IPAC2017 - List of Keywords (background)

Paper	Title	Other Keywords	Page
MOPAB065	Breit-Wheeler Scattering Events Produced by Two Interacting Compton Sources	photon, scattering, electron, laser	261
	I. Drebot, L. Serafini Istituto Nazionale di Fisica Nucleare, Milano, Italy D. Micieli, E. Tassi UNICAL, Arcavacata di Rende, Italy E. Milotti INFN-Trieste, Trieste, Italy V. Petrillo Universita' degli Studi di Milano & INFN, Milano, Italy
	We present the dimensioning of a photon-photon collider based on conventional Compton gamma sources for the observation of Breit-Wheeler pair production and QED gamma-gamma generation. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two primary gamma rays through Compton back-scattering with two high-energy lasers. Tuning the system energy above the Breit-Wheeler cross section threshold, a flux of secondary electrons and positrons is generated. The process is analyzed by start-to-end simulations. The Monte Carlo code 'Rate Of Scattering Events' (ROSE) has been developed ad hoc for the counting of the QED events. Realistic numbers of the secondary particles yield, referring to existing or approved set-ups, a discussion of the feasibility of the experiment and the evaluation of the background are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB065
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MOPAB098	Coronagraph Based Beam Halo Monitor Development for BERLinPro	electron, dipole, linac, scattering	355
	J.G. Hwang Kyungpook National University, Daegu, Republic of Korea J. Kuszynski HZB, Berlin, Germany
	For linac based high power electron machines, beam halo induced by nonlinear space charge force and scattering of trapped ions is one of the critical issues on a machine protection system. It causes additional radiation which can be a heat source on a cryogenic system as a result of uncontrolled beam losses. During the last decades, several instruments have been newly developed for measuring the beam halo distribution. The conceptual design and optimization of the coronagraph based halo monitor were performed to measure the beam halo which has ~ 10^-3 contrast to the beam core.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB098
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MOPAB112	Schottky Based Intensity Measurements and Errors Due to Statistical Fluctuations	antiproton, pick-up, instrumentation, diagnostics	385
	C. Carli, M.E. Angoletta, F. Caspers, O.R. Jones, F. Pedersen, J. Sanchez-Quesada, L. Søby CERN, Geneva, Switzerland
	The beam intensities at the Extra Low ENergy Antiproton ring ELENA are too low for standard beam current transformers and, thus, are measured with longitudinal Schottky diagnostics. This method is already successfully used at the Antiproton Decelerator since the commissioning of this machine. The fact that Schottky noise is a statistical phenomenon implies statistical errors of these measurements. Simple analytical formulas describing the statistical error to be expected as a function of the frequency spread of the band considered, the time resolution chosen and the background noise have been derived. On the one hand, low revolution harmonics and, in turn, frequency spread of the band analysed lead to large measurement errors as this situation corresponds to low momentum resolution of the resulting distribution describing the beam. At very large revolution harmonics and, thus, frequency spreads of the band analysed, the measurement error increases again due to additional contributions from the background noise.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB112
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MOPAB128	The Design of a Non-Destructive Single-Shot Longitudinal Bunch Profile Monitor using Smith-Purcell Radiation	radiation, detector, polarization, experiment	433
	H. Harrison, G. Doucas, I.V. Konoplev, A.J. Lancaster, H. Zhang JAI, Oxford, United Kingdom A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: This work was supported by the: the STFC UK, the Leverhulme Trust, the JAI (University of Oxford) and the Photon and Quantum Basic Research Coordinated Development (Japan). The conceptual design for a single-shot longitudinal bunch profile monitor using coherent Smith-Purcell radiation (cSPr) has recently been completed. The exploitation of the directionality and the polarization of cSPr to reduce the length of the monitor and to eliminate background radiation are discussed. The linear polarization of cSPr will be used to separate the signal from background radiation and experiments to test this design will be presented. Alongside the conceptual design an investigation to optimize the number of detection channels needed to produce high quality longitudinal bunch profile reconstructions has been carried out. It has been determined that the number of detection channels can be reduced compared to previous experiments if measurement uncertainty and background radiation are minimized effectively.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB128
