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MOO3A02 Beam Induced Fluorescence (BIF) Monitor for Transverse Profile Determination of 5 to 750 MeV/u Heavy Ion Beams ion, background, photon, electron 33
 
  • F. Becker, C. A. Andre, P. Forck
    GSI, Darmstadt
  • D. Hoffmann
    TU Darmstadt, Darmstadt
  In the frame of the FAIR-project (facility for antiproton and ion research) at GSI, high intensity beams from protons to Uranium ions in the energy range from 100 MeV/u to 30 GeV/u are foreseen. In transport lines between the synchrotrons and in front of production targets a precise beam alignment is mandatory. Since the beam energy will increase from 90 Joule to about 104 Joule per ion pulse, conventional intercepting beam diagnostics may not be used. For transverse profile determination we investigated a non-intercepting Beam Induced Fluorescence (BIF) monitor in residual nitrogen. An image intensified CCD camera was used to record the fluorescence images representing the beam profile. The photon yield and background contribution were determined for different ion species, beam energies and N2 pressures. Applying narrowband 10 nm interference filters we mapped the spectral response and associated it with the N2 transitions. Profile distortions were compared to simulations taking into account effects as momentum transfer, gas dynamics and the electrical field of the ion beam. Additionally the feasibility and appropriate layout for different diagnostic tasks is discussed.  
slides icon Slides  
 
MOO3A03 First Vibrating Wire Monitor Measurements of a Hard X-ray Undulator Beam at the Advanced Photon Source photon, radiation, resonance, 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  
 
TUPB01 A Fiber Profile Monitor for low Beam Intensities. secondary-beams, target, background, controls 51
 
  • G. R. Tassotto, H. Nguyen, D. P. Schoo, G. W. Sellberg
    Fermilab, Batavia, Illinois
  A scintillating Fiber Profile Monitor (FPM) has been prototyped, built and tested for the new low intensity Meson Test (M-Test) beamline at Fermilab. The beamline has the following beam parameters: E = 1-120 GeV, I from a few hundreds to 700,000 particles/spill, and the spill length is 4.5 seconds. Segmented Wire Ion Chambers (SWICs) and Proportional Wire Chambers (PWCs) do not display the beam profile accurately below about 10,000 particles. For the prototype FPM detector a modified SWIC vacuum can was used. An (x, y) array of fibers replaced the chamber containing windows, gas, and AuW wires soldered on a ceramic substrate. The fibers were purchased from Saint Gobain and are of the type BCF-12 MC, 420 nm wavelength They have a diameter of 0.75 mm and are coated with black EMA for optical isolation. The 64 channel fibers are positioned and then epoxied in a vacuum feed-thru “cookie” to match a Burle 64 channel multianode microchannel plate PMT of the type Planacon # 85011-501. The gain of the Planacon PMT is 800,000 at –2400 Volts. Unlike SWICs or PWCs, this device will allow for vacuum continuity. Comparative data with PWCs will be presented.  
 
TUPB02 Stripline Transversal Filter Techniques For Sub-Picosecond Bunch Timing Measurements feedback, diagnostics, synchrotron, controls 54
 
  • J. D. Fox, T. Mastorides
    SLAC, Menlo Park, California
  Measurement of time of arrival of a particle bunch is a fundamental beam diagnostic. The PEP-II/ALS/BESSY/PLS longitudinal feedback systems use a planar stripline circuit structure to convert a 30 ps beam BPM impulse signal into a 4 cycle tone burst at the 6th harmonic of the accelerator RF frequency (roughly 3 GHz). A phase-detection technique is used to measure the arrival time of these BPM impulses with 180 fs rms single-shot resolution (out of a 330 ps dynamic range). Scaled in frequency, this approach is directly applicable to LCLS, FEL and other sub-fs regime pulse and timing measurements. The transversal circuit structure is applicable to measurement of microbunches or closely spaced bunches (the PEP-II examples make independent measurements at 2 nS bunch spacing) and opens up some new diagnostic and control possibilities. This paper reviews the principles of the technique, and uses data from PEP-II operations to predict the limits of performance of this measurement scheme for arrival phase measurement. These predictions are compared with results in the literature from electro-optic high-resolution sub-picosecond beam timing and phasing diagnostics.

