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monitoring

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IT05 Single Shot Electron-Beam Bunch Length Measurements diagnostics, instrumentation, electro-magnetic fields, electron, wakefield 20
 
  • G. Berden, G.M.H. Knippels, D. Oepts, A.F.G. van der Meer
    FOM, Institute for Plasma Physics 'Rijnhuizen', Nieuwegein, The Netherlands
  • S.P. Jamison, X. Yan, A.M. MacLeod, W.A. Gillespie
    Abertay, University of Abertay Dundee, Dundee, UK
  • J.L. Shen
    CNU, Capital Normal University, Beijing, China
  • I. Wilke
    RPI, Rensselaer Polytechnic Institute, Troy, NY, USA
  It is recognised by the Instrumentation community that 4th generation light sources (like TESLA, LCLS) are posing some of the most stringent requirements on beam diagnostics. Among these, the single-shot electro-optic measurement of the bunch length and shape in the sub-picosecond domain is an ongoing development. The electro-optic detection method makes use of the fact that the local electric field of a highly relativistic electron bunch moving in a straight line is almost entirely concentrated perpendicular to its direction of motion. This electric field makes an electro-optic crystal placed in the vicinity of the beam birefringent. The amount of birefringence depends on the electric field and is probed by monitoring the change of polarization of the wavelength components of a chirped, synchronized Ti:sapphire laser pulse. This talk will provide details of the experimental setup at the Free Electron Laser for Infrared eXperiments (FELIX) in Nieuwegein, The Netherlands, where single shot images have been obtained of 1.7 ps long electron bunches (beam energy 46 MeV, charge per bunch 200 pC). Furthermore, future upgrading possibilities will be discussed.  
 
IT09 Smith-Purcell Radiation in View of Particle Beam Diagnostics diagnostics, instrumentation, radiation 40
 
  • G. Kube
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • H. Backe, W. Lauth, H. Schöpe
    IKP, Institut für Kernphysik, Mainz, Germany
  The development of the next generation high quality electron beams which are necessary for future high luminosity linear colliders and short wavelengths free electron lasers requires sensitive and non-destructive beam diagnostic techniques. In this context Smith-Purcell radiation which is generated when a charged particle beam passes close to the surface of a periodic structure (diffraction grating) is under discussion as a compact and inexpensive beam profile monitor. In order to study the basic emission process of Smith-Purcell radiation also in view of possible applications for particle beam diagnostics, experimental studies were performed at the Mainz Microtron MAMI in the visible spectral region with a microfocused 855 MeV electron beam. The radiation was separated from background components, as diffracted synchrotron radiation and transition radiation generated by electrons scratching the grating surface, by exploiting their specific emission characteristics. These are
  1. the narrow emission cone in the direction perpendicular to the grating surface,
  2. the dispersion relation |n| λ = D (1 / β - cos θ) with n the diffraction order, β the reduced electron velocity, and θ the angle of observation, and
  3. the charcteristic intensity scaling as a function of the distance between beam axis and grating surface.
Based on the experimental results the use of Smith-Purcell radiation as a longitudinal and transversal beam profile monitor will be discussed. 		 
 
CT09 SLIM (SEM for Low Interception Monitoring) - An Innovative Non-Destructive Beam Monitor for the Extraction Lines of a Hadrontherapy Centre medical accelerators, hadron, diagnostics, instrumentation, electrostatic devices 77
 
  • L. Badano, O. Ferrando, M. Pezzetta
    TERA, Fondazione TERA, Università delgi Studi Milano, Milano, Italy
  • G. Molinari
    CERN, Geneva, Switzerland
  Real time monitoring of hadrontherapy beam intensity and profile is a critical issue for the optimisation of the dose delivery to the patient carcinogenic tissue, the patient safety and the operation of the accelerator complex. For this purpose an innovative beam monitor, based on the secondary emission of electrons by a nonperturbative, sub-micron thick Al target placed directly in the extracted beam path, is being proposed. The secondary electrons, accelerated by an electrostatics focusing system, are detected by a monolithic silicon position sensitive sensor, which provides the beam intensity and its position with a precision of 1 mm at 10 kHz frame rate. The conceptual design and the engineering study optimised for hadrontherapy, together with the results of the preliminary tests of the first system prototype, will be presented.  
 
