MOPA —  Poster in Room 201 on Monday   (01-Oct-12   16:20—17:50)
Final Design of the Striplines for the Extraction Kicker of the CLIC Damping Rings
  • C. Belver-Aguilar, A. Faus-Golfe
    IFIC, Valencia, Spain
  • M.J. Barnes
    CERN, Geneva, Switzerland
  • I. Podadera, F. Toral
    CIEMAT, Madrid, Spain
  Pre-Damping Rings (PDR) and Damping Rings (DR) are required to reduce beam emittance and, therefore, to achieve the luminosity requirements for the CLIC main linac. Kicker systems will be used to inject and extract the beam from the PDRs and DRs: the most challenging of these is the DR extraction kicker system. In this paper we present results from a comprehensive set of 3D analyses of the striplines for the DR extraction kicker, including studies of tapering of the electrodes, an estimate of the power loss in the coaxial feedthroughs and beam coupling impedance calculations for a tapered beam pipe. Furthermore the required mechanical tolerances for the stripline are also presented. Prototype striplines will be manufactured, to the specified tolerances, and will be available for tests from December 2012: it is planned to measure field stability, field homogeneity and beam coupling impedance. Measurements will be carried out in the laboratory and in both the ALBA and ATF2 facilities.  
270 degree Electron Beam Bending System using Two Sector Magnets for Therapy Application
  • S.D. Dhole, S. Akhter, V.N. Bhoraskar, B.J. Patil
    University of Pune, Pune, India
  • S.T. Chavan, R. Krishnan, S.N. Pethe
    SAMEER, Mumbai, India
  The 270 degree doubly achromatic beam bending magnet system using two sector magnets has been designed mainly for treating cancer and skin diseases. The main requirements of the design of two magnet system is to focus an electron beam having a spot size less than 3 mm X 3 mm, energy spread within 3% and divergence angle <= 3 mrad at the target. To achieve these parameters the simulation was carried out using Lorentz-3EM software. The beam spot, divergence angle and energy spread were observed with respect to the variation in angles of sector magnets and drift distance. From the simulated results, it has been optimized that the first and second magnet has an angle 195 degree and 75 degree and the drift distance 64 mm. It is also observed that at the 1396, 2878 and 4677 A-turn, the optimized design produces 3324, 6221 and 9317 Gauss of magnetic field at median plane require to bend 6, 12 and 18 MeV electron respectively. The output parameters of the optimized design are energy spread 3 %, divergence angle ~ 2.8 mrad and spot size 2.6 mm.  
Beam Diagnostics for PAL-XFEL
  • C. Kim, H. J. Choi, J.Y. Choi, J.Y. Huang, H.-S. Kang, D.T. Kim, I.S. Ko, E.H. Lee, B.R. Park, J.C. Yoon
    PAL, Pohang, Kyungbuk, Republic of Korea
  Pohang Accelerator Laboratory started its XFEL program from 2011. The XFEL project in Pohang Accelerator Laboratory (PAL) requires low beam-emittance, ultra-short bunch length, high peak current, high stability of beam energy. Therefore, beam diagnostics for SASE XFEL should be, focused on attaining femto-second precision in the measurement of temporal beam parameters, and sub-micrometer precision in beam position measurement. Charge measurement and energy measurement and their feedback are important as well. In this work, technical concepts regarding the diagnostic monitors will be summarized and present status of them will be described.  
An Electron Beam Profile Monitor for the Race-track Microtron
  • S.D. Dhole, V.N. Bhoraskar, B.J. Patil, N.S. Shinde
    University of Pune, Pune, India
  In electron irradiation experiments on materials such as semiconductors, solar cells etc., an uniformity and the charge distribution in the electron beam is very important. Therefore, an electron beam current monitor and its electronic system have been designed and built to measure the distribution of a beam current either in the horizontal or vertical direction along with the beam dimensions. To obtain X-Y beam profile, a special type of Faraday Cup was designed which mainly consists of charge collecting electrodes made up of thin copper strips. Each strip having dimensions 0.5 mm wide, 4 mm thick and 20 mm long were fixed parallel to each other and separation between them was ~ 0.5 mm. This multi electrode Faraday was mounted at the extraction port of the Race Track Microtron, where 1 MeV electron beam allowed to fall on it. The beam characterization in the form of current and uniformity were measured. The current from each strip were measured using an electronic circuit developed based on the multiplexing principle. The uniformity of the beam can be measured with an accuracy of 10%. The minimum and maximum dimensions which can be measured are 3 mm and 15 mm respectively.  
X-ray Diagnostic of High-current Low-energy Electron Beam in Plasma
  • S.A. Cherenshchykov, V.D. Kotsubanov
    NSC/KIPT, Kharkov, Ukraine
  Low-energy high-current electron beams are used in a novel technology for surface modification of metallic materials. Propagation high current electron beam in plasma give possibility for much current increasing. Direct diagnostic by a Faraday cup in plasma is incorrect. Therefore we used for beam diagnostic X-ray radiation from a metal target. The electron beam was creating by a cold-cathode magnetron injection gun. The gun voltage was nearly 20 kV. The target current was up to 20 kA. We observed X-ray radiation by its transformation in visible light. Plastic scintillators were used for high time resolution. A cross section of beam and time dependences was obtained too. For time dependence resolution was used digital oscillograph Tektronix. Photomultiplier tubes were used for light detection. Their signal was write together with target current by the Faraday cup and visible light emission. We observed in oscillograms X-ray radiation without target current and target current without X-ray radiation with duration up several microseconds. The diagnostic method will be use for next improvement cold-cathode magnetron injection gun as source of low-energy high-current electron beam.  
