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