Paper | Title | Page |
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MOPAB031 | Development and Operation of Vacuum System for Rapid Cycling Synchrotron to Target Beam Transfer Line of China Spallation Neutron Source | 145 |
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China Spallation Neutron Source (CSNS) is a major scientific project during the National Eleventh Five-Year Plan. It consists of a negative hydrogen ion linear accelerator, a rapid cycling synchrotron ( RCS), a linac to RCS beam transfer line (LRBT), an RCS to target beam transfer line (RTBT), and a target station. As an important part of CSNS, the RTBT connects the rapid cycling synchrotron and the target window. This paper described the design requirements, technical solutions, and operating conditions of the vacuum system for the CSNS RCS to target beam transfer line. In addition, the fast valve protection system and its verification results were also expounded. The CSNS has been in operation for over three years, during this period, the beam power has been gradually improved from 10KW to 100KW, and the vacuum system for RTBT has been operating stably. | ||
Poster MOPAB031 [0.581 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB031 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 24 May 2021 issue date ※ 25 August 2021 | |
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MOPAB360 | Anomalous Skin Effect Study of Normal Conducting Film | 1119 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. For the radiofrequency (RF) applications of normal conducting film with large mean free path at high frequency and low temperature, the anomalous skin effect differs considerably from the normal skin effect with field decaying exponentially in the film. Starting from the relationship between the current and the electric field (E field) in the film, the amplitude of E field along the film depth is calculated, and is found to be non-monotonic. The surface impedance is found to have a minimum value at certain film thickness. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB360 | |
About • | paper received ※ 17 May 2021 paper accepted ※ 25 June 2021 issue date ※ 17 August 2021 | |
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TUXC04 |
Electron Desorption From Porous Materials of Interest for Future Accelerators | |
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Funding: ARYA project funded by INFN Scientific National Committee 5 Laser ablated Cu surfaces (LASE) have been proposed to mitigate electron cloud phenomena due to their porous structure*. When such surfaces are used as cryogenic components in accelerators, they will undergo thermal fluctuation, photon, and e-irradiation. A rigorous evaluation of their overall behavior in such vacuum conditions is clearly required. Our studies on thermal desorption of gas from LASE have shown that the morphology gives rise to a vaster and higher desorption temperature (T) with respect to what has been observed from a flat surface**. This implies that gas desorption from LASE will occur in an unexpected T range, but also that cryosorbed gas will be on those surfaces at temperatures and quantities very different from what is expected to occur on flat surfaces. This gas can participate in other desorption mechanisms, such as e-desorption. Here we report some measurements of e-desorption yield from such LASE treated surfaces at low T. Such results can be useful to predict the gas quantity finally delivered in accelerators’ cryogenic vacuum from a porous surface under e-irradiation. * R. Valizadeh et al. , Appl. Surf. Sci. 404, 370 (2017) ** L. Spallino et al. , Phys. Rev.. Accel. Beams 23, 063201 (2020) |
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TUPAB260 | A Beam Screen to Prepare the RHIC Vacuum Chamber for EIC Hadron Beams: Conceptual Design and Requirements | 2066 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy. The Electon Ion Collider (EIC) hadron ring will use the existing Relativistic Heavy Ion Collider storage rings, including the superconducting magnet arcs. The vacuum chambers in the superconducting magnets and the cold mass interconnects were not designed for EIC beams and so must be updated to reduce its resistive-wall heating and to suppress electron clouds. To do so without compromising the EIC luminosity goal, a stainless steel beam screen with co-laminated copper and a thin layer of amorphous carbon will be installed. This paper describes the main requirements that our solution for the hadron ring vacuum chamber needs to satisfy, including impedance, aperture limitations, vacuum, thermal and structural stability, mechanical design, installation and operation. The conceptual design of the beam screen currently under development is introduced. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB260 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 12 August 2021 | |
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TUPAB391 | Cryopanels in the Room Temperature Heavy Ion Synchrotron SIS18 | 2435 |