VIMOS, New Capabilities for a Dedicated Optical Safety System
  • K. Thomsen
    PSI, Villigen, Switzerland
  VIMOS is a dedicated safety system developed at the Spallation Neutron Source SINQ at the Paul Scherrer Institut, PSI, in Switzerland. VIMOS very directly monitors the correct current density distribution of the proton beam on the target by sampling the light emitted from a glowing mesh heated by the passing protons. The design has been optimized for obtaining maximum sensitivity and timely detection of beam irregularities relying on standard well-proven components. Recently it has been demonstrated that technical boundary conditions like radiation level and signal strength should allow for upgrading the system to a sensitive diagnostic device delivering quantitative and image-resolved values for the proton current density distribution on the SINQ target. By determining the temperature of the glowing mesh from the signals in two separate wavelength bands the temperature distribution over the mesh can be derived und subsequently the incident proton beam current density distribution. Work aimed at investigating the feasibility of adding these diagnostic abilities to VIMOS shows initial promising results. The status of the project and preliminary findings will be reported.  
Development of a Phase Probe for the Small Cyclotron HM-18 at NIRS
  • S. Hojo, A. Goto, T. Honma, K. Katagiri, A. Sugiura
    NIRS, Chiba-shi, Japan
  • Y. Takahashi
    AEC, Chiba, Japan
  The small cyclotron HM-18 of the National Institute of Radiological Sciences (NIRS) has been operated for use in RI production since 1994. The HM-18 allows us to accelerate protons and deuterons at fixed energies of 18 and 9 MeV, respectively. It has four trim coils for generation of the isochronous fields. Until recently, currents of the four trim coils had been adjusted only by monitoring the output beam intensity. In order to exactly produce the isochronous fields, a new phase probe has been installed in the HM-18. The phase probe has a simple structure in which four copper electrode plates of 60 mm x70 mm in area are glued to a copper base plate with a polyimide insulator between them. The thicknesses of the copper plates and the polyimide are 0.1 mm. This structure has an advantage that it can be easily installed in the cyclotron; only one part of a pair of upper and lower electrodes, which is usually adopted, is simply attached on the surface of the (lower) sector pole. The development of the phase probe and some results of a preliminary beam test using it are reported.  
Various Usages of Wall Current Monitors for Commissioning of RF Systems in J-PARC Synchrotrons
  • F. Tamura, M. Nomura, A. Schnase, T. Shimada, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • K. Hara, K. Hasegawa, C. Ohmori, M. Toda, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
  Wall current monitors (WCM) for rf system commissioning are installed in the J-PARC synchrotrons, the RCS and the MR. The WCM signals are used as the input of the beam loading compensation system, and also used diagnosis to adjust the rf system parameters. Since the rf and beam frequency is in the range of a few MHz, direct measurement of the WCM signals is possible. For the diagnosis, the WCM signals are taken by an oscilloscope with the revolution clock signal generated by the LLRF control system, and slices of the WCM waveform with lengths of the revolution periods are generated. By stacking the slices, one can get a mountain plot, which shows motions of bunches and variations of the bunch shapes. Also, time variations of the bunching factor, which are important for acceleration of high intensity proton beams, are obtained. The harmonic analysis is performed on the WCM signal and the cavity voltage monitor signal. By using complex amplitudes of them, one can calculate the impedance seen by the beam. In this presentation, we show examples of the analyses described above. The rf parameters for high intensity beams have been successfully adjusted by using these analyses.  
Comparison of Three Different Concepts of High Dynamic Range and Dependability Optimised Current Measurement Digitisers for Beam Loss Systems
  • W. Vigano, B. Dehning, E. Effinger, G.G. Venturini, C. Zamantzas
    CERN, Geneva, Switzerland
  The first concept is based on current to frequency conversion, enhanced with an ADC for extending the dynamic range and decreasing the response time. A summary of 3 years worth of operational experience with such a system for LHC beam loss monitoring will be given. The second principle is based on an adaptive current to frequency converter implemented in an ASIC. The basic parameters of the circuit are discussed and compared with measurements. Several measures are taken to harden both circuits against single event effects and to make them tolerant for operation in radioactive environments. The third circuit is based on a fully differential integrator for enhanced dynamic range, where laboratory and test installation measurements will be presented. All circuits are designed to avoid any dead time in the acquisition and have reliability and fail safe operational considerations taken into account.  
Diamond Detectors
  • E. Griesmayer
    CIVIDEC Instrumentation, Wien, Austria
  • B. Dehning
    CERN, Geneva, Switzerland
  Funding: CIVIDEC Instrumentation GmbH
Diamond is perhaps the most versatile, efficient and radiation-tolerant material available for use in beam detectors. Correspondingly, it has a wide range of applications in beam instrumentation. Numerous practical applications have demonstrated the exceptional sensitivity of diamond to charged particles, photons and neutrons. Some examples will be given including the latest measurements made with the Diamond Beam Loss Monitors at the LHC and the impact of diamond detectors on the observation of the Higgs candidate at CERN.
The Linearity Calibration of the PMT Using Synchrotron Light
  • C. Liu, Y.B. Leng, L.Y. Yu
    SINAP, Shanghai, People's Republic of China
  A fiber-based Cerenkov beam loss monitor has been widely used in the world for FEL facilities to monitor electron beam losses. As a key component, Photomultiplier (PMT) is employed to detect the Cerenkov light emitted by the secondary charge particles. The linearity of the PMT has to be calibrated precisely due to its strong impact to the position accuracy and sensitivity of the whole system. Synchrotron radiation is therefore a perfect calibration source with fine linearity and large intensity scale. The preliminary calibration result of PMT using synchrotron light at SSRF will be presented in this paper.  
Characterization of a Wide Dynamic-range, Radiation-tolerant Charge-digitizer ASIC for Monitoring of Beam Losses
  • G.G. Venturini, F. Anghinolfi, B. Dehning
    CERN, Geneva, Switzerland
  • M. Kayal
    EPFL, Lausanne, Switzerland
  An Application Specific Integrated Circuit (ASIC) has been designed and fabricated to provide a compact solution to digitize current signals from ionization chambers and diamond detectors, employed as beam loss monitors at CERN and several other high energy physics facilities. The circuit topology has been devised to accept positive and negative currents, to have a wide dynamic range (above 120 dB), withstand radiation levels over 100kGy and offer different modes of operation, covering a broad range of applications. Furthermore, an internal conversion reference is employed in the digitization, to provide an accurate absolute measurement. This paper discusses the detailed characterization of the first prototype: linearity, radiation tolerance and temperature dependence of the conversion, as well as implications and system-level considerations regarding its use for beam instrumentation applications in a high energy physics facility.  
