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radiation

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MOO1A03 Review of Synchrotron Radiation based Diagnostics for Transverse Profile Measurements emittance, optics, synchrotron, diagnostics 6
 
  • G. Kube
    DESY, Hamburg
  The transverse particle beam emittance is a crucial accelerator parameter because it is directly related to the brilliance of a synchrotron light source or the luminosity of a particle beam collider. Therefore a precise online control of the beam profile is highly desirable from which the corresponding emittance can be calculated. In addition observation of the particle beam shape's time-like evolution allows to study effects as for example injection mismatch and dynamical beta beating which are important for smooth-running accelerator operation. Due to its non-destructive nature synchrotron radiation is a versatile tool for beam profile measurements and is used in nearly every accelerator. While in principle synchrotron radiation from insertion devices or bending magnets can be utilized, in reality most accelerators use bending magnet radiation based profile monitoring because of space limitations. There exist a number of different techniques in order to overcome limitations due to resolution broadening effects which can result in theoretical resolutions down to the sub-micron level. In this talk an overview over the methods presently applied in most accelerators will be given.  
 
MOD1A03 Electron Beam Diagnostics for the ALBA Light Source booster, diagnostics, linac, synchrotron 27
 
  • U. Iriso, A. Olmos, F. Peréz
    ALBA, Bellaterra
  This paper presents the diagnostics systems that will be used to monitor the electron beam at ALBA, a 3 GeV 3rd generation synchrotron light source. The electron beam is characterized by measuring its transverse position in the beam pipe, beam current, transverse size and longitudinal structure. We provide a complete picture of all the systems to diagnose the electron beam along ALBA facility, not only in the Storage Ring but also in the injector system (Linac, Booster and transfer lines).  
 
MOO3A01 Optical Transition Radiation Monitor for High Intensity Proton Beam at the J-PARC background, target, proton, beam-losses 30
 
  • A. Toyoda, A. Agari, E. Hirose, M. Ieiri, Y. Katoh, M. Minakawa, H. Noumi, Y. Sato, Y. Suzuki, H. Takahashi, M. Takasaki, K. H. Tanaka, H. Watanabe, Y. Yamanoi
    KEK, Tsukuba
  The OTR is a powerful tool to observe 2-dimensional information of beam profile at the high intensity beamline because the OTR intensity only depends on the screen reflectivity so that we can minimize a beam loss. However, it is necessary to overcome large background due to the Cerenkov radiation and low radiation tolerance of camera system. The purpose of the present effort is to achieve small background and good S/N and to prolong the lives of the camera system. This requires that amount of potential Cerenkov radiator be minimized and radiation level at the camera system be suppressed. For this requirement, we design and develop an OTR monitor with the optical system of a Newtonian telescope type. Detail design of the optical system and a result of background measurement performed at one of primary proton beam lines of our old 12 GeV Proton Synchrotron will be presented.  
 
MOO3A03 First Vibrating Wire Monitor Measurements of a Hard X-ray Undulator Beam at the Advanced Photon Source photon, resonance, vacuum, insertion 36
 
  • G. Decker
    ANL, Argonne, Illinois
  • S. G. Arutunian, M. R. Mailian
    YerPhI, Yerevan
  • G. Rosenbaum
    UGA, Athens, Georgia
  The first hard x-ray flux measurements with a vibrating wire monitor (VWM) using the acoustic resonance frequencies of two vertically-offset horizontal stainless steel wires as temperature diagnostics were conducted at APS beamline 19-ID. Due to the high sensitivity of this technique, the studies were performed at extremely low power levels using radiation from a 3.3-cm-period permanent magnet hybrid undulator with a 5-mA electron beam at an energy of 7 GeV. The x-ray beam was filtered by transmission through 7 mm of beryllium placed in the photon beam path, assuring that only hard x-rays were detected. The particle beam was scanned through a range of 400 microradians using an asymmetric closed-orbit angle bump, producing two vertical photon beam profiles. The difference between processed wire signals provides a very sensitive measure of photon beam position. Details of the measurements will be given, along with a discussion of the limitations of the method and possible future research directions.  
slides icon Slides  
 
