Arakatsu, Bunsaku

Saji, Yoshio

Sonda, Masateru

Uemura, Yoshiaki

Yasumi, Shinjiro

Kyoto University Research Information Repository

Title Photo-disintegration of Beryllium by the High Energy γ-RaysAuthor(s)Arakatsu, Bunsaku; Sonda, Masateru; Uemura, Yoshiaki;Yasumi, Shinjiro; Saji, YoshioCitation京都大学化学研究所報告 (1950), 22: 71-72Issue Date1950-09-30URL http://hdl.handle.net/2433/74154RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityNow, if n(E, x) is the number of the electrons of energy E produced by the multiplication process  .  like the cosmic ray shower at the depth x distant from the point where the initial electron of energy  E0 is produced, the total probability of penetration  Pr(E0, x) with which the electron of initial energy  E0 can travel through  thd distance x will be given by  Pr(Eo,  ,X)=  Bo n(E, x) dE  n(E, x) can be obtained by solving the similar diffusion equation as in the shower theory. This, however, is a very difficult problem especially in the case of the intermediate energy under consideration and we were obliged to simplify the equation under some approximate assumption. The calculation was then performed numerically. The final results were shown in the table for the case of the lead counter of the inner diameter 2 cm.                                    Table       wall energy of  y-ray quantum in mc2       thickness   in cm 12 20 25 30 35     0.20 3.7% 9.7% 13.6% 16.0% 17.7%     0.30 3.5 10.4 15.2 19.1 22.4     0.40 3.4 10.2 15.0 19.8 24.4     0.50 3.2 9.7 14.4 19.6 24.7  0.60. 3.1 9.0 13.8 18.8 24.4     0.65 3.0 8.7 13.5 18.3 23.9    1) M. SONODA, J. Phys. Soc. Jap. (in press).   2) B. ROSSI and K. GREISEN, Rev. Mod. Phys. 13, 240 (1941)           6. Photo-disintegration of Beryllium by                     the High Energy  7-Rays.  Bunsaku Arakatsu, Masateru Sonda, Yoshiaki Uemura,  Shinjiro Yasumi and Yoshio Saji.    The photo-disintergration of Beryllium was observed for the  1-rays of energy 17.6  and 6.13 Mev. These  !-rays were obtained by bombarding thick target of Li metal and CaF2 with protons of energy of 500  Key and 350  Key, respectively. The proton beam was unseparated and the intensity was about  30-60  AA. Two  propor-tional counters of methane flow type, were placed near the target, one of which was coated with thick layer of  BeO and the other was uncoated. The Be-counter was 6 cm in diameter  ands20 cm in length. After being amplified by the respective 4-stage  `71)linear amplifier, the pulses from the counters were fed into the deflectors vertical and horizontal respectively, of a Braun-tube oscilloscope, in order to discriminate a spuri-ous pulse due to an accidental electromagnetic induction from the accelerating tube. The output from the Be-counter were also recorded on the printing paper by an  electromagnetic  oscillograph.    When these counters were irradiated by the r-rays, many pulses were observed in the Be-counter, but very few in the uncoated counter. Moreover, the number of observed kicks from the Be-counter was seen to follow exactly the r-ray excitation curves. These facts show that the observed pulses from the Be-counter were definitely due to some processes in Be produced by the r-rays, but not by the contaminated neutrons. The oscillograph records were analysed and the following disintegration schema were concluded.    1)  Be9  +  17.6  Mev  r—Be8*  +n  Be8*--.2a  Be8* in 7 Mev excited state.    2) Be9 +17.6 Mev  r-.Be8 +n  Be8-.2a Be8 in ground state.    3) Be9 +6.13 Mev +n  Be8-2a The cross-sections for these three processes were found to be    1)  2.15  x10-27  cm2    2)  5.1  x  10-26  cm2    3)  1.62x  10-27  cm2 respectively.    The trend of the excitation curve is entirely different from the theory of E. Guth  1). Moreover, it seems noticeable that the excited states of  Be8* of energy 3.0 Mev and 4.8 Mev do not contribute in these processes.    More decisive experiments using photographic emulsion are now in progress.   1) E. Guth and C. Mullin, Phys. Rev., 76, 234 (1949)                 7. Some Experiments on  P32.                   I. Physical Procedures and Measurements.          Sakae Shimizu, Yoshiaki Uemura,  Iseryutaro Ishiwari,                 Osamu Horibe and Sunao Okamoto.   We have produced radioactive phosphorus, P32,  kiy the reaction S32(n,  p)P32. The irradiation of 3.8 liters of CS2 in a spherical flask with a 50 mg. radium-beryllium neutron source placed at the center of the flask, during about 28 days produced sufficient  P32 with a high activity sufficient to support some research programs. The extraction procedures of  P32 from the irradiated CS2 are described in Part  II. The activity of  P32 obtained was measured by an endwindow  (27r-type) G-M counter with a thin mica window  (4  mgicm2). The pulses from the counter were counted by a decade scaler particularly devised for the present experiment.                             ( 72  )

Photo-disintegration of Beryllium by the High Energy γ-Rays

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Photo-disintegration of Beryllium by the High Energy γ-Rays

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