1. LIFETIME MEASUREMENT Advanced experiment group: Le Cong Hao Tran Hoai Nam Tran Duy Tap Tran Thien Thanh Dang Ngoc Thang Guo Wei Hu Jun Zhao Pengwei The primer course of experimental particle and nuclear physics Osaka University – 2009

2. Outline  Introduction  Principle of lifetime measurement  Procedure  Results 2

3. Introduction  Lifetime is an important parameter in nuclear structure.  1 st excited state of 57 Fe:  1 = 122 keV  2 = 14.4 keV 3

4. Principle of lifetime measurement (1)  Impossible to predict the lifetime of an nucleus, but mean lifetime can be determined  Lifetime of unstable nucleus follows the decay law: 4

5. Principle of lifetime measurement (2)  Using TAC (Time to Amplitude Converter) 11 22 DET 1 DET 2 5

6. Procedure (1)  Setup: NEG. DISCR.AMPSCA DET A AMPSCADISCR. TACMCA Start Stop NEG. DET B 6

7. Procedure (2)  Select two gamma rays: same method as experiment 1 coinc. AMPDELAY SCA (NORM) MCA DET BiPolsignal POS. Det A: HV = -900V Gain: coarse 40, fine 3.5 Window: - upper level = 9V - lower level = 7V Det B: HV = +1000V Gain: coarse 40, fine 6 Window: - upper level = 1.4V - lower level = 0.8V 7

8. Procedure (3)  Time to channel calibration:  Delay unit: 0 ÷ 500 ns DET AMPSCA DelayDISCR. TACMCA NEG. Start Stop 8

9. Procedure (4)  Adjust delay time of SCA: DET A AMPSCA DISCR. TACMCA NEG. Start Stop SCA NEG. 9

10. Procedure (5)  Time spectrum measurement: NEG. DISCR.AMPSCA DET A AMPSCADISCR. TACMCA Start Stop NEG. DET B 10

11. Result (1)  Time spectrum: 11

12. Result (2)  Calculating:  Estimate background N BG  Subtract BG:  Convert to logarithmic scale  Linear fit using least square method  Estimate error 12

13. Result (3) 13

14. Result (4)  Another method to calculate:

15. Result (5)  Half life time:  Measured value: 1 st method: 2 nd method:  Reference value:  Other groups’ results: 15

16. Summary  In this experiment, we have measured the lifetime of 1 st excited state of 57 Fe by using TAC.  Lifetime can be measured by other methods: delayed coincidence, … 16

17. Summary  In this experiment, we have measured the lifetime of 1 st excited state of 57 Fe by using TAC.  Lifetime can be measured by other methods: delayed coincidence … 17

18. Acknowledgement  Osaka University  JICA  Professors and TAs  My partner and coincidence group 18

19. Thanks for your attention! 19