Investigation of the proton-induced reactions on natural molybdenum. M. S. Uddin, M. Hagiwara, F. Tarkanyi1, F. Ditroi1 and M.Baba Cyclotron and Radioisotope Center, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan. IInstitute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, H-4001, Hungary. Introduction

(Collaboration work between Tohoku University and Debrecen,Hungary) CONTENTS Introduction Experimental Data analysis Results and discussion Conclusion (Collaboration work between Tohoku University and Debrecen,Hungary)

1. Introduction 1.1 a) Activation of structural element b) Importance of p-induced activation on molybdenum: 1. Thin layer activation, 2 a. Medical radioisotopes i) 99mTc/99Mo, ii) 96Tc. b. Reactions of 99Mo production i) (n,) and (n, fission) ii) 100Mo(p,pn)99Mo. c) Radioactive wastes.

1.2 Data status 1.3 Aim of the present work Excitation functions Thick target integral yield 22-70 MeV AVF Cyclotron, Tohoku University.

2. Experimental 2.1 Layout of Cyclotron and Radioisotope Center (CYRIC) Tohoku University

2.2 Experimental specifications Stacked-target technique Proton source : AVF Cyclotron, CYRIC, Tohoku University Proton energy : 70 MeV Beam diameter: 0.8 cm Beam current : ~25 nA Irradiation time : 1 hr and 17 min 0.8 cm diam. Al Cu Mo Proton Beam 70 MeV, ~25 nA Monitor foil Sample foil

2.3 Experimental set-up HPGe-Gamma Detector HV+4000V Amp Al Cu Mo Proton Beam Monitor foil Sample foil HPGe-Gamma Detector Radioactive material Ge detector HV+4000V Gamma-ray Amp 99mTc (140 keV)

2.4 Proton energy degradation Al Cu Mo Proton Beam Simulation with SRIM Monitor foil Sample foil Al Cu Energy Dispersion

Data analysis 3. Data Analysis 3.1 Formulae Reaction rate ……………(1)    3.1 Formulae Reaction rate ……………(1) Cross-section  = RNQ/(INdt) …………….(2) Thick target integral yield …………….(3) Where C = total counts of gamma ray peak area  = decay constant (s-1) , ENSDF  = efficiency, experimentally determined and coincidence- summing effect corrected.  = branching ratio of gamma rays, ENSDF N= number of atoms in the target Q= beam current (coulomb) ti = irradiation time tc= cooling time tm= counting time Nd= density, atom/cm3 I = beam flux , p/cm2/sec t = thickness, cm N= number of atom dE/dt= stopping power 3. Data Analysis Data analysis

3.2 Monitor reactions Cu-monitor Al-monitor 3. natCu(p,x)56Co ( E=846.812 keV) 4. natCu(p,x)65Zn (E=1115.518 keV) 5.natCu(p,x)62Zn (E=596.70 keV) 27Al(p,x)22Na (E= 1274.53 keV) 27Al(p,x)24Na (E=1368.598 keV) 62Zn 65Zn 56Co

3.3 Gamma lines separation 99Mo 99mTc 140 keV 99Mo(A1, 1)99mTc (A2, 2) 1. (direct) 99mTc (A3, 3) 90Nb (A4, 4) t=decay time 2. 2= 3

Theoretical calculations 4. Results and discussion 4.1 Excitation functions Other experiments { Comparison with Theoretical calculations 100Mo(p,x)99Mo natMo(p,x)93mMo natMo(p,x)96Tc natMo(p,x)95,95mTc

Excitation functions natMo(p,x)94Tc natMo(p,x)95Tc natMo(p,x)95mTc

Excitation functions natMo(p,x)95Nb natMo(p,x)90Nb natMo(p,x)92m,96Nb

Excitation functions natMo(p,x)86,88,89Zr natMo(p,x)86,87,88Y

4.2 Thick target integral yields

5. Conclusion 5.1. Method: The excitation functions of the proton-induced reactions on Mo were obtained by employing a stacked target technique in the energy range 22-70 MeV. We established a complete method to obtain reliable data of proton-induced reactions. 5.2. Results: Obtained new data for all of the investigated radinuclides. For 86Zr, 86,87,88Y radionuclides, the single curves of theoretical calculations do not fit our results because i) the decay goes through a parent isotope and ii) the model calculations are not reliable. In most of the cases, the thick target integral yields are linearly rising with the increase of bombarding proton energy. Yields of the radiocontaminants become large due to opening of several new reaction channels on natural Mo.

5.3. Monitor: Good agreement of the measured excitation functions of the monitor reactions to each other. For 24Na and 62Zn radionuclides, the measured cross-sections are completely supporting recommendation data. Measured cross-sections of 22Na production showed more consistent with recommendation in higher energy region than lower energy. Its production cross-sections became lower systematically than the recommended values with the decrease of proton energy. Our measured values for 22Na will play important role to give proper recommended data.