HB2018 - Classification: Beam Instruments and Interactions

Paper	Title	Page
TUP1WE01	RAON Beam Diagnostics System
	Y.S. Chung, G.D. Kim, H.J. Woo IBS, Daejeon, Republic of Korea J.W. Kwon Korea University, Seoul, Republic of Korea
	The ultimate goal of RAON is to accelerate uranium and proton beams up to 200 MeV/u and 600 MeV, with a maximum beam currents of 8.3 pμA and 660 pμA, respectively. Various types of beam diagnostic devices such as beam current monitor, beam position monitor (BPM), beam profile monitor, beam phase monitor, and beam loss monitor are required for setting accelerator parameters, monitoring beam acceleration and transport, and improving accelerator system. ACCT and Faraday cup will be used for beam intensity measurement. Hundreds of BPMs will be used for the measurement of transversal position and phase. Various profile monitors such as wire scanner, wire grid, and Fast Faraday cup will be installed for monitoring beam shapes in the transversal and longitudinal beam directions. And plastic detector, proportional counter, and Halo Monitor Ring are considered for beam loss monitor. The design and status of RAON beam diagnostics system will be discussed.
	Slides TUP1WE01 [4.902 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP1WE02	Hollow Electron-Lens Assisted Collimation and Plans for the LHC	92
	D. Mirarchi, H. Garcia Morales, A. Mereghetti, S. Redaelli, J.F. Wagner CERN, Geneva, Switzerland W. Fischer, X. Gu BNL, Upton, Long Island, New York, USA H. Garcia Morales Royal Holloway, University of London, Surrey, United Kingdom D. Mirarchi The University of Manchester, The Photon Science Institute, Manchester, United Kingdom G. Stancari Fermilab, Batavia, Illinois, USA J.F. Wagner IAP, Frankfurt am Main, Germany
	The hollow electron lens (e-lens) is a very powerful and advanced tool for active control of diffusion speed of halo particles in hadron colliders. Thus, it can be used for a controlled depletion of beam tails and enhanced beam halo collimation. This is of particular interest in view of the upgrade of the Large Hadron Collider (LHC) at CERN, in the framework of the High-Luminosity LHC project (HL-LHC). The estimated stored energy in the tails of the HL-LHC beams is about 30 MJ, posing serious constraints on its control and safe disposal. In particular, orbit jitter can cause significant loss spikes on primary collimators, which can lead to accidental beam bump and magnet quench. Successful tests of e-lens assisted collimation have been carried out at the Tevatron collider at Fermilab and a review of the main outcomes is shown. Preliminary results of recent experiments performed at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven, put in place to explore different operational scenarios studies for the HL-LHC, are also discussed. Status and plans for the deployment of hollow electron lenses at the HL-LHC are presented.
	Slides TUP1WE02 [29.382 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WE02
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP1WE03	Beam Instruments for High Power Spallation Neutron Source and Facility for ADS	99
	S.I. Meigo JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	As increase of beam power, beam instruments play an essential role in the Hadron accelerator facility. In J-PARC, the pitting erosion on the mercury target vessel for the spallation neutron source is one of a pivotal issue to operate with the high power of the beam operation. Since the erosion is proportional to the 4th power of the beam current density, the minimization of the peak current density is required. To achieve low current density, the beam-flattening system by nonlinear beam optics using octupole magnets in J-PARC. By the present system, the peak density was successfully reduced by 30% compared to the ordinary linear optics. Also in J-PARC, transmutation experimental facility is planned for the realization of the accelerator-driven system (ADS), which will employ powerful accelerator with the beam power of 30 MW. To achieve equivalent damage on the target as the ADS, the target will be received high current density. For the continuous observation of the beam status on the target, a robust beam profile monitor is required. We have been developed beam profile monitor by using heavy-ion of Ar beam to give the damage efficiently.
	Slides TUP1WE03 [15.133 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WE03
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP2WE01	Injection Foil Temperature Measurements at the SNS Accelerator	104
	W. Blokland, C.F. Luck, A. Rakhman ORNL, Oak Ridge, Tennessee, USA N.J. Evans ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The SNS uses charge exchange injection to minimize losses during the accumulation of the accelerated beam in the ring. A stripper foil implements this by removing the electrons from the high intensity H⁻ beam coming from the linac. At a beam power of 1.2 MW, the foil lasts for many weeks, sometimes months. However, given the upgrade to 2.8 MW, it is important to know the current temperature of stripper foil in order to estimate its lifetime for the new beam power and beam size. In this paper, we discuss several methods to measure the temperature of stripper foil exposed to current operating conditions of the SNS accelerator. Given the high radiation in the vicinity of the foil, the uncertainty in the foil's emissivity, and available resources, we chose a two-wavelength pyrometer that is located 40 m from the foil. The pyrometer is composed of two mirrors, a refracting telescope, and two photodiodes. We present the calibration data and the temporally resolved measurements made with this pyrometer.