* Briggs, et al, "Prompt Bunch by Bunch Synchrotron Oscillation Detection by a Fast Phase Measurement", Proceedings of the IEEE Particle Accelerator Conference, 5/91, 1404-1406

 
 
TUPB03 Precision Beam Position Monitor for EUROTeV pick-up, electron, linear-collider, collider 57
 
  • I. Podadera Aliseda, L. Søby
    CERN, Geneva
  For future linear colliders (ILC, CLIC) a new Precision Beam Position Monitor (PBPM) has been designed within the framework of EUROTeV. The design goals are a resolution of 100nm and an overall precision of 10μm, in a circular vacuum chamber of 6mm in diameter. The required bandwidth is 100 kHz-30MHz. The PBPM is based on an inductive type BPM which measures the image current in four electrodes located outside the vacuum tube, from which the position is derived. In this paper, the design of the PBPM is presented together with the first bench measurements, where twoμmovers and a rotational stage, installed on a vibration damped table, have been used to characterize the PBPM.  
 
TUPB07 Electric -In-Air-X-Ray- Detectors for high Resolution Vertical Beam Position Measurement at the ESRF feedback, diagnostics, dipole, emittance 69
 
  • K. B. Scheidt
    ESRF, Grenoble
  The tiny fraction of the very hard X-rays that fully penetrate the dipole absorber structure and enter the free air space behind it can be detected in different ways to yield precise information on the vertical characteristics of the electron beam. In addition to a system of imaging detectors to measure the emittance, a 2nd detector type was developed that yields a direct electric signal. It consists of a high-Z blade in conjuction with a small In-Air ionization slot that generates a direct strong electric signal allowing for nanometer resolution measurements of vertical beam motion in a spectrum upto 1KHz. The high resolution performance of this detector type is explained by the fact that it touches the heart and center of the beam whereas other devices (X-BPMs or e-BPMs) have to work on the edges or tails of the beam or feel the beam indirectly by wall-current pick-ups. The results obtained with prototypes will be presented together with the prospects of an installation of 8 units in 2007. The intrinsic advantages of this In-Air detector like costs and simplicity, thanks to a total absence of cooling and UHV requirements, will be emphasized.  
 
TUPB19 Signal Level Calculation for the PETRA-III Beam Position Monitor System insertion, pick-up, controls, insertion-device 105
 
  • G. Kube, M. Werner
    DESY, Hamburg
  Starting mid 2007 the PETRA accelerator at DESY in Hamburg (Germany) will be converted into a new high brilliance light source. For measurement and control of the PETRA-III closed orbit with a resolution of better than 1 micrometer (rms) it is planned to install about 220 button type beam position monitors (BPMs). To guarantee a good performance of the BPM electronics, the button signals have to meet several criteria in time and frequency domain. Therefore signal levels for the monitor types included for installation have been estimated. The results of these calculations will be presented together with a comparison of monitor signals from accelerators in operation, and the expected position resolution will be discussed for a certain type of BPM electronics.  
 
TUPB20 Large Horizontal Aperture BPM and Precision Bunch Arrival Pickup pick-up, laser, electron, simulation 108
 
  • K. E. Hacker, F. Löhl, H. Schlarb
    DESY, Hamburg
  The large horizontal aperture chicane BPM and the precision bunch arrival monitor at FLASH will be important tools to stabilize the arrival-time of the beam at the end of the linac. The pickups for these monitors will be paired with front-ends that sample the zero-crossing of the beam transient through the use of electro-optical modulators and sub-picosecond-long laser pulses delivered by the master-laser oscillator. The design of pickups for this front-end requires the consideration of the beam transient shape as well as the amplitude. Simulations and oscilloscope traces from pickups that use or will use the EOM based phase measurement and the expected limitations and benefits of each pickup are presented. In particular, the design for a 5 um resolution BPM with a 10 cm horizontal aperture is demonstrated in terms of its capability to measure the beam energy and its sensitivity to the shape and orientation of the beam.  
 
TUPB24 First Results from the LEIR Ionisation Profile Monitors ion, electron, controls, accumulation 120
 
  • G. Tranquille, C. B. Bal, V. Prieto, R. S. Sautier
    CERN, Geneva
  The role of the Low Energy Ion Ring, LEIR is to transform long pulses of lead ions from the Linac 3 to short dense bunches for transfer to the LHC. This is accomplished by the accumulation of up to 4 Linac pulses by electron cooling. In order to non-destructively monitor the cooling performance and determine the accumulated beam characteristics, two prototype ionisation profile monitors have been built and were tested during the LEIR commissioning runs with O4+ and Pb54+ ions in 2006. In this paper we present the results obtained with the prototype monitors, the problems encountered and describe the modifications made for the final design. The modified monitors have been installed on the LEIR machine and are waiting for the next ion run planned in August.  
 
