IPAC2014 - Classification: 04 Hadron Accelerators / T19 Collimation

Paper	Title	Page
MOPRI104	Measurement of Beam Ioniziation Loss in SIS18	864
	L.H.J. Bozyk, P.J. Spiller GSI, Darmstadt, Germany
	In the heavy ion synchrotron SIS18 at GSI an ion catcher system has been installed to provide low desorption surfaces for ionization beam loss to reduce dynamic vacuum effects. Medium charge state heavy ions can change their charge state in collission with residual gas molecules. Those ions are cought by the ion catcher system. The ion catcher blocks are mounted electrically insulated, such that it is possible, to directly measure the electrical current, induced by the incident ions. Changes in vacuum density during the acceleration cycle and also the energy dependent decrease of the cross sections for electron loss and electron capture can be measured by this system. Different ion catcher currents, measured during the operation with U²⁸⁺, and their interpretation are presented. The measurement of ionization beam loss is a valuable tool to benchmark the dynamic vacuum simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI104
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MOPRI105	Heavy Ion Induced Desorption Measurements on Cryogenic Targets	867
SUSPSNE045	use link to see paper's listing under its alternate paper code
	Ch. Maurer, D.H.H. Hoffmann TU Darmstadt, Darmstadt, Germany L.H.J. Bozyk, H. Kollmus, Ch. Maurer, P.J. Spiller GSI, Darmstadt, Germany
	Funding: Bundesministerium für Bildung und Forschung FKZ 06DA7031 Heavy-ion impact induced gas desorption is the key process that drives beam intensity limiting dynamic vacuum losses. Minimizing this effect, by providing low desorption yield surfaces, is an important issue for maintaining a stable ultra high vacuum during operation with medium charge state heavy ions. For room temperature targets, investigation shows a scaling of the desorption yield with the beam's near-surface electronic energy loss, i.e. a decrease with increasing energy,. An optimized material for a room temperature ion-catcher has been found. But for the planned superconducting heavy-ion synchrotron SIS100 at the FAIR accelerator complex, the ion catcher system has to work in a cryogenic environment. Desorption measurements with the prototype cryocatcher for SIS100 showed an unexpected energy scaling*, which needs to be explained. Understanding this scaling might lead to a better suited choice of material, resulting in a lower desorption yield. An experimental setup for systematic examination of this scaling is presented. The cryogenic beam-induced desorption yield of several materials at different temperatures is examined. H. Kollmus et al., AIP Conf. Proc. 773, 207 (2005)) E. Mahner et al., Phys. Rev. ST Accel. Beams 14, 050102 (2011) * L.H.J. Bozyk, H. Kollmus, P.J. Spiller, Proc. of IPAC 2012, p. 3239
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MOPRI106	Simulation Study of Beam Halo Collimation in the Heavy-ion Synchrotron SIS 100	870
SUSPSNE047	use link to see paper's listing under its alternate paper code
	I.A. Prokhorov TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim, I. Strašík GSI, Darmstadt, Germany
	Funding: Work is supported by German Federal Ministry of Education and Research (BMBF) contract no. 05P12RDRBM The FAIR synchrotron SIS-100 will be operated with high-intensity proton and heavy-ion beams. The collimation system should prevent beam loss induced degradation of the vacuum, activation of the accelerator structure and magnet quenches. A conventional two-stage betatron collimation system is considered for the operation with protons and fully-stripped ions. Particle tracking and ion-collimator interaction simulations of the collimation system were performed. The angular and momentum distributions of the scattered halo particles were described using analytical models and numerical tools like ATIMA and FLUKA. MADX was used for the multi-pass tracking simulations. The results obtained for the collimation cleaning efficiency as a function of the ion species and beam energy together with the detailed beam losses distributions along the ring circumference are presented. This work highlights the main aspects of the collimation of fully-stripped ion beams in the intermediate energy range using conventional two-stage systems.
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MOPRI107	The Mitigation System of the Large Angle Foil Scattering Beam Loss caused by the Multi-turn Charge-exchange Injection	873
	S. Kato Tohoku University, Graduate School of Science, Sendai, Japan H. Harada, H. Hotchi, M. Kinsho, K. Yamamoto JAEA/J-PARC, Tokai-mura, Japan
	Funding: Research Fellow of Japan Society for the Promotion of Science In the J-PARC RCS, the significant losses were observed at the branch of H⁰ dump line and the Beam Position Monitor which was put at the downstream of the H⁰ dump branch duct. These losses were caused by the large angle scattering of the injection and the circulating beam at the charge exchange foil. To realize high power operation, we have to mitigate these losses. So, we developed a new collimation system in the H⁰ branch duct and installed in October 2011. In order to optimize this system efficiently, we focused on the relative angle of collimator block from scattering particles. We developed the beam based angler regulation method by the simulation and achieved the sufficient mitigation of the loss at 181 MeV injection energy. Since the injection energy will be upgraded to 400 MeV in this year, we will start to estimate again the collimator performance by the upgraded simulation set. We present this system as one of the mitigation methods of the large angle foil scattering beam loss caused by the multi-turn charge-exchange injection.
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MOPRI108	Transverse H⁻ Beam Halo Scraper System in the J-PARC L3BT	876