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The FAIR complex at the GSI Helmholtzzentrum will generate heavy ion beams of ultimate intensities. To achieve this goal, medium charge states have to be used. However, the probability for charge exchange in collisions with residual gas particles of such ions is much higher than for higher charge states. In order to lower the residual gas density to extreme high vacuum conditions, 65% of the circumference of SIS18 are already coated with NEG, which provides high and distributed pumping speed. Nevertheless, nobel and nobel-like components, which have very high ionization cross sections, do not get pumped by this coating. A cryogenic environment at moderate temperatures, i.e. at 50-80K, provides high pumping speed for all heavy residual gas particles. The only typical residual gas species, that cannot be pumped at this temperature is hydrogen. With an additional NEG coating the pumping will be optimized for all residual gas particles. The installation of cryogenic surfaces in the existing room temperature synchrotron SIS18 at GSI has been investigated. A prototype quadrupole chamber with cryogenic surfaces, first measurements, and simulations of the adapted accelerator are presented. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB391 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 31 August 2021 issue date ※ 25 August 2021 | |
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TUPAB392 | Conceptual Design of the Vacuum System for the Future Circular Collider FCC-ee Main Rings | 2438 |
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The Future Circular Collider study program comprises several machine concepts for the future of high-energy particle physics. Among them there is a twin-ring e−e+ collider capable to run at beam energies between 45.6 and 182.5 GeV, i.e. the energies corresponding to the resonances of the Z, W, H bosons and the top quark. The conceptual design of the two 100-km rings has advanced to what is believed to be a working solution, i.e. capability to deal with low-energy (45.6 GeV) high-current (1390 mA) version as well as the high-energy (182.5 GeV) low-current (5.4 mA) one, with intermediate energy and current steps for the other 2 resonances. The limit for all of the versions is given by the 50 MW/beam allotted to the synchrotron radiation (SR) losses. The paper will outline the main beam/machine parameters, the vacuum requirements, and the choices made concerning the vacuum chamber geometry, material, surface treatments, pumping system, and the related pressure profiles. The location of lumped SR photon absorbers for the generic arc cell has been determined. An outline of the studies needed and envisaged for the near future will also be given. | ||
Poster TUPAB392 [3.036 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB392 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 25 August 2021 | |
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TUPAB393 | Study of Remote Helium Mass Spectrometer Leak Detection in Accelerator | 2441 |
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In order to solve the problem that the vacuum system of the accelerator can’t be close to the operation for a long time, a long-distance helium mass spectrometer leak detection system is explored by studying the structure of the conventional round tube vacuum box of the vacuum system, which integrates the online vacuum leak detection, defect diagnosis and process design, improves the digital operation, realizes the accurate and effective detection of the leak location range and leak rate, and provides the technology for the remote leak detection of the vacuum system. Support. | ||
Poster TUPAB393 [0.666 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB393 | |
About • | paper received ※ 13 May 2021 paper accepted ※ 31 May 2021 issue date ※ 10 August 2021 | |
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TUPAB395 | Vacuum System Models for Minerva Linac Design | 2443 |
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The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in a 100 MW Accelerator Driven System (ADS) by building a new flexible irradiation complex at Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton current of 4 mA in continuous wave operation, with an additional requirement for exceptional reliability. Supported by SCK•CEN and the Belgian federal government the project has entered in its phase I: this includes the development and the construction of the linac first part, up to 100 MeV. We here review the MINERVA linac vacuum system modelling studies that enabled to validate the choice of materials and vacuum equipment. The strengths and weaknesses of the vacuum design, highlighted by the models, will be discussed as well as the required improvements. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB395 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 01 June 2021 issue date ※ 28 August 2021 | |
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TUPAB396 | The Thermal Outgassing Rate of Materials Used in Vacuum Systems | 2447 |
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There are many rarely used materials in vacuum systems that are poorly investigated in terms of vacuum properties. For example, phosphors, scintillating materials, ferrites, various adhesives, etc. In addition, new organic materials are being developed with mechanical properties similar to those of conventional steel. The use of such materials is very promising in vacuum technology. This article presents the thermal degassing performance of several rarely used materials and promising materials for vacuum applications. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB396 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 31 August 2021 issue date ※ 20 August 2021 | |
