04 Hadron Accelerators
T12 Beam Injection/Extraction and Transport
Paper Title Page
TUPAF027 CERN PS Kicker for Proton Injection: from Beam-Based Waveform Measurements to Hardware Improvements 732
  • V. Forte, A. Ferrero Colomo, M.A. Fraser, T. Kramer
    CERN, Geneva, Switzerland
  For 2017 operation, the termination mode of the CERN Proton Synchrotron (PS) horizontal injection kicker was permanently changed to short-circuited, to be compliant with the future performances requested by the LHC Injectors Upgrade (LIU) project. An extensive campaign of measurements was performed through a dedicated beam-based technique. The measurements identified possibilities for optimisation of the kicker system and were fundamental to properly tune the PSpice simulation model of the kicker, as well as for validating the hardware changes. The model was finally used to estimate the horizontal emittance growth for the future injection schemes in the PS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF027  
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TUPAF028 Energy Deposition Studies and Analysis of the Quench Behavior in the Case of Asynchronous Dumps During 6.5 TeV LHC Proton Beam Operation 736
  • M.I. Frankl, W. Bartmann, M. Bednarek, C. Bracco, A. Lechner, A.P. Verweij, C. Wiesner, D. Wollmann
    CERN, Geneva, Switzerland
  The CERN LHC beam dumping system comprises a series of septa and fast-pulsed kicker magnets for extracting the stored proton beams to the external beam dumps. Different absorbers in the extraction region protect superconducting magnets and other machine elements in case of abnormal beam aborts, where bunches are swept across the machine aperture. During Run 2 of the LHC, controlled beam loss experiments were carried out at 6.5 TeV probing the particle leakage from protection devices under realistic operation conditions. This paper presents particle shower simulations analyzing the energy deposition in superconducting coils and assessing if the observed magnet quenches are compatible with the presently known quench limits.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF028  
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TUPAF031 Beam Simulation Studies for the Upgrade of the SPS Beam Dumping System 747
  • C. Heßler, W. Bartmann, E. Carlier, L. Ducimetière, B. Goddard, F.M. Velotti
    CERN, Geneva, Switzerland
  The SPS at CERN currently uses a beam dumping system that is installed in the long straight section 1 (LSS1) of the SPS. This system consists of two beam stopper blocks for low and high energy beams, as well as two vertical and three horizontal kicker magnets, which deflect and dilute the beam on the dumps. Within the frame of the LHC injector upgrade project (LIU) the beam dumping system will be relocated to long straight section 5 (LSS5) and upgraded with an additional vertical kicker, new main switches and a single new beam dump, which covers the full energy range. The impact of a possible increase of the vertical kicker rise time on the beam has been studied in simulations with MAD-X for the different optics in the SPS. Furthermore, the impact on the beam in failure scenarios such as the non-firing of one kicker has been investigated. The results of these studies will be presented and discussed in this paper. Operational mitigation methods to deal with an increased rise time will also be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF031  
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TUPAF032 Beam Transfer Line Design to the SPS Beam Dump Facility 751
  • Y. Dutheil, J. Bauche, M. Calviani, L.A. Dougherty, M.A. Fraser, B. Goddard, C. Heßler, J. Kurdej, E. Lopez Sola
    CERN, Geneva, Switzerland
  Studies for the SPS Beam Dump Facility (BDF) are ongoing within the scope of the Physics Beyond Collider project. The BDF is a proposed fixed target facility to be installed in the SPS North Area, to accommodate the SHiP experiment (Search for Hidden Particles), which is most notably aiming at studying hidden sector particles. This experiment requires a high intensity slowly extracted 400 GeV proton beam with 4·1013 protons per 1 s spill to achieve 4·1019 protons on target per year. The extraction and transport scheme will make use of the first 600 m of the existing North Area extraction line. In this paper, we will present the design of the additional 600 m of transfer line towards BDF branching off from the existing line and discuss the detailed design of the BDF beam line, its components and optics. We present the latest results on the study and design of a new laminated Lambertson splitter magnet to provide fast switch between the current North Area experiments and the BDF. The latest specification of a dipole dilution system used to reduce the local peak power of the beam on the target is also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF032  
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TUPAF033 Beam Optics Studies for BDF and for Tests of a Prototype Target 754
