DESY, Hamburg
CERN, Geneva
RIKEN/SPring-8, Hyogo
PSI, Villigen
XFELs require high precision orbit control in the long undulator sections. Due to the pulsed operation of these systems the high precision has to be reached by single bunch measurements. So far cavity BPMs achieve the required performance and will be used at the European XFEL between each of the 116 undulators. Coupling between the orthogonal planes limits the precision of beam position measurements. A first prototype build at DESY shows a coupling between orthogonal planes of about -20 dB, but the requirement is lower than -40 dB (1%). The next generation Cavity BPM was build with tighter tolerances and mechanical changes, the orthogonal coupling is measured to be lower than -43 dB. This report discusses the various observations, measurements and improvements which were done.
PSI, Villigen
ELETTRA, Basovizza
CERN, Geneva
Currently a X band traveling wave accelerator structure is fabricated in a collaboration between CERN and PSI. It will compensate nonlinearities in the longitudinal phase space at the injector prototype of the PSI-XFEL, whereas CERN will use it to test break down limits and rates in the high gradient regime. Due to the modest beam energies, the operation in the PSI-XFEL injector is quite sensitive to transverse wakes destroying the beam emittance. In that respect, the structure will use an active monitoring of the beam to structure alignment and include two wake field monitors coupling to the transverse higher order modes. These allow steering the beam to the structure axis giving a higher precision than mechanical alignment strategies. Localized offsets due to bends or tilts have individual signatures in the frequency spectrum, which in turn are correlated with different delays in the signal envelope. By taking advantage of this combined with the single bunch mode at the PSI-XFEL, the use of a relatively simple detector type RF front end should be possible, which will not only show beam offsets, but also higher order misalignments as tilts in the structure.
PSI, Villigen
The resonant stripline pickup was chosen for a Beam Position Monitor (BPM) developed for the 250 MeV PSI XFEL Injector to reach the desired sensitivity of 10 micrometers in beam position. The electromagnetic design of this cavity, performed with Microwave Studio, was optimized in terms of the main radiofrequency characteristics - frequency, shunt impedance, Q value - of the resonant modes of interest, in order to obtain the pickup sensitivity required by the electronics (direct sampling, [*]). Also mechanical aspects of the design are presented, with particular attention to the solution adopted for the stripline alignment. Based on the simulated geometry, a pickup prototype was carried out and tested, allowing to verify the correct characteristics of the resonant modes and to state the present resonant stripline pickup design as one possible candidate for the standard (non-undulator) BPM system of the PSI XFEL and also for other linear accelerators or storage ring transfer lines.
[*]: B. Keil, S. Lehner. S. Ritt, "Application of a 5 GSPS Analogue Ring Sampling Chip For Low-cost Single-shot BPM Systems", Proc. EPAC 2008, Genoa, Italy, 1167 (2008).
DESY Zeuthen, Zeuthen
LAL, Orsay
Research activities at the Photo Injector Test facility at DESY, Zeuthen site, (PITZ) aim to develop and optimize high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. To demonstrate the XFEL operation, an electron bunch train containing 3250 pulses of 1 nC charge at 10 Hz repetition rate is required. The spectrometers and related equipments for studying the longitudinal phase space for such long pulse trains do not yet exist at PITZ. Design and construction of a new high energy dispersive arm (HEDA2) is currently in progress. Besides the requirement to handle long electron bunch trains, the HEDA2 setup is designed to allow high resolution measurements of momentum distribution up to 40 MeV/c, a longitudinal phase space measurement with slice momentum spread down to 1 keV/c and transverse slice emittance measurements at off crest booster phases. The status of the physics design and technical considerations of this dispersive section will be presented in this contribution.
