a study of time over threshold (tot) technique for plastic scintillator counter
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A Study of Time over Threshold (TOT) Technique
for Plastic Scintillator Counter
高能物理研究所 吴金杰
Outline
Introduction Research method-wave analysis Signal characteristics Relative charge resolution by TOT Summary
Introduction to TOT (1)
TOT- Time Over Threshold
Pulse width
TOT is somewhat dependent the charge
Different threshold
Advantage:
One of alternatives to charge measurement
Simplify the electronics
Reduce the cost
Time over threshold
Introduction to TOT (2)
Apply in gas detectors Multi-gap Resistive Plate Chamber of
ALICE and STAR:
NINO-Correction of front edge time walk
Drift Chamber of CLEO-III: Relative charge resolution: 10%
TOT for Plastic scintillator counter?The correlation between TOT and Charge?
Relative charge resolution?Relative Charge resolution of CLEO
TOT versus measured time
Research method-wave analysis
Scintillator
PMT1
PMT3
Scintillator EJ200
PMT2
Sintillator 1
PMT R5924
PMT R5924
Signal from the scintillator bar
Delay cable
Oscilloscope
PMT1PMT2PMT3
DiscriminatorLogic unit 1 ∩ 2 ∩ 3
Trigger
CH1
CH2
To be measure TOT, Amplitude, Charge
How?
Chip?
Based on CAMAC system?
Wave analysisUsing high quality oscilloscope
sample rate 20 GS/s
TOF module
Scintillator EJ200 +R5924 Experimental setup
Pedestal, Noise, Rise time
The data within the first 250 ns are noise without any particle passing through the scintillator counter
Noise: 2.0 mV
Pedestal: 2.2 mV
Rise time:4.2ns A wave shape of pulse
The noise spectrum Spectrum of rise time
Reference to the design BESIII TOF electronics
Amplitude, Charge
Spectrum of amplitude
Spectrum of charge
Charge versus amplitude
2000
0
50
50
i
ii
ps VQ
The charge is obtained from the time integral of the current pulse
Distribution of TOT
The distribution of TOT when the threshold is set to 65 mV
15% of the most probable value of amplitude
The distribution of TOT when the threshold is set to 195 mV
45% of the most probable value of amplitude
The distribution of TOT with different threshold
TOT VS Charge--threshold 65mV
The relative charge resolution versus charge
TOT versus charge
Linear correlation between TOT and charge
Relative charge resolution can reach 7%-18% when the threshold is set to 65mV
Q TOT actual
actual
Q Q
Q Q
The relative error of Q by TOT can be obtained by formula
TOT VS Charge--threshold 195mV
The relative charge resolution versus charge
TOT versus charge
The correlation between TOT and charge
Relative charge resolution can reach 4%-7% when the threshold is set to 195mV
/TOT A B Q
Summary
A Study of TOT technique for Scintillator counter firstly
Wave analysis The Characteristics of TOF module
Pedestal, Noise, Amplitude, Charge, Rise time
Relative charge resolution From 7% to 18% (Threshold is set to 65mv)
From 4% to 7% (Threshold is set to 195mv)
Thanks
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