  • C. Heßler, M. Calviani, Y. Dutheil, M.A. Fraser, B. Goddard, V. Kain, E. Lopez Sola, F.M. Velotti
    CERN, Geneva, Switzerland
  Within the frame of the Physics Beyond Collider project a new fixed target facility at the SPS North Area, the so-called Beam Dump Facility (BDF), is under study. BDF requires a high intensity slowly extracted 400 GeV proton beam with 4·1013 protons per 1 s spill to achieve 4·1019 protons on target per year. This results in an exceptionally high average beam power of 355 kW on the target, which is a major challenge. To validate the target design, a test of a prototype target is planned for 2018 at an existing North Area beam line. A large part of this beam line is in common with the future BDF beam line with comparable beam characteristics and several measurement campaigns were performed in 2017 to study the optics of the line in preparation for the test. The intrinsic characteristics of the slow extraction process make the precise characterisation of the beam reaching the target particularly challenging. This paper presents beam and lattice characterisation methods and associated measurement results.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF033  
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TUPAF035 Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements 761
  • F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari
    CERN, Geneva, Switzerland
  The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF035  
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TUPAF037 Validation of the CERN PS Eddy Current Injection Septa 768
  • M. Hourican, B. Balhan, J.C.C.M. Borburgh, T. Masson, A. Sanz Ull
    CERN, Geneva, Switzerland
  As part of the upgrade of the CERN PS accelerator from 1.4 GeV to 2 GeV, new injection septa have been developed. The system is comprised of a pulsed eddy current septum magnet and a pulsed eddy current bumper magnet. Both magnets will be housed in a common vacuum vessel and powered by independent power converters. In-depth studies and simulations have been performed to reduce as much as possible the leak field by designing specific magnetic shielding, combined with dual function beam impedance shielding. A prototype magnet was built and measured to validate the simulations. The final complete system will be bake-able at 200C and uses demineralised water for cooling. Closed circuit cooling systems have been integrated to reduce risks of vacuum leaks. This report describes the electromechanical design from the concept and simulation stages to the prototyping and final manufacturing. Results of the initial magnetic measurements, including field homogeneity and leak field mitigation methods are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF037  
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TUPAF050 Beam Dynamics Simulations of the Effect of Power Converter Ripple on Slow Extraction at the CERN SPS 818
  • J. Prieto, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
  The SPS provides slowly extracted protons at 400 GeV/c to CERN's North Area Fixed Target experiments over spills of duration from 1-10 seconds. Low frequency ripple on the current in the main magnets originating from their power converters is a common issue that degrades the slow-extracted spill quality. In order to better understand how the stability of the power converters affects losses, beam emittance and spill quality, particle tracking simulations were carried out using MAD-X and compared to measurements, with the impact of each magnet circuit investigated systematically. The implications for the performance of the SPS slow extraction are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF050  
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TUPAF051 Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS 822
SUSPF060   use link to see paper's listing under its alternate paper code  
  • L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard
    CERN, Geneva, Switzerland
  • K.A. Brown
    BNL, Upton, Long Island, New York, USA
  Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF051  
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TUPAF052 Effects of Electrostatic Septum Alignment on Particle Loss During Slow Extraction at CERN SPS 826
  • J. Prieto, Y. Dutheil, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
  • M.A. Kagan
    SLAC, Menlo Park, California, USA
  Slow extraction is an intrinsically lossy process that splits the beam with an electrostatic septum (ES), employing a thin-wire array to delimit the high electric field region that deflects the beam into the extraction channel. At CERN's Super Proton Synchrotron (SPS) the ES is over 16 m long and composed of 5 separate units containing separate wire-arrays that can be moved independently. The tanks are all mounted on a single support structure that can move the ensemble coherently. As a result, the large number of positional degrees of freedom complicates the alignment procedure in operation. Obtaining and maintaining accurate alignment of the ES with the beam is therefore crucial for minimising beam loss. In this paper, we investigate the alignment procedure for different operational scenarios using particle tracking simulations to understand the beam loss along the extraction straight as a function of the relative positions of each of the 5 separate ES units. An important aspect of the study was to understand the required alignment tolerance to achieve optimum extraction efficiency for a given configuration of wire-array thicknesses.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF052  
