GSI, Darmstadt
TEMF, TU Darmstadt, Darmstadt
This contribution focuses on extensive simulations based on Finite Element Methods (FEM) which were successfully used for the design of several Beam Position Monitor (BPM) types. These simulations allow not only to reduce the time required for BPM prototyping but open up new possibilities for the determination of characteristic BPM features like signal strength, position sensitivity etc. Since a precise visualization of the signal propagation along the BPM structure is possible, effects like resonances, field inhomogeneties or complex cross talks between adjacent electrodes can be controlled. Moreover, modern simulation programs enable to define a charge distribution that is moving also at non relativistic velocities, which has an impact on the electromagnetic field propagation. It is shown that for slow ion beams the frequency spectrum of the BPM signal depends on the beam position. A variety of simulation methods are discussed in the context of different BPM realizations applied in hadron accelerators.
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.
CIEMAT, Madrid
CEA, Gif-sur-Yvette
The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology that will be used in the future IFMIF accelerator. Non-interceptive Beam Position Monitors pickups (BPMs) will be installed to measure the transverse beam position in the vacuum chamber in order to correct the dipolar and tilt errors. Depending on the location, the response of the BPMs must be optimized for a beam with an energy range from 5 up to 9 MeV and a current between 0.1 and 125 mA. Apart from the broadening of the electromagnetic field due to the low-beta beam, specific issues are affecting some of the BPMs: tiny space in the transport line between the RFQ and cryomodule (MEBT), cryogenic temperature inside the cryomodule, phase and energy measurement in the diagnostics plate, and debunching and big vacuum pipe aperture at the end of the high energy beam transport line. For this reason different types of BPMs are being designed for each location (MEBT, cryomodule, Diagnostics Plate and High Energy Beam Tranport Line). In this contribution, the design of each BPM will be presented, focusing on the electromagnetic response for high-current low-beta beams.
CERN, Geneva
A convenient way of having beam bunch intensity information available all around the LHC ring is to use the beam position monitor (BPM) system. The principle is to add the BPM signals, process them and make the result compatible with the time-modulation method used for transmitting the position over a fibre-optic link. In this way the same acquisition system can make both position and intensity data available. This paper describes the technique developed and presents the first intensity measurements performed on the CERN-SPS and LHC.
U. Erlangen-Nurnberg LHFT, Erlangen
Siemens Med, Erlangen
For beam position monitoring purposes, particle-in-cell simulations were applied to investigate pickup button and electron beam spectrum characteristics. Results on this simulative approach are presented. Particularly, a comparison is made between simulation results from the PIC solver of CST’s PARTICLE STUDIO and experimental data gathered with a 6 MeV electron beam from a linear accelerator for medical purposes. The measurements were conducted under non-vacuum conditions. Good agreement between simulation and experimental data was achieved although non-negligible electron spread during air passage of the electron beam can be assumed.
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).
CERN, Geneva
EPFL, Lausanne
LAL, Orsay
Within the framework of the second Joint Research Activity PHIN of the European CARE program, a new photo injector for CTF3 drive beam has been designed and installed by collaboration between LAL, CCLRC and CERN. The laser driven rf photo injectors are recent candidates for high-brightness, low-emittance electron sources. One of the main beam dynamics issues for a high brightness electron source is the optimization of beam envelope behavior in the presence of the space charge force in order to get low emittance. Beam based measurements have been made during the commissioning runs of the PHIN 2008 and 2009 including measurements of the emittance, using multi-slits technique. In this work the photo injector will be described and the first beam measurement results will be presented and compared with the PARMELA simulations.
INFN/LNF, Frascati (Roma)
INFN-Roma II, Roma
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
One of the key diagnostics techniques for the full characterization of beam parameters for LINAC-based FELs foresees the use of RF deflectors. With these devices it is possible to completely characterize both the longitudinal and the transverse phase space. In the talk I will present the main design considerations for time resolved (sliced) beam parameter measurements using RF deflectors. Measurement setups for longitudinal pulse shape as well as phase space and transverse beam slice emittance characterizations are described. The main sources of errors are discussed and the design criteria of these devices are presented. In particular the SPARC RF deflector and the related diagnostic lines as well as recent measurement results from the SPARC facility are shown. RF deflectors in use or planned to be used in other FEL labs are then illustrated with an overview of these activities.