TUPC13 The new Diode BPM system for ELETTRA controls, undulator, storage-ring, pick-up 177
 
  • R. De Monte
    ELETTRA, Basovizza, Trieste
  A new Beam Position Monitor system has been developed at ELETTRA based on an envelope detector. It is a four channel system reading in parallel the four voltages from a button pick-up that adopts a wide-band Schottky diode. The analogue bandwidth of the currently implemented detector is <1kHz which has been adapted to the present application of the system, i.e. a fast beam position interlock to be installed on the ELETTRA storage ring. The upgrade of the ELETTRA BPM which is based on the Libera detector suggested us to add some redundancy on the fast position interlock in order to protect the vacuum chamber from wrong positions / angles of the beam. The data collection scheme, based on a single board computer for each straight section, is presented. Currently, the system has been installed and tested on all the ELETTRA undulator sections; the first running experience is here presented.  
 
TUPC18 New Type Photocathode for X-Ray Streak Camera of the 10-Fs Resolution radiation, electron, monitoring, 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.

 
 
TUPC19 Matlab Code for BPM Button Geometry Computation storage-ring, booster, controls, linac 186
 
  • A. Olmos, F. Pérez
    ALBA, Bellaterra
  • G. Rehm
    Diamond, Oxfordshire
  Third generation Synchrotron Light Sources with vertical beam sizes down to few microns require beam resolutions on the submicron level. Study of different Beam Position Monitors (BPM) geometries has been done to reach such tight requirements. The used Matlab Graphical User Interface (GUI) is based on the simulation of a charged particle inside a selectable vacuum chamber type, computing the induced signal that it produces on the button feedthroughs. Needed parameters for the computation are the button electrode dimensions, vacuum chamber profile, electron beam current and measurement bandwidth. Output results from the GUI are the induced power on the feedthroughs, BPM sensitivity and intrinsic resolution of the analyzed geometry. As sensitivity and resolution are BPM geometry dependent terms, the Matlab GUI turned out to be an easy and fast way for first step geometry analysis.  
 
TUPC20 The SOLEIL BPM and Orbit Feedback Systems feedback, controls, storage-ring, instrumentation 189
 
  • N. Hubert, L. Cassinari, J.-C. Denard, N. L. Leclercq, A. Nadji, L. S. Nadolski, D. Pédeau
    SOLEIL, Gif-sur-Yvette
  SOLEIL is a third generation light source built in France, near Paris. Its BPM system is important for machine studies and for delivering stable beams to the users. A beam stable to 1/10th of the dimensions requires submicron stability in the vertical plane. The monitors, anchored either to the girders or to the ground, are fixed points of the vacuum chamber. Bellows avoid transverse drifts due to mechanical stress. The electronics design was driven by combined efforts through an active communication between accelerator labs (SOLEIL at first, later joined by DIAMOND) and Instrumentation Technologies. The result is the “Libera Electron” beam position processor. It combines a 0.2μm rms resolution and micron level stability for beam delivery with accurate turn-by-turn measurements (3μm resolution at 0.8MHz) for machine commissioning and beam physics studies. It also features position interlock, tune measurement, and postmortem capabilities. A Slow Orbit Feedback for correcting low frequency drifts (0 to 0.1Hz) is currently in operation. The Fast Orbit Feedback to be implemented soon will suppress higher frequency perturbations up to 100Hz.  
 
TUPC23 Design of a Submicron Resolution Cavity BPM for the ILC Main Linac dipole, coupling, linear-collider, collider 192
 
  • A. Lunin, G. Romanov, N. Solyak, M. Wendt
    Fermilab, Batavia, Illinois
  A high resolution Beam Position Monitor (BPM) is necessary for the beam-based alignment and feedback systems of the future international linear collider (ILC). We present the cavity BPM developed at Fermilab within ILC collaboration. This monitor will be operated at cryogenic temperature and rigidly attached to the quad magnet. The same cylindrical cavity is used to obtain the signals from both dipole and monopole modes excited by beam. Such a scheme makes the BPM more compact for placing it inside the magnet space and simplifying the signal processing. The dipole TM110 mode is utilized to measure pulse to pulse beam motion at a theoretical resolution of approximately 50 nm. In order to measure a single bunch trajectory within 300 ns timescale we use a resonant coupling to lower cavity Q-factor. The ceramic windows are brazed inside coupling slots for vacuum isolation and easy cavity cleaning. We will present a BPM detailed numerical study and analyze its tolerance requirements for submicron resolution.  
 