TUPB25 Beam Profile Measurement with Optical Fiber Sensors at FLASH undulator, beam-losses, controls, monitoring 123
 
  • W. Goettmann, F. Wulf
    HMI, Berlin
  • M. Körfer
    DESY, Hamburg
  The measurement setup is based on wire scanners, optical fibers mounted symmetrically around the beam line over the full length (30 m) of the undulator section, a signal conditioning unit and a data acquisition system. The fiber sensors along the beam line allow the measurement of the spatial distribution of the scattered beam caused by the wire scanner. At each increment of the wire scanner, the generated Cherenkov light in the fiber sensors - which is proportional to the intensity of the scattered electron shower - is measured. As an improvement, the shower is not only measured at a singular location but over the entire length of the undulator section. Each integral of the generated Cherenkov light along the beam line gives one point of the transversal beam profile. Accomplishing an x-y-scan leads to a two dimensional profile of the beam. The synchronisation with the beam trigger allows the characterization of each bunch. The measured data are visualized in real time and stored in a log file for extended evaluation. The high sensitivity of the system allows an accurate monitoring of the beam profile as well as HALO measurement.  
 
TUPB28 A Large Scintillating Screen for the LHC Dump Line proton, kicker, photon, controls 132
 
  • T. Lefèvre, C. B. Bal, E. Bravin, S. Burger, B. Goddard, S. C. Hutchins, T. Renaglia
    CERN, Geneva
  7 TeV proton beam from the LHC is ejected through a long transfer line to a beam dump block. Approximately 100 m downstream of the ejection septa, a series of dilution kicker magnets provide a sweeping deflection spreading the extracted beam over a 40 cm diameter area on the face of the beam dump core. During normal operation, the quality of each dump event must be recorded and verified. The so called “Post-Mortem” data-set will include information from the beam dumping system as well as from the beam diagnostics along the extraction line. For this purpose, a profile monitor in front of the dump block is permanently available during machine operation. With more than 1014 protons stored in LHC, the thermal properties of the screen have to be considered as beam energy deposition becomes an issue. This paper presents the design of this device, which is original due to its very large size. We introduce the different technical considerations involved in the design of the system and present the complete layout of its installation with a special emphasis on the mechanical design, the screen assembly and the choice of the radiation-hard video camera used to capture the image.  
 
TUPB30 Applications of IEEE-1394 and GigE Vision Digital Camera in the TLS controls, diagnostics, emittance, synchrotron 138
 
  • C. H. Kuo, J. Chen, P. C. Chiu, K. T. Hsu, S. Y. Hsu, D. Lee, C. Y. Wu
    NSRRC, Hsinchu
  Digital cameras comply with IEEE-1394 and GigE Vision standard are applied for beam diagnostic applications at NSRRC. These cameras provide low distortion for image transmission over long distance and flexible camera parameters adjustment with remote interface. These digital interfaces include of FireWire and gigabit Ethernet. The wide bandwidth bus can reduce latency time and timing jitter effectively and provides high quality image transportation. It also provides lossless compressed image with high update rate. Experiences accompany with both kind of cameras will be summarized. System integration with control system, analysis and application will also include in the report.  
 
TUPB31 The Beam Position System of the CERN Neutrino to Gran Sasso Proton Beam Line pick-up, target, controls, proton 141
 
  • T. Bogey, O. R. Jones
    CERN, Geneva
  The CERN Neutrino to Gran Sasso (CNGS) experiment uses 400GeV protons extracted from the SPS, which travel along 825 meters of beam line before reaching the CNGS target. This beam line is equipped with 23 BPMs capable of measuring both the horizontal and vertical position of the beam. The final BPM is linked to the target station and due to radiation constraints has been designed to work in air. This contribution will give an overview of the BPMs used in the tansfer line. It will also provide a detailed explanation of their logarithmic amplifier based acquisition electronics, which consists of an auto-triggered sequencer controlling an integrator, the A/D conversion and the Manchester encoded transmission of the digital data to the surface. At the surface the digital data is aquired using the Digital Acquisition Board (DAB) developed by TRIUMF (Canada) for the LHC BPM system. Results from both laboratory measurements and beam measurements during the 2006 CNGS run will also be presented.  
 
