YerPhI, Yerevan
Thermal sensors based on the vibrating wire principle are distinguished by high accuracy and stability. An important advantage of these sensors is that they produce a frequency signal that can be transferred large distances without disturbance. Original vibrating wire sensors and monitors for the measurement of beam transversal characteristics of charged-particle and photon beams are described. By means of these devices, measurements of an electron beam in the Yerevan synchrotron, a proton beam at PETRA (DESY), and a hard x-ray undulator beam at the APS (ANL) have been performed.
LBNL, Berkeley, California
Historically, progress in high-energy physics has largely been determined by development of more-capable accelerators. This trend continues with the imminent commissioning of the Large Hadron Collider and the worldwide development effort toward the International Linear Collider. Looking beyond these machines, there are two scientific areas ripe for further exploration–the energy frontier and the precision frontier. To explore the energy frontier, two approaches toward multi-TeV beams are being studied, an electron-positron linear collider based on a novel two-beam powering system (CLIC), and a Muon Collider. Work on the precision frontier involves accelerators with very high intensity, including a proposed Super-B Factory and a muon-based Neutrino Factory. Without question, one of the most promising approaches is the development of muon-beam accelerators. Such machines would substantially advance the state of the art in accelerator design and, to reap their scientific potential, require sophisticated instrumentation to characterize the beam and control it with unprecedented precision.
SLAC, Menlo Park, California
Stanford University, Stanford, Califormia
The LCLS accelerator produces a 14GeV beam with a normalized emittance on the order of one micron RMS, and peak current exceeding 1000 Amps. The design of the beam measurement system relied heavily on optical transition radiation profile monitors, in conjunction with transverse cavities, and conventional energy spectrometers. It has been found that the high peak currents, and small longitudinal phase space of the beam generate strong coherent optical emission that prevents the use of OTR or other prompt optical diagnostics, requiring the use of wire scanners or fluorescent screen based measurements. We present the results of the beam measurements, measurements of the coherent optical effects, and future plans for diagnostics.
IHEP Beijing, Beijing
As the upgrade project of Beijing Electron Positron Collider (BEPC), BEPCII will still serve both high energy physics experiments and synchrotron radiation applications. The storage ring of BEPCII consists of electron ring (BER), positron ring (BPR) and synchrotron radiation ring (BSR). Up to now, we have completed two stages run. The first stage run started on Nov. 13, 2006 by using conventional magnets instead of superconducting (SC) magnets in the interaction region (IR). The second stage operation started on Oct. 24, 2007 by using SC magnets and without BESIII detector. In this paper, we will present the progress of the BEPCII storage ring diagnostics system along with the BEPCII commissioning, such as how Libera BPM has been used for the BPR first turn measurement and the injection residual orbit research of BER; COD measurement can satisfy the resolution requirement for the beam-beam scan in the IR and for the slow orbit feedback; BCM can help us on the different injection pattern; and the TFB system is important to suppress the strong multibunch instabilities when the higher beam current run. The tune meters and the beam-loss monitors are also described in this paper.
LBNL, Berkeley, California
CERN, Geneva
SLAC, Menlo Park, California
Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave which is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.
Royal Holloway, University of London, Surrey
Lasers are increasingly being employed in particle beam diagnostics. Laser-based techniques are attractive because they are essentially non-invasive to the beam under test and can not be destroyed by it. They also have the potential to be extremely fast. Uses include transverse beam profile measurement at electron machines using the Compton effect,and at proton machines using laser-ionization of H- beams. An introduction is provided to Gaussian beam propagation and how this affects the laser properties and final focus optics needed for the various applications. Recent applications and results from ongoing research projects will be reviewed, with particular emphasis on the "laser-wire" systems recently employed at the PETRA and ATF machines.
LBNL, Berkeley, California
The recent availability of ultrashort (femtosecond) electron bunches is accompanied by the necessity for ultrafast bunch characterization, preferably in a single-shot manner. The duration of the bunch, its precise charge profile, and/or its arrival time, are parameters relevant to accelerator performance and experimental applications. The electro-optic (EO) technique has proven ideal as a single-shot femtosecond bunch diagnostic. The technique is based on the polarization modulation of a laser pulse by either the self-fields of the electron bunch, or by the coherent radiation emission of the bunch. The technique is limited in time resolution only by the laser pulse length (<10's of fs). We will present an overview of the several variations of existing EO configurations (analysis in spatial, temporal, or frequency domain), each with its own set of advantages and limitations. Both modeled and experimental results will be presented. Emphasis is put on results on electron bunches from the 10-TW-laser-based Laser Wakefield Accelerator of the LOASIS group at LBNL. These bunches were found to have a duration of 45 fs. Future improvements on the EO technique will be discussed.
