Keyword: coupling
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MOOCB03 A Novel Method for Quasi-non-interceptive Beam Profile Measurement in a Linac linac, diagnostics, emittance, beam-transport 50
 
  • A.V. Aleksandrov
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
Beam profile diagnostics is an important tool for understanding beam dynamics in accelerators. Non-interceptive diagnostics have many great advantages but often are difficult in implementation. We suggest a method of measuring beam profiles that is not truly non-interceptive, because beam has to be intercepted at some point, preferably in the beginning of the linac. But significant difference from a conventional interceptive measurement is that beam is not intercepted at any of the points of measurement along the linac. One important application is measuring beam profiles within cryostats of a super-conducting linac. The equipment required for implementing this diagnostic is simple: a set of slits in the beginning of the accelerator, and a Beam Position Monitor (BPM) in the point of measurement. Beam profiles can be measured simultaneously at every BPM along the linac. In this paper we will discuss details of the method, its limitations, and effect of non-linearity, coupling and space charge. Results of a demonstration experiment at SNS will be presented and discussed.
 
slides icon Slides MOOCB03 [3.365 MB]  
 
MOPC004 352.2 MHz HOM Damped Normal Conducting ESRF Cavity: Design and Fabrication cavity, HOM, vacuum, storage-ring 68
 
  • V. Serrière, A.K. Bandyopadhyay, D. Boilot, L. Goirand, J. Jacob, B. Ogier, A. Triantafyllou
    ESRF, Grenoble, France
 
  Funding: This work, carried out within the framework of the ESRFUP project, has received research funding from the EU Seventh Framework Programme, FP7.
The ongoing ESRF upgrade included an option for an increase of the storage ring current from 200 to 300 mA, which has been tested successfully with the existing RF system. At this current level the HOM tuning of the existing five-cell copper cavities becomes extremely delicate and in view of a future reliable operation in user mode, new HOM free normal conducting cavities were developed at the ESRF. The design is based on the existing BESSY/ALBA cavity. However, several substantial modifications have been implemented and different fabrication processes elaborated to improve the design. Three operational prototypes will be delivered by three manufacturers in the coming months and will be fully tested on the ring. Although the 300 mA option has finally not been retained for the first phase of the ESRF upgrade, the aim is now to validate the new cavity design for a possible later increase in current.
 
 
MOPC006 A Coupled RFQ-IH Combination for the Neutron Source FRANZ rfq, DTL, cavity, proton 74
 
  • M. Heilmann, O. Meusel, D. Mäder, U. Ratzinger, A. Schempp
    IAP, Frankfurt am Main, Germany
 
  Funding: HIC for FAIR
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum is driven by a 2 MeV proton linac consisting of a 4-rod-radio-frequency-quadrupol (RFQ) and an 8 gap IH-DTL structure. RFQ and IH cavity will be powered by only one radio frequency (RF) amplifier to reduce costs. The RF-amplifier of the RFQ-IH combination is coupled into the RFQ. Internal inductive coupling along the axis connects the RFQ with the IH cavity ensuring the required power transition as well as a fixed phase relation between the two structures. The main acceleration of 120 keV up to 2.03 MeV will be reached by the RFQ-IH combination with 175 MHz and at a total length of 2.3 m. The losses in the RFQ-IH combination are about 200 kW.
 
 
MOPC009 Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator electron, acceleration, linac, simulation 80
 
  • H. Shaker
    IPM, Tehran, Iran
  • F. Ghasemi
    sbu, Tehran, Iran
  • H. Shaker
    CERN, Geneva, Switzerland
 
  This design is related to a Pi/2 mode S-Band low energy TW electron linear accelerator which is in the construction stage. This project is supported by the school of particles and accelerators, institute for research in fundamental sciences (IPM), Tehran, Iran. This design consists of a buncher and an accelerating structure that are joined and two couplers for the input/output feedings. At each design stage, different methods (analytical or numerical) are used to confirm the results and also to have a better understanding.  
 
MOPC012 Fabrication of the CERN/PSI/ST X-band Accelerating Structures wakefield, alignment, vacuum, FEL 86
 
  • M.M. Dehler, A. Citterio, R. Zennaro
    PSI, Villigen, Switzerland
  • S. Atieh, D. Gudkov, S. Lebet, G. Riddone, J. Shi
    CERN, Geneva, Switzerland
  • G. D'Auria, C. Serpico
    ELETTRA, Basovizza, Italy
 
  Within a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a multi- purpose X-band accelerating structure has been designed and fabricated, used for high gradients tests in the CLIC structure testing program and in the FEL projects of PSI and ST. The structure has 72 cells with a phase advance of 5 pi/6 and includes upstream and downstream wakefield monitors to measure the beam alignment. The SLAC mode launcher design is used to feed it with RF power. Following the CERN fabrication procedures for high-gradient structure, diffusion bonding and brazing in hydrogen atmosphere is used to assemble the cells. After tuning, a vacuum bakeout is required before the feedthroughs for the wake field monitors are welded in as a last step. We describe the experiences gained in finishing the first two structures out of a series of four and present the results from the RF tuning and low level RF tests.  
 
MOPC017 Thermal Analyses of an RF Input Coupler for the IFMIF/EVEDA RFQ Linac rfq, cavity, linac, beam-transport 101
 
  • S. Maebara
    JAEA, Ibaraki-ken, Japan
 
  In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a coupled cavity type of RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in CW mode. The driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As the RF input coupler design, RF losses including a loop antenna and an RF vacuum window, based on a 6 1/8 inch co-axial waveguide were calculated. In this conference, these results and thermal analysis results in CW operation mode will be presented in details.  
 
MOPC023 Design of a C-band 6 MeV Standing-wave Linear Accelerating Structure electron, bunching, impedance, simulation 119
 
  • J.H. Shao, H. Chen, Q.Z. Xing
    TUB, Beijing, People's Republic of China
 
  We design a C-band standing-wave biperiodic on-axis coupled linear accelerating structure for industrial and medical applications. It’s less than 300mm long; consists of 3 bunching cells and 9 normal cells. It can accelerate electrons to 6MeV and the pulsed beam current is 100mA. The RF power source is a 2.5MW magnetron. We implement 2D cells geometry optimization by SUPERFISH, beam dynamics study by PARMELA and full scale 3D calculations by MAFIA codes.  
 
MOPC031 Performance of a 13 MHz Cavity for an RF Implanter at PEFP* cavity, ion, ion-source, simulation 136
 
  • T.A. Trinh
    UST, Daejeon, Republic of Korea
  • Y.-S. Cho, J.-H. Jang, D.I. Kim, H.S. Kim, H.-J. Kwon, B.-S. Park, K.T. Seol
    KAERI, Daejon, Republic of Korea
 
  Funding: This work is supported by the Ministry of Education, Science and Technology of the Korean Government
A 13 MHz - normal conducting cavity for an rf implanter has been successfully developed at PEFP (Proton Engineering Frontier Project). It consists of an inductive coil, accelerating electrodes and a ground electrode for the inductor. Quality factor of 2074 and critical coupling were achieved at resonant frequency of 12.658 MHz. Rf power of 1 kW was forwarded to the cavity without any spark in the cavity. Beam test was then carried out with a 27 keV helium beam generated from a Duoplasmatron ion source. The results showed that the helium beam was accelerated to final energy of 120 keV with energy spread of 1%. Detail experiments and results are addressed in this presentation.
 
 
MOPC042 RF and Accelerating Structure of 12 MeV UPC Race-track Microtron linac, vacuum, microtron, controls 169
 
  • Yu.A. Kubyshin, X. Gonzalez Arriola
    UPC, Barcelona, Spain
  • D. Carrillo, L. García-Tabarés, F. Toral
    CIEMAT, Madrid, Spain
  • S.J. Mathot
    CERN, Geneva, Switzerland
  • G. Montoro
    EPSC, Castelldefels, Spain
  • V.I. Shvedunov
    MSU, Moscow, Russia
 
  We describe the design and technical characteristics of a C-band SW accelerating structure of a 12 MeV race-track microtron, which is under construction at the Technical University of Catalonia, and its RF system with a 5712 MHz magnetron as a source. Results of cold tests of the accelerating structure, before and after the brazing, and of high-power tests of the RF system at a special stand are reported. The main features of the magnetron frequency stabilization subsystem are also outlined.  
 
