LBNL, Berkeley, California
The 13th edition of the Beam Instrumentation Workshop (BIW08) took place at the Granlibakken Conference Center on the beautiful shores of Lake Tahoe in California during the first week of May 2008. About 130 participants registered for the workshop. Included in the program during the three and a half days were three tutorials, eight invited and seven contributed oral presentations, and more than 50 poster contributions. A discussion group session, and the vendor exhibition simultaneously held with the single day poster session, afforded many opportunities for informal discussion and idea exchange between attendees. During the workshop, the 2008 Faraday Cup Award that recognizes innovative achievements in beam diagnostics was also presented. In this talk, I will present the highlights from BIW08. The overall quality of the contributions was notably high, which made the selection of the topics for this talk quite difficult. Although I endeavored to produce a balanced choice of highlights, the final list is surely incomplete due to time limitations of the talk, and also it unavoidably reflects my personal point of view and preferences.
ORNL, Oak Ridge, Tennessee
UMD, College Park, Maryland
The Spallation Neutron Source (SNS) continues a ramp up in proton beam power toward the design goal of 1.4 MW on target. At Megawatt levels, US and Japanese studies have shown that cavitation in the Mercury target could lead to dramatically shortened target lifetime. Therefore, it will be critical to measure and control the proton beam distribution on the target, in a region of extremely high radiation and limited accessibility. Several sources of photons have been considered for imaging the beam on or near the target. These include a freestanding temporary screen, a scintillating coating, Helium gas scintillation, optical transition radiation, and a beam-heated wire mesh. This paper will outline the selection process that led to the current emphasis on coating development. In this harsh environment, the optics design presented significant challenges. The optical system has been constructed and characterized in preparation for installation. Optical test results will be described along with predictions of overall system performance.
GANIL, Caen
LPC, Caen
The SPIRAL2 project is based on a multi-beam driver facility in order to allow both ISOL and low-energy in-flight techniques to produce intense radioactive ion beams (RIB) in a new Facility. A superconducting linac capable of accelerating 5-mA deuterons up to 40 MeV is used to bombard both thick and thin targets. These primary beams will be used for the RIB production by several reaction mechanisms (fusion, fission, etc.) The production of high intensity RIB will be based on fission of uranium target induced by neutrons. These exotic particles will be produced, ionized, selected in a dedicated production building and transported to the existing CIME cyclotron for post acceleration. After this, they will be used in the present experimental area of GANIL. The construction phase of SPIRAL2 was officially started in 2005. The beam diagnostics for the production facility allow a pre-tuning with a stable beam followed by an extrapolation to the radioactive beam. Some diagnostic devices may also provide for equipment protections and for the safety systems. An overview is presented of the diagnostics which will allow tuning and control of the RIB in this new production facility.
YerPhI, Yerevan
BERGOZ Instrumentation, Saint Genis Pouilly
ANL, Argonne, Illinois
YSU, Yerevan
The Vibrating Wire Monitor (VWM) was developed for precise transversal profiling/monitoring of charged particle/photon beams. The extremely high sensitivity of VWM is achieved by sensitivity of wire natural oscillation frequency to wire temperature. Due to the rigidity of the wire support structure, the VWM is also sensitive to the environmental parameters. In this paper, it is shown that the main parameter of influence is the ambient temperature. The magnitude and character of this influence is investigated along with the effect of electromagnetic interference on the VWM electronics in an accelerator environment.
GSI, Darmstadt
At the GSI Linac and transfer lines several Beam Induced Fluorescence Monitors (BIF) for transverse profile determination are installed. The non-intercepting measurement principle is based on the excitation of residual gas molecules by the beam and the detection of the fluorescence photons with image intensified cameras. This allows simultaneous profile determination at multiple positions without beam disturbance. The software ProfileView is a data acquisition system to visualize and record the profiles of several BIF monitors along the beamline. One BIF monitor comprises two image intensified cameras with remote irises, timing interface, gas pressure control and remote reset functionality. The basic functions needed for daily operation are combined in an easy-to-use graphical user interface. Beside this 'operator mode' an 'expert mode' can be called by advanced users to control every hard- or software parameter of the whole system separately. This contribution describes the software design and its realization for communication and data display.
