Design of a Radial TPC for Antihydrogen Gravity Measurement with ALPHA-g

Gaseous and dual-phase time projection chambers for imaging rare processes

“…Some other recent TPC proposals devoted to the imaging of rare processes, at different stages of development, involve i) the triple GEM-based HypTPC, for searches of the H-dibaryon at high incoming beam rates (around 10 5 -10 6 Hz/cm 2 ) at J-PARC [405]; ii) the thick GEM-based TPC for the study of deeply-bound kaonic clusters (also at J-PARC) [406]; iii) the ββ0ν xenon TPC of the AXEL experiment [407], that relies on a very thick (5-10 mm) GEMlike teflon structure coupled to VUV-sensitive SiPMs; iv) the recently proposed active target TPC for γ-spectroscopy at ELI [408]; and v) the ALPHA-g experiment, that aims at a measurement of the gravitational force over antihydrogen, by continuously monitoring its decay to pions under free-fall conditions [409]. Recent imaging TPCs whose subject of study can be hardly categorized as 'rare process' include those devoted to precision measurements of the neutron lifetime [410], study of fission [411], and low energy nuclear reactions [412].…”

Laser-cooled Be+ for improved antihydrogen trapping and magnetometry

“…Pions give a "hit" signal in the position they pass through each silicon layer, and having three layers allows reconstructing their trajectory. Silicon detectors are expensive, so for the ALPHA-g trap, which is around 3 times longer, a radial Time Projection Chamber (rTPC) is used [113]. The time projection chamber is a gas detector in which charged particles are detected by ionising the gas mixture (90% argon + 10% CO 2 ) as they pass through a detector volume.…”