Fermilab, Batavia
We review the sources and effects of radiation damage in silicon-based particle detectors and electronics. Recent R&D has established basic mechanisms for bulk damage in silicon and several possible mitigation strategies. We will dicsuss radiation damage effects on CMOS, Silicon-On-Insulator, and bipolar technologies as well as mitigation strategies.
NewPath, Salt Lake City, Utah
We have shown that a group of sinusoidally-wound coaxial toroids can be used to determine the transverse distribution of a time-dependent current that passes through their common aperture. The current is expressed in a basis of chapeau (pulse) functions over an array of pixels, and matrix methods are used to determine the current in each pixel from measurements of the voltages that are induced on the toroids. Optimum configurations of pixels are used, for which the condition number of the matrix is bounded by the number of pixels. For example, with a resolution of 50 pixels, the fractional errors in determining the current at each pixel are approximately 50 times the fractional errors in the measurements of the induced voltages as well as imperfections in the fabrication of the toroids and their placement. Our algorithms were tested numerically by specifying the currents, calculating the voltages that would be induced on the toroids, adding Gaussian noise to these voltages, and then using the algorithms to calculate the currents from the simulated voltage measurements. These simulations confirm that the condition number of the matrix is bounded by the number of pixels.
NewPath Research L.L.C., Salt Lake City
NewPath, Salt Lake City, Utah
We have shown that a group of sinusoidally-wound non-ferrous coaxial toroids can be used to determine the transverse distribution of a time-dependent current that passes through their common aperture. A single current filament requires one uniformly-wound toroid, and two others having turn densities proportional to the sine and cosine of the azimuthal coordinate. Three simple algebraic equations give the magnitude and phase of the current and its position in terms of the voltages induced on the three toroids, and there is no ill-conditioning. Two current filaments require two additional toroids with turn densities proportional to the sine and cosine of two times the azimuthal coordinate, and the solution may be obtained by using steepest descent to minimize the residuals. Ill-conditioning makes it impractical to use more than two currents. We have tested our algorithms numerically by specifying the magnitudes and phases of the currents and their locations, calculating the voltages that would be induced on the toroids, adding Gaussian noise to these voltages, and then using the algorithms to calculate the currents and their locations from the simulated voltage measurements.
IHEP Beijing, Beijing
A DC Current Transformer (DCCT) as a standard diagnostic system for beam current plays an important role in BEPCII, the upgrade project of the Beijing Electron Positron Collider. Two DCCTs are operated in the BEPCII storage ring now, separated in electron ring and positron ring, used to monitor the beam current, the beam injection rate and the beam loss rate, meanwhile to help to calculate the beam lifetime. In this paper, the mechanical structure design, readout system and data processing are presented. The progress of DCCTs on each step of BEPCII commissioning, such as improving the beam lifetime，and solution of background noise, are also included.
BESSY GmbH, Berlin
FZD, Dresden
MBI, Berlin
A superconducting RF (SRF) photoelectron injector is currently under commissioning by a collaboration of BESSY, DESY, FZD and MBI. The project aims at the design and setup of a continuous-wave (CW) SRF electron injector including a diagnostics beamline for the ELBE FEL and to address R&D issues of high brightness CW injectors for future light sources such as the BESSY FEL. The layout and realization of the diagnostics beamline for the electron beam is presented including systems to monitor the momentum, charge, transverse emittance and bunchlength in various operation modes of the injector.
Northern Illinois University, DeKalb, Illinois
Electrons crossing the boundary between different media generate bursts of transition radiation. In the case of bunches of N electrons, the radiation is coherent and has an N-squared enhancement at wavelengths related to the longitudinal bunch distribution. This coherent transition radiation has therefore attracted attention as an interceptive charged particle beam diagnostic technique. Many analytical descriptions have been devised describing the spectral distribution generated by electron bunches colliding with thin metallic foils making different simplifying assumptions. For typical bunches having lengths in the sub-millimeter range, measurable spectra are generated up into the millimeter range. Analysis of this THz radiation is performed using optical equipment tens of millimeters in size. This gives rise to concern that optical diffraction effects may spread the wavefront of interest into regions larger than the optical elements and partially escape detection, generating a wavelength-dependent instrument response. In this paper we present a model implementing vector diffraction theory to analyze these effects in bunch length diagnostics based on coherent transition radiation.