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
DESY, Hamburg
The characterization of the transverse phase space for high charge density and high energy electron beams is demanding for the successful development of the next generation light sources and linear colliders. Due to its non-invasive and non-intercepting features, Optical Diffraction Radiation (ODR) is considered as one of the most promising candidates to measure the transverse beam size and angular divergence. A thin stainless steel mask has been installed at 45° with respect to the DR target and normally to the beam propagation to reduce the contribution of synchrotron radiation background. In addition, interference between the ODR emitted on the shielding mask in the forward direction and the radiation from the DR target in the backward direction is observed. This is what we call Optical Diffraction Interferometry (ODRI). The contribution of this interference effect to the ODR angular distribution pattern and, consequently, its impact on the beam transverse parameters is discussed. Results of an experiment, based on the detection of the ODRI angular distribution to measure the electron beam transverse parameters and set up at FLASH (DESY, Hamburg) are discussed in this paper.
SLAC, Menlo Park, California
CERN, Geneva
Synchrotron-light telescopes will monitor the profiles of the two LHC proton beams. At collision energy (7 TeV), each telescope will image visible light from a superconducting dipole used to increase beam separation for the RF-cavities. At injection (0.45 TeV), this source must be supplemented by a two-period superconducting undulator 80 cm from the dipole. We will present the mechanical and optical layouts of the telescope. The initial plan to use dipole edge radiation at high beam energy, for its increased visible emission, suffers from significant diffractive blurring. We will instead collect radiation from the first 2 to 3 m of the dipole’s interior. An optical "trombone" delay line will provide the large shift in focus. We will discuss calculations and measurements of blurring by diffraction and by this extended source, and present an alternative optical design using off-axis elliptical mirrors.
GSI, Darmstadt
Technical University Darmstadt, Darmstadt
Optical properties of scintillating screens were studied for various materials and different ion beams at GSI. C2+, Ar10+, Ni9+ and U28+-ion beams were applied, in the energy range from 5.5 to 11.4 MeV/u with currents up to some mA, as delivered by the heavy ion LINAC at GSI. Scintillation screens are widely used and are an essential part of a pepper-pot emittance device for which the precise mapping of the beam profile is a critical issue. However, precise measurements of the beam profile yield ambivalent results, especially for high beam currents*,**. The investigations were not only focused on well-known scintillators but also ceramic materials with lower light yield were studied. Their properties (light yield, beam width and higher statistical moments) are compared with different Quartz-glass screens. The recorded beam width shows dependence on the scintillation material and a decrease of the light yield was observed for some materials. Additionally, the light yield and beam width depend significantly on the screen temperature, which is increased by the ion impact. The empirical results are discussed and concepts for further investigations on the materials are presented.
* E. Gütlich, P. Forck et al., GSI-Scientific Report 2007 p.105 and 2008 (to be published).
** E. Gütlich, P. Forck, et al., Proc. Beam Instrum. Workshop BIW, Lake Tahoe (2008).
CIEMAT, Madrid
The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA (CW) deuteron LINAC with the purpose of validating the technology that will be used in the future IFMIF accelerator. In such low energy and high current prototype accelerator, any device intercepting the beam could be destroyed. Thus, non interceptive profile monitors will be installed inside of a Diagnostics-Plate and along the High Energy Transport Line. CIEMAT group investigates a profile monitor based on the fluorescence of the residual gas. A high neutron and gamma flux environment (due to high deuteron beam current) stands for a hostile environment for most of electronic devices and fibers. The design must guarantee not only good spatial resolution but a reliable operation in such environment. Hence, different options for detectors, optical windows, fibers and shielding concepts have been considered to overcome these aspects. Transverse profilers will be used as well as a tool to perform emittance measurements through quad-scans. In this contribution, the design of a transverse profiler prototype for EVEDA, together with a brief discussion about mechanisms that can play a role in profile falsification will be presented.
ESRF, Grenoble
An additional electron beam emittance measurement at the ESRF storage ring is now installed that uses X-ray radiation from an undulator. The method consists in detecting the monochromatic spatial profile of the fifth harmonic of the undulator spectrum. The photon energy is roughly 30 keV, selected with a single bounce (3,1,1) Si monochromator. The X-rays are converted to visible light using a scintillating screen which is then imaged to a CCD camera. The emittance value is deduced from the image size, source distance, and the beta-function at the source point, taking into account the precisely known photon beam divergence. The direct use of undulator radiation is advantageous in terms of the precise knowledge of the source position and lattice parameters in the straight section. For this reason this device will find its main application as a horizontal emittance monitor with improved absolute precision compared to that of the pinhole cameras which are making use of bending magnet radiation. This paper will present the details of the method, the setup and the obtained results.
