelerator is fully coated with non-evaporable getter (NEG) thin film to ensure low gas density. The storage ring started commissioning in August 2015 and currently delivers photon beams from insertion devices (IDs) to 9 beamlines that are in user operation or commissioning. After over 6 years of operation, the NEG coated vacuum system continues to be reliable, is conditioning well and do not pose any limitation to the accelerator operation. The average dynamic pressure is lower than the design value (below 3·10^-10 mbar) and is reducing with the accumulated beam dose. The vacuum beam lifetime is greater than 39 Ah, and the total beam lifetime is above the design value of 5 Ah - thus is not limited by the residual gas density. Several successful interventions to install new vacuum components were performed on few achromats in the storage ring during shutdowns. Some of them were done utilizing purified neon gas to vent the vacuum system, thus avoiding the need of re-activation of the NEG coating and saving intervention time without compromising the storage ring performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK034
About •	Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 28 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK035	Thermo-Mechanical Modeling and Thermal Performance Analysis of Beam Vacuum Line Interconnections and Cold Warm Transitions in HL-LHC Long Straight Section Magnets	2839
	J. Harray, C. Garion, V. Petit CERN, Meyrin, Switzerland
	The HL-LHC upgrade, aiming at increasing the LHC levelled luminosity by factor of five, relies on new superconducting magnets requiring a new beam vacuum system. Along with the challenges related to magnet design, the beam optic configuration exposes this new equipment to stringent conditions for vacuum and cryogenic performance. Both cold-warm transitions and magnet interconnections appear to be delicate components that are crucial for the thermal heat transfer between diverse subsystems. The proposed study aims at assessing the heat loads to the cryogenic system and the temperature fields in the vacuum system. A nonlinear static thermal analysis is first performed. A thermo-mechanical approach is developed to capture additional thermal resistance arising from contact between components and their behaviour during cool-down. The system is then studied under dynamic operations when beams are circulating and colliding. A thorough analysis of beam-induced heat loads under ultimate conditions highlights the different relevant contributions. Finally, the transient response of the systems is computed to assess thermal time constants.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK035
About •	Received ※ 08 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 27 June 2022 — Issue date ※ 29 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK036	Determination of Pumping and Dynamic Vacuum Properties of Conductive Quaternary Alloy of TiZrVAg Non-Evaporable Getter.	2843
	R. Valizadeh, A.N. Hannah, O.B. Malyshev STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom G.Y. Hsiung NSRRC, Hsinchu, Taiwan J.M. O’Callaghan Castella Universitat Politécnica de Catalunya, Barcelona, Spain M. Pont, N.D. Tagdulang ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	Non Evaporable Getter (NEG) coating has been employed extensively in the particle accelerator especially where the vacuum conductance of the vessel is severely restricted and ultra-high vacuum condition is required. NEG coating will significantly reduce the outgassing rate and provides active pumping surface for H₂, CO and CO₂. In addition, it has been proven that NEG coated surfaces have a very low secondary electron yield, as well as low photon and electron stimulated desorption yields. However, the existing NEG film increases the RF surface resistance of the beam pipe. In order to increase NEG coating conductivity, at ASTeC, in the past several years, the alternative NEG com-position have been studied by adding more conductive element such as Cu, Au, Al and Ag. In this study, we report on the photon stimulated desorption, activation temperature and surface resistance from room temperature to cryogenic temperature for a new NEG quaternary alloy of TiVZrAg as function of the film composition.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK036
About •	Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK037	Measurement of the Photon Stimulated Desorption for Various Vacuum Tubes at a Beam Line of TLS	2847
	G.Y. Hsiung, C.M. Cheng NSRRC, Hsinchu, Taiwan R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	For most light sources, the synchrotron radiation (SR) hit on the beam ducts or absorbers results in higher pressure rise and the consequent higher radiation level through the commissioning stage. Various surface treatments, e.g. chemical cleaning, oil-free machining, NEG-coating, etc., for the beam ducts or absorbers have been developed worldwide for mitigating the yield of Photon Stimulated Desorption (PSD). A beam line, BL19B, of 1.5 GeV Taiwan Light Source (TLS) has been modified to measure the PSD-yield of the vacuum tubes. The white light of BL19B covers the critical length at 2.14 keV is suitable for generating higher yield of the photo-electrons (PEY) and the consequent PSD-yield to be measured can be resolved wide range of 10^-2 ~ 10^-7 molecules/photon. The PSD-outgas, measured by RGA, contains the typical H₂, CO, CO₂, hydrocarbons, and Kr from NEG-coating, alcohol from ethanol machined surface, in some cases. The effect of beam-cleaning reflects the PSD-molecules generated from the SR-irradiated surface. The comparison of the PSD for the various vacuum tubes will be described in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK037
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 08 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK038	Electron Stimulated Desorption From Titanium Tube	2850
	O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Titanium is one of material that used for production of accelerator vacuum chamber and components. In this paper we report the results of vacuum properties evaluation measurements of titanium vacuum chamber. The sample was produced from 40-mm inner diameter tube made of titanium and equipped with CF40 flanges at both ends. The electron stimulated desorption (ESD) was measured after 24-h bakeout to 80, 150, 180 and 250 oC. H₂ and CO initial sticking probabilities were measured after bakeout before the ESD measurements. After ESD measurements, the initial H₂ and CO sticking probabilities were measured again together with CO sorption capacity. These measurements provide the results for ESD as a function of electron dose baked to different temperatures and demonstrate the efficiency of electron stimulated activation of titanium vacuum chamber.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK038
About •	Received ※ 25 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPOTK039	The Effect of Activation Duration on the Performance of Non-Evaporable Getter Coatings	2854
	E.A. Marshall, O.B. Malyshev, R. Valizadeh STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Non-evaporable getter (NEG) coatings can be activated at temperatures as low as 140°C. However, better pumping properties are achieved using higher temperatures, between 150-300 °C. This paper investigates whether using an increased activation duration can improve the NEG properties obtained using lower activation temperatures, and so decrease the energy and temperature requirement. This could allow a greater range of materials to be used in particle accelerator systems. Our findings have shown that increasing activation duration from 24 hrs to 1 week at 160 °C produces an improvement in the NEG pumping properties.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK039
About •	Received ※ 01 June 2022 — Accepted ※ 10 June 2022 — Issue date ※ 17 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUIXSP1

