Keyword: background
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MOPMF085 Beam-gas Background Characterization in the FCC-ee IR simulation, scattering, vacuum, optics 322

• M. Boscolo, O.R. Blanco-García
INFN/LNF, Frascati (Roma), Italy
• H. Burkhardt, R. Kersevan, M. Lueckhof
CERN, Geneva, Switzerland
• F. Collamati
INFN-Roma1, Rome, Italy

The MDISim toolkit is used to evaluate and characterize the beam-gas induced background in the FCC-ee Interaction Region. MDISim allows a full characterization of this beam background source with the locations where the beam-gas scattering occurs as well as the loss points, as a function of different vacuum conditions and composition, for the nominal optics and parameters. Detailed pressure distribution profiles have been obtained running coupled synchrotron radiation and molecular flow montecarlo codes, as an input to the GEANT4 calculations. The particles hitting the pipe in the IR can be tracked in the detectors with a full Geant-4 simulation. Semi-analytic estimates for the expected rates and lifetime are also performed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF085
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MOPML012 Special Collimation System Configuration for the LHC High-Beta Runs collimation, simulation, detector, experiment 418

• H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom
• R. Bruce, H. Burkhardt, M. Deile, S. Jakobsen, A. Mereghetti, S. Redaelli
CERN, Geneva, Switzerland

Special LHC high-beta optics is required for the forward physics program of TOTEM and ATLAS-ALFA. In this configuration, the beam is de-squeezed (the \beta-function at the collision point is increased) in order to minimize the divergence for measurements at very small scattering angles. In these low beam intensity runs, it is important to place the Roman Pots (RPs) as close as possible to the beam, which demands special collimator settings. During Run I, a significant amount of background was observed in the forward detectors due to particles outscattered from the primary collimator. During Run II, a different collimation configuration was used where a tungsten collimator was used as primary collimator instead of the usual one made of carbon. Using this configuration, a significant reduction of the background at the RPs was observed. In this paper we present a description of the new collimator configuration and the results obtained during the high-beta run carried out in 2016.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML012
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• S. Bai, J. Gao, H. Geng, D. Wang, Y. Wang, C.H. Yu, Y. Zhang
IHEP, Beijing, People's Republic of China

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and Beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector.
Slides TUYGBD4 [0.796 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBD4
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WEPAL075 Time-Resolved Transverse Beam Profile Measurements with a Rest Gas Ionisation Profile Monitor Based on Hybrid Pixel Detectors electron, detector, proton, site 2361

• S. Levasseur, S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
• W. Bertsche, H. Sandberg
UMAN, Manchester, United Kingdom
• D. Bodart, A. Huschauer, G. Schneider, J.W. Storey, R. Veness
CERN, Geneva, Switzerland
• M. Sapinski
• K. Satou
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

A novel rest gas ionisation profile monitor which aims to provide continuous, bunch-by-bunch and turn-by-turn measurement of the transverse beam profile has recently been in- stalled in the CERN Proton Synchrotron (PS) as part of the LHC Injector Upgrade (LIU) project. The instrument consists of an electric drift field to transport ionisation electrons produced by beam-gas interaction onto a measurement plane, and a magnetic field to maintain the transverse position of the ionisation electrons. The electron detector located at the measurement plane is based on four in-vacuum hybrid pixel detectors. The detectors record the position, time and energy of single ionisation electrons with unprecedented precision compared to traditional MCP based techniques. Continuous transverse beam profile measurements for LHC-type beams in the PS will be presented, demonstrating the unique capabilities of the instrument to provide new insights into beam dynamics throughout the acceleration cycle.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL075
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WEPML008 Tuner Testing of a Dressed 3.9 GHz Cavity for LCLS-II at Fermilab cavity, SRF, operation, FEL 2690

• J.P. Holzbauer, S. Aderhold, T.N. Khabiboulline, Y.M. Pischalnikov, W. Schappert, J.C. Yun
Fermilab, Batavia, Illinois, USA
• C. Contreras-Martinez
FRIB, East Lansing, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Fermilab is responsible for the design of the 3.9 GHz cryomodule for LCLS-II. Integrated acceptance testing of a dressed 3.9 GHz cavity for the LCLS-II project has been done at the Fermilab Horizontal Test Stand. This test included a slim blade tuner (based on INFN & XFEL designs) with integrated piezoelectric fast/fine tuner. This paper will present results of the mechanical setup, cold testing, and cold function of this tuner including fast and slow tuner range, sensitivity, and hysteresis.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML008
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WEPML072 Gas Permeability Measurement of Graphene Films vacuum, experiment, neutron, detector 2856

• P.C. Wang, X. Sun
DNSC, Dongguan, People's Republic of China
• Liu. S. Liu
Institute of High Energy Physics (IHEP), People's Republic of China
• C. Meng, H. Wang, D.H. Zhu
IHEP, Beijing, People's Republic of China

Graphene has extremely high strength and thermal conductivity, which can possibly be used for high-power beam window in accelerator. In this paper, gas permeabilities of different graphene films have been measured by the permeation measurement facility. According to the results, the possibility of the graphene-made beam windows will be discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML072
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WEPML073 Research on Magnetic Center Measurement of Quadrupole and Sextupole Using Vibrating Wire Alignment Technique in HEPS-TF sextupole, alignment, quadrupole, multipole 2860

• L. Wu, C. H. Li, H. Qu, H. Wang, X.L. Wang
IHEP, Beijing, People's Republic of China
• H.Y. Zhu
Institute of High Energy Physics (IHEP), People's Republic of China