CERN, Geneva
UFC, Besançon
UTBM, Belfort
Scanning of a high intensity particle beam imposes challenging requirements on Wire Scanner system. It is expected to reach scanning speed of 20 m/s with position accuracy of the order of 1 μm. In addition a timing accuracy better than 1 millisecond is needed. The adopted solution consists of a wire holding fork rotating by maximal of 200°. Fork, rotor and angular position sensor are mounted on the same axis and located in a chamber connected to the beam vacuum. The requirements imply the design of a system with extremely low vibration, vacuum compatibility, radiation, and temperature tolerance. The adopted solution consists of a rotary brushless synchronous motor with the permanent magnet rotor installed inside of the vacuum chamber and the stator installed outside. The accurate position sensor will be mounted on the rotary shaft inside of vacuum chamber and has to resist bake-out temperature of 200°C and ionizing radiation up to tenth of kGy/years. A digital feedback controller allows maximum flexibility for the loop parameters and feeds the 3 phases input for the linear power driver. The paper will present a detail discussion of chosen concept and the selected components.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
Beam diagnostics based on synchrotron radiation can use imaging techniques that allow monitoring beam transverse dimensions in real time. In particular the bunch-by-bunch transverse beam diagnostics is a powerful method that allows investigations of transient phenomena in which bunch motion and beam instabilities are correlated to the position in the bunch train. Such diagnostic methods need photon array detectors with response time in the ns down to ps range and dedicated fast electronics. At DAΦNE, the e+/e- collider of LNF/INFN, preliminary measurements with a prototype of an IR array detector made by 32x2 pixels are in progress. The array has pixel of 50x50 μm2 characterized by a response time of about 1 ns per pixel measured with the IR emission of the SINBAD beamline. The array detector and the 64 channels dedicated electronics has been installed at the 3+L experiment, a dedicated diagnostics of the e+ DAΦNE ring used to monitor the transverse dimensions of the beam. In this paper we describe the apparatus built to obtain IR imaging of a SR source and a turn-by-turn and a bunch-by-bunch transverse diagnostics of the stored bunches with a sub-ns time resolution
CEA, Gif-sur-Yvette
Optical diagnostics based on the excitation of residual gas molecules are routinely used for high intensity beam characterization. Beam intensity, beam position and profile are measured by means of a CCD sensor. In addition species fraction and profile of each beam are measured using a Doppler shift method. As part of IFMIF-EVEDA* project, CEA is in charge of the design and realization of the 140mA-100keV cw deuteron source and low energy beam transport line. In the beam line, (D,d) reaction will occur and high neutron flux will be emitted when deuteron beam interacts with surfaces. Moreover gamma ray and activation will also occur. In order to protect diagnostics, coherent optic fibers could be used to transport the beam image outside the irradiated zone. A comparative study of two coherent fibers will be presented (FUJIKURA & SCHOTT), along with the characterization in magnification and attenuation of a 610 mm long fiber and its associated optics. To estimate the capability of such fibers to transport beam image, a dedicated experiment has been performed with proton beam produced by the SILHI source. The beam transverse profile has been compared with and without the optic fiber.
* International Fusion Materials Irradiation Facility - Engineering Validation and Engineering Design Activities
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
One of the key diagnostics instruments during the ALBA Linac commissioning was the screen monitors, which allowed control of beam size and position. These screen monitors are equipped with a YAG and an OTR screen. This paper describes our screen monitor setup and the experience with both types of screens.
