Muon to alpha sticking K(sub beta)/K(sub alpha) X-ray ratio in muon catalyzed D-T fusion at the RIKEN-RAL Muon Facility

Abstract

The negative muon (mu(-)) to alpha initial sticking probability experimentally observed is smaller than that of theoretically calculated with nuclear reaction theory. However, it is difficult to identify which causes the discrepancy, the initial sticking probability calculation or the atomic process calculation. Study of the intensity ratio between K(sub beta) and K(sub alpha) X rays from mu(-) alpha atom can contribute much to answer the above question; because such a ratio is nearly independent of the initial sticking process, but is very sensitive to the atomic process. Measurement of the X rays and neutrons from muon catalyzed D-T fusion (deuterium-tritium) was carried out at the RIKEN (Institute of Physical and Chemical Research)-RAL (Rutherford Appleton Laboratory) muon facility. The world highest intensity pulsed muon beam enabled the observation of K(sub beta) X ray for the first time. Experiments to measure the K(sub beta)/K(sub alpha) intensity ratio were performed for D-T mixtures with different tritium concentration. The area of K(sub beta) and K(sub alpha) X ray signals in the energy spectrum was obtained for each tritium concentration, and it was corrected for the difference of attenuation by the materials between D-T target and Si (Li) X ray detector. The averaged K(sub beta)/K(sub alpha) intensity ratios for liquid and solid were 7.5 +/- 1.0 percent and 6.0 +/- 1.2 percent, respectively.

負のミューオン(μ(-))のαへの初期固着確率の実験観測値は核反応理論を用いて計算した理論予測値よりも小さい。しかし初期固着確率計算と原子プロセス計算のどちらが不一致をもたらせているかを明らかにするのは困難である。K(sub β)X線とK(sub α)X線の強度比をμ(-)α原子から研究することはこの問題の解決に役立つ。この比率は初期固着プロセスにほぼ無関係だが、原子プロセスの影響を強く受けるからである。ミューオン媒介D-T(重水素-三重水素)融合からのX線と中性子の測定をRIKEN(理化学研究所)-RAL(ラザフォード・アップルトン研究所)ミューオン装置で実施した。世界最強のパルスミューオンビームによりK(sub β)X線の観測が初めて可能になった。K(sub β)/K(sub α)強度比を測定する実験を、異なる三重水素濃度を持つD-T混合に対して行った。エネルギースペクトルにおけるK(sub β)およびK(sub α)X線信号の面積を、各三重水素濃度から得て、D-T標的試料とSi(Li)X線検知器間の介在物質による減衰に対して補正した。K(sub β)/K(sub α)強度比の平均値は、液体または固体に対してそれぞれ7.5±1.0%または6.0±1.2%であった。