MPI-K, Heidelberg
The University of Liverpool, Liverpool
Growing interest in the development of low energy projectile beams, in particular heavy ions and antiprotons, calls for new beam instrumentation to be developed to match the strict requirements on ultra-high vacuum and low beam perturbation. When it comes to transverse profile monitoring, a convenient solution for simultaneous determination of both transverse profiles is found in a neutral supersonic gas-jet target shaped into a thin curtain and the two-dimensional imaging of the gas ions created by impacting projectiles. The resolution and vacuum efficiency of this monitor is directly linked to the characteristics of the gas-jet curtain. In this contribution we describe the design of a nozzle-skimmer system to be used for the creation of the jet curtain in the first prototype of such a monitor. Using numerical fluid dynamics simulations, we present the effects resulting directly from changes in the geometry of the nozzle-skimmer system on the characteristics of the jet curtain.
CERN, Geneva
UFC, Besançon
UTBM, Belfort
Scanning of a high intensity particle beam imposes challenging requirements on Wire Scanner system. It is expected to reach scanning speed of 20 m/s with position accuracy of the order of 1 μm. In addition a timing accuracy better than 1 millisecond is needed. The adopted solution consists of a wire holding fork rotating by maximal of 200°. Fork, rotor and angular position sensor are mounted on the same axis and located in a chamber connected to the beam vacuum. The requirements imply the design of a system with extremely low vibration, vacuum compatibility, radiation, and temperature tolerance. The adopted solution consists of a rotary brushless synchronous motor with the permanent magnet rotor installed inside of the vacuum chamber and the stator installed outside. The accurate position sensor will be mounted on the rotary shaft inside of vacuum chamber and has to resist bake-out temperature of 200°C and ionizing radiation up to tenth of kGy/years. A digital feedback controller allows maximum flexibility for the loop parameters and feeds the 3 phases input for the linear power driver. The paper will present a detail discussion of chosen concept and the selected components.
CEA, Gif-sur-Yvette
Optical diagnostics based on the excitation of residual gas molecules are routinely used for high intensity beam characterization. Beam intensity, beam position and profile are measured by means of a CCD sensor. In addition species fraction and profile of each beam are measured using a Doppler shift method. As part of IFMIF-EVEDA* project, CEA is in charge of the design and realization of the 140mA-100keV cw deuteron source and low energy beam transport line. In the beam line, (D,d) reaction will occur and high neutron flux will be emitted when deuteron beam interacts with surfaces. Moreover gamma ray and activation will also occur. In order to protect diagnostics, coherent optic fibers could be used to transport the beam image outside the irradiated zone. A comparative study of two coherent fibers will be presented (FUJIKURA & SCHOTT), along with the characterization in magnification and attenuation of a 610 mm long fiber and its associated optics. To estimate the capability of such fibers to transport beam image, a dedicated experiment has been performed with proton beam produced by the SILHI source. The beam transverse profile has been compared with and without the optic fiber.
* International Fusion Materials Irradiation Facility - Engineering Validation and Engineering Design Activities
Soreq NRC, Yavne
ACCEL, Bergisch Gladbach
RI Research Instruments GmbH, Bergisch Gladbach
The first phase of the SARAF high current proton/deuteron accelerator facility is currently under commissioning. Along with traditional beam diagnostics instruments, a beam halo measuring station was implemented into the SARAF diagnostic plate. The beam halo is planned to be characterized using a mini Faraday cap, on-line and off-line measurements of radiation from LiF target crystals and by monitoring energy spectra of Rutherford scattered particles from a thin gold foil. The first experience with 3 mA, pulsed proton beam included measuring energy spectra of the protons at energies up to 2.2 MeV scattered at 45 degrees from a 0.3 mg/cm2 thick gold foil. The beam was accelerated by SARAF RFQ and by several cryogenic resonators in the SARAF Prototype Superconductive Module. The energy spectra of the scattered particles were taken for different RFQ voltages and for different voltages and phases of the PSM resonators. The results were compared with time of flight measurements utilizing two phase probes installed at the D-plate. Comparison of the experimental spectra with results of the TRACK Monte-Carlo simulations was also performed.
