SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) X-ray FEL utilizing the last km of the SLAC linac has been operational since April 2009 and finished its first successful user run last December. The various diagnostics for electron beam properties including beam position monitors, wire scanners, beam profile monitors, and bunch length diagnostics are presented as well as diagnostics for the X-ray beam. The low emittance and ultra-short electron beam required for X-ray FEL operation has implications on the transverse and longitudinal diagnostics. The coherence effects of the beam profile monitors and the challenges of measuring fs-long bunches are discussed.
LBNL, Berkeley, California
SLAC, Menlo Park, California
The scientific potential of femtosecond x-ray pulses at linac-driven FELs such as the LCLS is tremendous. Time-resolved pump-probe experiments require a measure of the relative arrival time of each x-ray pulse with respect to the experimental pump laser. In order to achieve this, precise synchronization is required between the arrival time diagnostic and the laser, which are often separated by hundreds of meters. We describe an optical timing system based on stabilized fiber links which has been developed for the LCLS to provide this synchronization. Preliminary results show synchronization of the synchronization signals at the sub-10 fsec level and overall synchronization of the x-ray and pump laser of <40 fsec. We present details of the implementation and LCLS and potential for future development.
Diamond, Oxfordshire
JAI, Egham, Surrey
UCL, London
Royal Holloway, University of London, Surrey
This paper describes the design of a cavity BPM for use in single pass machines. The design was modelled using a number of different EM codes to allow cross comparison of the simulation results. Furthermore, in addition to existing designs, the geometry has been modified to introduce a frequency separation between the horizontal and vertical dipole signals, as well as a reduction of the sensitivity of the position monitor to the monopole sum signal. The next stage of this project will be the manufacture of a prototype for tests in the transfer path at Diamond Light Source.
SLAC, Menlo Park, California
ANL, Argonne
CERN, Geneva
The Linac Coherent Light Source (LCLS) is a free-electron laser (FEL) at SLAC producing coherent 1.5 angstrom x-rays. This requires precise and stable alignment of the electron and photon beams in the undulator. We describe construction and operational experience of the beam position monitor (BPM) system which allows the required alignment to be established and maintained. Each X-band cavity BPM employs a TM010 monopole reference cavity and a single TM110 dipole cavity detecting both horizontal and vertical beam position. The processing electronics feature low-noise single-stage three-channel heterodyne receivers with selectable gain and a phase-locked local oscillator. Sub-micron position resolution is required for a single-bunch beam of 200 pC. We discuss the specifications, commissioning and performance of 36 installed BPMs. Single shot resolutions have been measured to be about 200 nm rms at a beam charge of 200 pC.
Fermilab, Batavia
CERN, Geneva
In the context of the development of a high resolution BPM system for the CLIC Main Linac we present the design of a cavity BPM prototype. It consists of a waveguide loaded dipole mode resonator and a monopole mode reference cavity, both operating at 15 GHz, to be compatible with the bunch frequencies at the CLIC Test Facility. Requirements, design concept, numerical analysis, and practical considerations are discussed.
CEA, Gif-sur-Yvette
IPN, Orsay
The European XFEL is a research facility, currently under construction in Germany. It is based on a superconducting electron linac including about 100 cryomodules based on the TESLA technology. Each cryomodule is equipped with a beam position monitor connected to a quadrupole at the high-energy end of the cavity string. Around one third of cold BPMs will be re-entrant RF cavities. This contribution will describe the present status of the cold re-entrant cavity BPM, and will present measurements of the BPM pickup and electronics prototypes.
RIKEN/SPring-8, Hyogo
Hamamatsu Photonics K.K., Hamamatsu-city
JASRI/SPring-8, Hyogo-ken
The SCSS test accelerator, which was constructed to check feasibility of XFEL/SPring-8, is operated for user experiments using stable EUV SASE. This accelerator provides a high quality electron beam with parameters suitable for power saturation of the EUV SASE, such as a bunch length of 300 fs and a peak current of 700 A. Evaluating the parameters is very important to ensure the stable generation of the SASE. The bunch length measurement systems to evaluate the parameters have been developed. The systems use the rf zero phasing method, the EO sampling method with temporal decoding and an 800 nm laser, and the method of observing OTR (near infrared region) by a FESCA-200 streak camera, which are mature technologies. All the measured bunch lengths were about 300 fs (FWHM), which is consistent with the individual methods. The most important result is that the streak camera with optimum tuning directly measured the temporal structure with femtosecond resolution. This presentation briefly introduces a development plan for a higher-resolution streak camera and a beam monitor system for the XFEL, as well as the experimental set-up and results.