	K. Okabe, M. Kinsho, K. Yamamoto, M. Yoshimoto JAEA/J-PARC, Tokai-mura, Japan
	In the Japan Proton Accelerator Research Complex (J-PARC) 3-GeV rapid cycle synchrotron (RCS), transverse beam halo scraping for the injection beam is required to increase the output beam power. The transverse collimation system at the Linac-RCS beam transport line (L3BT) was utilized in a nominal beam operation because the area of the scraper section was contaminated when scrapers were working. In the summer-autumn period of 2013, we installed a new beam-halo scraper which had optimized scraper heads for mitigation of the radiation around the scraper system. In this poster, we report a preliminary result for a halo scraper at the L3BT.
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MOPRI109	High-Power Proton-Synchrotron Collimation Studies	879
	A. Alekou, Y. Papaphilippou CERN, Geneva, Switzerland D. Spitzbart TU Vienna, Wien, Austria
	The High-Power Proton-Synchrotron (HP-PS) will be delivering a 2 MW proton beam to a fixed target in order to produce neutrinos within the LAGUNA-LBNO project. A mechanical collimation system is essential to prevent lost particles from hitting the super-feric dipoles of the HP-PS ring and to also limit the equipment irradiation close to the beam. This paper presents how the efficiency of the HP-PS collimator system is optimised with respect to the change of the collimators’ thickness, material and beam halo size.
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MOPRI110	Final Layout and Expected Cleaning for the First Crystal-assisted Collimation Test at the LHC	882
SUSPSNE046	use link to see paper's listing under its alternate paper code
	D. Mirarchi, S. Montesano, S. Redaelli, W. Scandale CERN, Geneva, Switzerland F. Galluccio INFN-Napoli, Napoli, Italy A.M. Taratin JINR, Dubna, Moscow Region, Russia
	The installation in the CERN Large Hadron Collider (LHC) of two crystals in the horizontal and vertical planes was accomplished during the present LHC long shutdown (LS1) for crystal collimation studies. An appropriate layout was designed to demonstrate the principle feasibility of crystal collimation at the LHC. Extensive simulation campaigns were made to evaluate different crystal positions and parameters, in order to ensure that the main goals of these first feasibility tests in the LHC are within reach. In this paper, the final layout is presented. An overview of the considerations behind the design choices and the crystal parameters is given, and the expected performance of the system is discussed.
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MOPRI111	Improvements of the Crystal Routine for Collimation Studies	886
	D. Mirarchi, S. Redaelli, W. Scandale CERN, Geneva, Switzerland A.M. Taratin JINR, Dubna, Moscow Region, Russia I.A. Yazynin IHEP, Moscow Region, Russia
	A routine has been implemented to simulate interactions of protons with bent crystals in the collimation version of \texttt{SixTrack}. This routine is optimized in view of producing high-statistics tracking simulations of collimation cleaning assisted by bent crystals. Fine tuning and comparisons with experimental data of coherent effects which a particle can experience in a bent crystal have been carried out. The data taken with 400 GeV beams at the CERN-SPS North Area in the framework of the UA9 experiment are used to benchmark the routine. Further checks on low probability interactions have been made, leading to significant improvements in the description of interactions with crystals. Comparisons with other simulations tools are used to increase our confidence in the scaling to higher energies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI111
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MOPRI114	Numerical Estimation of the Equivalent Dose Rate after the Irradiation of a Tungsten Collimator by a Low Energy Proton Beam	890
	V. Talanov, D.C. Kiselev, M. Wohlmuther PSI, Villigen PSI, Switzerland
	The issue of activation of a Tungsten collimator by protons is considered for the incident energy of 12.2 MeV. Two different simulation approaches using the Monte Carlo programs MCNPX and FLUKA are applied to estimate the equivalent remanent dose rate after the irradiation of the collimator. The results of the numerical simulation are then compared to the measured dose levels of the collimator of the COMET cyclotron at Paul Scherrer Institut (PSI).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI114
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MOPRI115	Activation Models of the ISIS Collectors	893
	H. V. Smith, D.J. Adams, B. Jones, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The ISIS facility at the Rutherford Appleton Laboratory is a pulsed neutron and muon source, for materials and life science research. The 163 m circumference, 800 MeV, 50 Hz rapid cycling synchrotron accelerates up to 3·10¹³ protons per pulse. The maximum operating intensity of the synchrotron is limited by loss during acceleration, mainly due to the non-adiabatic longitudinal trapping process between 0 and 3 ms, corresponding to energies between 70 and 200 MeV. In order to minimise global machine activation and prevent component damage a beam collimation, or collector, system is installed in a five metre drift section in super-period one, to localise loss to this region. This paper summarises new results from modelling of the beam collectors using the FLUKA code [1, 2]. Understanding the current performance of the collectors is important for high intensity beam optimisation and may influence future injection upgrade plans. Residual dose rates are compared to film badge measurements, predicted energy deposition results are compared to the measured heat load on the collector cooling systems and an assessment is made of the distribution of particles exiting the collector straight.
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Paper