Fermilab, Batavia, Illinois
LBNL, Berkeley, California
Electron cloud density in the Fermilab Main Injector was measured by observing microwave transmission along the vacuum tube. Presence of the electron cloud reduces the velocity of the microwave signal. Both frequency and time domain methods reveal relative cloud density and time evolution. The effect of beam time structure is clearly evident. The accelerator magnetic field effects the distribution of electrons making it difficult to estimate density.
CERN, Geneva
A novel radiation hardened current digitizer ASIC is in planning stage, aimed at the acquisition of the current signal from the ionization chambers employed in the Beam Loss Monitoring system in CERN accelerator chain. The purpose is to match and exceed the performances of the existing discrete component design, currently in operation in the Large Hadron Collider (LHC). The specifications include: a dynamic range of nine decades, defaulting to the 1pA-1mA range but adjustable by the user, ability to withstand a total integrated dose of at least 10 kGray in 20 years of operation and user selectable integrating windows, as low as 500ns. Moreover, the integrated circuit can be employed to digitize currents of both polarity with a minimum number of external components and without needing any configuration. The target technology is IBM 130 nm CMOS process. The specifications, the architecture choices and the reasons on which they're based upon are discussed in the paper.
FZD, Dresden
At the ELBE Free Electron Laser (FEL) at Forschungszentrum Dresden Rossendorf (FZD) electron bunches having lengths between 1 to 4 ps are generated. It is required to compress these electron bunches to lengths below 1 ps which necessitates diagnosis of the electron bunch parameters. We use a Martin-Puplett interferometer (MPI) which is a modification of the Michelson interferometer, where the beams are linearly polarized at specific orientations. It measures the autocorrelation function of the coherent transition radiation (CTR) from a view screen which is an optical replication of the electron bunch. The interferometer setup consists of various optical components like polarizers, beam splitter, mirrors and Golay cell detectors. In our measurement a wire grid was used as a polarizer and also as a beam splitter. A thorough understanding of the response of the optical components, as a function of the CTR wavelength range of our interest, is required for correct analysis of the measured signal. We have therefore simulated the response of the entire interferometer setup including the diffraction losses and the window transmission and compared the results to experimental measurements.
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.
DESY, Hamburg
High-brightness electron bunches with low energy spread, small emittance and high peak currents are the basis for the operation of high-gain Free Electron Lasers (FELs). As only part of the longitudinally compressed bunches contributes to the lasing process, time-resolved measurements of the bunch parameters are essential for the optimisation and operation of the FEL. Transverse deflecting structures (TDS) have been proven to be powerful tools for time-resolved measurements. Operated in combination with a magnetic energy spectrometer, the measurement of the longitudinal phase space can be accomplished. Especially in case of ultra-short electron bunches with high peak currents for which a time resolution on the order of 10 fs would be desirable, both the TDS and magnetic energy spectrometer have intrinsic limitations on the attainable resolution. In this paper, we discuss the fundamental limitations on both the time and energy resolution, and how these quantities are connected.
GANIL, Caen
The SPIRAL2 project is composed of an accelerator and a radioactive beam section. Radioactive ions beams (RIBs) will be accelerated by the current cyclotron CIME and sent to GANIL experimental areas. The accelerator, with a RFQ and a superconducting Linac, will accelerate 5 mA deuterons up to 40MeV and 1 mA heavy ions up to 14.5 MeV/u. A new electronic device has been evaluated at GANIL to measure phase and amplitude of pick-up signals. The principle consists of directly digitizing pulses by under-sampling. Phase and amplitude of different harmonics are then calculated with a FPGA by an I/Q method. Tests and first results of a prototype are shown and presented as well as future evolutions.
GSI, Darmstadt
ITEP, Moscow
A device for accessing the longitudinal phase space at low energy sections (1.4 MeV/u) of the GSI heavy ion LINAC is presented. In the course of the FAIR project optimizations of the existing facility at GSI are required. Integral information for the optimization process is extracted by the knowledge of the six dimensional phase space. Opposed to the transversal parameters it is particular difficult to access the longitudinal degree of freedom at low energies. The presented interceptive measurement is based on the coincident detection of single particles by means of two detectors: The first detector provides measurement of secondary electrons emitted from a thin Al-foil by the impinging ion beam. Secondly, after a drift of 80 cm beam particles are registered directly by a fast diamond detector. This contribution describes the measurement setup in detail including the principle of particle number attenuation by Rutherford scattering in the Ta foil. The achievements concerning the required timing resolution are presented and the investigations are accompanied by recently recorded data.