TUPC06 Coherent Radiation Studies For The FERMI@Elettra Relative Bunch Length Diagnostics dipole, diagnostics, electron, synchrotron 156
 
  • M. Veronese, S. Di Mitri, M. Ferianis
    ELETTRA, Basovizza, Trieste
  Bunch compressors are key components of the seeded FEL FERMI@elettra. Assuring their stable operation requires multiple non-destructive diagnostics to provide error signals to the feedback systems. Both the energy and the peak current of the electron bunch have to be stabilized by the feedback systems. The peak current stabilization implies charge and bunch length stabilization. The latter will be achieved by a redundant diagnostics based on Coherent Synchrotron Radiation (CSR) and Coherent Diffraction Radiation (CDR). In this paper we describe a study of Coherent Radiation emission downstream bunch compressors as the source of a relative bunch length measurement diagnostics. The study evaluates the most critical parameters in the design of such a diagnostic using numerical integration to calculate the spectral angular properties of the radiation for both CSR and CDR.  
 
TUPC12 FPGA based Frame Grabber for Video Beam Diagnostics controls, diagnostics, injection, proton 174
 
  • I. Krouptchenkov, K. Wittenburg
    DESY, Hamburg
  TV-based accelerator diagnostics are widely used for machine operation and beam diagnostics. It is planned to renew the video memory modules of the TV monitor data acquisition systems for the injection and transfer lines at DESY. New FPGA based Frame Grabber (FG) modules were developed within this project. The modules are required to be able to work with different analog signal formats, to capture video frames on trigger and to provide live mode operation. The main feature of this FG is the possibility of reprogramming. This allows us to optimize its functionality, for example to operate with non-standard or corrupted video signals. This has proved especially useful for grabbing images from CCD-cameras suffering from radiation damage.  
 
TUPC16 Ultimate Resolution of Soleil X-Ray Pinhole Camera photon, coupling, synchrotron, synchrotron-radiation 180
 
  • M.-A. Tordeux, L. Cassinari, O. V. Chubar, J.-C. Denard, D. Pédeau, B. Pottin
    SOLEIL, Gif-sur-Yvette
  During the commissioning of the SOLEIL Storage Ring, beam emittances have been measured with an X-ray pinhole camera system. The evolution of the system and its performances are presented here. As a result of the excellent alignment of the ring magnets, the vertical beam size is smaller than expected, that led us to an effort towards improving the initial resolution of the instrument. A high sensitivity CCD camera allows us to select the harder X-ray part of the radiation which is a key element for resolution improvement. Finally an evaluation of the ultimate pinhole resolution is made for SOLEIL.  
 
TUPC18 New Type Photocathode for X-Ray Streak Camera of the 10-Fs Resolution electron, monitoring, vacuum, space-charge 183
 
  • A. M. Tron
    LPI, Moscow
  • T. V. Gorlov
    MEPhI, Moscow
  High current streak camera with new principle of operation* allowing to get resolution of the order of 10 fs in the frequency range both of visible light and x-ray is described. One of the key units of the camera is photocathode of spherical configuration with its surface radius of 10…100 micrometers. For creating the photocathode new technologies, developed and realized, are described. The results of the photocathode fabrication and investigations of its main features are presented and discussed.

* A. M. Tron, I. G. Merinov, T. Gorlov. New generation streak camera design and investigation. Proc. of EPAC 2006, p. 1175.

 
 
TUPC26 Button Beam Position Monitors for FLASH undulator, pick-up, electron, linac 201
 
  • J. Lund-Nielsen, N. Baboi
    DESY, Hamburg
  • W. Riesch
    DESY Zeuthen, Zeuthen
  Abstract: FLASH (Free Electron Laser in Hamburg) accelerates electron bunches to up to 750 MeV for producing intense, coherent, very short pulses of radiation. Various types of BPMs (beam position monitors) are installed in the facility: cavity and re-entrant-cavity BPMs in the accelerating cryo-modules and button and stripline BPMs in most of the room-temperature sections. The undulator section, where the FEL radiation is produced, is one of the most critical areas of the linac in terms of requirements on the position monitoring. Due to the tight space, button BPMs were chosen for this area. The electronics is based on the AM/PM principle. In the past couple of years these BPMs were commissioned and intensively studied. A few modifications have been made in the electronics, in order to deal with the small signals and the very high frequencies of the ultra-short bunches. In this paper the button-BPMs at FLASH will be presented. The studies made in the RF laboratory and the measurements made on the performance of the BPMs will be discussed.  
 