Real-time Calculation of Scale Factors of X-ray Beam Position Monitors during User Operation
  • C. Bloomer, G. Rehm
    Diamond, Oxfordshire, United Kingdom
  Photoemission based X-ray Beam Position Monitors (XBPMs) are widely used at 3rd generation light sources to both monitor and stabilise the photon beam to sub-micron precision. Traditionally, finding the geometric scale factors requires either systematic stepper motor movements of the XBPM or well controlled electron beam displacements to measure the response of the XBPM. For each Insertion Device gap it is required to repeat this in order to build up a complete set of scale factors covering all possible operating conditions. Elliptically Polarising Undulators further complicate matters by having multiple operating modes which would require multi dimensional lookup tables. Presented in this paper is a method for retrieving the geometric scale factors of an XBPM in real time by making use of the intrinsic small random movements of the electron beam and finding the correlation in synchronous measurements from Electron BPMs and XBPMs at kHz sample rates.  
Development of the New Electronic Instrumentation for the LIPAc/IFMIF Beam Position Monitors
  • A. Guirao, J.M. Carmona, L.M. Martinez, I. Podadera
    CIEMAT, Madrid, Spain
  Funding: Work partially supported by the Spanish Ministry of Science and Innovation under project AIC10-A-000441 and ENE2009-11230
Among all the LIPAc/IFMIF accelerator diagnostics instrumentation, the Beam Position Monitors are a key stone for its operation. A new approach for the LIPAc/IFMIF beam position monitors acquisition electronics is proposed for the twenty BPM stations distributed along the accelerator. The new system under development is a fully digital instrumentation which incorporates automatic calibration of the monitors' signals and allows monitoring of both fundamental and second signal harmonics. The current state of the development and first experimental results of the system on the test bench will be presented.
New Electronics Design for the European XFEL Re-entrant Cavity Beam Position Monitor
  • C.S. Simon
    CEA/DSM/IRFU, France
  • R. Baldinger, B. Keil, R. Kramert, G. Marinkovic, M. Roggli, M. Stadler
    PSI, Villigen, Switzerland
  About one third of the beam position monitors (BPMs) in the European XFEL (E-XFEL) cryomodules will be re-entrant cavities. The BPM mechanics and Radio-Frequency front-end (RFFE) electronics are developed by CEA/Saclay. Two RFFEs and a digital back-end with two ADC mezzanines are integrated into a compact standalone unit called MBU (modular BPM unit) developed by PSI. The signal processing uses hybrids and a single stage downconversion to generate the signals sum and delta. Every RF/analog component of the re-entrant BPM electronics has been simulated with a Mathcad model and tested independently on test benches. The very low Q of the cavity monopole mode allows the new electronics to filter this mode at the dipole mode frequency and an IQ demodulation for delta and sum channels allow the digital back-end to determine the sign of the beam position just by comparing the phases of the channels, independently of beam arrival time jitter and external reference clock phase. This paper describes the design and architecture of a new re-entrant BPM electronics, including results of beam tests at FLASH that were performed to validate the chosen design.  
Design, Characterization and laboratory tests of a Stripline BPM for the CLIC Drive Beam
  • A. Benot-Morell
    IFIC, Valencia, Spain
  • A. Benot-Morell, L. Søby
    CERN, Geneva, Switzerland
  • J.M. Nappa, J. Tassan-Viol, S. Vilalte
    IN2P3-LAPP, Annecy-le-Vieux, France
  • S.R. Smith
    SLAC, Menlo Park, California, USA
  A prototype of a strip line Beam Position Monitor (BPM) with its associated readout electronics has been developed in collaboration with SLAC, LAPP and IFIC and tested at CERN. The position resolution and accuracy parameters are expected to be below 2μm and 20μm respectively for a beam with a bunching frequency of 12GHz, and an average current of 101A. This paper will focus on the measured characteristics in the laboratory and 3D electromagnetic simulations.  
Modular Logarithmic Amplifier Beam Position Monitor Read-Out
  • B.T. Jacobson, J. Madey
    University of Hawaii, Honolulu, HI, USA
  High brightness electron beams for inverse Compton backscatter photon sources driven by thermionic microwave guns require real-time position measurements in order to achieve the spatial and temporal coincidence necessary to ensure statistically measurable signals. True logarithmic amplifiers are more adequately suited to signal comparison than are σ-delta methods. A low-cost, modular and scalable readout and data acquisition system for strip-line beam position monitors utilizing the AD640 log-amp is being developed at University of Hawai'i MkV Linear Accelerator and Free Electron Laser Lab. Initial measurements and prototyping of the hardware is complete, production and deployment underway, and commissioning scheduled for July and August. We present the methodology and results of this project.  
A Prototype Cavity Beam Position Monitor for CLIC
  • F.J. Cullinan, S.T. Boogert, A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  • A. Lunin, M. Wendt
    Fermilab, Batavia, USA
  • L. Søby
    CERN, Geneva, Switzerland
  The Compact Linear Collider (CLIC) places unprecedented demands on its diagnostics systems. A large number of cavity beam position monitors (BPMs) throughout the main linac and beam delivery system must routinely perform with 50 nm spatial resolution. Multiple position measurements within a single bunch train are also required. A prototype cavity beam position monitor (BPM) has been designed and built to be tested on the CLIC Test Facility (CTF3) probe beam. This paper presents the latest measurements of the prototype cavity BPM and the design and measurement of the radio frequency (RF) processing electronics with regards to the final performance. Installation of the BPM in the CTF3 probe beam line is also discussed.  