	Slides TUP2WE01 [13.195 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE01
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP2WE03	Radiation Damage Calculation in PHITS and Benchmarking Experiment for Cryogenic-Sample High-Energy Proton Irradiation	116
	Y. Iwamoto, D. Satoh JAEA, Ibaraki-ken, Japan Y. Ishi, Y. Kuriyama, T. Uesugi, H. Yashima, T. Yoshiie Kyoto University, Research Reactor Institute, Osaka, Japan H. Matsuda, S.I. Meigo JAEA/J-PARC, Tokai-mura, Japan T. Nakamoto KEK, Ibaraki, Japan K. Niita Research Organization for Information Science & Technology, Ibaraki, Japan R.M. Ronningen FRIB, East Lansing, Michigan, USA T. Shima RCNP, Osaka, Japan
	Funding: The experimental study was supported by JSPS KAKENHI, Grant Number JP 16H04638 and 25820450. The calculation work was supported in part by the US National Science Foundation under grant PHY06-06007. The radiation damage model in the Particle and Heavy Ion Transport code System (PHITS) has been developed using the screened Coulomb scattering to evaluate the energy of the target Primary Knock on Atom (PKA) created by the projectile and the secondary particles which include all particles created from the sequential nuclear reactions. For the high-energy proton incident reactions, a target PKA created by the secondary particles was more dominant than a target PKA created by the projectile. To validate prediction of DPA values in metals irradiated by >100 MeV protons, we developed a proton irradiation device with a Gifford-McMahon (GM) cryocooler to cryogenically cool wire samples. By using this device, the defect-induced electrical resistivity changes related to the DPA cross section of copper and aluminum were measured under irradiation with 125 and 200 MeV protons at cryogenic temperature. A comparison of the experimental DPA cross sections with the calculated results indicates that the athermal-recombination-corrected displacement damage (arc-dpa) provide better quantitative descriptions of the DPA cross section than NRT-dpa without defect production efficiencies.
	Slides TUP2WE03 [4.747 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE03
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP2WE04	Design of the Target Dump Injection Segmented (TDIS) in the Framework of the High Luminosity Large Hadron Collider (HL-LHC) Project	122
	L. Teofili, D. Carbajo Perez, I. Lamas Garcia, M. Migliorati, A. Perillo CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy M. Migliorati Sapienza University of Rome, Rome, Italy
	The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In this scenario most equipment has to be redesigned and rebuilt. In particular, beam intercepting devices (as dumps, collimators, absorbers and scrapers) have to withstand impact or scraping of the new intense HL-LHC beams without failures. Further, minimizing the electromagnetic beam-device interactions is also a key design driver since they can lead to beam instabilities and excessive thermo-mechanical loading of devices. In this context, the present study assesses the conceptual design quality of the new LHC injection dump, the Target Dump Injection Segmented (TDIS), from an electromagnetic and thermo-mechanical perspective. This contribution analyzes the thermo-mechanical response of the device considering two cases: an accidental beam impact scenario and another accidental scenario with complete failure of the RF-contacts. Further, this paper presents the preliminary results for the simulation of the energy deposited by the two counter-rotating beams circulating in the device.
	Slides TUP2WE04 [10.895 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE04
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP2PO030	A 4D Emittance Measurement Device for the 870 keV HIPA Injection Line	329
	R. Dölling, M. Rohrer PSI, Villigen PSI, Switzerland
	A 4D emittance measurement device has recently been installed in PSI's high intensity proton accelerator (HIPA) after the acceleration tube of the Cockcroft-Walton pre-accelerator. A pinhole collimator is moved 2D transversally and at each collimator position, the resulting beamlet is downstream scanned 2D by vertically moving over it a horizontal linear array of small electrodes. The properties of this setup and the intended use are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP2PO032	A Secondary Emission Monitor in the SINQ Beam Line for Improved Target Protection	334
	R. Dölling, M. Rohrer PSI, Villigen PSI, Switzerland
	A 4-strip secondary-emission monitor (SEM) has been installed in the beam line to the SINQ neutron source to detect irregular fractions of the megawatt proton beam which might damage the spallation target. We discuss the estimated performance of the monitor as well as its design and implementation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO032