BNL, Upton, Long Island, New York
A new microwave link has been developed for the longitudinal stochastic cooling system, replacing the fiber optic link used for the transmission of the beam signal from the pickup to the kicker. This new link reduces the pickup to kicker delay from 2/3 of a turn to 1/6 of a turn, which greatly improves the phase margin of the system and allows operation at higher frequencies. The microwave link also introduces phase modulation on the transmitted signal due to variations in the local oscillators and time of flight. A phase locked loop tracks a pilot tone generated at a frequency outside the bandwidth of the cooling system. Information from the PLL is used to calculate real-time corrections to the cooling system at a 10 kHz rate. The design of the pilot tone system is discussed and results from commissioning are described.
Fermilab, Batavia
A linear accelerator test facility called HINS has been operating at Fermilab. The goal of this program is to test new technology for the front end of an intensity frontier linac. Some of the new technologies that will be tested include: operation of multiple cavities from a single RF source using high-power vector modulators, round beam transport using superconducting solenoidal focusing, accelerating beam with spoke cavities, and a transition to superconducting RF cavities at 10 MeV. The testing has been split into four different stages: 2.5 MeV beam out of the RFQ only, acceleration through 6 room temperature cavities with quadrupole focusing, acceleration through 18 room temperature cavities with solenoidal focusing, and acceleration through the room temperature section plus one cryomodule of superconducting spoke cavities. Each stage focuses on testing the beam quality with a particular new technology. This paper describes the instrumentation necessary to verify the specified beam quality for each stage of the program.
DESY, Hamburg
TEMF, TU Darmstadt, Darmstadt
DESY Zeuthen, Zeuthen
INRNE, Sofia
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
INFN/LASA, Segrate (MI)
RAS/INR, Moscow
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
FNRF, Chiang Mai
MBI, Berlin
The Photo Injector Test facility at DESY Zeuthen site (PITZ) is dedicated to developing and optimizing high brightness electron sources for short wavelength Free-Electron Lasers (FELs) like FLASH and the European XFEL, both in Hamburg (Germany). Since October 2009 a major upgrade has been ongoing with the goal of improving the accelerating components, the photocathode drive laser system, and the beam diagnostics. The previously operated and fully characterized gun was brought to FLASH and will go into operation soon. A gun of the same type is installed now in PITZ. The conditioning has started and the gun will be characterized throughout 2010. A new booster cavity, Cut Disk Structure (CDS), was developed and will be mounted at PITZ in spring 2010. The booster cavity will be able to accelerate electrons above 20 MeV/c and will be suitable for long RF pulses. The most important upgrade of the diagnostics system will be the implementation of a phase space tomography module (PST) consisting of three FODO cells each surrounded by two screen stations. The results of commissioning, gun and booster conditioning and the very first measurements will be reported.
DESY, Hamburg
DESY Zeuthen, Zeuthen
The stability of the photo injector is a key issue for the successful operation of linac based free electron lasers. Several types of jitter can impact the stability of a laser driven RF gun. Fluctuations of the RF launch phase and the cathode laser energy have significant influence on the performance of a high brightness electron source. Bunch charge measurements are used to monitor the stability of the rf gun phase and the cathode laser energy. A basic measurement is the so called phase scan: the accelerated charge downstream of the gun is measured as a function of the launch phase, the relative phase of the laser pulses with respect to the RF. We describe a method which provides simultaneous information on rms jitters from phase scans at different cathode laser energies. Fluctuations of the rf gun phase together with cathode laser energy jitter have been measured at the Photo Injector test facility at DESY in Zeuthen (PITZ). Obtained results will be presented in comparison with direct independent measurements of corresponding instability factors. Dedicated beam dynamics simulations have been done in order to optimize the method performance.
DESY, Hamburg
The European XFEL is a 4th generation synchrotron radiation source, currently under construction in Hamburg. Based on different Free-Electron-Laser and spontaneous sources, driven by a 17.5 GeV superconducting accelerator, it will be able to provide several user stations with photons simultaneously. Due to the superconducting technology high average as well as peak brilliance can be produced. Flexible bunch pattern will allow for optimum tuning to the experiments demands. This paper will present the current planning of the electron beam diagnostics. An overview of the entire system will be given, as well as detailed insight into the main diagnostic systems, like BPM, charge and transmission diagnostics, beam size and beam loss monitor systems.
PSI, Villigen
The 9th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2009) was hosted by Paul Scherrer Institute (PSI) and took place at the Hotel Mercure Conference Center in Basel, Switzerland, May 25-27, 2009. A record number of 210 registered participants contributed to an exciting scientific program with ten invited talks, fourteen contributed orals and 115 poster contributions. In this talk, I will provide an overview of the various fields of beam instrumentation discussed during the workshop. A number of highlights from the scientific program have been selected, illustrating some of the outstanding achievements in accelerator diagnostics, presented at DIPAC 2009.