TitleScattering Chamber for Three Body N.

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(1969), 47(2): 154-161 ssue Date 1969-03-31 URL http://hdl.hle.

1 TitleScattering Chamber for Three Body N Author(s) Yanabu, Takuji; Fujita, Hirokazu; G Tatsuya Citation Bulletin of nstitute for Chemi University (1969), 47(2): ssue Date URL Right Type Departmental Bulletin Paper Textversion publisher Kyoto University

2 Bull. nst. Chem. Res., Kyoto Univ., Vol. 47, No. 2, 1969 A Scattering Chamber for Three Body Nuclear Reactions Takuji YANABU*, Hirokazu FUJTA*, Masayuki GoTOx**, Tatsuya WASA** Received March 20, 1969 To study non-coplaner events in three body nuclear reaction, a scattering of three dimensional freedom was constructed, Three sets of radiation detectors could be mounted could move to any position in scattering. Design of some experimental results obtained with this are described.. NTRODUCTON n Laboratory of Nuclear Reaction, nstitute for Chemical Research, scattering of alpha particles by nuclei emission of alpha particles from nuclei have been studied systematically for about eight years." merits of an alpha particle as a nuclear probe particle are : 1, alpha particle is easily absorbed by nucleus, so that one can survey nature of nuclear surface with scattering of alpha particles from nucleus. 2, alpha particle is a tightly bound particle has no spin isobaric spin, refore mechanism of reaction induced by or emitting an alpha particle is simple relative to proton or deuteron induced or producing reactions. 3, alpha particle is a composite particle of nucleons, so that this particle is useful to investigate composite structure of nucleus. That means, overlapping of alpha particle target nucleus is useful to see alpha-like structure of nucleus. From se reasons, collective motion of nucleus alpha cluster structure of nucleus has been studied in laboratory by use of a 30 MeV alpha particle beam from Kyoto University Cyclotron. n early stage of research works, two body reactions were main subject of our investigations, but as research developed, it was felt to be nescessary to construct a scattering with which one can investigate particle-particle or particle-gamma correlations in final state. reasons were as follows. We have become concious about importance of nucleon clustering into alpha clusters in nucleus in alpha particle emitting reactions such as * gra KM,,1 11f (-- : Laboratory of Nuclear Reaction, nstitute for Chemical Research, Kyoto University, Kyoto. ** f 1E2., L fi : Central Research Laboratory, Mitsubishi Electric Corporation, Amagasaki. (154)

3 Three Dimensional Scattering Chamber (d, a) (p, a) reactions. To investigate existence of alpha clusters in nucleus, quasi-free scattering experiment was programmed (a, 2a) reactions on Be', B10, 02, 016 Ne20 have been studied.2' n course of se investigations, a scattering equipped with two moving counters was nescessary was constructed in ' This scattering had two co-axial rotating discs co-planer particle-particle correlation experiment could be done when two counters were set on se discs. Be' (p, pa) He' reaction was studied" with this by use of an FM cyclotron of nstitute for Nuclear Study, University of Tokyo. However, re still remained dissatisfaction with this, because non-coplaner particle-particle correlation could not be measured. We have experienced in investigation of Ne20 (a, 2a) 016 reaction, coincidence spectrum of two alpha particles distributes discontinuously,'' i. e., coincidence events on a kinematical line of two alpha particles leaving residual 016 nucleus in its ground state, gar into several parts indicating excited states of Ne20. To confirm this phenomenon, alpha decay from excited states of Ne20 should be investigated non-coplaner alpha-alpha coincidences around recoil axis of excited Ne20 should be measured. Moreover, in experiment on C12 (a, 2a) Be' reaction, it was found that two alpha particles from this reaction are emitted in coincidence mainly in forward region.61 An explanation of this phenomenon was that this phenomenon was caused by final state interaction between two alpha particles. f this is true, same phenomenon should be observed when two alpha particle correlations were measured in plane vertical to that defined by beam direction recoil direction of Ne20. To do this experiment, we needed a scattering with which three dimensional correlation could be measured. n this report, design, construction of a three dimensional scattering some of nuclear physics experiment by use of this, are described.. DESGN AND CONSTRUCTON This scattering was expected to be mounted on axis of broad range magnetic spectrograph') in order to utilize beam analyzed through momentum analyzer magnet,'' so diameter of was limited by entrance of spectrograph. Moreover, vacuum system of this was same of that of spectrograph, so depth of was also limited. Under se conditions, outer dimensions of were designed as large as possible. To transport radiation detector to any position in three dimensional space, a longitudinal rotation was coupled with a latitudinal translation. Longitudinal rotation was executed by a rotation around vertical axis containing target center. Latitudinal translation was performed by an arc of sphere this arc-shaped arm was drived by a gear mechanism. Two sets of se arrangements were installed into so as to make particle-particle space correlation measurement feasible. Be- (155)

