CIEMAT, Madrid
CEA, Gif-sur-Yvette
The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology that will be used in the future IFMIF accelerator. Non-interceptive Beam Position Monitors pickups (BPMs) will be installed to measure the transverse beam position in the vacuum chamber in order to correct the dipolar and tilt errors. Depending on the location, the response of the BPMs must be optimized for a beam with an energy range from 5 up to 9 MeV and a current between 0.1 and 125 mA. Apart from the broadening of the electromagnetic field due to the low-beta beam, specific issues are affecting some of the BPMs: tiny space in the transport line between the RFQ and cryomodule (MEBT), cryogenic temperature inside the cryomodule, phase and energy measurement in the diagnostics plate, and debunching and big vacuum pipe aperture at the end of the high energy beam transport line. For this reason different types of BPMs are being designed for each location (MEBT, cryomodule, Diagnostics Plate and High Energy Beam Tranport Line). In this contribution, the design of each BPM will be presented, focusing on the electromagnetic response for high-current low-beta beams.
KEK, Ibaraki
A transverse bunch by bunch feedback system using iGp feedback processors has been tested at the KEK-PF. The system consists of a bunch position detection system using 1.5 GHz components of the beam (3 x fRF), iGp feedback signal processors, and a transverse feedback kicker with a high power amplifier. It shows sufficient performance to suppress instabilities completely up to a beam current of 450mA. Results of the mode analysis of the instabilities using the grow-damp function of the iGp are also shown.
U. Erlangen-Nurnberg LHFT, Erlangen
Siemens Med, Erlangen
For beam position monitoring purposes, particle-in-cell simulations were applied to investigate pickup button and electron beam spectrum characteristics. Results on this simulative approach are presented. Particularly, a comparison is made between simulation results from the PIC solver of CST’s PARTICLE STUDIO and experimental data gathered with a 6 MeV electron beam from a linear accelerator for medical purposes. The measurements were conducted under non-vacuum conditions. Good agreement between simulation and experimental data was achieved although non-negligible electron spread during air passage of the electron beam can be assumed.
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.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The commissioning of the ALBA Linac (Autumn 2008) required a careful measurement of the beam parameters. This paper describes the diagnostics devices installed at the ALBA Linac and our experience with them.
BESSY GmbH, Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
BunchView is a system for the direct measurement of the current from each bunch circulating in a storage ring based on the analysis of the RF-signals delivered by a set of striplines. This paper describes the development, achievements, operation, and results of this fast and accurate bunch current monitor built for the BESSY and MLS storage rings. Using a combination of a 14/16Bit ADC, a high-speed FIFO, ECL technique, and FPGAs, a real-time measurement of the fill-pattern with high accuracy and bunch-by-bunch resolution was achieved. The results are identical to the fill-pattern determined by time correlated single photon counting based on synchrotron radiation detected with an avalanche photo diode. BunchView is fully integrated into the EPICS control system. The data provided by the BunchView monitor give accurate bucket position in the ring and bunch current over a wide range of currents. The smallest measured single bunch current is less than 100nA. In the future the system will be used in the top-up mode of operation in order to inject beam into the emptiest buckets and thus keep the fill-pattern stable over longer periods of time.
CERN, Geneva
The LHC circulating beam current measurement is provided by 8 current transformers, i.e. 2 DC current transformers (DCCT) and 2 fast beam current transformers (FBCT) per ring. This paper presents the DCCT, designed and built at CERN, including the sensor, the electronics and the front-end instrumentation software. The more challenging requirements are the needed resolution, of the order of 1μA rms at 1s average, and the wide dynamic range of the circulating beam intensity from the pilot bunch (8μA) to the ultimate beam (860mA). Another demanding condition is the high level of reliability and availability requested for the operation and machine protection of this highly complex accelerator. The measurement of the first RF captured beam in ring 2 is close to meet the specifications in term of resolution (1.3μA rms at 1s average) and stability over a period of a few hours (drift less than 3μA). Finally elements intended to be installed in the near future are presented.
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.
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.