UMD, College Park, Maryland
Intense charged particle beams are of great interest to many wide areas of application ranging from high-energy physics, light sources and energy recovery linacs, to medical applications. The University of Maryland Electron Ring (UMER) is a scaled model to investigate the physics of such intense beams. It uses a 10 keV electron beam along with other scaled beam parameters that model the larger machines but at a lower cost. Multi turn operation of the ring (3.6 m diameter) has been achieved for highly space charge dominated beams. Such, multi-turn operation requires a non-intercepting diagnostic for measuring the transverse beam size. Localized density or velocity variations on a space-charge dominated beam travel as space charge waves along the beam. The speed at which the space charge waves separate from each other depends on the beam current, energy and g-factor. In this work, we propose a diagnostic using deliberately-induced space charge waves to measure the beam size with multi-turn operation. We present and compare experimental results with self-consistent simulation.
Fermilab, Batavia
We present preliminary measurements of the electron bunch lengths at the Fermilab A0 Photoinjector using a Martin-Puplett interferometer on loan from DESY. The photoinjector provides a relatively wide range of bunch lengths through laser pulse width adjustment and compression of the beam using a magnetic chicane. We present comparisons of data with simulations that account for diffraction distortions in the signal and discuss future plans for improving the measurement.
ELETTRA, Basovizza
FERMI@Elettra is a seeded FEL source, currently under construction at the Elettra Synchrotron Light Laboratory. On-line single shot and non destructive longitudinal bunch profile and bunch arrival time measurements are of great importance for this type of FEL source. These measurements will be performed by means of two Electro Optic Station (EOS) to be installed just upstream each of the two undulator chains. The paper describes the EOS stations design based on the spatial conversion scheme tested at SPPS and FLASH, and proposed for LCLS. The EOS will make use of two laser sources: a fiber laser at 780nm and the seed laser oscillator. A set of ZnTe and GaP crystal of different thicknesses will allow for flexibility in choosing high signal or high resolution configurations. The maximum resolution is expected to be of about100 fsec. The time profile mapped in a spatial laser profile will be acquired by a gated Intensified CCD. Calculations are presented for the expected EO signal and THz pulse broadening and distortion during propagation in the crystals.
INFN/LNF, Frascati (Roma)
LAL, Orsay
roma3, Rome
INFN-Roma, Roma
INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)
The test of the crabbed waist scheme, undergoing at the Frascati DAΦNE accelerator complex, needs a fast and accurate measurement of the absolute luminosity, as well as a full characterization of the background conditions. Three different monitors, a Bhabha calorimeter, a Bhabha GEM tracker and a gamma bremsstrahlung proportional counter have been designed, tested and installed on the accelerator at the end of January 2008. Results from beam-test measurements, comparison with the Monte Carlo simulation and preliminary data collected during the SIDDHARTA run are presented.
INFN/LNF, Frascati (Roma)
INFN-Roma, Roma
The DAΦNE Beam Test Facility (BTF), initially optimized to produce single electrons and positrons in the 25-750 MeV energy range, can now provide beam in a wider range of intensity, up to 1010 electrons/pulse. The facility has been also equipped with a system for the production of tagged photons, and the possibility of photo-production of neutron is under study. Different diagnostic tools have been developed and are available for high-energy users and accelerator community to monitor and check beam and device under test performance. The main results obtained, the performance and the most significant characteristics of the facility diagnostics and operation are presented, as well as the users experience collected during these years of operation.