PM11 Beam Studies Made With The SPS Ionization Profile Monitor diagnostics, emittance, instrumentation, SPS 116
 
  • C. Fischer, G. Ferioli, J. Koopman, F. Roncarolo
    CERN, Geneva, Switzerland
  During the last two years of SPS operation, investigations were pursued on the ability of the SPS ionization profile monitor prototype to fulfill different tasks. It is now established that the instrument can be used for injection matching tuning, by turn to turn recording of the beam size after the injection. Other applications concern beam size measurements on beams ranging from an individual bunch to a nominal SPS batch foreseen for injection into the LHC (288 bunches). By continuously tracking throughout the SPS acceleration cycle from 26 GeV to 450 GeV the evolution of parameters associated to the beam size, it is possible to explain certain beam behavior. Comparisons are also made at different beam currents and monitor gains with measurements made with the wire scanners. Data are presented and discussed, and the possible implementation of new features is suggested in order to further improve the consistency of the measurements.  
 
PM21 Recent Developments Of The EXCYT Radioactive Beam Diagnostics diagnostics, ion, ion-source, isotope-production 143
 
  • L. Cosentino, P. Finocchiaro
    INFN-LNS, Laboratori Nazionali del Sud, Catania, Italy
  The EXCYT radioactive beam facility at LNS, based on the ISOL (Isotope Separator On Line) technique, will start producing its first radioactive beams during 2004. We are setting up a suitable high sensitivity diagnostics, in order to guarantee a real time monitoring of the beam parameters (transversal profiles, ion composition and current), offering also the capability to perform the beam imaging at very low beam energy (50 keV). For this purpose, a simple technique based on the use of a thin CsI(Tl) scintillating plate that does not require any amplification system inside the beam pipe, has been employed. Tests performed with stable beams have shown a current sensitivity well below 105 pps, a value that can be improved by adopting a more suitable lens and an intensified and cooled CCD camera.  
 
PM29 A Modular VME Data Acquisition System for Counter Applications at the GSI Synchrotron controls 164
 
  • D.A. Liakin
    ITEP, Institute for Theoretical and Experimental Physics, Moscow, Russia
  • T. Hoffmann, P. Forck
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  Particle counters perform the control of beam loss and slowly extracted currents at the heavy ion synchrotron (SIS) at GSI. A new VME/Lynx - PC/Linux based data acquisition system has been developed to combine the operating purposes beam loss measurement, spill analysis, spill structure measurement and matrix switching functionality in one single assembly. In this paper a detailed PC-side software description is presented. To achieve best system stability, the software has been divided into time critical networking and data deploying threads and low or normal priority interface tasks. Some new abilities in the fields of data computation and presentation are reported. A hardware description is presented, in detail a programmable GSI-EVENT controller, which is based on an ordinary 8 bit RISC microprocessor and which has been integrated into the system, to synchronize the data acquisition with the sophisticated “virtual accelerator” timing at GSI. First experiences gained while the commissioning of the system are discussed.  
 
PT02 Pill-Box Cavity BPM For TESLA Cryomodul diagnostics, linac, position, resonance, single bunch 172
 
  • V. Sargsyan
    TU-Berlin, Technische Universität, Berlin, Germany
  A new cavity BPM with 10 μm resolution is designed and fabricated to perform single bunch measurements at the TESLA linear collider. In order to have a low energy dissipation in the cryogenic supermodule, the inner surface of the cavity is copper plated. Cross-talk is minimised by a special polarisation design. The electronics, at 1.5 GHz, is a homodyne receiver normalised to the bunch charge. Its LO-signal for down-conversion is taken from the same cavity.  
 
