Single-quantum annihilation and two-quantum annihilation-in-flight measurements of electron distributions using channeled positrons

The goal of our experiments is to combine the channeling technique with single-quantum annihilation (SQA) and two-quantum annihilation-in-flight (TQAF) in order to measure electron distributions in a crystal. In SQA the incoming positron annihilates with an inner shell electron, while in TQAF the positron can annihilate with any electron in the crystal. We can use the channeling effect to steer the positrons in the crystal, and the measured annihilation rates will reflect the electron density in the region the positrons go through. We are upgrading the 3 MeV positron accelerator at Lawrence Livermore National Laboratory (LLNL) to become a new intense source of the monochromatic, MeV positrons required for channeling, and we are constructing a new beamline for these experiments.