MOPC052 Engineering Design and Fabrication of X-band RF Components vacuum, klystron, pick-up, diagnostics 196
 
  • M. Filippova, A. Olyunin, V. Soldatov, A. Solodko
    JINR, Dubna, Moscow Region, Russia
  • S. Atieh, G. Riddone, I. Syratchev
    CERN, Geneva, Switzerland
 
  The CLIC RF frequency has been changed in 2008 from the initial 30 GHz to the European X-band 11.9942 GHz permitting beam independent power production using klystrons for accelerating structure testing. X-band klystron test facilities at 11.424 GHz are operated at SLAC and at KEK, and these facilities are used by CLIC study in the frame of the X-band structure collaboration for testing accelerating structures scaled to that frequency*. Generally RF components are used in the transmission and the transformation of radio frequency signals generated by the power supply. The operating range of the devices accommodates the frequencies from 11.424 to 11.9942 GHz. RF components are needed for the Klystron test stand at CERN, and also for the X-FEL projects at PSI and Sincrotrone Trieste. Currently CERN is ordering tens of these companies to industry. The engineering design of the RF components (high power and compact loads, bi-directional couplers, X-band splitters, hybrids, phase shifters, variable power attenuators) and the main fabrication processes are presented here.
* K.M. Schirm et al., “A 12 GHZ RV Power source for the CLIC study”, Proc. of IPAC’10, THPEB053, p. 3990 (2010).
 
 
MOPC056 The Linac4 Power Coupler cavity, linac, vacuum, simulation 208
 
  • F. Gerigk, J.-M. Giguet, E. Montesinos, B. Riffaud, P. Ugena Tirado, R. Wegner
    CERN, Geneva, Switzerland
 
  Linac4 employs 3 types of accelerating structures after the RFQ: a Drift Tube Linac (DTL), a Cell-Coupled DTL (CCDTL), and a Pi-Mode Structure (PIMS) to accelerate the beam to 160 MeV. The structures are designed for a peak power of 1 MW per coupler, which consists of two parts: a ceramic window, which separates the cavity vacuum from the air in the wave-guides, and a so-called "coupling T", which couples the RF power through an iris to the cavity. In the frame of the Linac4 R&D both devices have been significantly improved with respect to their commonly used design. On the coupler side, the wave-guide short circuit with its matched length has been replaced by a fixed length λ/4 short circuit. The RF matching is done by a simple piston tuner, which allows a quick matching to different cavity quality factors. In the window part, which usually consists of a ceramic disc and 2 pieces of wave-guides with matching elements, the wave-guide sections could be completely suppressed, so that the window became very compact, lightweight, and much simpler to manufacture. In this paper we present electromagnetic simulations, and tests on first prototypes, which were constructed at CERN.  
 
MOPC071 Status of High Power Tests of Normal Conducting Short Standing Wave Structures* klystron, electron, status, beam-loading 241
 
  • V.A. Dolgashev, Z. Li, S.G. Tantawi, A.D. Yeremian
    SLAC, Menlo Park, California, USA
  • Y. Higashi
    KEK, Ibaraki, Japan
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
 
  Funding: Work Supported by Doe Contract No. DE-AC02-76SF00515
We report results of continuing high power tests of short standing wave structures. These tests are part of an experimental and theoretical study of basic physics of rf breakdown in 11.4 GHz, normal conducting structures. The goal of this study is to determine the accelerating gradient capability of normal conducting rf powered particle accelerators. We have tested structures of different geometries, cell joining techniques, and materials. We found that the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for cylindrically symmetric structures powered via a TM01 mode launcher. We report test results for structures powered by side-coupled rectangular waveguides. We found that increased rf magnetic field due to the side-coupling increases the breakdown rate as compared to the same accelerating gradient in cylindrically symmetric structures.
 
 
MOPC072 Design of an RF Feed System for Standing-wave Accelerator Structures cavity, wakefield, damping, linac 244
 
  • J. Neilson, V.A. Dolgashev, S.G. Tantawi
    SLAC, Menlo Park, California, USA
 
  Travelling wave (TW) accelerator structures are known to suffer from several deficiencies. A breakdown in one of the cells propagates towards the source. This results in damage to upstream cells in addition to the cell where the breakdown was initiated. The deficiencies of TW accelerator structures can be overcome by using standing wave (SW) cells that are fed in parallel. An RF breakdown is contained to the cell where it originates. This eliminates upstream cell damage and the resulting changes in phase shift between cells. In addition the feed structure can provide a high conductance port for vacuum pumping. We have completed the design of a parallel fed SW structure with a directional coupler for each cell and serpentine waveguide connection between couplers. This design approach improves isolation between the cells resulting in the maximum increase in the operational robustness of the accelerator structure. The design uses four feed arms spaced uniformly around the cell circumference to suppress dipole modes and improve damping of low order wakefields. Construction of a test structure in now underway and is scheduled for testing in October of this year.  
 
MOPC080 First Considerations Concerning an Optimized Cavity Design for the Main Linac of BERLinPro cavity, HOM, linac, impedance 259
 
  • B. Riemann, T. Weis
    DELTA, Dortmund, Germany
  • W. Anders, J. Knobloch, A. Neumann
    HZB, Berlin, Germany
  • H.-W. Glock, C. Potratz, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
  • F. Marhauser
    JLAB, Newport News, Virginia, USA
 
  Funding: work supported by BMBF under contracts 05K10PEA and 05K10HRC
The Berlin Energy Recovery Linac Project (BERLinPro) is designed to develop and demonstrate CW linac technology and expertise required to drive next-generation Energy Recovery Linacs. Strongly HOM-damped multicell 1.3 GHz cavities are required for the main linac. The optimization of the cavities presented here is primarily based on the CEBAF 1.5 GHz 5-cell high-current cavity design, including HOM waveguide couplers. The cavity was scaled to 1.3 GHz and extended to 7 cells. Modifications to the end group design have also been studied. An effort was also made to reduce the ratio Epk/Eacc while still permitting HOMs to propagate.
 
 
MOPC090 Tuner Performance in the S1-global Cryomodule cavity, controls, cryomodule, high-voltage 286
 
  • R. Paparella, A. Bosotti, C. Pagani
    INFN/LASA, Segrate (MI), Italy
  • C. Albrecht, K. Jensch, L. Lilje
    DESY, Hamburg, Germany
  • S. Barbanotti, Y.M. Pischalnikov, W. Schappert
    Fermilab, Batavia, USA
  • H. Hayano, E. Kako, S. Noguchi, N. Ohuchi, Y. Yamamoto
    KEK, Ibaraki, Japan
 
  S1-Global is a collaborative effort of INFN, DESY, FNAL, SLAC and KEK, in the framework of the ILC global collaboration. For this project two cryomodules, 6 meter long and hosting four SC cavities each, were realized and successfully cold tested at KEK-STF. Three different cavity tuning systems, provided with fast tuning capability through piezoelectric actuators (piezo), were installed, and fully characterized in static and dynamic operation: Blade Tuner from INFN/FNAL, Saclay Tuner from DESY, Slide Jack Tuner from KEK. Finally, Lorenz Force Detuning (LFD) active compensation has been successfully achieved during high power cavity tests in pulsed RF regime, where active control of the LFD disturbance up to Hz-level residual detuning has been achieved with each type of tuning system up to the maximum gradient of each cavity. The installation procedures, together with the relevant results and their analyses are summarized in the paper.  
 
MOPC120 Design of Superconducting Parallel-bar Deflecting/Crabbing Cavities cavity, luminosity, SRF, proton 361
 
  • J.R. Delayen, S.U. De Silva
    ODU, Norfolk, Virginia, USA
 
  The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties, compared to other conventional designs, that is being considered for a number of applications. We present an analysis of several designs of parallel-bar cavities and their electromagnetic properties.  
 
MOPC132 Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator* resonance, simulation, plasma, space-charge 388
 
  • X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong
    National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
 
  Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. *gexingjun230230@yahoo.com.cn
The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%.
 
 
MOPC166 Low RF Control Feedback and IQ Vector Modulator Compensation Functions controls, linac, gun, feedback 472
 
  • M.G. Fedurin, R. Malone, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
 
  IQ vector modulator is key element of the gun and linac RF control circuits at Accelerator Test Facility at Brookhaven National Laboratory. IQ modulator calibration procedure was developed to find proper compensation functions in the conversion algorithm to minimize phase-amplitude coupling and setting-reading errors: rms(Aset - Aread )= 0.03dB, rms(Phiset - Phiread) = 0.3 deg. Since stabilization of the RF phase and amplitude is become critical for many experiments the slow feedback was developed and applied as well to significantly compensate drifts in RF system.  
 