TUPC24 A Versatile Emittance Meter and Profile Monitor ion, emittance, ion-source, heavy-ion 195
 
  • H. R. Kremers, J. P.M. Beijers, S. Brandenburg
    KVI, Groningen
  We present the design, construction and the first results of a new, versatile emittancemeter and profilemonitor for low-energy, multiply-charged ion beams. Both instruments share the same basic design, e.g. they fit on the same size vacuum flange and many parts can be exchanged. The central component of both instruments is a beam-imaging device, consisting of two multi-channel plates (MCP) in the chevron configuration followed by a phosphor screen. This combination transforms the two-dimensional beam-intensity distribution to a two-dimensional light-intensity distribution, which is imaged via a mirror and a lens system onto a CCD camera mounted outside the vacuum. The MCP, phosphor screen and mirror are mounted on a table which can be moved in and out of the beam. For emittance measurements the device is equipped with a pepperpot plate with a pattern of small holes in one direction, which is stepped through the beam in the orthogonal direction. The structure of the pattern can be adapted to the expected shape of the emittance. By taking images of the beamlets passing through the holes at a number of positions the full four-dimensional beam emittance can be reconstructed.  
 
WEO2A01 Beam Diagnostics for the Front End Test Stand at RAL emittance, ion, ion-source, simulation 218
 
  • S. Jolly, D. A. Lee, P. Savage
    Imperial College of Science and Technology, Department of Physics, London
  • D. C. Faircloth, J. K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon
  • C. Gabor
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL) is intended to demonstrate the early stages of acceleration (0-3MeV) and beam chopping required for high power proton accelerators, including proton drivers for pulsed neutron spallation sources and neutrino factories. The FETS ion source is required to produce a 60 mA beam in pulses up to 2ms long at up to 50 pps with an RMS emittance of 0.3 π mm mrad. A number of different diagnostic systems are currently under development to provide precise measurements of the H- ion beam. A pepperpot emittance measurement system, which is also capable of high resolution transverse beam density measurements, has been designed for use on the ISIS ion source development rig. This system is capable of sub-microsecond time-resolved measurements at a range of positions along the beam axis. Details are given of the improvements to the current design, including extensive tests on suitable scintillators and emittance and profile measurements are presented. Additionally, the designs of two different novel laser diagnostic systems for FETS are also presented.  
 
WEPB05 Streak Camera Measurements of the SOLEIL Bunch Length single-bunch, impedance, electron, radiation 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.  
 
WEPB09 Mechanical Design of the Intensity Measurement Devices for the LHC impedance, alignment, shielding, resonance 253
 
  • D. B. Belohrad, S. Longo, OP. Odier, S. Thoulet
    CERN, Geneva
  The intensity measurement for the LHC ring is provided by eight current transformers: 2 DC current transformers (DCCTs) and 2 fast transformers (FBCTs) per vacuum chamber. The measurement precision of 1uArms at averaging over 1s time interval for the DCCTs and ±109 charges in 25ns bunch measurements for the FBCTs is required. Such constraints call for low noise electronics and a compact magnetically shielded mechanical design. Due to ultra high vacuum requirements in the LHC the vacuum chambers are equipped with the non-evaporable getter (NEG) film. The NEG is activated by heating the vacuum chamber to 200°C and more. Such temperatures affect the structure of the magnetic materials, which form the base part of the intensity measurement devices, and degrade their performance. A cooling circuit is needed. Due to the mechanical constraints, the cooling circuit, as well as heating element must form an integral part of the design. The paper presents the solution of these problems and discusses the mechanical construction of the DCCTs and FBCTs currently being installed in the LHC.  
 
WEPB12 Measurement of Bunch Lengthening Effects Using a Streak Camera with Reflective Optics optics, impedance, synchrotron, coupling 256
 
  • T. Obina, T. Mitsuhashi
    KEK, Ibaraki
  For the precise measurement of the bunch length, the incident optics of a streak camera must be free from an optical path difference due to chromatic effects. We designed and installed a reflective optics for the streak camera, and measured the bunch length as a function of the beam current. In the KEK Photon Factory, almost one half of the vacuum components were replaced in 2005. We measured the bunch lengthening effects before and after the replacement. The threshold-current of the microwave instabilities showed the impedance of the storage ring was greatly improved. This paper describes the detail of measurement and the calculations of the impedance of vacuum components.  
 