WEO1A01 Sub-ps Timing and Synchronization Systems for Longitudinal Electron Bunch Profile Measurements laser, electron, undulator, diagnostics 204
 
  • A. Winter
    DESY, Hamburg
  Precise timing and synchronization systems have become an increasingly important topic for next generation light sources. Particularly free electron lasers can emit X-ray pulses with pulse durations down to the few-tens of femtoseconds level. In order to utilize this potential temporal resolution for pump-probe experiments, a precise synchronization of the experimental laser to the X-ray pulse and stabilization of the electron beam arrival time at the undulators are mandatory. This requires a timing and synchronization system which can supply ultra-stable phase references over long distances, thus enabling the temporal stabilization of the electron beam to a sub-100 fs level. Furthermore, a precise timing and synchronization system renders possible extremely accurate measurements of the longitudinal electron bunch profile. This talk will give an overview of the status of existing sub-ps timing and synchronization systems and of systems currently under construction.  
 
WEO1A03 Instrumentation for Longitudinal Beam Gymnastics in FEL's and in the CLIC test facility 3 electron, linac, diagnostics, pick-up 215
 
  • T. Lefèvre, H.-H. Braun, E. Bravin, S. Burger, R. Corsini, S. Döbert, L. Søby, F. Tecker, P. Urschütz, C. P. Welsch
    CERN, Geneva
  • D. Alesini, C. Biscari, B. Buonomo, O. Coiro, A. Ghigo, F. Marcellini, B. Preger
    INFN/LNF, Frascati (Roma)
  • P. Craievich, M. Ferianis, M. Veronese
    ELETTRA, Basovizza, Trieste
  • A. E. Dabrowski, M. Velasco
    NU, Evanston
  • A. Ferrari
    UU/ISV, Uppsala
  Built at CERN by an international collaboration, the CLIC Test Facility 3 (CTF3) aims at demonstrating the feasibility of a high luminosity 3TeV e+-e- collider by the year 2010. One of the main issues to be demonstrated is the generation of a high average current (30A) high frequency (12GHz) bunched beam by means of RF manipulation. At the same time, Free Electron Lasers (FEL) are developed in several places all over the world with the aim of providing high brilliance photon sources. These machines all rely on the production of high peak current electron bunches. The required performances put high demands on the diagnostic equipment and innovative longitudinal monitors have been developed during the past years. This paper gives an overview of the longitudinal instrumentation developed at ELETTRA and CTF3, where a special effort was made in order to implement at the same time non-intercepting devices for online monitoring, and destructive diagnostics which have the advantage of providing more detailed information.  
 
WEPB03 Femtosecond Yb-Doped Fiber Laser System at 1 um of Wavelength with 100-nm Bandwidth and Variable Pulse Structure for Accelerator Diagnostics laser, electron, diagnostics, polarization 235
 
  • A. Winter, B. Steffen
    DESY, Hamburg
  • F. O. Ilday
    Bilkent University, Bilkent, Ankara
  Laser-based diagnostic systems play an increasingly important role in accelerator diagnostics in, for instance, measurements of the electron bunch length. To date, the laser system of choice for electro-optic experiments has been the Ti:Sa laser. These offer nJ pulse energies at fixed repetition rate between 50-100 MHz, which is not well suited to the bunch structure of facilities such as FLASH (several hundred pulses with 1 MHz spacing at 1-5 Hz repetition rate).The limited robustness, stability and operability of Ti:Sa systems make them less than an ideal candidate for a continuously running measurement system requiring minimal maintenance. Fiber lasers represent a promising alternative, since gating and subsequent amplification is simple and of low cost, hence a pulse pattern corresponding exactly to the linac bunch pattern can be generated. Furthermore, these lasers offer superior robustness at a fraction of the cost of a Ti:Sa laser and have been shown to work without maintenance for several months and longer. Here, we present an ytterbium-doped fiber laser system with 80 nm bandwidth and multi-nJ pulse energy with adjustable bunch pattern for use in electro-optic experiments.  
 