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MOPIK091	Development of Real-Time Charge Integrator for the Irradiation Dose Measurement	real-time, target, Ethernet, controls	739
	H.G. Lim, Y.-S. Cho, Y.S. Hwang, M.H. Jung, K. R. Kim Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea
	Funding: This work has been supported through KOMAC (KOREA of Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT, and Future Planning). KOMAC (Korea of Multi-purpose Accelerator Complex, Gyeongju, Korea) has several kinds of facilities using proton beam or ion beam. The KOMAC has provided beam service to user group since 2013. For effective beam service, it is important that irradiation dose at a target should be supplied as much as user requires. To control the irradiation dose of target, a multi-channels charge integrator, Faraday cups, and a beam shutter are used. The amount of irradiation dose is calculated in real time by accumulative charge, which is represented to integration of induced current at each Faraday cup for the target. If the measurements reach to the set value (desired dose), the beam is automatically blocked by beam shutter. Thus, precise measurement of accumulative charge is required. For out purpose, two kinds of real-time charge integrators were implemented with different measuring ranges. In order to verify performance of the integrators, each device's linearity was evaluated after measuring accumulative charge corresponding to dc current. And their measurable range was determined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK091
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MOPVA041	Vertical Test Results on ESS Medium and High Beta Elliptical Cavity Prototypes Equipped with Helium Tank	cavity, linac, radiation, cryomodule	948
	E. Cenni CEA/IRFU, Gif-sur-Yvette, France P. Bosland, G. Devanz, F. Éozénou, X. Hanus, L. Maurice, F. Peauger, J. Plouin, D. Roudier, C. Servouin CEA/DSM/IRFU, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden
	The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA041
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TUOAB2	First Observation of the LHC Beam Halo Using a Synchrotron Radiation Coronagraph	simulation, synchrotron, radiation, photon	1244
	T.M. Mitsuhashi KEK, Ibaraki, Japan E. Bravin, F. Roncarolo, G. Trad CERN, Geneva, Switzerland
	A test coronagraph for the observation of beam halo has been installed in the Synchrotron radiation monitor line LHCB2 in 2015. This coronagraph is commissioned with LHC operation at 450GeV (injection energy). After some optical testing of the coronagraph with visible Synchrotron radiation in B2, we try to observe artificially-made beam halo. The beam halo of 10^-3 order of magnitude against the beam core is excited by the kicker of the transverse damper. We have succeeded to observe a diffraction noise free image of beam halo. The effect of beam collimator is also observed. Reduction of beam halo intensity was found nicely proportional to the simultaneously-recorded beam loss.
	Slides TUOAB2 [8.302 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUOAB2
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TUPAB087	Undulator Commissioning Experience at PAL-XFEL	undulator, electron, radiation, site	1520
	D.E. Kim, Y.G. Jung, H.-S. Kang, I.S. Ko, H.-G. Lee, S.B. Lee, W.W. Lee, K.-H. Park, H.S. Suh PAL, Pohang, Kyungbuk, Republic of Korea I.S. Ko POSTECH, Pohang, Kyungbuk, Republic of Korea J. Pflüger XFEL. EU, Hamburg, Germany
	Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. The hard X-ray undulator line requires 20 units of 5 m long hybrid-type conventional planar undulator while soft X-ray line requires 7 units of 5 m long hybrid type planar undulators. In this report, the final measurement results of all the undulators, phase matching scheme, and the commissioning experiences will be summarized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB087