PT06 Dynamic X-Y Crosstalk / Aliasing Errors of Multiplexing BPMs instrumentation, diagnostics, pick-up, operational-performance, controls, feedback 181
 
  • T. Straumann
    SLAC, Stanford Linear Accelerator, Stanford, CA, USA
  Multiplexing Beam Position Monitors (BPM) are widely used for their simplicity and inherent drift cancellation property. These systems successively feed the signals of (typically four RF) pickups through one single detector channel. The beam position is calculated from the demultiplexed (base band) signal. However, as shown by this contribution, transverse beam motion results in positional aliasing errors due to the finite multiplexing frequency. Fast horizontal motion, for example, can alias into an apparent, slow vertical position change. A thorough analysis is presented and the impact of essential parameters such as the multiplexing rate and the scanning pattern/sequence of classical 4-button pickups is discussed.  
 
PT07 Cavity Beam Position Monitor For The TESLA Energy Spectrometer diagnostics, electro-magnetic fields, linear-collider, radio-frequency, TESLA 184
 
  • A. Liapine
    TU-Berlin, Technische Universität, Berlin, Germany
  In order to measure the beam position with a precision of better than 1μm in the TESLA energy spectrometer a cavity beam position monitor is proposed. The waveguide coupling is used to achieve a good common mode rejection and therefore a better precision. The paper gives a short overview of the monitor functionality and describes resolution measurements which were made on the cavity prototype.  
 
PT15 Performance of the ELBE BPM Electronics diagnostics, instrumentation, linac, pick-up, ELBE 202
 
  • P. Evtushenko, R. Schurig
    FZR, Forschungszentrum Rossendorf, Dresden, Germany
  The ELBE radiation source is based on a superconducting linac. Initially it was designed to be used in CW mode with repetition rates either 13 MHz either 260 MHz. Later it was decided to operate the accelerator with reduced repetition rates for diagnostic reasons and for certain users. Now it is possible to operate at repetition rate 13/n MHz, where n can be 2, 4, 8, 16, 32, 64, and 128. It is required that the BPM system supports any of these operation modes. A core element of the BPM electronics is a logarithmic amplifier AD8313 made by Analog Devices Inc. The logarithmic amplifier is a direct RF to DC converter rated up to 2.5 GHz. Initial design of the BPM electronic was sophisticated only for CW operation with repetition rate more than 10 MHz, since bandwidth of the AD8313 is about of 10 MHz. Additionally a sample and hold amplifier is built in to provide enough time for an ADC to make measurements. The sample and hold amplifier is synchronized with a micropulse frequency. In the paper we present results of the modified BPM electronics test.  
 
PT26 Cryogenic Current Comparator for Absolute Measurement of the Dark Current of the Superconducting Cavities for Tesla cryogenics, diagnostics, pick-up, shielding, superconductivity, TESLA 234
 
  • K. Knaack, M. Wendt, K. Wittenburg
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • R. Neubert, S. Nietzsche, W. Vodel
    FSU Jena, Friedrich-Schiller Universität, Jena, Germany
  • A. Peters
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  A newly high performance SQUID based measurement system for detecting dark currents, generated by superconducting cavities for TESLA is proposed. It makes use of the Cryogenic Current Comparator principle and senses dark currents in the nA range with a small signal bandwidth of 70 kHz. To reach the maximum possible energy in the TESLA project is a strong motivation to push the gradients of the superconducting cavities closer to the physical limit of 50 MV/m. The field emission of electrons (the so called dark current) of the superconducting cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. This contribution describes a Cryogenic Current Comparator (CCC) as an excellent and useful tool for this purpose. The most important component of the CCC is a high performance DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the extracted dark current. For this reason the SQUID input coil is connected across a special designed pick-up coil for the electron beam. Both the SQUID input coil and the pick-up coil form a closed superconducting loop so that the CCC is able to detect dc currents down to 2 pA/√Hz. Design issues and the application for the CHECHIA cavity test stand at DESY as well as preliminary experimental results are discussed.