MOPO022 Precision Beam Instrumentation and Feedback-Based Beam Control at RHIC feedback, acceleration, controls, resonance 526
 
  • M.G. Minty, W. Fischer, H. Huang, R.L. Hulsart, C. Liu, Y. Luo, G.J. Marr, A. Marusic, K. Mernick, R.J. Michnoff, V. Ptitsyn, G. Robert-Demolaize, T. Roser, V. Schoefer, S. Tepikian, M. Wilinski
    BNL, Upton, Long Island, New York, USA
 
  Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this report we present advances in beam instrumentation required for feedback-based beam control at the Relativistic Heavy Ion Collider (RHIC). Improved resolution has contributed to enabling now routine acceleration with multiple feedback loops. Better measurement and control of the beam’s properties have allowed acceleration at a new working point and have facilitated challenging experimental studies.
 
 
MOPS016 First Observations of Intensity-dependent Effects for Transversally Split Beams resonance, extraction, space-charge, booster 631
 
  • S.S. Gilardoni, M. Giovannozzi
    CERN, Geneva, Switzerland
 
  During the commissioning of the CERN PS Multi-Turn Extraction (MTE) tests with different beam intensities were performed. The beam current before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total intensity was found, which is a first observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in this paper.  
 
MOPS045 Coupling Impedance of Rough Resistive Pipe* impedance, resonance, vacuum, wakefield 700
 
  • M. Ivanyan, V.M. Tsakanov
    CANDLE, Yerevan, Armenia
 
  A new version of modelling of the surface roughness impact by thin dielectric layer in the round resistive beam pipe is suggested. The calculation method of coupled resistive-roughness impedance is developed.  
 
MOPS052 Analytical and Numerical Calculations of Beam Pipe Impedances at Low Frequencies with Application to Thin SIS100 Pipe impedance, synchrotron, shielding, betatron 721
 
  • U. Niedermayer, O. Boine-Frankenheim, L. Hänichen
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  The projected fast ramped synchrotron SIS100 for FAIR uses an elliptical stainless steel beam pipe of 0.3 mm thickness. The lowest coherent betatron sidebands reach down to 100 kHz which demands accurate impedance calculations in the low frequency (LF) regime. For these frequencies, i.e. skin depth greater than wall thickness, structures behind the pipe may contribute to the impedance. Due to the extremely large wake length numerical methods in the time domain are not applicable. The longitudinal and transverse impedance of the thin SIS100 beam pipe including structures behind the pipe are obtained numerically by a method using power loss in the frequency domain. We compare different analytical models for simplified pipe structures to the numerical results. The dc and ultra-relativistic limits are investigated. The interpretation of bench measurements in the LF regime is discussed.  
 
MOPS054 Impedance of the Pulse Power Converter for the SIS100 Bipolar Extraction Kicker System impedance, kicker, simulation, extraction 727
 
  • K. Samuelsson, V. Hinrichsen
    TU Darmstadt, Darmstadt, Germany
  • U. Blell, P.J. Spiller
    GSI, Darmstadt, Germany
 
  SIS100 will be operated with high intensity heavy-ion and proton beams. The reduction of ring impedances is therefore of great importance in order to avoid coherent beam instabilities. The kicker system is one of the main contributors to the overall ring impedance in SIS100. This paper will focus on the contribution of the external network to the kicker impedance. Calculations as well as experimental impedance measurements of the network contribution have already been carried out for the SIS18 and ESR kickers. The SIS100 will be equipped with a bipolar kicker system, which uses a Pulse Forming Network (PFN) as energy storage. For potential detachment purposes an insulation transformer will be installed. Since this setup is new in several ways it is important to know its contribution to the coupling impedance of the kicker system. In this contribution the corresponding numerical calculation is presented.  
 
MOPS059 Transverse Impedance Calculation for Simplified Model of Ferrite Kicker Magnet with Beta < 1 impedance, kicker, extraction, proton 742
 
  • N. Wang, Q. Qin
    IHEP Beijing, Beijing, People's Republic of China
 
  In high intensity rings, kicker magnet is usually considered as a main source to the total impedance. Transverse coupling impedance of a simplified kicker model has been derived analytically in the ultrarelativistic limit. We extend the result to the general case of v < c, and present the analytical formulae of both horizontal and vertical transverse impedances. Numerical results are given for the CSNS extraction kicker magnets.  
 
MOPS073 Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime impedance, kicker, vacuum, neutron 772
 
  • N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini
    CERN, Geneva, Switzerland
  • N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo
    Rome University La Sapienza, Roma, Italy
  • Q. Qin, N. Wang
    IHEP Beijing, Beijing, People's Republic of China
 
  Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.  
 
MOPS075 Simulation of Multibunch Motion with the HEADTAIL Code and Application to the CERN SPS and LHC impedance, wakefield, simulation, synchrotron 778
 
  • N. Mounet
    EPFL, Lausanne, Switzerland
  • N. Mounet, E. Métral, G. Rumolo
    CERN, Geneva, Switzerland
 
  Multibunch instabilities due to beam-coupling impedance can be a critical limitation for synchrotrons operating with many bunches. It is particularly true for the LHC under nominal conditions, where according to theoretical predictions the 2808 bunches rely entirely on the performance of the transverse feedback system to remain stable. To study these instabilities, the HEADTAIL code has been extended to simulate the motion of many bunches under the action of wake fields. All the features already present in the single-bunch version of the code, such as synchrotron motion, chromaticity, amplitude detuning due to octupoles and the ability to load any kind of wake fields through tables, have remained available. This new code has been then parallelized in order to track thousands of bunches in a reasonable amount of time. The code was benchmarked against theory and exhibited a good agreement. We also show results for bunch trains in the LHC and compare them with beam-based measurements.  
 
MOPS079 Simulations of Coaxial Wire Measurements of the Impedance of Asymmetric Structures impedance, simulation, kicker, synchrotron 787
 
  • H.A. Day, R.M. Jones
    UMAN, Manchester, United Kingdom
  • F. Caspers, H.A. Day, E. Métral
    CERN, Geneva, Switzerland
 
  Coaxial wire measurements have provided a simple and effective way to measure the beam coupling impedance of accelerator structures for a number of years. It has been known how to measure the longitudinal and dipolar transverse impedance using one and two wires for some time. Recently the ability to measure the quadrupolar impedance of structures exhibiting top/bottom and left/right symmetry has been demonstrated. A method for measuring the beam coupling impedance of asymmetric structures using displaced single wires and two wire measurements is proposed. Simulations of the measurement system are presented with further work proposed.  
 
MOPS080 Comparison of the Current LHC Collimators and the SLAC Phase 2 Collimator Impedances impedance, simulation, cavity, collimation 790
 
  • H.A. Day, R.M. Jones
    UMAN, Manchester, United Kingdom
  • F. Caspers, H.A. Day, E. Métral, B. Salvant
    CERN, Geneva, Switzerland
 
  One of the key sources of transverse impedance in the LHC has been the secondary graphite collimators that sit close to the beam at all energies. This limits the stable bunch intensity due to transverse coupled-bunch instabilities and transverse mode coupling instability. To counteract this, new secondary collimators have been proposed for the phase II upgrade of the LHC collimation system. A number of designs based on different jaw materials and mechanical designs have been proposed. A comparison of the beam coupling impedance of these different designs derived from simulations are presented, with reference to the existing phase I secondary collimator design.  
 
MOPS089 Identification of Bunch Dynamics in the Presence of E-cloud and TMCI for the CERN SPS Ring simulation, controls, feedback, kicker 811
 
  • O. Turgut, J.D. Fox, C.H. Rivetta, S. Uemura
    SLAC, Menlo Park, California, USA
  • W. Höfle
    CERN, Geneva, Switzerland
 
  Funding: Work is supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
Measurements and multi-particle simulation codes (i.e. HEAD-TAIL, WARP, CMAD) indicate that bunched particle beams show unstable motions induced by electron-clouds and strong head-tail interactions. The bunch dynamics exhibits highly non-linear, complex and unstable behavior under certain operating conditions. Feedback control systems have been proposed to mitigate these instabilities in the CERN SPS ring. The design of feedback systems requires the knowledge of a reduced dynamic model of the bunch. It allows to include and quantify the effect of noise and signal perturbations, as well as system robustness to parameter variation. Identification techniques are used to estimate those models based on bunch motion measurements. In this work we present reduced mathematical models representing the transverse bunch dynamics and identification techniques to extract the model parameters based on measurements. These techniques are validated using time domain simulations of the bunch motion conducted using multi-particle simulation codes. For that, different sections of the bunch are driven by random signals, and the vertical motion of those areas is used to estimate the reduced model.
 
