Paper  Title  Other Keywords  Page 

TUPAF055  Progress Toward a Dynamic Extraction Bump for Slow Extraction in the CERN SPS  extraction, simulation, alignment, septum  838 


The possibility of reducing the angular spread of slow extracted particles with a timedependent extraction bump at the CERN Super Proton Synchrotron (SPS) is under investigation. In order to create this socalled 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 beambased 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/JACoWIPAC2018TUPAF055  
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TUPAL028  New Feature of the Oscillating Synchrotron Motion Derived from the Hamiltonian Composed of Three Motions  synchrotron, betatron, experiment, storagering  1060 


The equation for the synchrotron motion was derived from the Hamiltonian, which was composed of coasting, betatron and synchrotron motions*. The betatron oscillation is the horizontal oscillation. The synchrotron oscillation is not only an oscillation of the revolution frequency but also an oscillation of the average radius. The synchrotron oscillation is both longitudinal and horizontal oscillations and it is possible to exchange energy with the betatron oscillation. The synchrotron oscillation occurs under a constant particle velocity and the Hamiltonian is conserved.
*K.Jimbo, Physical Review Special Topics  Accelerator and Beams 19, 010102 (2016). 

DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWIPAC2018TUPAL028  
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TUPAL030  Improvement of RF Capture with MultiTurn H^{−} Injection in KURRI FFAG Synchrotron  injection, acceleration, proton, scattering  1066 


In the KURRI FFAG synchrotron, chargeexchanging multiturn injection is adopted with a stripping foil located on the closed orbit of injection energy. No injection bump orbit system is used and the beam escapes from the foil according to the closedorbit shift by acceleration. The particles hit the foil many times and the emittance grows up during the injection. In this paper, the capture efficiencies are studied with different rf process, including adiabatic capture.  
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TUPAL056  High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron  simulation, resonance, spacecharge, vacuum  1140 


ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory.  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWIPAC2018TUPAL056  
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TUPMF014  Synchrotron Accumulation on OffEnergy ClosedOrbit with AntiSeptum or Nonlinear Kicker  kicker, injection, septum, accumulation  1280 


Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DEAC0206CH11357. Offaxis accumulation on offenergy closedorbit (socalled synchrotron injection/accumulation) was studied and implemented in the 1990s for LEP at CERN. The idea of using pulsed multipole injection on offenergy closedorbit was first proposed in 2014 and then developed for Swiss Light Source (SLS) upgrade in 2015. In 2017, the antiseptum was proposed for SLS upgrade injection. In this paper, two similar injection schemes are proposed which combine offaxis accumulation on offenergy closedorbit (no betatron oscillations), with the antiseptum or pulsed nonlinear kicker schemes. Preliminary lattice solutions are developed for Advanced Photon Source upgrade (APSU) where a special injection straight (with length of 5.8 m) is designed with horizontal dispersion of 0.15m. The impact on the ring emittance is relatively small. The injection elements are all placed in this injection straight, including 1 thin septum and 3 slow kickers (or 1 pulsed nonlinear kicker). No fast kickers are needed. 

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TUPMF040  Alignment of Current Strips at the Canadian Light Source  alignment, undulator, electron, vacuum  1342 


The Quantum Materials Spectroscopy Centre beamline at the Canadian Light Source will employ a 180 mm period elliptically polarizing undulator (EPU180), which will have significant impacts on beam dynamics with large tune shifts and reductions in dynamic aperture. Current strips mounted to the vacuum chamber are intended to mitigate the effects of EPU180 with each strip powered by an independent power supply. It is important to accurately model the current strips in order to calculate the required compensation. We model the current strips as straight wires, parallel to the electron beam, with small horizontal and vertical displacements from their nominal positions. As the real current strips are not completely straight, this is an effective model, but justified as we are mostly interested in the magnetic field integrated along the strips. By activating two strips and measuring the ratio of the two currents needed to minimize closed orbit distortion in the horizontal and vertical planes, we can find the effective horizontal and vertical displacements of the straight wires in the model. Our goal is to create an effective model of the strips from beambased measurements.  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWIPAC2018TUPMF040  
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TUPMF059  Error Study of HEPS Booster  booster, multipole, simulation, lattice  1398 


The High Energy Photon Source (HEPS) is a 6GeV, ultralowemittance light source to be built in China. The injector is composed of a 500MeV linac and a full energy booster with 1 Hz repetition frequency. The detailed error study of the booster will be presented, including misalignment errors and closed orbit correction, magnetic field errors and power supply errors. The effect of errors on closed orbit, tune, chromaticity and dynamic aperture will be discussed. The dynamic aperture with multipole errors will be presented also.  
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TUPML078  Fast Quadrupole Beam Based Alignment Using AC Corrector Excitations  quadrupole, alignment, optics, synchrotron  1727 


