CERN, Geneva
At present more than 15000 particle accelerators exist worldwide, being built and optimised to handle a large variety of particle beams for basic research and applications in industry and medicine. Diagnostic tools have been developed and optimised according to the special requirements of these machines and to meet the demands of their users. Storage rings for ultra cooled heavy ion beams, third generation synchrotrons for the production of high brilliant radiation, super conducting protons machines working at the energy frontier and finally linear electron accelerators for FEL applications or high energy physics are just the most prominent representatives of the large variety of accelerators and each of them needs highly sophisticated tools to measure and optimise the corresponding beam parameters. Accordingly the issue addressed here is not to cover in full detail the different diagnostic devices but rather to concentrate on the aspects and needs as seen by the accelerator physicists and machine designers.
CERN, Geneva
During the 2008 LHC injection synchronisation tests and the subsequent days with circulating beam, the majority of the LHC beam instrumentation systems were capable of measuring their first beam parameters. This included the two large, distributed, beam position and beam loss systems, as well as the scintillating and OTR screen systems, the fast and DC beam current transformer systems, the tune measurement system and the wire scanner system. The fast timing system was also extensively used to synchronise most of this instrumentation. This presentation will comment on the results to date, some of the issues observed and what remains to be done for the next LHC run.
CERN, Geneva
The CERN Proton Synchrotron has been fitted with a new trajectory measurement system (TMS). Analogue signals from the forty beam position monitors are digitized at 125MS/s, and then further treated entirely in the digital domain to derive the positions of all individual particle bunches on the fly. Large FPGAs handle all digital processing. The system fits in fourteen plug-in modules distributed over three half-width cPCI crates. Data are stored in circular buffers of large enough size to keep a few seconds-worth of position data. Multiple clients can then request selected portions of the data, possibly representing many thousands of consecutive turns, for display on operator consoles. The system uses digital phase-locked loops to derive its beam-locked timing reference. Programmable state machines, driven by accelerator timing pulses and information from the accelerator control system, direct the order of operations. The cPCI crates are connected to a standard Linux computer by means of a private Gigabit ethernet segment. Dedicated server software, running under Linux, knits the system into a coherent whole.
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.
ORNL, Oak Ridge, Tennessee
UMD, College Park, Maryland
The Spallation Neutron Source (SNS) continues a ramp up in proton beam power toward the design goal of 1.4 MW on target. At Megawatt levels, US and Japanese studies have shown that cavitation in the Mercury target could lead to dramatically shortened target lifetime. Therefore, it will be critical to measure and control the proton beam distribution on the target, in a region of extremely high radiation and limited accessibility. Several sources of photons have been considered for imaging the beam on or near the target. These include a freestanding temporary screen, a scintillating coating, Helium gas scintillation, optical transition radiation, and a beam-heated wire mesh. This paper will outline the selection process that led to the current emphasis on coating development. In this harsh environment, the optics design presented significant challenges. The optical system has been constructed and characterized in preparation for installation. Optical test results will be described along with predictions of overall system performance.
iThemba LABS, Somerset West
FZJ, Jülich
Non-destructive beam position monitors (BPMs) have been in use at iThemba LABS for several years in the neutron therapy and radioisotope production beamlines, as well as in the transfer lines between the K200 separated-sector cyclotron and the two K8 injector cyclotrons. The sensitivity of these BPMs is limited by noise and pickup from the RF systems to about 300 nA in the high energy beam lines. For proton therapy, using the scattering method, position measurement at beam currents as low as 20 nA have to be made. A new and more sensitive BPM as well as the electronic measuring equipment, using RF pickup cancellation and improved filtering, have been developed and installed in the proton therapy beamline. The BPM, the electronic equipment and the results of measurements at beam currents down to 10 nA for 200 MeV protons are described.
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.
Brunel University, Middlesex
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. A fist measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and RF acceleration. A second spectrometer identical to the first one and a particle identification system provide a measurement of the outgoing emittance. By April 2009 it is expected that the beam and first set of detectors will have been commissioned, and a first measurement of input beam emittance may be reported. Along with the plan of measurements of emittance and cooling that will follow in the second half of 2009 and in 2010.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
An electron Scanner has been commissioned to non-destructively measure the transverse profiles in the Spallation Neutron Source (SNS) Ring. The SNS Ring is designed to accumulate in the order of 1.6·1014 protons with a typical peak current of over 50 Amps. Because of this high intensity no other profile measuring devices such as wire scanners were installed. The electron scanner is based on measuring the deflection of 50-75kV electrons by the electric field of the proton beam. Two electron guns, one for each plane, with dipole correctors, quadrupoles and deflectors to shape the electron beam have been installed. This paper describes the system and the initial results.
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.
UniDo/IBS, Dortmund
iThemba LABS, Somerset West
FZJ, Jülich
DELTA, Dortmund
Scintillation is one of the outcomes of beam interaction with residual gas. This process is utilized for non-destructive beam profile monitoring. Test bench measurements at various gas compositions and pressures as well as ones with the circulating proton beam at COSY-Juelich were performed. This was done using a single large photocathode PMT to estimate the photon yield. A multichannel photomultiplier was used along with a lens system to monitor the ion beam profile. Experimental results are presented and the challenges of the approach are discussed.
FZJ, Jülich
UniDo/IBS, Dortmund
GSI, Darmstadt
ITEP, Moscow
The advanced ionization beam profile monitor is being developed at GSI for the future FAIR facility in collaboration with ITEP and FZ-Jülich. In January 2009 the IPM prototype was installed in COSY-Jülich. After successful hardware test the beam tests followed. The prototype was operated without magnetic field, thus only residual gas ions were detected. An arrangement consisting of an MCP stack, a phosphor screen, and a CCD camera was used to detect ions. We report the first profile measurements of the proton beam up to 2.8 GeV at COSY.
