Beam Loss Monitoring System Research Articles

A new beam loss detector for low-energy proton and heavy-ion accelerators

The Facility for Rare Isotope Beams (FRIB) to be constructed at Michigan State University shall deliver a continuous, 400kW heavy ion beam to the isotope production target. This beam is capable of inflicting serious damage on accelerator components, e.g. superconducting RF accelerating cavities. A Beam Loss Monitoring (BLM) System is essential for detecting beam loss with sufficient sensitivity and promptness to inform the machine protection system (MPS) and operations personnel of impending dangerous losses. Radiation transport simulations reveal shortcomings in the use of ionization chambers for the detection of beam losses in low-energy, heavy-ion accelerators. Radiation cross-talk effects due to the folded geometry of the FRIB LINAC pose further complications to locating specific points of beam loss. We propose a newly developed device, named the Loss Monitor Ring (LMR11Loss Monitor Ring.), to be implemented upstream of each FRIB cryomodule, as part of the direct loss monitoring system to fulfill the needs of machine protection.

BEPCⅡ储存环逐束团丢束监测系统及应用

BEPCⅡ储存环逐束团丢束监测系统及应用

Radiation damage in the diamond based beam condition monitors of the CMS experiment at the Large Hadron Collider (LHC) at CERN

The Beam Condition Monitor (BCM) of the CMS detector at the LHC is a protection device similar to the LHC Beam Loss Monitor system. While the electronics used is the same, poly-crystalline Chemical Vapor Deposition (pCVD) diamonds are used instead of ionization chambers as the BCM sensor material. The main purpose of the system is the protection of the silicon Pixel and Strip tracking detectors by inducing a beam dump, if the beam losses are too high in the CMS detector. By comparing the detector current with the instantaneous luminosity, the BCM detector efficiency can be monitored. The number of radiation-induced defects in the diamond, reduces the charge collection distance, and hence lowers the signal. The number of these induced defects can be simulated using the FLUKA Monte Carlo simulation. The cross-section for creating defects increases with decreasing energies of the impinging particles. This explains, why diamond sensors mounted close to heavy calorimeters experience more radiation damage, because of the high number of low energy neutrons in these regions. The signal decrease was stronger than expected from the number of simulated defects. Here polarization from trapped charge carriers in the defects is a likely candidate for explaining the difference, as suggested by Transient Current Technique (TCT) measurements. A single-crystalline (sCVD) diamond sensor shows a faster relative signal decrease than a pCVD sensor mounted at the same location. This is expected, since the relative increase in the number of defects is larger in sCVD than in pCVD sensors.

Beam Loss Monitoring for LHC Machine Protection

Abstract The energy stored in the nominal LHC beams is two times 362 MJ, 100 times the energy of the Tevatron. As little as 1 mJ/cm 3 deposited energy quenches a magnet at 7 TeV and 1 J/cm 3 causes magnet damage. The beam dumps are the only places to safely dispose of this beam. One of the key systems for machine protection is the beam loss monitoring (BLM) system. About 3600 ionization chambers are installed at likely or critical loss locations around the LHC ring. The losses are integrated in 12 time intervals ranging from 40 μs to 84 s and compared to threshold values defined in 32 energy ranges. A beam abort is requested when potentially dangerous losses are detected or when any of the numerous internal system validation tests fails. In addition, loss data are used for machine set-up and operational verifications. The collimation system for example uses the loss data for set-up and regular performance verification. Commissioning and operational experience of the BLM are presented: The machine protection functionality of the BLM system has been fully reliable; the LHC availability has not been compromised by false beam aborts.

Monitoring system experiments on beam loss at SSRF injector

Experiments on beam loss by using beam loss monitoring (BLM) system were carried out at Shanghai Synchrotron Radiation Facility (SSRF) injector. This system used highly sensitive and current-integrated Si-photodiode detectors and an Ethernet data acquisition (DAQ) system. The experimental results demonstrate that the Si-photodiode detectors are a useful tool that provides dynamic information on beam loss and investigates problems of machine operation. It also shows that the Si-photodiode BLM system is suitable for pulse-radiation of high-energy accelerators.

The upgraded data acquisition system for beam loss monitoring at the Fermilab Tevatron and Main Injector

A VME-based data acquisition system for beam-loss monitors has been developed and is in use in the Tevatron and Main Injector accelerators at the Fermilab complex. The need for enhanced beam-loss protection when the Tevatron is operating in collider-mode was the main driving force for the new design. Prior to the implementation of the present system, the beam-loss monitor system was disabled during collider operation and protection of the Tevatron magnets relied on the quench protection system. The new Beam-Loss Monitor system allows appropriate abort logic and thresholds to be set over the full set of collider operating conditions. The system also records a history of beam-loss data prior to a beam-abort event for post-abort analysis. Installation of the Main Injector system occurred in the fall of 2006 and the Tevatron system in the summer of 2007. Both systems were fully operation by the summer of 2008. In this paper we report on the overall system design, provide a description of its normal operation, and show a number of examples of its use in both the Main Injector and Tevatron.