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP2PO033	A Test of Stripper Foil Lifetime in PSI's 72 MeV Proton Beam	338
	R. Dölling, R. Dressler PSI, Villigen PSI, Switzerland L. Calabretta INFN/LNS, Catania, Italy
	A test of the lifetime of an amorphous carbon foil of ~79 ug/cm² was performed at PSI in the transfer line between Injector 2 and Ring cyclotron during the regularly beam production. The 72 MeV ~1.7 mA proton beam had a central current density of ~2.8 mA/cm². Two spots on the foil were irradiated alternatively with in total three fractions of 17, 52 and 119 mAh. Foil thickness was measured before and after irradiation at several positions via the energy loss of alpha-particles from a 241Am source in the foil. We discuss the observed foil damage as well as the experimental setup, the estimation of the beam parameters and practical boundary conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO033
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE01	New Electron Cloud Instability Mechanism and its Detection and Suppression
	V.A. Lebedev Fermilab, Batavia, Illinois, USA S. A. Antipov CERN, Geneva, Switzerland
	Fast transverse instability was observed in Recycler proton storage ring (RR). The instability develops within 100 turns and may lead to beam loss. The fast rise suggested that the instability is driven by electron cloud. That was later supported by microwave transmission measurements. In difference to RR the instability was not observed in similar conditions in Main Injector (MI). RR is based on combined function dipoles while MI uses pure dipoles. This difference plays a key role in instability development. The instability dynamics was studied experimentally and with numerical simulations. An analytical model predicts that electrons are trapped in RR dipoles. Numerical simulations show that up to 1% of particles can be trapped. The cloud build-up is exponential with its density limited by space charge. That results in the cloud intensity orders of magnitude greater than in MI. A growth rate of about 30 turns and mode frequency of 0.4 MHz are consistent for observations and PEI simulations. The high intensity batch can be stabilized by low intensity clearing bunch injected behind batch which destroys the trapped electron cloud and prevents its multi-turn accumulation.
	Slides THA1WE01 [7.328 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE02	Requirements and Results for Quadrupole Mode Measurements	393
	A. Oeftiger CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project. Direct space charge may be quantified, and hence the beam brightness observed, by measuring the quadrupolar beam modes in the CERN Proton Synchrotron (PS). The spectrum of the transverse beam size oscillations (i.e. the quadrupolar beam moment) contains valuable information: the betatron envelope modes and the coherent dispersive mode indicate optics mismatch, while their frequency shifts due to space charge allow a direct measurement thereof. To measure the quadrupolar beam moment we use the Base-Band Q-meter system of the PS which is based on a four electrode stripline pick-up. Past experiments with quadrupolar pick-ups often investigated coasting beams, where the coherent betatron and dispersion modes correspond to single peaks in the tune spectrum. In contrast, long bunched beams feature bands of betatron modes: the mode frequencies shift depending on the transverse space charge strength which varies with the local line charge density. By using the new transverse feedback in the PS as a quadrupolar RF exciter, we measured the quadrupolar beam transfer function. The beam response reveals the distinct band structure of the envelope modes as well as the coherent dispersive mode.
	Slides THA1WE02 [7.315 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE02
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE03	BPM Technologies for Quadrupolar Moment Measurements	399
	A. Sounas, M. Gąsior, T. Lefèvre CERN, Geneva, Switzerland
	Quadrupolar moment measurements based on electromagnetic pick-ups (PU), like BPMs, have attracted particular interest as non-intercepting diagnostics to determine the transverse beam size. Here, the second-order moment, which contains information about the beam size, is extracted from the BPM electrode signals. Despite the simplicity of the concept, quadrupololar measurements have always been challenging in practice. This is related to the fact that the quadrupolar moment constitutes only a very small part of the total PU signal, which is dominated by the contributions of beam intensity and position. In this study we discuss the limitations of absolute quadrupolar measurements if applying traditional BPM technologies, and we propose a new approach to efficiently overcome them via movable PUs. Moreover, we highlight the potential use of BPMs as an emittance measurement system during the energy ramp at synchrotrons by performing differential quadrupolar measurements, which show a remarkably higher accuracy than absolute measurements. Dedicated studies using different types of BPMs in the Large Hadron Collider (LHC) at CERN demonstrated promising results.