Recent Achievements in the NEG Technology in Application to Coating Vacuum Chambers of Constrained Geometries

O. Omolayo, G. Wang
LBNL, Berkeley, California, USA

ALS/ALS-U has invested great deal of effort into development of NEG technology to reduce the dependency of the next generation light sources on conventional vacuum pumps. In this presentation, we will focus on summarizing advances in design of vacuum systems with the use of NEG, including coating of chambers with small (6mm D) cross-section. In our recent experiments at ALS-U we succeeded to extend our coating techniques up to 4 m long undulator chambers. We will review experience in NEG technology acquired by several accelerator facilities.

Slides TUIXSP1 [10.888 MB]

Cite •

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

TUOXSP1

Origin and Mitigation of the Beam-Induced Surface Modifications of the LHC Beam Screens

780

V. Petit, P. Chiggiato, M. Himmerlich, S. Marinoni, H. Neupert, M. Taborelli, L.J. Tavian
CERN, Meyrin, Switzerland

All over Run 2, the LHC beam-induced heat load on the cryogenic system exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpected high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. The inner copper surface of high and low heat load beam screens, extracted during the Long Shutdown 2, was analysed. On the low heat load ones, the surface was covered with the native Cu2O oxide, while on the high heat load ones CuO dominated at surface, and it exhibited a very low carbon coverage. Such chemical modifications increase the SEY and inhibit a proper conditioning of the affected surfaces. Following this characterisation, the mechanisms for CuO build-up in the LHC beam pipe were investigated on a newly commissioned cryogenic system allowing electron irradiation, surface chemical characterisation by X-ray Photoelectron Spectroscopy and SEY measurements on samples held below 15 K. In parallel, curative solutions against the presence of CuO in the LHC beam screens were explored, which could be implemented in-situ to recover a proper conditioning and lower the beam-induced heat load.

