KEK, Ibaraki
JAI, Egham, Surrey
OXFORDphysics, Oxford, Oxon
Optical Transition Radiation (OTR) appearing when a charged particle crosses a boundary between two media with different dielectric properties has widely been used as a tool for transverse profile measurements of charged particle beams in various facilities worldwide. The resolution of the conventional monitors is defined by so-called Point Spread Function (PSF) dimension - the source distribution generated by a single electron and projected by an optical system onto a screen. In our experiment we managed to create a system which can practically measure the PSF distribution. We demonstrated that is it is non-uniform. In this paper we represent the development of a novel sub-micrometer electron beam profile monitor based on the measurements of the PSF structure. The visibility of the structure is sensitive to micrometer electron beam dimensions. In this report we shall represent the recent experimental results. The future plans on the optimization of the monitor will also be presented.
FEL/Duke University, Durham, North Carolina
SLAC, Menlo Park, California
USTC/NSRL, Hefei, Anhui
Touschek lifetime of an electron beam in a storage ring depends on the beam polarization through the intrabeam scattering effect. Consequently, the electron beam polarization can be determined by comparing the measured Touschek lifetime of a polarized beam and an unpolarized beam. In this paper, we report a systematic experimental procedure to study the radiative polarization of a stored electron beam. Based upon this technique, we have successfully observed the polarization build-up of a 1.15 GeV electron beam in the Duke storage ring. Using the Touchek lifetime data, we are able to determine the equilibrium degree of the electron beam polarization and the time constant for the polarization build-up process.
BNL, Upton, Long Island, New York
University of Tuebingen, Tuebingen
Installation of electron lenses for the purpose of head-on beam-beam compensation is foreseen at RHIC. To optimize the relative alignment of the electron lens beam with the circulating proton (or ion) beam, photon detectors will be installed to measure the bremsstrahlung generated by momentum transfer from protons to electrons. We present the detector layout and simulations of the bremsstrahlung signal as function of beam offset and crossing angle.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
The Marie Curie Initial Training Network DITANET covers the development of advanced beam diagnostic methods for a wide range of existing or future accelerators, both for electrons and ions. The network brings together research centres like CERN or DESY, Universities, and private companies. DITANET currently has 27 partners from Europe and the USA and is committed to training young researchers in this field, performing cutting edge research in beam instrumentation, and exploiting synergies within this community. This contribution presents an overview of the research outcomes within the first two years of DITANET and summarizes the network's training activities.
on behalf of the DITANET Consortium.
Cockcroft Institute, Warrington, Cheshire
INFN/LNS, Catania
The University of Liverpool, Liverpool
Future atomic and nuclear physics experiments put challenging demands on the required beam instrumentation. Low energy (<1 MeV), low intensity (<107 pps) beams will require highly sensitive monitors. This is especially true for the Facility for Low-energy Antiproton and Ion Research (FLAIR) where antiproton beams will be decelerated down to 20 keV and as few as 5·105 particles per second will be slowly extracted for external experiments. In order to investigate the limits of scintillating screens for beam profile monitoring in the low energy, low intensity regime a structured analysis of several screen materials, including CsI:Tl, YAG:Ce and scintillating fibre optic plate (SFOP), has been done under different irradiation conditions with keV proton beams. This contribution will present the experimental setup and summarize the results of this study.
YerPhI, Yerevan
The Vibrating Wire Monitor (VWM) with aperture 20 mm was developed for scan of electron beam with large transversal sizes. Test experiments with VWM placed in air were done on the 20 MeV electron beam of Yerevan Synchrotron Injector with 4-7 uA at outlet. A new design of VWM is proposed for scan of the beam with even greater transversal sizes.
Monash University, Faculty of Science, Victoria
ASCo, Clayton, Victoria
A new arrangement for the synchrotron radiation interferometer was proposed - as far as is known, it is unique in the world. The Young's-type interferometer is composed of two independent and optically identical paths, each with a single slit on a motorised translating stage. These two single slit patterns are interfered to produce a double slit diffraction pattern. This arrangement permits rapid scanning of the profile of fringe visibility as a function of slit separation. The interferometer was used on two beamlines at the Australian Synchrotron, the optical diagnostic and infrared beamlines. The interferometer was used to measure the coherence of the photon beam created by the electron beam source, for normal and low emittance couplings. A large change in fringe visibility was observed, proving the experimental arrangement. The interferometer was validated in the measurement of the width of a hard-edged single slit, akin to Thompson and Wolf's diffractometer. Optical simulations and measurements inform proposed modifications to the optical diagnostic beamline, so as to implement the interferometer as a regular diagnostic tool.
ASCo, Clayton, Victoria
Thirty two Bergoz Beam Position Monitors are located in the Australian Synchrotron booster ring. They currently suffer from a poor signal-to-noise ratio and a low sample rate data acquisition (DAQ) system, provided by a portable DAQ device. This architecture is being upgraded to offer better performance. Phase matched low attenuation cables are being pulled and readout electronics will be located in two sites to reduce cable length. Data acquisition will be upgraded using a high accuracy PCI DAQ board. The board's trigger, originally delivered by a Delay Generator, will be generated by an Event Receiver output following our recent upgrade of the timing system. The new Linux driver will be EPICS-based, for consistency with our control system.
TRIUMF, Vancouver
The ISAC accelerators presently deliver various stable and radioactive CW heavy ion beams to experiments with energies ranging from 2keV/u up to about 4.5 MeV/u ( for A/q = 6 ). Beam intensities also vary enormously being as low as a few hundred ions per second for certain radioactive ion species and as high as 100 enA for stable and pilot beams. Monitoring of beams with currents of less than ~0.5 epA requires a dedicated diagnostics instrumentation which typically makes use of radiation hard single particle detectors. Several such devices have been built and are under development at TRIUMF. Electron multiplier based SEEM monitors, solid state and scintillator detectors with a count rate capability in excess of 106 pps are employed. Device controls are integrated into the EPICS environment and provide standardized, simple and transparent operation. Details of the design, tests and beam measurements will be present.
HIP, University of Helsinki
Comenius University in Bratislava, Faculty of Mathematics Physics and Informatics, Bratislava
Helsinki University, Department of Physics, University of Helsinki
The Super-FRS is a superconducting fragment separator that will be built as part of the FAIR facility. For the slow-extraction part of the beam diagnostics system a total of 32 detectors are needed for beam monitoring and for tracking and characterization of the produced ions. Since GEM-TPC detectors can perform over wide dynamic range without disturbing the beam, they are suitable for this kind of in-beam detection. We have studied the performance of a prototype GEM-TPC. The current status of the prototype detector and the measurement results are shown.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
With a 7T wiggler in operation any attempts to detect the resonant depolarization of the electron spins were unsuccessful at BESSY II. This was attributed to the severely reduced final degree of spin polarization in the alternating fields of the strong wiggler which on the other hand nearly double the radiation loss per turn. The key to a clear detection of the depolarization were the improvement of the sensitivity of the polarimeter based on the spin dependent Touschek scattering cross section and the more effective and thus full depolarization of the beam. In the paper the steps taken will be presented in detail. With these improvements in place the high precision energy determination of the stored beam can be performed once again in parallel to the normal user operation and without any noticeable perturbations to the beam.
PTB, Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
For the operation of the Metrology Light Source (MLS)*, the electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), as a primary radiation source standard all storage ring parameters have to be known absolutely. For the measurement of the electron beam size and the monitoring of the stability of the orbit location a new imaging system has been set up, that operates at very different intensity levels covering more than 11 decades, given by the variation of the electron beam current. The system uses a commercial zoom lens for the achromatic optical imaging of the electron beam source point onto two different camera systems. One camera system is for life-imaging of the electron beam at electron beam currents from 200 mA down to some μA. The second system is a cooled CCD-camera that allows imaging of the electron beam size and location at very low currents, down to only one stored electron.
* R. Klein et al., Phys. Rev. ST-AB 11, 110701 (2008).
ELSA, Bonn
At the electron stretcher accelerator ELSA of Bonn University, an external beam of either unpolarized or polarized electrons is supplied to hadron physics experiments. In order to correct dynamic effects caused by eddy currents induced during the fast energy ramp, the transversal tunes have to be measured in situ with high precision. These measurements are based on the excitation of coherent betatron oscillations generated by a pulsed kicker magnet. Horizontal oscillations were excited using one of the injection kicker magnets. Since its installation in 2009 a newly designed kicker magnet enables measurements in the vertical plane as well. Betatron oscillation frequencies were derived from a fast Fourier transform of the demodulated BPM signals, showing a well pronounced peak at the tune frequency. Using this technique, tune shifts were measured and corrected successfully on the fast energy ramp. Measurement and correction of coherent synchrotron oscillations are feasible as well, utilizing a quite similar technique. Coherent synchrotron oscillations are excited by a phase jump of the acceleration voltage using an electrical phase shifter in the reference RF signal path.
U. Erlangen-Nurnberg LHFT, Erlangen
Siemens Med, Erlangen
The usability of conventional BPM topologies in compact linear accelerators used for medical and industrial applications is very limited due to tight space restrictions in such systems. To overcome these limitations, a different approach is introduced which is based on integrating the pickups into low-field regions of the accelerating structure and evaluating higher beam harmonics. Applications based on this approach will require RF frontends in frequency ranges beyond those covered by BPM dedicated hardware which is currently commercially available. Therefore, a demonstrator setup is presented which is capable of investigating suitable RF frontends for the proposed method. The demonstrator uses capacitive pickups of the button type for displacement sensing and allows for control of the beam position with the help of feedback steering coils which are typically used for compact linacs. Representative sensitivity measurement results based on the evaluation of the 2nd S-Band beam harmonic are also presented in this paper.
DESY, Hamburg
The problem of errors, arising due to finite BPM resolution in the reconstructed orbit parameters, is one of the standard problems of the accelerator physics. Even so for the case of uncoupled motion the covariance matrix of reconstruction errors can be calculated "by hand", the usage of the obtained solution, as a tool for designing of a "good measurement system", is not straightforward. A better understanding of this problem is still desirable. We make a step in this direction by introducing dynamics into this problem, which seems to be static. We consider a virtual beam obtained as a result of the application of a reconstruction procedure to ‘‘all possible values'' of BPM reading errors. This beam propagates along the beam line according to the same rules as any real beam and has all beam dynamical characteristics, such as emittances, dispersions, betatron functions, and all these values describe the properties of the BPM measurement system. As an application we formulate requirements for the BPM measurement system of high-energy intra-bunch-train feedback system of the European XFEL Facility in terms of the introduced concepts of error emittance and error Twiss parameters.
DESY, Hamburg
IKP, Mainz
Luminescent screens are widely used for particle beam diagnostics, especially in transverse profile measurements at hadron machines and low energy electron machines where the intensity of optical transition radiation (OTR) is rather low. The experience from modern linac based light sources showed that OTR diagnostics might fail even for high energetic electron beams because of coherence effects in the OTR emission process. An alternative way to overcome this limitation is to use luminescent screens, especially inorganic scintillators. However, there is only little information about scintillator properties for applications with high energetic electrons. Therefore a test experiment has been performed at the 855 MeV beam of the Mainz Microtron MAMI (University of Mainz, Germany) in order to study the spatial resolution. The results of this experiment will be presented and discussed in view of scintillator material properties and observation geometry.
