RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
We present the design and performance of the beam diagnostic system of XFEL/SPring-8. The XFEL accelerator requires sub-um resolution beam position monitors (BPM), few-um resolution screen monitors, high-speed beam current monitors and a ten femtosecond resolution temporal structure measurement system. We designed an rf cavity BPM which has a resonant frequency of 4760 MHz and a position resolution of less than 1 um. For the screen monitor, thin stainless-steel foil (0.1 mm thick) is used to reduce beam divergence. In addition, a custom-made lens system having few-micron resolution was designed. For the beam measurement, we developed a differential current transformer (CT) with four ports, two are positive and the others are negative, to reduce common-mode noise. The rise time of the CT output pulse is 0.1 ns. To measure the temporal structure of a beam, we developed a C-band (5712 MHz) transverse deflecting cavity that has a disk-loaded backward traveling wave structure. The iris shape of the cavity is a race-track to separate x- and y-mode. This cavity can resolve a beam into femtosecond fragments. Thus, the beam diagnostic system satisfies the demands of the XFEL machine.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
In the XFEL project at SPring-8, the resolution of a beam position monitor (BPM) is required to be less than 1 um. Therefore, we developed an rf cavity BPM (RF-BPM) to achieve a precise position resolution. The RF-BPM has two cavities: one is a TM110 cavity for position detection and the other is a TM010 cavity for phase reference and charge normalization. The resonant frequency is 4760 MHz and the loaded Q factor is approximately 50 for both cavities. The designed performance of the RF-BPM cavity was confirmed by low-level rf measurement. The rf signal is detected by an IQ demodulator to obtain the intensity and the phase. Although the BPM signal is a mixture of a position signal and a slope signal, the IQ demodulator can easily distinguish them because the phases of these signals are 90 degrees different from each other. We developed a new circuit that has small errors: the intensity error is 1 % and the phase error is 0.5 degree. The RF-BPM system has been tested by using a 250 MeV electron beam at the SCSS test accelerator. We report results of confirmed RF-BPM performances; position resolution, xy coupling, linearity, dynamic range, beam arrival timing measurements etc.
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
SLAC, Menlo Park, California
CERN, Geneva
We present the performance and limitations of the SPS exponential coupler for transverse instability measurements with LHC type beam. Data were acquired in 2008 in the SPS in the time domain with a bandwidth of up to 2.5 GHz. The data were filtered to extract the time evolution of transverse oscillations within the less than 5ns long LHC type bunches. We describe the data filtering techniques and reveal the limitations of the pick-up due propagating modes.
CERN, Geneva
EPFL, Lausanne
LAL, Orsay
Within the framework of the second Joint Research Activity PHIN of the European CARE program, a new photo injector for CTF3 drive beam has been designed and installed by collaboration between LAL, CCLRC and CERN. The laser driven rf photo injectors are recent candidates for high-brightness, low-emittance electron sources. One of the main beam dynamics issues for a high brightness electron source is the optimization of beam envelope behavior in the presence of the space charge force in order to get low emittance. Beam based measurements have been made during the commissioning runs of the PHIN 2008 and 2009 including measurements of the emittance, using multi-slits technique. In this work the photo injector will be described and the first beam measurement results will be presented and compared with the PARMELA simulations.
DESY Zeuthen, Zeuthen
LAL, Orsay
Research activities at the Photo Injector Test facility at DESY, Zeuthen site, (PITZ) aim to develop and optimize high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. To demonstrate the XFEL operation, an electron bunch train containing 3250 pulses of 1 nC charge at 10 Hz repetition rate is required. The spectrometers and related equipments for studying the longitudinal phase space for such long pulse trains do not yet exist at PITZ. Design and construction of a new high energy dispersive arm (HEDA2) is currently in progress. Besides the requirement to handle long electron bunch trains, the HEDA2 setup is designed to allow high resolution measurements of momentum distribution up to 40 MeV/c, a longitudinal phase space measurement with slice momentum spread down to 1 keV/c and transverse slice emittance measurements at off crest booster phases. The status of the physics design and technical considerations of this dispersive section will be presented in this contribution.
CNAO Foundation, Milan
INFN/LNF, Frascati (Roma)
CERN, Geneva
The CNAO, the first Italian center for deep hadrontherapy, is presently in its final step of installation. It will deliver treatments with active scanning both with Proton and Carbon ion beams. Commissioning of the low energy injection lines has been successfully concluded in January 2009. CNAO beams are generated by two ECR sources which are both able to produce both particle species. The beam energy in the Low Energy Beam Transfer (LEBT) line is 8 keV/u. A compact and versatile tank containing a complete set of diagnostic tools has been intensively used for the line commissioning: in a length of 390mm it houses two wire scanners, for vertical and horizontal beam transverse profile, a Faraday Cup, for current measurement, and two vertical and horizontal plates for beam halo suppression , emittance measurements, beam collimation and particles selection. Using one tank devices, phase space distribution reconstruction can be quickly performed as well as synchronous profiles and intensity measurements. Commissioning results and measurements are presented.