Slides TUOXSP1 [2.669 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP1

About •

Received ※ 17 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022

Cite •

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

THPOTK029

Role of Surface Chemistry in Conditioning of Materials in Particle Accelerators

2829

G. Sattonnay, S. Bilgen, S. Della Negra, D. Longuevergne, B. Mercier, I. Ribaud
Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France

For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon and ion desorption and beam instabilities induced by ion and electron clouds is a major issue. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations in particle accelerators, leading to modifications of: outgassing rates, stimulated desorption processes and a decrease of secondary emission yields (SEY). To understand the role of the surface chemistry of air exposed materials in the electron conditioning process, typical air exposed materials used in particle accelerators : thin film coatings (NEG and TiN), copper (and its oxides Cu2O and CuO) and Niobium were conditioned by low energy electron irradiation for a better understanding of Ecloud effect. First, SEY was measured to understand the changes of surface conditioning upon particle irradiation; then, surface chemistry evolution after electron irradiation was investigated by both XPS and TOF-SIMS analyses using the ANDROMEDE facility at IJCLab. Finally, the relationship between the surface chemistry and the conditioning phenomenon will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK029

About •

Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 05 July 2022

Cite •

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

THPOTK032

A Vacuum System for the Milliampere Booster

2833

R.G. Heine, C.L. Lorey
KPH, Mainz, Germany

The Milliampere Booster (MAMBO) is the injector linac for the Mainz Energy-recovering Superconducting Accelerator MESA. MESA is a multi-turn energy recovery linac with beam energies in the 100 MeV regime currently designed and built at Institut für Kernphysik (KPH) of Johannes Gutenberg-Universität Mainz. The main accelerator consists of two superconducting Rossendorf type modules, while the injector MAMBO relies on normal conducting technolgy. The MAMBO RF cavities are bi-periodic pi/2 structures that are about 2m long, each. In this paper we present the results of Molflow+ simulations of several setups of the vacuum system for MAMBO that differ in number of pumps, pumping speed and diameter of the pumping ports that are connected to the DN40 beam pipe.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK032

About •

Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 24 June 2022

Cite •

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

THPOTK034

Vacuum System Performance of the 3 GeV Electron Storage Ring at MAX IV Laboratory

2836

M.J. Grabski, E. Al-Dmour, S.M. Scolari
MAX IV Laboratory, Lund University, Lund, Sweden

The 3 GeV electron storage ring at MAX IV laboratory is the first synchrotron light source with compact multi-bend achromat (MBA) magnet lattice to achieve ultra-low emittance. The vacuum system of the accelerator is fully coated with non-evaporable getter (NEG) thin film to ensure low gas density. The storage ring started commissioning in August 2015 and currently delivers photon beams from insertion devices (IDs) to 9 beamlines that are in user operation or commissioning. After over 6 years of operation, the NEG coated vacuum system continues to be reliable, is conditioning well and do not pose any limitation to the accelerator operation. The average dynamic pressure is lower than the design value (below 3·10^-10 mbar) and is reducing with the accumulated beam dose. The vacuum beam lifetime is greater than 39 Ah, and the total beam lifetime is above the design value of 5 Ah - thus is not limited by the residual gas density. Several successful interventions to install new vacuum components were performed on few achromats in the storage ring during shutdowns. Some of them were done utilizing purified neon gas to vent the vacuum system, thus avoiding the need of re-activation of the NEG coating and saving intervention time without compromising the storage ring performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK034

About •

Received ※ 08 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 28 June 2022

Cite •

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

THPOTK035

Thermo-Mechanical Modeling and Thermal Performance Analysis of Beam Vacuum Line Interconnections and Cold Warm Transitions in HL-LHC Long Straight Section Magnets

2839

J. Harray, C. Garion, V. Petit
CERN, Meyrin, Switzerland

The HL-LHC upgrade, aiming at increasing the LHC levelled luminosity by factor of five, relies on new superconducting magnets requiring a new beam vacuum system. Along with the challenges related to magnet design, the beam optic configuration exposes this new equipment to stringent conditions for vacuum and cryogenic performance. Both cold-warm transitions and magnet interconnections appear to be delicate components that are crucial for the thermal heat transfer between diverse subsystems. The proposed study aims at assessing the heat loads to the cryogenic system and the temperature fields in the vacuum system. A nonlinear static thermal analysis is first performed. A thermo-mechanical approach is developed to capture additional thermal resistance arising from contact between components and their behaviour during cool-down. The system is then studied under dynamic operations when beams are circulating and colliding. A thorough analysis of beam-induced heat loads under ultimate conditions highlights the different relevant contributions. Finally, the transient response of the systems is computed to assess thermal time constants.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK035

About •

Received ※ 08 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 27 June 2022 — Issue date ※ 29 June 2022

Cite •

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

THPOTK036

Determination of Pumping and Dynamic Vacuum Properties of Conductive Quaternary Alloy of TiZrVAg Non-Evaporable Getter.

