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.
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.
ANL, Argonne
YerPhI, Yerevan
A 5-wire vibrating wire monitor (VWM005) was developed and tested at the Advanced Photon Source (APS). The sensor was mounted on the outboard side of a bending-magnet synchrotron radiation terminating flange in sector 37 of the APS storage ring. The parallel wires were separated vertically by 0.5 mm; however, due to the possibility of rotation about a horizontal axis, the effective distance between the wires was reduced by 30%. To increase the response speed, the sensor was installed in air, resulting in a step response time of less than one second. Due to the extreme sensitivity of the detector, the very hard x-ray component of synchrotron radiation was successfully measured after its passage through the terminating flange.
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.
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.
LANL, Los Alamos, New Mexico
The LANSCE accelerator facility utilizes 110 wire scanner devices to monitor the accelerator's charged particle beam. The LANSCE facility's existing wire scanner control systems have remained relatively unchanged since the LANSCE accelerator became operational in the 1970's. The evolution of motion control technologies now permits the development of a wire scanner motion control system that improves in areas of energy efficiency, precision, speed, resolution, robustness, upgradeability, maintainability, and overall cost. The purpose of this project is to research the capabilities of today's motion control products and analyze the performance of these products when applied to a wire scanner beam profile measurement. This experiment's test bed consists of a PC running LabVIEW, a National Instruments motion controller, and a LEDA (Low Energy Demonstration Accelerator) actuator. From this experiment, feedback sensor performance and overall motion performance (with an emphasis on obtaining maximum scan speed) has been evaluated.
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.
KIP, Heidelberg
CERN, Geneva
GSI, Darmstadt
Synchrotron radiation has proven to be a flexible and effective tool for measuring a wide range of beam parameters in storage rings, in particular information about the longitudinal beam profile. It is today an established and widely used diagnostic method providing online measurements and thus allowing for continuous optimization of the machine performance. At the CLIC Test Facility (CTF3), synchrotron radiation is routinely used at a number of diagnostic stations, in particular in the Delay Loop and the Combiner Ring. Measurements with both standard CCDs and a streak camera showed the wide range of possible applications of this method, including determination of inter-bunch spacing, charge per pulse and monitoring of the manipulation of the effective path length by an undulator. This contribution first addresses the critical points during the design phase of long optical lines with lengths of more than 30 meters as they had to be realized at CTF3. Second, a summary of the present installations is given and results from measurements are shown.
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.
GSI, Darmstadt
LBNL, Berkeley, California
TU Darmstadt, Darmstadt
Non-intercepting Beam Induced Fluorescence (BIF) monitors determine transversal beam profiles by observation of fluorescence light originating from excited residual gas molecules. Thus they are an alternative to conventional intercepting devices. Single photon counting is performed using an image intensified digital CCD camera. We investigated the BIF process in the energy range of 7.7 keV/u to 750 MeV/u in residual nitrogen. Experiments at low beam energies were performed at a Marx-accelerator (NDCX) at Berkeley Lab whereas mid and high energy experiments were carried out at GSI accelerators. Especially in the vicinity of targets the neutron-generated radiation level limits the monitor's signal to background ratio. Therefore the radiation background was investigated for different ion species and particle energies. Background simulations using a Monte Carlo transport code are compared to experimental data measured with scintillators, thermo luminescence detectors and the BIF monitor. Alternative image intensifier techniques are presented as well as shielding concepts. Furthermore the dynamics of ionized nitrogen molecules in the electric field of intense ion beams is 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.
BNL, Upton, Long Island, New York
NSLS-II Storage Ring will provide ultrabright radiation sources with extra small sizes of the circulating electron beam. The beam dimensions will be monitored with a pinhole camera. In this paper we discuss possible design and ultimate achievable resolution of the system. The modeling is based on the SRW code as well as numerical calculations using MATLAB.
Fermilab, Batavia
Several complementary transverse emittance monitors have been developed and used at the Fermilab accelerator complex. These include Ionization Profile Monitors (IPM's), Flying Wires, Schottky detectors and a Synchrotron Light Monitor. Mechanical scrapers have also been used for calibration purposes. This paper describes the various measurement devices by examining their basic features, calibration requirements, systematic uncertainties, and applications to collider operation. A comparison of results from different kinds of measurements is also presented.
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.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
Low cost bunch-by-bunch longitudinal diagnostics is a key issue of modern accelerators. To face up this challenging demand mid-IR compact uncooled PC HgCdTe detectors have been characterized at DAΦNE. These devices were used to monitor the emission of e- bunches. The first experiment allowed to record 2.7 ns long bunches in the e- ring with a FWHM of a single pulse of about 600 ps. To improve diagnostics at DAΦNE an exit port on a bending magnet of the e+ ring has been set-up to monitor the positron bunch structure. The front-end of this port includes an HV chamber hosting a gold-coated plane mirror that collects and deflects the radiation through a ZnSe window. After the window a simple optical layout in air will focus the radiation on IR detectors. The instrumentation will allow comparison in the ns time domain between the two rings and to identify and characterize bunch instabilities. To improve the established performances new faster IR photovoltaic detectors with sub-ns response times are under characterization. In this work we will present the actual status of the 3+L experiment and new measurements obtained with photovoltaic detectors on the e- ring.
CERN, Geneva
Field Programmable Gate Arrays (FPGAs) have become a central enabling technology for the design of fast digital signal processing systems. This tutorial starts with an introduction to digital signal processing and a comparison with analog techniques. We then treat the problem of choosing between the two key technologies for digital systems: Digital Signal Processors (DSPs) and FPGAs. Once the advantages of FPGAs for very demanding systems have been laid out, we go on with a survey of digital design techniques of general nature, followed by tips and tricks more directly applicable to FPGA implementations. Digital signal processing in FPGAs typically uses a fixed-point number representation. We explain how different fixed-point arithmetic operations can be implemented, and the trade-offs regarding speed, silicon area and precision. Finally, all the concepts are applied to a set of examples in beam instrumentation.
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.