4 d i e V T. YANABU et al. A 41W H i Fig. 1. Schematic drawing of principle of three-dimensional freedom three sets ofmoving 11, Th: i =oio 4.,,,, _ : ~r i,,.. uy<..l.,'fig. ''"t, /.. 2. Photof scattering..,. Two moving arms are shown. arr/se arms are attached to,ao#'`'' -upper lid of. M (156)

5 N Three Dimensional Scattering Chamber side se arrangements, a horizontal rotating disc was equipped to mount a monitor counter to be capable of three body correlation experiment. A schematical drawing of se translation mechanism is shown in Fig. 1. Figure 2 shows photographic view of two rotating arms. se arms are attached to lid of. alignment of se arms a rotating disc depends on error of mechanical fabrication. 2 \ c' ^ no7q _: 1415,,... it..1 ' to F=. =1.1 im,..., , it 1 1 AN. -e, ,i!- Aim _Xi. E-:: 3 - ',.^^ " 'Vim n~~ Q l 0 D 1 9 E 21 (a 1) 26 el 4) Fig. 3. Cross section of scattering. parts of are : 1, viewing window. 2, 0-ring seal of upper lid. 3, ball bearings supporting upper lid. 4, gears attached to upper lid. 5, upper lid. 6, rollers defining motion of arm. 7, driving hle of arm 21. 8, ball bearings supporting central jig of arm 11. 9, driving hle of arm , driving hle to rotate central jig toger with arm , moving arm. 12, viewing window. 13, gear attached to arm , driving gear of gear 4. 15, driving hle of gear , collimator. 17, collimator support. 18, index of rotation angle of disc , ball bearings of disc , frictional wheel to rotate disc , moving arm. 22, driving hle to rotate target holder. 23, tapered axis to fix scattering to platform of reaction analyzer magnet. 24, gear attached to target holder. 25, target frame. 26, rotating disc. 27, ball bearings. 28, rollers defining motion of disc , insulator. 30, Faraday cup. (157)

r T. YANABU et al. Figure disc 3 shows is held dimensions by three segments of this. attached to bottom no rotating axis. This mechanism comes from holder in center of this. target tangular frame.

6 r T. YANABU et al. Figure disc 3 shows is held dimensions by three segments of this. attached to bottom no rotating axis. This mechanism comes from holder in center of this. target tangular frame. axis. to which Explanations port are three height of pieces of thin target of a beam metalic holder collimater, centering of need to leave holder could foil are is of rotating adjustable a Faraday cup has room for target mount a rec- fixed or a gas relative target to a beam beam monitering omitted. Airis 7.y^ Fig. 4. fite Photo of scattering reaction analyzer magnet. radiation detectors are disc by means of relevant se arms geared mechanism a frictional rack were wheel contact of magnetic through copes were set estimated scattering. 4F to mounted jigs so is used. to fix 4 shows rotation center dimensions. PERFORMANCE was to angle n assembling mentioned of constructed from in set errors center. beam spectra') as d+a>p+a+n. direction (158) was beginning a function of proton moved a around on out from, this center. To drive disc is done with is read this arms of of outside two 1966 has than 0.2, Figure 5 azimuthal counter teles- machining accuracy of angular measurement is less particle-particle correlation experiment. shows proton-alpha correlation experiment is on reaction respect Figure window. above to point at target Driving of rotating by measuring been used since n. sufficient to investigate at 45 with on disc. spectrograph. viewing as mounted on platform of beam angle. was set direc-

