On the suitability of longitudinal profile measurements using Coherent Smith-Purcell radiation for high current proton beams

The use of Smith-Purcell radiation to measure electrons longitudinal profiles has been demonstrated at several facilities in the picosecond and sub-picosecond range. There is a strong interest for the development of non intercepting longitudinal profile diagnostics for high current proton beams. We present here results of simulations on the expected yield of longitudinal profile monitors using Smith-Purcell radiation for such proton beams.Comment: Presented at IPAC 2014 - THPME08

Development of Beam Conditions Monitor for the ATLAS experiment

If there is a failure in an element of the accelerator the resulting beam losses could cause damage to the inner tracking devices of the experiments. This thesis presents the work performed during the development phase of a protection system for the ATLAS experiment at the LHC. The Beam Conditions Monitor (BCM) system is a stand-alone system designed to detect early signs of beam instabilities and trigger a beam abort in case of beam failures. It consists of two detector stations positioned at z=±1.84m from the interaction point. Each station comprises four BCM detector modules installed symmetrically around the beam pipe with sensors located at r=55 mm. This structure will allow distinguishing between anomalous events (beam gas and beam halo interactions, beam instabilities) and normal events due to proton-proton interaction by measuring the time-of-flight as well as the signal pulse amplitude from detector modules on the timescale of nanoseconds. Additionally, the BCM system aims to provide a coarse instantaneous luminosity measurement complementary to the main ATLAS luminosity monitor. Radiation hard sensor devices capable of producing fast signals with 1MIP sensitivity were required for the BCM system. Two different sensor materials were considered: Polycrystalline Chemical Vapour (pCVD) diamond and n-type thin epitaxial (epi) silicon. The annealing study of irradiated epi samples at an annealing temperature of 20oC proved the epi material to be radiation hard in terms of effective dopant concentration. The results were found to agree with the results obtained by a different group at elevated annealing temperatures. However, the performance of epi devices was measured to be inferior to pCVD diamond sensors in terms of BCM detector module signal to noise ratio. Thus, the pCVD diamond was chosen for the BCM sensor material in the end. Numerous measurements have been performed during the development in order to optimise the BCM system performance. These incorporate characterisation of the diamond sensors, tests of the detector modules with test beam pions and 90Sr electrons as well as tests with the digitisation electronics included. The most relevant results are discussed here. An estimate of the expected BCM system performance at the end of readout chain in ATLAS is also given

Characterization of proton and neutron irradiated low resistivity p-on-n magnetic Czochralski ministrip sensors and diodes

Transient Current Technique (TCT) and Charge Collection Efficiency (CCE) measurements were performed on low resistivity (280Ωcm) n-bulk, p-readout magnetic Czochralski ministrip sensors and diodes. The detectors were irradiated with neutrons and 24 GeV/c protons up to a total NIEL equivalent fluence of 8×10 15/ cm2. The study was addressed to assess the radiation tolerance of the detectors up to fluences expected in the next generations of High Energy Physics experiments. The charge collection efficiency after irradiation was found to be much higher than for standard FZ silicon p-in-n sensors. The underlying physics of this remarkable result was investigated by performing Edge-TCT measurements on one of the neutron irradiated ministrip sensors to extract detailed informations about the field and efficiency profiles of the detector. © 2011 Elsevier B.V

Detector Response Studies of the ESS Ionization Chamber

The European Spallation Source (ESS), currently under construction in Lund, Sweden, will be a pulsed neutron source based on a proton linac. The ESS linac is designed to deliver a 2GeV beam with peak current of 62.5mA at 14 Hz to a rotating tungsten target for neutron production. One of the most critical elements for protection of an accelerator is a Beam Loss Monitoring (BLM) system. The system is designed to protect the accelerator from beam-induced damage and unnecessary activation of the components. The main ESS BLM system is based on ionization chamber (IC) detectors. The detector was originally designed for the LHC at CERN resulting in production of 4250 monitors in 2006-2008. In 2014-2017 a new production of 830 detectors with a modified design was carried out to replenish spares for LHC and make a new series for ESS and GSI. This contribution focuses on the results from a measurement campaigns performed at the HRM (High-Radiation to Materials) facility at CERN, where detector response of the ESS type IC has been studied. The results may be of interest for other facilities, that are using existing or plan to use new generation of LHC type IC monitors as BLM detectors

New Neutron Sensitive Beam Loss Monitor (nBLM)

International audienceThe beam loss detection is of the utmost importance for accelerator safety. At CEA, we are closely collaborating with ESS and DMCS on development of ESS nBLM. The system is based on Micromegas* gaseous detector sensitives to fast neutrons produced when beam particles hit the accelerator materials. This detector has powerful features: reliable neutron detection and fast time response. The nBLM control system provides slow monitoring, fast security based on neutron counting and post mortem data. It is fully handled by EPICS, which drives 3 different subsystems: a Siemens PLC regulates the gas line, a CAEN crate controls low and high voltages, and a MTCA system based on IOxOS boards is in charge of the fast data processing for 16 detectors. The detector signal is digitized by the 250 Ms/s ADC, which is further processed by the firmware developed by DMCS and finally retrieved and sent to EPICS network. For other accelerator projects, we are designing nBLM system close to ESS nBLM one. In order to be able to sustain the full control system, we are developing the firmware and the driver. This paper summarizes CEA’s work on the nBLM control system for the ESS and other accelerators