DESY, Hamburg
BNL, Upton, Long Island, New York
TUD, Dresden
DESY Zeuthen, Zeuthen
PETRA III is the new 3rd generation hard X-ray synchrotron light source at DESY, operating at a beam energy of 6 GeV. Machine commissioning began in April 2009 and user operation starts in 2010. In order to achieve a high brilliance, damping wigglers with a total length of 80 m are installed to reduce the horizontal emittance down to an extremely low value of 1 nm rad. For a precise emittance online control, a dedicated diagnostics beamline was built up to image the beam profile with synchrotron radiation from a bending magnet in the X-ray region. The beamline is equipped with two interchangeable X-ray optical systems, a pinhole optic for standard operation and a high resolution compound refractive lens optic. In addition, the synchrotron radiation angular distribution can be exploited at high photon energies. In this presentation, first experience with the system will be reported.
DESY, Hamburg
Università di Roma I La Sapienza, Roma
The control and stabilization of RF systems for accelerators has a considerable importance. In case of high-gain free-electron lasers (FEL) with magnetic bunch compressors, the RF phases determine the attainable bunch peak current, which is a relevant parameter for driving the FEL process. In order to measure the bunch peak current in a simple and fast but indirect way, both bunch compressors at FLASH are equipped with compression monitors (BCM) based on pyroelectrical detectors and diffraction radiators (CDR). They provide substantial information to tune the bunch compression and are used for beam-based feedback to stabilize RF phases. This monitor system becomes more important and more challenging after the installation of a third-harmonic RF system for longitudinal phase space linearization in front of the first bunch compressor. In this paper, we describe the hardware upgrade of the bunch compression monitor and show the expected performance by simulations of the CDR source and the radiation transport optics. Particle tracking simulations are used for generation of the simulated BCM-signal for various compression schemes. Comparison with experimental data will be presented.
Uni HH, Hamburg
PSI, Villigen
Westdeutsches Protonentherapiezentrum, Essen
DESY, Hamburg
sFLASH is a seeded FEL experiment at DESY, which uses a 38nm high harmonic gain (HHG)-based XUV-beam laser in tandem with FLASH electron bunches at the entrance of a 10m variable-gap undulator. The temporal overlap between the electron and HHG beams is critical to the seeding process. Use of a 3rd harmonic accelerating module provides a high current electron beam (at the kA level) with ~ 600fs FWHM bunch duration. The length of the HHG laser pulse will be ~30fs FWHM. The desired overlap is achieved in steps. First is the synchronization of the HHG drive laser (Ti: Sapphire, 800nm) and the incoherent spontaneous radiation from an upstream undulator. Next, the IFEL-modulated electron bunch will pass through a dispersive section, producing a density modulation in the beam. This in turn yields emission of coherent radiation from a downstream undulator or transition radiation screen when the longitudinal overlap of the two beams is achieved. The coherently enhanced light emitted will be then spectrally analyzed. The experimental layout, simulation results of generation and transport of both light pulses, and preliminary measurements are presented.
MPI-K, Heidelberg
Kyoto ICR, Uji, Kyoto
A cryogenic storage ring (CSR) is under construction at MPI für Kernphysik, which will be a unique facility for low velocity phase space cooled ion beams. Among other experiments the cooling and storage of molecular ions in there rotational ground state is planed. To meet this requirement the ring must provide a vacuum with a residual gas density below 10000 molecules/cm3, which will be achieved by cooling the vacuum chamber of the ion beam to 2-10 K. The projected stored beam current will be in the range of 1 nA - 1 μA. The resulting low signal strengths on the beam position pickups, current monitors and Schottky monitor put strong demands on these diagnostics tools. The very low residual gas density of the CSR does not allow using a conventional residual gas monitor to measure the profile of the stored ion beam. Other methods were investigated to measure the profile of a stored ion beam. In the paper an overview of the CSR diagnostics tool and diagnostics procedures will be given.
FZJ, Jülich
UniDo/IBS, Dortmund
GSI, Darmstadt
JINR, Dubna, Moscow Region
To study electron cooling in a synchrotron nondestructive methods only are suitable. The ionization profile monitor (IPM) delivers real-time data in both transverse planes allowing detailed analysis of beam profile evolution in COSY. First attempts to use scintillation of residual gas (SPM) to measure beam profiles were very promising. Beam diagnostics based on recombination is usually used to optimize electron cooling of protons (H0-diagnostics). However, it is not available when cooling antiprotons. So the IPM and possibly the SPM are vital for electron cooling optimization in the HESR ring. The new beam instrumentation at COSY is introduced and its relevance for the new 2 MeV electron cooler project and the HESR are discussed. Results of beam studies performed during electron cooling beam times at COSY are presented.
KIT, Karlsruhe
A new 90 kV e-gun had been installed at the 50 MeV microtron at ANKA. The emittance of the gun has been measured in long pulse mode (1 us, 200 mA) with a pepper-pot, resulting in 5 u.rad RMS normalised emittance. The single pulse width is less than 1 ns, resulting in a bunch purity in the storage ring of better 0.5 %. The old timing system for gun and injection elements based on 4 Stanford delay generator has now been replaced by an event driven system from Micro-Research Finland (MRF). This consists of one event generator and one event receiver. Visualisation and programming is achieved with PVSS from ETM Austria. The e-gun trigger can be adjusted in 10 ps steps. The entire system is phase locked to the 499.69 MHz RF signal.
IKP, Mainz
During the last three years at the 1.5 GeV Harmonic Double Sided Microtron (HDSM)* of MAMI a lot of improvements concerning the longitudinal operation of the accelerator were tested and installed. To monitor the rf power dissipated in the accelerating sections, their cooling water flow and its temperature rise are now continuously logged. Phase calibration measurements of the linacs and the rf-monitors revealed nonlinearities of the high precision step-motor driven waveguide phase shifters. They were recalibrated to deliver precise absolute values. Thereby it is now possible to measure not only the first turn's phase very exactly, but also determine the linac's rf-amplitude within an error of less than 5%, using the well known longitudinal dispersion of the bending system. These results are compared to the thermal load measurements. For parity violating experiments the beam energy has to be stabilised to some ppm. A dedicated system measuring the time-of-flight through a bending magnet is now used in routine operation and controls the output energy via the proper linac phases.
* K.-H. Kaiser et al., NIM A 593 (2008) 159 - 170, doi:10.1016/j.nima.2008.05.018
IHEP Beijing, Beijing
IHEP Beiing, Beijing
The analytic solution of a microchannel target for a uniform beam is given in one-dimentional model. The target surface temperature, maximum acceptable power density, and the function of various geometric parameter are deduced. The solution is modified for an axi-symmetric Gaussian beam. The analytic results are coincident with the numerical solution. A slit target used to measure beam energy spectrum for a beam with energy of 3.54MeV, average beam power of 36kW is developed.
ELETTRA, Basovizza
DEEI, Trieste
FERMI@Elettra is a soft X-ray fourth generation light source under construction at the ELETTRA laboratory. To characterize the beam phase space by means of measurements of the bunch length and of the transverse slice emittance two deflecting cavities will be positioned at two points in the linac. One will be placed at 250 MeV (low energy), after the first bunch compressor (BC1); the second at 1.2 GeV (high energy), just before the FEL process starts. The Low-Energy RF Deflector consists in a 5 cells, standing wave, normal conducting, RF copper cavity. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. In this paper we discuss and report on results of electromagnetic, thermal, and structural analysis.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
At the LNF of INFN an IR array detector with a ns response time has been built and assembled in order to collect the IR image of the e-/e+ sources at DAΦNE. Such detector is made by 32 bilinear pixels with a pixel size of 50x50 μm2 and a response time of 1 ns. The device with its electronic board has been assembled for the installation on the e+ ring of DAΦNE in the framework of an experiment funded by the INFN Vth Committee dedicated to beam diagnostics. A preliminary characterization of few pixels of the array and of the electronics has been carried out at the IR beamline SINBAD at DAΦNE. In particular the detection of the IR source of the e- beam has been observed using four pixels of the array acquiring signals simultaneously with a 4 channels scope at 1GHz and at 4 Gsamples/s. The acquisition of 4 pixels allowed monitoring in real time differences in the bunch signals in the vertical direction. Preliminary analysis of data is presented and discussed. In particular we will outline how the differences in the signals can be correlated to small displacements of the source after the bunch refilling and during a complete shift of DAΦNE and before the refilling of electrons.
INFN/LNF, Frascati (Roma)
INFN-Roma II, Roma
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
Ultra-short electron bunch production is attractive for a large number of applications ranging from short wavelength free electron lasers (FEL), THz radiation production, linear colliders and plasma wake field accelerators. SPARC is a test facility able to accelerate high brightness beam from RF guns up to 150 MeV allowing a wide range of beam physics experiments. Those experiments require detailed beam measurements and careful data analysis. In this paper we discuss the techniques currently used in our machine; by combining quadrupoles, RF deflector, spectrometer dipole and reliable data analysis codes, we manage to characterize the 6D phase space and the beam slice properties. We focus on the ongoing studies on the emittance compensation in the velocity bunching regime.
NIRS, Chiba-shi
For the beam profile diagnosis of heavy ion cancer therapy in HIMAC (Heavy Ion Medical Accelerator in Chiba), a MWPC (Multi-Wire Proportional Counter) detector is employed as a beam profile monitor. Due to the high rate beams (~ 108 pps), a gain reduction of output signals, which is caused by space charge effects, have been observed in the scanning beam experiments at HIMAC. In order to reduce the gain reduction by optimizing the parameters of MWPCs including anode radius, and distance between electrodes, a numerical calculation code was developed by employing two-dimensional fluid model. In order to understand the relations between the gain reduction and space charge distribution, the temporal evolution of the ion/electron distribution were calculated for several hundredμseconds, which is significantly longer than the time period required for ions to travel between the electrodes. The output signal was also evaluated by the current flux into the anode and compared with that obtained by the beam experiment at HIMAC. The dependence of the gain reduction on the MWPC parameters was analyzed from these calculation results.
JAEA/TARRI, Gunma-ken
It is important to match the injection beam emittance to the acceptance of an accelerator for high beam transmission A system to evaluate transverse beam matching has been developed in the JAEA AVF cyclotron facility. In this presentation, concepts of an apparatus for transverse acceptance measurement will be reported. The apparatus consists of a phase-space collimator in the injection beam line and beam current monitor after the cyclotron. The collimator consists of two pairs of position defining slits and angle defining slits to inject an arbitrarily small portion of transverse phase-space into the cyclotron. Measurement of the acceptance is made by testing every portion in the whole phase-space, which should large enough to cover the acceptance. The acceptance can be estimated from the sum of the portions of the beam which passes through the system.
