Environmental Radiation Monitoring Experiment

1. Objective

To understand the principles and operational characteristics of various radiation detectors (GM counter, PIN diode detector, small scintillator+SiPM, 3-inch NaI(Tl) detector) by measuring their respective counts per minute (CPM) for background radiation. Furthermore, to learn and practice detector calibration using a Cesium-137 ($^{137}$Cs) test source.

2. Theoretical Background

Background radiation is ubiquitous, originating from cosmic rays, terrestrial radionuclides (e.g., Uranium, Thorium, Potassium-40), and artificial sources. This experiment introduces four radiation detector types, their principles, and calibration using $^{137}$Cs.

• Geiger-Müller (GM) Counter: Gas-filled tube; detects radiation with electrical pulses; no energy resolution.
• PIN Diode Detector: Semiconductor junction; detects alpha/beta/gamma; can provide partial energy info.
• Small Scintillator + SiPM: Compact; converts radiation to light then electric signal; basic spectroscopy.
• 3-inch NaI(Tl) Detector: High-resolution gamma detector; good for isotope ID using spectral peaks.
• Detector Calibration: Maps detector output (e.g., channel) to physical units (keV); uses 662 keV from $^{137}$Cs.

3. Materials & Equipment

• Portable GM counter
• PIN diode detector
• Small scintillator + SiPM
• 3-inch NaI(Tl) detector with MCA
• $^{137}$Cs source
• PC with MCA software
• Timer
• Measurement sheets
• Ruler

4. Procedure

1. Measure background radiation with all detectors (5 minutes). Record CPM.
2. Place $^{137}$Cs at a fixed distance. Acquire a spectrum using MCA for NaI(Tl) and SiPM.
3. Identify the 662 keV photopeak and perform energy calibration.
4. Measure CPM at multiple locations with all detectors. Note differences and their causes.

5. Data Analysis & Interpretation

Analyze and interpret the collected data.

• Compare the background CPM readings from each detector and explain the differences.
• Describe the process of energy calibration using the $^{137}$Cs source.
• Discuss which detector is best suited for different applications (quick detection, spectroscopy, low-level monitoring).

6. Conclusion & Notes

Summarize your findings on detector performance, CPM trends, and the importance of calibration for environmental radiation monitoring.

• Review the 'Class Preparation Materials' before starting the experiment.
• Always follow radiation safety protocols.