	Slides THA1WE03 [5.299 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE03
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE04	ESS nBLM: Beam Loss Monitors based on Fast Neutron Detection	404
	T. Papaevangelou CEA/IRFU, Gif-sur-Yvette, France H. Alves, S. Aune, J. Beltramelli, Q. Bertrand, T. Bey, B. Bolzon, N. Chauvin, M. Combet, D. Desforge, M. Desmons, Y. Gauthier, E. Giner-Demange, A. Gomes, F. Gougnaud, F. Harrault, F. J. Iguaz Gutierrez, T.J. Joannem, M. Kebbiri, C. Lahonde-Hamdoun, P. Le Bourlout, Ph. Legou, O. Maillard, A. Marcel, C. Marchand, Y. Mariette, J. Marroncle, V. Nadot, M. Oublaid, G. Perreu, O. Piquet, B. Pottin, Y. Sauce, J. Schwindling, L. Segui, F. Senée, R. Touzery, G. Tsiledakis, O. Tuske, D. Uriot IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France I. Dolenc Kittelmann, R.J. Hall-Wilton, C. Höglund, L. Robinson, T.J. Shea, P. Svensson ESS, Lund, Sweden V. Gressier IRSN, Saint-Paul-Lez-Durance, France K. Nikolopoulos Birmingham University, Birmingham, United Kingdom M. Pomorski CEA/DRT/LIST, Gif-sur-Yvette Cedex, France
	A new type of Beam Loss Monitor (BLM) system is being developed for use in the European Spallation Source (ESS) linac, primarily aiming to cover the low energy part (proton energies between 3-100 MeV). In this region of the linac, typical BLM detectors based on charged particle detection (i.e. Ionization Cham-bers) are not appropriate because the expected particle fields will be dominated by neutrons and photons. Another issue is the photon background due to the RF cavities, which is mainly due to field emission from the electrons from the cavity walls, resulting in brems-strahlung photons. The idea for the ESS neutron sensi-tive BLM system (ESS nBLM) is to use Micromegas detectors specially designed to be sensitive to fast neutrons and insensitive to low energy photons (X and gammas). In addition, the detectors must be insensitive to thermal neutrons, because those neutrons may not be directly correlated to beam losses. The appropriate configuration of the Micromegas operating conditions will allow excellent timing, intrinsic photon back-ground suppression and individual neutron counting, extending thus the dynamic range to very low particle fluxes.
	Slides THA1WE04 [3.267 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE04
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA2WE01	Bayesian Optimization for Online FEL Tuning at LCLS
	J.P. Duris, M.W. McIntire, D.F. Ratner SLAC, Menlo Park, California, USA D. Dylan UCSC, Santa Cruz, California, USA
	The Linac Coherent Light Source changes configurations 2 to 5 times per day, necessitating fast tuning strategies to reduce setup time for successive experiments. To this end, we employ a Bayesian approach to transport optics tuning to quickly optimize groups of quadrupole magnets. The power of Bayesian optimization lies in its ability to employ a probability distribution to represent the most likely region of a control feature space to optimize an objective. A Gaussian process allows us to employ kernel learning to modify the Bayesian likelihood of the machine response from observed data and learned characteristics of the machine response with respect to the controlled parameters. We build Bayesian priors and response correlations from historical LCLS run data of FEL pulse energy versus quadrupole magnet strengths, and use this to simultaneously optimize quadrupoles. Here, we introduce Bayesian optimization with Gaussian processes, and then describe our approach to training the optimizer on historical LCLS data.
	Slides THA2WE01 [2.511 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA2WE02	Application of Machine Learning for the IPM-Based Profile Reconstruction	410
	M. Sapinski, R. Singh, D.M. Vilsmeier GSI, Darmstadt, Germany J.W. Storey CERN, Geneva, Switzerland
	One of the most reliable devices to measure the transverse beam profile in hadron machines is Ionization Profile Monitor (IPM). This type of monitor can work in two modes: collecting electrons or ions. Typically, for lower intensity beams, the ions produced by ionization of the rest gas are extracted towards a position-sensitive detector. Ion trajectories follow the external electric field lines, however the field of the beam itself also affects their movement leading to a deformation of the observed beam profile. Correction methods for this case are known. For high brightness beams, IPM configuration in which electrons are measured, is typically used. In such mode, an external magnetic field is often applied in order to confine the transverse movement of electrons. However, for extreme beams, the distortion of the measured beam profile can still be present. The dynamics of electron movement is more complex than in case of ions, therefore the correction of the profile distortion is more difficult. Investigation of this problem using a dedicated simulation tool and machine learning algorithms lead to a beam profile correction methods for electron-collecting IPMs.
	Slides THA2WE02 [7.357 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA2WE02
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUP1WE01