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TUPIK023	Gas-filled Capillaries for Plasma-Based Accelerators	plasma, acceleration, electron, laser	1731
	F. Filippi INFN-Roma, Roma, Italy M.P. Anania, A. Biagioni, E. Brentegani, E. Chiadroni, M. Ferrario, R. Pompili, S. Romeo INFN/LNF, Frascati (Roma), Italy A. Cianchi INFN-Roma II, Roma, Italy A. Zigler The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	Plasma Wakefield Accelerators are based on the excitation of large amplitude plasma waves excited by either a laser or a particle driver beam. The amplitude of the waves, as well as their spatial dimensions and the consequent accelerating gradient depend strongly on the background electron density along the path of the accelerated particles. The process needs stable and reliable plasma sources, whose density profile must be controlled and properly engineered to ensure the appropriate accelerating mechanism. Plasma confinement inside gas filled capillaries have been studied in the past since this technique allows to control the evolution of the plasma, ensuring a stable and repeatable plasma density distribution during the interaction with the drivers. Moreover, in a gas filled capillary plasma can be pre-ionized by a current discharge to avoid ionization losses. Different capillary geometries have been studied to allow the proper temporal and spatial evolution of the plasma along the acceleration length. Results of this analysis obtained by varying the length and the number of gas inlets will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK023
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TUPIK059	Recent Progress of Dithering System at SuperKEKB	luminosity, feedback, optics, electronics	1827
	Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, S. Nakamura, K. Ohmi, T. Oki, S. Uehara KEK, Ibaraki, Japan P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault LAL, Orsay, France A.S. Fisher SLAC, Menlo Park, California, USA U. Wienands ANL, Argonne, Illinois, USA
	Recent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK059
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TUPIK075	ATF2 Beam Halo Collimation System Background and Wakefield Measurements in the 2016 Runs	collimation, wakefield, simulation, photon	1864
	N. Fuster-Martínez, A. Faus-Golfe IFIC, Valencia, Spain P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang LAL, Orsay, France K. Kubo, T. Okugi, T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan S. Kuroda KEK, Ibaraki, Japan I. Podadera, F. Toral CIEMAT, Madrid, Spain G.R. White SLAC, Menlo Park, California, USA
	A single vertical beam halo collimation system has been installed in ATF2 in March 2016 to reduce the background in the IP and Post-IP region. In this paper, we present the results of an experimental program carried out during 2016 in order to demonstrate the efficiency of the vertical collimation system and measure the wakefields induced by such a system. Furthermore, a comparison of the measurements of the collimation system wakefield impact with CST PS numerical simulations and analytical calculations is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK075
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TUPVA032	Beam-Gas Background Observations at LHC	experiment, detector, simulation, luminosity	2129
	S.M. Gibson Royal Holloway, University of London, Surrey, United Kingdom R. Alemany-Fernández, F. Alessio, G. Bregliozzi, H. Burkhardt, G. Corti, A. Di Mauro, M. Guthoff, A. Manousos, K.N. Sjobak, C. Yin Vallgren CERN, Geneva, Switzerland A. Alici Bologna University, Bologna, Italy S. D'Auria University of Glasgow, Glasgow, United Kingdom S.M. Gibson JAI, Egham, Surrey, United Kingdom D. Lazic BUphy, Boston, Massachusetts, USA
	Observations of beam-induced background at LHC during 2015 and 2016 are presented in this paper. The four LHC experiments use the non-colliding bunches present in the physics-filling pattern of the accelerator to trigger on beam-gas interactions. During luminosity production the LHC experiments record the beam-gas interactions using dedicated background monitors. These data are sent to the LHC control system and are used to monitor the background levels at the experiments during accelerator operation. This is a very important measurement, since poor beam-induced background conditions can seriously affect the performance of the detectors. A summary of the evolution of the background levels during 2015 and 2016 is given in these proceedings.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA032