Title

Page

Measurement of Beam Ioniziation Loss in SIS18

864

L.H.J. Bozyk, P.J. Spiller
GSI, Darmstadt, Germany

In the heavy ion synchrotron SIS18 at GSI an ion catcher system has been installed to provide low desorption surfaces for ionization beam loss to reduce dynamic vacuum effects. Medium charge state heavy ions can change their charge state in collission with residual gas molecules. Those ions are cought by the ion catcher system. The ion catcher blocks are mounted electrically insulated, such that it is possible, to directly measure the electrical current, induced by the incident ions. Changes in vacuum density during the acceleration cycle and also the energy dependent decrease of the cross sections for electron loss and electron capture can be measured by this system. Different ion catcher currents, measured during the operation with U²⁸⁺, and their interpretation are presented. The measurement of ionization beam loss is a valuable tool to benchmark the dynamic vacuum simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI104

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MOPRI105

Heavy Ion Induced Desorption Measurements on Cryogenic Targets

867

SUSPSNE045

use link to see paper's listing under its alternate paper code

Ch. Maurer, D.H.H. Hoffmann
TU Darmstadt, Darmstadt, Germany
L.H.J. Bozyk, H. Kollmus, Ch. Maurer, P.J. Spiller
GSI, Darmstadt, Germany

Funding: Bundesministerium für Bildung und Forschung FKZ 06DA7031
Heavy-ion impact induced gas desorption is the key process that drives beam intensity limiting dynamic vacuum losses. Minimizing this effect, by providing low desorption yield surfaces, is an important issue for maintaining a stable ultra high vacuum during operation with medium charge state heavy ions. For room temperature targets, investigation shows a scaling of the desorption yield with the beam's near-surface electronic energy loss, i.e. a decrease with increasing energy*,**. An optimized material for a room temperature ion-catcher has been found. But for the planned superconducting heavy-ion synchrotron SIS100 at the FAIR accelerator complex, the ion catcher system has to work in a cryogenic environment. Desorption measurements with the prototype cryocatcher for SIS100 showed an unexpected energy scaling***, which needs to be explained. Understanding this scaling might lead to a better suited choice of material, resulting in a lower desorption yield. An experimental setup for systematic examination of this scaling is presented. The cryogenic beam-induced desorption yield of several materials at different temperatures is examined.
* H. Kollmus et al., AIP Conf. Proc. 773, 207 (2005))
** E. Mahner et al., Phys. Rev. ST Accel. Beams 14, 050102 (2011)
*** L.H.J. Bozyk, H. Kollmus, P.J. Spiller, Proc. of IPAC 2012, p. 3239