PSI, Villigen
For the neutron spallation source SINQ at PSI a novel visual monitor (VIMOS) has been devised to guarantee correct beam conditions, triggered at the occasion of irradiating the delicate liquid metal target during the MEGAPIE project. VIMOS is looking directly for the most relevant parameter: it checks whether any point on the target is hotter than allowed. For this purpose the incandescence of a glowing mesh right in front of the beam entrance window is observed by means of dedicated radiation hard optics and suitable cameras. Starting from the initial goal of reliably detecting beam anomalies in a timely manner the scope of the system has been extended to serve as a standard device for beam monitoring and fine tuning of the settings of the proton beam transport lines. Over the course of the five years of continuous reliable operation of this unique system valuable experience has accumulated, which is employed for steady improvements of the device with respect to endurance in the radiation environment, calibration, maintenance, and price. A summary of the operational experience of VIMOS will be reported as well as steps taken towards further upgrades.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
An electron beam halo monitor has been developed in order to protect undulator permanent magnets against radiation damage for the X-ray free electron Laser facility at SPring-8 (XFEL/SPring-8). The halo monitor will be installed at the upstream of the undulator and detect the electron beam that might hit the undulator magnets. Diamond detector, which operates in photoconductive mode, is good candidate for electron beam sensor, because diamond has excellent physical properties, such as, high radiation hardness, high insulation resistance and sufficient heat resistance. Pulse-by-pulse measurement suppresses the background noise efficiently, especially in the facilities having extremely high intense beam but low repetition rate, such as XFELs. The linearity of output signal on injected beam has been demonstrated in the range of 103 to 107 electron/pulse. The feasibility check for this monitor was performed at the SPring-8 compact SASE source (SCSS) test accelerator for XFEL/SPring-8. We observed the unipolar pulse signal with the pulse length of 0.4 nsec FWHM. The beam profiles of the halo can be also measured by scanning the sensor of this monitor.
MPI-K, Heidelberg
The University of Liverpool, Liverpool
This contribution describes an optical fibre sensor based on the use of a silicon photomultiplier (SiPM) composed of an array of Single Photon Avalanche Detectors (SPADs). This sensor will be used for the detection and localization of particle losses in accelerators by exploiting the Cerenkov Effect in optical fibres. As compared to conventional vacuum photomultipliers, the SPAD array allows for maximizing the geometrical efficiency of Cerenkov photon detection. The array can be directly integrated into the fibre end while retaining the same quantum efficiency (20%) in the wavelength range of interest. The SiPM is intrinsically very fast due to its small depletion region and extremely short Geiger-type discharge, which is in the order of a few hundreds of picoseconds. Therefore, the combined use of optical fibres and SiPMs seems a promising option for a modern Cherenkov detector featuring subnanosecond timing, insensitive to magnetic fields, capable of single photon detection and allowing for the possibility of realization in the form of a smart structure. We present the layout and operating principle of the detector, its characteristics, and outline possible fields of application.
YerPhI, Yerevan
Diffusive Radiation (BR) is originated by the passage of charged particles through or near a randomly inhomogeneous medium. DR appears when the conditions for multiple scattering of pseudophotons are fulfilled in the medium. Such a situation can be realized when a charged particle slides over a rough metallic surface. One of the important properties of DR is that the emission maximum lies at large angles from particle velocity direction. Therefore it can be used for detection of beam touch to the accelerators vacuum chamber wall in case when generated photons will be observed on the opposite side of the vacuum chamber. Such a diagnostics can be especially useful for observation of storage ring beams halo. Corresponding proposal is presented in the paper.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
Fiber-based beam loss monitors offer the possibility to detect beam losses over long distances, with good position accuracy and sensitivity at a reasonable cost. For the undulator section of the SPring-8 X-FEL, radiation safety considerations set the desirable detection limit at 1 pC (corresponding to a 0.1% beam loss) over more than a hundred meter. While a theoretical approach offers some hints, the selection of the optimum fiber is not straightforward. Glass fibers of different diameter (100 to 600 μm), index profile (graded/stepped) and from three different makers were therefore characterized (signal strength, dispersion, attenuation) at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL. Beam tests (Fujikura SC400) showed that, at 250 MeV, the detection limit corresponding to a 10 mV signal is below 1 pC over 60 m and 3 pC over 120 m. The position accuracy was found to be better than 30 cm. Finally, the fiber lifetime has been estimated to be over 13000 h from dose measurements at the SCCS.