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WEPAB022	Background-free Harmonic Production in XFELs via a Reverse Undulator Taper	undulator, FEL, radiation, electron	2618
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Nonlinear harmonics in X-ray FELs can be parasitically produced as soon as FEL reaches saturation, or can be radiated in dedicated afterburners. In both cases there is a strong background at the fundamental, since it is much stronger than harmonics. One can get around this problem by application of the recently proposed reverse undulator tapering. In this contribution we present numerical simulations of harmonic production in such a configuration as well as recent results from FLASH where the second and the third harmonics were efficiently generated with a low background at the fundamental. We also present the results for a high-contrast operation when the afterburner is tuned to the fundamental.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB022
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WEPIK004	Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design	detector, photon, luminosity, interaction-region	2914
	G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani CERN, Geneva, Switzerland N. Bacchetta INFN- Sez. di Padova, Padova, Italy M. Boscolo INFN/LNF, Frascati (Roma), Italy M.K. Sullivan SLAC, Menlo Park, California, USA
	A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK004
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WEPIK009	Collimators for SuperKEKB Main Ring	impedance, factory, positron, HOM	2929
	T. Ishibashi, Y. Suetsugu, S. Terui KEK, Ibaraki, Japan
	SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK009
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WEPIK119	Lost Muon Study for the Muon g-2 Experiment at Fermilab	storage-ring, positron, quadrupole, experiment	3230
	J.D. Crnkovic, W. Morse BNL, Upton, Long Island, New York, USA S. Ganguly University of Illinois at Urbana-Champaign, Urbana, USA D. Stratakis Fermilab, Batavia, Illinois, USA
	The Fermilab Muon g-2 Experiment has a goal of measuring the muon anomalous magnetic moment to a precision of 140 ppb - a fourfold improvement over the 540 ppb precision obtained by the BNL Muon g-2 Experiment. Some muons in the storage ring will interact with material and undergo bremsstrahlung, emitting radiation and loosing energy. These so called lost muons will curl in towards the center of the ring and be lost, but some of them will be detected by the calorimeters. A systematic error will arise if the lost muons have a different average spin phase than the stored muons. Algorithms are being developed to estimate the relative number of lost muons, so as to optimize the stored muon beam. This study presents initial testing of algorithms that can be used to estimate the lost muons by using either double or triple detection coincidences in the calorimeters.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK119
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THPVA113	Inverse Problem-Based Magnetic Characterization of Weekly Magnetic Alloys	dipole, radiation, luminosity, collider	4722
	A. Parrella, M.P. Ramos IT, Lisboa, Portugal P. Arpaia, A. Liccardo Naples University Federico II, Science and Technology Pole, Napoli, Italy M.C.L. Buzio CERN, Geneva, Switzerland
	Understanding the magnetic properties of materials used in accelerator components is becoming more and more important. For example, in the upcoming LHC upgrade at CERN, the increasing luminosity will boost the radiation dose received by the accelerator magnet's coil and consequently decrease its lifespan. Hence, a radiation shield with relative permeability less than 1.005 is required. The goal of this research is to design and validate a new method for characterizing weekly magnetic materials, suitable to be used in quality control of series production. The proposed method is based on inverse analysis approach coupled with a finite-element model. A material with unknown permeability is inserted in the air gap of a dipole magnet and the consequent perturbations of the dipole background flux density are measured. The magnetic permeability is then identified through gray-box inverse modelling, based on a finite-element approach. The results have been used to predict the magnetic impact of the radiation shield and develop further research on this subject.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA113
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Paper