Fermilab, Batavia
Abstract The Fermilab Recycler ring employs an electron cooler to store and cool 8.9-GeV antiprotons. The cooler is based on a 4.3MV, 0.1A, DC electrostatic accelerator (Pelletron) for which current losses have to remain low (~10-5) in order to operate reliably. The Machine Protection System (MPS) has been designed to interrupt the beam in a matter of 1-2 μs when losses higher than a safe limit are detected, either in the accelerator itself or in the beam lines. This paper highlights the various diagnostics, electronics and logic that the MPS relies upon to successfully ensure that no damage be sustained to the cooler or the Recycler ring.
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.
GSI, Darmstadt
TUD, Darmstadt
Most timing systems used for particle accelerators send their time or reference signals via optical single mode fibres embedded in cables. An important question for the design of such systems is how fast the delay changes in the fibre optic cable take place, subject to the variation of the ambient air temperature. If this information is known, an appropriate method for delay compensation can be chosen, to enable a phase stabilised transmission of the timing signals. This is of interest particularly with regard to RF synchronisation applications. To characterise the velocity of the delay change, the delay behaviour after a sudden temperature change will be described. When trying to determine the step response, two problems occur. On the one hand, the material parameter of the coating, necessary for the calculation, is typically unknown. On the other hand, the measurement of the step response under realistic conditions is very laborious. Thus in this presentation it will be shown how the step response and, accordingly, the velocity of the delay change in a fibre optic cable can be calculated by means of theoretical considerations, utilizing the typical geometry of fibre optic cables.
PSI, Villigen
IAP Univ. Bern, Bern
The knowledge and control of electron bunch lengths is one of the key diagnostics in XFEL accelerators to reach the desired peak current in the electron beam. A compact electro-optical monitor was designed and build for bunch length measurements at the Swiss FEL. It is based on a mode locked ytterbium fiber laser probing the field-induced birefringence in an electro-optically active crystal (GaP) with a chirped laser pulse. The setup allows the direct time resolved single-shot measurement of the Coulomb field (THz-radiation) of the electron beam -and therefore the bunch length- with an accuracy as good as 200fs. Simulations of the signals expected at the SwissFEL and the results of first test at the SLS linac will be presented.
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.
CNAO Foundation, Milan
CERN, Geneva
The CNAO, the first Italian center for deep hadrontherapy, is presently in its final step of installation. Commissioning of the low energy injection lines has been successfully concluded in January 2009. The synchrotron injection chain consists of a 8 keV/u Low Energy Beam Transfer (LEBT) line, an RFQ to accelerate the beam up to 400 keV/u, a LINAC to reach the 7 Mev/u injection energy and a Medium Energy Beam Transfer line. At the end of the LEBT line, just upstream the RFQ, an electrostatic Chopper deviates the beam for about 100 micro-seconds every 2 seconds on the vacuum chamber, in order to shape the particles batch according to LINAC requirements and to minimize the beam lost at the RFQ entrance. The chamber section hit by the beam was electrically isolated from the adjacent vacuum chambers, allowing the reading of the LEBT beam current. The detector is based on the Faraday Cup working principle, but it results in a “not-interceptive” monitor that is able to measure, continuously, the source beam current ripples and stability without affecting the beam delivered to the synchrotron. The system is presently under commissioning with beam and preliminary results are presented.
DESY, Hamburg
The basic design for the machine protection system (MPS) for the light-source PETRA III is discussed. High synchrotron radiation can damage absorbers and vacuum chambers. Therefore the MPS identifies alarm conditions from different systems, including the BPM, temperature and vacuum systems and creates a dump command within 100us. For diagnostic purposes a post-mortem trigger is implemented and a first alarm detection is planned. The initial commissioning of the MPS with its alarm-delivering systems is described.
CEA, Gif-sur-Yvette
Within the framework of IFMIF-EVEDA project, a high-intensity deuteron beam (125 mA - 9 MeV) prototype accelerator will be built and tested at Rokkasho (Japan) in order to validate the future IFMIF accelerator. One of the most challenging diagnostics is the Beam Transverse Profile Monitor (BTPM), which has to be a non-interceptive device. Two R&D programs have been initiated: one based on residual gas fluorescence developed by Ciemat Madrid (see J. Carmona et al. contribution) and another one based on residual gas ionization developed at CEA Saclay. The principle of the last one is to measure the current induced by the ionization electrons, which drift under an electric field influence, towards several strips to get a one-dimension projection of the transverse beam profile. Preliminary results of a first prototype tested on the IPHI Saclay accelerator will be shown, as well as a new prototype design. In the new design several improvements have been carried out which will be tested soon with continuous and pulsed beam at higher energy.
