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Flashcards in Gamma Energy Deck (9)
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1
Q

What is mono-energetic γ-radiation?

A

γ-radiation, which has photons of equal E

2
Q

What is dual isotope labeling?

Why are 2 isotopes used?

A

investigation of a physiological process by 2 γ-emitting isotopes of different photon E

3
Q

What is a integral discriminator?

A

device that

  • lets through pulses of amplitude higher than a certain level, the discriminator level
  • blocks those of smaller amplitude
4
Q

What is a differential discriminator?

A

device that

  • lets through pulsed for which the amplitude is between 2 DD levels, the channel
  • blocks those of the amplitude outside the channel

⇒ used to make size distribution of pulses

5
Q

What is a photopeak?

On what does its width depend on?

A

γ-photon absorbed by photoeffect in the scintillator

→ light flash intensity dependent on photon E
→ amplitude of voltage pulse generated by PMT proportional to photon E

⇒ sorted by DD → histogram with photopeak

width depends on: type of detector

6
Q

What is a Compton range?

Why do we achieve a broad Compton range instead of a narrow line like in photopeaks?

A

similar to photopeak, but wider range with lower peaks generated by Compton scatter

→ wider spread amplitude range due to partial E transfer

7
Q

How can the position of the photopeak in the pulse rate vs. voltage graph be shifted?

A

increased anode voltage → increased dynode voltage → enlarged secondary-electron multiplying factor → pulses of higher amplitude → photopeak shifted to the right

8
Q

How can the height of the graph in the pulse rate vs. voltage graph be shifted?

A

increased activity (decay rate) → more γ-photons absorbed → more pulses → amplitude of graph increased

9
Q

What did we calculate in the gamma energy lab and how? Give the formula.

A

gamma energy of one isotope determined by using the ratio of the photopeaks and the gamma energy of the second isotope.

E1 = E2 * Uphoto 1/Uphoto 2