Title

Other Keywords

Page

MOPAB065

Breit-Wheeler Scattering Events Produced by Two Interacting Compton Sources

photon, scattering, electron, laser

261

I. Drebot, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
D. Micieli, E. Tassi
UNICAL, Arcavacata di Rende, Italy
E. Milotti
INFN-Trieste, Trieste, Italy
V. Petrillo
Universita' degli Studi di Milano & INFN, Milano, Italy

We present the dimensioning of a photon-photon collider based on conventional Compton gamma sources for the observation of Breit-Wheeler pair production and QED gamma-gamma generation. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two primary gamma rays through Compton back-scattering with two high-energy lasers. Tuning the system energy above the Breit-Wheeler cross section threshold, a flux of secondary electrons and positrons is generated. The process is analyzed by start-to-end simulations. The Monte Carlo code 'Rate Of Scattering Events' (ROSE) has been developed ad hoc for the counting of the QED events. Realistic numbers of the secondary particles yield, referring to existing or approved set-ups, a discussion of the feasibility of the experiment and the evaluation of the background are presented.

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MOPAB098

Coronagraph Based Beam Halo Monitor Development for BERLinPro

electron, dipole, linac, scattering

355

J.G. Hwang
Kyungpook National University, Daegu, Republic of Korea
J. Kuszynski
HZB, Berlin, Germany

For linac based high power electron machines, beam halo induced by nonlinear space charge force and scattering of trapped ions is one of the critical issues on a machine protection system. It causes additional radiation which can be a heat source on a cryogenic system as a result of uncontrolled beam losses. During the last decades, several instruments have been newly developed for measuring the beam halo distribution. The conceptual design and optimization of the coronagraph based halo monitor were performed to measure the beam halo which has ~ 10^-3 contrast to the beam core.

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MOPAB112

Schottky Based Intensity Measurements and Errors Due to Statistical Fluctuations

antiproton, pick-up, instrumentation, diagnostics

385

C. Carli, M.E. Angoletta, F. Caspers, O.R. Jones, F. Pedersen, J. Sanchez-Quesada, L. Søby
CERN, Geneva, Switzerland

The beam intensities at the Extra Low ENergy Antiproton ring ELENA are too low for standard beam current transformers and, thus, are measured with longitudinal Schottky diagnostics. This method is already successfully used at the Antiproton Decelerator since the commissioning of this machine. The fact that Schottky noise is a statistical phenomenon implies statistical errors of these measurements. Simple analytical formulas describing the statistical error to be expected as a function of the frequency spread of the band considered, the time resolution chosen and the background noise have been derived. On the one hand, low revolution harmonics and, in turn, frequency spread of the band analysed lead to large measurement errors as this situation corresponds to low momentum resolution of the resulting distribution describing the beam. At very large revolution harmonics and, thus, frequency spreads of the band analysed, the measurement error increases again due to additional contributions from the background noise.

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MOPAB128

The Design of a Non-Destructive Single-Shot Longitudinal Bunch Profile Monitor using Smith-Purcell Radiation

radiation, detector, polarization, experiment

433

H. Harrison, G. Doucas, I.V. Konoplev, A.J. Lancaster, H. Zhang
JAI, Oxford, United Kingdom
A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: This work was supported by the: the STFC UK, the Leverhulme Trust, the JAI (University of Oxford) and the Photon and Quantum Basic Research Coordinated Development (Japan).
The conceptual design for a single-shot longitudinal bunch profile monitor using coherent Smith-Purcell radiation (cSPr) has recently been completed. The exploitation of the directionality and the polarization of cSPr to reduce the length of the monitor and to eliminate background radiation are discussed. The linear polarization of cSPr will be used to separate the signal from background radiation and experiments to test this design will be presented. Alongside the conceptual design an investigation to optimize the number of detection channels needed to produce high quality longitudinal bunch profile reconstructions has been carried out. It has been determined that the number of detection channels can be reduced compared to previous experiments if measurement uncertainty and background radiation are minimized effectively.

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MOPIK091

Development of Real-Time Charge Integrator for the Irradiation Dose Measurement

real-time, target, Ethernet, controls

739

H.G. Lim, Y.-S. Cho, Y.S. Hwang, M.H. Jung, K. R. Kim
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC (KOREA of Multi-purpose Accelerator Complex) operation fund of KAERI by MSIP (Ministry of Science, ICT, and Future Planning).
KOMAC (Korea of Multi-purpose Accelerator Complex, Gyeongju, Korea) has several kinds of facilities using proton beam or ion beam. The KOMAC has provided beam service to user group since 2013. For effective beam service, it is important that irradiation dose at a target should be supplied as much as user requires. To control the irradiation dose of target, a multi-channels charge integrator, Faraday cups, and a beam shutter are used. The amount of irradiation dose is calculated in real time by accumulative charge, which is represented to integration of induced current at each Faraday cup for the target. If the measurements reach to the set value (desired dose), the beam is automatically blocked by beam shutter. Thus, precise measurement of accumulative charge is required. For out purpose, two kinds of real-time charge integrators were implemented with different measuring ranges. In order to verify performance of the integrators, each device's linearity was evaluated after measuring accumulative charge corresponding to dc current. And their measurable range was determined.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK091