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TUPAF053 Optimization of Diffuser (Pre-Scatterer) Configurations for Slow Extraction Loss Reduction at Electrostatic Septa 830
  • B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.O. Jorat, V. Kain, C. Lolliot, L.S. Stoel, P. Van Trappen, F.M. Velotti
    CERN, Geneva, Switzerland
  • D. Barna
    Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
  • V.P. Nagaslaev
    Fermilab, Batavia, Illinois, USA
  Uncontrolled beam loss at the electrostatic septum is a performance limit for several existing or planned high power hadron accelerators delivering slow-extracted spills to fixed targets. A passive diffuser, or pre-scatterer, in a suitable configuration has been shown to reduce such beamloss significantly, with the actual gain factor depending on the parameters and details of the extraction process and hardware. In this paper, the optimization of diffuser configurations is investigated for a range of beam energies and extraction conditions, and the sensitivity to the available parameters explored via simulation results. The advantages and limitations of the diffuser are discussed and conclusions drawn concerning the specific case studies of the 8 GeV Fermilab debuncher ring and 400 GeV CERN SPS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF053  
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TUPAF054 Slow Extraction Efficiency Measurements at the CERN SPS 834
  • M.A. Fraser, K. Cornelis, L.S. Esposito, B. Goddard, V. Kain, F. Roncarolo, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
  The high efficiency of most slow extraction systems makes quantifying the exact amount of beam lost in the process extremely challenging. This is compounded by the lack of time structure in the extracted beam, as is typically required by the high-energy physics experiments, and the difficulty in accurately calibrating D.C. intensity monitors in the extraction line at count rates of ~ 1013 Hz. As a result, it is common for the extraction inefficiency to be measured by calibrating the beam loss signal induced by the slow extraction process itself. In this paper, measurements of the extraction efficiency performed at the CERN Super Proton Synchrotron for the third-integer resonant slow extraction of 400 GeV protons over recent years will be presented and compared to expectation from simulation. The technique employed will be discussed along with its limitations and an outlook towards a future online extraction efficiency monitoring system will be given.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF054  
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TUPAF055 Progress Toward a Dynamic Extraction Bump for Slow Extraction in the CERN SPS 838
  • L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard, J. Prieto, F.M. Velotti
    CERN, Geneva, Switzerland
  The possibility of reducing the angular spread of slow extracted particles with a time-dependent extraction bump at the CERN Super Proton Synchrotron (SPS) is under investigation. In order to create this so-called dynamic bump, two orthogonal knobs were designed to enable independent movements of the beam in position and angle at the upstream end of the electrostatic extraction septum (ES). With the present slow extraction scheme, simulations show that the use of a dynamic bump can reduce the angular spread at the ES by roughly a factor two and reduce beam loss on the ES. A reduction in the angular spread is also a prerequisite to exploit the full potential of other loss reduction techniques being considered for implementation at the SPS, like the active or passive diffusers planned for installation upstream of the ES in 2018. In this paper, the simulated loss reduction with a dynamic bump alone or in combination with other loss reduction techniques will be assessed, the first beam-based tests of the dynamic bump presented, the details of its implementation examined and its potential for future operation at the SPS discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF055  
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TUPAF058 Optimization of the FCC-hh Beam Extraction System Regarding Failure Avoidance and Mitigation 850
  • E. Renner, M.J. Barnes, W. Bartmann, F. Burkart, E. Carlier, L. Ducimetière, B. Goddard, T. Kramer, A. Lechner, N. Magnin, V. Senaj, J.A. Uythoven, P. Van Trappen, C. Wiesner
    CERN, Geneva, Switzerland