PSI, Villigen
A new current monitor has been built and installed during the last maintenance period in prevision of the high intensity beam operation (3mA, 1.8MW) which is planned in the near future. It is a re-entrant cavity tuned at the 2nd RF harmonic (101 MHz). Compared to the current monitors already in operation, the design had to be modified to improve its cooling. Indeed, this monitor is placed 8 m behind a graphite target and is exposed to scattered particles. The resulting heat load would raise the monitor temperature well above 200 deg C without cooling. The modifications include a slightly different structure to improve the heat conduction, a blackening of the external surface to increase the thermal radiation and an active water cooling. Thermocouples placed on the cavity will monitor the temperature of the system. The new design was supported by simulations for heat load resulting from the scattered particles and by calculations concerning the cooling efficiency. Results obtained during laboratory tests and at the beginning of operation will be presented. Comparison between expected heat load and temperature with the actual measured values will be also discussed.
INFN-Roma, Roma
LAL, Orsay
INFN/LNF, Frascati (Roma)
roma3, Rome
INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza)
The Frascati e+e- collider DAΦNE, running at sqrt(s) 1.02 GeV is testing the crabbed waist scheme, aiming to reach a large improvement of the specific and integrated luminosity of the accelerator. In order to have a reliable, fast and accurate measurement of the absolute luminosity a number of dedicated detectors have been designed, built, tested, calibrated and put into operation. In particular, three different monitors have been realized: a Bhabha calorimeter, realized with lead/scintillator tiles read by WLS fibers subdivided in 10+10 phi sectors, a Bhabha GEM tracker, of annular shape, with a 4x16 pads per side, covering the same angular region between 18 and 27 degrees in theta, and a Bremsstrahlung proportional counters realized by a couple of 4 PbWO4 crystals at small angle. Results from the 2008 run of DAΦNE are presented, together with the analysis tools for background subtraction and comparison with GEANT simulations.
CERN, Geneva
KEK, Ibaraki
UW-Madison/PD, Madison, Wisconsin
For the LHC beam loss measurement system the high voltage supply of the ionisation chambers and the secondary emission detectors is used to test their connectivity. A harmonic modulation of 0.03 Hz results in a current signal of about 100 pA measured by the beam loss acquisition electronics. The signal is analyzed and the measured amplitude and phase are compared with individual channel limits for the 4000 channels. It is foreseen to execute an automatic procedure for all channels every 12 hours which takes about 20 minutes. The paper will present the design of the system, the circuit simulations, measurements of systematic dependencies of different channels and the reproducibility of the amplitude and phase measurements.
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
HIT, Heidelberg
The ion cancer therapy facility HIT in Heidelberg is producing ions (H, He, C and O) from two ECR sources at an energy of 8 keV/u with different beam currents from about 80 μA up to 1.2 mA. Typical sizes for the beam in the LEBT range from are 5 40 mm. Matching the always slightly changing output from the ECR sources to the first accelerating structure, an RFQ, demands a periodical monitoring of the beam emittance. For that, a special pepper-pot measurement device is under design, whose most important parts are a damage-resistant pepper-pot mask and a vacuum-suitable scintillator material. The investigation of the material lifetime is done in the first step by computing the maximum intensity the target volume can stand without any radiation damage, shock and heating. A list of feasible materials will be discussed and results from SRIM calculations for them will be shown. A set-up for necessary material tests with beam will be presented.
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
INFN-Roma II, Roma
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
The characterization of the transverse phase space of electron beams with charge density and high energy is a fundamental requirement for particle accelerator facilities. The knowledge of characteristics of the accelerated electron beam is of great importance for the successful developement of the SPARC FEL. Here the high-energy emittance measurement with the quadrupole scan technique using two quadrupoles arranged as a doublet is discussed.