The Positron User Facility at the PULSTAR Nuclear Reactor Applications in Materials Studies and Recent Upgrades

Abstract:

The PULSTAR nuclear reactor at North Carolina State University is a 1-MWth open-pool reactor and a center for irradiation and examination of materials. Among the different facilities based on this reactor, an intense positron beam facility has been established and operational since 2009, providing a positron beam reaching 6 × 10⁸ e⁺/s and two positron beam spectrometers. This facility has been recently upgraded in several aspects in terms of sample manipulation and heating/cooling capabilities, as well as coincidence Doppler Broadening Spectroscopy (CDBS) capability, enabled by a new sample changer and target chamber with new digital MCA systems. Currently, both beam and bulk spectrometers can perform CDBS and Positron Annihilation Lifetime Spectroscopy (PALS) with varying temperature settings. In addition, environmental control has also been added to the bulk system, where the sample pressure and humidity can be adjusted together with temperature. These systems have been utilized to study a variety of nuclear-related materials, such as metal alloys and oxide compounds, that had undergone surface and bulk damages induced by radiation. Such materials are widely used as structural and sensor materials related to nuclear reactors where microstructural damage is critical in determining their performance and failure modes. Some of the studies also demonstrated the unique advantage of Positron Annihilation Spectroscopy (PAS) over other traditional characterization techniques.

• Periodical: Solid State Phenomena (Volume 374)
• Pages: 155-161
• DOI: https://doi.org/10.4028/p-x8U404
• Online since: July 2025
• Authors: Ming Liu*, Yasmin Akter, Aidana Bauyrzhan, Ayman Hawari
• Keywords: CDBS, Doppler Broadening Spectroscopy, Positron Annihilation, PULSTAR

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