General Detector Properties

Question 1

Dead Time

Answer 1

Minimum amount of time needed between two events to detect them

Question 2

Non-paralyzable model

Answer 2

A fixed dead time is assumed to follow each event and true events occurring during the dead time are lost

True interaction rate = (Recorded count rate) / (1 - recorded count rate * dead time)

Question 3

Paralyzable Model

Answer 3

Dead times are not fixed and the dead period is extended by the dead time by each true event that occurs during the dead period

Recorded Count Rate = (True Interaction Rate)*EXP(-True Interaction Rate * Dead Time)

Question 4

Two Source Method to determine Dead Time

Answer 4

Find background rate
Gross count rate with source 1
Gross count rate with source 2
Gross count rate with both sources

Use either paralyzable or non paralyzable model to calculate dead time

Question 5

Absolute Detection Efficiency

Answer 5

(# pulses recorded) / (# of particles emitted by source)

Question 6

Intrinsic Detection Efficiency

Answer 6

(# of pulses recorded) / (# of particles incident on detector)

Question 7

Total Efficiency

Answer 7

All pulses are accepted

Question 8

Peak Efficiency

Answer 8

Only interactions that deposit full energy of incident radiation are accepted

Question 9

Energy Resolution

Answer 9

Fluctuation from pulse to pulse in terms of recorded energy

Resolution = 100% * (FWHM) / (Pulse Height)

Question 10

Pulse Mode

Answer 10

Instrument records each individual particle that interacts with the detector so a pulse above a threshold registers one count regardless of energy deposition

Question 11

Current Mode / Mean Square Voltage Mode

Answer 11

The time average of many individual events is measured which is preferable for high event rates