Unit 3 - Radiation electronics and detection Part 1

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What is the conventional unit of measuring exposure to x-rays?

Radiation

Electron

Ionization

Roentgen (correct)

What is the best way to count the x-ray photons incident across an area?

Measuring the electric charge generated within the air

Attracting the electrons to a positive anode

Measuring the intensity of the x-ray beam

Extrapolating their number from the ionizations they are causing within air molecules (correct)

What is generated within the air when x-ray photons interact with it?

An electric charge (correct)

A small electrical current

Ionization

Radiation

What is the limitation of the Roentgen unit?

It is not a good indicator of the biological impact of radiation exposure Signup and view all the answers

What is the common component of all radiation detectors?

A transducer (radiation sensitive region) Signup and view all the answers

What happens to the electrons freed by ionization in a detection device?

They are attracted to the positive anode of a detection device Signup and view all the answers

What is the primary function of a portable survey instrument in environmental radiation?

To detect radiation contamination on work surfaces Signup and view all the answers

What happens when valence electrons return to their normal position in scintillation?

They scintillate Signup and view all the answers

What is required for a material to scintillate?

A particular crystalline structure Signup and view all the answers

What determines the amount of light emitted in scintillation?

The amount of energy absorbed by the material Signup and view all the answers

What type of detector converts x-rays to light?

Scintillation detector Signup and view all the answers

What is the purpose of a photocathode in a scintillation detector?

To convert light to electrons Signup and view all the answers

What is the basis of radiation detection instruments?

The ionization of atoms Signup and view all the answers

What determines whether ionization or excitation is favored in a radiation detector?

The physical state and density of the transducer Signup and view all the answers

What is the purpose of the electronic component in a radiation detector?

To convert the radiation effect in the transducer into a useful electronic signal Signup and view all the answers

What is the main difference between instruments designed for detection and those designed for measurement?

The mode of operation Signup and view all the answers

What is the main advantage of using the integrate mode in radiation detection?

It provides a precise measurement of radiation exposure over a set period of time Signup and view all the answers

What is the unit of measurement for radiation exposure in the integrate mode?

Millisieverts (mSv) Signup and view all the answers

What is the main factor that affects the accuracy of radiation detection devices?

The actual printed scale behind the needle of a meter Signup and view all the answers

How can the sensitivity of a radiation detection instrument be improved?

By increasing the electronic amplification of the incoming signal Signup and view all the answers

What is the definition of sensitivity in radiation detection?

The ability to detect small amounts of radiation Signup and view all the answers

What is the purpose of a photomultiplier tube in radiation detection?

To increase the sensitivity of the instrument Signup and view all the answers

What can cause the read-out of a radiation detection device to be higher than the real exposure?

Electronic noise Signup and view all the answers

Why do integrate mode detectors have less chance of missing photons?

They are less susceptible to dead times Signup and view all the answers

What is the problem with using a Geiger counter on a diagnostic x-ray machine?

It overloads the circuits of the counter Signup and view all the answers

What happens if the range of a detection instrument is set too high for the intensities of radiation expected?

Low intensities will not be picked up and adequately displayed on the read-out Signup and view all the answers

What is required for a transducer to have a high quantum detection efficiency?

Sufficient stopping power and optimal positioning Signup and view all the answers

What is the effect of increasing the density of a transducer on its absolute detection efficiency?

It increases Signup and view all the answers

What is the definition of absolute efficiency of a radiation detector?

The ratio of the number of radiation events detected to the number of photons emitted Signup and view all the answers

What is the reason for the low absolute efficiency of gas-filled detectors?

They are based on ionization of gas Signup and view all the answers

What is the result of increasing the resolving time of a radiation detector?

It decreases the accuracy of the instrument Signup and view all the answers

What is the condition necessary for a radiation detection device to produce a valid and accurate reading?

The sensitivity of the device must be matched to the expected intensity levels and type of radiation Signup and view all the answers

What occurs when radiation passes through gas in a detector?

Ion pairs are created Signup and view all the answers

What is the purpose of the anode in a gas filled detector?

To attract and detect electrons freed from the gas Signup and view all the answers

What is the characteristic of ionization chambers that makes them suitable for radiation surveys?

Portability Signup and view all the answers

What is the 'cascade' effect in proportional counters?

The electron ejected from the first event has energy to knock other electrons out Signup and view all the answers

What is the main difference between proportional counters and Geiger-Mueller tubes?

Cascade effect vs saturation process Signup and view all the answers

What is the purpose of quenching agents in Geiger-Mueller tubes?

To restore the gas molecules to their original state Signup and view all the answers

What is the characteristic of Geiger-Mueller tubes that makes them suitable for detecting small amounts of radiation?

High sensitivity Signup and view all the answers

What is the disadvantage of Geiger-Mueller tubes?

Dead time Signup and view all the answers

What is the result of the saturation process in Geiger-Mueller tubes?

The ionization of all gas molecules in the chamber Signup and view all the answers

What is the advantage of ionization chambers over proportional counters?

Higher accuracy Signup and view all the answers

Unit 3 - Radiation electronics and detection Part 1 - Med rad 2

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