MPI-K, Heidelberg
The University of Liverpool, Liverpool
The majority of particles in a beam are located close to the beam axis, called the beam core. However, particles in the tail distribution of the transverse beam profile can never be completely avoided and are commonly referred to as beam halo. The light originating from or generated by the particle beam is often used for non- or least destructive beam profile measurements. Synchrotron radiation, optical transition, or diffraction radiation are examples of such measurements. The huge difference in particle density between the beam core and its halo, and therefore the huge intensity ratio of the emitted light is a major challenge in beam halo monitoring. In this contribution, results from test measurements using a flexible core masking technique are presented indicating way to overcome present limitations. This technique is well-known in e.g. astronomy, but since particle beams are not of constant shape in contrast to astronomical objects, a quickly adjustable mask generation process is required. The flexible core masking technique presented in this paper uses aμmirror array to generate a mask based on an automated algorithm.
CERN, Geneva
A novel radiation hardened current digitizer ASIC is in planning stage, aimed at the acquisition of the current signal from the ionization chambers employed in the Beam Loss Monitoring system in CERN accelerator chain. The purpose is to match and exceed the performances of the existing discrete component design, currently in operation in the Large Hadron Collider (LHC). The specifications include: a dynamic range of nine decades, defaulting to the 1pA-1mA range but adjustable by the user, ability to withstand a total integrated dose of at least 10 kGray in 20 years of operation and user selectable integrating windows, as low as 500ns. Moreover, the integrated circuit can be employed to digitize currents of both polarity with a minimum number of external components and without needing any configuration. The target technology is IBM 130 nm CMOS process. The specifications, the architecture choices and the reasons on which they're based upon are discussed in the paper.
CERN, Geneva
A discrete components design of a current digitizer based on the current-to-frequency converter (CFC) principle is currently under development at CERN. The design targets at rather high input current compared to similar designs, with a maximum equal to 200mA and a minimum of 1nA, as required by the ionization chamber that will be employed in the Proton Synchrotron and Booster accelerators as well as in the LINAC. It allows the acquisition of currents of both polarities without requiring any configuration and provides fractional counts through an ADC to increase the resolution. Several architectural choices are being considered for the front-end circuit, including charge balance integrators, dual-integrator input stages, integrators with switchable-capacitor, in both synchronous and asynchronous versions. The signal is processed by an FPGA and transmitted over a VME64x bus. Design, simulations and measurements are discussed in this article.
DESY, Hamburg
In this contribution we describe how Coherent Optical Transition Radiation can be used as a diagnostic tool for characterizing electron bunches in X-ray Free-electron lasers. The proposed method opens up new possibilities in the determination of ultra-short, ultra-relativistic electron bunch distributions.
FZD, Dresden
At the ELBE Free Electron Laser (FEL) at Forschungszentrum Dresden Rossendorf (FZD) electron bunches having lengths between 1 to 4 ps are generated. It is required to compress these electron bunches to lengths below 1 ps which necessitates diagnosis of the electron bunch parameters. We use a Martin-Puplett interferometer (MPI) which is a modification of the Michelson interferometer, where the beams are linearly polarized at specific orientations. It measures the autocorrelation function of the coherent transition radiation (CTR) from a view screen which is an optical replication of the electron bunch. The interferometer setup consists of various optical components like polarizers, beam splitter, mirrors and Golay cell detectors. In our measurement a wire grid was used as a polarizer and also as a beam splitter. A thorough understanding of the response of the optical components, as a function of the CTR wavelength range of our interest, is required for correct analysis of the measured signal. We have therefore simulated the response of the entire interferometer setup including the diffraction losses and the window transmission and compared the results to experimental measurements.
CERN, Geneva
University of Oslo, Oslo
The CTF3 provides high current (28A) high frequency (12GHz) electron beams, which are used to generate high power radiofrequency pulses at 12GHz by decelerating the electrons in resonant structures. A Test Beam Line (TBL) is currently being built in order to prove the efficiency and the reliability of the RF power production with the lowest level of particle losses. As the beam propagates along the line, its energy spread grows up to 60%. For instrumentation, this unusual characteristic implies the developments of new and innovative techniques. One of the most important tasks is to measure the beam energy spread with a fast time resolution. The detector must be able to detect the energy transient due to beam loading in the decelerating structures (nanosecond) but should also be capable to measure bunch to bunch fluctuations (12GHz). This paper presents the design of the spectrometer line detectors.