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.
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)
The experimental setup implemented in the SPARC linac control system used to monitor the laser beam energy and to measure the beam charge by means of a Faraday Cup will be illustrated and discussed. The experimental setup makes use of National Instruments 2 GS/s 8-Bit digitizer board. This tool has been shown to be useful in order to monitor the laser beam energy stability and to evaluate the quantum efficiency of the cathode.
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.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
An electron Scanner has been commissioned to non-destructively measure the transverse profiles in the Spallation Neutron Source (SNS) Ring. The SNS Ring is designed to accumulate in the order of 1.6·1014 protons with a typical peak current of over 50 Amps. Because of this high intensity no other profile measuring devices such as wire scanners were installed. The electron scanner is based on measuring the deflection of 50-75kV electrons by the electric field of the proton beam. Two electron guns, one for each plane, with dipole correctors, quadrupoles and deflectors to shape the electron beam have been installed. This paper describes the system and the initial results.
DESY, Hamburg
The European XFEL is an X-ray free-electron-laser that is currently being built in Hamburg. It is organized as an international Project and will be a large scale user facility. Based on superconducting TESLA technology electron beams of high average power will be send to several undulator lines simultaneously to produce hard X-Rays with high average intensity and a peak brilliance by far superior to any 3rd generation light source. This paper will present the current status of the planning, the development and the prototyping process for this facility. It will cover as well as the BPM system, the other main diagnostic systems, like beam size measurements, charge, dark current and beam loss and protection systems.
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.
MPI-K, Heidelberg
The University of Liverpool, Liverpool
Growing interest in the development of low energy projectile beams, in particular heavy ions and antiprotons, calls for new beam instrumentation to be developed to match the strict requirements on ultra-high vacuum and low beam perturbation. When it comes to transverse profile monitoring, a convenient solution for simultaneous determination of both transverse profiles is found in a neutral supersonic gas-jet target shaped into a thin curtain and the two-dimensional imaging of the gas ions created by impacting projectiles. The resolution and vacuum efficiency of this monitor is directly linked to the characteristics of the gas-jet curtain. In this contribution we describe the design of a nozzle-skimmer system to be used for the creation of the jet curtain in the first prototype of such a monitor. Using numerical fluid dynamics simulations, we present the effects resulting directly from changes in the geometry of the nozzle-skimmer system on the characteristics of the jet curtain.
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.
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.
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
Electron cloud density in the Fermilab Main Injector was measured by observing microwave transmission along the vacuum tube. Presence of the electron cloud reduces the velocity of the microwave signal. Both frequency and time domain methods reveal relative cloud density and time evolution. The effect of beam time structure is clearly evident. The accelerator magnetic field effects the distribution of electrons making it difficult to estimate density.
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.
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.
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.
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.
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.
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
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
High-brightness electron bunches with low energy spread, small emittance and high peak currents are the basis for the operation of high-gain Free Electron Lasers (FELs). As only part of the longitudinally compressed bunches contributes to the lasing process, time-resolved measurements of the bunch parameters are essential for the optimisation and operation of the FEL. Transverse deflecting structures (TDS) have been proven to be powerful tools for time-resolved measurements. Operated in combination with a magnetic energy spectrometer, the measurement of the longitudinal phase space can be accomplished. Especially in case of ultra-short electron bunches with high peak currents for which a time resolution on the order of 10 fs would be desirable, both the TDS and magnetic energy spectrometer have intrinsic limitations on the attainable resolution. In this paper, we discuss the fundamental limitations on both the time and energy resolution, and how these quantities are connected.
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.
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.
DELTA, Dortmund
TU Dortmund University, Dortmund
Orbit stability at the 1.5 GeV electron storage ring DELTA is currently achieved via a global slow orbit feedback system at a data acquisition rate of 10 Hz. The system is based on analog Bergoz MX-BPMs and I-Tech Libera digital BPMs. In order to enhance the precision of the slow position measurement and in preparation for a global fast orbit feedback at a 10 kHz data acquisition rate we developed an FPGA based digital frontend for the MX-BPMs. The prototype module is taking orbit data from 4 Bergoz MX-BPMs, clocked to 40 kHz, at a rate of 10 kHz while averaging over 4 samples per clock cycle. The digitized data is distributed via the Diamond Communication Controller [*] formerly only available for Libera BPMs. Precision, fault tolerance and easy maintenance are the key aspects of this system. First operational tests in the storage ring showed that the system reveals the desired capabilities. The paper will give an overview on the layout of the FPGA-based system, will report on the results with beam and will show prospects for the further use at DELTA.
