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.
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.
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.
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.
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.
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.
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.
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.
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.