WEPB05 Streak Camera Measurements of the SOLEIL Bunch Length single-bunch, impedance, electron, vacuum 241
 
  • M. Labat, L. Cassinari, M.-E. Couprie, R. Nagaoka, D. Pédeau
    SOLEIL, Gif-sur-Yvette
  A double sweep streak camera (C5680, Hamamatsu) has been installed on the French third generation light source SOLEIL. The visible radiation of the diagnostics beam-line is used to study the longitudinal profile of the stored electron bunches. We report on the commissioning of the streak camera, as well as on its first uses. Measurements of single-bunch length as a function of various machine parameters such as RF cavity voltage and frequency, and beam current with a few picoseconds resolution are reported, and interpreted in terms of vacuum chamber impedance and beam stability.  
 
WEPB08 Noise and drift characterization of critical components for the laser based synchronization system at FLASH laser, extraction, free-electron-laser, optics 250
 
  • B. Lorbeer, B. Lorbeer
    TUHH, Hamburg
  • F. Löhl, F. Ludwig, J. M. Müller, H. Schlarb, A. Winter
    DESY, Hamburg
  At FLASH, a new synchronization system based on distributing streams of short laser pulses through optical fibers will be installed and commissioned in 2007. At several end stations, a low drift- and low noise conversion of the optical signal into RF signals is needed. In this paper, we present the influence of photodiodes on the phase stability of the optical pulse streams and investigate the drift performance of the photo-detection scheme for the extraction of the RF signal.  
 
WEPB13 Focusing of Optical Transition and Diffraction Radiation by a Spherical Target target, electron, focusing, diagnostics 259
 
  • L. G. Sukhikh, G. A. Naumenko, A. Potylitsyn
    TPU, Tomsk
  • A. S. Aryshev, J. Urakawa
    KEK, Ibaraki
  • S. T. Boogert, V. Karataev
    JAI, Egham, Surrey
  During the last few years Transition Radiation (TR) and Diffraction Radiation (DR) have been intensively studied for different applications such as diagnostics of electron beam size, emittance, length, energy spread, etc. For extremely high-energy electrons the broadening of TR (DR) spatial distribution due to “pre-wave” zone effect [*] leads to distortion of the radiation characteristics and decreasing of photon concentration per unit square detector. In papers [**,***] it was shown that using a spherical target one can make TR (DR) distribution in the pre-wave zone identical to a far-field one. To verify our approach we carried out an experiment at KEK-ATF extraction line with electron beam energy of 1.28 GeV using a spherical target to focus optical TR (DR) at the distance of L=440 mm which corresponds to an extreme pre-wave zone. We also measured OTR (ODR) characteristics from a flat target in order to compare them with OTR (ODR) characteristics from the spherical one. We clearly observed that OTR (ODR) angular distribution from the spherical target is narrower than from a flat one and it’s very similar to a far-field zone distribution as it was predicted by the theory.

* V. A.Verzilov, PLA 273(2000)135** P. V.Karataev, PLA 345(2005)428*** A. P. Potylitsyn and R. O. Rezaev, NIMB 252(2006)44

 
 
WEPB18 Electron Beam Temperature Measurements at the Fermilab Medium Energy Electron Cooler electron, antiproton, optics, diagnostics 268
 
  • A. Warner, K. Carlson, G. M. Kazakevich, L. R. Prost, M. Sutherland
    Fermilab, Batavia, Illinois
  The Fermilab Recycler ring employs an electron cooler to store and cool 8.9-GeV antiprotons. The cooler is based on an electrostatic accelerator (Pelletron) working in an energy-recovery regime. Several techniques for determining the characteristics of the beam dynamics have been investigated. Beam temperature measurements using OTR in conjunction with a Pepper-pot have been made at several settings of the upstream optics of the machine. Without temperature the pepper-pot hole images would have sharp boundaries. A finite temperature makes these boundaries broader. Thus, comparison of the ratios of the hole image boundaries and intensities is a measure of the beam temperature. In this paper we report the results so far obtained using this technique.  
 
