A. Fabich

A High-Power Target Experiment

We describe an experiment designed as a proof-of-principle test for a target system capable of converting a 4-MW proton beam into a high-intensity muon beam suitable for incorporation into either a neutrino factory complex or a muon collider. The target system is based on exposing a free mercury jet to an intense proton beam in the presence of a high-strength solenoidal magnetic field.

An R&D program for targetry and capture at a neutrino factory and muon collider source

The need for intense muon beams for muon colliders and for neutrino factories based on muon storage rings leads to a concept of 1-4 MW proton beams incident on a moving target that is inside a 20-T solenoid magnet, with a mercury jet as a preferred example. Novel technical issues for such a system include disruption of the mercury jet by the proton beam and distortion of the jet on entering the solenoid, as well as more conventional issues of materials lifetime and handling of activated materials in an intense radiation environment. As part of the R&D program of the Neutrino Factory and Muon Collider Collaboration, an R&D eort related to

A high-power target experiment at the CERN PS

We test a target concept devised for the purpose of producing copious secondary pions and capturing the muon decay products. This experiment is designed to test the target system for a neutrino factory or muon collider and consists of a free flowing mercury stream embedded in a high-field solenoid. Key components are described.

Systems testing of a free hg jet system for use in a high-power target experiment

The design and operational testing of a mercury jet delivery system is presented. The equipment is part of the Mercury Intense Target (MERIT) Experiment, which is a proof-of-principle experiment to be conducted at CERN in the summer of 2007 to determine the feasibility of using an unconstrained jet of mercury as a target in a Neutrino Factory or Muon Collider. The Hg system is capable of producing a 1 cm diameter, 20 m/s jet of Hg inside a high-field solenoid magnet. A high-speed optical diagnostic system allows observation of the interaction of the jet with a 24 GeV proton beam. Performance of the Hg system will be presented, along with results of integrated systems testing without a beam.

Experimental observation of proton-induced shocks and magneto-fluid-dynamics in liquid metal

Abstract A liquid metal target is one of the options for the pion production target of a ν-factory. The interaction between a liquid metal and a proton beam were observed with static mercury as well as with a free mercury jet and up to 4×1012 protons/bunch. The experimental method for investigating the magneto-fluid-dynamic effects of a high-velocity liquid metal in a high magnetic field magnet has been validated by recording the behaviour of a 15 m/s mercury burst entering the gradient of a 13 T solenoid at GHMFL Grenoble. The paper includes the description of the optical read-out system as well as numerical results of the mercury drop velocities.

High purity 100 GeV electron identification with synchrotron radiation

Abstract In high energy experiments such as active beam dump searches for rare decays and missing energy events, the beam purity is a crucial parameter. In this paper we present a technique to reject heavy charged particle contamination in the 100 GeV electron beam of the H4 beam line at CERN SPS. The method is based on the detection with BGO scintillators of the synchrotron radiation emitted by the electrons passing through a bending dipole magnet. A 100 GeV π − beam is used to test the method in the NA64 experiment resulting in a suppression factor of 10 −5 while the efficiency for electron detection is ∼ 95%. The spectra and the rejection factors are in very good agreement with the Monte Carlo simulation. The reported suppression factors are significantly better than previously achieved.

Response of a tungsten powder target to an incident high energy proton beam

The experiment described in this paper is the first study of the response of a static tungsten powder sample to an impinging high energy proton beam pulse. The experiment was carried out at the HiRadMat facility at CERN. Observations include high speed videos of a proton beam induced perturbation of the powder sample as well as data from a laser Doppler vibrometer measuring the oscillations of the powder container. A comparison with a previous analogous experiment which studied a proton beam interaction with mercury is made

The radiation field in the Gamma Irradiation Facility GIF++ at CERN

Abstract The high-luminosity LHC (HL-LHC) upgrade is setting now a new challenge for particle detector technologies. The increase in luminosity will produce a particle background in the gas-based muon detectors that is ten times higher than under conditions at the LHC. The detailed knowledge of the detector performance in the presence of such a high background is crucial for an optimized design and efficient operation after the HL-LHC upgrade. A precise understanding of possible aging effects of detector materials and gases is of extreme importance. To cope with these challenging requirements, a new Gamma Irradiation Facility (GIF++) was designed and built at the CERN SPS North Area as successor of the Gamma Irradiation Facility (GIF) during the Long Shutdown 1 (LS1) period. It features an intense source of 662 keV photons with adjustable intensity, to simulate continuous background over large areas, and, combined with a high energy muon beam, to measure detector performance in the presence of the background. The new GIF++ facility has been operational since spring 2015. In addition to describing the facility and its infrastructure, the goal of this work is to provide an extensive characterization of the GIF++ photon field with different configurations of the absorption filters in both the upstream and downstream irradiation areas. Moreover, the measured results are benchmarked with Geant4 simulations to enhance the knowledge of the radiation field. The absorbed dose in air in the facility may reach up to 2.2 Gy/h directly in front of the irradiator. Of special interest is the low-energy photon component that develops due to the multiple scattering of photons within the irradiator and from the concrete walls of the bunker.

Performance of Multiplexed XY Resistive Micromegas detectors in a high intensity beam

Abstract We present the performance of multiplexed XY resistive Micromegas detectors tested in the CERN SPS 100 GeV/c electron beam at intensities up to 3 . 3 × 1 0 5 e − ∕ ( s ⋅ cm 2 ) . So far, all studies with multiplexed Micromegas have only been reported for tests with radioactive sources and cosmic rays. The use of multiplexed modules in high intensity environments was not explored due to the effect of ambiguities in the reconstruction of the hit point caused by the multiplexing feature. For the specific mapping and beam intensities analyzed in this work with a multiplexing factor of five, more than 50% level of ambiguity is introduced due to particle pile-up as well as fake clusters due to the mapping feature. Our results prove that by using the additional information of cluster size and integrated charge from the signal clusters induced on the XY strips, the ambiguities can be reduced to a level below 2%. The tested detectors are used in the CERN NA64 experiment for tracking the incoming particles bending in a magnetic field in order to reconstruct their momentum. The average hit detection efficiency of each module was found to be ∼ 96% at the highest beam intensities. By using four modules a tracking resolution of 1.1% was obtained with ∼ 85% combined tracking efficiency.

HiRadMat: A high-energy, pulsed beam, material irradiation facility

HiRadMat is a recently constructed facility designed to provide high-intensity pulsed beams to an irradiation area where different material samples or accelerator components can be tested. The facility, located at the CERN SPS accelerator complex, uses a 440 GeV proton beam with a pulse length up to 7.2 μs and a maximum intensity up to 1013 protons / pulse. The facility, a unique place for performing state-of-the art beam-to-material experiments, operates under transnational access and welcomes and financially supports, under certain conditions, experimental teams to perform their experiments.