1. A Study of Time over Threshold (TOT) Technique for Plastic Scintillator Counter 高能物理研究所 吴金杰

2. Outline Introduction Research method-wave analysis Signal characteristics Relative charge resolution by TOT Summary

3. 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

4. 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

5. Research method-wave analysis To be measure TOT, Amplitude, Charge How? Chip? Based on CAMAC system? Wave analysis Using high quality oscilloscope sample rate 20 GS/s TOF module Scintillator EJ200 +R5924 Experimental setup

6. 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

7. Amplitude, Charge Spectrum of amplitude Spectrum of charge Charge versus amplitude The charge is obtained from the time integral of the current pulse

8. 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

9. 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 The relative error of Q by TOT can be obtained by formula

10. 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

11. 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)

12. Thanks