372596158

129

RIKEN Accel. Próg. Rep. 24 (1990)

IV-2. Cross Section Data for ⁶⁸Ge Production

Y. Tendow, A. Hashizume, Y. Ohkubo, and K. Kitao

The nuclide ^GefTi^ = 270.8 d) decays to ⁶⁸Ga(T_V2 = 67.629 m) by electron capture, and ⁶⁸Ga decays by 89% positron emission and 11% electron capture and emits weak y-rays (3%). Thus, a ⁶⁸Ge-⁶⁸Ga system provides a useful generator of positron emitters which could be applied to medical diagnosis with positron Computer tomogragh for the localization of malignant human tumors. The short-lived positron emitter ⁶⁸Ga is separated from ^<,8Ge by milking at any time when a diagnosis is reąuired in hospitals having no cyclotron facilities.

Only a few cross sections measured for ⁶⁸Ge production are found in the literaturę. The reaction types, incident energy ranges, and maximum cross sections for the excitation functions measured up to the present are summarized in Table 1.

Table 1. Cross Sections for ⁶⁸Ge Production.

Reaction	Energy (MeV)	O max (mb at MeV)	Reference
^69Ga (p, 2n)	13-56	465 (at 20)	1)
^7lGa (p, 4n)	36-56	137 (at 43)	1)
^70Ge (p, p2n)	24-64	100 (at 37)	2)
^MZn (a. y)	9.4 - 15.6	0.771 (at 11.3)	3)
	10.5 - 16.5	0.9 (at 16.5)	4)
66Zn (a, 2n)	17-26	180 (at 26)	3)
	19-37	154 (at 31)	5)
5«Ni (160, 2pa)	50-70	204 (at 70)	6)
Y (p, spali)	593	6.75	7)
Rb (p, spali)	593	7.80	7)
Br (p, spali)	593	11.1	7)
As (p, spali)	593	10.7	7)
Rb+Br (p, spali)	800	19	8)

As for the proton-reaction cross section, Porile et al.^l) measured for ⁶⁹Ga(p, 2n), ⁷¹Ga(p, 4n) reac-tions and Horiguchi et al.^2> for ⁷⁰Ge(p, p2n) reaction (Fig. 1). The cross section for (p, xn) reaction, in contrast to the (p, pxn), fails rapidly from the maximum as the proton energy increases. There-fore, in order to obtain large thick target yields, the (p, pxn) reaction would be advanta-geous over the

Proton Energy (MeV)

Fig. 1. Excitation functions for Ga(p. xn) and Ge(p, pxn) reactions.

(p, xn) reaction when higher energy proton beams are available.

Nagarnę et al. ⁵⁾ measured corss sections for the ’Zn(a, 2n) reaction using natura! zinc targets. Ruddy et al³⁾ also measured cross sections for the same reaction in a lower energy part of excitation.

Griitter⁷⁾ measured spallation cross sections on As, Br, Rb, and Y targets at a proton energy of 593 MeV.

References

1)    N.T. Porile, S. Tanaka, H. Amano, M. Furukawa, S. Iwata, and M. Yagi: Nuci Phys., 43, 500 (1963).

2) T. Horiguchi, H. Kumahora, H. Inoue, and Y. Yoshizawa: Int. J. Appl. Radiał. Isot., 34, 1531 (1983).

3)    F.H. Ruddy and B.D. Pate: Nuci Phys., A127, 305 (1969).

4)    N.T. Porile: Phys. Rev., 115, 739 (1959).

5)    Y. Nagarnę, M. Unno, H. Nakahara, and Y. Murakami: Int. J. Appl. Radiat. Isot., 29, 615 (1978).

6) J.J. Simpson, P.O. Tj0m, and I. Espe, G.B. Hagemann, B. Herskind, and M. Neiman: Nuci Phys., A287, 362 (1977).

7)    A. Griitter: Int. J. Appl. Radiat. Isot., 33, 725 (1982).

8)    B.L. Cohen and E. Newman: Phys. Rev., 99, 718 (1955).