In order to meet the extremely low emittance re-quirement, the magnets in the storage ring of High Energy Photon Source(HEPS) need to have a stable support and precise positioning. Vibrating wire align-ment technique can be used to pre-align the quadru-poles and sextupoles on one girder with high preci-sion. Research of vibrating wire alignment technique is one important project of HEPS Test Facility (HEPS-TF). In HEPS-TF, the key and difficult technologies of HEPS should be researched and developed. This paper introduces the principle of the vibrating wire align-ment technique and the measurement system in brief. The magnetic center measurement of quadrupole and sextupole using vibrating wire will be introduced in detail. It concludes the measurement procedure, mag-netic field distribution, measurement repeatability, sag correction and magnet adjustment measurement. The research of vibrating wire has get a better precision than the aim. The magnetic center measurement preci-sion reach to ±3μm and the magnet adjustment error is less than 6μm.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPML073
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THYGBE4 Early Phase 2 Results of LumiBelle2 for the SuperKEKB Electron Ring luminosity, simulation, electron, photon 2934

• S. Di Carlo, P. Bambade, D. Jehanno, V. Kubytskyi, C.G. Pang, Y. Peinaud, C. Rimbault
LAL, Orsay, France

We report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors.
Slides THYGBE4 [3.096 MB]
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE4
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THPAF047 Measurements and Impact of Stray Fields on the 380 GeV Design of CLIC site, emittance, dipole, collider 3072

• C.G. Gohil, M.C.L. Buzio, E. Marín, D. Schulte
CERN, Geneva, Switzerland
• P. Burrows
JAI, Oxford, United Kingdom

Previous studies of the 3 TeV Compact Linear Collider (CLIC) design have shown a sensitivity to external dynamic magnetic fields (stray fields) on the nanoTesla level. In this paper the obtained tolerances for stray fields in the 380 GeV CLIC design are presented. In order to determine potential stray field sources, a measurement sensor has been acquired and used to investigate the magnetic contamination from technical equipment. The collected measurements, as well as details of the sensor, are discussed.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF047
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THPAK139 Lost Muon Studies for the Muon g-2 Experiment at Fermilab positron, experiment, storage-ring, resonance 3573

• S. Ganguly, K. T. Pitts
University of Illinois at Urbana-Champaign, Urbana, USA
• J.D. Crnkovic
BNL, Upton, Long Island, New York, USA
• C. C. Polly
Fermilab, Batavia, Illinois, USA

The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment aµ with an unprecedented precision of 140 parts per billion (ppb), a four-fold improvement over the 540~ppb precision obtained by the BNL Muon g-2 Experiment. This study presents preliminary work on estimating the muon losses by using double coincidences in the calorimeters.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK139
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THPAL076 Experimental Methods for the Assessment of NEG Pumps Working in Dust-Sensitive Environments vacuum, cavity, SRF, experiment 3828

• T. Porcelli, E. Maccallini, P. Manini, M. Mura, M.F. Urbano
SAES Getters S.p.A., Lainate, Italy

NEG pumps have been widely adopted by many accelerator facilities since decades. However, their use in dust-sensitive areas - such as superconductive radio frequency (SRF) cavities - has always been limited by concerns about accidental dust emission, which could induce detrimental field emission. As future machines will necessarily rely on highly-efficient SRF cavities, able to supply very high accelerating gradients, requirements in terms of particle release from vacuum components (e.g., pumps and valves) are becoming more and more stringent. At the same time, achieving stable ultra-high vacuum conditions is crucial, as condensed residual gas might also be a potential source of field emission. At present, a unified standard procedure to assess dust generation and propagation along a machine is still missing and discussions are ongoing in the vacuum community. Recent experimental measurements demonstrated the compatibility of sintered NEG pumps with ultra-clean environments, due to their intrinsic very low dust release. In parallel, in-situ tests performed at different accelerator facilities showed absence of dust contamination from NEGs and no impact on cavities efficiency.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL076
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THPML002 Emittance Preservation in Plasma-Based Accelerators with Ion Motion emittance, plasma, wakefield, ECR 4654

• C. Benedetti, E. Esarey, W. Leemans, T.J. Mehrling, C.B. Schroeder
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. DOE under Contract No. DE-AC02-05CH11231.
In a plasma-accelerator-based linear collider, the density of matched, low-emittance, high-energy particle bunches required for collider applications can be orders of magnitude above the background ion density, leading to ion motion, perturbation of the focusing fields, and, hence, to beam emittance growth. By analyzing the response of the background ions to an ultrahigh density beam, analytical expressions, valid for non-relativistic ion motion, are obtained for the perturbed focusing wakefield. Initial beam distributions are derived that are equilibrium solutions, which require head-to-tail bunch shaping, enabling emittance preservation with ion motion.

DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML002
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THPML118 The AWAKE Electron Spectrometer proton, electron, plasma, radiation 4947

• F. Keeble, M. Cascella, J. A. Chappell, L.C. Deacon, S. Jolly, M. Wing
UCL, London, United Kingdom
• I. Gorgisyan, S. Mazzoni
CERN, Geneva, Switzerland
• P.L. Penna, M. Quattri
ESO, Garching bei Muenchen, Germany

The AWAKE experiment at CERN aims to use a proton driven plasma wakefield to accelerate electrons from 10–20 MeV up to GeV energies in a 10 m plasma cell. We present the design of the magnetic spectrometer which will measure the electron energy distribution. Results from the calibration of the spectrometer's scintillator and optical system are presented, along with a study of the backgrounds generated by the 400 GeV SPS proton beam.
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML118
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