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI105

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MOPRI106

Simulation Study of Beam Halo Collimation in the Heavy-ion Synchrotron SIS 100

870

SUSPSNE047

use link to see paper's listing under its alternate paper code

I.A. Prokhorov
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim, I. Strašík
GSI, Darmstadt, Germany

Funding: Work is supported by German Federal Ministry of Education and Research (BMBF) contract no. 05P12RDRBM
The FAIR synchrotron SIS-100 will be operated with high-intensity proton and heavy-ion beams. The collimation system should prevent beam loss induced degradation of the vacuum, activation of the accelerator structure and magnet quenches. A conventional two-stage betatron collimation system is considered for the operation with protons and fully-stripped ions. Particle tracking and ion-collimator interaction simulations of the collimation system were performed. The angular and momentum distributions of the scattered halo particles were described using analytical models and numerical tools like ATIMA and FLUKA. MADX was used for the multi-pass tracking simulations. The results obtained for the collimation cleaning efficiency as a function of the ion species and beam energy together with the detailed beam losses distributions along the ring circumference are presented. This work highlights the main aspects of the collimation of fully-stripped ion beams in the intermediate energy range using conventional two-stage systems.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI106

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MOPRI107

The Mitigation System of the Large Angle Foil Scattering Beam Loss caused by the Multi-turn Charge-exchange Injection

873

S. Kato
Tohoku University, Graduate School of Science, Sendai, Japan
H. Harada, H. Hotchi, M. Kinsho, K. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan

Funding: Research Fellow of Japan Society for the Promotion of Science
In the J-PARC RCS, the significant losses were observed at the branch of H⁰ dump line and the Beam Position Monitor which was put at the downstream of the H⁰ dump branch duct. These losses were caused by the large angle scattering of the injection and the circulating beam at the charge exchange foil. To realize high power operation, we have to mitigate these losses. So, we developed a new collimation system in the H⁰ branch duct and installed in October 2011. In order to optimize this system efficiently, we focused on the relative angle of collimator block from scattering particles. We developed the beam based angler regulation method by the simulation and achieved the sufficient mitigation of the loss at 181 MeV injection energy. Since the injection energy will be upgraded to 400 MeV in this year, we will start to estimate again the collimator performance by the upgraded simulation set. We present this system as one of the mitigation methods of the large angle foil scattering beam loss caused by the multi-turn charge-exchange injection.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI107

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MOPRI108

Transverse H⁻ Beam Halo Scraper System in the J-PARC L3BT

876

K. Okabe, M. Kinsho, K. Yamamoto, M. Yoshimoto
JAEA/J-PARC, Tokai-mura, Japan

In the Japan Proton Accelerator Research Complex (J-PARC) 3-GeV rapid cycle synchrotron (RCS), transverse beam halo scraping for the injection beam is required to increase the output beam power. The transverse collimation system at the Linac-RCS beam transport line (L3BT) was utilized in a nominal beam operation because the area of the scraper section was contaminated when scrapers were working. In the summer-autumn period of 2013, we installed a new beam-halo scraper which had optimized scraper heads for mitigation of the radiation around the scraper system. In this poster, we report a preliminary result for a halo scraper at the L3BT.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI108