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
PSI, Villigen
For the neutron spallation source SINQ at PSI a novel visual monitor (VIMOS) has been devised to guarantee correct beam conditions, triggered at the occasion of irradiating the delicate liquid metal target during the MEGAPIE project. VIMOS is looking directly for the most relevant parameter: it checks whether any point on the target is hotter than allowed. For this purpose the incandescence of a glowing mesh right in front of the beam entrance window is observed by means of dedicated radiation hard optics and suitable cameras. Starting from the initial goal of reliably detecting beam anomalies in a timely manner the scope of the system has been extended to serve as a standard device for beam monitoring and fine tuning of the settings of the proton beam transport lines. Over the course of the five years of continuous reliable operation of this unique system valuable experience has accumulated, which is employed for steady improvements of the device with respect to endurance in the radiation environment, calibration, maintenance, and price. A summary of the operational experience of VIMOS will be reported as well as steps taken towards further upgrades.
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.
NERS-UM, Ann Arbor, Michigan
Michigan Ion Beam Laboratory (MIBL) is equipped with a 1.7 MV tandem particle accelerator and a 400 KV ion implanter. Ion beams can be produced from a variety of ion sources and delivered to different beamlines. Precise beam profiling and current measurements are critical aspects of everyday activity in the laboratory and influence the success of each experiment. The paper will present the beam simulation software employed and the benefits and the shortcomings of the devices used at MIBL to precisely know all the parameters of the ion beams
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.
CNAO Foundation, Milan
CERN, Geneva
The CNAO, the first Italian center for deep hadrontherapy, is presently in its final step of installation. Commissioning of the low energy injection lines has been successfully concluded in January 2009. The synchrotron injection chain consists of a 8 keV/u Low Energy Beam Transfer (LEBT) line, an RFQ to accelerate the beam up to 400 keV/u, a LINAC to reach the 7 Mev/u injection energy and a Medium Energy Beam Transfer line. At the end of the LEBT line, just upstream the RFQ, an electrostatic Chopper deviates the beam for about 100 micro-seconds every 2 seconds on the vacuum chamber, in order to shape the particles batch according to LINAC requirements and to minimize the beam lost at the RFQ entrance. The chamber section hit by the beam was electrically isolated from the adjacent vacuum chambers, allowing the reading of the LEBT beam current. The detector is based on the Faraday Cup working principle, but it results in a “not-interceptive” monitor that is able to measure, continuously, the source beam current ripples and stability without affecting the beam delivered to the synchrotron. The system is presently under commissioning with beam and preliminary results are presented.
KEK, Tsukuba
RCNP, Osaka
We have continuously developed the Optical Transition Radiation (OTR) monitor with optics system based on the Newtonian telescope to measure a profile for a high intensity proton beamline. Now we installed the OTR monitors of production version on the J-PARC hadron beamline, and successfully observed a first OTR light. This led to the establishment of high S/N profile measurement with minimum beam disturbance. At this commissioning stage, a beam intensity is as small as 1.2 KW, but expected to increase up to 750 kW, so that maintenance work becomes important. To improve ease of maintenance, we plan to replace the focusing lens system with reflective mirror system with higher resistance to radiation. A result of beam profile measurement, an estimation of dependence of an OTR background on a beam loss, and a future plan for an upgrade of our optics system will be presented.
CEA, Gif-sur-Yvette
Within the framework of IFMIF-EVEDA project, a high-intensity deuteron beam (125 mA - 9 MeV) prototype accelerator will be built and tested at Rokkasho (Japan) in order to validate the future IFMIF accelerator. One of the most challenging diagnostics is the Beam Transverse Profile Monitor (BTPM), which has to be a non-interceptive device. Two R&D programs have been initiated: one based on residual gas fluorescence developed by Ciemat Madrid (see J. Carmona et al. contribution) and another one based on residual gas ionization developed at CEA Saclay. The principle of the last one is to measure the current induced by the ionization electrons, which drift under an electric field influence, towards several strips to get a one-dimension projection of the transverse beam profile. Preliminary results of a first prototype tested on the IPHI Saclay accelerator will be shown, as well as a new prototype design. In the new design several improvements have been carried out which will be tested soon with continuous and pulsed beam at higher energy.
CERN, Geneva
Carbon fibres are commonly used as moving targets in Beam Wire Scanners. Because of their thermo mechanical properties they are very resistant to particle beams. Their strength deteriorates with time due to low-cycle thermal fatigue. In case of high intensity beams this process can accelerate and in extreme cases the fibre is damaged during a scan. In this work a model describing the fibre temperature, thermionic emission and sublimation is discussed. Results are compared with fibre damage test performed on the CERN SPS beam in November 2008. For the operation of Wire Scanners with high intensity beams damage threshold are predicted.
CERN, Geneva
Linac4 is the first step of the future LHC injectors chain. This LINAC will accelerate H- ions from 45 keV to 160 MeV. During the commissioning phase of LINAC4, emittance measurements will be required at 45 keV, 3 MeV and 12 MeV. For this purpose a slit&grid system is currently being developed. The material and geometry of the wires and of the slits need to be optimized in order to reduce the effects of the energy deposition and maximize the signals: carbon, titanium steel and tungsten have been considered and studied. This document describes the results of the studies carried out during the design of the emittance meter and the first results during the commissioning.