RAON Beam Diagnostics System

Y.S. Chung, G.D. Kim, H.J. Woo
IBS, Daejeon, Republic of Korea
J.W. Kwon
Korea University, Seoul, Republic of Korea

The ultimate goal of RAON is to accelerate uranium and proton beams up to 200 MeV/u and 600 MeV, with a maximum beam currents of 8.3 pμA and 660 pμA, respectively. Various types of beam diagnostic devices such as beam current monitor, beam position monitor (BPM), beam profile monitor, beam phase monitor, and beam loss monitor are required for setting accelerator parameters, monitoring beam acceleration and transport, and improving accelerator system. ACCT and Faraday cup will be used for beam intensity measurement. Hundreds of BPMs will be used for the measurement of transversal position and phase. Various profile monitors such as wire scanner, wire grid, and Fast Faraday cup will be installed for monitoring beam shapes in the transversal and longitudinal beam directions. And plastic detector, proportional counter, and Halo Monitor Ring are considered for beam loss monitor. The design and status of RAON beam diagnostics system will be discussed.

Slides TUP1WE01 [4.902 MB]

Export •

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

TUP1WE02

Hollow Electron-Lens Assisted Collimation and Plans for the LHC

92

D. Mirarchi, H. Garcia Morales, A. Mereghetti, S. Redaelli, J.F. Wagner
CERN, Geneva, Switzerland
W. Fischer, X. Gu
BNL, Upton, Long Island, New York, USA
H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom
D. Mirarchi
The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
G. Stancari
Fermilab, Batavia, Illinois, USA
J.F. Wagner
IAP, Frankfurt am Main, Germany

The hollow electron lens (e-lens) is a very powerful and advanced tool for active control of diffusion speed of halo particles in hadron colliders. Thus, it can be used for a controlled depletion of beam tails and enhanced beam halo collimation. This is of particular interest in view of the upgrade of the Large Hadron Collider (LHC) at CERN, in the framework of the High-Luminosity LHC project (HL-LHC). The estimated stored energy in the tails of the HL-LHC beams is about 30 MJ, posing serious constraints on its control and safe disposal. In particular, orbit jitter can cause significant loss spikes on primary collimators, which can lead to accidental beam bump and magnet quench. Successful tests of e-lens assisted collimation have been carried out at the Tevatron collider at Fermilab and a review of the main outcomes is shown. Preliminary results of recent experiments performed at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven, put in place to explore different operational scenarios studies for the HL-LHC, are also discussed. Status and plans for the deployment of hollow electron lenses at the HL-LHC are presented.

Slides TUP1WE02 [29.382 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WE02

Export •

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

TUP1WE03

Beam Instruments for High Power Spallation Neutron Source and Facility for ADS

99

S.I. Meigo
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

As increase of beam power, beam instruments play an essential role in the Hadron accelerator facility. In J-PARC, the pitting erosion on the mercury target vessel for the spallation neutron source is one of a pivotal issue to operate with the high power of the beam operation. Since the erosion is proportional to the 4th power of the beam current density, the minimization of the peak current density is required. To achieve low current density, the beam-flattening system by nonlinear beam optics using octupole magnets in J-PARC. By the present system, the peak density was successfully reduced by 30% compared to the ordinary linear optics. Also in J-PARC, transmutation experimental facility is planned for the realization of the accelerator-driven system (ADS), which will employ powerful accelerator with the beam power of 30 MW. To achieve equivalent damage on the target as the ADS, the target will be received high current density. For the continuous observation of the beam status on the target, a robust beam profile monitor is required. We have been developed beam profile monitor by using heavy-ion of Ar beam to give the damage efficiently.

Slides TUP1WE03 [15.133 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WE03

Export •

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

TUP2WE01

Injection Foil Temperature Measurements at the SNS Accelerator

104

W. Blokland, C.F. Luck, A. Rakhman
ORNL, Oak Ridge, Tennessee, USA
N.J. Evans
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy.
The SNS uses charge exchange injection to minimize losses during the accumulation of the accelerated beam in the ring. A stripper foil implements this by removing the electrons from the high intensity H⁻ beam coming from the linac. At a beam power of 1.2 MW, the foil lasts for many weeks, sometimes months. However, given the upgrade to 2.8 MW, it is important to know the current temperature of stripper foil in order to estimate its lifetime for the new beam power and beam size. In this paper, we discuss several methods to measure the temperature of stripper foil exposed to current operating conditions of the SNS accelerator. Given the high radiation in the vicinity of the foil, the uncertainty in the foil's emissivity, and available resources, we chose a two-wavelength pyrometer that is located 40 m from the foil. The pyrometer is composed of two mirrors, a refracting telescope, and two photodiodes. We present the calibration data and the temporally resolved measurements made with this pyrometer.