DESY, Hamburg
Uni HH, Hamburg
The need for timing and bunch-length monitors for free-electron lasers and other accelerators makes the electro-optic spectral decoding (EOSD) a promising diagnostic technique. Being non-destructive, it allows a single shot-measurement within the accelerator environment. In some cases, e.g. low charge or necessity to resolve time-structures below 20 fs, the bunch length is measured indirectly, using the spectrum of the coherent transition radiation (CTR). We present results of EOSD measurements on the CTR beam line at FLASH, using a chirped Ti:Sapphire oscillator pulse focused simultaneously with the THz radiation on a GaP crystal in vacuum. The CTR spectrum is in the range 200 GHz-100 THz and and the pulse energy in the focus is over 10 mJ. The measured narrow CTR temporal profiles in the order of 400 fs FWHM demonstrate, that the ultra short THz-pulses, emitted by the compressed electron bunches are transported through the 19 m long beam line without significant temporal broadening.
BNL, Upton, Long Island, New York
We have developed a photodiode-based X-ray beam-position monitor with high-spatial resolution for use on the future beamlines at NSLS-II. A ring array of 32 Si PIN photodiodes were fabricated for a photon sensor, and a newly-designed HERMES4 ASIC die was integrated into the data-acquisition system. A series of precision measurements for electrical characterization of the Si-photodiode sensor and the ASIC die demonstrated that the inherent noise is sufficiently below tolerance levels. Following up with a series of modeling efforts including geometrical optimization, we have built prototype detectors. In this paper, we present the development of the new state-of-the-art X-ray BPM and experimental measurements performed on the existing X12A beamline at NSLS.
NERS-UM, Ann Arbor, Michigan
Michigan Ion Beam Laboratory (MIBL) is equipped with a 1.7 MV tandem particle accelerator and a 400 KV ion implanter. Ion beams can be produced from a variety of ion sources and delivered to different beamlines. Precise beam profiling and current measurements are critical aspects of everyday activity in the laboratory and influence the success of each experiment. The paper will present the beam simulation software employed and the benefits and the shortcomings of the devices used at MIBL to precisely know all the parameters of the ion beams
PSI, Villigen
IAP Univ. Bern, Bern
Pulsed Yb fiber lasers emit at 1030 nm which provides a better phase matching in standard EO crystals (GaP, ZnTe) than Ti:Sa lasers (800nm). We present a mode locked ytterbium fiber laser which is phase locked to the RF. A subsequent fiber amplifier is used to boost the power and to broaden the spectrum due to nonlinear effects. The produced pulses have a spectral width of up to 100 nm and are therefore suitable for EO bunch length measurements, especially for spectral decoding. The laser delivers a chirped pulse of some ps, the fourier limited pulse duration of ~30 fs can be almost reached by an additional shaper setup with a spatial light modulator in the Fourier plane.
Diamond, Oxfordshire
JAI, Oxford
The operation of the Diamond storage ring with short electron bunches using ‘low alpha’ optics for generation of Coherent THz radiation and short X-ray pulses for time-resolved experiments is limited by the onset of microbunch instabilities. We have installed two ultra-fast (time response is about 250 ps) Schottky Barrier Diode Detectors sensitive to radiation within the 3.33-5 mm and 6-9 mm wavelength ranges. Bursts of synchrotron radiation at these wavelengths have been observed to appear periodically above certain thresholds of stored current per bunch. The fast response allows a bunch-by-bunch and turn-by-turn detection of the burst signal, which facilitates study of the bursts’ structure and evolution. In this paper we present our first results for various settings of alpha and also discuss future plans for the modification of a beam port to improve sensitivity of the system.
KEK, Tsukuba
RCNP, Osaka
We have continuously developed the Optical Transition Radiation (OTR) monitor with optics system based on the Newtonian telescope to measure a profile for a high intensity proton beamline. Now we installed the OTR monitors of production version on the J-PARC hadron beamline, and successfully observed a first OTR light. This led to the establishment of high S/N profile measurement with minimum beam disturbance. At this commissioning stage, a beam intensity is as small as 1.2 KW, but expected to increase up to 750 kW, so that maintenance work becomes important. To improve ease of maintenance, we plan to replace the focusing lens system with reflective mirror system with higher resistance to radiation. A result of beam profile measurement, an estimation of dependence of an OTR background on a beam loss, and a future plan for an upgrade of our optics system will be presented.