 
TUODA01 Vertical Emittance Reduction and Preservation at the ESRF Electron Storage Ring emittance, quadrupole, feedback, storage-ring 928
 
  • A. Franchi, J. Chavanne, F. Ewald, L. Farvacque, T.P. Perron, K.B. Scheidt
    ESRF, Grenoble, France
 
  In 2010 a campaign for the reduction and preservation of low vertical emittance at the ESRF electron storage ring was undertaken: values between 20 and 30 pm have been dramatically reduced to 3.5-4.5 pm, even during beam delivery. This improvement is the result of an increased measurement precision provided by the recently upgraded beam position monitoring system, a new correction algorithm, a larger number of correctors and two independent schemes for the automatic compensation of coupling induced by a few insertion devices whenever their gaps are moved by users during beam delivery. This paper summarizes the campaign's milestones and the results updated to the first half of 2011.  
slides icon Slides TUODA01 [5.297 MB]  
 
TUYB02 The Challenges of Ultra-low Emittance Damping Rings emittance, damping, electron, quadrupole 956
 
  • D. L. Rubin
    CLASSE, Ithaca, New York, USA
 
  Funding: Work supported by the National Science Foundation and by the US Department of Energy under contract numbers PHY-0734867 and DE-FC02-08ER41538.
In this paper we review the state of the art of the design of damping rings for linear colliders, as supported by the experimental data from ATF and CESR test damping rings. We consider implications of measurements of electron cloud dynamics and mitigation in a radiation dominated ring. The techniques developed for tuning for ultra-low emittance in these rings are summarized. Other dynamics manifested in the ultra-low emittance regime where collective effects are important are discussed.
 
slides icon Slides TUYB02 [7.198 MB]  
 
TUPC007 Kicker and Monitor for CTF3 Phase Feed Forward kicker, impedance, pick-up, collider 1000
 
  • F. Marcellini, D. Alesini, A. Ghigo
    INFN/LNF, Frascati (Roma), Italy
 
  Funding: Work partially supported by the EuCARD research programme, Grant Agreement 227579, within the 'Assessment of Novel Accelerator Concepts'.
In the Compact LInear Collider (CLIC) the synchronization of the Drive Beam and the Main Beam has to be assured in the femtosecond range to avoid luminosity reduction of the collider. The Drive and Main Beams arrival time is measured with longitudinal monitors and the correction is applied changing the path length of one beam respect to the other in a magnetic chicane by means of two transverse fast stripline kicker. The performance of the feed forward system will be tested in the CLIC Test Facility (CTF3) measuring the phase at the linac exit, correcting in the chicane after the combination rings and comparing the longitudinal position change before the power RF production system. The developed phase monitors and kicker magnets for the test in CTF3 are described.
 
 
TUPC026 Status of the Crab Cavity Design for the CLIC cavity, damping, wakefield, dipole 1054
 
  • P.K. Ambattu, G. Burt, A.C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • V.A. Dolgashev
    SLAC, Menlo Park, California, USA
  • A. Grudiev
    CERN, Geneva, Switzerland
  • R.M. Jones
    UMAN, Manchester, United Kingdom
  • P.A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  RF design of a crab cavity (2π/3, 11.9942 GHz) for the Compact Linear Collide (CLIC) is presented. As part of the UK-CLIC collaboration, CERN is building two copper prototypes, designed by Lancaster University / Cockcroft Institute. The first prototype to be made will be a 12 cell undamped cavity and the second will be waveguide damped cavity. The RF test at CERN will help characterisation of the dipole mode with X-band RF pulses of 15 MW peak power and pulse length of ~242 ns. Since the cavity frequency and phase advance per cell are identical to those of the CLIC main linac, the first prototype could exploit CERN’s X-band cavity characterisation facilities. A fully damped cavity will be required for the actual machine in order to meet the luminosity specs. The damped prototype will use an identical coupler type as the undamped one, but the cells will have damping waveguides with / without dielectric material.  
 
TUPC036 S-band ps Pulse Photoinjector for THz Radiation Source electromagnetic-fields, electron, gun, acceleration 1078
 
  • S.M. Polozov, T.V. Bondarenko
    MEPhI, Moscow, Russia
 
  S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results.  
 
TUPC052 Normal Mode BPM Calibration for Ultralow-Emittance Tuning in Lepton Storage Rings emittance, quadrupole, alignment, simulation 1114
 
  • A. Wolski
    The University of Liverpool, Liverpool, United Kingdom
  • D. L. Rubin, D. Sagan, J.P. Shanks
    CLASSE, Ithaca, New York, USA
 
  BPMs capable of high-resolution turn-by-turn measurements offer the possibility of new techniques for tuning for ultra-low beam emittance. In this paper, we describe how signals collected from individual buttons during resonant beam excitation can be used to calibrate BPMs to read the beam position in a normal mode coordinate system. This allows for rapid minimization of the mode II emittance, simply by correcting the mode II dispersion. Simulations indicate that the technique is effective and robust, and has the benefit of being insensitive to BPM gain and alignment errors that can limit the effectiveness of other techniques.  
 
TUPC076 Realization of a High Bandwidth Bunch Arrival-time Monitor with Cone-shaped Pickup Electrodes for FLASH and XFEL pick-up, electron, laser, free-electron-laser 1177
 
  • A. Angelovski, M. Hansli, R. Jakoby, A. Kuhl, A. Penirschke, S. Schnepp
    TU Darmstadt, Darmstadt, Germany
  • M. Bousonville, H. Schlarb
    DESY, Hamburg, Germany
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
 
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA
In the Free Electron Laser in Hamburg (FLASH) an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing*. Future experiments will be conducted using significantly lower bunch charges resulting in a reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth as introduced in **. This paper presents the implementation and measurement results of a high bandwidth cone-shaped pickup capable of operating in the frequency range up to 40 GHz. The slope steepness at the zero crossing is investigated for a simplified equivalent circuit model. RF-measurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance. The measurements are compared to simulation results obtained by CST PARTICLE STUDIO®.
* F. Loehl et al., Proc. of DIPAC2007, WEPB15, p. 262 (2007).
** A. Angelovski et al., "Pickup design for a high resolution Bunch Arrival time Monitor for FLASH and XFEL", DIPAC2011.
 
 
TUPC077 Investigations on High Sensitive Sensor Cavity for Longitudinal and Transversal Schottky for the CR at FAIR cavity, dipole, resonance, simulation 1180
 
  • M. Hansli, A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • W. Ackermann, T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  • P. Hülsmann
    GSI, Darmstadt, Germany
 
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 06DA90351
For the Collector Ring (CR) at the FAIR (Facility for Antiproton and Ion Research) accelerator complex a sensitive Schottky sensor is required. The CR covers different modes of operation, like pre-cooling of antiprotons at 3 GeV, pre-cooling of rare isotope beams at 740 MeV/u and an isochronous mode for mass measurements. For longitudinal Schottky measurements the concept of a resonant cavity had been introduced [Hansli2011]. Due to limited space inside the ring, the integration of transversal Schottky analysis into this cavity is desired. In this paper the demands and required changes to implement also transversal Schottky measurements are discussed. An analysis of the expected signal characteristics featuring equivalent circuit is shown, as well as numerical full wave simulations of the cavity.
* M. Hansli, A. Penirschke, R. Jakoby, W. Kaufmann, W. Ackermann, T. Weiland, "Conceptual Design of a High Sensitive Versatile Schottky Sensor for the Collector Ring at FAIR", DIPAC2011.
 
 
TUPC092 Transverse C-band Deflecting Structure for Longitudinal Phase Space Diagnostics in the XFEL/SPring-8 “SACLA” laser, vacuum, diagnostics, emittance 1221
 
  • H. Ego
    RIKEN/SPring-8, Hyogo, Japan
  • T. Hashirano, S. Miura
    MHI, Hiroshima, Japan
  • H. Maesaka, Y. Otake
    RIKEN Spring-8 Harima, Hyogo, Japan
  • T. Sakurai
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
 
  In SPring-8, the 8 GeV compact XFEL “SACLA” is under commissioning. A single bunch of electrons is compressed down to about 30 fs for brilliant SASE X-ray lasing. It is an important key of stable lasing to investigate the longitudinal phase space and the sliced emittance of a lasing part of the bunch by using a transverse RF deflector. We developed a high gradient C-band deflecting structure operated at 5712 MHz for the bunch diagnosis with a resolution of femtosecond regime at a limited space in the SACLA. The backward travelling-wave of the HEM11-5pi/6 mode is excited in the cylindrical structure periodically loaded with racetrack-shaped irises. The featuring irises suppress rotation of the deflection plane and generate strong cell-to-cell coupling for stable resonance. Two 1.8m-long structures were fabricated and installed in the SACLA. They successfully generated a deflection voltage over 40 MV and pitched the bunch at the zero-crossing RF phase. In this paper, we present the details of the fabrication and the deflecting performance of the structures applied to the diagnosis.  
 