Octave Broadband EO-probe Laser Source for High Resolution 3D-EO Sampling
  • K. Ogawa, H. Tomizawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • S. Matsubara, Y. Okayasu
    JASRI/SPring-8, Hyogo, Japan
  We have been developing three dimensional bunch charge distribution (3D-BCD) monitor for FEL seeded with high-order harmonic (HH) pulse. 3D-BCD is based on EO-sampling technique with multiple EO crystal detectors in the manner of spectral decoding. Using this 3D-EO sampling technique, the positioning and timing of electron bunch is obtained in real-time with non-destructive measurement. For obtaining the high temporal resolution, an octave broadband probe laser with linear chirp rate of 1 fs/nm is required. We are developing an EO-probe laser pulse with ~10 μJ pulse energy and the bandwidth over 300 nm (FWHM). For meet these bandwidth and pulse energy, this EO-probe pulse is using a supercontinuum generated by photonic crystal fiber (PCF) and amplified with optical parametric amplification (OPA). Especially, for amplification with maintaining octave bandwidth, non-collinear OPA (NOPA) using BBO crystal and a pump source with a wavelength of 450 nm are adopted. The EO-probe pulse energy of 10 μJ provides for high S/N ratio to each detector and the bandwidth of 300 nm with 300 fs pulse duration allows the measurement for the 30 fs electron bunch duration (FWHM).  
Improvement of Storage Ring BPM System for SIAM Photon Source
  • S. Klinkhieo, S. Boonsuya, P. Klysubun, S. Krainara, P. Songsiriritthigul, P. Sudmuang, N. Suradet, S. Tesprasitte
    SLRI, Nakhon Ratchasima, Thailand
  This report describes the improvement of the Beam Position Monitoring (BPM) systems for the 1.2 GeV storage ring of the Siam Photon Source (SPS). The systematic studies and investigations for improving the machine performance, and storage ring BPM system has been carried out in the last few years. Some major technical problems have been found and solved. The inefficiency and unreliability of the original BPM system were also identified. They are mainly caused due to the use of low quality signal and improper installation of cables. Detailed descriptions of the replacement with the higher quality (lower loss and better interference shielding) BPM cables and implementation of a separated cable trays for the BPM cables, as well as the work on BPM electronic board calibration will be described. The measurement results before and after the improvement of the BPM system will also be presented.  
Beam Position Measurement System in the Injector of HLS II
  • J.Y. Zou, J. Fang, W.B. Li, P. Lu, T.J. Ma, B.G. Sun, Y.L. Yang, Z.R. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  Funding: Supported by the National Science Foundation of China (11175173, 11105141)
A beam position monitor(BPM) system is being installed to improve the beam position measurement of the injector at the upgrade project of Hefei Light Source (HLS II). The new BPM system is consists of 19 stripline BPMs and 19 Libera Brilliance Single Pass modules. The parameters and placement of the stripline BPMs were carefully designed. A clock distribution system was built. An EPICS-based control and display system has been developed, including a new record type to calculate the beam position by log-ratio method. The performance of the electronic system is presented based on the laboratory tests as well as real beam test at HLS linac using existing BPMs.
Measurement of X-Y Coupling at J-PARC MR
  • K. Ohmi
    KEK, Ibaraki, Japan
  • S. Hatakeyama
    JAEA/J-PARC, Tokai-mura, Japan
  In high intensity proton ring, nonlinear accelerator elements and space charge force in the presence of x-y coupling induces skew resonances. Degradation of the beam performance, beam loss enlargement, is caused by the resonances. x-y coupling has been measured in whole ring of J-PARC MR. We discuss the measurement and the effect of x-y coupling in the beam performance.  
Photon Beam Position Monitor at SIAM Photon Source
  • P. Sudmuang, S. Boonsuya, S. Chaichuay, P. Klysubun, S. Krainara, H. Nakajima, S. Rugmai, N. Sumano, N. Suradet
    SLRI, Nakhon Ratchasima, Thailand
  Photon beam position monitors (PBPM) have been designed and installed in the beamline front-ends at Siam Photon Source (SPS). Up till now, these blade-type PBPMs have been successfully installed at three bending magnet and an insertion device (planar undulator) beamlines. Its performance has been tested and compared with that of the electron beam position monitor. The achieved resolution is found to be better than 3 μm. The obtained PBPM data proved to be extremely invaluable in the investigation of the sources of the observed beam positional fluctuation, and for compensation of the orbit perturbation caused by undulator gap change. In this paper, the details of the calibration procedure will be presented. Various factors affecting reading of the signal such as back scattering effect, choice of bias voltage, and temperature variation have been investigated and the results will be discussed herewith.  
New Progress of DBPM Processor Development at SINAP
  • Y.B. Leng
    SSRF, Shanghai, People's Republic of China
  • L.W. Lai, X.U. Sun, B.P. Wang, Y.B. Yan, X. Yi
    SINAP, Shanghai, People's Republic of China
  A high speed ADC and FPGA based beam signal processing platform with modular structure has been developed to meet the various requirements of synchrotron light source and FEL facilities at SINAP. Equipped with 500MHz band-pass RF front end this instrument demonstrated very good performance in SSRF ring as a standard DBPM processor. Equipped with GHz front end this instrument can be a cavity BPM processor serving FEL facilities. New beam test results of this prototype will be presented in this paper.  
Performance and Upgrade of BPMs at the J-PARC MR
  • T. Toyama, Y. Hashimoto
    J-PARC, KEK & JAEA, Ibaraki-ken, Japan
  • K. Hanamura
    MELCO SC, Tsukuba, Japan
  • S. Hatakeyama
    JAEA/J-PARC, Tokai-mura, Japan
  • M. Okada, M. Tejima
    KEK, Ibaraki, Japan
  Since recovery from the great earthquake 2011.3.11, proton beam, more than 1014 ppp, is accelerated up to 30 GeV at the J-PARC MR. The BPMs were originally designed with the external capacitors. The aim was to improve the position response in wider frequencies and to get an adequate output voltage at the design intensity, 4x1013 ppb. It was modified, however, not to have the capacitors. Therefore we have sufficient signal intensity from low intensity beams of the initial beam commissioning, but too large from the design intensity beam. The processing circuits (BPMC) have to accommodate those output signals from high intensity beams. We are adding the attenuator-LPFs just before the BPMC. This paper will describe these additional attenuator-LPFs. In connection with the MR collimator upgrade, some BPMs are re-allocated. This process is also reported.  