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TUPAB398 | Vacuum Issues with Argon Gas in the LANSCE Accelerator | 2450 |
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Funding: US DOE NNSA In the Los Alamos Neutron Science Center (LANSCE) accelerator, there are about 220 500-L/s ion pumps running all the time. The oldest pumps recorded in the current system were installed in 1983. All the ion pumps are diode type ion pumps. In 2017, we started to suffer from ion pumps trips in an accelerator module 15 (M15) that includes 3 500-L/s ion pumps and they caused beam down times of the accelerator during the production run cycles. This paper reports the details of these trips, how we found it was argon gas that was causing the trips and how we tried to reduce it. |
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Poster TUPAB398 [0.817 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB398 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 01 June 2021 issue date ※ 28 August 2021 | |
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TUPAB399 | RF Characterisation of New Coatings for Future Circular Collider Beam Screens | 2453 |
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For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9 T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB399 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021 | |
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TUPAB400 | Manufacturing of Ceramic Vacuum Chambers for Sirius On-Axis Kicker | 2457 |
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Ceramic vacuum chambers were produced by LNLS for the Sirius kickers. Alumina tubes with an elliptical inner shape of 9.5 mm (V) x 29 mm (H) and 500 mm long were successfully manufactured by a Brazilian company. Metallic F136 titanium flanges were brazed to Nb inserts using Ag-58.5Cu-31.5Pd wt% alloy, these inserts were brazed to the ceramic using Ag-26.7Cu-4.5Ti wt% active filler metal. A titanium film was coated inside the chamber using argon plasma by RF Magnetron Sputtering technique. Samples have been investigated by Scanning Electron Microscopy (SEM) to measure film thickness along the inner section of the tube, coating morphology, chemical composition and homogeneity. The total electrical resistance of the tube was also monitored during the sputtering process to achieve the desired value (0.2 ohms/square). In this contribution, we present the results of an On-Axis kicker manufacturing process developed by LNLS. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB400 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 29 August 2021 | |
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TUPAB401 | Mechanical Design, Fabrication and Characterization of Electron Beam Position Monitors for Sirius | 2461 |
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Beam Position Monitors were designed and manufactured to meet Sirius operation requirements. Final dimensional accuracy and stability of the BPM were achieved by careful specification of its components’ manufacturing tolerances and materials. AISI-305 Stainless Steel was used for the BPM support fabrication due to magnetic and thermal expansion constraints. High purity molybdenum for the electrode pin and Ti6Al4V F136 G23 alloy for housing was used to manufacture the sensor components for their thermal characteristics. The electrical insulator was made of high alumina. The materials were joined by an active metal brazing process using 0,01mm accurate fixtures. The brazed sensors were subjected to dimensional, mechanical, and metallurgical testing, as well as leak detection and optical microscopy inspection at each stage. The sensors were joined in Ti6Al4V F136 BPM bodies using TIG welding. Dimensional sorting was used to choose groups of sensors-to-body, and body-to-support pairs during the final assembly. 160 BPMs are currently in operation on Sirius storage ring. In this contribution, we present the results of BPM manufacturing and testing processes developed for Sirius. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB401 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 31 May 2021 issue date ※ 29 August 2021 | |
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WEPAB333 | Installation and Commissioning of the Sirius Vacuum System | 3455 |
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The installation of the Sirius accelerators was completed in 2019. The vacuum installation of the booster took place in October 2018. The booster vacuum chambers were baked-out ex-situ and the vacuum pumps, gauges and valves were assembled prior to the installation in the tunnel. The vacuum installation of the storage ring took place from May to August 2019. The vacuum system of the storage ring is based on fully NEG-coated chambers and each sector was baked-out in-situ for NEG activation. The average static pressure in the booster is in the range of low 10-9 mbar. In the storage ring, 95% of the pressures are in 10-11 mbar range and 5% are in 10-10 mbar range. The first beam was stored in the storage ring in December 2019. The vacuum system has been performing well, and an effective beam cleaning effect has been observed for the NEG-coated chambers. At a beam dose of 70 A-h, the storage ring already achieved the design normalized average dynamic pressure of 3x10 12 mbar/mA. A summary of the installation and the commissioning status of the vacuum system will be presented. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB333 | |