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MOPVA041

Vertical Test Results on ESS Medium and High Beta Elliptical Cavity Prototypes Equipped with Helium Tank

cavity, linac, radiation, cryomodule

948

E. Cenni
CEA/IRFU, Gif-sur-Yvette, France
P. Bosland, G. Devanz, F. Éozénou, X. Hanus, L. Maurice, F. Peauger, J. Plouin, D. Roudier, C. Servouin
CEA/DSM/IRFU, France
G. Costanza
Lund University, Lund, Sweden
C. Darve
ESS, Lund, Sweden

The ESS elliptical superconducting Linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity Linac) up to the final energy at 2 GeV. The last Linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the Linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. This work presents the latest vertical test results on ESS medium and high beta elliptical cavity prototypes equipped with helium tank. We describe the cavity preparation procedure from buffer chemical polishing to vertical test.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA041

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TUOAB2

First Observation of the LHC Beam Halo Using a Synchrotron Radiation Coronagraph

simulation, synchrotron, radiation, photon

1244

T.M. Mitsuhashi
KEK, Ibaraki, Japan
E. Bravin, F. Roncarolo, G. Trad
CERN, Geneva, Switzerland

A test coronagraph for the observation of beam halo has been installed in the Synchrotron radiation monitor line LHCB2 in 2015. This coronagraph is commissioned with LHC operation at 450GeV (injection energy). After some optical testing of the coronagraph with visible Synchrotron radiation in B2, we try to observe artificially-made beam halo. The beam halo of 10^-3 order of magnitude against the beam core is excited by the kicker of the transverse damper. We have succeeded to observe a diffraction noise free image of beam halo. The effect of beam collimator is also observed. Reduction of beam halo intensity was found nicely proportional to the simultaneously-recorded beam loss.

Slides TUOAB2 [8.302 MB]

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TUPAB087

Undulator Commissioning Experience at PAL-XFEL

undulator, electron, radiation, site

1520

D.E. Kim, Y.G. Jung, H.-S. Kang, I.S. Ko, H.-G. Lee, S.B. Lee, W.W. Lee, K.-H. Park, H.S. Suh
PAL, Pohang, Kyungbuk, Republic of Korea
I.S. Ko
POSTECH, Pohang, Kyungbuk, Republic of Korea
J. Pflüger
XFEL. EU, Hamburg, Germany

Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. The hard X-ray undulator line requires 20 units of 5 m long hybrid-type conventional planar undulator while soft X-ray line requires 7 units of 5 m long hybrid type planar undulators. In this report, the final measurement results of all the undulators, phase matching scheme, and the commissioning experiences will be summarized.

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TUPIK023

Gas-filled Capillaries for Plasma-Based Accelerators

plasma, acceleration, electron, laser

1731

F. Filippi
INFN-Roma, Roma, Italy
M.P. Anania, A. Biagioni, E. Brentegani, E. Chiadroni, M. Ferrario, R. Pompili, S. Romeo
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
INFN-Roma II, Roma, Italy
A. Zigler
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

Plasma Wakefield Accelerators are based on the excitation of large amplitude plasma waves excited by either a laser or a particle driver beam. The amplitude of the waves, as well as their spatial dimensions and the consequent accelerating gradient depend strongly on the background electron density along the path of the accelerated particles. The process needs stable and reliable plasma sources, whose density profile must be controlled and properly engineered to ensure the appropriate accelerating mechanism. Plasma confinement inside gas filled capillaries have been studied in the past since this technique allows to control the evolution of the plasma, ensuring a stable and repeatable plasma density distribution during the interaction with the drivers. Moreover, in a gas filled capillary plasma can be pre-ionized by a current discharge to avoid ionization losses. Different capillary geometries have been studied to allow the proper temporal and spatial evolution of the plasma along the acceleration length. Results of this analysis obtained by varying the length and the number of gas inlets will be presented.