First experiences with the LHC BLM sanity checks

The reliability concerns have driven the design of the Large Hardron Collider (LHC) Beam Loss Monitoring (BLM) system from the early stage of the studies up to the present commissioning and the latest development of diagnostic tools. To protect the system against non-conformities, new ways of automatic checking have been developed and implemented. These checks are regularly and systematically executed by the LHC operation team to ensure that the system status is after each test "as good as new". The sanity checks are part of this strategy. They are testing the electrical part of the detectors (ionisation chamber or secondary emission detector), their cable connections to the front-end electronics, further connections to the back-end electronics and their ability to request a beam abort. During the installation and in the early commissioning phase, these checks have shown their ability to find also non-conformities caused by unexpected failure event scenarios. In every day operation, a non-conformity discovered by this check inhibits any further injections into the LHC until the check confirms the absence of non-conformities.

BLM System for LINAC and Booster at SSRF

A beam loss monitoring (BLM) system for a linear accelerator (LINAC) and booster has been designed and implemented at the Shanghai Synchrotron Radiation Facility, which is under construction. It is a distributed system, constructed with 54 detectors, 11 data collectors, and a console personal computer. Several experiments were made at the National Synchrotron Radiation Laboratory to verify the performance of this system, and one comparison experiment with thermoluminescent dosimeters for dose rate measurement was also done. From preliminary experiments and commissioning, this BLM system is proving to be functional and a useful tool to study the machine status. Moreover, it is hoped that this can be developed into a new method to measure the radiation dose distribution around the LINAC and booster directly, which would help the shielding calculation for future facilities, although more quantitative experiments are needed.

Design and construction of the first prototype ionization chamber for CSNS and PA beam loss monitor (BLM) system

Design and construction of the first prototype ionization chamber for CSNS and Proton Accelerator (PA) beam loss monitor (BLM) system is reported. The low leakage current (<0.1 pA), good plateau (≈800 V) and linearity range up to 200 Roentgen/h are obtained in the first prototype. All of these give us good experience for further improving the ionization chamber construction.

Beam Loss Monitor System for SSRF Storage Ring

A Beam Loss Monitor (BLM) system has been designed for Shanghai Synchrotron Radiation Facility (SSRF). The BLM system is utilized to detect beam loss around the electron storage ring. It will be helpful to find out the position of vacuum leakage, regulate the machine operation parameters, and study the beam lifetime. This paper will discuss some considerations in the BLM system design, including the detector selection, the beam loss mechanism, the detector location along the ring, and the structure of BLM system.

Simulations and Measurements of Secondary Electron Emission Beam Loss Monitors for LHC

Secondary Emission Monitor (SEM) is a part of the LHC Beam Loss Monitoring system, which is providing the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. SEM detectors will be used in the high dose rate environments of LHC because of their low sensitivity and excellent linearity. The design of SEM consists of two bias electrodes separating the produced secondary electrons from the Ti signal electrode placed in a vacuum steel cylinder. The response of the chamber was tested with bunched and continuous proton beams and compared with a reference detector and GEANT4 simulations.

FLUKA Monte Carlo simulations and benchmark measurements for the LHC beam loss monitors

One of the crucial elements in terms of machine protection for CERN's Large Hadron Collider (LHC) is its beam loss monitoring (BLM) system. On-line loss measurements must prevent the superconducting magnets from quenching and protect the machine components from damages due to unforeseen critical beam losses. In order to ensure the BLM's design quality, in the final design phase of the LHC detailed FLUKA Monte Carlo simulations were performed for the betatron collimation insertion. In addition, benchmark measurements were carried out with LHC type BLMs installed at the CERN-EU high-energy Reference Field facility (CERF). This paper presents results of FLUKA calculations performed for BLMs installed in the collimation region, compares the results of the CERF measurement with FLUKA simulations and evaluates related uncertainties. This, together with the fact that the CERF source spectra at the respective BLM locations are comparable with those at the LHC, allows assessing the sensitivity of the performed LHC design studies.

Prototype of linac BLM at NSRL

A prototype of the Beam Loss Monitoring (BLM) System for the linac and transportation line has been built up in National Synchrotron Radiation Laboratory. Different from the storage ring, the radiation field around linac and transportation line have a duty factor of 10 −6 and a dose rate of hundreds Gy/h. The Monte-Carlo calculation gave the dose, flux, energy and direction distributions of the radiation field. According to the simulation result, the proper type of detector was chosen and the installation positions were selected accordingly. The widely used ionization chamber is not suitable to give accurate and real-time information of beam loss due to its large dimension and slow respond speed. Several PIN silicon diode-based detectors were designed and tested, and a charge-balanced integrating amplifier circuit was applied to read out the charge. A distributed data acquisition system based on embedded Ethernet technology was implemented in the prototype, which can offer a web server from the microcontroller. From preliminary tests, this new prototype was proved to be sensitive to the change of the linac status, and is a useful tool for monitoring and adjusting machine parameters. Further analyses are required to achieve a more accurate measurement of the beam loss.