KEK, Ibaraki
Recent high-intensity machines with a multi-bunched beam demand bunch-by-bunch beam diagnostics. Especially in a colliding machine such as KEKB, the beam-beam effect is one of the main issues from the viewpoint of beam dynamics. Recently, KEKB achieved an effective head-on collision by using of crab cavities and gained a higher specific luminosity. A gated beam-position monitor, being capable of measuring the beam phase as well as the transverse position of a specific bunch in a bunch train, has been developed and is used to measure a beam-beam kick at KEKB. The monitor detects the beam position with a resolution of a few micrometers. The monitor demonstrated the effect of the crab cavities and estimated the effective horizontal beam size at the interaction point from a linear part of a beam-beam kick. Moreover, the monitor detected a displacement of the horizontal beam position along a bunch train under the crabbing collision. We estimate that the horizontal displacement is caused by an asymmetric kick of the crab cavities, which is based on a bunch-by-bunch phase modulation due to transient beam loading.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
ALBA synchrotron light source is a 3rd generation light source being constructed by the CELLS consortium near Barcelona, Spain. Orbit correction system will be based on the Libera Brilliance electronics and its goal will be the stabilization of the beam at the submicron level. Important parameters to reach such corrections have been measured and are reported in this document, like electronics resolution, beam current dependence, latency (among others). Comparison of the two different Libera products offered by the company (Libera Electron and Libera Brilliance) is also reported in order to analyze the benefits of choosing Libera Brilliance.
UMD, College Park, Maryland
ANL, Argonne
We have used an optical diffraction-transition radiation interferometer (ODTRI) in a transmission mode to measure the divergence of the low energy 8 MeV ANL-AWA electron beam. The interferometer employs a metallic micromesh first foil, which is used to overcome the inherent limitation due to scattering in the solid first foil of a conventional OTR interferometer, and an optically transparent dielectric foil. The interferences of forward directed ODR from the mesh and radiation from the dielectric foil is observed in transmission. This geometry allows a small gap between the foils (0.9 mm), which is required to observe fringes from two foils at low beam energies. The measured beam divergence is in a good agreement with that obtained using the standard pepper pot technique and simulation code calculations. ODTRI measurements indicate that a single Gaussian distribution is insufficient to describe the angular distribution of the measured beam and that a second Gaussian beam faction or halo beam component is required to fit the data.
BNL, Upton, Long Island, New York
A new, ultra-bright 3rd generation light source, the NSLS-II Project, is planned to be built at Brookhaven National Laboratory. The light source being developed will have unprecedently small beam horizontal emittance and will provide the radiation sources with a brightness of 3x1021 photons/sec/0.1%BW/mm2/mrad2. In this paper we present the detailed specifications and a comprehensive description of the planned beam instrumentation system and the first results of the ongoing instrumentation R&D activities on beyond state-of-the-art sub-systems.
JLAB, Newport News, Virginia
In this contribution we present results of the timing jitter and energy modulation of the electron beam in the driver energy recovery linac (ERL) for the JLab FEL. Measurements techniques are described. The effects of the timing jitter and the energy modulation on the performance of the FEL are discussed.
Fermilab, Batavia
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
ANL, Argonne
We have previously experimentally observed and modeled the near-field optical diffraction radiation (ODR) generated by a 3-nC micropulse of a 7-GeV electron beam at the Advanced Photon Source (APS). Due to the high gamma of ~14,000, the scaling factor of γλ/2π was about 1.4 mm for 0.628 um radiation. Thus, a standard CCD camera was sufficient for imaging at an impact parameter of 1.25 mm. The extension of this technique to γ 1000 is challenged by the ·1014 reduction in visible light photon production compared to the APS case. We discuss the feasibility of monitoring at a new Fermilab facility a high average current linac beam of 3000 times more charge in a video frame time and with a more sensitive 12- to 16-bit camera. Numerical integrations of our base model show beam size sensitivity for ±20% level changes at 200- and 400-um base beam sizes. We also evaluated impact parameters of 5 σy and 12 σy for both 800-nm and 10-um observation wavelengths. The latter examples are also related to a proposal to apply the technique to an ~ 0.94 TeV proton beam, but there are trades on photon intensity and beam size sensitivity to be considered at such gammas.
Fermilab, Batavia
The Fermilab A0 photoinjector facility consists of an L-band photocathode (PC) gun and a 9-cell SC rf accelerating structure which combine to generate up to 16-MeV electron beams. The drive laser operates at 81.25 MHz, although the micropulse structure is usually counted down to 9 MHz. Bunch length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a single-sweep module of the Hamamatsu C5680 streak camera system with an intrinsic shot-to-shot trigger jitter of 10 to 20 ps. We have upgraded the camera system with the synchroscan module tuned to 81.25 MHz and a phase-locked delay box to provide synchronous summing capability with less than 1.5 ps FWHM trigger jitter. This allows us to measure both the UV laser pulse train at 244 nm and the e-beam via optical transition radiation (OTR). Due to the low OTR signals, we typically summed over 50 micropulses with 1 nC per micropulse. We also identified a significant e-beam micropulse elongation effect from 10 to 30 ps (FWHM) as the charge was varied from 1 to 5 nC. This is attributed to space-charge effects in the PC gun as reproduced by ASTRA calculations.