University of Oslo, Oslo
CERN, Geneva
Uppsala University, Uppsala
IN2P3-LAPP, Annecy-le-Vieux
The two-beam acceleration scheme foreseen for CLIC and the associated radio-frequency (RF) components will be tested in the Two-beam Test Stand (TBTS) at CTF3, CERN. Of special interest is the performance of the power extraction structures (PETS) and the acceleration structures as well as the stability of the beams in the respective structures. After the recent completion of the TBTS, the first 12 GHz PETS has been tested with beam. Up to 30MW of RF power was extracted from a 5A electron beam, using so called recirculation of the RF power inside the PETS. The TBTS instrumentation, including inductive beam position monitors, allows precise measurement of beam parameters before and after the PETS as well as RF power and phase. Measurements of transverse kicks, energy loss and RF power with recirculation are discussed and compared with estimations, including first measurements of RF pulse shortening probably due to break down.
CNAO Foundation, Milan
INFN/LNF, Frascati (Roma)
CERN, Geneva
The CNAO, the first Italian center for deep hadrontherapy, is presently in its final step of installation. It will deliver treatments with active scanning both with Proton and Carbon ion beams. Commissioning of the low energy injection lines has been successfully concluded in January 2009. CNAO beams are generated by two ECR sources which are both able to produce both particle species. The beam energy in the Low Energy Beam Transfer (LEBT) line is 8 keV/u. A compact and versatile tank containing a complete set of diagnostic tools has been intensively used for the line commissioning: in a length of 390mm it houses two wire scanners, for vertical and horizontal beam transverse profile, a Faraday Cup, for current measurement, and two vertical and horizontal plates for beam halo suppression , emittance measurements, beam collimation and particles selection. Using one tank devices, phase space distribution reconstruction can be quickly performed as well as synchronous profiles and intensity measurements. Commissioning results and measurements are presented.
SLAC, Menlo Park, California
CERN, Geneva
Synchrotron-light telescopes will monitor the profiles of the two LHC proton beams. At collision energy (7 TeV), each telescope will image visible light from a superconducting dipole used to increase beam separation for the RF-cavities. At injection (0.45 TeV), this source must be supplemented by a two-period superconducting undulator 80 cm from the dipole. We will present the mechanical and optical layouts of the telescope. The initial plan to use dipole edge radiation at high beam energy, for its increased visible emission, suffers from significant diffractive blurring. We will instead collect radiation from the first 2 to 3 m of the dipole’s interior. An optical "trombone" delay line will provide the large shift in focus. We will discuss calculations and measurements of blurring by diffraction and by this extended source, and present an alternative optical design using off-axis elliptical mirrors.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Imperial College of Science and Technology, Department of Physics, London
The RAL front end FETS is currently under construction to demonstrate an H-ion beam with up to 18 kW at 3 MeV. Due to the beam power photo detachment techniques are the preferable choice for emittance instruments. Typically, measurements will be performed in just one transverse plane by using a magnet to separate ion beam from produced neutrals. Another general technique to work out a 2D emittance bases on several beam profiles applying an image reconstruction method called maximum entropy (MaxEnt). Combining both methods in one device has the significant advantage of reducing technical and physical problems which may occur by doubling magnet or laser beam path. Drawback of MaxEnt is the necessity of sufficient phase space advance to achieve reasonable results which can be either optimised by moving the particle detector or with additional focusing. The paper presents a conceptual design study discussing all possible constraints given by beam parameters and chopper/ MEBT. Simulations will help to estimate performance and errors.
DESY, Hamburg
For current and future accelerators, in particular light sources, high availability is an important topic. Therefore the causes of beam losses must be diagnosed and eliminated as fast as possible. This paper presents a concept using the following signals and data from diagnostic instruments and other sources:
- software alarms transmitted by the control system,
- hardware alarms received and timestamped by the machine protection system, and
- Post-Mortem-Analysis.
CERN, Geneva
University of Oslo, Oslo
The CTF3 provides high current (28A) high frequency (12GHz) electron beams, which are used to generate high power radiofrequency pulses at 12GHz by decelerating the electrons in resonant structures. A Test Beam Line (TBL) is currently being built in order to prove the efficiency and the reliability of the RF power production with the lowest level of particle losses. As the beam propagates along the line, its energy spread grows up to 60%. For instrumentation, this unusual characteristic implies the developments of new and innovative techniques. One of the most important tasks is to measure the beam energy spread with a fast time resolution. The detector must be able to detect the energy transient due to beam loading in the decelerating structures (nanosecond) but should also be capable to measure bunch to bunch fluctuations (12GHz). This paper presents the design of the spectrometer line detectors.