Slides TUP2WE01 [13.195 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE01

Export •

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

TUP2WE03

Radiation Damage Calculation in PHITS and Benchmarking Experiment for Cryogenic-Sample High-Energy Proton Irradiation

116

Y. Iwamoto, D. Satoh
JAEA, Ibaraki-ken, Japan
Y. Ishi, Y. Kuriyama, T. Uesugi, H. Yashima, T. Yoshiie
Kyoto University, Research Reactor Institute, Osaka, Japan
H. Matsuda, S.I. Meigo
JAEA/J-PARC, Tokai-mura, Japan
T. Nakamoto
KEK, Ibaraki, Japan
K. Niita
Research Organization for Information Science & Technology, Ibaraki, Japan
R.M. Ronningen
FRIB, East Lansing, Michigan, USA
T. Shima
RCNP, Osaka, Japan

Funding: The experimental study was supported by JSPS KAKENHI, Grant Number JP 16H04638 and 25820450. The calculation work was supported in part by the US National Science Foundation under grant PHY06-06007.
The radiation damage model in the Particle and Heavy Ion Transport code System (PHITS) has been developed using the screened Coulomb scattering to evaluate the energy of the target Primary Knock on Atom (PKA) created by the projectile and the secondary particles which include all particles created from the sequential nuclear reactions. For the high-energy proton incident reactions, a target PKA created by the secondary particles was more dominant than a target PKA created by the projectile. To validate prediction of DPA values in metals irradiated by >100 MeV protons, we developed a proton irradiation device with a Gifford-McMahon (GM) cryocooler to cryogenically cool wire samples. By using this device, the defect-induced electrical resistivity changes related to the DPA cross section of copper and aluminum were measured under irradiation with 125 and 200 MeV protons at cryogenic temperature. A comparison of the experimental DPA cross sections with the calculated results indicates that the athermal-recombination-corrected displacement damage (arc-dpa) provide better quantitative descriptions of the DPA cross section than NRT-dpa without defect production efficiencies.

Slides TUP2WE03 [4.747 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE03

Export •

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

TUP2WE04

Design of the Target Dump Injection Segmented (TDIS) in the Framework of the High Luminosity Large Hadron Collider (HL-LHC) Project

122

L. Teofili, D. Carbajo Perez, I. Lamas Garcia, M. Migliorati, A. Perillo
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy
M. Migliorati
Sapienza University of Rome, Rome, Italy

The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In this scenario most equipment has to be redesigned and rebuilt. In particular, beam intercepting devices (as dumps, collimators, absorbers and scrapers) have to withstand impact or scraping of the new intense HL-LHC beams without failures. Further, minimizing the electromagnetic beam-device interactions is also a key design driver since they can lead to beam instabilities and excessive thermo-mechanical loading of devices. In this context, the present study assesses the conceptual design quality of the new LHC injection dump, the Target Dump Injection Segmented (TDIS), from an electromagnetic and thermo-mechanical perspective. This contribution analyzes the thermo-mechanical response of the device considering two cases: an accidental beam impact scenario and another accidental scenario with complete failure of the RF-contacts. Further, this paper presents the preliminary results for the simulation of the energy deposited by the two counter-rotating beams circulating in the device.

Slides TUP2WE04 [10.895 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP2WE04

Export •

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

WEP2PO030

A 4D Emittance Measurement Device for the 870 keV HIPA Injection Line

329

R. Dölling, M. Rohrer
PSI, Villigen PSI, Switzerland

A 4D emittance measurement device has recently been installed in PSI's high intensity proton accelerator (HIPA) after the acceleration tube of the Cockcroft-Walton pre-accelerator. A pinhole collimator is moved 2D transversally and at each collimator position, the resulting beamlet is downstream scanned 2D by vertically moving over it a horizontal linear array of small electrodes. The properties of this setup and the intended use are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO030

Export •

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

WEP2PO032

A Secondary Emission Monitor in the SINQ Beam Line for Improved Target Protection

334

R. Dölling, M. Rohrer
PSI, Villigen PSI, Switzerland

A 4-strip secondary-emission monitor (SEM) has been installed in the beam line to the SINQ neutron source to detect irregular fractions of the megawatt proton beam which might damage the spallation target. We discuss the estimated performance of the monitor as well as its design and implementation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO032