A novel method to perform Beam Based Alignment has been tested at ALBA using the 10kHz fast acquisition BPMs together with an AC excitation of the corrector magnets allowing to speed up the beam based alignment process. The former approach relies on software synchronization and tango device servers to execute a series of DC corrector magnets and quadrupoles settings designed to avoid the quadrupole hysteresis effects. The approach that we present here is simpler, gives the same level of accuracy and precision and speeds up the measurement by a factor 10. The total measurement time has changed from 5 hours to 10 minutes.  
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WEPAF032  An Alternative Fast Orbit Feedback Design of HEPS  feedback, lattice, emittance, controls  1888 


The High Energy Photon Source (HEPS) is a fourth generation light source in China and will be built in this year. The emittance of HEPS storage ring is approaching diffraction limit and the circumstance of the ring is about 1.3 kilometres. To stabilize the electron beam, fast orbit feedback (FOFB) system is prerequisite. In this paper, the requirements on the HEPS beam stability are discussed and an alternative FOFB design based on DBPM are introduced with algorithm and architecture.  
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WEPAK003  Effect of Model Errors on the Closed Orbit Correction at the SIS18 Synchrotron of GSI  quadrupole, synchrotron, controls, focusing  2080 


Funding: Deutscher Akademischer Austauschdienst under contract No. 91605207 A fast closed orbit feedback system (bandwidth in the order of 1 kHz) is under development at the GSI SIS18 synchrotron for the orbit correction from injection to extraction including the acceleration ramp. The static process model, represented as the orbit response matrix (ORM), is subjected to the systematic optics changes during ramp e.g. beta function and phase advance variations at the locations of BPMs and steerers. In addition to these systematic variations, model mismatches may arise from dipole and quadrupole magnet errors, space charge dependent tune shift as well as BPM and steerer calibration errors. In this contribution, the effects of these model errors on the closed orbit correction are investigated which is necessary for the robust stability analysis of the feedback controller. For the robustness tests, the traditional SVDbased matrix pseudoinversion is compared to a Fourierbased analysis. The results are achieved by detailed simulations in MADX. 

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THYGBD3  Beambeam Studies for Super ProtonProton Collider  luminosity, resonance, collider, proton  2918 


In China, a twostage circular collider project, CEPCSPPC has been proposed. The first stage, CEPC (Circular Electron Positron Collier, a socalled Higgs factory) is focused on the Higgs physics, and the second stage, SPPC (Super ProtonProton Collider) will be an energy frontier collider and a discovery machine. Luminosity is a key factor for any particlephysics colliders. With the increasing bunch population, beambeam interaction is increasingly become the limit factor of luminosity improvement. The finite crossing angle scheme is considered firstly. Meanwhile, longrange interaction is another significant source of luminosity degrade. In this report, firstly, we don't consider longrange interactions and study luminosity degrade with crossing angle and without crossing angle for horizontal crossing and horizontalvertical crossing. Secondly we discuss luminosity decay with longrange interactions for horizontal crossing and horizontalvertical crossing. Thirdly, we talk about emittance growth and luminosity degradation using resonance analysis for different scenarios. Finally the resulting beambeam limit will be concluded for SPPC.  
Slides THYGBD3 [1.379 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWIPAC2018THYGBD3  
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THPAF040  Estimated Impact of Ground Motion on HLLHC Beam Orbit  groundmotion, quadrupole, luminosity, emittance  3052 


Funding: Research supported by the HLLHC project. The High Luminosity LHC (HLLHC) will require unprecedented orbit stability at the low beta collision points (IP1 and IP5), and the effect of seismic noise might become a relevant source of luminosity loss. Many studies have been conducted in the past to characterise the actual ground motion in the LHC tunnel, and recently a few geophones have been installed to permanently monitor the ground stability at IP1 and IP5. An estimate of the impact of the main machine element vibration on orbit at the IPs and collimators is presented, together with a first look at the data collected by the installed geophones. 

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THPAF077  Ionoptical Measurements at CRYRING@ESR during Commissioning  MMI, acceleration, injection, simulation  3161 


CRYRING@ESR is a heavy ion storage ring, which can cool and decelerate highly charged ions down to a few 100 keV/u. It has been relocated from Sweden to GSI, downstream of the experimental storage ring (ESR), within the FAIR project. The ring will be used as a test facility for FAIR technologies as well as for physics experiments with slow exotic ion beams for several FAIR collaborations: SPARC, BioMat, FLAIR and NUSTAR. CRYRING@ESR is in its commissioning phase since summer 2016. Several ionoptical measurements such as tunes, tune diagram, dispersion, chromaticity and orbit response matrix were performed at the ring. The measurements will be used for several purposes such as improvement of the theoretical model, closed orbit control and correction of unacceptable misalignments, calibration coefficients and field errors.  
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THPAK007  Beam Extraction from TR24 Cyclotron at IPHC  extraction, cyclotron, betatron, emittance  3218 