TUPC097 Status of Cold Cavity Beam Position Monitor for STF cavity, linac, cryomodule, vacuum 1236
 
  • E.-S. Kim, A. Heo
    KNU, Deagu, Republic of Korea
  • H. Hayano
    KEK, Ibaraki, Japan
 
  Cold cavity BPM was developed to meet high position resolution and bunch to bunch measurement time. It is designed based on re-entrant cavity and has Low-Q to achieve short signal decay time in L-band frequency with large aperture as 78mm. The beam test was performed to demonstrate position resolution at ATF main linac, which is operating with 1.6nC bunch charge, while BPM will be installed inside the ILC cyomodule with 3.2nC spacing 369ns like as ILC at STF. Stripline BPMs, ML2P and ML3P installed upstream and downstream of the BPM’s location respectively were used to predict its position. Reference cavity was optimized to use for synchronous detection. We had achieved ~340nm position resolution since position resolution was estimated due to limitation of system with noise, namely in case of ideal state. We will present configuration of beam test, procedure to measure position resolution and the result on the test. Furthermore, new design will be introduced to improve signal intensity and have heavy coupling.  
 
TUPC107 Some Preliminary Experiments using LIBERA BPMs in BEPCII* resonance, injection, kicker, feedback 1266
 
  • Y. Zhang, H.Z. Ma, J. Yue
    IHEP Beijing, Beijing, People's Republic of China
 
  Funding: Supported by the National Natural Science Foundation of China (10805051)
There are total 16 LIBERA BPMs in BEPCII, which is a double ring e+e collider. The turn-by-turn BPMs serve as only tune measurement system in most cases during normal operation. We tried to do some more machine study using them: the local coupling parameter at the BPM, the resonance driving term, the decoherence parameter which could be used to calibrate the strength of octupole in the ring. We also compare the difference from the different exciting method: single time kick with injection kicker or sinusoidal kick with feedback system.
 
 
TUPC119 A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2* cavity, dipole, simulation, extraction 1296
 
  • Y.I. Kim, H. Park
    Kyungpook National University, Daegu, Republic of Korea
  • S.T. Boogert
    Royal Holloway, University of London, Surrey, United Kingdom
  • J.C. Frisch, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White, M. Woodley
    SLAC, Menlo Park, California, USA
  • Y. Honda, R. Sugahara, T. Tauchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki, Japan
 
  Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515.
High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system.
 
 
TUPC127 Optical Transition Radiation System for ATF2 emittance, target, simulation, radiation 1317
 
  • J. Alabau-Gonzalvo, C. Blanch Gutierrez, A. Faus-Golfe, J.J. García-Garrigós
    IFIC, Valencia, Spain
  • J. Cruz, D.J. McCormick, G.R. White, M. Woodley
    SLAC, Menlo Park, California, USA
 
  Funding: Funding Agency: FPA2010-21456-C02-01 Work supported in part by Department of Energy Contract DE-AC02-76SF00515
In this paper we present the first measurements performed during the fall 2010 and early 2011 runs. Software development, simulations and hardware improvements to the Multi-Optical Transition Radiation System installed in the beam diagnostic section of the Extraction (EXT) line of ATF2 are described. 2D emittance measurements have been performed and the system is being routinely used for coupling correction. Realistic beam simulations have been made and compared with the measurements. A 4D emittance procedure, yet to be implemented, is also discussed. A demagnifier lens system to improve the beam finding procedure has been designed and will be implemented in a future run. Finally, we discuss further verification work planned for the next run period of ATF.
 
 
TUPS085 Mass Production Report of C-band Choke Mode Accelerating Structure and RF Pulse Compressor resonance, cavity, acceleration, electron 1737
 
  • S. Miura, T. Hashirano, F. Inoue, K. Okihira
    MHI, Hiroshima, Japan
  • T. Inagaki
    RIKEN/SPring-8, Hyogo, Japan
  • H. Maesaka, T. Shintake
    RIKEN Spring-8 Harima, Hyogo, Japan
 
  RIKEN and JASRI already completed the construction of XFEL/SPring8. Recently the facility was named “SACLA” (SPring-8 Angstrom Compact Free Electron LAser). The commissioning team succeeded in acceleration of 8 GeV electron beam and observation of the undulator light of 0.8 angstrom wavelength in March 2011. Now the accelerator is stably operated for the XFEL commissioning. In this project, a C-band (5712 MHz) choke mode accelerating structures and C-band RF pulse compressors are employed to obtain a high acceleration gradient of more than 35 MeV/m. We completed the fabrication of 128 accelerating structures, 64 RF pulse compressors, and 64 units of waveguide components and conducted RF measurements on them until May 2010. We report the result of the mass-production of these 64 C-Band units.  
 
TUPS103 High Temperature Radio Frequency Loads simulation, vacuum, instrumentation, impedance 1783
 
  • S. Federmann, F. Caspers, A. Grudiev, E. Montesinos, I. Syratchev
    CERN, Geneva, Switzerland
 
  In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet with 150 deg C and more than 20 bar has a certain value. Normal RF power loads containing dielectric and sensitive windows usually do not permit going much higher than 50 deg C. Here we present and discuss several design concepts for narrow-band “metal only” RF high power loads. One concept is the application of normal steel corrugated waveguides structures near cutoff .This concept could find practical use above several GHz. Another solution are resonant structures made of normal magnetic steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage the rather high losses of normal steel may also be used in coaxial line geometries with large dimensions.  
 
TUPZ001 90 m Optics Commissioning optics, proton, injection, scattering 1795
 
  • S. Cavalier
    LAL, Orsay, France
  • H. Burkhardt, M. Fitterer, G.J. Müller, S. Redaelli, R. Tomás, G. Vanbavinckhove, J. Wenninger
    CERN, Geneva, Switzerland
 
  Special β* = 90 m optics have been developed for the two very high luminosity insertions of the LHC, as a first step towards to allow for very low angle precision measurements of the proton-proton collisions in the LHC. These optics were developed to be compatible with the standard LHC injection and ramp optics. The target value of β* = 90 m is reached by an un-squeeze from the injection β* = 11 m. We describe the implementation of this optics in the LHC and the first experience in the commissioning of these optics.  
 
TUPZ026 Alternative Working Point(s) at Injection for the LHC injection, optics, quadrupole, emittance 1861
 
  • R. Calaga, R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  • R. Tomás
    CERN, Geneva, Switzerland
  • G. Vanbavinckhove
    NIKHEF, Amsterdam, The Netherlands
 
  Funding: This work partially supported by the US Department of Energy through the LHC Accelerator Research Program (LARP).
At present, the LHC operates with a different fractional tunes at injection and at collision energy due to improved dynamic aperture indicated by tracking studies. Therefore, a tune swing crossing the 10th order resonance is needed during the beta-squeeze. A new proposal to alter the working point to collision tunes already at injection and during an energy ramp is foreseen to avoid the tune jump. Simulations and measurements of the optics along with the beam emittances and lifetime are compared to the nominal injection tunes. Feasibility for a working point close to the 1/2 integer is also attempted.
 
 
WEPC001 Beam Based Sextupole Alignment Studies for Coupling Control at the ASLS sextupole, quadrupole, storage-ring, alignment 1995
 
  • R.T. Dowd, Y.E. Tan
    ASCo, Clayton, Victoria, Australia
 
  Offsets in sextupole magnets can be a significant source of coupling in a storage ring and hinder efforts to minimize vertical emittance. Beam offsets in the sextupoles at the Australian Synchrotron Light Source were measured using a response matrix analysis in LOCO with differing magnets strengths. These results were used to obtain an estimate of offset in each sextupole as well as estimate quadrupole contributions to coupling.  
 
WEPC004 Comparison of the Action and Phase Analysis on LHC Orbits with Other Techniques quadrupole, interaction-region, optics, simulation 2004
 
  • J.F. Cardona
    UNAL, Bogota D.C, Colombia
  • R. Calaga, R. Miyamoto
    BNL, Upton, Long Island, New York, USA
  • R. Tomás
    CERN, Geneva, Switzerland
  • G. Vanbavinckhove
    NIKHEF, Amsterdam, The Netherlands
 
  Funding: DIB-Universidad Nacional de Colombia
Recently acquired turn-by-turn data of the LHC is analyzed using the action and phase jump technique. The results of this analysis show a visible variation of the action and phase plots at the interaction regions from which optic error estimations can be done. In this paper error estimations will be presented and comparisons with other existing techniques in the LHC, such as the recently implemented Segment-by-segment technique, will be discussed.
 