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TUPIK059

Recent Progress of Dithering System at SuperKEKB

luminosity, feedback, optics, electronics

1827

Y. Funakoshi, H. Fukuma, T. Kawamoto, M. Masuzawa, S. Nakamura, K. Ohmi, T. Oki, S. Uehara
KEK, Ibaraki, Japan
P. Bambade, D. El Khechen, D. Jehanno, V. Kubytskyi, C. Rimbault
LAL, Orsay, France
A.S. Fisher
SLAC, Menlo Park, California, USA
U. Wienands
ANL, Argonne, Illinois, USA

Recent progress of the dithering system at SuperKEKB is described. Some details of the system layout are shown. Beam orbit and optics related issues are discussed. Preliminary tests of the some components in the Phase 1 beam commissioning or in the bench are described.

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TUPIK075

ATF2 Beam Halo Collimation System Background and Wakefield Measurements in the 2016 Runs

collimation, wakefield, simulation, photon

1864

N. Fuster-Martínez, A. Faus-Golfe
IFIC, Valencia, Spain
P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang
LAL, Orsay, France
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan
S. Kuroda
KEK, Ibaraki, Japan
I. Podadera, F. Toral
CIEMAT, Madrid, Spain
G.R. White
SLAC, Menlo Park, California, USA

A single vertical beam halo collimation system has been installed in ATF2 in March 2016 to reduce the background in the IP and Post-IP region. In this paper, we present the results of an experimental program carried out during 2016 in order to demonstrate the efficiency of the vertical collimation system and measure the wakefields induced by such a system. Furthermore, a comparison of the measurements of the collimation system wakefield impact with CST PS numerical simulations and analytical calculations is also presented.

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TUPVA032

Beam-Gas Background Observations at LHC

experiment, detector, simulation, luminosity

2129

S.M. Gibson
Royal Holloway, University of London, Surrey, United Kingdom
R. Alemany-Fernández, F. Alessio, G. Bregliozzi, H. Burkhardt, G. Corti, A. Di Mauro, M. Guthoff, A. Manousos, K.N. Sjobak, C. Yin Vallgren
CERN, Geneva, Switzerland
A. Alici
Bologna University, Bologna, Italy
S. D'Auria
University of Glasgow, Glasgow, United Kingdom
S.M. Gibson
JAI, Egham, Surrey, United Kingdom
D. Lazic
BUphy, Boston, Massachusetts, USA

Observations of beam-induced background at LHC during 2015 and 2016 are presented in this paper. The four LHC experiments use the non-colliding bunches present in the physics-filling pattern of the accelerator to trigger on beam-gas interactions. During luminosity production the LHC experiments record the beam-gas interactions using dedicated background monitors. These data are sent to the LHC control system and are used to monitor the background levels at the experiments during accelerator operation. This is a very important measurement, since poor beam-induced background conditions can seriously affect the performance of the detectors. A summary of the evolution of the background levels during 2015 and 2016 is given in these proceedings.

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WEPAB022

Background-free Harmonic Production in XFELs via a Reverse Undulator Taper

undulator, FEL, radiation, electron

2618

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Nonlinear harmonics in X-ray FELs can be parasitically produced as soon as FEL reaches saturation, or can be radiated in dedicated afterburners. In both cases there is a strong background at the fundamental, since it is much stronger than harmonics. One can get around this problem by application of the recently proposed reverse undulator tapering. In this contribution we present numerical simulations of harmonic production in such a configuration as well as recent results from FLASH where the second and the third harmonics were efficiently generated with a low background at the fundamental. We also present the results for a high-contrast operation when the afterburner is tuned to the fundamental.

