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# Lifetime measurement - PowerPoint PPT Presentation

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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Presentation Transcript

Osaka University – 2009

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

g1 = 122 keV

g2 = 14.4 keV

• Impossible to predict the lifetime of an nucleus, but mean lifetime can be determined
• Lifetime of unstable nucleus follows the decay law:
• Using TAC (Time to Amplitude Converter)

g1

DET 1

DET 2

g2

Procedure (1)
• Setup:

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

DET B

NEG.

AMP

SCA

DISCR.

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)
• Time to channel calibration:
• Delay unit: 0 ÷ 500 ns

NEG.

AMP

SCA

DISCR.

DET

Start

Stop

TAC

MCA

Delay

DISCR.

Procedure (4)
• Adjust delay time of SCA:

NEG.

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

SCA

DISCR.

Procedure (5)
• Time spectrum measurement:

NEG.

AMP

SCA

DISCR.

DET A

Start

Stop

TAC

MCA

NEG.

AMP

SCA

DISCR.

DET B

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