*I. S. Uzun et al., "Initial Design of the Fast Orbit Feedback System for Diamond Light Source", Proc. 10th ICALEPCS
DPNC, Genève
INFN-Napoli, Napoli
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum. The measurement of emittance is the subject of another contribution. This talk focuses on the particle identification devices, with three time-of-flight stations, Cherenkov detectors, a preshower device and a full absorption calorimeter. These devices ensure the purity of the muon sample separating off pions in the incoming beam upstream of the cooling cell and muon decay electrons downstream of the cooling cell. By April 2009 it is expected that the beam and first set of detectors will have been commissioned, and operation performance will be reported.
GSI, Darmstadt
ITEP, Moscow
A device for accessing the longitudinal phase space at low energy sections (1.4 MeV/u) of the GSI heavy ion LINAC is presented. In the course of the FAIR project optimizations of the existing facility at GSI are required. Integral information for the optimization process is extracted by the knowledge of the six dimensional phase space. Opposed to the transversal parameters it is particular difficult to access the longitudinal degree of freedom at low energies. The presented interceptive measurement is based on the coincident detection of single particles by means of two detectors: The first detector provides measurement of secondary electrons emitted from a thin Al-foil by the impinging ion beam. Secondly, after a drift of 80 cm beam particles are registered directly by a fast diamond detector. This contribution describes the measurement setup in detail including the principle of particle number attenuation by Rutherford scattering in the Ta foil. The achievements concerning the required timing resolution are presented and the investigations are accompanied by recently recorded data.
DESY, Hamburg
To exploit the short radiation pulses in pump-probe experiments at single-pass free-electron lasers (FELs), stabilization of the longitudinal profile and arrival time of the electron bunches is an essential prerequisite. Beam energy fluctuations, induced by the cavity field regulation in the accelerating modules, transform into an arrival time jitter in subsequent magnetic chicanes used for bunch compression due to the longitudinal dispersion. The development of beam based monitors is of particular importance for the validation and optimization of the cavity field regulation. In this paper we present bunch-resolved energy jitter measurements that have been recorded with a synchrotron radiation monitor at the Free-electron LASer in Hamburg (FLASH). The cavity field detectors of the accelerating module have been identified as the main source of the stochastical noise which corresponds to a beam energy jitter of 0.012%. The reduction of deterministic cavity field imperfections by applying an adaptive feedforward learning algorithm for the cavity field regulation is demonstrated.
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.
DESY Zeuthen, Zeuthen
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) develops and optimizes high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. A new multi-purpose dispersive section was designed* and installed to characterize the momentum distribution, the longitudinal phase space distribution and the transverse slice emittance of the electron bunch for an electron energy up to 40 MeV. The spectrometer consists of a 180 degree dipole magnet followed by a slit, a quadrupole magnet and two screen stations. One of the screen stations is equipped with an optical read-out for a streak camera to measure the longitudinal phase space distribution. The first measurement results and corresponding beam dynamics simulations of the longitudinal phase space and the momentum distributions will be reported in this contribution. The resolution of the system will be analysed and compared to the design expectations.
*Sergiy Khodyachykh et al.
"Design and Construction of the Multipurpose Dispersive Section at PITZ"
Proceedings of DIPAC 2007, Venice, Mestre, Italy 2007
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.
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.
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.
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.
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.
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.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
The RAL Front End Test Stand is under construction with the aim of demonstrating production of a high-quality, chopped 60 mA H- beam at 3 MeV and 50 pps. In addition to the accelerator development, novel laser-based diagnostics will be implemented. This paper reports on a device that will be able to measure multiple profiles of the beam density distribution in such a way that the full 2D density distribution can be reconstructed. The device is currently being commissioned. The status of the device is presented together with results of the commissioning and plans for future development.
CERN, Geneva
Linac4 is the first step of the future LHC injectors chain. This LINAC will accelerate H- ions from 45 keV to 160 MeV. During the commissioning phase of LINAC4, emittance measurements will be required at 45 keV, 3 MeV and 12 MeV. For this purpose a slit&grid system is currently being developed. The material and geometry of the wires and of the slits need to be optimized in order to reduce the effects of the energy deposition and maximize the signals: carbon, titanium steel and tungsten have been considered and studied. This document describes the results of the studies carried out during the design of the emittance meter and the first results during the commissioning.
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.
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.
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.
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.