PARTICLE DETECTORS (V): ELECTRONICS

Transcription

1 Monday, April 13, PARTICLE DETECTORS (V): ELECTRONICS Zhenyu Ye April 13, 2015

2 Monday, April 13, References Techniques for Nuclear and Particle Physics Experiments by Leo, Chapter Particle Data Group Review:

3 Monday, April 13, Contents Introduction Pulse Height Selection Coincidence Determination Triggers

4 Monday, April 13, Introduction NIM Electronics NIM Standard Co-axial cable and termination Discriminator Coincidence unit Logic unit Gate and delay generator Analog-to-Digital Converter Digital-to-Analog Converter Time-to-Digital Converter Single- and Multi-Channel Analyzer Multiple solutions for one application. Imaginations!

5 Monday, April 13, A Simple Counting System Preamp+Amplifier: amplify and shape the analog signal of the detector Discriminator: deliver a standard logic signal for every analog signal with an amplitude higher than the threshold; - serve a dual purpose: exclude low level electronic noise, shape the accepted signals to a form acceptable to the scaler Scaler: counts each arriving logic signal

6 Monday, April 13, Gate and Delay Generator (GDG) Gate and Delay Generators are triggerable devices which generate variable width gate pulses ranging from a few nanoseconds to a few seconds. Gate generators can be triggered by an input logic signal, or manually via a front panel button. The gate pulse then may be used to activate a certain device, e.g., a scaler. These modules are also equipped with an end marker signal which is a logic pulse issued at the end of the gate pulse.

7 Monday, April 13, Signal Height Selection In many experiments, the reaction of interest or products of the reaction are of a fixed energy or limited to a small range of energies.

8 Monday, April 13, Signal Height Selection Single-Channel Analyzer has adjustable upper (ULD) and lower (LLD) thresholds which defines an acceptable window. Pulses with amplitudes falling into this window are converted to logic signals while everything else rejected.

9 Monday, April 13, Calibration of SCA with Sources Pulse height = a + b * channel; Pulse height = a + b * channel + c * channel 2

10 Monday, April 13, Pulse Height Spectroscopy with MCA

11 Monday, April 13, Coincidence Technology

12 Monday, April 13, Coincidence Technology

13 Monday, April 13, Coincidence Technology

14 Monday, April 13, Coincidence Technology

15 Monday, April 13, Coincidence Curve Ideal coincidence curve is rectangular. Timing variations from detectors and electronics cause a jitter in the timing relation between the two signals which smear out the ideal rectangular coincidence curve. σ=resolving Time If the width of the signal is too smaller than fluctuations, true coincidences will be lost. In such cases, the widths should be enlarged.

16 Monday, April 13, Timing Measurements

17 Monday, April 13,

18 Monday, April 13, Accidental Coincidences Uncorrelated background events which happen to arrive within the resolving time of the circuit. The accidental coincidence rate ~ σn 1 N 2 The accidental coincidence rate corresponds to the baseline of the coincidence curve.

19 Monday, April 13, Combining Pulse Height Selection and Coincidence

20 Monday, April 13, Combining Pulse Height Selection and Coincidence

21 Monday, April 13, Triggers Inhibit or Busy Signal

22 Monday, April 13, Triggers Rutherford Scattering Rutherford Scattering Experiment

23 Monday, April 13, Triggers Rutherford Scattering Rutherford Scattering Experiment

24 Monday, April 13, Triggers Two Body Scattering Two-body Scattering Experiment

25 Monday, April 13, Triggers Two Body Scattering Two-body Scattering Experiment

26 Monday, April 13, Triggers Muon Lifetime

27 Monday, April 13, Triggers Muon Lifetime