  A core part of the Future Circular Collider (FCC) study is a high energy hadron-hadron collider with a circumference of nearly 100~km and a center of mass beam energy of 100~TeV. The energy stored in one beam at top energy is 8.3~GJ, more than 20 times that of the LHC beams. Due to the large damage potential of the FCC-hh beam, the design of the beam extraction system is dominated by machine protection considerations and the requirement of avoiding any material damage in case of an asynchronous beam dump. Erratic operation of one or more extraction kickers is a main contributor to asynchronous beam dumps. The presented study shows ways to reduce the probability and mitigate the impact of erratic kicker switching. Key proposals to achieve this include layout considerations, different hardware options and alternative reaction strategies in case of erratic extraction kicker occurrence. Based on these concepts, different solutions are evaluated and an optimized design for the FCC-hh extraction system is proposed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF058  
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TUPAF059 Design and Evaluation of FCC-hh Injection Protection Schemes 854
  • E. Renner, M.J. Barnes, W. Bartmann, C. Bracco, R. Bruce, F. Burkart, B. Goddard, A. Lechner, L.S. Stoel, F.M. Velotti, C. Wiesner, D. Woog
    CERN, Geneva, Switzerland
  The Future Circular Collider (FCC) study considers several injector scenarios for FCC-hh, the proposed 100~TeV centre of mass hadron collider located at CERN. The investigated options include amongst others to use the LHC at 3.3~TeV or a superconducting SPS at 1.3~TeV as a High Energy Booster (HEB). Due to the high energy of the injected proton beam and the short time constant of injection failures, a thorough consideration of potential failure cases is of major importance. Further attention has to be given to the fact that the injection is - as in LHC - located upstream of the side experiments. Failure scenarios are identified for both injector options, appropriate designs of injection protection schemes are proposed and first simulations are conducted to validate the protection efficiency.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF059  
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TUPAF060 Injection and Dump Systems for a 13.5 TeV Hadron Synchrotron HE-LHC 858
  • W. Bartmann, M.J. Barnes, L. Ducimetière, B. Goddard, M. Hofer, T. Kramer, A. Lechner, E. Renner, A. Sanz Ull, V. Senaj, L.S. Stoel, C. Wiesner
    CERN, Geneva, Switzerland
  One option for a future circular collider at CERN is to build a 13.5 TeV hadron synchrotron, or High Energy LHC (HE-LHC) in the LHC tunnel. Injection and dump systems will have to be upgraded to cope with the higher beam rigidity and increased damage potential of the beam. The required modifications of the beam transfer hardware are highlighted in view of technology advancements in the field of kicker switch technology. An optimised straight section optics is shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF060  
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TUPAF061 Use of a Massless Septum to Increase Slow-Extraction Efficiency 862
  • K. Brunner, M.A. Fraser, B. Goddard, L.S. Stoel, C. Wiesner
    CERN, Geneva, Switzerland
  • D. Barna
    Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
  The Super Proton Synchrotron (SPS) at CERN provides slow-extracted beam for Fixed Target experiments in the North Area. For the higher extracted beam intensities requested by future experimental proposals, beam-loss induced activation will be one of the limiting factors for the availability of such a facility. In this paper, we present and discuss the concept of using a massless septum magnet to increase the extraction efficiency and decrease losses caused by protons scattering on the electrostatic-septa wires.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF061  
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TUPAF062 Parametric Study of the Beam Footprint Characteristics on the ESS Target 866
  • R. Miyamoto
    ESS, Lund, Sweden
  • H.D. Thomsen
    ISA, Aarhus, Denmark
  The beam delivery system of the ESS linac utilizes fast oscillating triangular wave dipole magnets of two transverse planes (raster magnets) to spray each long beam pulse (2.86 ms) over a rectangular cross-check pattern on the target. The characteristics of this beam footprint on the target are determined by the amplitudes of the raster magnets, RMS sizes of the beam and, in some case, the tail of the beam profile and have to satisfy the requirements from the target for the peak density as well as the fraction outside of a given rectangular boundary. This paper presents approximate closed-form expressions for the characteristics of the beam footprint and, based on the presented expressions, explores the parameter space of the raster magnets and beam parameters for achieving the optimal characteristics of the beam footprint.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF062  