About • | paper received ※ 20 May 2021 paper accepted ※ 14 June 2021 issue date ※ 22 August 2021 | |
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WEPAB334 | Development of Diffusion Bonded Joints of AA6061 Aluminum Alloy to AISI 316LN Stainless Steel for Sirius Planar Undulators | 3459 |
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LNLS has been commissioning Sirius, a 4th-generation synchrotron light source. The commissioning of the beamlines has been mainly done by using planar undulator, which uses in-house built aluminum vacuum chambers with ultra-high vacuum tight bimetallic flanges. In order to manufacture these flanges, diffusion bonded joints of AA6061 aluminum alloy to AISI 316LN stainless steel were developed. Diffusion bonding was carried out at 400-500°C for 45-60 min, applying a load of 9.8MPa in a vacuum furnace. Also, the surface preparation for Al and SS was investigated. SEM observation revealed that an 1-3 µm reaction layer was formed at the AA6061/Ni-plated interface. The intermetallic compound Al3Ni was identified in the reaction layer. The obtained Al/SS joints showed mean ultimate strength of 84 MPa, with the fracture occurring in the Al/reaction layer interface. Bake-out cycles followed by leak tests were carried out to validate the process and approve their use on the planar undulator vacuum chambers. Two undulators with Al/SS flanges have been installed and are under operation in the storage ring. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB334 | |
About • | paper received ※ 17 May 2021 paper accepted ※ 17 June 2021 issue date ※ 31 August 2021 | |
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WEPAB335 | Aluminum Vacuum Chamber for the Sirius DELTA 52 Undulator | 3463 |
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Sirius is a 3 GeV fourth generation synchrotron light source under commissioning by the Brazilian Synchrotron Light Laboratory (LNLS). Delta Undulators with magnet vertical aperture of 13.6 mm, and period of 52.5 mm will be used for the generation of soft X rays to photoemission spectroscopy and X ray absorption experiments. Extruded aluminum vacuum chambers having small vertical aperture of 7.6 mm and horizontal aperture of 13 mm is proposed. This paper details the design and manufacturing processes of a complete chamber. Challenges regarding the TIG welding for aluminum and NEG coating for small aperture chambers will also be presented. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB335 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 19 July 2021 issue date ※ 20 August 2021 | |
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WEPAB336 | Aluminum Vacuum Chamber for the Sirius Commissioning Undulators | 3467 |
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Sirius is a 3 GeV fourth generation light source under commissioning by the Brazilian Synchrotron Light Laboratory (LNLS). Compact Linear Polarizing Undulators with magnet vertical aperture of 8 mm have been used for the commissioning of some beam lines. Extruded aluminum vacuum chambers having small vertical aperture of 6 mm and horizontal aperture of 40 mm, were built. This paper details the design and manufacturing processes of a complete chamber and its installation procedure at the storage ring. Challenges regarding the precision machining of the 0.5 mm wall thickness, TIG welding for aluminum, NEG coating for small apertures will also be presented. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB336 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 25 August 2021 issue date ※ 20 August 2021 | |
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WEPAB337 | Some Methods of Making Titanium Vacuum Chamber Act as Getter Pump for UHV/XHV | 3471 |
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Funding: JSPS KAKENHI Grant Number JP18K11925 The non-evaporable getter (NEG) coating has been developed in CERN to make a beam pipe act as a distributed vacuum pump by coating the getter materials with the ability to adsorb/absorb gas molecules on the beam pipe surface. The NEG coating materials used in the LHC are alloys of titanium, zirconium, and vanadium. In high-power beam accelerators, titanium has been used as the beam pipe chamber material due to its low radio activation characteristics. The ordinal titanium surface has no getter function because it is covered with a titanium oxide film. The new technique, which removes the titanium-oxide surface by some methods, such as baking or sputtering, has been investigated. The dependence of the surface oxide film and the getter characteristics on the baking temperature have been measured. Also, by sputtering the inner surface of the titanium chamber, clear evidence that shows the chamber acts as a vacuum pump has been obtained. Furthermore, the NEG coating on the pure titanium surface can suppress the rapid decrease of the sticking probability by the repeated air purge and reactivation. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB337 | |
About • | paper received ※ 14 May 2021 paper accepted ※ 25 June 2021 issue date ※ 19 August 2021 | |
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WEPAB338 | Amorphous Carbon Coating in SPS | 3475 |