 
WEPC013 Tests for Low Vertical Emittance at Diamond using LET Algorithm quadrupole, emittance, simulation, lattice 2031
 
  • S.M. Liuzzo, M.E. Biagini, P. Raimondi
    INFN/LNF, Frascati (Roma), Italy
  • R. Bartolini
    JAI, Oxford, United Kingdom
 
  We present measurements recently performed at the Diamond Light Source, aimed at the achievement of low vertical emittance using the Low Emittance Tuning (LET) algorithm developed for a SuperB factory project presently in progress. The tests have been focused on the comparison between this method and the LOCO algorithm currently used at Diamond. Beam position monitor tilts estimate and multiple coupling response matrices have been introduced in the algorithm in order to optimize the procedure. After few iterations using vertical correctors and skew quadrupoles, very low vertical dispersion and emittance coupling, comparable to those obtained by LOCO, have been measured.  
 
WEPC017 Vertical Beam Size Correction at the SSRF Storage Ring quadrupole, betatron, emittance, simulation 2043
 
  • M.Z. Zhang, J. Hou, B.C. Jiang, H.H. Li, S.Q. Tian
    SINAP, Shanghai, People's Republic of China
 
  Vertical beam size is an important parameter for 3rd generation light source. Correcting the vertical beam size is a realistic way to increase brightness or beam lifetime without any additional equipments in a machine under operation. The main sources of vertical beam size are betatron coupling and vertical dispersion. At the SSRF storage ring, LOCO is used for vertical dispersion and coupling measurements and corrections. The betatron coupling and vertical dispersion is corrected by skew quadrupoles that calculated by LOCO. Vertical beam size can be changed from 10s um to several um for different purposes. Touschek lifetime is also measured to testify the vertical beam size. Simulations show that if smaller vertical beam size is required, more skew quadrupoles are needed.  
 
WEPC024 LOCO in the ALBA Storage Ring quadrupole, dipole, optics, storage-ring 2055
 
  • G. Benedetti, D. Einfeld, Z. Martí, M. Muñoz
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
 
  ALBA is a 3 GeV 3rd generation light source which achieved first stored beam in February 2011, and will be commissioned during 2011. The ring comprises of 112 independent quadrupoles grouped in 14 families and 32 combined gradient dipoles powered in series. This paper reviews the process of recovering the design lattice and the symmetry of the machine, and the effects on orbit and lifetime. The main tool employ for this has been the LOCO implementation provided in the Matlab MiddleLayer. First results shows that the main effect on the symmetry is the difference between bending magnets. As this effect can not be compensated locally at present at the bendings, a global optics correction using all the quadrupoles is used.  
 
WEPC033 Decoupling Problem of Weakly Linear Coupled Double Mini-beta-y Lattice of TPS Storage Ring lattice, betatron, storage-ring, resonance 2076
 
  • H.-P. Chang, C.C. Chiang, M.-S. Chiu
    NSRRC, Hsinchu, Taiwan
 
  Three double mini-beta-y (DMBy) lattice design of the TPS storage ring is in progress to enhance the photon sources at three of the six long straight sections. For the estimation of Touschek beam lifetime, the TRACY code is used to calculate the momentum acceptance of the linear coupled TPS 3-DMBy lattice. The weak linear coupling was generated by adding some random skew quadrupoles at all quadrupole locations in order to create 1% coupling. Using the Teng’s symplectic rotation form in program may cause trouble in decoupling the one-turn coupled matrix. This report describes how we solve this decoupling problem and some useful references and comments are also presented.  
 
WEPC050 New Optics for the SOLEIL Storage Ring optics, injection, undulator, vacuum 2124
 
  • P. Brunelle, F. Briquez, A. Loulergue, O. Marcouillé, A. Nadji, L.S. Nadolski, M.-A. Tordeux, J.F. Zhang
    SOLEIL, Gif-sur-Yvette, France
 
  SOLEIL, the French 2.75GeV synchrotron light source is delivering photons to 24 beam lines and is presently equipped with 22 insertion devices (ID) including a high field and small gap in-vacuum wiggler*. This paper presents the continuous work performed to reduce the strong non linear effects of several IDs. On one side, the ID defaults have been precisely identified using on-beam measurements, and magnetic correction developments are going on, especially for the in-vacuum wiggler and for the 10m long HU640 undulator. On the other side, a new optics has been optimised in terms of beta-functions (at the ID location) and non linear dynamics in order to improve the injection efficiency and the beam lifetime in the presence of IDs. The modified optics has been used daily in operation since November 2010 and ensures a beam lifetime greater than 10h for a 400mA stored beam with the users ID configuration. In parallel, an extensive experimental optimization has been performed to prepare the operation with an additional quadrupole triplet that provides double low vertical beta functions in one long straight section that will accommodate two canted in-vacuum insertion devices**.
* O. Marcouillé et al., IPAC10, p. 3102 (2010).
** A. Loulergue et al., IPAC10, p. 2496 (2010).
 
 
WEPC069 Impact of Nonlinear Resonances on Beam Dynamics at the SPring-8 Storage Ring injection, resonance, storage-ring, betatron 2181
 
  • M. Takao, J. Schimizu, Y. Shimosaki, K. Soutome
    JASRI/SPring-8, Hyogo-ken, Japan
 
  For a low emittance storage ring like high brilliant light sources, the improvement of nonlinear beam dynamics is necessary for the stable operation, or for providing large dynamic aperture and momentum acceptance for efficient injection and long Touschek lifetime. At the SPring-8 storage ring it is observed that injection efficiency is affected by the gap heights of the magnet arrays of the in-vacuum insertion devices. The fact that the injected beam of fundamentally oscillating in horizontal direction is limited by the vertical aperture means that coupling resonances influence the beam dynamics. To clarify the phenomena, we studied the nonlinear beam dynamics of transverse betatron motion by means of turn-by-turn method. Then, we found some nonlinear coupling resonances, such as the one by skew sextupole field, are excited to enhance vertical oscillation and to deteriorate the injection efficiency. By analyzing these results, we developed measures to suppress the effect of the nonlinear coupling resonances and to improve the injection efficiency.  
 
WEPC071 The Motion of an Electron in the Periodic Cusped Magnetic Fields electron, wiggler, focusing, betatron 2184
 
  • G. Du, B.L. Qian, H. Wang
    National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
 
  Funding: National High Technology Research and Development Program of P. R. China
The motion and its stability of an electron in the periodic cusped magnetic fields have been analyzed theoretically and calculated numerically, as the stability could not be well predicted by the Mathieu’s equation to guide the design of the magnetic focusing system for the propagation of the sheet electron beams in the waveguides. The precise solution to the motion equations of the electron has been obtained by iteration. To validate the analytical solution and to evaluate the stability of the motion, numerical calculations have been carried out. And the results show that the analytical solution is reliable, and there is only one stable region in the (p0, B0) space, where the parameter p0 is the period of the magnetic fields, and B0 is the magnitude of the magnetic fields. Besides, the stability of the electron motion would become weaker while the initial distance between the electron and the axis becomes larger. These results are interesting to the area of the sheet-electron-beam microwave sources focused by the periodical cusped magnetic fields.
 
 
WEPC097 A Concatenation Scheme for the Computation of Beam Excited Higher Order Mode Port Signals cavity, HOM, wakefield, higher-order-mode 2238
 
  • T. Flisgen, H.-W. Glock, U. van Rienen
    Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
 
  Ongoing studies investigate in how far higher order mode (HOM) port signals of superconducting RF cavities can be used for machine and beam diagnostics. Apart from experiments e.g. at the FLASH facility at DESY in Hamburg, numerical modelling is needed for the prediction of HOM coupler signals. For this purpose, the RF properties of the entire accelerating module have to be taken into account, since higher order modes can propagate along the cavity chain. A discretization of the full chain, followed by a wake field simulation is only feasible with powerful and expensive cluster computers. Instead, an element wise wake field simulation of sub-sections of the chain, followed by a suitable concatenation scheme can be performed on standard hardware assuming the beam to be sufficiently stiff. In this paper a concatenation scheme for the computation of beam excited HOM port signals is derived as a generalization of the Coupled S-Parameter scheme CSC. Furthermore, the validity of the method is shown for a sample structure.  
 