The Progress in BPM Electronic System of CSNS RCS
  • W. Lu, X.L. Guan, H.Y. Sheng, X.C. Tian, Y.B. Zhao
    IHEP, Bejing, People's Republic of China
  The Beam Position Monitor (BPM) system is designed for the Rapid Cycling Synchrotron (RCS) in China Spallation Neutron Source (CSNS) to acquire beam position. This article introduces the design and implementation of the BPM electronic system. In the BPM system, signal is generated by diagonally cut electrode with dynamic range of 75dB (5.8mv~32V) and frequency range of 1MHz to 2.4MHz. Signals from the four electrodes of one test point are processed and digitalized individually, and the position is calculated using ⊿/∑ method in FPGA. It is the key point of our design to receive signal with large dynamic range while keeping low noise figure. Analog circuit with much consideration is described, and the primary test result of the system is provided in the end of this article.  
Turn-by-turn BPM System using Coaxial Switches and ARM Microcontroller at UVSOR
  • T. Toyoda
    IMS, Okazaki, Japan
  • K. Hayashi, M. Katoh
    UVSOR, Okazaki, Japan
  A major upgrade of the electron storage ring at UVSOR (Institute for Molecular Science, Japan) started from April 2012. To assist the commissioning procedure, we have developed a turn-by-turn Beam Position Monitor (BPM) system which consists of a signal switching circuit, a digital oscilloscope and software. The storage ring has 24 BPMs, each of which consists of four electrodes. By using the signal switching circuit, we can select one BPM from eight BPM's. The four signals from the BPM are sent to a digital oscilloscope and are recorded. In the switching circuit, coaxial switches of SPDT (Single Pole Dual Throw) and SP4T type are used. To control coaxial switches, we adopted 'mbed', the ARM microcontroller development kit. The 'mbed' stores the control applications configured in the HTML file and JavaScript library which can handle multiple I/O ports. It responds as a HTTP server and the control application runs on a Web browser. By clicking buttons with a mouse, we can control the I/O ports of 'mbed' through JavaScript library and accordingly can control coaxial switches. In the presentation, we will report the detail of the developed BPM system and its performance.  
Development of a microTCA Stripline BPM System for LCLS II at SLAC
  • D. Van Winkle, J.J. Olsen, C. Xu
    SLAC, Menlo Park, California, USA
  Funding: Work supported by Department of Energy Contract DE-AC02-76-SFO0515
A new stripline BPM system has been developed in the microTCA .4 (mTCA) platform for the upcoming LCLS II machine at SLAC. The new systems is based upon a mix of commercial off the shelf (COTS) digitizers and custom signal conditioning rear transitions modules (RTM). A shelf of mTCA BPMs can contain up to 8 BPMs which reduces the complexity of the cable plant and overhead required for the current 2u rack mounted chassis solution. The new system has increased sensitivity requirements as well as the potential to work with proposed multi-bunch operation of LCLS II. We will provide details of the system architecture, implementation and provide actual beam results.
Application of EMMA BPMs to the ALICE Energy Recovery Linac
  • A. Kalinin, D. Angal-Kalinin, F. Jackson, J.K. Jones
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  The ALICE Energy Recovery Linac arc button pickups have been recently equipped with EMMA BPM electronics*. These bunch-by-bunch EPICS VME BPMs give information about charge and position, and its jitter, allowing estimates of the beam energy jitter in ALICE in different modes of operation. A Mathematica program is designed to monitor statistically individual bunches (spacing 61.54ns) as well the train as a whole (up to 1625 bunches), allowing the study of jitter and position stability of the beam through the arc. The ALICE arc has been designed to be isochronous, with the bunch compression achieved through a separate dedicated bunch compressor chicane. The arc incorporates two sextupoles for correcting non-linear longitudinal matrix terms and experimental evidence suggests that the off-centred beam in the sextupoles breaks the linear isochronicity. We present some beam measurement results collected in 2012 using these BPMs.
*A. Kalinin et al, MOPPR061, IPAC12
Design and Fabrication of the Stripline BPM at ESSB
  • S. Varnasseri, I. Arredondo, D. Belver, F.J. Bermejo, J. Feuchtwanger, N. Garmendia, P.J. González, L. Muguira
    ESS Bilbao, LEIOA, Spain
  • V. Etxebarria, J. Jugo, J. Portilla
    University of the Basque Country, Faculty of Science and Technology, Bilbao, Spain
  A Stripline type BPM is designed and fabricated at ESSB. In order to compare, in the future, the functionality and response of the previous BPM capacitive pick-ups design with stripline, a design for stripline BPM is proposed. The design is based on travelling wave electrodes principles to detect the transverse position of the beam in the vacuum chamber. In the design of stripline setup, it has been considered to keep the comparison conditions with pick-ups as similar as possible. The length of strip electrodes is 200 mm and the coverage angle is 0.952 rad. The structure is rotationally pi/2 symmetric and the alignment of electrodes are pi/4, 3pi/, 5pi/4 and 7pi/4. The design is optimized for a frequency of 352 MHz, however it can function on a wide range of frequencies out coming from the measurement results. Striplines in general have well defined behavior even for low beta and low intensity beams as well as functionality at low and high frequencies. A report on the design and characteristics measurement of Stripline will be presented. The characteristics like frequency range, electrodes insulation, electrode response, sensitivities to beam power and position will be presented.  
Image Profile Diagnostics Solution for the Taiwan Photon Source
  • C.Y. Liao, Y.-S. Cheng, P.C. Chiu, K.T. Hsu, K.H. Hu, C.H. Kuo, D. Lee, C.Y. Wu
    NSRRC, Hsinchu, Taiwan
  TPS (Taiwan Photo Source), a third generation 3 GeV synchrotron light facility, featuring ultra-high photon brightness with extremely low emittance which will be a state-of-the-art synchrotron radiation facility and is being in construction at National Synchrotron Radiation Research Center (NSRRC) campus. For optimize machine operation and diagnostics applications, beam image profile and its analysis play an important role in beam diagnostics of a particle accelerator system. However, due to the CCD image collection devices are distributed around the linac, booster, and storage ring, a distributed EPICS based image profile diagnostics solution was proposed, which are based on Gigabit PoE embedded vision system with PoE camera. This solution provides an effective way to simplify wiring, and increased performance, load independence and reliability. The system is implemented and tested and the results will be summarized in this report.  