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Within the LHC Injector Upgrade (LIU) project, the Super Proton Synchrotron (SPS) needs to be upgraded to inject into the LHC higher intensity and brighter 25-ns bunch spaced beams. To mitigate the Electron Multipacting (E.M.) phenomenon, a well-known limiting factor for high-intensity positively charged beams, CERN developed carbon coatings with a low Secondary Electron Yield (SEY). During the 2016 & 2017 year-end technical stops, such coatings were deposited on the inner wall of the vacuum chambers of some SPS quadrupole and dipole magnets by a dedicated in-situ setup. A much larger scale deployment was implemented during the Long Shutdown 2 (2019-2020) to coat all beam pipes of focussing quadrupoles (QF) and their adjacent short straight sections. In this contribution, we remind the motivation of the project, and present the results and the quality control of the carbon coating campaign during the latter phase of implementation. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB338 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 16 June 2021 issue date ※ 13 August 2021 | |
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WEPAB339 | Beam-Induced Surface Modification of the LHC Beam Screens: The Reason for the High Heat Load in Some LHC Arcs? | 3479 |
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All over Run 2, the LHC beam-induced heat load exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpectedly high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. During the Long Shutdown 2, the beam screens of a low and a high heat load dipole were extracted. Their inner copper surface was analysed in the laboratory to compare their SEY and surface composition. While findings on the low heat load beam screens are compatible with expectations from laboratory studies of copper conditioning and deconditioning mechanisms, an extremely low carbon amount and the presence of CuO (non-native surface oxide) are observed on the high heat-load beam screens. The azimuthal distribution of CuO correlates with the density and energy of electron impingement. Such chemical modifications increase the SEY and inhibit the full conditioning of affected surfaces. This work shows a direct correlation between the abnormal LHC heat load and the surface properties of its beam screens, opening the door to the development of curative solutions to overcome this critical limitation. | ||
Poster WEPAB339 [2.247 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB339 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 16 August 2021 | |
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WEPAB340 | Pressure Simulations for the EIC Interaction Region | 3483 |
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Background detector rates in the Electron Ion Collider depend in part on the pressure in the interaction region. Materials choice, synchrotron radiation induced desorption, conditioning time and pumping configuration all affect the pressure in the system. Simulations of the region using Synrad and Molflow+ coupled simulation codes will be presented for various configruations and conditioning times. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB340 | |
About • | paper received ※ 18 May 2021 paper accepted ※ 20 July 2021 issue date ※ 11 August 2021 | |
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THPAB290 | Evolution of the LHC Beam Screen Surface Conditioning Upon Electron Irradiation | 4370 |
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For the vacuum scientists and the accelerator community, finding solutions to mitigate pressure rises induced by electron, photon, and ion desorption, and also beam instabilities induced by ion and electron clouds is a major issue. Moreover, it is worth noting that the OFE copper beam screen of the LHC is initially cleaned with standard industrial processes, leading to residual chemical contamination. Along the time, changes in the surface chemistry of vacuum chambers are observed during beam operations, leading to modifications of outgassing rates, stimulated desorption processes, and secondary emission yields (SEY). The impact of ions on molecule desorption and electron production was investigated to identify their influence on the global pressure rises and to quantify the ion conditioning effect on copper surfaces: (i) SEY evolution was measured to understand the changes of surface conditioning upon particle irradiation; (ii) 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 surface chemistry and the conditioning phenomenon will be discussed. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB290 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 14 July 2021 issue date ※ 10 August 2021 | |
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THPAB291 | DYVACS (DYnamic VACuum Simulation) Code: Gas Density Profiles in Presence of Electron Cloud in the LHC | 4373 |
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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 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 and the evolution of the electronic density related to the electron cloud build-up. 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 induced desorption. The pressure evolution computed with DYVACS reproduces with good accuracy the experimental pressure recorded in the VPS beam pipes sector*** of the LHC from the proton beam injection to the stable beam period. Additionally, DYVACS can also be used as a predictive tool to compute the pressure evolution in the beam pipes for Future Circular Colliders (FCC-hh or -ee).