PSI, Villigen
This contribution gives an overview of transverse sub-micron beam position measurement systems and techniques for 3rd and 4th generation light sources and collider projects. Topics discussed include mechanical, electrical and digital design aspects, environmental influences, machine operation and design considerations, as well as system- and beam-based measurement and calibration techniques.
DESY, Hamburg
Future accelerators like the International Linear Collider and Free-Electron Lasers require beam position measurements with resolutions between few nanometres and 1 μm. Cavity Beam Position Monitors (BPM) are able to achieve the resolution. This paper shows the basic principles of this type of monitor, followed by a brief history of the developments. Since different institutes are designing Cavity BPM system for different projects, an overview is given on their recent developments including results and limitations compared with their requirements.
SLAC, Menlo Park, California
ANL, Argonne, Illinois
We present the performance of the cavity beam position monitor (BPM) system for the Linac Coherent Light Source (LCLS) undulator at SLAC. The construction and installation phase of 36 BPMs have been completed. Commissioning is underway. The X-band cavity BPM employs a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at nominal center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and phase locking local oscillator. The approximately 40MHz intermediate frequency is digitized to 16 bits at a 119 MHz sampling rate then reduced to baseband digitally. Phase and charge are normalized with respect to the reference cavities. System requirements include sub-micron position resolution for a single-bunch beam charge of 200 pC. Early commissioning results indicate single-bunch resolutions better than 500 nm rms and stabilities better than 1 micron drift over 24 hours.
DESY Zeuthen, Zeuthen
DESY, Hamburg
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
Uni HH, Hamburg
The Photo Injector Test facility at DESY, Zeuthen site, (PITZ) develops and optimizes high brightness electron sources for Free Electron Lasers (FELs) like FLASH and the European XFEL. A new multi-purpose dispersive section was designed* and installed to characterize the momentum distribution, the longitudinal phase space distribution and the transverse slice emittance of the electron bunch for an electron energy up to 40 MeV. The spectrometer consists of a 180 degree dipole magnet followed by a slit, a quadrupole magnet and two screen stations. One of the screen stations is equipped with an optical read-out for a streak camera to measure the longitudinal phase space distribution. The first measurement results and corresponding beam dynamics simulations of the longitudinal phase space and the momentum distributions will be reported in this contribution. The resolution of the system will be analysed and compared to the design expectations.
*Sergiy Khodyachykh et al.
"Design and Construction of the Multipurpose Dispersive Section at PITZ"
Proceedings of DIPAC 2007, Venice, Mestre, Italy 2007
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
The RAL Front End Test Stand is under construction with the aim of demonstrating production of a high-quality, chopped 60 mA H- beam at 3 MeV and 50 pps. In addition to the accelerator development, novel laser-based diagnostics will be implemented. This paper reports on a device that will be able to measure multiple profiles of the beam density distribution in such a way that the full 2D density distribution can be reconstructed. The device is currently being commissioned. The status of the device is presented together with results of the commissioning and plans for future development.
Uni HH, Hamburg
DESY, Hamburg
A synchrotron radiation monitor (SRM) based on a multi-anode photomultiplier tube (PMT) has been installed in the first magnetic bunch compressor chicane at the Free-electron LASer in Hamburg (FLASH). The synchrotron radiation emitted in the third dipole of the magnetic chicane is imaged by a telescope onto two anodes of the PMT. In this way the horizontal beam position of the electron bunches is recorded which corresponds to the beam energy as the beam position is governed by the beam energy in the dispersive section of the magnetic chicane. The fast PMT signals are digitized by analog -to-digital converters (ADC) which enables bunch-resolved beam energy measurement within the trains of the up to 800 bunches generated by the superconducting linear accelerator of FLASH. In this paper we describe the experimental setup of the SRM and present first commissioning results for various accelerator settings.