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TUPAK010 The Development of a New Low Field Septum Magnet System for Fast Extraction in Main Ring of J-PARC 981
  • T. Shibata, K. Ishii, H. Matsumoto, T. Sugimoto
    KEK, Ibaraki, Japan
  • K. Fan
    HUST, Wuhan, People's Republic of China
  The J-PARC Main Ring (MR) is being upgraded to improve its beam power to the design goal of 750 kW. One important way is to reduce the repetition period from 2.48 s to 1.3 s so that the beam power can be nearly doubled. We need to improve the septum magnets for fast extraction. We are improving the magnets and their power supplies. The present magnets which are conventional type have problem in durability of septum coil by its vibration, and large leakage field at the flange of the beam duct. The new magnets are eddy current type. The eddy current type does not have septum coil, but has a thin plate. We expect that there is no problem in durability, we can construct the thin septum plate, the leakage field can be reduced. The output of the present power supply are pattern current which of flat top is 10 ms width, the new one is short pulse which of one is 10 us. The short pulse consists of 1st and 3rd higher harmonic. We can expect that the flatness and reproducibility of flat top current can be improved. The calorific power can be also reduced. This paper will report the performance of the power supply and its magnetic field with the eddy septum magnet systems.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK010  
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TUPAK013 Geant4 Simulation of Radiation Effect on the Deflector of Extraction System in HUST SCC250 990
  • S. Hu, K. Fan, L.X.F. Li, Z.Y. Mei, Z.J. Zeng, L.G. Zhang
    HUST, Wuhan, People's Republic of China
  China has payed extensive attention to the development of proton therapy in recent years. When design a compact, high energy superconducting cyclotron for proton therapy, radiation effect induced by beam losses is a crucial consideration. Since the proton beam is extracted out of HUST SCC250 by electrostatic deflectors, the fierce interaction between proton beam and the deflector septum is the main cause of beam losses, which will bring about radiation effect leading to activation and coil quench. This paper presents simulation results of radiation effect by utilizing Geant4 Monte Carlo code. The energy depositions of proton beam in various septum materials are compared. Meanwhile, the yields, the ener-gy and angular distributions of secondary particles are investigated. Those simulation results based on radiation effect will provide us with valuable implications for the design of this superconducting cyclotron.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK013  
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TUPAL003 Measurement of the Injection Beam Parameters by the Multi-Wire Scanner for CSNS 1014
  • M.Y. Huang, H.C. Liu, S. Wang, Zh.H. Xu, P. Zhu
    IHEP, Beijing, People's Republic of China
  • X.H. Lu
    CSNS, Guangdong Province, People's Republic of China
  In order to inject the H beam to the Rapid Cycling Synchrotron (RCS) with high precision and high transport efficiency, the injection beam parameters need to be measured and then corrected while its eccentric position or direction angle is too large. In this paper, firstly, a method to measure the injection beam parameters by using two of the four multi-wire scanners (MWSs) is presented. The injection commissioning results confirmed that this method works well. Secondly, a method to measure the signals of injection beam and circular beam by the INMWS02 is presented and the method work well during the beam commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL003  
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TUPAL005 Study on the Fixed Point Injection during the Beam Commissioning for CSNS 1017
  • M.Y. Huang, H.C. Liu, S. Wang, S.Y. Xu
    IHEP, Beijing, People's Republic of China
  In order to inject the H beam into the Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) accurately, different injection methods were used in different periods of beam commissioning for CSNS. In the early stage of beam commissioning, since the precise relative position of the injection beam and circular beam was unknown and the injection beam power was relatively small, the fixed point injection method was used. In this paper, the fixed point injection method is studied in detail and the beam commissioning results are given and discussed. In addition, a method to adjust the timing of the injection pulse power is presented and confirmed by the beam commissioning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL005  
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TUPAL035 3D Beam Dynamics Modeling of MEBT for the New LANSCE RFQ Injector 1081
  • S.S. Kurennoy
    LANL, Los Alamos, New Mexico, USA
