Related Experiment Video
Updated: Aug 19, 2025

Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera
Published on: January 30, 2020
Development of gamma-ray-induced positron age-momentum correlation measurement
Yoshitaka Taira1, Ryohei Yamamoto2, Kento Sugita1
1Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki 444-8585, Japan.
Abstract:
In conventional positron annihilation spectroscopy using radioisotopes, source contributions are unavoidable since positrons annihilate in the material covering the radioisotopes. Part of the positrons annihilate within the radioisotopes even when radioisotopes are deposited directly on a sample. Gamma-ray-induced positron annihilation spectroscopy makes it possible to measure only the spectra of a sample without source contributions since positrons are directly generated inside the sample from the gamma rays by pair production and annihilate inside the same sample. In this study, a new positron age-momentum correlation measurement system using ultrashort pulsed gamma rays is developed. The gamma rays with an energy of 6.6 MeV are generated by the inverse Thomson scattering of laser photons by high-energy electrons and are irradiated to the sample. The laser pulse can fully control the timing of gamma-ray generation. This characteristic and the use of a digital oscilloscope with a 12-bit vertical resolution enable us to develop a simple measurement system. Time-resolved momentum distributions for stainless steel with no defects and deformed interstitial free steel show the explicit differences reflecting the type of defect; for BaF2 single crystals, the results have been interpreted by considering the formation of positronium.
Related Concept Videos
Atomic Nuclei: Larmor Precession Frequency
Positron Emission Tomography
One of the main requirements of a PET scan is a positron-emitting radioisotope, which is produced in a cyclotron and then attached to a substance used by the part of the body...
Atomic Emission Spectroscopy: Instrumentation
Atomic Nuclei: Nuclear Spin State Population Distribution
Atomic Emission Spectroscopy: Lab
Atomic Nuclei: Nuclear Magnetic Moment

