Speaker
Description
Muons are widely used for the various fields in condensed matter physics and fundamental nuclear physics. Muons or parent particles, pions are produced by collision of high energy protons against a target material. A pulsed muon beam and a continuous DC muon beam are selectively used for the purpose of the experiments. In particular, the pulsed muon beam is useful for Muon-Spin-Spectroscopy technique investigating rapid time transient phenomena, detection of rare events with a large background, and studies using devices synchronizing with the proton beam, e.g. high-power pulsed laser to stimulate specimens and so forth. A typical pulsed muon beam is produced by a pulsed proton beam with a time-width of around 100 ns and with a frequency of 20-50 Hz. Then, highly-cyclic and volumetric heating with extremely short-time width is induced by high-energy and pulsed proton beam. Consequently, the compressive-to-tensile stress causes the propagation of the displacement. The wave propagation could severely damage the target material. The HiRadMat Facility at CERN is a unique facility to study the impact of intense pulsed beams on the target materials for the muons and pions production.
Polycrystalline graphite is the principal candidate for production of pions and muons with high-intense proton beam irradiation in different facilities all over the world, because graphite shows an extremely high performance for these applications due to its thermal, mechanical, and other properties. However, graphite is easily oxidized at high temperature. If air is unexpectedly introduced into the primary beamline in vacuum during the high-power beam operation, the rapid oxidation of the graphite target and the consequent mass loss could be detrimental to safe operation. Target materials denser than graphite would be preferable to have a point wise source for secondary beam transport. Therefore, to replace the graphite, it is important to develop the material that is denser while keeping excellent mechanical and thermal properties as well as more resistant to oxidation. Recently, we have been working on investigation of a variety of new materials, such as SiC-coated graphite as an oxidation resistant material, SiC/SiC composite material as a denser and oxidation resistant material, and TFGR (Toughened, Fine Grained, Recrystallized) W-1.1%TiC as an extremely denser material for next-generation pulsed-pions/muons-production targets and other spallation targets. The fabricated specimens of each material were supplied and were successfully irradiated at CERN-HiRadMat Facility. This presentation will address our motivation, the present status, and the prospective outcomes of the thermal shock experiments at CERN-HiRadMat Facility.