Improvement of Hardware and Software Setup for the Acquisition and Processing of SIAM Photon Source BPM Signal
  • N. Suradet, S. Boonsuya, S. Klinkhieo, P. Klysubun, S. Krainara, C.P. Preecha, P. Sudmuang
    SLRI, Nakhon Ratchasima, Thailand
  Data acquisition and processing system has been developed for the Siam Photon Source storage ring BPM system in order to improve monitoring and logging performances. BPM readout, i.e. scanning of BPM electrode voltage outputs and subsequently converting to X-Y position values, is now performed by an upgraded Programmable Logic Controller (PLC) with higher bit resolution (16-bit) digital-to-analog converter (DAC). Moving averaging is then performed on the obtained BPM data utilizing a LabVIEW code to reduce background noise during on-line measurement. All data is then stored on a dedicated computer serving as a central data logging system, which can be remotely accessed via a network communication link. In this report, details of the new setup will be presented, and comparison will be made between the performance of the new and previous setups, together with suggestions on further improvements.  
Design Status of the European X-FEL Tranverse Intra Bunch Train Feedback
  • B. Keil, R. Baldinger, C.D. Beard, M.M. Dehler, W. Koprek, G. Marinkovic, M. Roggli, M. Rohrer, M. Stadler, D.M. Treyer
    PSI, Villigen, Switzerland
  • V. Balandin, W. Decking, N. Golubeva
    DESY, Hamburg, Germany
  Funding: Work supported by Swiss State Secretariat for Education and Research SER
The European X-Ray Free Electron Laser (E-XFEL) will have a fast transverse intra-bunch train feedback (IBFB) system to stabilize the beam position in the SASE undulators. E-XFEL bunch trains consist of up to 2700 bunches with a minimum bunch spacing of 222ns and typ. 10Hz train repetition rate. The IBFB will measure the positions of each bunch in the bunch train, and apply intra-train feedback corrections with fast kickers, in addition to a feed-forward correction for reproducible trajectory perturbations. By achieving a feedback loop latency in the order of one microsecond, the IBFB will allow the beam position to converge quickly to the nominal orbit as required for stable SASE operation. The latest conceptual design of the IBFB and the status of IBFB components will be presented.
Development of Bunch Current and Oscillation Recorder for SuperKEKB Accelerator
  • M. Tobiyama, J.W. Flanagan
    KEK, Ibaraki, Japan
  A High-speed digital signal memory has been developed for the bunch current and oscillation recorder for SuperKEKB. The memory consists of an 8-bit ADC and a FPGA daughter card with Spartan6 and DDR2 memories commercially available on a double width VME card. The block-RAM on the FPGA is used to transfer bunch current data with low latency for prompt bunch current measurements, and the large DDR2 memory is used for long-duration position recording, such as post-mortem bunch oscillation recording. The performance of the board, including data transfer rate, will be presented.  
Reliable Beam-Intensity Control Technique at the HIMAC Synchrotron
  • K. Mizushima, T. Furukawa, Y. Hara, Y. Iwata, K. Katagiri, K. Noda, S. Sato, T. Shirai
    NIRS, Chiba-shi, Japan
  The carbon-ion beam is slowly extracted from the Heavy Ion Medical Accelerator in Chiba (HIMAC) synchrotron using the third-order resonance with the RF-knockout method for scanned carbon-ion therapy. However, an overshoot of the beam spill at the start of extraction is often induced by a slight variation of the beam emittance in operation cycles. It brings dose hot spot inside the target volume, because the tolerable beam-intensity in scanning irradiation is low. We have added short extraction, called preliminary extraction, before irradiation in order to remove the uncontrollable spilled particles. During preliminary extraction, it is necessary to prevent the beam delivering to the patient. Therefore, a fast beam shutter on which an ionization chamber is mounted was developed, and it was installed in the extraction line. The fast shutter enables us to switch from preliminary extraction to irradiation within 100 ms, and the reliability of the beam-intensity control system was drastically improved by the preliminary extraction technique.  
Development of the System for Longitudinal Coupled Bunch Modes Measurement at Indus-2
  • S. Yadav, A.C. Holikatti, C.P. Navathe, A. Ojha, T.A. Puntambekar, Y. Tyagi
    RRCAT, Indore (M.P.), India
  In a circular accelerator, beam instabilities are intensity-dependent collective effects that arise because of the electromagnetic wake fields generated by the beam as it interacts with its environment. These instabilities limit the high current operation in the accelerator and degrade the performance of synchrotron radiation beam. Indus-2 is a synchrotron radiation source at RRCAT, Indore having design beam current of 300 mA and 2.5 GeV beam energy. Beam intensity signal obtained from wall current monitor (WCM) is used to measure the longitudinal coupled bunch modes (CBM). To study the beam instabilities, an automated software has been developed which acquires the beam intensity spectrum for measurement of coupled bunch modes. The software has option of complete CBM scan, scanning near the significant RF cavity higher order modes (HOM) and scanning of user-selected modes. The scanning time for complete 291 modes is ~5 minutes. In this paper, we describe the measurement system, features of the developed software and some measurement results on Indus-2 machine.  