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MOPRI109

High-Power Proton-Synchrotron Collimation Studies

879

A. Alekou, Y. Papaphilippou
CERN, Geneva, Switzerland
D. Spitzbart
TU Vienna, Wien, Austria

The High-Power Proton-Synchrotron (HP-PS) will be delivering a 2 MW proton beam to a fixed target in order to produce neutrinos within the LAGUNA-LBNO project. A mechanical collimation system is essential to prevent lost particles from hitting the super-feric dipoles of the HP-PS ring and to also limit the equipment irradiation close to the beam. This paper presents how the efficiency of the HP-PS collimator system is optimised with respect to the change of the collimators’ thickness, material and beam halo size.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI109

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MOPRI110

Final Layout and Expected Cleaning for the First Crystal-assisted Collimation Test at the LHC

882

SUSPSNE046

use link to see paper's listing under its alternate paper code

D. Mirarchi, S. Montesano, S. Redaelli, W. Scandale
CERN, Geneva, Switzerland
F. Galluccio
INFN-Napoli, Napoli, Italy
A.M. Taratin
JINR, Dubna, Moscow Region, Russia

The installation in the CERN Large Hadron Collider (LHC) of two crystals in the horizontal and vertical planes was accomplished during the present LHC long shutdown (LS1) for crystal collimation studies. An appropriate layout was designed to demonstrate the principle feasibility of crystal collimation at the LHC. Extensive simulation campaigns were made to evaluate different crystal positions and parameters, in order to ensure that the main goals of these first feasibility tests in the LHC are within reach. In this paper, the final layout is presented. An overview of the considerations behind the design choices and the crystal parameters is given, and the expected performance of the system is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI110

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MOPRI111

Improvements of the Crystal Routine for Collimation Studies

886

D. Mirarchi, S. Redaelli, W. Scandale
CERN, Geneva, Switzerland
A.M. Taratin
JINR, Dubna, Moscow Region, Russia
I.A. Yazynin
IHEP, Moscow Region, Russia

A routine has been implemented to simulate interactions of protons with bent crystals in the collimation version of \texttt{SixTrack}. This routine is optimized in view of producing high-statistics tracking simulations of collimation cleaning assisted by bent crystals. Fine tuning and comparisons with experimental data of coherent effects which a particle can experience in a bent crystal have been carried out. The data taken with 400 GeV beams at the CERN-SPS North Area in the framework of the UA9 experiment are used to benchmark the routine. Further checks on low probability interactions have been made, leading to significant improvements in the description of interactions with crystals. Comparisons with other simulations tools are used to increase our confidence in the scaling to higher energies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI111

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MOPRI114

Numerical Estimation of the Equivalent Dose Rate after the Irradiation of a Tungsten Collimator by a Low Energy Proton Beam

890

V. Talanov, D.C. Kiselev, M. Wohlmuther
PSI, Villigen PSI, Switzerland

The issue of activation of a Tungsten collimator by protons is considered for the incident energy of 12.2 MeV. Two different simulation approaches using the Monte Carlo programs MCNPX and FLUKA are applied to estimate the equivalent remanent dose rate after the irradiation of the collimator. The results of the numerical simulation are then compared to the measured dose levels of the collimator of the COMET cyclotron at Paul Scherrer Institut (PSI).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI114

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MOPRI115

Activation Models of the ISIS Collectors

893

H. V. Smith, D.J. Adams, B. Jones, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

The ISIS facility at the Rutherford Appleton Laboratory is a pulsed neutron and muon source, for materials and life science research. The 163 m circumference, 800 MeV, 50 Hz rapid cycling synchrotron accelerates up to 3·10¹³ protons per pulse. The maximum operating intensity of the synchrotron is limited by loss during acceleration, mainly due to the non-adiabatic longitudinal trapping process between 0 and 3 ms, corresponding to energies between 70 and 200 MeV. In order to minimise global machine activation and prevent component damage a beam collimation, or collector, system is installed in a five metre drift section in super-period one, to localise loss to this region. This paper summarises new results from modelling of the beam collectors using the FLUKA code [1, 2]. Understanding the current performance of the collectors is important for high intensity beam optimisation and may influence future injection upgrade plans. Residual dose rates are compared to film badge measurements, predicted energy deposition results are compared to the measured heat load on the collector cooling systems and an assessment is made of the distribution of particles exiting the collector straight.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI115

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