Measuring nuclear disintegration rates: Which instrument directly counts ionizing events from radioactive emissions?

Introduction / Context:
Monitoring radioactivity requires instruments that detect and count ionizing events due to alpha, beta, or gamma radiation. The goal is to measure disintegration rate (activity) or count rate for safety, research, and calibration purposes.

Given Data / Assumptions:

• The device must provide event counts proportional to ionization events.
• Typical on-site survey and laboratory counting contexts are considered.

Concept / Approach:
A Geiger–Müller (G–M) counter uses a gas-filled tube biased at high voltage. Ionizing radiation creates electron–ion pairs; Townsend avalanches cause detectable pulses. The instrument counts pulses per unit time, which reflects the rate of nuclear disintegrations reaching the detector (after geometry and efficiency corrections). By contrast, a cyclotron accelerates particles; a cold chamber is not a standard radiation counter; a mass spectrograph separates ions by mass-to-charge and is used for isotopic analysis rather than real-time counting of decay events.

Step-by-Step Solution:

Verification / Alternative check:
Other counters (proportional counters, scintillation detectors) also measure activity, but the most common general-purpose rate meter is the G–M counter.

Why Other Options Are Wrong:

• Cyclotron: Produces beams; not a rate counter.
• Cold chamber: Not a standard radiation measurement device for count rates.
• Mass spectrograph: Identifies isotopes; does not directly count disintegrations in real time.

Common Pitfalls:
Assuming any radiation-related instrument measures activity; function and operating principle must match the need for counting ionizing events.

Final Answer:
Geiger–Müller counter