WEPB22 Touschek Lifetime Measurement with a Spurious Bunch in UVSOR-II Electron Storage Ring electron, single-bunch, scattering, storage-ring 280
 
  • A. Mochihashi, M. Katoh, M. Shimada
    UVSOR, Okazaki
  • Y. Hori
    KEK, Ibaraki
  • M. Hosaka, Y. Takashima
    Nagoya University, Nagoya
  We have developed a method to measure the Touschek beam lifetime of an electron storage ring using spurious bunches in single-bunch operation by measuring change in the single-bunch impurity over time. To measure a spurious bunch and the main bunch simultaneously, we use a photon counting method with sufficient dynamic range and response time. We demonstrated the method by measuring the Touschek beam lifetime in the UVSOR-II electron storage ring. We find that the Touschek beam lifetime dominates the total beam lifetime in UVSOR-II in usual vacuum condition. The Touschek beam lifetime measurement in multibunch operation with the method will be discussed in the presentation.

A. Mochihashi, M. Katoh, M. Hosaka, Y. Takashima, Y. Hori, NIM-A 572 (2007) 1033-1041.

 
 
WEPB24 Machine Protection and Interlock Systems at Synchrotron SOLEIL storage-ring, diagnostics, booster, synchrotron 286
 
  • Y.-M. Abiven, F. Dohou, R. P. Patrick
    SOLEIL, Gif-sur-Yvette
  SOLEIL is a third generation Synchrotron radiation source located in France near Paris, having the classical accelerator structure consisting of a Linac pre-accelerator, a Booster accelerator and a Storage Ring, which are connected by two transfer lines[1]. Since January, the Storage Ring delivers photon beam to 9 beamlines. In order to protect the very sensitive and essential equipment during machine operation, (vacuum chambers, vacuum valves, mirrors, etc.) an interlock system has been implemented. This system is based on industrial and autonomous PLC (Programmable Logic Controller). This paper describes each level of the interlock chain from the diagnostics and vacuum sensors and processes, up to the backbone of the interlock system which stops the RF system.  
 
WEPB26 Transition Thermal Processes In Vibrating Wire Monitors photon, radiation, 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.  
 
WEPC16 Excitation Striplines for SOLEIL Fast Transverse Feedback impedance, simulation, feedback, kicker 343
 
  • C. Mariette, J.-C. Denard, R. Nagaoka
    SOLEIL, Gif-sur-Yvette
  SOLEIL, the French third generation light source, is equipped with excitation striplines for a tune monitor and for the (bunch-by-bunch) Fast Transverse Feedback* that has been recently implemented. A careful design of the striplines and their vacuum feedthroughs was aimed at maximizing the effectiveness of the excitation power via high shunt impedances, and minimizing the power taken from the beam via low parasitic mode losses. Three stripline kickers have been developed for these applications. We report on their design using RADIA and GdfidL simulation codes, on the fabrication of the striplines, and on the experimental results with beam.

* R. Nagaoka: Transverse Feedback Development at SOLEIL. ID 1257

 
 
WEPC17 Fast Orbit Feeback System Upgrade with New Digital Bpm and Power Supply in the Tls feedback, power-supply, controls, electron 346
 
  • C. H. Kuo, J. Chen, P. C. Chiu, K. T. Hsu, K. H. Hu, K.-B. Liu
    NSRRC, Hsinchu
  • A. Bardorfer
    Instrumentation Technologies, Solkan
  The BPMs of orbit feedback loop use analogy type in the TLS that is more than 10 years. The analogy type BPM provides high resolution position detection after signal processing. The new generation digital beam position monitor (DBPM) was performed recently. The BPM electronics are commercial available by using direct RF sampling technology, FPGA, and embedded control environment running GNU/Linux. The programmable nature of DBPM system is beneficial for multi-mode high precision beam diagnostics purposes. Sub-micron resolution is achieved for averaged beam position measurement with high update rate. The DBPM are seamless integrated with existed control system and is compatible with old BPM in the orbit feedback loop. In the same time, the corrector power-supply is also upgraded for wide bandwidth control. The integration of old and new BPM, power-supply control for fast orbit feedback will be discussed in this report.  
 
WEPC21 Diagnostics of the Waveform of Picosecond Electron Bunches Using the Angular Distribution of Coherent Sub-mmTransition and Diffraction Radiation radiation, electron, target, linac 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, booster, radiation 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.