WEPO014 Magnetic Design of Quadrupoles for the Medium and High Energy Beam Transport line of the LIPAC Accelerator quadrupole, beam-transport, simulation, dipole 2424
 
  • C. Oliver, B. Brañas, A. Ibarra, I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
 
  Funding: Work partially supported by Spanish Ministry of Science and Innovation under project AIC10-A-000441 and ENE2009-11230.
The LIPAC accelerator will be a 9 MeV, 125 mA cw deuteron accelerator which will verify the validity of the design of the future IFMIF accelerator. A Medium Energy Beam Transport line (MEBT) is necessary to handle the high current beam from the RFQ to the Superconducting RF accelerating cavities (SRF) whereas a High Energy Beam Transport line (HEBT) is used to match the beam from the SRF to the beam dump. The high space charge and beam power determine the beam dynamics in both transport lines. As a consequence, magnets with strong fields in a reduced space are required. Along the transport beamlines, there are different types of quadrupoles with steerers and a dipole. Special care is devoted to maximize the integrated fields in the available space. Both 2-D and 3-D magnetic calculations are used to optimize coil configurations. Magnetic performance and cost, both of magnet and power supply, have been taken into account for final choice. In this paper, the design of the resistive quadrupoles of the MEBT and HEBT of the LIPAC accelerator is presented.
 
 
WEPO036 Design of a Cryogenic Regulation Valve Box for SRF Operation at TPS SRF, cryogenics, cavity, feedback 2475
 
  • M.H. Chang, L.-H. Chang, L.J. Chen, F.-T. Chung, F. Z. Hsiao, M.-C. Lin, Y.-H. Lin, C.H. Lo, H.H. Tsai, Ch. Wang, T.-T. Yang, M.-S. Yeh, T.-C. Yu
    NSRRC, Hsinchu, Taiwan
  • L.L. Han, M.H. Tsai
    NTUT, Taiwan
 
  A 3-GeV light source named Taiwan Photon Source (TPS) at National Synchrotron Radiation Research Center (NSRRC) is under construction, and is scheduled for commissioning in 2013/2014. An SRF module of KEKB type has been selected for the TPS as the accelerating cavity of its storage ring. The SRF valve boxes, as part of the cryogenic transfer system, stabilize the cryogenic operational conditions required for various needs of SRF operation. The SRF operation requires a large dynamic variation in the cryogenic loading that challenges appropriate sizing of the cryogenic regulation valves to minimize the pressure drop and concurrently to maintain a fine regulation of pressure. Here, we report our design considerations for an SRF valve box with emphasis on highly stabilizing the helium pressure for SRF operation with a dual-return valve scheme. The estimated fluctuations of pressure due to finite accuracy of the valve opening decrease to a tenth of what is obtained from the conventional single return-valve scheme.  
 
WEPS036 First Coupled CH Power Cavity for the FAIR Proton Injector cavity, linac, proton, DTL 2565
 
  • R. M. Brodhage, C. Fix, H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • G. Clemente, L. Groening
    GSI, Darmstadt, Germany
 
  For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The main acceleration of this room temperature linac will be provided by six CH cavities operated at 325 MHz. Each cavity will be powered by a 2.5 MW Klystron. For the second acceleration unit from 11.5 MeV to 24.2 MeV a 1:2 scaled model has been built. Low level RF measurements have been performed to determine the main parameters and to prove the concept of coupled CH cavities. For this second tank technical and mechanical investigations have been performed in 2010 to develop a complete technical concept for the manufacturing. In Spring 2011, the construction of the first power prototype has started. The main components of this cavity will be ready for measurements in summer 2011. At that time, the cavity will be tested with a preliminary aluminum drift tube structure, which will allow precise frequency and field tuning. This paper will report on the recent technical development and achievements. It will outline the main fabrication steps towards that novel type of proton DTL. Also first low level RF measurements are expected.  
 
WEPZ004 Solid Pulse Transforming Line for DWA impedance, simulation, induction, high-voltage 2769
 
  • L. Zhang
    CAEP/IFP, Mainyang, Sichuan, People's Republic of China
 
  This paper introduces the research work about solid pulse transforming line for dielectric wall accelerator(DWA). We will discuss the impedence of the solid pulse transforming line due to different material. Some research of PCSS(photoconductive semiconductor switch),which was used for DWA, will also be described.  
 
THXA01 Recent Trends in Accelerator Control Systems controls, EPICS, LLRF, feedback 2844
 
  • I. Verstovšek, F. Amand, M. Pleško, K. Žagar
    Cosylab, Ljubljana, Slovenia
 
  The talk will discuss the approaches of different accelerators, such as FAIR, ESS, MedAustron, XFEL, etc. An overview of different approaches will be given with an emphasis of the recent spectrum of various realizations of accelerator control systems. The talk will not be limited to open source and off-the-shelf software frameworks only but will touch all trends in modern accelerators, including recent trends in hardware. The role of the control system will be highlighted as a common integration framework for various applications, with an emphasis on its increased complexity and scale, and the need for improved reliability and an appropriate service. How control systems can help support the requirements-shaping process early in the project will also be discussed.  
slides icon Slides THXA01 [1.535 MB]  
 
THPC056 Orbit Studies during ALBA Commissioning feedback, alignment, quadrupole, brilliance 3020
 
  • M. Muñoz, G. Benedetti, D. Einfeld, Z. Martí
    CELLS-ALBA Synchrotron, Cerdanyola del Vallès, Spain
 
  The 3rd generation light source ALBA is in the commissioning stage. This paper review the results of the commissioning concerning the transversal beam behavior, in particular the orbit correction system, results from the beam based alignment (BBA), and coupling. The orbit control system of ALBA consists of 88 horizontal and vertical correctors, mounted as extra coils in the sextupole magnets, up to 104 LIBERA BPMs (brilliance version). The correctors magnets would be used for both static orbit correction and for the fast orbit feedback mode, providing up to 1 mrad of correction in the static case. In phase one of the commissioning, the orbit has been corrected down to values of 50 um rms, with an estimated emittance ratio in the order of 1% .  
 
THPC062 SLS Vertical Emittance Tuning alignment, quadrupole, emittance, betatron 3035
 
  • M. Böge, M. Aiba, N. Milas, A. Streun
    PSI, Villigen, Switzerland
  • S.M. Liuzzo
    INFN/LNF, Frascati (Roma), Italy
 
  To establish ultra-small vertical emittances (<1pmrad @2.86GeV) is one important aim of future linear collider damping ring optimization studies* at the SLS. By utilizing various correction techniques the SLS is already close to this goal with emittances of <2pm.rad @2.4GeV under the constraint of maintaining user operation conditions. One of the limiting contributions is the remaining spurious vertical dispersion etay of ~1.4mm which can be reduced by careful re-alignment and the application of dispersion-free steering techniques. The latter require orbit manipulations which are only partially compatible with the user operation mode. A first application of dispersion-free steering techniques demonstrates that etay can be reduced to <1mm at the expense of large orbit excursions which require a simultaneous betatron-coupling correction by means of skew quadrupoles in order to benefit in terms of a further reduction of vertical emittance. Therefore possible girder and magnet misalignments are analyzed in simulation which allows to localize the sources of etay and to eliminate them by re-alignment. Following this path the goal to achieve emittances close to 1pmrad is within reach.
* In January 2011 the EU-project TIARA (Test Infrastructure and Accelerator Research Area) started with contributions from the SLS as part of the SVET (SLS Vertical Emittance Tuning) work package WP6.
 
 
THPC074 Dynamic Aperture and Tolerances for PEP-X Ultimate Storage Ring Design sextupole, dynamic-aperture, resonance, quadrupole 3065
 
  • M.-H. Wang, Y. Cai, R.O. Hettel, Y. Nosochkov
    SLAC, Menlo Park, California, USA
  • M. Borland
    ANL, Argonne, USA
 
  Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515.
A lattice for the PEP-X ultimate storage ring light source[1], having 11 pm-rad natural emittance at a beam energy of 4.5 GeV at zero current, using 90 m of damping wiggler and fitting into the existing 2.2-km PEP-II tunnel, has been recently designed[2]. Such a low emittance lattice requires very strong sextupoles for chromaticity correction, which in turn introduce strong non-linear field effects that limit the beam dynamic aperture. In order to maximize the dynamic aperture we choose the cell phases to cancel the third and fourth order geometric resonances in each 8-cell arc. Four families of chromatic sextupoles and six families of geometric (or harmonic) sextupoles are added to correct the chromatic and amplitude-dependent tunes. To find the best settings of the ten sextupole families, we use a Multi-Objective Genetic Optimizer employing elegant[3] to optimize the beam lifetime and dynamic aperture simultaneously. Then we evaluate dynamic aperture reduction caused by magnetic field multipole errors, magnet fabrication errors and misalignments. A sufficient dynamic aperture is obtained for injection, as well as workable beam lifetime[2].
 