7 - Three Dimensional Scattering Chamber 1041 /. D(a,pa)n Eaa= 29.2 MeV Op= 45 6a=10 200A # E15020 Aerw' ~10018,1 b50~14~a Yp(deg.) 12 16\*'z Fig. 5. Three dimensional representation of energy spectra of alpha particles. See text. Figure from ref. 9) tion varying azimuthal angles. alpha particle counter was fixed at 10 with respect to beam. n this system, coincidence spectrum of alpha particles at op=0 gives co-planer coincidence events. f proton or neutron has no momentum inside deuteron, it should give no coincidences when 0-#-0 against experimental results. Figure 6 shows momentum distribution of neutrons in deuteron thus obtained : 8 p=45? 8a=10 : ep=30, 80=H uff n2 _ b1 =r i E i2(kev/2) Fig. 6. Momentum distribution of a neutron in a deuteron. See text. Figure from ref. 9). Figure 7 shows a result of or experiment.1) This figure shows azimuthal angular correlation distribution between alpha-particles tritons from (159)

8 T. YANABU et al. reaction Li' +a >Li7* (4.63 MeV) +a' +t nelastically nelastically scattered alpha particles (a' in equation) were detected at 60 with respect to beam direction decay product tritons from excited state of Li7 were detected by moving a counter with 30 or 90 fixed polar angle around recoil axis of excited Li'. n figure, it is seen that tritons are preferentially emitted in reaction plane defined by beam direction by alpha detector direction ; Ojw 0 or 180 in figure. From se figures, it is seen that non-coplaner correlation measurements give more precise abundant informations than correlation measurements in reaction plane. 1.5Li' E 10^ 463 MeV 60 lab lab. + Bac,, 90 eacm= Azimuthal angle (deg.) Fig. 7. Angular correlations between alpha particles tritons. See text. Figure from ref. 10). This three dimensional scattering is now fully utilized in laboratory to investigate final three body nuclear reaction can be used in final four body nuclear reaction. Molecular structure of nucleus can be clarified with this we hope to do a variety of experiments with this. ACKNOWLEDGMENT authors would like to acknowledge Prof. Y. Uemura, Dr. K. Fukunaga or members of Laboratory of Nuclear Science, nstitute for Chemical Research, for ir stimulating discussions in course of designing. REFERENCES (1) K. Kimura, Bull. nst. Chem. Res. Kyoto Univ., 43, 499 (1965). (2) T. Yanabu, S. Yamashita, K. Takimoto K. Ogino, J. Phys. Soc. Japan, 20, 425 (1960). K. Takimoto, Mem. Coll. Sci., Univ. Kyoto, Ser. A, Vol. 31, No. 2, Article 12 (1967). (160)

9 Three Dimensional Scattering Chamber T. Yanabu, S. Yamashita, K. Hosono, S. Matsuki, T. Tanabe, K. Takimoto, Y. Okuma, K. Ogino, S. Okumura R. shiwari, J. Phys. Soc. Japan, 24, 667 (1968). (3) T. Yanabu, to be published. (4) S. Yamashita et al, J. Phys. Soc. Japan. 26, 1078 (1969). (5) T. Yanabu et al, Contribution No. 8-33, nternational Conference on Nuclear Structure, Sept. 1967, Tokyo, Japan. (6) T. Yanabu et al, third paper of ref. 2) (7) Y. Uemura et al, this Bulletin, preceding paper. (8) T. Yanabu et al. this Bulletin, preceding paper. (9) T. Tanabe, J. Phys. Soc. Japan, 25, 21 (1968). (10) S. Matsuki, J. Phys. Soc. Japan, 24, 1203 (1968). (161 )

Title Broad Range Magnetic Spectrograph. Author(s) Matsuki, Seishi; Ogino, Kouya; Saka.

Title Broad Range Magnetic Spectrograph. Author(s) Matsuki, Seishi; Ogino, Kouya; Saka. Title A Gas Target System for Nuclear Sca Broad Range Magnetic Spectrograph Author(s) Matsuki, Seishi; Ogino, Kouya; Saka Citation Bulletin of the Institute for Chemi University (1985), 63(1): 40-46 Issue