CEA, Gif-sur-Yvette
In the IFMIF-EVEDA framework, a high deuteron beam intensity (125 mA - 9 MeV) accelerator will be built and tested at Rokkasho (Japan). The development of this accelerator is shared between France, Italy and Spain. France (CEA-Saclay) and Spain (Ciemat-Madrid) are responsible of the beam instrumentation from the RFQ to the beam dump. One of the most challenging detectors is the Beam Transverse Profile Monitor (BTPM), and the Saclay group decided to investigate such a monitor based on residual gas ionisation. In order to study the feasibility, we plan in a first step to built a prototype. This monitor use a high electric field to drive the products (electrons and ions) of ionisation to resistive micro-strips. At first sight, no amplification is necessary! This prototype will be tested in the IPHI high intensity (100 mA) proton beam at Saclay to answer this question in particular, and to check the feasibility in general.
Diamond, Oxfordshire
Top up is becoming more and more a standard mode of operation for synchrotron light sources. Although it brings a very stable source in terms of position and intensity, the regular injections potentially perturb the beam. In order to investigate the perturbation of the beam from imperfections of the injection kickers (i.e. non-closure of the bump), we use an X-ray pinhole camera equipped with a fast CMOS-sensor giving a rate of up to 3200 frames per second to monitor the image of the beam. The analysis of the observed beam size as well as position allows quantifying the perturbation from the kickers that can be seen on beamlines. In addition we compare the observed motion to bunch-by-bunch position data recorded in both vertical and horizontal planes, which reveals to be very complementary.
UMD, College Park, Maryland
I review the state of the art of diagnostics based on transition, diffraction and Smith Purcell radiation in the optical to millimeter wave band, which are currently being used to measure the transverse and longitudinal parameters of charged particle beams. The properties and diagnostic capabilities of both the incoherent and coherent forms of each type of radiation are described. Examples of TR, DR and SPR diagnostics for electron and proton beams are presented.
CERN, Geneva
Built at CERN by an international collaboration, the CLIC Test Facility 3 (CTF3) aims at demonstrating the feasibility of a high luminosity 3 TeV e+-e- collider by the year 2010. The CLIC project is based on the so called ?two-beam acceleration scheme? where the RF accelerating power is provided by a high current high frequency electron beam. The required performances put high demands on the diagnostic equipment and innovative monitors have been developed during the past years. This paper gives an overview of the instrumentation developed at CTF3 with a special emphasis on short bunch length measurements, high precision beam position monitors, high dynamic range beam imaging system and high precision beam phase measurements.
JLAB, Newport News, Virginia
CASA, newport news
Fermilab, Batavia
An optical diffraction radiation (ODR) diagnostic station was recently designed and installed on a CEBAF transfer beam line. The purpose of the setup is to evaluate experimentally the applicability range for an ODR based non interceptive beam size monitor as well as to collect data to benchmark numerical modeling of the ODR. An extensive set of measurements were made at the electron beam energy of 4.5 GeV. The ODR measurements were made for both pulsed and CW electron beam of up to 80 uA. The wavelength dependence and polarization components of the ODR were studied using a set of insertable bandpass filters (500 nm short and 500 nm long pass filter) and polarizers (horizontal and vertical). The typical transverse beam size during the measurements was ~150 microns. Complete ODR data, wavelength and polarization, were recorded for different beam sizes and intensities. The beam size was also measured with an optical transition radiation (OTR) (using the surface of the ODR converter) and wire scanner located next to the ODR station. In this contribution we describe the experimental setup and present the results of the measurements with the comparison to the numerical simulations.
LBNL, Berkeley, California
The Advanced Light Source (ALS) in Berkeley was the first third generation light source ever built, and since 1993 has been in continuous and successful operation serving a large community of users in the VUV and soft x-ray community. During these years the storage ring underwent through several important upgrades that allowed to maintain the performances of this veteran facility at the forefront. The ALS beam diagnostics and instrumentation have followed a similar path of innovation and upgrade and nowadays include most of the modern and last generation devices and technologies that are commercially available and used in the recently constructed third generation light sources. In this talk we will not focus on such already widely known systems, but we will concentrate in the description of some measurements techniques, instrumentation and diagnostic system specifically developed at the ALS and used during the last few years.