Design of the beam loss monitoring system in strong prompt radiation field

It is inescapable that some electrons will be lost when they are accelerated or transported in the accelerator vacuum chamber. A beam loss monitoring (BLM) system, which works by the radiation measurement, has been successfully installed on the storage ring. Next on the schedule is design of the BLM system for LINAC and transport line. The radiation field around the LINAC and transport line consists of a strong prompt mixed (gamma, neutron) one. Its duty factor is only 10 −6 at Hefei Light Source (HLS). A detector based on counting cannot be used here, while one based on integral charge may be suitable in such a field. The most effective detected objects for estimating beam loss by radiation measurement are shower electrons because they can indicate the beam loss position more clearly than γ rays. The detector also should have the ability to decrease stray radiation influence in strong prompt radiation field. For the requirements mentioned above, a new kind of photodiode detector is being developed. We analyzed the beam transportation process and calculated relevant parameters. Then the positions where the detectors should be fixed were determined. The CAN bus mode we use for the storage ring BLM system is out of date because of the rapid development in the communication field. TCP/IP communication is used for the new system.

Design of Ion Chamber for Beam Loss Monitor of PEFP

A beam loss monitoring system is being designed for PEFP(Proton Engineering Frontier Project) by Korea Atomic Energy Research Institute(KAERI). The beam loss monitoring system is based on the ion chamber and an electrometer. An air-filled ion chamber was designed and fabricated as a prototype detector of beam loss monitor. The radiation response of the ion chamber was simulated by using EGSnrc code. The collection efficiency and stability of the ion chamber with respect to the different radii of inner electrodes is discussed. The proper choice of high voltage bias polarity for the ion chamber is also studied. The test of the ion chamber under high dose rate is under way at KAERI gamma irradiation facility at the exposure rate of 106R/h.

Compton diodes as diagnostic tools in accelerator operation

We report on the development and application of robust, inexpensive bremsstrahlung detectors, so called Compton diodes, for a photon energy from 5 MeV to more than 130 MeV . The detector signal is estimated from a simple analytical model and compared with a more quantitative description of the detector behaviour obtained from numerical simulations and with experimental results for photon energies between 6 and 72 MeV . For the S-DALINAC, a beam loss monitoring system using Compton diodes as detectors has been designed and installed. The detectors were also used for other applications like the investigation of dark current emission from the superconducting cavities at the TESLA Test Facility (TTF) at DESY.

The radiation measurement applied to beam lifetime study on the synchrotron radiation facilities

To collect beam loss information from an accelerator radiation field is helpful to machine study and operation. For a synchrotron radiation storage ring, shower electrons give a distinct clue to loss location and a BLM-XS model detector is suitable to detect them. Recently, we set up a new beam loss monitoring system by this method for National Synchrotron Radiation Laboratory (NSRL) storage ring. It does not interfere with the vacuum chamber and machine operation. Different from other systems, the detectors are used in pairs, fixed on opposite sides of the chamber separately. Some interesting phenomena about beam lifetime were observed. We located exactly where an excessive beam loss took place during ramping process and solved the problem. It was proved that gas accumulated at the front ends of photo-beam lines strongly impacted the electron beam and led to beam lifetime decreases. The cause of beam lifetime decrease because of superconducting wiggler is discussed.

Data acquisition system for BLM at NSRL

A Beam Loss Monitoring (BLM) System has been built up for the 800MeV storage ring in National Synchrotron Radiation Laboratory. It has helped to resolve some problems about beam lifetime. This paper introduces the data acquisition system of BLM. It has a counter whose counting rate is higher than 10MHz. Furthermore, this counter is a free running one that will never lose any pulse when it is being read or written. This DAQ system is composed of 14 front-ends and a console connected via CAN bus. The intensity, distribution and time information of the beam loss can be offered by this system. This BLM system is helpful for machine study and operation.

The beam loss monitoring system for HLS storage ring

A beam loss monitoring system has been established at HLS. This paper gives its principle and scientific grounds. Study on the ring's TBA structure and utilization of Monte-Carlo calculation to the shower electrons is important in its design. The system composition and performance are also introduced. The detector BLMs, data acquisition devices and host PC are linked via CAN bus. This system is helpful to analyze beam loss distribution and regulate the machine operation parameters.

Fail-safe ion chamber beam loss monitor system for personnel protection

A fail-safe beam loss monitor system has been designed for use in the Los Alamos Neutron Scattering Center (LANSCE) Radiation Security System (RSS). The latest version (Model III) has been in use since 1991. This system has been carefully designed to protect personnel from large radiation doses caused by errant beam conditions during beam transport. Due to limited shielding between the beam transport lines and occupied areas, personnel can safely occupy these areas only if the beam losses in the transport lines are sufficiently low. Although the usual solution is to increase the bulk shielding between the beam lines and the occupied areas, the physical dimensions of the site do not permit additional shielding to be added. In this paper we will discuss the design and implementation of the fail-safe beam loss monitor system.