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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

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
Outline
  • Introduction
  • Principle of lifetime measurement
  • Procedure
  • Results
introduction
Introduction
  • Lifetime is an important parameter in nuclear structure.
  • 1st excited state of 57Fe:

g1 = 122 keV

g2 = 14.4 keV

principle of lifetime measurement 1
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:
principle of lifetime measurement 2
Principle of lifetime measurement (2)
  • Using TAC (Time to Amplitude Converter)

g1

DET 1

DET 2

g2

procedure 1
Procedure (1)
  • Setup:

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

DET B

NEG.

AMP

SCA

DISCR.

procedure 2
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
procedure 3
Procedure (3)
  • Time to channel calibration:
  • Delay unit: 0 ÷ 500 ns

NEG.

AMP

SCA

DISCR.

DET

Start

Stop

TAC

MCA

Delay

DISCR.

procedure 4
Procedure (4)
  • Adjust delay time of SCA:

NEG.

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

SCA

DISCR.

procedure 5
Procedure (5)
  • Time spectrum measurement:

NEG.

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

AMP

SCA

DISCR.

DET B

result 1
Result (1)
  • Time spectrum:
result 2
Result (2)
  • Calculating:
    • Estimate background NBG
    • Subtract BG:
    • Convert to logarithmic scale
    • Linear fit using least square method
    • Estimate error
result 4
Result (4)
  • Another method to calculate:
result 5
Result (5)
  • Half life time:
    • Measured value:
      • 1st method:
      • 2nd method:
    • Reference value:
    • Other groups’ results:
summary
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, …
summary1
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 …
acknowledgement
Acknowledgement
  • Osaka University
  • JICA
  • Professors and TAs
  • My partner and coincidence group