HU/AdSM, Higashi-Hiroshima
The University of Tokyo, Institute of Physics, Tokyo
MPQ, Garching, Munich
RIKEN, Wako, Saitama
Hiroshima University, Graduate School of Advanced Sciences of Matter, Higashi-Hiroshima
Tokyo University of Science, Tokyo
In Antiproton Decelerator (AD) at CERN, unique low energy antiproton beams of 5.6 MeV have been delivered for physics experiments. Furthermore, the RFQ decelerator (RFQD) dedicated for Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) collaboration enables the use of 100 keV pulsed antiproton beams for experiments. What is more, Mono-energetic Ultra Slow Antiproton Source for High-precision Investigations (MUSASHI) in ASACUSA can produce antiproton beams with the energy of 100 ~ 1000 eV. Since the successful extraction of 250 eV antiproton beams reported in 2005, continuous improvements on beam quality and equipments have been conducted. Here, the basic properties of a tank circuit attached to MUSASHI trap are reported. Signals from a tank circuit provide information on the trapped antiprotons, as Shottky signals do for high energy beams in accelerators. In fact, it is known that this kind of trap-based beams are physically equivalent with those in a FODO lattice. Monitoring the tank circuit signals will be useful for on-line handling of the low energy antiproton beams from MUSASHI.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
Energy Recovery Linac (ERL) as synchrotron light source is planned to construct in KEK. Before the construction of full-set of ERL, compact ERL to study the accelerator technologies will be constructed. For the injector, a high voltage photoemission gun with DC operation and measurement systems for the low emittance beam will be developed. In order to observe bunch length and longitudinal beam profile, we have designed a single-cell deflecting cavity with 2.6 GHz dipole mode. We describe the optimization of the cavity, mechanical design and the measurements results with simulation.
RIKEN/SPring-8, Hyogo
The x-ray FEL facility at SPring-8 produces a very short-bunch beam by using bunch compressors (BC) consisting of magnetic chicanes. Since the bunch compression ratio is strongly depends on the beam energy and the energy chirp, we need to monitor the energy from the beam position at the dispersive part of the BC with a 0.1% resolution. However, a beam profile at the dispersive part is horizontally flat and wide, maximally 50 mm, due to the large energy chirp of the beam. Therefore, we designed a multi-stripline beam position monitor. This monitor has a flat rectangular duct with a 70 mm width and a 10 mm height. Six stripline electrodes at individual intervals of 10 mm are equipped on each of the top and the bottom surface. Due to the small height of the monitor, each electrode is sensitive to the electron position within 10 mm in the horizontal. Therefore, the monitor provides a rough charge profile and the beam position which is calculated from the gravity center of the signals. We prepared a prototype of the monitor and tested it at the SCSS test accelerator. We confirmed that the position sensitivity was better than 0.1 mm, which corresponds to 0.1 % energy resolution.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
We report the design, performance, and installation of the beam diagnostic system of XFEL/SPring-8. The electron beam bunches of an XFEL accelerator are compressed from 1 ns to 30 fs by bunch compressors without emittance growth and peak-current fluctuation which directly cause SASE fluctuation. To maintain the stable bunch compression process, the accelerator requires rf caivty beam position monitors (BPM) with 100 nm resolution, OTR screen monitors (SCM) with a few micro-meter resolution, fast beam current monitors (CT) and temporal structure measurement systems with resolution under picosecond. The performance of the developed monitor instruments, such as the BPM, the SCM, and the CT, was tested at the SCSS test accelerator and satisfied with the requirements. To measure the temporal structure of the electron bunch, three type measurement systems, which are a streak camera, an EO sampling measurement, and a transverse deflecting cavity with a resolution of few-tens femtosecond, are being prepared. The streak camera and EO sampling shows the resolution of sub-picosecond. The installation of these beam diagnostic systems is going on smoothly.
JASRI/SPring-8, Hyogo-ken
The signal processing electronics of the SPring-8 Storage Ring BPM were replaced during the summer shutdown of 2006, and put into operation. However, a large filling pattern dependence was observed. The cause was attributed to the nonlinear response of the diodes to large pulse signals. The diode were attached in front of the RF switches for protection from the electrostatic discharge damages on the switch IC. We took a countermeasure for the filling pattern dependence by reducing the pulse height with a band pass filter (BPF) in front of each channel. The BPF were attached and put into the operation from November 2008. The effect of the BPF was evaluated using the beam with changing the filling patterns and repeating the position measurements. The differences of the measured position data across the filling pattern change were found to be within 10μmeters, which was the same amount of the orbit drift during the filling pattern change.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
We are developing a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor based on Electro-Optical (EO) sampling with a manner of spectral decoding for XFEL/SPring-8. For fine beam tuning, 3D-BCD is often required to measure in real-time. The main function of this bunch monitor can be divided into longitudinal and transverse detection. For the transverse detection, eight EO-crystals surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape passes thorough the crystal. The polarization axis of the probe laser should be radially distributed as well as the Coulomb field of the electron bunches. Since the signal intensity encoded at each crystal depends on the strength of the Coulomb field at each point, we can detect the transverse BCD. In the longitudinal detection, we utilize a broadband square spectrum (> 400 nm at 800 nm of a central wavelength) so that the temporal resolution is < 30 fs if the pulse width of probe laser is 500 fs. In order to achieve 30-fs temporal resolution, we use an organic EO material, DAST crystal, which is transparent up to 30 THz. We report the first experimental results of this 3D-BCD monitor.
KEK, Ibaraki
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
UH, Honolulu, HI
An x-ray beam size monitor based on coded aperture imaging* has been developed at CesrTA, for the purpose of making bunch-by-bunch, turn-by-turn measurements of low emittance beams. Using low-emittance beam (~44 pm, or 16 microns at the x-ray source point) we have been able to make detailed comparisons between the measured mask response and that predicted by theory, validating our simulations of the mask response. In turn, we demonstrate the ability to measure both integrated and single-bunch turn-by-turn beam sizes and positions for monitoring the progress of the low-emittance tuning of the machine, and for electron-cloud instability-related beam dynamics studies.
* J.W. Flanagan et al., EPAC08, 1029 (2008).
KEK, Ibaraki
Crab cavities were installed in the KEKB rings in order to increase the luminosity. We measured the tilt of the bunches in the x-z plane using streak cameras. In a previous report*, the measured tilt in the HER was 2 times smaller than the expected crabbing angle, while the LER measurement was consistent with that expected. After the streak camera's vertical sweep speed was calibrated, the results were consistent with the expected crabbing angle in both rings.
* H. Ikeda et al., PAC07, 4018.
KEK, Ibaraki
Some of the improvement were done for an SR interferometer with the Herschelian reflective optics*. Previously, the measured vertical beam size was limited to around 5μm with a double slit separation of 40mm and wavelength of 400nm at the ATF damping ring. Double slit separation was mainly limited to the effective aperture of the optical path between the source point and interferometer. This time, we re-aligned the optical path, and as a result, the effective aperture was increased. Using this re-alignment we can have a double slit separation of up to 60mm. To reduce air turbulence, the optical path was covered with a tight air duct. After these improvements were made, we succeeded in measuring a vertical beam size of 3.4μm with double slit separation of 60mm and wavelength of 550nm, which corresponds to 5pm of the vertical emittance assuming 3m of the beta function.
* T. Naito et. al. "Very Small Beam Size Measurement by Reflective SR Interferometer at KEK-ATF", Proc. of EPAC06, pp2772-2274.
KEK, Ibaraki
Sudden decrease in the beam lifetime is sometimes observed in many electron storage rings. Such an event has been commonly attributed to dust trapping, but its mechanism has not been entirely elucidated yet. Our recent research at PF-AR has shown that trapped dust with certain conditions can be visually observed by video cameras, and the recorded movies revealed that the trapped dust moved longitudinally. In addition, the light emission from the dust indicated that its temperature reached 1000 K or more. Thus, direct observation of trapped dust has been proved to be an effective way to investigate the dust trapping mechanism. We have carried on this research with advanced cameras, such as high-sensitivity or high-speed cameras, and the results will be presented.
KEK, Ibaraki
MELCO SC, Tsukuba
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
To maintain the beam orbit of beam transport line from RCS to MR in J-PARC (3-50BT), 14 beam position monitors (BPMs) were installed. Their signals gathered in the local control building (D01) have been measured by using 14 digitizing oscilloscopes. The data acquisition system have a performance of shot-by-shot measurement.
KEK, Ibaraki
MELCO SC, Tsukuba
J-PARC, KEK & JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Experiences of operating BPM's during beam commissioning at the J-PARC MR are reported. The subjects are: (1) bug report, statistics and especially the effect of a beam duct step, (2) position resolution estimation (<30 micrometers with 1 sec averaging), (3) beam based alignment.
KEK, Ibaraki
Osaka University, Osaka
Proton beam extinction, defined as a residual to primary ratio of beam intensity, is one of the most important parameters to realize the future muon electron conversion experiment (COMET) proposed at J-PARC. To achieve the required extinction level of 10-9, we started measuring beam extinction at main ring (MR) as the first step. The newly developed beam monitor was installed into the abort beam line and the first measurement was successfully performed by using the fast-extracted MR beam. We found that empty RF buckets of RCS, in which all protons were considered to be swept away by a RF chopper before injection to RCS,, contained about 10-5 of the main beam pulse due to chopper inefficiency. We are now developing a new beam monitor with improved performance for further studies at the abort line. In addition, we have started new measurements at the different stage of proton acceleration, i.e. at Linac, 3-50 BT line, and the main ring. In this paper, we present recent results and future prospect of beam extinction measurements.
J-PARC, KEK & JAEA, Ibaraki-ken
AEC, Chiba
Morimoto Engineering, Iruma, Saitama
NIRS, Chiba-shi
KEK, Ibaraki
Kyoto University, Radioisotope Research Center, Kyoto-shi
A nondestructive beam profile monitor using a nitrogen-molecule gas-jet sheet has been developed for intense ion beams. The density of the gas-jet sheet corresponds to 1 x 10-3 Pa. A light emitted from nitrogen excited by an ion beam collision is measured with a high sensitive camera attached a radiation hard image intensifier. In tests, beam profiles of 6 MeV/u full-stripped oxygen beams whose peak current was 600 μA. were measured. This paper describes characteristics of the instruments and the beam test results.
J-PARC, KEK & JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
A single-wire proportional counter which has the maximum gain of 6·104 is used as a beam loss monitor (p-BLM), thus low-level beam loss can be monitored. However, it involves gain reduction problem by the space charge effect. It is essential to estimate the space charge effect to utilize a proportional counter for beam loss monitoring. The calibration procedure is discussed for the p-BLMs for 3-50BT and MR. Measurements of residual dose were made and some nuclei were identified. Radiation from the short-life nucleus, Fe53 (T1/2=8.51m), may be a good index to predict a residual dose after a long term beam operation.
Nagoya University, Nagoya
UVSOR, Okazaki
Sokendai - Okazaki, Okazaki, Aichi
Central Japan Synchrotron Radiation Research Facility which provides synchrotron radiation for a large community of users is under construction in the Aichi prefecture, Japan. The light source accelerator complex consists of a linac, a booster synchrotron and a storage ring. We have developed beam monitor systems which play important role especially in the commissioning stage of the accelerators. An RF knockout system to observe betatron tune of the electron beam in the booster synchrotron and the storage ring has been designed. We paid special attention in an RF source fed to a shaker to realize efficient measurement of the tune of electron beam during acceleration. We made a test experiment using electron beam of a booster synchrotron of the UVSOR facility. We have also developed a BPM system which enables a single path beam monitoring. The signal processing is based on a fast digital oscilloscope and a simple preprocessor circuit which was developed to improve position resolution. The performance was evaluated using an injection beam pulse to the storage ring of the UVSOR.
Osaka University, Osaka
The Muon Ionization Cooling Experiment (MICE) is an accelerator and particle physics experiment aimed at demonstrating the technique of ionization cooling on a beam of muons. The transverse phase space will be measured by two identical trackers comprised of 5 measurement stations of scintillating fibre inside a 4T solenoid. Both trackers have been assembled and tested using cosmic rays and will be installed in the MICE hall at the Rutherford Appleton Laboratory in 2010. The design, construction and results from cosmic ray testing of both trackers are presented.
JAEA, Rokkasho, Kamikita, Aomori
NIFS, Gifu
Tohoku University, School of Engineering, Sendai
Doshisha University, Graduate School of Engineering, Kyoto
We propose a negative ion beam probe system as a new scheme to diagnose beam profile of high power positive ion beams. Two RF linacs of IFMIF have to drive the neutron source by providing continuous-wave (CW) positive deuterium ion beams with the intensity of 125 mA each at the beam energy of 40 MeV. During the CW beam operations, the extreme intensity of the beam and the severe radiation levels make the beam diagnostics with conventional techniques in the transport lines terribly difficult. A beam of negative ions liable to lose the additional electron at the occasion of impact with a high energy particle can work as a probe to measure the positive ion beam profile. On possible configuration to achieve high intensity beam profile measurement is to inject a negative ion probe beam into the target beam perpendicularly, and measure the attenuation of the negative ion beam by beam-beam interaction at each position. We have started an experimental study for the proof-of-principle of the new beam profile monitoring system. The paper presents the status quo of this beam profile monitor system development and the prospects to apply the system to the IFMIF beam line controls.
Tohoku University, School of Scinece, Sendai
Tohoku University, Research Center for Electron Photon Science, Sendai
A thermionic RF gun has been developed to generate very short electron bunch for a THz light source at Tohoku University. Bunch compression scheme requires, in general, linear momentum distribution of the particles with respect to the longitudinal position, so that measurement of longitudinal phase space is significant for better bunch compression. However, such measurement for the low energy electrons is difficult because space charge effect is so strong that longer drift space should not be included. Consequently, we have performed deliberation for employing energy dependent angular distribution of Cherenkov radiation. Though the energy dependence of emission angle of Cherenkov radiation is rapidly getting small as increasing the beam energy, it is still 25 deg/MeV at an energy around 2.0 MeV when we use radiator having refractive index of 1.035. Thus the beam energy distribution can be measured if we observe Cherenkov ring with sufficient angular resolution. Since this method needs only thin radiator, the drift space length will be minimized. We will discuss limitation for resolutions of both the time and the energy as well.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
J-PARC, KEK & JAEA, Ibaraki-ken
The J-PARC RCS is an M-Watt class rapid cycling synchrotron and it has delivered an intensive beam to the neutron target and the MR. In order to overcome large space charge effect, its physical aperture is designed to be more than 250mm in diameter. Even though its chamber size is very large, the BPM system gives precise data to determine beam optics parameters of the ring. For this purpose, only relative positions and resolutions are important. However, for much higher intensity, the absolute beam position and accurate COD correction are indispensable. We have carefully installed the BPM and measured the position with respect to the quadrupole magnet (QM) nearby. But it is also necessary to estimate its absolute position by using beam. If each QM could be controlled independently, the simple beam based alignment technique can be utilized, but it is not the case for RCS. There are seven families of QM, and only each family can be controlled at one time. We developed a new technique by expanding the simple method for the case of multiple QM focusing changed simultaneously, and applied to the J-PARC RCS. The paper describes this method and discussed about experimental results.
JAEA/J-PARC, Tokai-mura
KEK, Ibaraki
JAEA, Ibaraki-ken
A wire scanner monitor (WSM) is one of essential measurement devices for beam commissioning of current accelerators. J-PARC Linac also employs a number of WSMs for transverse beam profile. The transverse matching is performed based on the measured beam width. In addition, we have tried to measure halo component with the BSMs. In this paper, we present the experimental results obtained in a beam study to characterize the operational performance of the WSM.
ICEPP, Tokyo
KEK, Ibaraki
University of Tokyo, Tokyo
In this paper, we describe a system design and current status of Shintake beam size monitor. Shintake monitor is a laser-based beam diagnostics tool, which provides a non-invasive measurement of transverse beam sizes. The interaction target probing the electron beam is interference fringes build up by the two coherent lasers that have narrow bandwidth and long coherent length. A scale of the target structure corresponds to approximately one fourth of the laser wave length, and the smallest measurable size reaches down to several tens of nanometers. The monitor we described here is installed at the virtual interaction point of the ATF2 beam line, which is built to confirm the proposed final focus system for Future Linear Colliders. We adopt second harmonics of Nd:YAG laser of 532 nm wavelength, and phase stabilization feedback system to allow to measure the designed beam size of about 37 nm. To widen a measurable range up to about 5 microns (wire scanner's range), we also prepare three crossing modes that change an effective wavelength for the fringes. The monitor is used to measure a focus size during the tuning process. The system is based on the Shintake monitor for FFTB.
University of Tokyo, Tokyo
KEK, Ibaraki
ICEPP, Tokyo
ATF2 is the final focus test facility for ILC to realize and demonstrate nanometer focusing. One of the goals of the ATF2 is a demonstration of a compact final focus system based on the local chromaticity correction. A designed beam size at the focal point is to be 37 nm in vertical. To achieve the goal, a beam size monitor capable of nanometer beam size measurement is inevitably needed. Shintake monitor satisfies the demands, and is installed at the virtual interaction point of the ATF2. Shintake monitor is a beam size monitor which uses laser interference fringe pattern to measure beam size. The beam test for the Shintake monitor was successful in measurement of signal modulation with the laser interference fringe pattern in November 2009. In April 2010, beam size of less than 1 micron was achieved. We have studied the error sources, and evaluated the total error to be less than 10% for 1 minute measurement. This paper is about the evaluation of the Shintake monitor performance by analyzing beam tests data. Most systematic error sources are well understood, so that we can estimate accuracy of beam size measurement when the beam size reaches 37nm.
KEK, Tsukuba
RCNP, Osaka
Optical beam measurement such as OTR(Optical Transition Radiation), ODR(Optical Diffraction Radiation), gas Cerenkov, and so on is a powerful tool to observe a two-dimensional information of high intensity beam profile, so that this method is widely used at various electron and hadron accelerators. However, high radiation field to damage an optical system gradually becomes a major issue with increasing the beam intensity to explore new physics. Our present effort is devoted to develop a high efficient optical system to resist such high radiation field. We newly designed an optical system composed of two spherical mirrors which do not have any lenses vulnerable to radiation. Detailed optics design and a result of optical performance test will be presented. Also we will report a result of a beam test experiment of this optics system combined with an OTR screen performed at high intensity proton extraction beamline of the J-PARC.
SESAME, Amman
SESAME machine consists of a 22.5 MeV microtron, 800 MeV booster and a 2.5 GeV storage ring. The electron beam diagnostics will play a major rule during the commisioning and normal operation with different modes of single bunch and multi bunch operations. Furthermore the beam parameteres during injection, acceleration and storing the beam will be measured, monitored and integrated into other subsystems. The major diagnostics components and the general design for booster and storage ring are reported in this paper.
IHEP Beijing, Beijing
To monitor the beam profile at the end of linac non-destructively, Wire scanner as a new diagnostic instrument was designed, manufactured and installed in 2007. After that, we had done beam test for several times using this device. This paper describes the whole system of wire scanner and beam test result.
TUB, Beijing
The coherent Smith-Purcell radiation (CSPR) has been demonstrated as an efficient technique for measuring the longitudinal profile of beam bunches. To measure the ultrashort beam bunches, the simulations for the measurements using CSPR are anlyzed with tools of three dimensional particle-in-cell simulations and Kramer-Kronig reconstruction. Different parameters such as rms length of beam bunch and profiles of grating are studied. Furthermore, the measurement device based on a Martin-Puplett Interferometer is introduced, in which noises and attenuation can be reduced.
USTC/NSRL, Hefei, Anhui
The energy spread measurement by use the energy spectrum analysis system at HLS LINAC now is an intercepting measurement which can't measure the real injection beam. To achieve the non-intercepting measurement, a new Beam position monitor (BPM) with eight stripline electrodes in four-axis symmetry is designed, which can measure the energy spread at HLS LINAC in real time. This paper has introduced the physical structure of this new BPM which include eight 20 degree opening angle, 1/4 wavelength (26.2mm) length Stripline electrodes in detail, analyzed and calculated the electrode response and picking up the quadrupole component, and got the theoretical sensitivities of different methods. The BPM is simulated and calculated by CST Microwave Studio Program. The results shows the parameters such as characteristic impedance, electrode coupling degree, time-domain response and frequency-domain response etc are all meet the requirement of HLS LINAC and transfer line.
USTC/NSRL, Hefei, Anhui
An s-band re-entrant cavity BPM system is designed for new high brightness injector at HLS. A prototype cavity BPM system was manufactured for off-line test, which is also called cold test. According to the results of computer simulation, wire scanning off-line test method can be used to calibrate the BPM and estimate the performance of the on-line BPM system. Cross-talk problem was detected during the cold test. Ignoring nonlinear effect, transformation matrix is a way to correct cross-talk. Analysis of cold test results showed that position resolution of prototype BPM is better than 3 μm.
USTC/NSRL, Hefei, Anhui
A new beam current monitor (BCM) has been implemented on Hefei Light Source (HLS) recently. It has been used for bunch-by-bunch beam current measurement, which is useful for filling control and longitudinal feedback, etc. The BCM consists of three parts: the front-end circuit, a high sampling rate oscilloscope for beam current signal acquisition and the data processing system. The signals from the beam position monitor of the storage ring are manipulated by the front-end circuit first, then sampled by the Agilent MSO7104 oscilloscope and transported into the control computer for data processing. The sampling rate of the oscilloscope is up to 4GHz and the trigger rate is 4.533 MHz. The data processing program is supported by the LabVIEW. The measurement of beam current in multi-bunch operation mode is described. Some important results are summarized.
USTC/NSRL, Hefei, Anhui
In HLS we employ the TED FPGA based processor for digital feedback system. To make feedback system work better and more easily, we developed the control and analysis system based on matlab chiefly. The system do jobs as following: sampling data online and finishing its analysis; calculating fir filter parameters and generating .csv(format for FPGA) file to get the best gain and phase flexibly according to different beam working point; simulating the beam changes in different feedback gain and other stations to check whether the system work properly.
USTC/NSRL, Hefei, Anhui
GigE Vision (Gigabit Ethernet vision standard) is a new interface standard for the latest vision of cameras with higher performance compared to analogue vision standard and other digital vision standard. In recent years, the market of industrial vision components is evolving towards GigE Vision. This paper presents applications of digital camera comply with GigE Vision standard for the measurement of beam profile and emittance at the storage ring of HLS (Hefei Light Source). These cameras provide low distortion for image transmission over long distance with high image rate. Using the image of beam profile transmitted by GigE Vision digital camera, we calculated the horizontal and vertical center positions, and then we calibrated these center positions by BPM (Beam Position Monitor) system. According to the result of calibration and the pixel size of CCD sensor, transverse sizes of beam profile were calculated, further more the transverse emittance and coupling factor were calculated as well.
SINAP, Shanghai
A new beam profile diagnostic system based on industrial Ethernet has been installed in Shanghai Deep Ultraviolet Free Electron Laser (SDUV-FEL) facility recently. By choosing GigE Vision cameras, the system provides better image quality over a long distance than before. Beam images are captured from the beam profile monitors which are controlled by air cylinders or step motors. In order to fit for the system expansibility and curtail the cables, all devices are operated through the Ethernet and distributed along the FEL facility. The approach to the design of the hardware and software will be described in this paper. Applications and experiment results will be shown in this paper as well.
SSRF, Shanghai
Bunch charge uniformity control is very important for storage ring top-up operation. In order to monitor filling pattern and measure bunch charge precisely an PXI waveform digitizer based data acquisition system was developed to retrieve bunch charge information from BPM pickup signals. Effective sampling rate could be extended to 400GHz by waveform rebuilding technology, which folds multi turns data into single turn with real time sampling rate of 8GHz. Online evaluation shows charge resolution could be better than 0.5% for 1nC range.
Kyungpook National University, Daegu
Royal Holloway, University of London, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
Nanometer resolution Beam Position Monitors have been developed to measure and control beam position stability at the interaction point region of ATF2. The position of the beam focused has to be measured within a few nanometer resolution at the interaction point. In order to achieve this performance, electronics for this BPM was developed. Every component of the electronics have been simulated and checked by local test and using beam signal. We will explain each component and define their working range. Then, we will show the performance of the electronics measured with beam signal.
KAERI, Daejon
The PEFP (Proton Engineering Frontier Project) is constructing a 100-MeV proton accelerator, consisting of a 50-keV proton injector, LEBT (Low Energy Beam Transport), a 3-MeV RFQ (Radio Frequency Quadrupole), a 20-MeV DTL (Drift Tube Linac), 100-MeV DTL, and beam lines. In order to monitor signals measured from RF components and beam current monitors equipped to the 20-MeV proton accelerator, the commercial digital sampling oscilloscopes (DSO) are used. The signals, which are measured from the DSOs, must be calibrated and transmitted promptly to accelerator operators. So LabView as Window PC-based software, which equipped with various VISA (Virtual Instruments Software Architecture) interface as a standard I/O language for instrumentation programming, was chosen to do this data acquisition. The LabView was built with EPICS middleware by using the Window-based shared memory approach. In this paper, the preliminary design and implementation on integrating EPICS and LabView for the RF and beam current monitor are described.
KNU, Deagu
Kyungpook National University, Daegu
PAL, Pohang, Kyungbuk
The synchrotron-radiation interferometer was employed for the beam size measurement of electron beam circulating in the storage ring at 2.5 GeV Pohang Light Source. We measured the beam sizes in both vertical and horizontal directions as function of stored beam current. In this presentation, we will discuss the interferometer system, analysis method for the measurement and the measured results. We also compared the measured beam sizes with predicted values from the lattice parameters in the ring.
POSTECH, Pohang, Kyungbuk
PAL, Pohang, Kyungbuk
At Pohang Accelerator Laboratory, a femto-second THz facility was constructed for the experiments using femto-second THz radiation. The fs-THz radiation is generated from 60-MeV electron linac which consists of a photocathode RF gun, two accelerating columns, and two magnetic-chicane bunch compressors. The coherent transition radiation (CTR) is used for THz radiation generation. To generate high intensity THz radiation, the electron bunch length should be smaller than 200 fs. We report THz image obtained using IR-CCD camera and measured beam parameters including bunch length, energy spread, charge, emittance, and transverse beam size.
ITEP, Moscow
Application of a plasma lens to focusing of ion beams has a number of essential advantages. It is important that the focusing capabilities of the lens depend on the stage of plasma development. Under certain conditions a magnetic field is linear, that allow to focus the beam to a very small spot. In other conditions, the magnetic field is nonlinear, that allow formation of hollow and other beam structures. Hollow cylinder-shaped beams of high energetic heavy ions are efficient drivers for implosion targets to create matter in a highly compressed state. The work deals with the study the possibility of using a plasma lens to transformation the density distribution of ions in the beam. Calculations and measurements were performed for a C6+ and Fe26+ beams of 200 MeV/a.u.m. energy. The obtained results and analysis are reported.
RAS/INR, Moscow
Bunch shape monitors with low energy secondary electrons transverse modulation have found a use for measurements of longitudinal distribution of charge in bunches for ion linear accelerators. Temporal bunch structure is coherently transformed into the spatial distribution through transverse rf scanning. The fields of the analyzed beam can influence the trajectories of the secondary electrons thus resulting in a distortion of the transformation and hence to a deterioration of measurement accuracy revealed in worsening of a phase resolution and in appearance of an error of phase reading. The first error component aggravates observation of the bunch fine structure. The second one distorts the measured shape of the bunch as a whole. Two models have been used for the effect analysis. In the first model a target potential of the bunch shape monitor is supposed to be undistorted by the analyzed beam space charge. In the second model a target potential is completely defined by the potential of the analyzed beam bunch. The applicability of the two models is discussed. The results of simulations for typical beam parameters are presented for the latest bunch shape monitor elaborations.
Saint-Petersburg State University, Saint-Petersburg
LETI, Saint-Petersburg
We describe both analytically and numerically beams radiation in presence of media which can be realized as modern metamaterials. In particular, effects of reversed Cherenkov radiation (RCR)* and reversed Cherenkov-transition radiation (RCTR)** are considered. These phenomena can be used for detection of charged particles and diagnostics of beams. Earlier we noted some useful properties of radiation in the case of the boundary between an ordinary medium and an isotropic left-handed metamaterial (LHM)*. Now we continue to analyze prospects of use of LHM for beam diagnostics. Moreover, we investigate RCR and RCTR in the case of certain anisotropic materials with properties being similar to properties of LHM. The useful features are reversed character of radiation and, particularly, existence of two thresholds for RCTR (lower threshold and upper one). This fact allows selection of particles (or beams) with energy in some predetermined range. The specific radiation patterns (having two or three lobes in anisotropic metamaterial) can be useful for particle energy measurement as well.
* Z.Y. Duan, B.-I. Wu, S. Xi, H.S. Chen., M. Chen, Progress in Electromagn. Research, v.90, p.75 (2009).
** S.N. Galyamin, A.V. Tyukhtin, A. Kanareykin, P. Schoessow, PRL, v.103, p.194802 (2009).
Saint-Petersburg State University, Saint-Petersburg
Euclid TechLabs, LLC, Solon, Ohio
We consider the particles energy measurement method offered in our papers (footnotes). It is based on measurement of the modes frequencies in waveguide loaded with certain material. For this method, the modes frequencies must depend on the particles energy strong enough. Here we discuss the problem of selection of materials for this technique. It is shown that high precision of energy measurement can be reached by use of the system of specific parallel conductors. The approximate analytical approach for obtaining effective permittivity of such structure is developed. It is shown that selection of parameters of the structure allows ruling an effective permittivity characterized by both frequency dispersion and spatial one. The structure is simple enough for production. It allows measuring the particles energy for different predetermined ranges. The other ways of realization of the method are discussed as well. One of them consists in use of thin layer of ordinary dielectric. Selection of the layer thickness and dielectric constant allows obtaining strong enough dependence of frequency on Lorentz-factor in the relatively wide range.
A.V. Tyukhtin, S.P. Antipov, A. Kanareykin, P. Schoessow, PAC07, p.4156;
A.V. Tyukhtin, EPAC08, p.1302;
A.V. Tyukhtin, Technical Physics Letters, v.34, p.884 (2008), v.35, p.263 (2009).
TPU, Tomsk
Tomsk Polytechnic University, Nuclear Physics Institute, Tomsk
A noninvasive technique to determine a sub-mm length of electron bunches (rms < 100 um) based on a measurement of the coherent Cherenkov radiation (CChR) spectrum in THz range is proposed. CChR is generated when electron bunch moves in a vacuum near dielectric target. If the optical properties and geometry of a target are chosen in order to achieve a low absorption with a dispersion allowing expanding the Cherenkov cone, such target may be considered as the «natural Cherenkov prism». We demonstrated a feasibility of using of CsI prism for measurement of a bunch length in the range 50-200 um for Lorentz factor = 100. We also measured CChR power from Teflon target generated by the 6.1 MeV bunched electron beam with bunch rms length 1.2 mm and compared it with coherent diffraction radiation one for identical conditions. CChR seems to be a promising radiation mechanism for a new beam diagnostics technique.
I-Tech, Solkan
PSI, Villigen
Measurements were performed at the Swiss Light Source on the beamline X06SA using a four-quadrant CVD diamond sensor which was connected to Libera Photon, a new photon BPM device from Instrumentation Technologies. The outputs of the sensor are 4 current signals in the nA range and are directly connected to the measuring unit without any pre-amplifiers. External bias voltage was applied, although the Libera Photon can supply internal bias voltage. Measurements consisted of: scanning the measurement range, frequency analysis of the beam movement and analysis of the photon beam flux influence on the measured position. The Sensor was mounted on a motorized XY stepper motor stage. Acquired data consisted of raw signal amplitudes and processed positions. Acquisitions were taken at 10 kHz and 10 Hz rate.
Fundación TEKNIKER, Eibar (Gipuzkoa)
Bilbao, Faculty of Science and Technology, Bilbao
STFC/RAL/ISIS, Chilton, Didcot, Oxon
A Front End Test Stand is being built at the Rutherford Appleton Laboratory in the UK to demonstrate a chopped H− beam of sufficiently high beam quality for future high-power proton accelerators (HPPA). The test stand consists on a negative Hydrogen ion source, a solenoid LEBT, a 324 MHz four vane RFQ, a MEBT composed of rebunching cavities and choppers and a set of diagnostics ending with a beam stop. The beam stop, which has to accept a 3 MeV, 60 mA, 2 ms, 50 Hz (10% duty factor) H− beam, consists of a coaxial double cone configuration where the inner cone's inner surface is hit by the beam and the inter-cone gap is cooled by high-speed water. The cones are situated inside a water tank and mounted at one end only to allow thermal expansion. In order to minimize both prompt and induced radiation pure aluminium is used, but the poor mechanical properties of pure aluminium are overcome by employing a metal spinning process that increases the yield strength to several times the original value of the non-deformed material. CFD and FEM codes have been used to avoid high temperature gradients, to minimize thermal stresses, and to minimize fatigue caused by the pulsed beam.
IFIC, Valencia
SLAC, Menlo Park, California
In this paper we describe the design, installation and first calibration tests of a Multi Optical Transition Radiation (OTR) monitor system in the beam diagnostic section of the Extraction (EXT) line of ATF2, close to the multi wire scanner system. This system will be a valuable tool for measuring beam sizes and emittances from the ATF Damping Ring (DR). With an optical resolution of about 2 um an original OTR design demonstrated the ability to measure a 5.5um beam size in one beam pulse and to take many fast measurements. This gives the OTR the ability to measure the beam emittance with high statistics, giving a low error and a good understanding of emittance jitter. Furthermore the near by wire scanners will be a definitive test of the OTR as a beam emittance diagnostic device. The muti-OTR system design proposed here is based on the existing OTR1X, located after the septums at the entrance of the EXT line.
IFIC, Valencia
A set of 16 Inductive Pick-Ups (IPU) for Beam Position Monitoring (BPM) with its associated electronics were designed, constructed and characterized at IFIC for the Test Beam Line (TBL) of the 3rd CLIC Test Facility (CTF3) at CERN. In October 2009 the full set of IPUs, (BPS) was successfully installed in the TBL line. In this paper, we describe the prototyping and series production phases of the BPSs development, focusing in the implementation and the results analysis derived from their characterization tests. Two special test benches were designed and built to perform the characterization tests at low and high frequencies. The low frequency set up based on a wire-method test bench for emulating the beam position variations helped us to determine the BPS performance parameters at beam pulse time scale from 100μs/10kHz to 10ns/100MHz. On the other hand, the high frequency test setup, based on an adapted coaxial transmission line, was dedicated to obtain the BPS longitudinal coupling impedance at the beam microbunches time scale (83ps/12GHz). Furthermore, we also present the first beam performance tests made in the TBL line.
CERN, Geneva
As part of the CERN LHC injector chain upgrade, LINAC4 will accelerate H- ions from 45 keV to 160 MeV. A movable diagnostics test bench will be used to measure the beam parameters during the different construction stages (at 45 keV, 3 MeV and 12 MeV) at first in a laboratory setup and later in the LINAC4 tunnel. Given the beam properties at 3 and 12 MeV, the existing slit-grid system developed for the measurement of the transverse emittance at the source (45 keV) cannot be reused at these higher energies. At 3MeV and above the energy deposition would damage the steel slit in a single LINAC4 pulse. For this reason a new slit has been designed following detailed analytical and numerical simulations for different materials and geometries. The energy deposition patterns as simulated by FLUKA for the different cases are presented in detail. In addition, the choice of SEM grid wires for achieving the required measurement accuracy in terms of material, diameter and spacing, are discussed.
CERN, Geneva
LINAC4 is the first step in the upgrade of the injector chain for the LHC and will accelerate H- ions to 160 MeV. The ion source has initially been installed in a laboratory setup where its commissioning started at the end of 2009. A slit-grid system is used to monitor the transverse emittance at the exit of the source. Measurement results have been compared to analytical and numerical predictions of the system performance, addressing the system resolution, accuracy and sensitivity. This information has been used to improve the design of a new slit-grid system required for commissioning the linac at higher energies.
CERN, Geneva
SMI, Vienna
The hyperfine transition frequency of hydrogen is known to a very high precision and therefore the measurement of this transition frequency in antihydrogen is offering one of the most accurate tests of CPT symmetry. The ASACUSA collaboration will run an experiment designed to produce ground state antihydrogen atoms in a CUSP trap. These antihydrogen atoms will pass with a low rate in the order of 1 per second through a spin-flip cavity where they get excited depending on their polarization by a 1.42 GHz magnetic field. Due to the small amount of antihydrogen atoms that will be available the requirement of good field homogeneity is imposed in order to obtain an interaction with as many antihydrogen atoms as possible. This leads to a requirement of an RF field deviation of less than ± 10 % transverse to the beam direction over a beam aperture with 100 mm diameter. All design aspects of this new spin-flip cavity, including the required field homogeneity and vacuum aspects, are discussed.
CERN, Geneva
SLAC, Menlo Park, California
The University of Liverpool, Liverpool
Synchrotron radiation is currently used on LHC for beam imaging and for monitoring the proton population in the 3 microsecond abort gap. In addition to these existing detectors, a study has been initiated to provide longitudinal density profiles of the LHC beams with a high dynamic range and a 50ps time resolution. This would allow for the precise measurement both of the bunch shape and the number of particles in the bunch tail or drifting into ghost bunches. A solution is proposed based on counting synchrotron light photons with two fast avalanche photo‐diodes (APD) operated in Geiger mode. One is free‐running but heavily attenuated and can be used to measure the core of the bunch. The other is much more sensitive, for the measurement of the bunch tails, but must be gated off during the passage of the core of the bunch to prevent the detector from saturating. An algorithm is then applied to combine the two measurements and correct for the detector dead time, after pulsing and pile‐up effects. Initial results from laboratory testing of this system are described in this paper.
EPFL, Lausanne
CERN, Geneva
To improve the quality of the CLIC Test Facility 3 drive beam, it has been proposed that a photo injector replaces the actual thermionic gun. This would produce a lower emittance beam and minimize beam losses in the injector since the RF bunching and sub‐harmonic bunching systems would not be needed anymore. Such a photo injector, named PHIN, is currently being developed at CERN. One of the difficulties is to provide a high intensity beam (3.5A) with a stable (0.1%) beam energy over 1.5us as well as a relative energy spread less than 1%. A 90° spectrometer line featuring a segmented dump and an Optical Transition Radiation screen has been constructed and commissioned in order to study the time evolution of the beam energy along the pulse duration. In the following paper, we present the design as well as the results from the previous two PHIN runs.
CERN, Geneva
SLAC, Menlo Park, California
On the Large Hadron Collider (LHC), the continuous monitoring of the transverse sizes of the beams relies on the use of synchrotron radiation and intensified video cameras. Depending on the beam energy different synchrotron light sources must be used. A dedicated superconducting undulator has been built for low beam energies (450 GeV to 3 TeV), while edge and centre radiation from a beam separation dipole magnet are used respectively for intermediate and high energies (up to 7 TeV). The emitted visible photons are collected using a retractable mirror, which sends the light into an optical system adapted for acquisition using intensified CCD cameras. This paper presents the performance of the imaging system in terms of spatial resolution, and comments on the light intensity obtained and the cross calibration performed with the wire scanners. Upgrades and future plans are also discussed.
CERN, Geneva
EPFL, Lausanne
Uppsala University, Uppsala
The University of Liverpool, Liverpool
The CTF3 facility is being built and commissioned by an international collaboration in order to test the feasibility of the proposed CLIC drive beam generation scheme. Central to this scheme is the use of RF deflectors to inject bunches into a Delay Loop and a Combiner Ring, in order to transform the initial bunch spacing of 1.5 GHz from the linac to a final bunch spacing of 12 GHz. The optimization procedure relies on several steps. The active length of each ring is carefully adjusted to within a few millimeters accuracy using a two‐period undulator. The transverse optics of the machine must be set-up in a way so as to ensure the beam isochronicity. Diagnostics based on optical streak cameras and RF power measurements have been designed to measure the longitudinal behaviour of the beam during the combination. This paper presents their performance and highlights recent measurements.
CERN, Geneva
CERN's Large Hadron Collider (LHC) is equipped with three distinct types of intensity measurement systems: total intensity measurement using DC transformers (DCCTs) with a bandwidth up to a few kHz; total intensity measurements on a turn-by-turn basis for lifetime measurements using AC-coupled fast transformers (fast BCTs); bunch-by-bunch intensity measurements with a bandwidth up to a few hundred MHz also using the fast BCTs. In addition to providing intensity information these devices are part of the machine protection system, indicating whether or not there is beam circulating, transmitting intensity for evaluation of safe beam conditions and capable of triggering a beam dump if fast losses are detected. This paper reports on the commissioning of all these systems and their initial performance.
CERN, Geneva
University of Oslo, Oslo
The CLIC study is based on the so‐called two‐beam acceleration concept and one of the main goals of the CLIC Test Facility 3 is to demonstrate the efficiency of the CLIC RF power production scheme. As part of this facility a Test Beam Line (TBL), presently under commissioning, is a small scale version of a CLIC decelerator. To perform as expected the beam line must show efficient and stable RF power production over 16 consecutive decelerating structures. As the high intensity electron beam is decelerated its energy spread grows by up to 60%. A novel segmented beam dump for time resolved energy measurements has been designed to match the requirements of the TBL. As a complement, a diffusive OTR screen is also installed in the same spectrometer line. The combination of these two devices will provide both a high spatial resolution measurement of both the energy and energy spread and a measurement with a few nanoseconds time response. This paper describes the design of the new segmented dump and presents the results from the first commissioning of the TBL spectrometer line.
CERN, Geneva
Gas Electron Multipliers (GEM) find their way to more and more applications in beam instrumentation. Gas Electron Multiplication uses a very similar physical phenomenon to that of Multi Wire Proportional Chambers (MWPC) but for small profile monitors they are much more cost efficient both to produce and to maintain. This paper presents the new GEM profile monitors intended to replace the MWPCs currently used at CERN's low energy Antiproton Decelerator (AD). It will be shown how GEMs overcome the documented problems of profile measurements with MWPCs for low energy beams, where the interaction of the beam with the detector has a large influence on the measured profile. Results will be presented from profile measurements performed at 5 MeV using four different GEM prototypes, with discussion on the possible use of GEMs at even lower energies needed at the AD in 2012.
CERN, Geneva
The beta function has a fundamental impact on the LHC performance and on the functioning of its machine protection and collimation systems. A new beta-beat diagnostic system, prototyped at the SPS, has been used to verify the time-dependent variations of the LHC lattice with unprecedented 1% beta-beta resolution and at a measurement bandwidth of about 1 Hz.
PSI, Villigen
For high intensity beam operation (3mA, 1.8MW) in the PSI cyclotron, a new current monitor for proton beams has been installed during the 2009 maintenance period. This current monitor is an actively cooled re-entrant cavity with its resonance tuned at the 2nd RF harmonic (101 MHz). Operating this system presents several challenges due to the heavy shower of energetic particles, the resonator being placed 8 m behind a graphite target. The resonator is actively cooled with water, its external surface was blackened to improve the radiation cooling and its mechanical structure was optimized for good heat conduction. The resonance characteristics are extremely sensitive to structural changes of the resonator. Because of non-uniform temperature distribution and dynamical changes the observed gain drift during operation is of the order of 10%. To correct these drifts 2 tests signals 50 kHz off the RF frequency are measured on-line during beam operation. They provide an innovative mean to estimate and to correct on-line the resonator gain. This paper will present the measurement method and the achieved performances.
PSI, Villigen
DESY, Hamburg
CEA, Gif-sur-Yvette
IPN, Orsay
The European XFEL is an X-ray free electron laser user facility that is currently being built in Hamburg by an international consortium. The electron BPM system of the XFEL is developed by a collaboration of PSI, DESY, and CEA/Saclay/Irfu. Cavity BPMs will be used in all parts of the E-XFEL where highest resolution and lowest drift is required, e.g. in the undulators and some locations in the beam transfer lines. In the cryostats of the superconducting 17.5GeV main linac, 2/3rds of the BPMs will be buttons, while 1/3rd will be re-entrant cavities that promise higher resolution than buttons at low bunch charges. The transfer lines will also be equipped with cost-efficient button BPMs. The BPM electronics is based on a modular system concept, with a common FPGA-based digital back-end design for all BPMs and pickup-specific analog RF front-ends. This paper introduces the design concepts and reports on the project status and measurement results of BPM pickup and electronics prototypes.