  The new RFQ-based proton injector at LANSCE requires a specialized medium-energy beam transfer (MEBT) after the RFQ at 750 keV due to a following long (~3 m) existing common transfer line that also serves for transporting negative-ion beams to the DTL entrance. The horizontal space for MEBT elements is limited because two beam lines merge at 18-degree angle. The MEBT design developed with envelope codes includes two compact quarter-wave RF bunchers and four short quadrupoles with steerers, all within the length of about 1 m. The beam size in the MEBT is large, comparable to the beam-pipe aperture, hence non-linear 3D field effects at large radii become important. Using CST Studio codes, we calculate buncher RF fields and quadrupole magnetic fields and use them to perform particle-in-cell beam dynamics modeling of MEBT with realistic beam distributions from the RFQ. Our results indicate a significant emittance growth not predicted by standard beam dynamics codes. Its origin was traced mainly to the quadrupole edge fields. Quadrupole design modifications are proposed to improve the MEBT performance.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL035  
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TUPAL036 Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre 1084
  • C. Krantz, T. Fischer, Th. Haberer, B. Kroeck, U. Scheeler, A. Weber, M. Witt
    MIT, Marburg, Germany
  • R. Cee, F. Faber, E. Feldmeier, M. Galonska, Th. Haberer, A. Peters, S. Scheloske, C. Schömers
    HIT, Heidelberg, Germany
  • F. Faber
    Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
  The Marburg Ion-Beam Therapy Centre offers hadron therapy using proton and carbon beams. The accelerator is based on a 65-m ion synchrotron by Danfysik/Siemens Healthcare. Beam extraction from the synchrotron is driven by a transverse RF knock-out (KO) system featuring Dynamic Intensity Control (DIC) of the spill. DIC allows modulation of the extraction rate by factors up to 30 on millisecond time scales. A fast response of the system to the variable intensity set-point can be obtained by careful adjustment of the RF-KO spectrum relative to the machine tune. Tracking simulations of the extraction phase have been conducted to refine that behaviour. Presently, we investigate how fast machine tune shifts, induced by an air-core quadrupole lens, can be used as a way to further improve the spill quality.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL036  
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TUPAL045 Towards Operational Scalability for H Laser Assisted Charge Exchange 1110
  • S.M. Cousineau, A.V. Aleksandrov, T.V. Gorlov, Y. Liu, M.A. Plum, A. Rakhman, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  • D.E. Johnson, S. Nagaitsev
    Fermilab, Batavia, Illinois, USA
  • M.J. Kay
    UTK, Knoxville, Tennessee, USA
  The experimental development of H laser assisted charge exchange, a.k.a. laser stripping, has been ongoing at the SNS accelerator since 2006 in a three-phase approach. The first two phases associated with proof-of-principle and proof-of-practicality experiments have been successfully completed and demonstrated >95% H stripping efficiency for up to 10 us. The final phase is a proof-of-scalability stage to demonstrate that the method can be deployed for realistic beam duty factors. The experimental component of this effort is centered on achieving high efficiency stripping through the use of a laser power amplification scheme to recycle the macropulse laser light at the interaction point of the H stripping. Such a recycling cavity will be necessary for any future operational laser stripping system with at least millisecond duration H pulses. A second component of the proof-of-scalability phase is to develop a conceptual design for a realistic laser stripping scheme. The status of these efforts and challenges associated with deploying the recycling cavity into the laser stripping experiment will be described in this talk.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL045  
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TUPAL055 Progress with Carbon Stripping Foils at ISIS 1136
  • B. Jones, H.V. Cavanagh
    STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
  The ISIS Facility at the Rutherford Appleton Laboratory produces intense neutron and muon beams for condensed matter research. The facility's 50Hz rapid cycling synchrotron accelerates protons from 70 to 800MeV to deliver a mean beam power of 0.2MW to two target stations. Since 2016, ISIS has routinely used commercially produced carbon based foils for beam stripping during charge-exchange injection. Recent experience and developments to increase useful foil lifetime are presented including in-house high temperature annealing of foils prior to use. The installation and performance of a new foil imaging system are described and, finally, the procedure to change the stripping foil is described. Issues with the current arrangements and options for redesign are discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL055  
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