FPGA-based Data Processing in the Neutron-Sensitive Beam Loss Monitoring System for the ESS Linac

International audienceThe European Spallation Source (ESS), which is currently under construction, will be a neutron source based on 5 MW, 2 GeV superconducting proton linac. Among other beam instrumentation systems, this high intensity linac requires a Beam Loss Monitoring (BLM) system. An important function of the BLM system is to protect the linac from beam-induced damage by detecting unacceptably high beam loss and promptly inhibiting beam production. In addition to protection functionality, the system is expected to provide the means to monitor the beam losses during all modes of operation with the aim to avoid excessive machine activation. This paper focuses on the FPGA implementation of the real-time data processing in the nBLM system and presents preliminary result of a prototype system installed at LINAC4 at CERN

Neutron sensitive beam loss monitoring system for the European Spallation Source linac

International audienceThe European Spallation Source (ESS), currently under construction in Lund, Sweden, will be a neutron source based on a partly superconducting linac. The ESS linac will be accelerating protons to 2 GeV with a peak current of 62.5 mA and ultimately delivering a 5 MW beam to a rotating tungsten target for neutron production. For a successful tuning and operation of a linac, a beam loss monitoring (BLM) system is required. BLM systems are designed to protect the machine from beam-induced damage and unnecessary activation of the components. This paper focuses on one of the BLM systems to be deployed at the ESS linac, namely the neutron sensitive BLM (nBLM). An overview of the ESS nBLM system design will be presented. In addition to this, results of the tests performed with the full nBLM data acquisition chain will be discussed. These tests represent the first evaluation of the system prototype in a realistic environment. They served as an input to initial study of the procedure for neutron detection algorithm configuration discussed in this contribution as well

A Micromegas Based Neutron Detector for the ESS Beam Loss Monitoring

International audienceBeam loss monitors are of high importance in high-intensity hadron facilities where any energy loss can produce damage or/and activation of materials. A new type of neutron BLM have been developed for hadron accelerators aiming to cover the low energy part. In this region typical BLMs based on charged particle detection are not appropriate because the expected particle fields will be dominated by neutrons and photons. Moreover, the photon background due to the RF cavities can produce false beam loss signals. The BLM proposed is based on gaseous Micromegas detectors, designed to be sensitive to fast neutrons and insensitive to photons (X and gamma). In addition, the detectors will be insensitive to thermal neutrons, since part of them will not be directly correlated to beam loss location. The appropriate configuration of the Micromegas operating conditions will allow excellent timing, intrinsic photon background suppression and individual neutron counting, extending thus the dynamic range to very low particle fluxes. The concept of the detectors and the first results from tests in several facilities will be presented. Moreover, their use in the nBLM ESS system will be also discusse

Characterization and First Beam Loss Detection with One ESS-nBLM System Detector

International audienceThe monitoring of losses is crucial in any accelerator. In the new high intensity hadron facilities even low energy beam can damage or activate the materials so the detection of small losses in this region is very important. A new type of neutron beam loss monitor has been developed specifically targeting this region, where only neutrons and photons can be produced and where typical BLM, based on charged particle detection, could not be appropriate because of the photon background due to the RF cavities. The BLM proposed is based on gaseous Micromegas detectors, designed to be sensitive to fast neutrons and with little sensitivity to photons. Development of the detectors presented here has been done to fulfil the requirements of ESS and they will be part of the ESS-BI systems. The detector has been presented in previous editions of the conference. Here we focus on the neutron/gamma rejection with the final FEE and in the first operation of one of the modules in a beam during the commissioning of LINAC4 (CERN) with the detection of provoked losses and their clear separation from RF gammas. The ESS-nBLM system is presented in this conference in a separate contribution

Non-invasive Profilers for the Cold Part of ESS Accelerator

International audienceSeveral Non-invasive Profile Monitors are being in-stalled along the accelerator to support the commissioning, tuning and operation of the powerful proton based ESS linear accelerator. In the low energy parts of the ESS linac (3.6 MeV to 90 MeV), the residual gas pressure is high enough to measure the transverse beam profile by using fluorescence induced by the beam on the gas molecules. However, in the ESS linac sections above 90 MeV, protons are accelerated by superconductive cavities working at cryogenic temperatures and high vacuum. Therefore, the signal based on the fluorescence process is too weak, while ionization can counteract this drawback. We have provided five IPM (Ionization Profile Monitors) pairs for energies ranging from 100 to 600 MeV. The design of such monitors is challenging due to weak signal (as a result of high proton energy and low pressure <10-9 mbar), tight space constraints inside the vacuum chamber, space charge effect, ISO-5 cleanliness requirement, and electrode polarization at ±15 kV. This publication will detail the development we followed to fulfil the ESS requirements