WEPB26 Transition Thermal Processes In Vibrating Wire Monitors vacuum, photon, undulator, instrumentation 292
 
  • S. G. Arutunian, M. R. Mailian
    YerPhI, Yerevan
  • G. Decker
    ANL, Argonne, Illinois
  • G. Rosenbaum
    UGA, Athens, Georgia
  Dynamic characteristics of vibrating wire monitors (VWM) strongly depend on the media where the wire oscillates, and also on the geometry and materials of the wire and VWM housing. On the basis of a one-dimensional model of heat transfer along the wire, the time characteristics of transition processes of thermal equilibrium profiles are defined for wires of different materials and geometry. To decrease the response time of the VWM, a new scheme of measurement with constant mean temperature is suggested. In addition to the flux of particles/radiation deposited on the wire, the additional DC current maintains a constant wire oscillation frequency. The value of DC current serves as measure of particles/radiation flux.  
 
WEPC03 Secondary Electron Emission Beam Loss Monitor for LHC electron, proton, simulation, beam-losses 313
 
  • D. K. Kramer, B. Dehning, G. Ferioli, E. B. Holzer
    CERN, Geneva
  Beam Loss Monitoring (BLM) system is a vital part of the active protection of the LHC accelerators’ elements. It should provide the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. The LHC BLM system will use ionization chambers as standard detectors but in the areas where very high dose rates are expected, the Secondary Emission Monitor (SEM) chambers will be employed because of their high linearity, low sensitivity and fast response. The SEM needs a high vacuum for proper operation and has to be functional for up to 20 years, therefore all the components were designed according to the UHV requirements and a getter pump was included. The SEM electrodes are made of Ti because of its Secondary Emission Yield (SEY) stability. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production. The prototypes were calibrated by proton beams in CERN PS Booster dump line, SPS transfer line and in PSI Optis line. The results were compared to the simulations.  
 
WEPC06 Single gain radiation tolerant LHC beam loss acquisition card beam-losses, monitoring, survey, insertion 319
 
  • E. Effinger, B. Dehning, J. E. Emery, G. Ferioli, C. Zamantzas
    CERN, Geneva
  The beam loss monitoring system is one of the most critical elements for the protection of the LHC. It must prevent the super conducting magnets from quenches and the machine components from damages, caused by beam losses. Ionization chambers and secondary emission based detectors are used on several locations around the ring. The sensors are producing a signal current, which is related to the losses. This current will be measured by a tunnel card, which acquires, digitizes and transmits the data via an optical link to the surface electronic. The usage of the system, for protection and tuning of the LHC and the scale of the LHC, imposed exceptional specifications of the dynamic range and radiation tolerance. The input dynamic allows measurements between 10pA and 1mA and its protected to high pulse of 1.5kV and its corresponding current. To cover this range, a current to frequency converter in combination with an ADC is used. The integrator output voltage is measured with an ADC to improve the resolution. The radiation tolerance required the adaption of conceptional design and a stringent selection components.  
 
WEPC09 Classification of the LHC BLM Ionization Chamber simulation, proton, space-charge, target 328
 
  • M. Stockner, B. Dehning, C. Fabjan, E. B. Holzer
    CERN, Geneva
  • D. K. Kramer
    TUL, Liberec
  The LHC beam loss monitoring (BLM) system must prevent the super conducting magnets from quenching and protect the machine components from damage. The main monitor type is an ionization chamber. About 4000 of them will be installed around the ring. The lost beam particles initiate hadronic showers through the magnets and other machine components. These shower particles are measured by the monitors installed on the outside of the accelerator equipment. For the calibration of the BLM system the signal response of the ionization chamber to all relevant particles types and energies (keV to TeV range) is simulated in GEANT4. For validation, the simulations are compared to measurements using protons, neutrons, photons, muons and mixed radiation fields at various energies and intensities. This paper will focus on the signal response of the ionization chamber to various particle types and energies including recombination effects in the chamber gas at high ionization densities.  
 