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WEPIK004

Luminosity- and Beam- Induced Backgrounds for the FCC-ee Interaction Region Design

detector, photon, luminosity, interaction-region

2914

G.G. Voutsinas, P. Janot, A.M. Kolano, E. Perez, N.A. Tehrani
CERN, Geneva, Switzerland
N. Bacchetta
INFN- Sez. di Padova, Padova, Italy
M. Boscolo
INFN/LNF, Frascati (Roma), Italy
M.K. Sullivan
SLAC, Menlo Park, California, USA

A preliminary study on machine induced backgrounds has been performed for the proposed FCC-ee interaction region (IR) and proto-detector. Synchrotron radiation has the strongest impact on the present design of the IR and both radiation from dipoles and quadrupoles have been taken into account. The effect of luminosity backgrounds like gamma gamma to hadrons and pair production have also been studied. The impact of background particles on the detector occupancy has also been studied in full simulation.

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WEPIK009

Collimators for SuperKEKB Main Ring

impedance, factory, positron, HOM

2929

T. Ishibashi, Y. Suetsugu, S. Terui
KEK, Ibaraki, Japan

SuperKEKB, which is an upgrade project of KEKB, is an electron-positron collider with extremely high luminosity. Collimators (movable masks) for SuperKEKB have been designed to fit an antechamber scheme of the vacuum system and will be operated to improve backgrounds in the particle detector named Belle II. We are developing two types of collimators; a horizontal and vertical collimator. The collimator has a pair of horizontally or vertically opposed movable jaws with RF fingers. Each jaw travels independently through 5-25 mm horizontally or 2-12 mm vertically in a distance between the beam axis and the tip of the jaw. SuperKEKB will operate with high currents of short bunch lengths, therefore it is important to estimate and decrease the impedance of the collimators. Two horizontal collimators were already installed in the positron ring and operated during Phase-1 commissioning for approximately 5 months, from February to June 2016. In this presentation, the latest design, and the results in the Phase-1 commissioning are presented.

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WEPIK119

Lost Muon Study for the Muon g-2 Experiment at Fermilab

storage-ring, positron, quadrupole, experiment

3230

J.D. Crnkovic, W. Morse
BNL, Upton, Long Island, New York, USA
S. Ganguly
University of Illinois at Urbana-Champaign, Urbana, USA
D. Stratakis
Fermilab, Batavia, Illinois, USA

The Fermilab Muon g-2 Experiment has a goal of measuring the muon anomalous magnetic moment to a precision of 140 ppb - a fourfold improvement over the 540 ppb precision obtained by the BNL Muon g-2 Experiment. Some muons in the storage ring will interact with material and undergo bremsstrahlung, emitting radiation and loosing energy. These so called lost muons will curl in towards the center of the ring and be lost, but some of them will be detected by the calorimeters. A systematic error will arise if the lost muons have a different average spin phase than the stored muons. Algorithms are being developed to estimate the relative number of lost muons, so as to optimize the stored muon beam. This study presents initial testing of algorithms that can be used to estimate the lost muons by using either double or triple detection coincidences in the calorimeters.

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THPVA113

Inverse Problem-Based Magnetic Characterization of Weekly Magnetic Alloys

dipole, radiation, luminosity, collider

4722

A. Parrella, M.P. Ramos
IT, Lisboa, Portugal
P. Arpaia, A. Liccardo
Naples University Federico II, Science and Technology Pole, Napoli, Italy
M.C.L. Buzio
CERN, Geneva, Switzerland

Understanding the magnetic properties of materials used in accelerator components is becoming more and more important. For example, in the upcoming LHC upgrade at CERN, the increasing luminosity will boost the radiation dose received by the accelerator magnet's coil and consequently decrease its lifespan. Hence, a radiation shield with relative permeability less than 1.005 is required. The goal of this research is to design and validate a new method for characterizing weekly magnetic materials, suitable to be used in quality control of series production. The proposed method is based on inverse analysis approach coupled with a finite-element model. A material with unknown permeability is inserted in the air gap of a dipole magnet and the consequent perturbations of the dipole background flux density are measured. The magnetic permeability is then identified through gray-box inverse modelling, based on a finite-element approach. The results have been used to predict the magnetic impact of the radiation shield and develop further research on this subject.

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