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.
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.
GSI, Darmstadt
Scintillation screens are widely used for qualitative beam profile monitoring, but precise profile measurements yields ambivalent results for high beam currents. Moreover, these screens are an essential part of a pepper-pot emittance system requiring a quantitative profile evaluation. Therefore, we investigated the optical properties of 14 scintillating materials with different beams in the energy range 5.5 to 11.4 MeV/u as delivered by the heavy ion linac at GSI. Beside sensitive scintillators like YAG we focus on ceramic materials with lower light yield, like BN, ZrO2, Al2O3 and Al2O3+Cr. Their properties (light yield, beam width, high statistical moments etc.) are compared to different quartz glasses. The image of each macro-pulse is recorded by a digital CCD camera and individually evaluated by a high performance data acquisition system. For some materials, a decay of the light yield and an increase of the imaged beam width were observed. Moreover, the light yield depends on the screen temperature, which is significantly increased by the beam impact. A quantitative comparison under different beam conditions is presented.
ORNL, Oak Ridge, Tennessee
Taking Advantage of recent successes with the Laser Profile monitor, a new protottype is being built to use the laser wire as both a profile monitor and a slit for an emittance measuring device. This improved system takes advantage of the steering dipole magnet prior to ring injection of SNS such that only the recently stripped H0 protons continue forward to the emmitance device. In this way we hope to make an emittance device that is both parasitic to neutron production, and capable of accurate measurements during full power applications.
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
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.
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.
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.
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.