* A. Rossi, Tech. Report, LHC Project Note 341 ** T. Demma et al Phys. Rev. Acceler. and Beams 10, 114401 (2007) *** B. Henrist et al, Proc. IPAC2014, Dresden |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB291 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 02 August 2021 issue date ※ 31 August 2021 | |
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THPAB292 | Dynamic Pressure in the LHC: Detection of Ions Induced by Ionization of Residual Gas by the Proton Beam and by the Electron-Cloud | 4377 |
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Ultra-High Vacuum is an essential requirement to achieve design performances and high luminosities in high-energy particle colliders. Consequently, the understanding of the dynamic pressure evolution during accelerator operation is fundamental to provide solutions to mitigate pressure rises induced by multiple effects leading to beam instabilities. For the LHC, the appearance of instabilities may be due to the succession of several phenomena: (i) the induced desorption of gases adsorbed on the surfaces leading to pressure rises; (ii) the creation of secondary particles (ions, electrons); (iii) the production of the so-called Electron Cloud build-up by multipacting effect. This work aims to investigate some fundamental phenomena which drive the dynamic pressure in the LHC, namely the effects induced by electrons and ions interacting with the copper surface of the beam screens. Electron and ion currents, as well as pressure, were recorded in situ in the Vacuum Pilot Sector (VPS*) located on the LHC ring during the RUN II. By analyzing the results, more ions than expected were detected and the interplay between electrons, ions, and pressure changes was investigated.
* The LHC Vacuum Pilot-Sector Project, B. Henrist, V. Baglin, G. Bregliozzi, and P. Chiggiato, CERN, Geneva, Switzerland, Proceedings of IPAC2014, Dresden, Germany |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB292 | |
About • | paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 27 August 2021 | |
Export • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |
THPAB341 | TiN Metalizing and Coating for Multi-Megawatt RF Vacuum Windows | 4457 |
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Coatings on microwave windows and high-voltage ceramics are required to eliminate secondary electron emission (SEE), which initiates multipactoring discharge causing local heating and ceramic failures due to cracking and loss of vacuum. The region surrounding the triple junction (ceramic+metal+vacuum) is the primary source of free electrons and in microwave windows and high-voltage ceramics. This region is located at the metalizing and braze joint of the ceramic support structure making the vacuum seal. On very large microwave windows typically at low frequencies, this critical region is difficult to coat by the traditional techniques of sputter coating anti-multipactoring titanium nitride or other materials. The novel processes proposed here include a means for applying and controlling the thickness of titanium nitride both in the metallizing (controlling the source) and on the surface of the window, eliminating SEE and the multipactoring discharge. | ||
Poster THPAB341 [0.845 MB] | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB341 | |
About • | paper received ※ 23 May 2021 paper accepted ※ 21 July 2021 issue date ※ 01 September 2021 | |
Export • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |