CLASSE, Ithaca, New York
A need for femtosecond resolution beam arrival time measurements has arisen with the transition from many-picosecond-long bunches in ring-based accelerators to a few femtosecond-long bunches in high- gain free-electron lasers. Here we present an electro-optical detection scheme that uses the signal of a beam pick-up to modulate the intensity of a femtosecond laser pulse train. By detecting the energies of the laser pulses, the bunch arrival time can be deduced. We tested this scheme by distributing a laser pulse train to two locations in the FLASH linac, separated by 60 m, using length-stabilized optical fibers. By measuring the arrival times of the same electron bunches at these two locations, we determined an rms bunch arrival time resolution of 6 fs. This unprecedented monitor resolution allowed us to reduce the beam arrival time jitter from almost 200 fs down to 25 fs with an intra-bunch train feedback. Alternatively, the same detection scheme can be used for large dynamic range micrometer-resolution beam position measurements by using a stripline-type pickup mounted perpendicularly to the beam path, and then detecting the arrival time difference of both pick-up signals.
BNL, Upton, Long Island, New York
The Faraday Cup Award is given for an outstanding contribution to the development of an innovative particle beam diagnostic instrument of proven workability. It is presented at the Beam Instrumentation Workshop (BIW), a biennial forum for in-depth discussions of techniques for measuring particle beams produced in accelerators. This session will present the latest Faraday Cup winner, and the Proceedings article associated with it will summarize the history of the award. After the award is presented, this year's honoree (a secret until the Workshop) will give a talk on the design and performance of the winning instrument. For more information on the Award, see http://www.faraday-cup.com.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on the transverse and longitudinal diagnostics. The coherence effects of the beam profile monitors and the challenges of measuring fs-long bunches are discussed.
BNL, Upton, Long Island, New York
A residual gas x-ray beam position monitor (RGXBPM) was developed for PETRA-III storage ring. This type of x-ray beam position monitors (XBMP) tend to overcome some deficiencies of the blade type XBPMs, which are currently employed at the third generation synchrotron facilities as "white" undulator beam XBPMs. While blade XBPMs provide micron-accuracy resolution, the signal depends on the undulator gap and is also affected by stray radiation from bending magnets and focusing optics. The residual gas XBPM detects position of the centre of gravity of the undulator radiation; it has no elements that are hit by the x-ray beam, and complies with the windowless concept of the PETRA-III beamlines. Residual gas beam profile monitors were first developed to provide beam profile measurements at charged particles accelerators. The spatial resolution of RGXBPM was substantially improved in order to comply with the requirements at the PETRA III storage ring. Due to limited space, a thorough electrostatic optimization of RGXBPM was needed to achieve required electrical field quality. Test results obtained at the ESRF and commissioning of the RGXBPMs at PETRA-III will be reported.
LBNL, Berkeley, California
SLAC, Menlo Park, California
The scientific potential of femtosecond x-ray pulses at linac-driven FELs such as the LCLS is tremendous. Time-resolved pump-probe experiments require a measure of the relative arrival time of each x-ray pulse with respect to the experimental pump laser. In order to achieve this, precise synchronization is required between the arrival time diagnostic and the laser, which are often separated by hundreds of meters. We describe an optical timing system based on stabilized fiber links which has been developed for the LCLS to provide this synchronization. Preliminary results show synchronization of the synchronization signals at the sub-10 fsec level and overall synchronization of the x-ray and pump laser of <40 fsec. We present details of the implementation and LCLS and potential for future development.
CERN, Geneva
CLASSE, Ithaca, New York
PSI, Villigen
In the CLIC project, highest luminosity will be achieved by generation and preservation of ultra low beam emittances. It will require a mechanical stability of the quadrupoles down to 1 nm rms above 1 Hz through up to 24 km of linac structures. Studies are being undertaken to stabilize each quadrupole by an active feedback system based on motion sensors and piezoelectrical actuators. Since it will be very difficult to prove the stability of the magnetic field down to that level of precision, an attempt was made to use a synchrotron electron beam as a sensor and the beam motion was observed with a standard button BPM equipped with high resolution electronics. Hence in two consecutive experiments at CESR-TA (Cornell University, Wilson Lab) and at SLS (PSI-Villingen) the residual eigenmotion of the electron beam circulating in these two machines was measured in the frequency range 5700 Hz. This paper describes in detail the achieved results alongside with purpose of the measurement, the equipment used for observation of the beam rest-motion, and the vibration measurements of mechanical machine elements.
Tohoku University, School of Scinece, Sendai
Generation of high brilliance beam using an RF gun is very attractive for advanced use of electron linacs. Beam dynamics in the RF gun has been studied theoretically so far, and many simulation codes have been developed. The stage in which the beam is extracted and accelerated to relativistic momentum is crucial for understanding of space charge dominated beams. In this sense, actual measurement of the beam phase space is highly desired to examine the validity of the simulation codes. However, for the low energy electrons, such measurement is difficult because the phase space is easily distorted due to space charge effect during travel through drift space. Accordingly, we have considered employing the energy dependent angular distribution of Cherenkov radiation. Though the emission angle of Cherenkov radiation decreases rapidly with increasing beam energy, it is still 25 deg/MeV at an energy around 2 MeV when we use a radiator that has a refractive index of 1.035. Thus the energy distribution can be measured by observing the Cherenkov ring with sufficient angular resolution. Since this method needs only a thin radiator, the drift space length can be minimized.
Fermilab, Batavia
Optical transition radiation (OTR) imaging for transverse beam-size characterization is a well-established technique at many accelerators including the Fermilab A0 photoinjector (A0PI) facility. However, there is empirical evidence for gamma greater than 1000 beams that the utilization of the polarization component orthogonal to the dimension of interest resulted in a smaller projected image profile. Generally, at the A0PI low beam energies of 14-15 MeV and emittances of 3 mm mrad, one encounters beam sizes of 0.8 to 1.5 mm (σ). However, the use of 50-micron wide slits to sample the beam’s transverse phase spaces significantly alters the required resolution of the converter screen and imaging system. In this case, we dealt with slit-image sizes of about σ 100 microns and less, depending on drift distance and beam divergence. In the course of our study of the slit images, we have found that the OTR polarized component orthogonal to the narrow beam dimension of interest systematically gave us ~20-micron smaller projected image sizes than with the total OTR intensity. This is one of the first reports of this polarization effect at such a low-gamma regime (~30).
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Royal Holloway, University of London, Surrey
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The front end test stand FETS is an R&D project hosted at Rutherford Appleton Laboratory RAL with its aim to demonstrate a high power, fast chopped H- ion beam and will consist in final stage of ion source, low energy beam transport LEBT, RFQ and a transport line including a chopper system at 3MeV output energy. Possible candidates of applications are Isis upgrade (RAL neutron source), future spallation sources or the Neutrino factory. The high beam power may cause problems due to its thermal power deposition on diagnostics parts introduced into the beam so non-interceptive beam instruments are highly preferred to avoid those problems. Diagnostics for H- beams can benefit of laser light where photons with suitable energy are able to detach the additional electron. This method is applied to a beam profile monitor close to the ion source of the FETS beam line and the paper gives a status report of the ongoing process of commissioning and provides a detailed discussion of problems and recent changes including first "proof-of-principle" measurements.
BNL, Upton, Long Island, New York
Four ionization profile monitors (IPMs) in RHIC measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. In 2007 a prototype of a new design was installed in the yellow ring. During the 2007-2008 run it proved to be almost completely free from backgrounds from rf coupling, electron clouds and x-rays from upstream beam loss. In 2009 two more IPMs of this new design were installed and in the 2010 shutdown we will complete installation of four identical IPMs. This paper describes the new IPMs and shows data from the 2010 beam run. The new IPMs have been extremely important in the commissioning of the RHIC stochastic cooling system.
BNL, Upton, Long Island, New York
A beam profile and energy monitor for H- beams which measures electrons stripped from the beam by a laser has been installed in the high energy beam transport (HEBT) line at the Brookhaven National Lab linac. Our 100mJ/pulse, Q-switched laser neutralizes 70% of the beam during its 10ns pulse. Also electrons are stripped by the residual gas at a rate of ~1.5 x 10-8/cm at 1 x 10-7torr. Beam electrons have the same velocity as the beam and so have an energy of 1/1836 of the beam protons. There is a chamber in which the laser light passes through the ion beam followed by a dipole magnet which deflects the electrons by 90° through a biased retarding grid (V<125kV) into a Faraday cup detector. To measure beam profiles, a narrow laser beam is stepped across the ion beam removing electrons from the portion of the H- beam intercepted by the laser. To measure the energy spectrum of the electrons, we use either the gas-stripped or laser-stripped signal. The total current is measured as the voltage on the grid is raised in small steps. We deduce the energy spread of the H- beam by deconvolving the electron spectrum into components from beam energy and from space-charge fields.
NSTec, Los Alamos, New Mexico
LANL, Los Alamos, New Mexico
An optical diagnostic instrument developed for the acquisition of high-speed time-resolved images has been fielded at the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility at Los Alamos National Laboratory. The instrument was developed for the creation of time histories of electron-beam cross-section through the collection of Cerenkov light. This is accomplished through four optical lines of sight that optically collapse an image, an optical fiber relay, recording instruments, and a tomographic reconstruction algorithm. The instrument may be operated, adjusted, and calibrated remotely due to potential adverse environmental conditions. The instrument was operated over the course of various activities during and after DARHT commissioning, and tomographic reconstructions reported verifiable beam characteristics. Results from the collected data and reconstructions and analysis of the data are discussed.
LANL, Los Alamos, New Mexico
The primary goal of this newly installed beam profile measurement is to provide the facility operators and physicists with a reliable horizontal and vertical projected beam distribution and location with respect to the proton beam target and beam aperture. During a 3000-hour annual run cycle, 5 microcoulombs of charge is delivered every 50 milliseconds through this harp to the downstream 1L target. The resulting radioactive annual dose near this harp is at least 600 MRads. Because of this harsh environment, the new harp design has been further optimized for robustness. For example, compared to an earlier design, this harp has half of the sensing wires and utilizes only a single bias plane. The sensing fibers consist of a 0.078-mm diameter SiC fiber. To hold these fibers to a rigid ceramic structure, a “collet” fiber-clamping device accomplishes the three goals of maintaining a mechanical fiber clamp, holding the sense fiber under a slight tensile force, and providing a sensing fiber electrical connection. This paper describes the harp analysis and design, and provides fabrication, assembly, and installation information, and shows how facility wiring was altered.
DESY, Hamburg
To control the beam position at the entrance of the FLASH dump a position monitor is required outside of the vacuum. When a charged particle travels through a gas it will ionize the atoms. Therefore the signal from a capacitive button monitor is caused not only by the electric field of the beam but also by the ionized atoms which add high background to the usable signal. To avoid the ionization signal a magnetic coupled monitor is designed. The monitor consists of four longitudinal loops symmetrically arranged at the tube wall. An analytical expression of the signal for this monitor is derived and compared with simulation. Raw data are compared with the expectation.
ANL, Argonne
For reliable radiation dosimetry of undulator magnets, a beam loss monitor (BLM) covering a large solid angle from the point of beam losses is highly desirable. A BLM that uses a Cherenkov radiator plate wrapping around the beam pipe is utilized in the Linac Coherent Light Source (LCLS) undulator systems, and a similar BLM geometry is currently being tested for the Advanced Photon Source (APS) undulators. We report on measurements made with large solid-angle BLMs recently installed in the APS storage ring (SR) and the booster-to-SR transfer line (BTS) to assess the following design and performance characteristics: (1) relative sensitivity of the Cherenkov detector as a function of the transverse position of electron entry into the quartz radiator; (2) signal intensity as a function of the detector distance from the nominal beam loss location at the undulator vacuum chamber entrance; and (3) the effect of incorporating different tungsten/lead enhancers upstream of the radiator. The measured data will be compared with numerical simulation of the beam loss processes.
ANL, Argonne
Accurate and stable x-ray beam position monitors (XBPMs) are key elements in a feedback system for obtaining desired x-ray beam stability. For the low-emittance mode of operation of the APS, the cross sections of the undulator x-ray beams are not upright ellipses, and the effective beam sizes in the horizontal and vertical planes depend on the undulator gaps. These beam characteristics introduce strong gap dependence in blade-type XBPMs designed for upright elliptical beams. A center-of-mass detector XBPM will significantly reduce the gap dependence of the BPM readings. We report the development status of a high-power center-of-mass XBPM at the APS. We note that users often discard more than 50% of the undulator beam power outside of the monochromatic beam. These photons can be intercepted by the limiting aperture of the beamline, and then the x-ray fluorescence footprint can be imaged onto a detector. The position of the x-ray beam can be read out using position-sensitive silicon photodiodes. Thermal analyses show that the XBPM can be used for the measurement of beam with a total power up to 20 kW for the 7-GeV / 200-mA operation of a 5-m undulator in the APS.
ANL, Argonne
LBNL, Berkeley, California
Time-correlated single-photon counting (TCSPC) techniques have been used for bunch purity measurement since the Advanced Photon Source started operations. Over the past three years, improvements made in the monitor have increased the signal-to-noise ratio and dynamic range to above 10 billion. Recently, improvements of the timing resolution of TCSPC to < 50 ps FWHM allowed us to measure the longitudinal profile of individual bunches in the APS storage ring. The profile monitor uses a visible-light single-photon avalanche photodiode (SPAD) and a PicoHarp 300 TCSPC unit. Due to its robustness, the system operates continuously and measures the average longitudinal profile of the stored beam, updating the process variables for bunch phases and bunch lengths in intervals less than 30 seconds. In a third application, using a TCSPC x-ray detector with an x-ray wire scanner in the monochromatic beam of the diagnostics undulator, measurements of transverse profiles of individual bunches can be completed in less than 30 minutes. Since the beam sizes and phases are dependent on the bunch charge, these online tools will provide users with valuable information performing timing experiments.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
The introduction of Silicon Photomultipliers (SiPMs) as single photon sensitive detectors represents a promising alternative to traditional photomultiplier tubes. This is especially true in applications in which it is compulsory to attain magnetic field insensitivity, low photon flux detection, quantum efficiency in the blue region that is comparable to standard photomultipliers, high timing resolution, dimensions comparable to the dimensions of an optical fiber diameters, and low costs. The structure of the SiPM is based on an array of independent avalanche photodiodes (APDs) working in Geiger-mode at a low bias voltage with a high gain. The output signal is proportional to the number of pixels "fired" by impacting photons. The detection efficiency for state-of-the-art devices is in the order of 20% at 500 nm. In this contribution, the measured dark count rates of different SiPMs are compared and the influence of this noise on the real signal is presented. These results are then used to correct the photon count and determine the optimized working parameters for a future beam loss monitor at CTF3/CLIC.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
For destructive beam intensity measurements, electrostatic Faraday cups will be incorporated into the Ultra-low energy Storage Ring (USR) and its transfer lines at the Facility for Low-energy Antiproton and Ion Research (FLAIR). This multipurpose machine will offer both slow and fast extracted beams resulting in a wide range of intensities and varying time structure of the beam. In this contribution we present the particular challenges of measuring the beam intensity in the USR, results from numerical optimization studies, as well as the design of the cup.
MEPhI, Moscow
DESY Zeuthen, Zeuthen
The Photo Injector Test Facility at DESY, Zeuthen site (PITZ) develops electron sources of high brightness beams, required for linac based free electron lasers (FELs) like FLASH or the European XFEL. One of the key issues in electron beam optimization is the minimization of the transverse emittance. The main method to measure emittance at PITZ is a single slit scan technique, implying local beam divergence measurement by insertion of the slit mask at a definite location within the beam and measurements of the transmitted beamlet profile downstream of the slit station. “Emittance Measurement Wizard” (EMWiz) is the program used by PITZ operators for automated emittance measurements. EMWiz combines an acquisition program for beam and beamlet image recording and a postprocessing tool for the analysis of the measured transverse phase space of the electron beam. It provides a way to execute the difficult emittance measurements in an automatic mode and to get a calculated emittance result.
HIT, Heidelberg
GSI, Darmstadt
The transverse emittance of the ion beam at the Heidelberg Ion Therapy Center (HIT) will be measured within the Low Energy Beam Transport (LEBT) using a pepper-pot measurement system. At HIT, two ECR sources produce ions (H, He, C and O) at an energy of 8keV/u with different beam currents from about 80 μA to 2mA. The functionality and components of the pepper-pot device is reviewed as well as the final design and the choice of the scintillator. For that, results from recent beam test at the Max Planck Institute für Kernphysik at Heidelberg are presented. The material investigation was focused on inorganic doped crystal, inorganic undoped crystal, borosilicate glass and quartz glass with the following characteristics: availability, prior use in beam diagnostics, radiation hardness, fast response, spectral matching to CCD detectors.
RIKEN/SPring-8, Hyogo
Hamamatsu Photonics K.K., Hamamatsu-city
JASRI/SPring-8, Hyogo-ken
The SCSS test accelerator, which was constructed to check feasibility of XFEL/SPring-8, is operated for user experiments using stable EUV SASE. This accelerator provides a high quality electron beam with parameters suitable for power saturation of the EUV SASE, such as a bunch length of 300 fs and a peak current of 700 A. Evaluating the parameters is very important to ensure the stable generation of the SASE. The bunch length measurement systems to evaluate the parameters have been developed. The systems use the rf zero phasing method, the EO sampling method with temporal decoding and an 800 nm laser, and the method of observing OTR (near infrared region) by a FESCA-200 streak camera, which are mature technologies. All the measured bunch lengths were about 300 fs (FWHM), which is consistent with the individual methods. The most important result is that the streak camera with optimum tuning directly measured the temporal structure with femtosecond resolution. This presentation briefly introduces a development plan for a higher-resolution streak camera and a beam monitor system for the XFEL, as well as the experimental set-up and results.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
The experimental study of the electron cloud dynamics and mitigation techniques is one of the main objectives of the CESR Damping Ring Test Accelerator (Cesr-TA) program. Shielded pick-up buttons are a relatively simple diagnostic device for obtaining time-resolved information on the electron cloud density. They have been already successfully employed on the SPS at CERN, although with different resolution parameters due to the different type of beams. We present the initial results obtained using such a detector in the Cesr-TA electron/positron ring. By carefully designing the read-out electronics we were able to resolve the individual bunch contribution to the electron cloud formation process along a bunch train and gain useful information on its decay time. Alternatively, by increasing the electronics integration time, we could use our device as a sensitive detector of the average electron cloud density level generated by the passage of a bunch train.
Fermilab, Batavia
A system was developed for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations based on the signal from a single beam-position monitor (BPM) located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, the beam is excited with band-limited noise for about one second, and this was shown not to significantly affect the circulating beams even at high luminosity. The system is used to measure betatron tunes of individual bunches and to study beam-beam effects. In particular, it is one of the main diagnostic tools in an ongoing study of nonlinear beam-beam compensation studies with Gaussian electron lenses. We present the design and operation of this tool, together with results obtained with proton and antiproton bunches.
ELETTRA, Basovizza
The bunch arrival monitor (BAM) for the IV generation synchrotron light source FERMI@Elettra is presented. It is based on an original idea developed at FLASH/DESY, specifically designed and built in-house for FERMI@Elettra. Each BAM station consists of a front-end module, located in the machine tunnel, and of a back-end unit located in the service area. It makes use of the pulsed optical phase reference along with the stabilized fiber link. The front end converts the bunch arrival times into amplitude variations of the optical phase reference pulses distributed over the link. The analogue signal is generated at the e-beam's passage in a broadband pick-up and is sent to the modulation input of an electro-optical modulator (EOM). The back end acquires, synchronously, the amplitude modulated pulses, using a broadband photodiode and a fast analog-to-digital converter. The digitized data is sent to the machine control system for further processing. The dedicated analog-to-digital, conversion processing and communication board, part of the monitor back end, is briefly described. The BAM measurements performed on FERMI@Elettra at 10 Hz are presented.
ANL, Argonne
SLAC, Menlo Park, California
A large-solid-angle Cherenkov detector beam loss monitor has been built and tested as part of the Linac Coherent Light Source machine protection system (MPS). The MPS is used to protect the undulator magnets from high-energy electron beam loss that can lead to demagnetization. Lost primaries create a shower of secondary electrons that transit through the radiator medium. The radiator consists of an Al-coated plate of high-purity, fused silica, formed into a tuning fork geometry that envelopes the beam pipe preceding each undulator. The radiator transports Cherenkov photons via internal reflection through a tapered neck into a compact photomultiplier tube (PMT). A simple model based on line sources summed across image planes is used to calculate the radiator optical coupling efficiency etac as a function of the electron's transverse position. The results are compared for the case of normally incident electrons with a more detailed Monte Carlo random-walk simulation called RIBO. Both analytical and numerical models show etac to be relatively uniform over the full range of transverse positions in the radiator and to be a strong function of surface reflectivity.
DESY, Hamburg
DESY Zeuthen, Zeuthen
Additional beam diagnostics has been installed in the dump line at FLASH in 2009. Its purpose is to prevent damage by long high current electron beam pulses, as happened in autumn 2008, when a vacuum leak occurred near the dump vacuum window. Beam position monitors (BPM), scintillator-based loss monitors and temperature sensors have been installed thus far in the dump area. Additional BPMs and loss monitors have meanwhile been installed. These include a magnetic BPM placed after the vacuum window. Magnetic loops are used in order to prevent the influence of the ions on the pick-up signals. Four ionization chambers, consisting of air-filled tubes, and 4 glass fibers have been installed parallel to the vacuum pipe, along the last 2 m of beam pipe. Beam halo monitors were installed next to the magnetic BPM. These consist of 4 diamond and 4 sapphire sensors operating as solid state ionization chambers. The halo monitors are sensitive to very small losses. These additional diagnostic monitors were commissioned in autumn 2009, and have contributed to the successful run of long pulses with 3-9 mA current and up to 800 microsecond length. Their performance will be summarized in this paper.
Bira, Albuquerque, New Mexico
IUCMB, Bloomington, Indiana
A four-channel magnet-power-supply ramp controller has been designed and deployed at the new ALPHA (Advanced Electron Photon Facility) at the IUCMB (Indiana University Center for Matter and Beams). The first application is a power-supply controller; however, the system is a versatile arbitrary voltage-waveform generator with full DAQ (data acquisition) capabilities that can be used in a variety of beam instrumentation settings. The real-time controller can generate four arbitrary, independently-triggerable ramp profiles. A normalized wave-form array is encoded as a Process Variable array and is uploaded and stored by the real-time controller as required. Each ramp array is clocked out to a 16-bit DAC (Digital to Analog Converter) via a DMA FIFO and built-in FPGA. The duration of the waveform is programmable with a minimum time resolution of 20 usec between profile values. Four bipolar DACs have an output range of ± 10V. Eight digital I/O control bits are allocated for each control channel. Typically, these bits are used to monitor and control the power-supply operational state. The control-system interface uses the EPICS Channel-Access server accessible on Labview RT 2009.
LAL, Orsay
The PHIL (PhotoInjector at LAL: http://phil.lal.in2p3.fr/ ) accelerator is the new LAL (Orsay, France) facility dedicated to test state-of-the-art RF and beam sources technologies used for future electron accelerators. The machine based on 3 GHz RF gun triggered with a 262 nm wavelength laser, delivers a low energy ( E<10 MeV) single pulse electron beam at 5 Hz, with a low charge (0.1 nC) for now. The machine is about 5 meters long, with one direct and one deviated beam line (created after a 60° dipole). This paper describes the current status (first beam in november 2009) and the development of the diagnostics sections of the machine. At present, the machine is equipped by a transverse beam profile monitor based on «YAG:Ce» screen (30 mm diameter and 300 micrometers thick), two BPMs (one "button type" and one "reentrant resonators" type) and two Faraday cups (at the end of each line). The paper will present some preliminary results of the dimension and position of the beam at specific point for different charges and phase, and will present the expected development of the diagnostics of the machine (measurement of mean and energy dispersion, 2D emittance, beam length).
DESY, Hamburg
TEMF, TU Darmstadt, Darmstadt
DESY Zeuthen, Zeuthen
INRNE, Sofia
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
INFN/LASA, Segrate (MI)
RAS/INR, Moscow
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
FNRF, Chiang Mai
MBI, Berlin
The Photo Injector Test facility at DESY Zeuthen site (PITZ) is dedicated to developing and optimizing high brightness electron sources for short wavelength Free-Electron Lasers (FELs) like FLASH and the European XFEL, both in Hamburg (Germany). Since October 2009 a major upgrade has been ongoing with the goal of improving the accelerating components, the photocathode drive laser system, and the beam diagnostics. The previously operated and fully characterized gun was brought to FLASH and will go into operation soon. A gun of the same type is installed now in PITZ. The conditioning has started and the gun will be characterized throughout 2010. A new booster cavity, Cut Disk Structure (CDS), was developed and will be mounted at PITZ in spring 2010. The booster cavity will be able to accelerate electrons above 20 MeV/c and will be suitable for long RF pulses. The most important upgrade of the diagnostics system will be the implementation of a phase space tomography module (PST) consisting of three FODO cells each surrounded by two screen stations. The results of commissioning, gun and booster conditioning and the very first measurements will be reported.
DESY, Hamburg
DESY Zeuthen, Zeuthen
The stability of the photo injector is a key issue for the successful operation of linac based free electron lasers. Several types of jitter can impact the stability of a laser driven RF gun. Fluctuations of the RF launch phase and the cathode laser energy have significant influence on the performance of a high brightness electron source. Bunch charge measurements are used to monitor the stability of the rf gun phase and the cathode laser energy. A basic measurement is the so called phase scan: the accelerated charge downstream of the gun is measured as a function of the launch phase, the relative phase of the laser pulses with respect to the RF. We describe a method which provides simultaneous information on rms jitters from phase scans at different cathode laser energies. Fluctuations of the rf gun phase together with cathode laser energy jitter have been measured at the Photo Injector test facility at DESY in Zeuthen (PITZ). Obtained results will be presented in comparison with direct independent measurements of corresponding instability factors. Dedicated beam dynamics simulations have been done in order to optimize the method performance.
Agilent Technologies SA, Plan-les-Ouates
Agilent Technologies Inc., Loveland
Digital data acquisition in real time applications falls into two categories: digitizing a stream of data without missing a single sample point, and capturing a stream of triggered events without missing a single trigger. Maintaining these data streams over long periods requires an optimized combination of analog signal conditioning, and precise digitization, digital data reduction and high-speed data transfer. This paper describes suggested methods to reduce the amount of measurement data required, reduce the amount of that data that is to be transferred (to a measurement where possible), and then transfer this reduced data in the most rapid fashion. Our approach uses a combination of hardware, firmware and software elements that are designed to work together, optimizing performance and managing the data bottlenecks. New hardware standards and architectures are discussed that improve the capabilities of today's technologies, providing access to higher data and measurement flux. Applications presented in this paper include high trigger rate capture for beam steering and fill pattern monitoring in charged particle accelerators.
RIKEN Nishina Center, Wako
A highly sensitive beam current (position) monitor with a high Tc (Critical Temperature) SQUID (Superconducting QUantum Interference Device) and current sensor – the HTc-SQUID monitor – has been developed for the RIBF (RI Beam Factory) in RIKEN. In the present work, the HTc-SQUID monitor allows us to measure the DC of high-energy heavy-ion beams nondestructively in such a way that the beams are diagnosed in real time and the beam current extracted from the cyclotron can be recorded without interrupting the beam user's experiments. Both the HTc magnetic shield and the HTc current sensor were dip-coated with a thin layer of Bi-Sr-Ca-Cu-O (2223-phase, Tc 106 K) on 99.9 % MgO ceramic substrates. Unlike other existing facilities, all these HTS fabrications are cooled by a low-vibration pulse-tube refrigerator. These technologies enable us to downsize the system. Last year, aiming at the practical use, the HTc-SQUID monitor was installed in the RIBF. As a result, a 1 uA Xe beam intensity (50 MeV/u) was successfully measured with a 100 nA resolution. We will report the present status of the facility, the details of the monitor system and the results of the beam measurement.
DESY, Hamburg
The European XFEL is a 4th generation synchrotron radiation source, currently under construction in Hamburg. Based on different Free-Electron-Laser and spontaneous sources, driven by a 17.5 GeV superconducting accelerator, it will be able to provide several user stations with photons simultaneously. Due to the superconducting technology high average as well as peak brilliance can be produced. Flexible bunch pattern will allow for optimum tuning to the experiments demands. This paper will present the current planning of the electron beam diagnostics. An overview of the entire system will be given, as well as detailed insight into the main diagnostic systems, like BPM, charge and transmission diagnostics, beam size and beam loss monitor systems.
PSI, Villigen
JLAB, Newport News, Virginia
Electro Optical (EO) sampling is a promising non-destructive method for measuring ultra short (sub-ps) electron bunches. The FEMTO slicing experiment at the Swiss Light Source modulates about 1 pC of the 4-nC electron bunch longitudinally. The coherent synchrotron radiation (CSR) emitted by this substructure was sampled by 100 fs long pulses from an Yb fiber laser in EO crystals of different materials (GaP, ZnTe). The broadening of this ps long structure over several turns of the synchrotron could be measured with sub-ps resolution.
UMD, College Park, Maryland
MPI-K, Heidelberg
Cockcroft Institute, Warrington, Cheshire
We have developed a technique that employs a digital micro-mirror array to produce an image of the halo of an electron beam with enhanced dynamic range. Light produced by the beam intercepting a phosphor screen is first imaged onto the array; an adaptive mask is created and applied to filter out the beam core; and the result is reimaged onto an intensified CCD camera. We describe the optics used, the masking operation and preliminary results of experiments we have performed to study beam halo at the University of Maryland Electron Ring (UMER).
ORNL, Oak Ridge, Tennessee
Beam Loss Monitors are common devices used in hadron and lepton accelerators. Depending on accelerator specifics, BLMs could be just diagnostics or could play an essential role in the Machine Protection System (MPS). This tutorial discusses different types of BLMs and their applicability to different accelerators. It covers traditional BLMs like ionization chambers and scintillator-based devices, and also less common techniques like those based on fiber optics and avalanche diodes. The tutorial gives an overview of the underlying physics involved in beam loss detection, and recent advances in computer simulation of particle interaction with matter helpful for BLM modeling. Options for signal processing electronics are described, as well as interfaces to both the control system and the MPS.
PSI, Villigen
The 9th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2009) was hosted by Paul Scherrer Institute (PSI) and took place at the Hotel Mercure Conference Center in Basel, Switzerland, May 25-27, 2009. A record number of 210 registered participants contributed to an exciting scientific program with ten invited talks, fourteen contributed orals and 115 poster contributions. In this talk, I will provide an overview of the various fields of beam instrumentation discussed during the workshop. A number of highlights from the scientific program have been selected, illustrating some of the outstanding achievements in accelerator diagnostics, presented at DIPAC 2009.