WEPC14 Segmented Beam Dump for Time Resolved Spectrometry on a High Current Electron Beam electron, simulation, scattering, linac 340
 
  • T. Lefèvre, H.-H. Braun, E. Bravin, C. Dutriat, C. P. Welsch
    CERN, Geneva
  In the CLIC Test Facility 3, the strong coupling between the beam and the accelerating cavities induces transient effects such that the head of the pulse is accelerated twice as much as the rest of the pulse. Three spectrometer lines are installed along the linac with the aim of measuring energy spread versus time with a 20ns resolution. The major difficulty is due to the high power carried by the beam which imposes extreme constraints of thermal and radiation resistances for the detector. This paper presents the design and the performances of a simple and easy-to-maintain device, called ‘segmented dump’. In this device, the particles are stopped inside metallic plates and the deposited charge is measured in the same way as in faraday cups. Simulations were carried out with the Monte Carlo code ‘FLUKA’ in order to evaluate the problems coming from the energy deposition and find ways to prevent or reduce them. The detector resolution has been optimized by choosing the adequate material and thickness for the plates. The overall layout of the monitor is described with a special emphasis on its mechanical assembly. Finally, limitations arising at high beam energies are discussed.  
 
WEPC21 Diagnostics of the Waveform of Picosecond Electron Bunches Using the Angular Distribution of Coherent Sub-mmTransition and Diffraction Radiation electron, target, linac, vacuum 355
 
  • A. G. Shkvarunets, R. B. Fiorito
    UMD, College Park, Maryland
  • F. Mueller, V. Schlott
    PSI, Villigen
  The spectra of sub-mm wavelength coherent transition radiation (TR) and diffraction radiation (DR) have previously been used to measure the bunch length of picosecond electron beam pulses. However, both the spectral and angular distributions of the radiation from a finite target or aperture with size r, are strong functions of the wavelength, when λ ≈ 2πr/γ where γ is the relativistic factor of the beam. This dependence must be taken into account in the determination of the bunch form factor and bunch shape. Also the spectral density of the bunch is a strong function of wavelength when λ ≈ d, the characteristic length of the bunch. When both the above conditions are fulfilled, i.e. λ ≈ 2πr/γ ≈ d, the spectral and angular distribution (AD) of the radiation are very sensitive to the longitudinal distribution of the bunch. We are investigating the use of the AD of TR or DR, to diagnose the bunch length and shape. Here we present a comparison of measured and calculated angular distributions from two targets: a solid disk and a rectangular slit, which we have used to determine the waveform of the beam bunch produced at PSI’s SLS pre-injector LINAC.  
 
WEPC27 Segmented Foil SEM Grids for High-Intensity Proton Beams at Fermilab proton, beam-losses, vacuum, booster 370
 
  • Z. Pavlovic, D. Indurthy, S. E. Kopp, M. Proga, R. M. Zwaska
    The University of Texas at Austin, Austin, Texas
  • B. B. Baller, S. C. Childress, R. D. Ford, D. Harris, C. L.K. Kendziora, C. D. Moore, G. R. Tassotto
    Fermilab, Batavia, Illinois
  The extracted beam transport lines and transfer lines between accelerators at Fermilab must operate at ever higher proton fluences to service the neutrino program and the production of antiprotons for the Tevatron collider program. The high proton fluences place stringent criteria on invasive instrumentation to measure proton beam profiles. Based on a design from CERN, we have built SEM's consisting of Ti foils segmented at either 1.0mm or 0.5mm pitch. The foils are 5um thick Titanium, and two planes of the segmented foils per SEM chamber provides both horizontal and vertical beam profiles. The foil SEM's provide several features over the Au-plated 75 um Ø W-wire SEM's previously in use at Fermilab: (1) a factor 50-60 lower fractional beam loss; (2) greater longevity of Ti signal yield, as compared with W or Au-W; (3) a 'bayonnette'-style frame permitting insertion/retraction from the beam without interruption of operations; and (4) reduced calculated beam-heating from the high-intensity proton-pulses, which results in less sag of the wires/foils. Experience with these detectors after two years' operations in 8 and 120GeV beams will be summarized.