Transcript A Study of Time over Threshold (TOT)

A Study of Time over Threshold (TOT) Technique
for Plastic Scintillator Counter
高能物理研究所
吴金杰
Outline
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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
TOT versus measured time
 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
Research method-wave analysis
To be measure TOT, Amplitude, Charge
How?
Sintillator 1
PMT2
Chip?
PMT
R5924
PMT1
PMT
R5924
Scintillator EJ200
Scintillator
PMT3
Based on CAMAC system?
Wave analysis
Using high quality oscilloscope
sample rate 20 GS/s
TOF module
Scintillator EJ200 +R5924
Signal from
the scintillator bar
Oscilloscope
Delay cable
CH1
CH2
Trigger
PMT1
PMT2
PMT3
Discriminator
Experimental setup
Logic unit
1∩2∩3
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
A wave shape of pulse
Rise time:4.2ns
Reference to the design
BESIII TOF electronics
The noise spectrum
Spectrum of rise time
Amplitude, Charge
The charge is obtained from
the time integral of the
current pulse
50 ps 
Q
i  2000
V
i 0
i
50
Spectrum of amplitude
Spectrum of charge
Charge versus amplitude
Distribution of TOT
The distribution of TOT with different threshold
The distribution of TOT when the
threshold is set to 65 mV
The distribution of TOT when the
threshold is set to 195 mV
15% of the most probable value of
amplitude
45% of the most probable value of
amplitude
TOT VS Charge--threshold 65mV
Linear correlation between TOT
and charge
Relative charge resolution can
reach 7%-18% when the threshold
is set to 65mV
TOT versus charge
The relative error of Q by TOT
can be obtained by formula
Q
Q

QTOT  Qactual
Qactual
The relative charge resolution versus charge
TOT VS Charge--threshold 195mV
The correlation between TOT and charge
TOT  A  B / Q
TOT versus charge
Relative charge resolution can
reach 4%-7% when the threshold is
set to 195mV
The relative charge resolution versus charge
Summary
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A Study of TOT technique for Scintillator counter
firstly
Wave analysis
The Characteristics of TOF module
Pedestal, Noise, Amplitude, Charge, Rise time
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Relative charge resolution
From 7% to 18% (Threshold is set to 65mv)
From 4% to 7% (Threshold is set to 195mv)
Thanks