An improved Feynman-α analysis with a moving-bunching technique

• Published in: Journal of nuclear science and technology Vol. 53; no. 10; pp. 1647 - 1652
• Main Authors: Okuda, Ryohei, Sakon, Atsushi, Hohara, Sin-ya, Sugiyama, Wataru, Taninaka, Hiroshi, Hashimoto, Kengo
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 02.10.2016
• Subjects: analysis; Bunching; Channels; Constants; Counting; Decay; Feynman-α; Neutron detectors; nuclear reactor; reactor kinetics; Scalers; Scatter; subcriticality; UTR
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/00223131.2015.1125310

The bunching technique has been widely utilized in Feynman-α neutron correlation analysis to synthesize neutron counts within longer gate widths by bunching time-sequence neutron counts stored in multichannel scaler channels. An alternative technique referred to as "moving-bunching technique" was proposed to reduce a statistical scatter of variance-to-mean ratio of neutron counts. The conventional bunching technique has no overlap of adjacent bunches, while the present technique makes adjacent bunches overlap as long as possible similarly to the moving average technique. A Feynman-α experiment was performed in the UTR-KINKI, to confirm the advantage of the proposed bunching technique. When a neutron detector was placed far from the core, a Feynman-α analysis with the conventional bunching technique led to a scattered variance-to-mean ratio from which the prompt-neutron decay constant was never determinable. However, another analysis with the proposed technique remarkably reduced the above scatter and enabled the determination of the decay constant. For a neutron detector close to the core, the proposed technique also reduced statistical error of the decay constant.