TENZOR, Dubna, Moscow region
JINR, Dubna, Moscow Region
A diagnostic instrument in which a combination of a plastic scintillator and a solid-state photomultiplier is used as a nuclear radiation detector, is described. The detector is designed to record x-ray, gamma-ray, and neutron radiation in high-intensity proton beams accelerators.
PSI, Villigen
ORNL, Oak Ridge, Tennessee
Operation and upgrade of very intense proton beam accelerators like the PSI facility and the SNS spallation source at ORNL is typically constrained by potentially large machine activation. Besides the standard beam diagnostics, beam tomography techniques provide a reconstruction of the beam transverse phase space distribution, giving insights to potential loss sources like irregular tails or halos. Unlike more conventional measurement approaches (pepper pot, slits) beam tomography is a non destructive method that can be performed at high energies and, virtually, at any beam location. Results from the application of the Maximum Entropy Tomography (MENT) algorithm to different beam sections at PSI and SNS will be shown. In these reconstructions the effect of nonlinear forces is made visible in a way not otherwise available through wire scanners alone. These measurements represent a first step towards the design of a beam tomography implementation that can be smoothly employed as a reliable diagnostic tool.
IHEP Beijing, Beijing
Institute of High Energy Physics, Beijing
A high intensity RFQ has been built with an energy of 3.5 MeV and an average current of 3 mA. Based on this RFQ, we plan on performing a number of experimental tests on beam loss control. A series of beam diagnostic devices such as BPM, BLM, WS have thus been developed. Our work can also be easily applied to the CSNS project.
GSI, Darmstadt
TEMF, TU Darmstadt, Darmstadt
To achieve a high current operation close to space charge limit, a precise tune measurement during a full accelerating cycle is required. A tune measurement system was recently commissioned at GSI SIS-18, which allows calculation of tune using digital position data. It consists of three distinct parts; an exciter which provides band limited white noise to excite coherent betatron oscillations in the beam. The fast ADCs digitize the BPM signals at 125MSa/s and the post processing electronics integrate the data bunch by bunch to acquire one position value per bunch. Subsequently base band tune is determined by frequency transformation of the position data. Using this system, the charge effects were studied by correlating the current levels to tune spread/shift in the GSI synchrotron SIS-18. The experiment was conducted at injection energy of 11.6 Mev/nucleon using U73+.
CERN, Geneva
Carbon fibers are commonly used as moving targets in the beam wire scanners. The heating of the fiber due to energy loss of the particles traveling through is simulated with Geant4. Heating induced by the beam electromagnetic field is estimated with ANSYS. The heat transfer and sublimation processes are modeled. Due to the model nonlinearity a numerical approach based on discretization of the wire movement is used to solve it for particular beams. Radiation damage to the fiber is estimated with SRIM. The model is tested with available SPS and LEP data and a dedicated damage test on SPS beam is performed followed by post-mortem analysis of the wire remnants. Prediction for the LHC beams is made.
PSI, Villigen
The longitudinal-horizontal 2-dimensional (2D) density distribution of a bunched 2.2 mA beam of ~72 MeV protons has been measured at the last turns of the Injector 2 cyclotron, in the middle of the transfer line to and at the first turns of the Ring cyclotron. Protons scattered by a thin carbon-fibre target are stopped in a scintillator-photomultiplier detector. The longitudinal bunch shape is given by the distribution of arrival times measured with respect to the 50 MHz reference signal from the acceleration cavities. More probes are foreseen at 72 and 590 MeV which will use additional fibres to also determine the longitudinal-vertical and two longitudinal-diagonal 2D density distributions. These measurements together with more detailed beam transport calculations will support the matching of beam core and halo and the quest for a reduction of beam losses. The achievable dynamic range in the given environment of the cyclotrons and the connecting beam line is discussed.
CERN, Geneva
The LHC beam loss monitoring system is a safety critical system and ~ 4000 monitors are installed around the ring in order to prevent the superconducting magnets from quenches and protect the machine components from damage. Two different types of beam loss monitors are used: an ionization chamber (IC) and a secondary emission monitor (SEM). The response functions and expected signals have been simulated using Geant4 as well as FLUKA and have been validated and verified with measurements. The Geant4 model of the beam loss monitors has been tested with protons, gammas, neutrons, muon and mixed field beams for steady state and instantaneous losses. Results from the simulations compared to measurement results will be presented. The expected signals for several events (e.g. direct beam impact on collimators, over-injection, high intensity injection) have been checked against real data being taken during the LHC runtime in 2009 and 2010. The very good performance of the system and the agreement with previous simulations will be shown and discussed.