Introduction of Photon BPMs in SOLEIL Global Orbit Feedback Systems
  • N. Hubert, L. Cassinari, J.-C. Denard, L.S. Nadolski
    SOLEIL, Gif-sur-Yvette, France
  SOLEIL global orbit feedback systems (slow and fast), based on 122 Electron Beam Position Monitor (eBPM) readings, are in operation since 2008 and give very satisfying performances (0.1Hz-500Hz vertical noise < 300 nm, long term (8h) drifts < 1μm RMS). Nevertheless, in SOLEIL layout, magnetic elements (quadrupoles and sextupoles) are located between dipoles and their closest eBPMs. For that reason, Photon Beam Position Monitors (XBPMs) in the dipole beamline frontend give additional information that is useful to stabilize better the source point in the dipole. XBPMs provide also a better angular measurement resolution as they are located at 4 meters from the source point. Results presented in this papers show that vertical stability on bending magnet beamlines can be improved by including their XBPM measurements in global orbit feedback systems. In a first time XBPMs have been introduced in the Slow Orbit Feedback system (SOFB) that corrects the orbit with a repetition rate of 0.1Hz. In a second time XBPMs will be introduced in the Fast Orbit Feedback system (FOFB) running at a repetition rate of 10 kHz.  
High Frequency Response of Accelerator Vacuum Chambers and Implications for Orbit Feedback Systems
  • B. Podobedov
    BNL, Upton, Long Island, New York, USA
  Understanding the response of conducting accelerator vacuum chambers to external AC magnetic field is important for many accelerator applications, where the particle beam is dynamically driven with magnets external to the chamber. For instance, efficient orbit feedback system design requires detailed knowledge of the chamber transfer function at the locations of corrector magnets, which in general depends on the chamber material, cross-sectional shape and thickness. In practically interesting cases, the chamber response is influenced by both eddy currents and the skin effect, which are often accounted for rather crudely when modeling the system. This paper presents new analytical results for transfer functions through arbitrary shaped vacuum chambers; compares them with the measurements for the present NSLS rings and discusses the implications for the future NSLS-II orbit feedback systems.  
Measurements of Martin-Puplett Interferometer Limitations using Blackbody Source
  • P. Evtushenko, J.M. Klopf
    JLAB, Newport News, Virginia, USA
  Frequency domain measurements with Martin-Puplett interferometer is one of a few techniques capable of bunch length measurements at the level of ~ 100 fs. As the bunch length becomes shorter, it is important to know and be able to measure the limitations of the instrument in terms of shortest measurable bunch length. In this paper we describe experiment of using blackbody source with the modified Matrin-Puplett interferometer that is routinely used for bunch length measurements at the JLab FEL, as a way to estimate the shortest, measurable with the device, bunch. The limitation comes from high frequency cut-off of the presently used wire-grid polarizer and is estimated to be 50 fs RMS. The measurements are made with the same Golay cell detector that is used for beam measurements. We demonstrate that, even though the blackbody source is many orders of magnitude less bright than the coherent transition or synchrotron radiation, it can be used for the measurements and gives a very good signal to noise ratio in a combination with lock-in detection. We also compare the measurements made in air and in vacuum to show the very strong effect of the atmospheric absorption.  
RF Front-end for High Bandwidth Bunch Arrival-time Monitors in Free-Electron Lasers at DESY
  • A. Penirschke, A. Angelovski, M. Hansli, R. Jakoby
    TU Darmstadt, Darmstadt, Germany
  • M.K. Bock, M. Bousonville, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • A. Kuhl
    Uni HH, Hamburg, Germany
  • S. Schnepp
    IFH, Zurich, Switzerland
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors"
The Free-Electron Laser in Hamburg FLASH is equipped with Bunch Arrival-time Monitors (BAMs) that use an electro-optical detection scheme to modulate the intensity of the femtosecond laser pulse train with the pickup signals (*). The achieved resolution of the existing BAMs are less than 10 fs for bunch charges higher than 500 pC. For lower bunch charges the time resolution drops significantly. Increased demands for low bunch charge operation modes of 20 pC and less at FLASH II and the European X-ray Free-Electron Laser XFEL require an upgrade of the existing beam diagnostic equipment. High bandwidth BAMs with newly developed cone-shaped pickups (**) promise sub-10 fs time resolution for both, the high and low bunch charge operation mode. This paper addresses the RF signal path of the high bandwidth BAMs for FLASH II and XFEL. It comprises radiation resistant coaxial cables, combiners and limiters up to a frequency of 40 GHz from the pickup electrodes to the Electro-optical Mach-Zehnder type modulator (EOM). Detailed investigations of the signal path using measurements and simulations with AWR Microwave Office allows for a good prediction of the signal quality and shape at the EOM.
(*) F. Löhl et al., Phys. Rev. Lett. 104,144801 (2010)
(**) A. Angelovski et al. in Proceedings of the International Particle Accelerator Conference (IPAC2011), San Sebastian, Spain, 2011, p.1177
Coherent Optical Transition Radiation at the SwissFEL Injector Test Facility
  • B. Smit, M. Aiba, S. Bettoni, B. Beutner, R. Ischebeck, G.L. Orlandi, E. Prat, L. Rivkin, T. Schietinger, V. Schlott
    PSI, Villigen, Switzerland
  SwissFEL uses magnetic dispersive sections for bunch compression, which may cause micro-bunching within the electron bunch. Studies of Coherent Optical Transition Radiation (COTR) allow us to see whether or not such bunching is present. We present pilot results of COTR experiments carried out at the SwissFEL Injector Test Facility. Optical transition radiation is generated at an aluminium-coated silicon wafer that can be inserted into the beam. This can either be imaged to a CCD camera, or focused into a spectrometer with a spectral range from 200 nm to 925 nm. The compression of the electron bunches was varied, and data was recorded at different bunch lengths. Spectral data shows a clear gain of the signal and a shift towards the infrared for a stronger compression of the bunches. Results indicate that the spectrum fluctuates at maximum compression. This is consistent with fluctuations observed in COTR images.  
Study of Beam Length Measurement based on TM010 Mode
  • R.X. Yuan, Y.B. Leng, L.Y. Yu, W.M. Zhou
    SINAP, Shanghai, People's Republic of China
  Beam length measurement in frequency domain is a familiar method, and the resolution is seriously limited by the system signal-noise-ratio (SNR) and the beam length measured. Usually this method can only obtain the resolution about ~10ps with beam length ~30ps when using signal from button or stripline BPM. But in FEL case, the beam length is the ps or sub-ps order. The paper discusses the probability of beam length measurement based on the TM010 mode in FEL case. When adopting High Order Mode(HOM) reject and system gain control, the system SNR can arrive at 110dB and the resolution can achieve 30fs with beam length ps or sub-ps.  
