1. Physics Colloquium Ⅱ 2003.12.18 Shibata Laboratory 99-0508-5 OKA, Hiroki Nucleosyntheses studied with a Van de Graaff Accelerator [Contents] 1. Objective 2. Method 3. Germanium detector 4. Test beam time 5. Plans 6. Summary

2. 1. Objective I study nucleosynthesis like the one in stars. H, He, Li C, N, O to Fe Created in stars. To study nucleosynthesis with a Van de Graaff Accelerator and a germanium detector. ・ Nucleosyntheses Beyond Fe Z (atomic number) Ti V The composition ratio of elements to hydrogen Created in supernova explosion. Created soon after big-bang.

3. 2. Method p ＋ 48 Ti → 49 V * γ Bombard Titanium target with proton beam. The gamma rays are detected with the germanium detector. Vanadium is in excited state and emits gamma ray. γ p Van de Graaff Accelerator at Tokyo Tech

4. A semiconductor detector. Energy resolution is much better than that of NaI scintillator. ～１ｍ 3. Germanium detector Gamma rays make electron-hole pairs. The pairs converted to electric current. ・ Measurement of energy resolution Na22 (511 keV, 1274 keV) Red : Ge Black: NaI Energy resolution: R 、 Energy resolution at 1274 keV;

5. 4. Test beam time ・ Beam Time on November 6th, 2003 Proton Beam 1.5MeV Ti Target 5μm thick ・ 48Ti (p,γ) 49V Cross Section at Ep=1.5MeV Y : Number of γ-rays emitted from Vanadium I : Beam Current n : Density of the Target Nuclei x : Thickness of the Target To count the number of γ-rays emitted from Vanadium, energy calibration, detection efficiency, and the solid angle acceptance is needed. Gamma ray absorption in the target chamber wall is needed. Y σ ・ I ・ n ・ x (This was a preparation for the 3rd year students’ experiment as well.) The beam current was measured with Faraday cup.

6. Am241 (60 keV) Eu152 (122 keV etc.) ・ Measurement of Gamma ray absorption in the target chamber wall. γ chamber 50 100 500 absorption radiation source Target chamber is stainless steel. Some γ-rays are absorbed in the chamber wall. detector

7. 90.6152.9 1140.7 barn Obtained cross section There is an uncertainty originating from background, efficiency, absorption in target chamber wall and the beam current. I will evaluate these uncertainties. 0 90.6 152.9 748.3 1140.5 49V Level scheme

8. 5. Plans Jan. 20(Tue) ～ 23(Fri), 2004 ・ Next Beam Time ・ Veto the Compton continuum Anti-coincidence shielding Compton scattering γ plastic scintillator Germanium detector and plastic scintillator detect gamma ray in coincidence. Compton Scattering Compton continuum will be suppressed. Veto Ge detector

9. 6. Summary ・ The objective is to study nucleosyntheses with a Van de Graaff Accelerator and a germanium detector. ・ The germanium detector’s energy resolution and its efficiency were measured. ・ I had test beam time and observed nucleosyntheses. ・ I will have a 4-day beam time in January, 2004. Cross section was evaluated. Need to evaluate uncertainty. Try to suppress the Compton continuum. ・ Gamma ray absorption in target chamber was measured. Beam current was measured with Faraday cup.