2843

R. Valizadeh, A.N. Hannah, O.B. Malyshev
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
G.Y. Hsiung
NSRRC, Hsinchu, Taiwan
J.M. O’Callaghan Castella
Universitat Politécnica de Catalunya, Barcelona, Spain
M. Pont, N.D. Tagdulang
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Non Evaporable Getter (NEG) coating has been employed extensively in the particle accelerator especially where the vacuum conductance of the vessel is severely restricted and ultra-high vacuum condition is required. NEG coating will significantly reduce the outgassing rate and provides active pumping surface for H₂, CO and CO₂. In addition, it has been proven that NEG coated surfaces have a very low secondary electron yield, as well as low photon and electron stimulated desorption yields. However, the existing NEG film increases the RF surface resistance of the beam pipe. In order to increase NEG coating conductivity, at ASTeC, in the past several years, the alternative NEG com-position have been studied by adding more conductive element such as Cu, Au, Al and Ag. In this study, we report on the photon stimulated desorption, activation temperature and surface resistance from room temperature to cryogenic temperature for a new NEG quaternary alloy of TiVZrAg as function of the film composition.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK036

About •

Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022

Cite •

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

THPOTK037

Measurement of the Photon Stimulated Desorption for Various Vacuum Tubes at a Beam Line of TLS

2847

G.Y. Hsiung, C.M. Cheng
NSRRC, Hsinchu, Taiwan
R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

For most light sources, the synchrotron radiation (SR) hit on the beam ducts or absorbers results in higher pressure rise and the consequent higher radiation level through the commissioning stage. Various surface treatments, e.g. chemical cleaning, oil-free machining, NEG-coating, etc., for the beam ducts or absorbers have been developed worldwide for mitigating the yield of Photon Stimulated Desorption (PSD). A beam line, BL19B, of 1.5 GeV Taiwan Light Source (TLS) has been modified to measure the PSD-yield of the vacuum tubes. The white light of BL19B covers the critical length at 2.14 keV is suitable for generating higher yield of the photo-electrons (PEY) and the consequent PSD-yield to be measured can be resolved wide range of 10^-2 ~ 10^-7 molecules/photon. The PSD-outgas, measured by RGA, contains the typical H₂, CO, CO₂, hydrocarbons, and Kr from NEG-coating, alcohol from ethanol machined surface, in some cases. The effect of beam-cleaning reflects the PSD-molecules generated from the SR-irradiated surface. The comparison of the PSD for the various vacuum tubes will be described in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK037

About •

Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 08 July 2022

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

THPOTK038

Electron Stimulated Desorption From Titanium Tube

2850

O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Titanium is one of material that used for production of accelerator vacuum chamber and components. In this paper we report the results of vacuum properties evaluation measurements of titanium vacuum chamber. The sample was produced from 40-mm inner diameter tube made of titanium and equipped with CF40 flanges at both ends. The electron stimulated desorption (ESD) was measured after 24-h bakeout to 80, 150, 180 and 250 oC. H₂ and CO initial sticking probabilities were measured after bakeout before the ESD measurements. After ESD measurements, the initial H₂ and CO sticking probabilities were measured again together with CO sorption capacity. These measurements provide the results for ESD as a function of electron dose baked to different temperatures and demonstrate the efficiency of electron stimulated activation of titanium vacuum chamber.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK038

About •

Received ※ 25 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022

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

THPOTK039

The Effect of Activation Duration on the Performance of Non-Evaporable Getter Coatings

2854

E.A. Marshall, O.B. Malyshev, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Non-evaporable getter (NEG) coatings can be activated at temperatures as low as 140°C. However, better pumping properties are achieved using higher temperatures, between 150-300 °C. This paper investigates whether using an increased activation duration can improve the NEG properties obtained using lower activation temperatures, and so decrease the energy and temperature requirement. This could allow a greater range of materials to be used in particle accelerator systems. Our findings have shown that increasing activation duration from 24 hrs to 1 week at 160 °C produces an improvement in the NEG pumping properties.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK039

About •

Received ※ 01 June 2022 — Accepted ※ 10 June 2022 — Issue date ※ 17 June 2022

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