J-PARC, KEK & JAEA, Ibaraki-ken
KEK, Ibaraki
MINOTOS, Kunitachi, Tokyo Metropolitan
Morimoto Engineering, Iruma, Saitama
Kyoto University, Radioisotope Research Center, Kyoto-shi
UBE, Ichihara, Chiba
NIRS, Chiba-shi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
We developed a secondary emission type beam profile monitor with multi ribbon target made of a carbon graphite foil. The carbon graphite foil is excellent in endurance against heat load, and its thickness as 1.6-3.0 micron and low z (=6) are advantage for reducing beam loss. Intense bunch up to 1013 particle per bunch has been measured. Furthermore, the ribbon emits larger amount of electrons than ordinal metal wires because of its larger surface. Therefore the monitor has higher sensitivity, and transverse beam tail has been observed clearly. The monitors were installed in injection transport and injection point of main ring in J-PARC, in order to measure beam profiles by single passing. Normal size target has 32ch ribbons with 2 or 3 mm in width and their length is 200 mm or more each. In this report, target fabrication, basic characteristics of the carbon graphite target, and results of beam measurement will be discussed.
MPQ, Garching, Munich
CERN, Geneva
The Linac4 at CERN will provide 160-MeV negative hydrogen beams of high intensity N =2x1014 ions/s. Before this beam can be injected into the CERN PS Booster or future Superconducting Proton Linac for further acceleration, some sequences of 500-ps-long micro-bunches must be removed from it, using a beam chopper. We developed a monitor to measure the time structure and spatial profile of this chopped beam, with resolutions 1 ns and 2mm. Its large active area 40mm x 40mm and dynamic range also allows investigations of beam halos. The ion beam first struck a carbon foil, and secondary electrons emerging from the foil were accelerated by a series of parallel grid electrodes. These electrons struck a phosphor screen, and the resulting image of the scintillation light was guided to a thermoelectrically cooled, charge-coupled device camera. The time resolution was attained by applying high-voltage pulses of sub-nanosecond rise and fall times to the grids. The monitor has been tested with 700-ps-long UV laser pulses, and a 3-MeV proton beam. Its response over a wide range of beam intensities between 5 and 4x108 electrons emitted from the foil per pulse was studied.
ORNL, Oak Ridge, Tennessee
Two electron scanners, one for each plane, have been installed in the SNS Ring to measure the profile of the high intensity proton beam. The SNS Ring accumulates 0.6 us long proton bunches of up to 1.6·1014 protons with a typical peak current of over 50 Amp during a 1 ms cycle. The measurement is non-destructive and can be done during production. Electron guns with dipoles, deflectors and quadropules scan pulsed electrons through the proton beam. The EM field of the protons change the electrons' trajectory and projection on a fluorescent screen. Cameras acquire the projected curve and analysis software determines the actual profile of the bunch. Each scan lasts only 20 nsecs, which is much shorter than the proton bunch. Therefore the longitudinal profile of the proton bunch can be reconstructed from a series of scans made with varying delays. This talk will describe the theory, hardware and software of the electron scanner as well as the results and progress made in improving the measurements.
PSI, Villigen
The challenges for beam current and transmission measurements at high intensity (2.2mA, 1.3MW) beam operation are presented. The monitors used for the current measurements are resonators tuned at the 2nd RF harmonic (101 MHz). While most all the monitors do not require specific attention, the monitor placed 8m behind a graphite target presents several challenges. This current monitor is placed in vacuum and the calculated heat load due to the heavy shower of energetic particles is about 230 Watts for 2 mA beam current. The resonator cooling has been improved (active cooling, improved radiation cooling and a modified mechanical structure) to minimize drifts due to the thermal expension. However, the gain drift during operation is of the order of 10%. These larger than expected drifts are actually induced by the non-homogeneity of the power deposition. To correct these dynamical drifts, some on-line corrective electronics using 2 tests signals 50 kHz off the RF frequency had to be developed. This provides an innovative mean to estimate on-line the resonator gain. Without these corrections this system would have been unusable for transmission measurements at high beam intensity.
