CHP Radiation Measurement and Instrumentation 3

Question 1

The W-value for air (approximately 34 eV/ion pair) is used to convert:

Accepted Answer

Energy deposited to number of ion pairs created

Answer

The W-value (mean energy per ion pair) converts total energy deposited in a gas into the number of ion pairs produced, which is proportional to the measured charge.

Question 2

A Fano factor less than 1 in semiconductor detectors indicates:

Accepted Answer

Statistical fluctuations are sub-Poissonian, giving better resolution than expected

Answer

A Fano factor F < 1 means the variance in ion-pair creation is smaller than Poisson statistics predict, which is why HPGe resolution exceeds the Poisson limit.

Question 3

Compton suppression in a gamma-ray spectrometer system is achieved by:

Accepted Answer

Surrounding the primary detector with an annulus detector in anticoincidence

Answer

An anticoincidence annulus detector vetoes events where a Compton-scattered photon escapes the primary detector, reducing the Compton continuum.

Question 4

The quench gas in a Geiger-Müller tube serves to:

Accepted Answer

Absorb UV photons and positive ions to terminate the discharge

Answer

The quench gas (e.g., halogen or organic vapor) absorbs UV photons and neutralizes positive ions, preventing spurious secondary discharges.

Question 5

An OSLD (optically stimulated luminescence dosimeter) differs from a TLD primarily in that readout is performed by:

Accepted Answer

Exposing the crystal to a specific wavelength of light

Answer

OSLDs are read by stimulating the crystal with laser light of a specific wavelength rather than by thermal heating as in TLDs.

(CHP) Certified Health Physicist Practice Test

(CHP) Certified Health Physicist Practice Test

CHP Radiation Measurement and Instrumentation 3