PSI, Villigen
ORNL, Oak Ridge, Tennessee
Operation and upgrade of very intense proton beam accelerators like the PSI facility and the SNS spallation source at ORNL is typically constrained by potentially large machine activation. Besides the standard beam diagnostics, beam tomography techniques provide a reconstruction of the beam transverse phase space distribution, giving insights to potential loss sources like irregular tails or halos. Unlike more conventional measurement approaches (pepper pot, slits) beam tomography is a non destructive method that can be performed at high energies and, virtually, at any beam location. Results from the application of the Maximum Entropy Tomography (MENT) algorithm to different beam sections at PSI and SNS will be shown. In these reconstructions the effect of nonlinear forces is made visible in a way not otherwise available through wire scanners alone. These measurements represent a first step towards the design of a beam tomography implementation that can be smoothly employed as a reliable diagnostic tool.
NSRRC, Hsinchu
To keep and achieve desired performance of a modern synchrotron light source, it requires continuous efforts including good design of the accelerator, good performed subsystems and sophisticated feedback system. While some wonders happen unexpectedly and could deteriorate performance of the light source. For examples, some strong source occasionally occurred especially after long shut down or malfunction of some corrector power supply and it would result in increased noise level. Non ideal injection element will cause large perturbation as well. This report presents algorithms to spatially locate source and summarize some of our practical experience to identify the source.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We present preliminary results of beam diagnostics for the world's first Non-Scaling FFAG Accelerator 'EMMA'. Amongst other means, a single-shot/turn-by-turn BPM system is used, that was first tested on the ALICE injector. The BPM system utilizes a front-end conversion of button pickup signals into flat-top-envelope 700 MHz bursts, time-domain multiplexing (in each plane, signals are made spaced by 13.8 ns), and the manufacture of both synchronous detector and ADC clocks directly from the beam signal. The system performance is discussed; results of beam-based resolution measurement are given. First turn beam trajectories furthest from the Septum and Kicker are presented.
JAI, Egham, Surrey
DESY, Hamburg
The PETRA-III Laser-wire, a Compton scattering beam size measurement system at DESY, uses an automated mirror to scan a Q-switched laser across the electron beam and is developed from the system previously operated at PETRA-II. This paper reports on recent upgrades of the optics, vacuum vessel and data acquisition. First beam profile measurements are also presented.
JAI, Egham, Surrey
Royal Holloway, University of London, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
Kyungpook National University, Daegu
UCL, London
KNU, Deagu
Fermilab, Batavia
PLS, Pohang
The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance.
JAI, Egham, Surrey
CERN, Geneva
Royal Holloway, University of London, Surrey
A setup for the investigation of Coherent Diffraction Radiation (CDR) from a conducting screen as a tool for non-invasive longitudinal electron beam profile diagnostics has been designed and installed in the Combiner Ring Measurement (CRM) line of the CLIC Test Facility (CTF3, CERN). In this report the status of the monitor development and results on the interferometric measurements of CDR spectra are presented. The CDR signal correlation with an RF pickup and a streak camera is reported. The future plans for the system improvements are also discussed.
USTRAT/SUPA, Glasgow
University of Dundee, Nethergate, Dundee, Scotland
TUE, Eindhoven
UAD, Dundee
The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme at the University of Strathclyde is developing laser-plasma wakefield accelerators to produce high energy, ultra-short duration electron bunches as drivers of radiation sources. Coherent emission will be produced in a free-electron laser by focussing the electron bunches into an undulator. To achieve net gain, a high peak current, low energy spread and low emittance are required. A high intensity ultra-short pulse from a 30 TW Ti:sapphire laser is focussed into a helium gas jet to produce femtosecond duration electron bunches in the range of 80 - 200 MeV. Beam transport is monitored using a series of Lanex screens positioned along the beam line. We present measurements of the electron beam energy spread as low as 0.7% (at 90 MeV) obtained using a high resolution magnetic dipole spectrometer. We also present pepper-pot measurements of the normalised transverse emittance of the order of 1 pi mm mrad. With further acceleration to 1 GeV, the beam parameters indicate the feasibility of a compact X-ray FEL with a suitable undulator.
The University of Liverpool, Liverpool
MPI-K, Heidelberg
Cockcroft Institute, Warrington, Cheshire
Supersonic gas-jets have attracted much interest as experimental targets in several fields of science since they combine low internal temperatures with high directionality. Axisymmetric jets have found widespread application, triggering a wealth of studies on their properties, while only a limited number of detailed studies have been done on planar jets. In this paper, the design of a beam profile monitor based on a planar supersonic gas-jet for use in the Ultra-low energy Storage Ring (USR) at the Facility for Antiproton and Ion Research (FAIR) in Germany is described. Optimization of the monitor requires investigation into different characteristic jet parameters. For that purpose extensive simulation work with the Gas Dynamics Tool (GDT) was done. The results of these studies are presented together with a description of a novel nozzle-skimmer configuration and an experimental test stand to benchmark the numerical results.
JAI, Oxford
We present the design of a stripline beam position monitor (BPM) signal processor with low latency (c. 10ns) and micron-level spatial resolution in single-pass mode. Such a BPM processor has applications in single-pass beamlines such as those at linear colliders and FELs. The processor was deployed and tested at the Accelerator Test Facility (ATF2) extraction line at KEK, Japan. We report the beam test results and processor performance, including response, linearity, spatial resolution and latency.
JAI, Oxford
We report on the possible utilisation of Smith-Purcell radiation to measure the longitudinal profile of 50-femtoseconds electron bunches. This length is typical for the bunches currently produced by Laser Wakefield Acceleration and is at the limit of what is achievable by alternative techniques, such as Electro-Optic sampling.
JAI, Oxford
CERN, Geneva
Pepper-pot based transverse emittance measurement has the advantage of providing a fast (single shot) measurement with a relatively simple hardware. We report on Pepper-pot based transverse emittance measurements made at the CERN Linac 4 test stand.
JAI, Oxford
Although the pepper-pot method has been used for decades at low energy to measure the transverse emittance of particles sources, it has only been extended to high energy very recently. We report on some of the recent measurements done at high energy (several hundred MeVs) and discuss the practical consideration of such measurements. We show demonstrate that an extended pepper-pot does not significantly affect the phase space of the beam and thus provides a valid transverse emittance measurement.
OXFORDphysics, Oxford, Oxon
INFN MIB, MILANO
The international Muon Ionization Cooling Experiment (MICE) will carry out a systematic investigations of ionization cooling of a muon beam. As the emittance measurement will be done on a particle-by-particle basis, a sophisticated beam instrumentation is needed to measure particle coordinates and timing vs RF. A PID system based on three time-of-flight detectors, two Aerogel Cerenkov counters and a KLOE-like calorimeter has been constructed in order to keep beam contamination (e, π) well below 1 %. The MICE TOF system will measure timing with a resolution better than 60 ps per plane, in a harsh environment due to high particle rates, fringe magnetic fields and RF backgrounds. Performances in beam of all detectors will be shown, as also future upgrades.
Diamond, Oxfordshire
University of Oxford, Clarendon Laboratory, Oxford
JAI, Oxford
Single shot emittance measurement is essential to assess the performance of new generation light sources such as linac based X-ray FELs or laser plasma wakefield accelerators. To this aim, we have developed a single shot emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one shot. We present here test measurements performed at Diamond in the transfer line from the Booster to the Storage Ring, using thin OTR and also YAG screens. We also compare these measurements with results from the more conventional quadrupole scan method and also measurements using an OTR screen and an assembly of two cameras imaging the beam size and the beam divergence at a point near the waist of the beam. The validity and limits of the new method are discussed in the paper.
Diamond, Oxfordshire
JAI, Oxford
Electron bunch profile and length measurement from large bandwidth synchrotron radiation with a streak camera can be strongly limited by the chirp introduced by the length of material present in the input refractive optics of streak cameras. Elimination of the chirp can be done either by filtering the bandwidth of the synchrotron radiation pulses, by measuring time resolved spectra with the streak camera, or by replacing the front optics lenses by focussing mirrors. The first solution reduces the power available, thus limiting measurements to minimum bunch current that can be too high to assess the 'zero' current bunch length. The second elegant solution allows measurement of the bunch length with the whole bandwidth and available power but with loss of the second sweep axis in the camera, so that no beam dynamics can be observed. In order to prevent any pulse chirp, keep all the available power and capability of beam dynamics observation, we designed a new input optics exclusively with mirrors. We present here our design and the results of the system with our streak camera, measuring 2ps bunch in the new Diamond low-alpha lattice.
ZTEC Instruments, Albuquerque
Off-the-shelf instruments based on the LAN eXtensions for Instrumentation (LXI) standard that include embedded EPICS input/output controllers (IOCs) are an ideal solution for many particle accelerator applications. These applications require responsive remote control and real-time waveform monitoring for critical accelerator systems including machine protection, beam position monitoring and others. These instruments have the same feature sets and powerful analysis capabilities that today's high-end benchtop instruments have. With an embedded EPICS controller, the instruments easily integrate into the EPICS environment without the need for EPICS drivers or external controllers. They can be controlled and monitored by EPICS applications such as EDM and MEDM. These EPICS oscilloscopes and digitizers perform advanced real-time waveform math and analysis using on-board FPGAs and DSP. The paper will detail how ZTEC Instruments' EPICS oscilloscopes are being used at facilities around the world for real-time control and monitoring via EPICS.
ANL, Argonne
The Advanced Photon Source (APS) is a third-generation synchrotron light source in the United States. The BPM electronics plays an important part in the beam stability control. This paper presents comparative measurements of two BPM electronics: Libera Brilliance and APS FPGA-based BSP100. Some important parameters such as beam current dependence, electronics resolution and fill pattern dependence have been measured. These measurements were carried out in the lab and in the real system. The results will be useful for deciding which BPM electronics to deploy in the APS upgrade project.
Fermilab, Batavia
In fast ramping synchrotrons, like the Fermilab Booster, the usual methods for evaluating the betatron tunes from the spectrum of turn-by-turn data may fail due to fast decoherence of particle motion or rapid tune changes, in addition to the BPM noise. We propose a technique based on phasing of the signals from different BPMs. Although the number of the Fermilab Booster BPMs is limited to 48 per plane, this method allows to detect the beam tunes in conditions where the other algorithms were unsuccessful. In this paper we describe the method and its implementation in the Fermilab Booster control system. Results of measurements are also presented.