Export •

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

WEP2PO033

A Test of Stripper Foil Lifetime in PSI's 72 MeV Proton Beam

338

R. Dölling, R. Dressler
PSI, Villigen PSI, Switzerland
L. Calabretta
INFN/LNS, Catania, Italy

A test of the lifetime of an amorphous carbon foil of ~79 ug/cm² was performed at PSI in the transfer line between Injector 2 and Ring cyclotron during the regularly beam production. The 72 MeV ~1.7 mA proton beam had a central current density of ~2.8 mA/cm². Two spots on the foil were irradiated alternatively with in total three fractions of 17, 52 and 119 mAh. Foil thickness was measured before and after irradiation at several positions via the energy loss of alpha-particles from a 241Am source in the foil. We discuss the observed foil damage as well as the experimental setup, the estimation of the beam parameters and practical boundary conditions.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO033

Export •

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

THA1WE01

New Electron Cloud Instability Mechanism and its Detection and Suppression

V.A. Lebedev
Fermilab, Batavia, Illinois, USA
S. A. Antipov
CERN, Geneva, Switzerland

Fast transverse instability was observed in Recycler proton storage ring (RR). The instability develops within 100 turns and may lead to beam loss. The fast rise suggested that the instability is driven by electron cloud. That was later supported by microwave transmission measurements. In difference to RR the instability was not observed in similar conditions in Main Injector (MI). RR is based on combined function dipoles while MI uses pure dipoles. This difference plays a key role in instability development. The instability dynamics was studied experimentally and with numerical simulations. An analytical model predicts that electrons are trapped in RR dipoles. Numerical simulations show that up to 1% of particles can be trapped. The cloud build-up is exponential with its density limited by space charge. That results in the cloud intensity orders of magnitude greater than in MI. A growth rate of about 30 turns and mode frequency of 0.4 MHz are consistent for observations and PEI simulations. The high intensity batch can be stabilized by low intensity clearing bunch injected behind batch which destroys the trapped electron cloud and prevents its multi-turn accumulation.

Slides THA1WE01 [7.328 MB]

Export •

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

THA1WE02

Requirements and Results for Quadrupole Mode Measurements

393

A. Oeftiger
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
Direct space charge may be quantified, and hence the beam brightness observed, by measuring the quadrupolar beam modes in the CERN Proton Synchrotron (PS). The spectrum of the transverse beam size oscillations (i.e. the quadrupolar beam moment) contains valuable information: the betatron envelope modes and the coherent dispersive mode indicate optics mismatch, while their frequency shifts due to space charge allow a direct measurement thereof. To measure the quadrupolar beam moment we use the Base-Band Q-meter system of the PS which is based on a four electrode stripline pick-up. Past experiments with quadrupolar pick-ups often investigated coasting beams, where the coherent betatron and dispersion modes correspond to single peaks in the tune spectrum. In contrast, long bunched beams feature bands of betatron modes: the mode frequencies shift depending on the transverse space charge strength which varies with the local line charge density. By using the new transverse feedback in the PS as a quadrupolar RF exciter, we measured the quadrupolar beam transfer function. The beam response reveals the distinct band structure of the envelope modes as well as the coherent dispersive mode.

Slides THA1WE02 [7.315 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE02

Export •

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

THA1WE03

BPM Technologies for Quadrupolar Moment Measurements

399

A. Sounas, M. Gąsior, T. Lefèvre
CERN, Geneva, Switzerland

Quadrupolar moment measurements based on electromagnetic pick-ups (PU), like BPMs, have attracted particular interest as non-intercepting diagnostics to determine the transverse beam size. Here, the second-order moment, which contains information about the beam size, is extracted from the BPM electrode signals. Despite the simplicity of the concept, quadrupololar measurements have always been challenging in practice. This is related to the fact that the quadrupolar moment constitutes only a very small part of the total PU signal, which is dominated by the contributions of beam intensity and position. In this study we discuss the limitations of absolute quadrupolar measurements if applying traditional BPM technologies, and we propose a new approach to efficiently overcome them via movable PUs. Moreover, we highlight the potential use of BPMs as an emittance measurement system during the energy ramp at synchrotrons by performing differential quadrupolar measurements, which show a remarkably higher accuracy than absolute measurements. Dedicated studies using different types of BPMs in the Large Hadron Collider (LHC) at CERN demonstrated promising results.

