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

ESS nBLM: Beam Loss Monitors based on Fast Neutron Detection

International audienceA new type of Beam Loss Monitor (BLM) system is being developed for use in the European Spallation Source (ESS) linac, primarily aiming to cover the low energy part (proton energies between 3-100 MeV). In this region of the linac, typical BLM detectors based on charged particle detection (i.e. Ionization Cham-bers) are not appropriate because the expected particle fields will be dominated by neutrons and photons. Another issue is the photon background due to the RF cavities, which is mainly due to field emission from the electrons from the cavity walls, resulting in brems-strahlung photons. The idea for the ESS neutron sensi-tive BLM system (ESS nBLM) is to use Micromegas detectors specially designed to be sensitive to fast neutrons and insensitive to low energy photons (X and gammas). In addition, the detectors must be insensitive to thermal neutrons, because those neutrons may not be directly correlated to beam losses. The appropriate configuration of the Micromegas operating conditions will allow excellent timing, intrinsic photon back-ground suppression and individual neutron counting, extending thus the dynamic range to very low particle fluxes