 
THPC085 Effect of mirror-tilt on the mode-structure in an oscillator FEL FEL, cavity, simulation, alignment 3092
 
  • S. Krishnagopal, S.A. Samant
    BARC, Mumbai, India
 
  In an oscillator free-electron laser (FEL) the power coupled out depends strongly on the mode configuration at the out-coupling mirror. This mode configuration is affected by many parameters such as the resonator configuration, FEL wavelength, etc. In addition, mirror alignment also plays an important role in determining the mode structure. In this paper we use three-dimensional simulations (GENESIS+OPC), to study the effect of mirror tilt on the out-coupled power. We find that mirror-tilt can severely distort the mode, and can introduce non-Gaussian, non-axisymmetric modes. In this regard the confocal configuration is more robust compared to the concentric.  
 
THPC121 Design and Cold Tests of a Prototype photocathode RF Gun for Shanghai SXFEL Facility gun, cathode, vacuum, emittance 3170
 
  • H.J. Qian, H. Chen, Y.-C. Du, W.-H. Huang, C. Li, X.H. Liu, X. H. Lu, C.-X. Tang
    TUB, Beijing, People's Republic of China
 
  A soft X-ray (~9 nm) FEL (SXFEL) facility is going to be constructed in Shanghai, China, which requires high charge (>500 pC) electron beam with low transverse emittance (<1.5 mm-mrad) at photoinjector exit. One of the keys to achieve a low emittance with high charge is high gradient on the photocathode, so an S-band photocathode RF gun modified from BNL type gun is designed, which aims running 100 MV/m peak gradient at 10 Hz. By changing the cathode seal technique, removing the insertion RF tuner, and reducing the peak surface field, RF breakdown possibility is reduced. Besides, RF pulse width is also considered to be reduced to lower the RF breakdown possibility. Since zero mode and multipole field degrades the beam emittance, they are also suppressed in the new gun design. Design details and cold testing results are presented in this paper.  
 
THPO029 Microwave Beating Generated by a Dual Beam Accelerator beat-wave, plasma, electron, impedance 3406
 
  • G.L. Li, Z.X. Jin, L. Liu, T. Shu, J.H. Yang, C.W. Yuan, J. Zhang
    National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
 
  Funding: National University of Defense Technology
As high power microwave (HPM) technologies gradually matured, the technologies for enhancing the output capacity of HPMs are becoming more and more attractive. However, limited by physics and technology, the approaches for enhancing the output capacity with a single HPM source have encountered difficulties. An alternative method for enhancing the output capacity of HPM sources is the coupling output of dual channel HPM sources. However, if the microwave sources have some coupling with each other, they maybe inter modulate with each other, and the phase-locking of the HPM sources may occur. In order to make sure that the beat waves are generating on the right way, a waveguide diplexer is introduced. Each channel has disjoint pass frequency band, and dual-channel HPM sources are isolated. As the dual-channel electron beams are driven by one accelerator, the HPM sources are expected to have a better match with the accelerator, and even higher microwave power is possible. In the high power experiments, the radiated powers of the beat waves are measured to be about 4.3 GW, 40 ns, the frequencies are about 9.41 GHz and 9.59 GHz.
Correspondence: Guolin Li, College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha, 410073, P. R. China. Email: nudt-liguolin@hotmail.com
 
 
THPS033 Skew Quadrupole Effects on Multi-turn injection Efficiency in the SIS18 quadrupole, septum, injection, emittance 3490
 
  • W.M. Daqa, I. Hofmann, J. Struckmeier
    GSI, Darmstadt, Germany
 
  Funding: DAAD ( Deutscher Akademischer Austausch Dienst)
One goal of the SIS18 upgrade scheme is concerned about improving the multi-turn injection (MTI) efficiency, in order to reach the required intensities at the targets and to operate effectively as a booster for SIS100. To improve the limitation of the MTI scheme, there were successful attempts in AGS and PS boosters, to use the skew injection scheme and later it was suggested for SIS18. The strength of the skew quadrupoles is optimized together with the horizontal tune, the difference in horizontal to vertical tunes, the incoming beam parameters and the geometrical limitation of SIS lattice. A good optimization implies the emittance exchange, due to linear coupling, to take place partially and just before the return of the beamlet back to its original position at the septum. The present work was done by simulation using the code PARMTRA and compared with measurements. The results show that, depending on the working point, the skew injection scheme can improve the MTI efficiency from 2% up to 12%, taking into account the loss on the septum from inside and on the vertical acceptance.
 
 
THPS065 Upgraded X-band 950 KeV Linac X-ray Source for On-site Inspection at Petrochemical Complex linac, status, shielding, site 3574
 
  • M. Jin, K. Demachi, K. Dobashi, H.F. Jin, T. Natsui, M. Uesaka
    The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
  • J. Kusano, N. Nakamura, M. Yamamoto
    Accuthera Inc., Kawasaki, Kanagawa, Japan
  • E. Tanabe
    AET, Kawasaki-City, Japan
 
  Abstract―Our portable X-band (9.3GHz) 950KeV linac has been successfully upgraded. The problems of RF power oscillation, beam current oscillation and reduction and finally lack of X-ray intensity were solved by replacing the axial coupling cavities with the side-coupled ones. Designed X-ray dose rate of 0.05 Sv/min@1m is going to be achieved. Length of the accelerating tube is reduced to less than 25 cm. X-ray source part with the local radiation shielding is connected by the flexible waveguide with the box of the 300 kW magnetron and cooling unit. The total system consists of the three suit-case-size units, the last of which is one for the electric power supply. Even on-line dynamic transmission imaging is available by using the high intensity X-ray camera. Demonstration of the measurement of wall thinning of metal pipes with thick thermal shielding is under way. Updated measurement results will be presented. KEYWORDS: portable X-band linac X-ray source, on-site high energy X-ray inspection, petrochemical complex  
 
THPZ004 DAΦNE Tune-up for the KLOE-2 Experiment luminosity, background, closed-orbit, wiggler 3687
 
  • C. Milardi, D. Alesini, M.E. Biagini, S. Bini, C. Biscari, R. Boni, M. Boscolo, B. Buonomo, A. Clozza, G.O. Delle Monache, T. Demma, E. Di Pasquale, G. Di Pirro, A. Drago, M. Esposito, L.G. Foggetta, A. Gallo, A. Ghigo, S. Guiducci, C. Ligi, S.M. Liuzzo, F. Marcellini, G. Mazzitelli, L. Pellegrino, M.A. Preger, L. Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov
    INFN/LNF, Frascati (Roma), Italy
  • S. Bettoni
    PSI, Villigen, Switzerland
 
  Funding: Work supported by the EuCARD research programme within the 'Assessment of Novel Accelerator Concepts' work package (ANAC-WP11).
In its continuous evolution DAΦNE, the Frascati lepton collider, is starting a new run for the KLOE-2 experiment, an upgraded version of the KLOE one. A new interaction region, based on the high luminosity Crab-Waist collision scheme, has been designed, built and installed. Several machine subsystems have been revised according to innovative design concepts in order to improve beam dynamics. Collimators and shieldings have been upgraded in order to minimize the background rates on the detector during coasting as well as injection operation. A wide measurement campaign has been undertaken to verify and quantify the effect of the modifications and to tune-up the collider in view of the 3 years long data-taking foreseen to deliver ~5 fb-1 to the experiment.
 
 
THPZ012 Luminosity Enhancement and Performance in BEPCII luminosity, background, quadrupole, optics 3708
 
  • Q. Qin, J. Cao, J. Cheng, Y.L. Chi, H. Dong, Z. Duan, D. Ji, W. Kang, S.P. Li, L. Ma, H. Qu, C.H. Wang, G.W. Wang, J.Q. Wang, X.H. Wang, Y. Wei, J. Xing, G. Xu, C.H. Yu, J. Yue, C. Zhang, Y. Zhang
    IHEP Beijing, Beijing, People's Republic of China
 
  The Beijing Electron Positron Collider (BEPC) was upgraded to a factory-like machine –- BEPCII, during last several years. From last November, the BEPCII was commissioned again for its luminosity. Efforts on optics correction including optimizing the strengths of superconducting quadrupoles near the IP, orbits correction concerning beam energy, etc, make the transvers tunes possible to move very close to half integer, bringing a big luminosity increase. The background of the detector is also reduced with beam commissioning, and finally fit the requirements of data taking. Further luminosity commissioing, including coupling optimization, beta-waist tuning, was carried on, and the luminosity reached 6.49·1032 cm-2 s-1 during routine operation. Some measures of luminosity enhancement and the luminosity related accelerator physics issues will be discussed.