Slides THA1WE03 [5.299 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE03

Export •

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

THA1WE04

ESS nBLM: Beam Loss Monitors based on Fast Neutron Detection

404

T. Papaevangelou
CEA/IRFU, Gif-sur-Yvette, France
H. Alves, S. Aune, J. Beltramelli, Q. Bertrand, T. Bey, B. Bolzon, N. Chauvin, M. Combet, D. Desforge, M. Desmons, Y. Gauthier, E. Giner-Demange, A. Gomes, F. Gougnaud, F. Harrault, F. J. Iguaz Gutierrez, T.J. Joannem, M. Kebbiri, C. Lahonde-Hamdoun, P. Le Bourlout, Ph. Legou, O. Maillard, A. Marcel, C. Marchand, Y. Mariette, J. Marroncle, V. Nadot, M. Oublaid, G. Perreu, O. Piquet, B. Pottin, Y. Sauce, J. Schwindling, L. Segui, F. Senée, R. Touzery, G. Tsiledakis, O. Tuske, D. Uriot
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
I. Dolenc Kittelmann, R.J. Hall-Wilton, C. Höglund, L. Robinson, T.J. Shea, P. Svensson
ESS, Lund, Sweden
V. Gressier
IRSN, Saint-Paul-Lez-Durance, France
K. Nikolopoulos
Birmingham University, Birmingham, United Kingdom
M. Pomorski
CEA/DRT/LIST, Gif-sur-Yvette Cedex, France

A new type of Beam Loss Monitor (BLM) system is being developed for use in the European Spallation Source (ESS) linac, primarily aiming to cover the low energy part (proton energies between 3-100 MeV). In this region of the linac, typical BLM detectors based on charged particle detection (i.e. Ionization Cham-bers) are not appropriate because the expected particle fields will be dominated by neutrons and photons. Another issue is the photon background due to the RF cavities, which is mainly due to field emission from the electrons from the cavity walls, resulting in brems-strahlung photons. The idea for the ESS neutron sensi-tive BLM system (ESS nBLM) is to use Micromegas detectors specially designed to be sensitive to fast neutrons and insensitive to low energy photons (X and gammas). In addition, the detectors must be insensitive to thermal neutrons, because those neutrons may not be directly correlated to beam losses. The appropriate configuration of the Micromegas operating conditions will allow excellent timing, intrinsic photon back-ground suppression and individual neutron counting, extending thus the dynamic range to very low particle fluxes.

Slides THA1WE04 [3.267 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE04

Export •

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

THA2WE01

Bayesian Optimization for Online FEL Tuning at LCLS

J.P. Duris, M.W. McIntire, D.F. Ratner
SLAC, Menlo Park, California, USA
D. Dylan
UCSC, Santa Cruz, California, USA

The Linac Coherent Light Source changes configurations 2 to 5 times per day, necessitating fast tuning strategies to reduce setup time for successive experiments. To this end, we employ a Bayesian approach to transport optics tuning to quickly optimize groups of quadrupole magnets. The power of Bayesian optimization lies in its ability to employ a probability distribution to represent the most likely region of a control feature space to optimize an objective. A Gaussian process allows us to employ kernel learning to modify the Bayesian likelihood of the machine response from observed data and learned characteristics of the machine response with respect to the controlled parameters. We build Bayesian priors and response correlations from historical LCLS run data of FEL pulse energy versus quadrupole magnet strengths, and use this to simultaneously optimize quadrupoles. Here, we introduce Bayesian optimization with Gaussian processes, and then describe our approach to training the optimizer on historical LCLS data.

Slides THA2WE01 [2.511 MB]

Export •

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

THA2WE02

Application of Machine Learning for the IPM-Based Profile Reconstruction

410

M. Sapinski, R. Singh, D.M. Vilsmeier
GSI, Darmstadt, Germany
J.W. Storey
CERN, Geneva, Switzerland

One of the most reliable devices to measure the transverse beam profile in hadron machines is Ionization Profile Monitor (IPM). This type of monitor can work in two modes: collecting electrons or ions. Typically, for lower intensity beams, the ions produced by ionization of the rest gas are extracted towards a position-sensitive detector. Ion trajectories follow the external electric field lines, however the field of the beam itself also affects their movement leading to a deformation of the observed beam profile. Correction methods for this case are known. For high brightness beams, IPM configuration in which electrons are measured, is typically used. In such mode, an external magnetic field is often applied in order to confine the transverse movement of electrons. However, for extreme beams, the distortion of the measured beam profile can still be present. The dynamics of electron movement is more complex than in case of ions, therefore the correction of the profile distortion is more difficult. Investigation of this problem using a dedicated simulation tool and machine learning algorithms lead to a beam profile correction methods for electron-collecting IPMs.

Slides THA2WE02 [7.357 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA2WE02

Export •

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