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.
SOLEIL, Gif-sur-Yvette
Beam orbit stability is a crucial parameter for 3rd generation light sources in order to achieve their optimum performance. Sub-micron stability is now a common requirement for vertical beam position. To reach such performance, Global Orbit Feedback Systems are mandatory. This paper describes the different design approaches for Global Orbit Feedback Systems. A few machines can use a single set of strong correctors. Most machines have their strong corrector bandwidth limited by eddy currents in aluminium vacuum chamber, or power-supplies speed or digitization granularity. Then, a second set of fast correctors is required for high frequency correction. But Fast and Slow Orbit Feedback Systems cannot work together with a common frequency range, they fight each other. An earlier solution has been to separate fast and slow systems by a frequency deadband. This approach does not allow correcting efficiently the orbit shift due to the gap movements of the increasingly sophisticated insertion devices that are installed on new machines. The different solutions that have been recently implemented are reviewed.
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.
BNL, Upton, Long Island, New York
ANL, Argonne, Illinois
Sub-micron beam stability is a necessary performance requirement for the NSLS II light source, a substantial challenge testing the limits for presently available RF beam position monitoring methods. Direct performance comparisons between commercially available bpms and Advanced Photon Source in-house developed bpm were made at the APS Storage Ring. Noise floor, fill pattern dependence, and intensity dependence were investigated and correlated with photon diagnostics at the beam diagnostic beamline at APS sector 35. Key results will be presented.
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
LBNL, Berkeley, California
TU Darmstadt, Darmstadt
As conventional intercepting diagnostics will not withstand high intensity ion beams, Beam Induced Fluorescence (BIF) profile monitors constitute a pre-eminent alternative for online profile measurements. At present two BIF monitors are installed at the GSI UNILAC and several locations are planned for the FAIR high energy beam transport lines. For further optimizations accuracy issues like gas dynamics have to be investigated systematically. Especially the determination of focused beams in front of targets or beam intensities near the space charge limit rely on a careful selection of proper working gas transitions to keep profile distortions as low as possible. With an imaging spectrograph beam induced fluorescence spectra in the range of 300-800 nm were investigated. Wavelength-selective beam profiles were obtained for 5 MeV/u sulphur and tantalum beams in nitrogen, xenon, krypton, argon and helium gas at pressures below 10-3 mbar. In the calibrated BIF spectra the specific gas transitions were identified. The measurement results are compared with particle tracking simulations and discussed for typical applications at the present setup and the future FAIR facility.
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.
UniDo/IBS, Dortmund
iThemba LABS, Somerset West
FZJ, Jülich
DELTA, Dortmund
Scintillation is one of the outcomes of beam interaction with residual gas. This process is utilized for non-destructive beam profile monitoring. Test bench measurements at various gas compositions and pressures as well as ones with the circulating proton beam at COSY-Juelich were performed. This was done using a single large photocathode PMT to estimate the photon yield. A multichannel photomultiplier was used along with a lens system to monitor the ion beam profile. Experimental results are presented and the challenges of the approach are discussed.
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.
Uni HH, Hamburg
PSI, Villigen
DESY, Hamburg
A seeded free-electron laser operating in the soft X-ray (XUV) spectral range will be added to the SASE FEL facility FLASH. The seed beam will be generated by higher harmonics of a near infrared laser system. A dedicated transport system will guide the radiation into the electron accelerator environment. Within the seed undulator section compact diagnostic units have to be designed to control the transverse overlap of the photon and the electron beam. These units contain a BPM a wire scanner and an OTR screen for the electron diagnostic. A Ce:YAG screen and a MCP readout for the wire scanner are foreseen to measure the photon beam position.
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.
Diamond, Oxfordshire
During normal operation of synchrotron third generation light source like Diamond, the measurement of the electron bunch profile, of the order of 10~ps, is perfectly done with a streak camera. However, in 'low alpha' operation, where the momentum compaction factor is reduced in order to shorten the bunch length, the measurement becomes extremely close to the resolution of the camera. In such a case, performing a good measurement and extracting the real information requires a good knowledge of the impulse response of the streak camera. We present analysis and measurement of the contributions to the point spread function of the streak camera: the static point obtained by measuring a focussed beam without any sweep, which can be achieved at best around 5.5 pixels (0.7~ps with the fastest sweep), but also the chirp introduced by refractive optics and a large spectral beam, measured with a spectrograph at 26~fs/nm. Then we discuss short bunch measured in 'low alpha' operation and the agreement between measurements and expectation from theory.
PSI, Villigen
This contribution gives an overview of transverse sub-micron beam position measurement systems and techniques for 3rd and 4th generation light sources and collider projects. Topics discussed include mechanical, electrical and digital design aspects, environmental influences, machine operation and design considerations, as well as system- and beam-based measurement and calibration techniques.
Diamond, Oxfordshire
A relatively new development for synchrotron light sources is the concept of producing two independent X-ray beams in a single straight using two canted undulators. Two beams, separated by an angular divergence in the order of 1 mrad, proceed down the same front end before being separated into two experimental hutches. This creates a challenge for the position measurement of the two adjacent X-ray beams in the front end. Traditional four blade tungsten vane XBPMs are an established solution for accurate and reliable monitoring of the position of a single beam, so this approach has been developed to create an eight blade XBPM that is capable of resolving two beams independently. This paper presents first results from Diamond’s I04 and J04 IDs and illustrates the techniques used for position calibration and background subtraction.
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.
INFN-Roma, Roma
LAL, Orsay
INFN/LNF, Frascati (Roma)
roma3, Rome
INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)
The Frascati e+e- collider DAΦNE, running at sqrt(s) 1.02 GeV is testing the crabbed waist scheme, aiming to reach a large improvement of the specific and integrated luminosity of the accelerator. In order to have a reliable, fast and accurate measurement of the absolute luminosity a number of dedicated detectors have been designed, built, tested, calibrated and put into operation. In particular, three different monitors have been realized: a Bhabha calorimeter, realized with lead/scintillator tiles read by WLS fibers subdivided in 10+10 phi sectors, a Bhabha GEM tracker, of annular shape, with a 4x16 pads per side, covering the same angular region between 18 and 27 degrees in theta, and a Bremsstrahlung proportional counters realized by a couple of 4 PbWO4 crystals at small angle. Results from the 2008 run of DAΦNE are presented, together with the analysis tools for background subtraction and comparison with GEANT simulations.
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.
PSI, Villigen
In this paper, we describe four very different operating modes of the SwissFEL facility, the requirements of the challenging beam diagnostics and ultra-stable RF systems needed for two special operating modes with 10 pC, and the present status of developing beam diagnostics and RF systems for the PSI 250 MeV injector test facility, which is under construction.
ANL, Argonne, Illinois
This paper will give a general overview of active and passive stabilization systems, which are mainly required for future X-FEL and high energy linear colliders. Key physics requirements for beam stability for X-FELs and linear colliders will be introduced and resulting technical implications discussed. New and innovative approaches to the design and development of state-of-the-art linear accelerator components and stabilization systems will be reviewed, and recent results shown from selected prototypes and new machine installations.