Heavy-ion induced scintillation is accompanied by interesting effects which are mainly due to secondary electrons. These electrons are produced during the stopping of the primary projectiles. Strong signatures of such effects like recombination and the formation of a halo around the projectile’s trajectory will be presented and discussed. Two experiments in which this plays an important role have recently been performed at the Munich Tandem accelerator. In a study in collaboration with GSI/FAIR about optical beam diagnostics appropriate target gases and emission lines were identified, and effective emission cross sections were measured. In these experiments target gas pressures down to about 10−5 mbar were used which can be tolerable under beamline conditions. A pronounced halo appears around the beam at a pressure of about 1 mbar. Comparable to a ’halo’ around the whole beam are ’track-effects’ around individual projectiles at high target densities. These tracks were studied in a model-setup of a liquid argon-xenon scintillation detector. It had been found that an admixture of 10 ppm xenon to argon leads to a very strong near infrared (IR) emission at a peak wavelength of 1173 nm in addition to the well-known vacuum ultraviolet (VUV) scintillation. Here we could show that the IR/VUV intensity ratio of the scintillation light depends on the type of projectile and its energy. Eight different projectiles from the Munich Tandem accelerator were tested. The results are interpreted by the thermal conditions in the projectile’s tracks and are highly promising for using the IR/VUV intensity ratio for particle identification and background suppression in rare-event physics.
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Meeting ID: 984 5733 2925 Passcode: 979953
Peter Thirolf, Norbert Kaiser