SINAP, Shanghai
KEK, Ibaraki
SR monitor for the measurements of beam profile, sizes, and bunch length has been designed and constructed at the Shanghai synchrotron radiation Facility (SSRF). A water-cooled beryllium mirror is installed to extract the visible SR. This beryllium mirror was designed via thermal analysis based on ANSYS. The extracted visible SR is relayed to dark room by three mirrors. The measurement system includes, imaging system, SR interferometers (SRI), streak camera and fast-gated camera etc are set in the dark room. Both the horizontal and the vertical beam sizes are monitored by SRI, and bunch length and temporal profile of the beam are measured by streak camera. The existed system suffers with dynamic problem for beam physics studies. The commissioning of synchrotron radiation monitor system has been performed in SSRF since December, 2007. The results obtained at SSRF will be presented.
DESY, Hamburg
IKP, Mainz
For the European XFEL with a maximum beam energy of 20 GeV and an average beam power of up to 300 kW it is planned to install beam profile monitors in the dump sections in order to control beam position and size. Usually OTR monitors are used for electron profile measurements. For intense beams however, thermal load in the screen material may result in resolution degradation and even screen damage. To overcome this problem the beam can be swept over the screen, but the strong OTR light emission directivity will reduce the optical system's collection efficiency. Therefore it is planned to use luminescent screens because of their robustness and isotropic light emission. While only little information is available about scintillator properties for applications with high energetic electrons, a test experiment has been performed at the 855 MeV beam of the Mainz Microtron MAMI in order to study light yield and robustness of different screen materials like Aluminum and Zirconium oxide under electron bombardment. The results will be compared to independent measurements from studies with heavy ion beams.
Uni HH, Hamburg
DESY, Hamburg
A synchrotron radiation monitor (SRM) based on a multi-anode photomultiplier tube (PMT) has been installed in the first magnetic bunch compressor chicane at the Free-electron LASer in Hamburg (FLASH). The synchrotron radiation emitted in the third dipole of the magnetic chicane is imaged by a telescope onto two anodes of the PMT. In this way the horizontal beam position of the electron bunches is recorded which corresponds to the beam energy as the beam position is governed by the beam energy in the dispersive section of the magnetic chicane. The fast PMT signals are digitized by analog -to-digital converters (ADC) which enables bunch-resolved beam energy measurement within the trains of the up to 800 bunches generated by the superconducting linear accelerator of FLASH. In this paper we describe the experimental setup of the SRM and present first commissioning results for various accelerator settings.
SLAC, Menlo Park, California
By scanning the electron beam energy in LCLS, the sharp K-edge absorption energies in nickel and yttrium were exploited to measure spectral features of x rays from a single undulator section. We show measurements obtained using a Ni foil, with beam energy tuned to scan the first harmonic across the K-edge, and similar measurements obtained using the yttrium component of a YAG screen, with the beam tuned to match the third harmonic. These spectral features allow the precise determination of the position of central ray, and provide some measure of the undulator K parameter. A refinement of this method should allow precise matching of the K parameters of multiple undulator sections after their installation in March 2009.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
DESY, Hamburg
Local beam losses and beam profiles at particle accelerators are determined by measuring the ionizing radiation outside the vacuum chamber. Four different fiber optic radiation sensor systems will be presented. Two are based on the increase of radiation-induced attenuation of (Ge+P)-doped multimode graded index fibers, whereas with the third system detects the Cerenkov light generated by relativistic electrons in radiation hard fibers. The used fiber is an undoped multimode step-index fiber with 300 um core diameter. Dosimetry at high dose levels uses the radiation induced Bragg wavelength shift of Fiber Bragg Gratings. The selection of a suitable fiber for the individual application is an important requirement and depends on the type, doping, used wavelength and annealing behavior. In addition, the dose range, dose rate and temperature must be considered. At six accelerators all systems are used for in-situ beam optimization and dose measurement. This paper summarizes the basic of this measurement technology and the experience at linear accelerators and at storage rings.
Uppsala University, Uppsala
Uni HH, Hamburg
DELTA, Dortmund
FYSIKUM, AlbaNova, Stockholm University, Stockholm
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
We present very promising recent results from the optical replica synthesizer experiment in FLASH where we manipulate ultrashort electron bunches in FLASH with a laser in order to stimulate them to emit a coherent light pulse with the temporal structure of the electron bunches and subsequently analyze the light pulses with laser diagnostic (FROG) methods.