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
Due to rapid progress with the LHC commissioning in 2010 set-up beam intensities were soon surpassed and damage potential reached. One of the key systems for machine protection is the beam loss monitoring (BLM) system. Around 4000 monitors are installed at likely or critical loss locations. Each monitor has 384 associated beam abort thresholds (12 integrated loss durations from 40 us to 83 s for 32 energy intervals). A single integrated loss over threshold on a single monitor aborts the beam. Simulations of deposited energy, critical energy deposition for damage or quench and BLM signal response backed-up by control measurements determined the initial threshold settings. The commissioning and optimization of the BLM system is presented. Test procedures were used to verify the machine protection functionalities and optimize the system parameters. Dedicated beam tests and accidental magnet quenches were used to fine-tune threshold settings. The most significant changes to the BLM system during the 2010 run concerned the injection, the collimation and the beam dump region, where hardware changes and threshold increases became necessary to accommodate for increasing beam intensity.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Royal Holloway, University of London, Surrey
STFC/RAL, Chilton, Didcot, Oxon
Imperial College of Science and Technology, Department of Physics, London
The Rutherford Appleton Laboratory (RAL) is developing a Linac front end suitable for High Power Proton Applications (HPPA). The main components are an H- ion source with up to 60mA current at 65keV, a transport section to match the beam to an RFQ with 3MeV output energy and a MEBT comprising a chopper system with severalbuncher cavities. Photo detachment can be used as a non-destructive diagnostics method. The paper reports on progress with a beam profile monitor that is placed in a pumping vessel right after the ion source at the intersection to the Low Energy Beam Transport (LEBT). This consists of mirrors inside the vacuum to scan the laser beam through the beam, the actual detector to measure photo detached electrons, laser and optics outside the vacuum and electronics to amplify and read out the signal. The paper summarises the experimental set-up and status, discusses problems and presents recent measurements.
GSI, Darmstadt
As conventional intercepting diagnostics will not withstand high intensity ion beams, the non-destructive Beam Induced Fluorescence (BIF) method for transverse profile monitoring was extensively developed during the last years at the GSI heavy ion facility. An overview of the general performance, technical realization, applications and limitations will be given. Detailed investigations required for the optimization of this method were performed. Fluorescence spectra for various working gases like nitrogen and rare gases were recorded using an imaging spectrograph and wavelength selected beam profiles were obtained. The recorded profile width coincides for all working gases with the exception of He showing a significantly broader beam image. Experiments concerning the background contribution by beam induced neutrons and gammas were performed and the consequences for a possible installation close to a target will be discussed.
CIEMAT, Madrid
CNA, Sevilla
In the frame of the IFMIF-EVEDA accelerator project (a 125 mA, 9 MeV, 175 MHz (CW) Deuteron accelerator) two different optical non-interceptive monitors based on gas fluorescence has been designed and tested. One prototype of profiler is based on a PMT linear array whereas the other is based on a custom intensified CID camera. Both monitors have been tested at CNA cyclotron using 9 MeV deuterons up to 40 uA and 18 MeV protons up to 10 uA. Preliminary results of vertical beam profiles for deuterons and protons measured under different beam conditions are presented. The performance of both monitors under significant gamma and neutron background will be discussed. This optical beam diagnostic technique offers a non-invasive beam profile characterization for medium to high current hadron beams.
J-PARC, KEK & JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The overview and the present status of residual gas ionization profile monitors (IPMs) for J-PARC will be presented. Measured turn by turn profiles demonstrate clear contributions from dipole and quadupole injection mismatches. Injection tunings by using the IPMs are essential for painting injection tunings of 3 GeV Rapid Cycling Synchrotron (RCS) as well as to measure the emittance. As for the IPMs for RCS (RCS-IPMs), a magnetic guiding field (Bg) which is parallel to an external electric field (Eext) is also used, on the other hands, only the Eext is used for IPM for Main Ring synchrotron (MR-IPM); the Eext applied perpendicularly to the beam axis projects the ionized charged particles on the detector plane. Collecting the ionized ions with no Bg, the beam position at the RCS-IPMs calculated by using the BPMs (PosBPM) and the profile center (PosIPM) by the RCS-IPM suggests that PosIPM=PosBPM/2, and thus the measured beam size is shrink to a half size. Numerical analyses reveal that the fringe field of the electrodes to produce the Eext is the main source. The issue on the profile distortion due to the fringe fields will be discussed together with recovery plans.
Fermilab, Batavia
A number of high-intensity, multi-GeV superconducting proton or H- linacs are being developed or proposed throughout the world. The intensity frontier, having been identified as one leg of the future of particle physics, can be addressed by the development of such a linac. These accelerators will place strict demands on the required beam diagnostics, especially in the development of non-interacting monitors such as profile and halo monitors. Fermilab has started the High Intensity Neutrino Source (HINS) project as a research linac to address accelerator physics and technology questions for high-intensity, long pulse H- superconducting linacs. The paper will discuss the beam diagnostic needs for these high-intensity linacs as well as the role of HINS as a test facility for the development of beam diagnostic instrumentation required for the intensity frontier.
ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source is steadily approaching its design beam power of 1.4MW without encountering major beam dynamics issues or unexpectedly high beam losses. This success is a confirmation of a general validity of the models used for the accelerator design and tuning. Nevertheless, it is surprisingly difficult to reconcile many of the measured beam parameters with the model prediction. In this paper we discuss several examples of such discrepancies, ranging from a simple single particle tracking to the beam emittance measurements. We also present our approach on resolving some of the issues from the diagnostics side.