Off-Axis Characterisation of the CERN T10 Beam for low Momentum Proton Measurements with a High Pressure Gas Time Projection Chamber

Instruments, vol. 4, pp. 21

Abstract

We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.

Authors 6

1. C. Betancourt

   University of Zurich

   Affiliation as printed

   Physik-Institut, Universität Züriche, Rämistrasse 71, 8006 Zürich, Switzerland

2. D. Brailsford

   Lancaster University

   Affiliation as printed

   Department of Physics, Lancaster University, Bailrigg, Lancaster LA1 4YW, UK

3. L. Cremonesi

   University College London

   Affiliation as printed

   Department of Physics and Astronomy, University College London, Gower St, Kings Cross, London WC1E 6BT, UK

4. J. Monroe

   Royal Holloway University of London

   Affiliation as printed

   Department of Physics, Royal Holloway, University of London, Egham Hill, Egham TW20 0EX, UK

5. N. Serra

   University of Zurich

   Affiliation as printed

   Physik-Institut, Universität Züriche, Rämistrasse 71, 8006 Zürich, Switzerland

6. A. V. Waldron

   Imperial College London

   Affiliation as printed

   The Blackett Laboratory, Imperial College London, London SW7 2BW, UK