HIT, Heidelberg
The ion cancer therapy facility HIT in Heidelberg is producing ions (H, He, C and O) from two ECR sources at an energy of 8 keV/u with different beam currents from about 80 μA up to 1.2 mA. Typical sizes for the beam in the LEBT range from are 5 40 mm. Matching the always slightly changing output from the ECR sources to the first accelerating structure, an RFQ, demands a periodical monitoring of the beam emittance. For that, a special pepper-pot measurement device is under design, whose most important parts are a damage-resistant pepper-pot mask and a vacuum-suitable scintillator material. The investigation of the material lifetime is done in the first step by computing the maximum intensity the target volume can stand without any radiation damage, shock and heating. A list of feasible materials will be discussed and results from SRIM calculations for them will be shown. A set-up for necessary material tests with beam will be presented.
iThemba LABS, Somerset West
INFN/LNL, Legnaro, Padova
Equipment for non-destructive, two-dimensional beam profile measurement has been developed for the 15 MV tandem accelerator at INFN, Legnaro and the K200 variable-energy, separated-sector cyclotron at iThemba Labs. Ions, produced by the interaction of the beam with residual gas, are accelerated in an electrostatic field towards microchannel plates (MCP) for signal amplification. With the first of the two prototypes that were built, ions are collected in an electric field between two parallel plates and after passing through an aperture in one of the plates, move through the electric field between two curved plates and bend through an angle of ninety degrees before reaching the MCP. The spread in ion energies provides the second position. In the second prototype two one-dimensional systems, rotated through ninety degrees with respect to each other, were installed close together. The measured beam profiles for both systems were compared with those of measurements with a nearby profile grid. Measurements were made on various beams and intensities between 10 and 10{00} nA. The beam position display with the MCP was calibrated to within 0.75 mm with the profile grid.
CERN, Geneva
Carbon fibres are commonly used as moving targets in Beam Wire Scanners. Because of their thermo mechanical properties they are very resistant to particle beams. Their strength deteriorates with time due to low-cycle thermal fatigue. In case of high intensity beams this process can accelerate and in extreme cases the fibre is damaged during a scan. In this work a model describing the fibre temperature, thermionic emission and sublimation is discussed. Results are compared with fibre damage test performed on the CERN SPS beam in November 2008. For the operation of Wire Scanners with high intensity beams damage threshold are predicted.
PSI, Villigen
A screen monitor containing OTR foils and scintillator crystals has been designed to measure the transverse profile of electron bunches in the PSI-XFEL. In conjunction with quadrupole magnets in FODO cells and a transverse deflecting structure, the screen monitors will be used to measure transverse and longitudinal phase space projections of the electron pulses in the 250 MeV Injector. Tomographic methods will be used to reconstruct the phase space distributions.
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.
MPI-K, Heidelberg
The cryogenic storage ring CSR is a 35 m circumference electrostatic ring, for molecular- and atomic physics experiments at MPI-K Heidelberg. It will operate at pressures down to 10-13 mbar and temperatures <10 K. The beam intensities will be in the range of 1 nA to 1 uA, particle energies are between 20 - 300 keV. An intensity measurement for coasting beams below 1 uA requires magnetic field detection devices, which are much more sensitive than existing DC beam transformers. The highest sensitivity is currently achieved with DC SQUID based cryogenic current comparators (CCCs). At GSI, a prototype of such a CCC was successfully tested in the mid 90’s, reaching a resolution of ~250 pA/Hz1/2. Recently a resolution of 40 pA/Hz1/2 could be achieved under laboratory conditions at Jena University, however, the CCC sensitivity in an accelerator environment depends strongly on efficient shielding and mechanical decoupling. We describe our work on adaptation and improvement of the CCC beam transformer for the CSR. Furthermore a concept for an ionisation profile monitor is discussed, which in addition to low beam intensities, has to cope with extremely low gas densities at 10-13 mbar.