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Lifetime measurement

The primer course of experimental particle and nuclear physics Osaka University – 2009. 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. Outline. Introduction

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Lifetime measurement

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  1. The primer course of experimental particle and nuclear physics Osaka University – 2009 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

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

  3. Introduction • Lifetime is an important parameter in nuclear structure. • 1st excited state of 57Fe: g1 = 122 keV g2 = 14.4 keV

  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:

  5. Principle of lifetime measurement (2) • Using TAC (Time to Amplitude Converter) g1 DET 1 DET 2 g2

  6. Procedure (1) • Setup: AMP SCA DISCR. DET A Start Stop TAC MCA NEG. DET B NEG. AMP SCA DISCR.

  7. Procedure (2) • Select two gamma rays: same method as experiment 1 BiPol signal AMP DELAY MCA DET coinc. POS. SCA (NORM) • 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

  8. Procedure (3) • Time to channel calibration: • Delay unit: 0 ÷ 500 ns NEG. AMP SCA DISCR. DET Start Stop TAC MCA Delay DISCR.

  9. Procedure (4) • Adjust delay time of SCA: NEG. AMP SCA DISCR. DET A Start Stop TAC MCA NEG. SCA DISCR.

  10. Procedure (5) • Time spectrum measurement: NEG. AMP SCA DISCR. DET A Start Stop TAC MCA NEG. AMP SCA DISCR. DET B

  11. Result (1) • Time spectrum:

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

  13. Result (3)

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

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

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

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

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

  19. Thanks for your attention!

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