Ultra-slow negative muon production via muon catalyzed fusion

1989 Proceedings of the Japan Academy. Series B, Physical and biological sciences  
Communicated by Minoru ODA, M. J. A., Dec. 12, 1989) So far, various ideas have been proposed for the production of an intense slow positive muon (p+) beam.l> The basic concept underlying these ideas is the reduction of the phase-space volume by re-emission of the p+ after theremalization within a small source volume (brightness enhancement). For the case of negative muon (p1, it has been considered to be very difficult to produce an intense slow r beam due to the following difficulties : (1)
more » ... ifficulties : (1) because of a strong absorption of stopped ~r-inside the matter, the it to p decay can not be realized in the target material, so that there is no surface u-except a small probability for liquid H2 or He; (2) because of the muonic atom formation, the stopped pcan not be liberated from the stopping material after themalization inside the condensed matter ; no brightness enhancement can be expected in the case of p-. Here, in order to overcome the second difficulty, we propose an entirely new idea for the source of slow p-which will be realized with the help of celebrated phenomena of muon catalyzed fusion.2) As it is known in our present knowledge on muon catalyzed fusion (pCF), the basic process of the pCF in the high density D-T mixture proceeds as schematically shown in Fig. 1a . The process which takes place at the instant of the fusion reaction inside the muon molecule can be seen in more details in Fig. 1b . There, most of the p-(more than 99%) which is once bound to 5He nucleus is liberated because of a disappearance of the core-nucleus which changes into 14 MeV neutron and 3.6 MeV 4He, while only a small fraction (below 1%) of the p-is sticked to 4He. The binding energy of the p-in (p-5He) is 11 keV. The exact energy (momentum) distribution should be considered as a Fourier transform of the atomic wave function of the (p-5He) with the correction due to the Coulomb interaction between p-and a in flight.4~ In any case, in the process of each pCF cycle, the p-is liberated with an average energy of around 10 keV. According to our knowledge, this i-liberation process could take place up to 150 times during the p-life time.3> Recently the small sticking probability of the r to 4He was directly observed by detecting a characteristic X-ray from the (p-4He) atom for the first time for high density as well as high T2 concentration D-T mixture by UTMSL-;RIKEN-JAERI collaboration carried out at UT-MSL/KEK.2)>5) Then, let us consider the situation as is seen in Fig. 2 . The MeV i -is stopped in a thin layer of condensed D2 T2 mixture. The one MeV p-which is without much difficulties obtained by the pion decay in flight is now stopped in the thin layer of condensed D2/T,. Then, inside this thin layer, the 10 keV p-is successively generated during the pCF processes up to 150 times on the average during the p-life-time. Let us define leff as a range of p-produced at each liberation process before it is captured to form (gd) or (pt) atoms. Also,
doi:10.2183/pjab.65.225 fatcat:3k3x4sw5q5hejear7nr7pob5mm