The CYRCé cyclotron is used at IPHC (Institut Pluridisciplinaire Hubert Curien) for the production of radioisotopes for diagnostics, medical treatments and fundamental research in radiobiology. The TR24 cyclotron manufactured and commercialized by ACSI delivers a 1625 MeV proton beam with intensity from few nA up to 500 microA. The TR24 is a separatedsector isochronous cyclotron with normalconducting magnet and stripper foil. It is a challenge to fit the high intensity proton beam used for target irradiation to radiobiology and analytical applications due to requirements on beam quality and energy resolution. Field distribution in the region of the extraction performed with OPERA 3D as well as beam dynamics related with stripping are analysed. 3D calculation model and hypothesis about geometry and beam are described. Our goal is to evaluate the extraction efficiency and the beam characteristics in the focusing plane outside the cyclotron which will serve as inputs for the design of future beam lines and enable beam matching conditions. Therefore, different issues are discussed: energy dispersion, transverse dynamics and orbit separation.  
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THPAK114  Evaluation of an Interior Point Method Specialized in Solving Constrained Convex Optimization Problems for Orbit Correction at the Electron Storage Ring at DELTA  software, feedback, storagering, electron  3507 


The slow orbit feedback at the electron storage ring at DELTA will be upgraded with new software. Finding a set of dipolefieldstrength variations which minimize the deviation of the orbit from a reference orbit requires solving a convex optimization problem subject to inequality constraints. This work focuses on exploiting properties of a special type of interior point methods, which can solve this problem, for orbit correction at DELTA. After comparing runtimes of an interior point method to a Newtonlike optimization algorithm, the performance of the new sloworbitfeedback software is assessed based on measurement results.  
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THPMF053  Study of the Dynamic Aperture Reduction Due to Error Effects for the High Energy Photon Source  sextupole, lattice, quadrupole, optics  4182 


Funding: Work supported by Natural Science Foundation of China(No.11605212). The 6 GeV High Energy Photon Source (HEPS) employs a lattice of 48 hybrid 7BA cells, aims to achieve a natural emittance between 30 to 60 pm, within a circumference of about 1.3 km. In the performance evaluation of optimized lattices, we found that the dynamic aperture of the bare lat tice were su cient for onaxis swapout injection, but a large reduction in the dynamic aperture was observed in the simu lation when including lattice imperfections and even after dedicated lattice corrections. In this paper, we identi ed the feeddown e ects of sextupoles as the major source of DA reduction, and proposed to use dedicated sextupole movers to e ciently reduce the orbit o sets in sextupoles, to par tially recover the dynamic aperture, sextupole moverbased optics correction schemes were also discussed. 

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THPMF078  Simulation of Trajectory Correction in Early Commissioning of the Advanced Light Source Upgrade  MMI, simulation, lattice, sextupole  4256 


Funding: *Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC0205CH11231. The ALS upgrade into a diffractionlimited soft xrays light source requires a small emittance, which is achieved by much stronger focusing than in the present ALS. Very strong focusing elements and a relatively small vacuum chamber make the required rapid commissioning a significant challenge. This paper will describe the progress towards a starttoend simulation of the machine commissioning and present first simulation results. 

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THPMK135  Corrector Layout Optimization Using NSGAII for HALS  dipole, storagering, lattice, sextupole  4629 


In this paper, we present a method to find the global optimum correctors layout based NSGAII algorithm when the number of correctors is limited to be equal to the number of BPMs. We prove that this method works well with HALS.  
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THPML084  Validating the COBEA Algorithm at the DELTA Storage Ring  storagering, optics, betatron, lattice  4851 


ClosedOrbit BilinearExponential Analysis (COBEA) is an algorithm to decompose monitorcorrector response matrices into (scaled) beta optics values, phase advances, scaled dispersion and betatron tunes. No explicit magnetic lattice model is required for COBEA  only the sequence of monitors and correctors along the beam path (no lengths, no strengths approach). To obtain absolute beta values, the length of one drift space can be provided as optional input. In this work, the application of COBEA to the DELTA storage ring, operated by TU Dortmund University, is discussed, and its results for betatron tunes and scaled dispersion are compared with those of conventional, direct measurement methods. COBEA is also put in a historical perspective to other diagnostic algorithms. Improvements in the Python implementation of COBEA, which is available as free software, are presented. Due to COBEA being relatively modest regarding its requirements on input data respectively hardware, it should be applicable to the majority of existing storage rings.  
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THPML107  Steering Optimizations for the University of Maryland Electron Ring  dipole, lattice, injection, experiment  4913 


Funding: This work is supported by the US Dept. of Energy, Office of High Energy Physics award # DESC0010301 The University of Maryland Electron Ring (UMER) has the flexibility to set up alternative lattices for different research experiments, including nonlinear optics studies using octupoles. Each alternative lattice requires an acceptable steering solution for use in experiments. Existing beambased alignment tools can take a significant amount of time to run and become difficult to process with a low number of BPMs. The Robust Conjugate Directional Search (RCDS) optimizer* is used to quickly obtain steering solutions for different lattice configurations and has been adopted for beam steering at UMER. Steering magnets are optimized online to reduce scraping, correct equilibrium orbits, and increase beam lifetimes. This study presents the application of the optimizer at UMER. * X. Huang, J. Corbett, J. Safranek, J. Wu, Nucl. Instr. Meth. A vol. 726, pp. 7783, 2013. 

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