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Positron Lifetime Measurement System

Positron lifetime measurement is used for the measurement of vacancy-type defect of semiconductor in materials field. This is an all-in-one positron lifetime measurement system with measurement device and power supply. In the lifetime measurement, the life time is calculated by using 3GSPS, which is imported by high-speed pulse signal from two BaF2 scintillators. In the Coincidence Doppler Broadening(CDB), the 2D histogram is made by wave height value of coincidence from two Ge semiconductor detectors. Additionally, these devices can be combine to be measured by AMOC, which is the correlation of lifetime and momentum.

 

1. Appearance
(1) Spectral Meter Module for Time Analysis

It is a spectrum analyzer for time analysis which adopted high speed 3 GHz ADC for each CH.
BaF2 Enter the signal from the scintillation detector.
Time difference analysis DSP function built in.

(2) DSP multi-channel analyzer module

It is a multi-channel analyzer equipped with digital signal processing (DSP) function for gamma ray spectroscopy.

Ge input directly the preamplifier output signal from the semiconductor detector.
Sampling 100 MSPS, ADC gain maximum is 8192.

(3) Preamplifier power supply module

Preamplifier power supply for Ge semiconductor detector.

Supply } 24 V (50 mA) and } 12 V (50 mA) from the D-sub 9 pin connector.
The pin arrangement of the connector is NIM compliant.

(4) High voltage power supply module

It is a high voltage power supply for two BaF 2 scintillation detectors and two Ge semiconductor detectors.

CH1 and CH2 are for Ge semiconductor detectors and are rated up to + 5000V (or -5000V).
CH3 and CH4 are for BaF2 scintillation detector It is maximum rated -4000V.
Both use SHV connectors.

(5) VME power supply rack

It is VME standard 7-slot power supply rack.

AC 100 V, maximum 300 W.
Supplies power to each module.

* In addition to the above, the following items are required.

· BaF2 scintillation detector
· Ge semiconductor detector
· PC (for application execution)
· Switching hub (PC and each module for LAN cable connection)
 
2. Measurement mode (There are 5 measurement modes)

(1) Lifetime mode


Lifetime (LT) mode is a mode in which two BaF 2 scintillation detectors are measured at the same time, the time difference between the rise of the two waveforms is taken, and positron lifetime measurement is performed.

Lifetime mode configuration diagram

Lifetime mode screen

(2) Wave mode


The wave mode measures the waveform from two BaF 2 scintillation detectors.

Wave mode configuration diagram

Wave mode screen

(3) Energy mode


The energy mode is a mode for measuring the energy spectrum from two Ge semiconductor detectors.

Energy mode configuration diagram

Energy mode screen

(4) CDB mode

CDB (Coincidence Doppler Broadening) mode is a mode that takes coincidence counts of two Ge semiconductor detectors, takes each crest value, measures positron annihilation coincidence counting Doppler broadening.

CDB mode configuration diagram

CDB mode screen

(5) AMOC mode

AMOC mode is a mode to measure positron lifetime-momentum correlation by taking coincidence counts of two BaF 2 scintillation detectors and one Ge semiconductor detector.

AMOC mode configuration diagram

AMOC mode screen
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Last Update: 18 July 2017
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