Fermilab, Batavia
CERN, Geneva
A common-mode free cavity BPM is currently under development at Fermilab within the ILC-CLIC collaboration. This monitor will be operated in a CLIC Main Linac multi-bunch regime, and needs to provide both, high spatial and time resolution. We present the design concept, numerical analysis, investigation on tolerances and error effects, as well as simulations on the signal response applying a multi-bunch stimulus.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
Grove City College, Grove City, Pennsylvania
The CESR Damping Ring Test Accelerator collaboration (Cesr-TA) utilizes the CESR e+/e- storage ring at Cornell University for carrying out R&D activities critical for the ILC damping rings. In particular, various locations have been instrumented for the study of the electron cloud effects and their amelioration. In this paper we present the results obtained using the TE wave propagation method to study the electron cloud evolution and its dependence on several beam and machine parameters. Whenever possible, we have also compared our measurements with those obtained by using retarding field analyzers (RFA) with good agreement. Amongst the results obtained, we were able to detect a strong resonance of the electron cloud with the TE wave in regions of the beampipe where a dipole-like magnetic field is also present. Besides the standard transmission method, we are also developing an alternative procedure, the so-called resonant BPM, which can be used for a more localized measurement of the electron cloud density, which has already yielded promising results.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
The beam position monitor (BPM) system at the Cornell Electron Storage Ring (CESR) has been upgraded for use in both CESR Test Accelerator (CesrTA) and Cornell High Energy Synchrotron Source (CHESS) operations. CesrTA operates with electron and positron bunch trains with as little as 4ns bunch spacing. CHESS operates with simultaneous counter-rotating electron and positron trains with 14ns bunch spacing. The upgraded BPM system provides high resolution measurement capability as is needed for the CesrTA ultra low emittance operations, turn-by-turn digitization of multiple bunches for beam dynamics studies, and the capability for real-time dual beam monitoring in CHESS conditions. In addition to standard position measurement capability, the system is also required to measure betatron phase by synchronous detection of a driven beam for optics diagnosis and correction. This paper describes the characteristics of the BPM hardware upgrade, performance figures of the electronics designed for this purpose and the overall status of the upgrade effort. Examples of key measurement types and the analysis of data acquired from the new instruments will also be presented.
CLASSE, Ithaca, New York
KEK, Ibaraki
We report on the design and operation of the CesrTA x-ray beam size monitor (xBSM). The xBSM resolution must be sufficient to measure vertical beam sizes of order 10um by imaging 2-4keV synchrotron radiation photons onto a one-dimensional photodiode array. Instrumentation in the evacuated x-ray beam line includes upstream interchangeable optics elements (slits, coded apertures, and Fresnel zone plates), a monochromator and an InGaAs photodiode detector. The readout is a beam-synchronized FADC that is capable of parallel measurement of consecutive bunches with 4ns spacing. The xBSM has been used to measure beam sizes during the August 2009, November 2009, and April 2010 runs. Single turn measurements are fit to characteristic image shapes to extract beam sizes independent of position variations. The turn-averaged beam size provides feedback for low-emittance tuning.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
During the last several years CESR has been studying the effects of electron clouds on stored beams in order to understand their impact on future linear-collider damping ring designs. One of the important issues is the way that the electron cloud alters the dynamics of bunches within the train. Techniques for observing the dynamical effects of beams interacting with the electron clouds have been developed. These methods will be discussed and examples of measurements will be presented.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
For successful operation and beam characterization, fourth generation light sources require the observation of sub-picosecond bunches with femtosecond resolution. In this paper, we report on the design and development of a novel technique to achieve sub-femtosecond temporal resolution of high brightness bunches. The technique involves the coupling of the electron beam to a high power laser in an undulator field, which is optimized to maximize the angular deviation of the bunch. The beam angular components are imaged on a distant screen yielding a sweep across angles in one dimension. The addition of an x-band deflecting cavity downstream of the undulator creates another sweep of the beam, in the perpendicular dimension. The temporal resolution of the bunch is dependent on the seed laser wavelength and the spatial resolution of the screen. Initial calculations show that for a CO2 laser (T~30fs) and a phosphor screen (~50micron spatial resolution), the longitudinal resolution is approximately l/200 of the laser wavelength, or ~150 attoseconds.
RadiaBeam, Marina del Rey
NRL, Washington D.C.
A beam profile monitor utilizing the technological advances in fiber optic manufacturing to obtain micron level resolution is under development at RadiaBeam Technologies. This fiber-optic profiling device would provide a lost cost, turn-key solution with nominal operational supervision and requires minimal beamline real estate. We are currently studying and attempting to mitigate the technical challenges faced by a fiber optic based diagnostic system with a focus on radiation damage to the fibers and its effect on signal integrity. Preliminary irradiation studies and conceptual operation of the system are presented.
RadiaBeam, Marina del Rey
INFN/LNF, Frascati (Roma)
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
The quest for detailed information concerning ultra-fast beam configurations, phase spaces and high energy operation is a critical task in the world of linear colliders and X-ray FELs. Huge enhancements in diagnostic resolutions are represented by RF deflectors. In this scenario, Radiabeam Technologies has developed an X-band Travelling wave Deflector (XTD) in order to perform longitudinal characterization of the subpicosecond ultra-relativistic electron beams. The device is optimized to obtain a single digit femtosecond resolution using 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory; however, the design can be easily extended to be utilized for diagnostics of GeV-class beams. The XTD design fabrication and tuning results will be discussed, as well as installation and commissioning plans at ATF.
* J. England et al., "X-Band Dipole Mode Deflecting Cavity for the UCLA Neptune Beamline".
** D. Alesini, "RF deflector-based sub-ps beam diagnostics: application to FELs and advanced accelerators".
RadiaBeam, Marina del Rey
BNL, Upton, Long Island, New York
For high average current electron accelerators, such as Energy Recovery Linacs (ERL), the characterization of basic electron beam properties requires non-interceptive diagnostics. One promising non-destructive approach for a high average current beam diagnostic is the laser wire scanner (LWS). RadiaBeam Technologies is developing an inexpensive, stand-alone laser wire scanner system specifically adapted to ERL parameters. The proposed system utilizes distinctive features of ERL beams, such as a relatively long bunch length and ultra-high repetition rate, to maximize photon count while using off the shelf laser technology. The RadiaBeam LWS prototype presently under development will be installed and commissioned at the Brookhaven National Laboratory (BNL) ERL facility. This system's design and projected performance are discussed herein.
RadiaBeam, Marina del Rey
Spectrum Detector, Lake Oswego, Oregon
UGA, Athens, Georgia
PSI, Villigen
This paper reports on the progress of the development of a bunch length diagnostic for high brightness beams. The diagnostic, termed the real time interferometer, is a single shot, autocorrelator that outputs the interferogram of coherent radiation emitted from compressed, high-brightness beams. The device uses all-reflective terahertz optics as well as a highly sensitive pyroelectric-based detector array. For initial testing, coherent transition radiation is used, however, the diagnostic can be used in a non-destructive manner if coherent edge or synchrotron radiation is employed. Current research includes diagnostic design and preliminary tests conducted at the BNL Accelerator Test Facility.
USC, Los Angeles, California
SLAC, Menlo Park, California
SPEAR3 is a third-generation synchrotron light source storage ring. The beam stability requirements are ~10% of the beam size, which is about 1 micron in the vertical plane. Hydrostatic level system (HLS) measurements show that the height of the SPEAR3 tunnel floor varies by tens of microns daily. We present analysis of the HLS data, including accounting for common-mode tidal motion. We discuss the results of experiments done to determine the primary driving source of ground motion. We painted the accelerator tunnel walls white; we temporarily installed Mylar over the asphalt in the center of the accelerator; and we put Mylar over a section of the tunnel walls.
University of Notre Dame, Notre Dame
Royal Holloway, University of London, Surrey
JAI, Egham, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
The demonstration of the stability of the position of the focused beam is a primary goal of the ATF2 project. We have installed a laser interferometer system that will eventually correct the measurement of high-precision Beam Position Monitors used in the ATF2 Final Focus Steering Feedback for mechanical motion or vibrations. Here, we describe the installed system and present preliminary data on the short- and long-term mechanical stability of the BPM system.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
A laser wire system* has been developed in the Spallation Neutron Source (SNS) superconducting linac (SCL). The SNS laser wire system is the world largest of its kind with a capability of measuring profiles of an operational hydrogen ion (H-) beam at each of the 23 cryomodule stations along the SCL by using a single light source. Presently 9 laser wire stations have been commissioned that measure profiles of the H- beam at energy levels from 200 MeV to 1 GeV. The laser wire diagnostics has no moving parts inside the beam pipe and can be run parasitically on a neutron production H- beam. This talk reports our recent study of the laser wire profile measurement performance. Parasitic profile measurements have been conducted at multiple locations of SCL on an operational one-megawatt neutron production beam that SNS recently achieved as a new world record. We will describe experimental investigations of the laser wire system performance including the stability and repeatability of the measurement and the influence of the laser parameters. We will also discuss novel beam diagnostics capabilities at the SNS SCL by using the laser wire system.
* Liu et al., "Laser wire beam profile monitor in the SNS superconducting linac," Nucl. Instr. and Meth. A, to appear.
BNL, Upton, Long Island, New York
CEA, Gif-sur-Yvette
Commissioning of spin flipper in the RHIC (Relativistic Heavy Ion Collider) Blue ring during the 2009 RHIC polarized proton run showed significant global vertical coherent betatron oscillations induced by a two AC dipole plus four DC dipole configuration. These global orbital coherent oscillations affected collision rates and Yellow beam polarization when beams were in collision. The measured depolarizing strength of of the two AC dipoles at a phase difference of 180 degrees at injection with a different spin tune also confirmed that a single isolated spin resonance can not be induced in the presence of this global vertical coherent betatron oscillation. Hence, a new design was proposed to eliminate the coherent orbital oscillation outside the spin flipper with three additional AC dipoles. This paper presents the new design and supporting numerical simulations. In the RHIC 2010 Au run, only one AC dipole was inserted between the two original AC dipoles; and the measured closure of this AC dipole bump is also presented.
This work is under the auspices of the US Department of Energy
GSI, Darmstadt
Non-destructive profile measurements are preferred not only for single-pulse diagnostics at different locations in a transfer line, but also to enable time resolved observations of stored the beam within a synchrotron. Moreover, the large beam power available at modern hadron accelerators excludes intersecting materials like screens, SEM-grids or scanners. Over the last years advanced concepts were realized: Ionization profile monitors are based on residual gas ionization and their spatially resolved detection. A complimentary method uses single photons detection of beam induced residual gas excitation. A third method is based on the deflection of a crossing electron beam to reconstruct the beam's transverse distribution. At LINACs for negative hydrogen acceleration, a scanning laser beam combined with a photo-electron detector was developed. The transverse profile can be monitored by means of a dedicated pick-up for the determination of the beam's quadrupole moment, i.e. the difference of the horizontal and vertical beam variance. The physical principles and technical realizations of these monitors are discussed.
JASRI/SPring-8, Hyogo-ken
This presentation will cover the topics of synchrotron radiation monitors for light sources, including transverse beam profile measurement, longitudinal bunch profile measurement, and bunch purity measurement. It will also cover developments of beam diagnostics based on observation of x-rays from a dedicated insertion device.
Tohoku University, Graduate School of Science, Sendai
KEK, Ibaraki
Tohoku University, School of Scinece, Sendai
We have studied a beam orbit tilt monitor for stabilizing the beam orbit in ATF2. Once we can measure a beam orbit tilt with high precision at one point, we can relate this data with the beam position profile at the focal point. A tilt monitor is composed of a single rectangular sensor cavity and a waveguide to extract the signal. In the sensor cavity, there is the most basic resonant mode called monopole mode. This monopole mode is perpendicular to the nominal beam axis, and excited by the beam tilt. We extract this monopole mode. As the result, the amplitude of the extracted signal is proportional to the tilt angle. The tilt monitor is almost indepnedent with beam postion, so we can get the tilt date independently. According to our simulation, the sensitivity is estimated about 35nrad in the vertical direction. The prototype was completed and installed in the test area on the ATF2 beamline. The first beam test will be performed in December 2009. We will report this result and future update plan.