Realization and Measurements of Cone-shaped Pickups for Bunch Arrival-time Monitors for FLASH and XFEL
  • A. Angelovski, M. Hansli, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • M.K. Bock, M. Bousonville, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  • A. Kuhl
    Uni HH, Hamburg, Germany
  • S. Schnepp
    IFH, Zurich, Switzerland
  • T. Weiland
    TEMF, TU Darmstadt, Darmstadt, Germany
  Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors"
At the Free Electron Laser FLASH at DESY, the installed Bunch Arrival-time Monitors (BAMs) use an electro-optical detection scheme for arrival-time measurements. The achieved time resolution is in the sub-10 fs range for bunch charges higher than 500 pC. The extension of FLASH II and the European X-ray Free Electron Laser Project (XFEL) foresees a low charge operation mode with bunch charge of 20 pC or less. The time resolution of the BAMs significantly drops as the bunch charge reduces (*). By expanding the bandwidth of the pickups one can increase the time resolution at low charges. In this paper, we present the characterization results of the manufactured cone-shaped pickups introduced in (**) with a bandwidth up to 40 GHz. The pickups mounted in a vacuum body exhibit four-fold rotational symmetry with respect to the beam pipe. Due to different beam pipe apertures for FLASH and XFEL, two bodies are manufactured. The rf properties of the mounted pickups in case of open and sealed body as well as the pickups separately are measured and compared to the simulation results obtained by CST STUDIO SUITE®.
(*)M. K. Bock et al. in Proceedings of DIPAC 2011, Hamburg, Germany, 2011, p.365
(**)A. Angelovski et al. in Proceedings of IPAC 2011, San Sebastian, Spain, 2011, p.1177
Planar Transmission Line BPM for Magnetic Bunch Compressor Chicane for XFEL
  • A. Angelovski, R. Jakoby, A. Penirschke
    TU Darmstadt, Darmstadt, Germany
  • C. Gerth, U. Mavrič, H. Schlarb, C. Sydlo
    DESY, Hamburg, Germany
  In order to obtain ultra-short bunches in the Free Electron Laser FLASH at DESY, the electron beam is compressed in magnetic chicanes. Precise knowledge of the beam position in the chicane is of great significance for the longitudinal dynamics control. In the current implementation cylindrical pickup-striplines mounted perpendicularly to the beam are used as a Beam Position Monitor (BPM)(*). One can determine the horizontal beam position by measuring the phase difference of the beam induced signal at opposite ends of a pickup. Due to the different electrical and mechanical requirements for the European XFEL a new BPM has to be developed. In this paper, we present the design and analysis of a planar transmission line structure which is planned to be used as a BPM in the European XFEL. The planar design of the pickups can provide for proper impedance match to the subsequent electronics as well as sufficient mechanical stability along the aperture when using alumina substrates. A scaled non-hermetic prototype of the BPM is built and characterized by scattering parameters. The measurement results are compared to simulations obtained by CST STUDIO SUITE®.
(*) K. Hacker at el, Proceedings of DIPAC 2007, Venice, Italy 2007, p.108
Measurement of Temporal Resolution and Detection Efficiency of X-ray Streak Camera by Single Photon Images
  • A. Mochihashi, M. Masaki, H. Ohkuma, S. Takano, K. Tamura
    JASRI/SPring-8, Hyogo-ken, Japan
  Funding: This work was partly supported by MEXT Grant-in-Aid for Young Scientists (B) Grant number 21740215.
In the third generation and the next generation synchrotron radiation light sources, the electron beam bunch length of ps ~ sub-ps is expected to be achieved. An X-ray streak camera (X-SC) can directly measure the temporal width of X-ray synchrotron radiation pulse. The temporal resolution of X-SC depends on the initial velocity distribution of the photoelectrons from a photocathode which converts the X-ray photons to the photoelectrons. To measure the temporal resolution of the X-SC, we have observed 'single photon' streak camera images and measured the temporal spread of the images. By this 'single photon' experiment, we have evaluated the dependence of the temporal resolution and the detection efficiency on the photon energy. We have also tried to evaluate the dependence of the temporal resolution and the detection efficiency on the thickness of the photocathode. For this purpose, we have developed a multi-array type CsI photocathode with 3 different thickness of the photocathode. The experimental setups, and the results of the measurements of the temporal spread and the detection efficiency of the single photon events will be presented.
EO-sampling-based Temporal Overlap Control System for a Seeded FEL
  • S. Matsubara
    RIKEN/SPring-8, Hyogo, Japan
  • M. Aoyama
    JAEA/Kansai, Kyoto, Japan
  • A. Iwasaki, S. Owada
    The University of Tokyo, Tokyo, Japan
  • K. Ogawa, T. Sato, H. Tomizawa
    RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
  • Y. Okayasu, T. Togashi, T. Watanabe
    JASRI/SPring-8, Hyogo-ken, Japan
  FELs have greatly interested for the short-wavelength region. However, their temporal profile and frequency spectra have shot-to-shot fluctuation by a SASE process. One of the promising approached for the problems is a seeded FEL scheme by using a full-coherent light source. The seeded FEL has been demonstrated in the EUV region by employ the high-order harmonics (HH) generation from an external laser source at the SCSS test-accelerator in the SPring-8. It is important for the HH-seeded FEL scheme to synchronize and overlap between the seeding laser pulse and the electron bunch. Their timing difference and laser spatial pointing is drifting. Therefore, a timing feedback and non-destructive monitor are necessary to operate seeded FEL continuously. We have constructed the timing monitor based on Electro-Optic (EO) sampling which is measure the timing difference the seeded laser pulse and the electron bunch simultaneously with the seeded FEL process. The probe laser pulse for the EO-sampling system is optically split from the common external HH laser driver for the seeded FEL. The EO-sampling system is able to use timing feedback for continual operation of the HH-seededFEL.