The LXePET detector

The LXePET detector is a liquid xenon (LXe) Time Projection Chamber (TPC) viewed by Large Area Avalanche Photodiodes (LAAPDs). Gamma rays entering the detector from the cathode side interact with liquid xenon producing scintillation light and ionization charge. The ionization electrons are detected without gain on electrods after drifing up to 12 cm under an applied electric field of 1-3 kV/cm. The scintillation light is measured by the LAAPDs.
The anode module consists of a shielding grid, a layer of wires preceding the anode, and an anode segmented into strips perendicular to the wires. The electron signal induced on the wires and collected by the anode strips provide the 2D position (x-y) of interaction. The z coordinate is calculated from the drift time and the drift velocity. The amplitude of the pulse on the strip is proportional to the energy deposited in the interaction.

The micro-LXePET scanner under development consists of twelve trapezoidal TPCs arranged in a ring geometry with 10 cm inner bore diameter and 10 cm axial length. The PET detector ring is placed in a vessel filled with LXe located inside a vacuum cryostat. Each sector is a LXeTPC viewed by 2 arrays of LAAPDs.