DESY, Hamburg
The former electron and proton preaccelerator PETRA at DESY is currently reconstructed and will be converted into the most brilliant storage-ring-based X-ray source worldwide called PETRAIII. The commissioning is scheduled for January 2009. It will operate at 6 GeV with 100 mA stored current and with a design emittance of 1 nm rad. Top-up operation is foreseen right from the beginning to reduce changes in heat-load and thermal drifts to a minimum,. Suitable beam diagnostic instrumentation and machine protection systems have to be established to guarantee the low emittance, a sub-micron beam stability as well as a save machine operation. To ensure a very high availability of the beam in top-up mode, the injector and preaccelerator diagnostic systems will be refurbished as well. A complete overview of the instrumentation and their latest developments to achieve these goals will be presented.
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.
JLAB, Newport News, Virginia
CNU, Newport News, Virginia
Beamline components used for diagnostic elements often rely on thermal stabilization, continual physical maintenance (ie. tuning), and frequent beam-based calibrations to maintain specified performance. Direct-sequence spread spectrum (DSSS) pilot tones injected into a particular element and combined with the beam-derived signal can subsequently be separated and used to assess performance degradation. In addition, the DSSS tone can be used as a real-time calibration signal, without interference to the intended diagnostic signal. This paper demonstrates such a technique in the design of a Beam Current Monitor downconverter system, as an intended upgrade to the CEBAF Beam Loss Accounting system. A brief spread-spectrum primer is included, as well as a description of appropriate spreading codes and their generation.
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.
LBNL, Berkeley, California
The Advanced Light Source Transverse Feedback System currently consists of a refrigerator sized analog delay line system. The new system is the 2nd generation Transverse Feedback System, derived from work done for PEP-II in 2004. It uses the latest generation Virtex-5 FPGA, and has 12-bit ADCs and DACs for bunch-bunch feedback at 500MHz. In addition, this system provides networked capability for setup and diagnostics.
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.
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.
GSI, Darmstadt
HIT, Heidelberg
The Heidelberg Ion Therapy Center (HIT) for tumor treatment is presently being commissioned using the beam diagnostic devices designed and produced by the GSI beam diagnostic department. To fulfil the requirements for hadron therapy a high-resolution analysis of the particle distribution within the slowly extracted beam is necessary. We present spill-structure measurements for carbon ion beams at energies from 88 MeV up to 430 MeV, also with respect to the spill-pause and abort functionality of the rf-knock-out extraction method. The spill-structure, as measured by internal intercepting ionization chambers (IC) is compared to data recorded with external beam loss monitors (BLM). The high-resolution data acquisition system with sampling rates up to 10 kSa/s and the connected detectors are described and the achievements during the commissioning phase are discussed.
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.
Fermilab, Batavia
ANL, Argonne
During the commissioning of the LCLS injector in 2007, unexpected enhancements of the signals in the visible light optical transition radiation (OTR) monitors occurred after compression in a chicane bunch compressor. These were attributed to a microbunching effect of some kind. Explorations of such effects have now been performed on the Advanced Photon Source (APS) linac. The APS injector complex includes an option for photocathode (PC) gun beam injection into the 450-MeV S-band linac. At the 150-MeV point, a 4-dipole chicane was used to compress the micropulse bunch length from a few ps to sub-0.5 ps (FWHM). Noticeable enhancements of the OTR signal sampled after the APS chicane were observed. A FIR CTR detector and interferometer were used to monitor the bunch compression process and correlate the appearance of localized spikes of OTR signal (5-10 times brighter than adjacent areas) within the beam image footprint. We have done spectral dependency measurements at 375 MeV with a series of band pass filters centered from 400 to 700 nm and observed a broad-band enhancement in these spikes. Discussions of the possible mechanisms will be presented.
ANL, Argonne
A cw tune measurement system for the IPNS RCS is described. The pinger magnets are energized by a solid-state, transformer-coupled power supply operating at 30 Hz. In its present configuration, the power supply provides a 160-A pulse to a pair of series-connected, single-turn ferrite magnets. The magnet pair drive separately x- and y-plane orbit bumps in the h=1 beam. The dipole oscillations generated in the beam are sensed with pairs of split-can, "pie" electrodes. Raw signals from the H and V electrodes are carried on matched coax-cables to 0/180-degree combiners. The output difference signals are recorded with gated spectrum analyzers. Bunch circulation frequency varies from 2.21 MHz at injection to 5.14 MHz at extraction. With a fixed frequency span of 24 MHz, between 4 and 10 bunch harmonics and sidebands (SBs) are present in the difference spectra. Software has been developed to use the multi-harmonic SBs present over the span to improve the accuracy of the tune measurements. The software first identifies and then fits the multiple SBs to determine the tune. Sweeping the beam across the momentum aperture provides a method for measuring the chromaticity.
ANL, Argonne
The Advanced Photon Source (APS) injection booster is a 7-GeV electron synchrotron with a ramping time of 220 ms and a repetition rate of 2 Hz. A real-time tune measurement system is needed in order to monitor and possibly correct tune drift during the 220-ms energy ramp. Such a drift may occur during user beam operations, especially during top-up operations, and results in shot-to-shot charge fluctuations. We designed and developed a new FPGA-based system that pings the beam at variable intervals and measures booster tune. A prototype system has been built and tested, and it has achieved the specified time resolution of 2 ms and a tune resolution of better than 0.002. This report describes the design and main parameters, test results from our preliminary commissioning, and application of such a system in ramping correction.
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.
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.
KIP, Heidelberg
GSI, Darmstadt
The development of new particle accelerators with unprecedented beam characteristics has always driven the need for an intense R&D program in diagnostic techniques. The successful operation of these machines is finally only possible with an adequate set of beam instrumentation. DITANET is a large European network between several research centres, Universities, and partners from industry that aims for the development of beyond-state-of-the-art diagnostic techniques for future accelerator facilities. This includes research projects focusing on beam profile, current, and position measurements, as well as on particle detection techniques and related electronics. A particular focus of the consortium is the training of young researchers in this multi-disciplinary field and to thus prepare them for their future careers in academia or industry. This contribution will introduce the network participants, present the general structure of DITANET, and give an overview of its research and training activities.