Measurement and instrumentation Flashcards

1
Q

What is the operational voltage for a Gieger-Muller counter?

A

900-1000 volts

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2
Q

What is the scintillation process?

A

The absorption of energy by a substance and its re-emission as visible or near visible light. (photoluminescence, thermoluminescence, phosphorescence)

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3
Q

Equation for resolving time correction

A
N= n/(1-nt)
N=true count rate 
n=observed count rate
t= resolved time
ex: t=200 sec; n= 6x10^4 cpm; N=7.5x10^4 cpm
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4
Q

What is dead time?

A

The interval of time for GM tubes where no pulse can be formed.

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5
Q

What is resolving time?

A

The interval of time which is required between two successive signals, so that both may be analyzed

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6
Q

Equation for resolving time correction

A
N= n/(1-nt)
N=true count rate 
n=observed count rate
t= resolved time
ex: t=200 sec; n= 6x10^4 cpm; N=7.5x10^4 cpm
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7
Q

What is Recovery Time?

A

the period from the time a pulse can be formed (end of dead time) until the time the pulse size is large enough to be passed by the discriminator and be counted.

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8
Q

Common gases used in proportional counters

A
  1. 90% argon, 10% methane
  2. Propane
  3. BF3
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9
Q

What is exposure?

A

the correspondence to the amount of ionization charge collected per unit of mass of air

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10
Q

What is absorbed dose?

A

The measurement of ionization produced by radiation considering its avg energy needed to create an ion pair in the detector.

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11
Q

What is Dose Equivalent?

A

The true dose imparted to matter. Takes into account the quality factor for the type of radiation exposed.

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12
Q

Which factors affect detector response?

A

Temperature, humidity, and pressure

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13
Q

What is the process of radiation being detected?

A

Radiation goes into the detector, interacts with the scintillator, creates secondary electrons, secondary electrons interact with dynodes, electrons progressively multiply until it reaches 10^6 electrons, signal goes through pre-amp, then amp, the discriminator, then pulse shaper, lastly scaler/analyzer

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14
Q

What factors affect detector efficiency?

A

Geometry, backscatter, housing/other scatter, self-absorption, other absorption, intrinsic efficiency

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15
Q

How to calculate detector efficiency?

A

E= (# counts)
—————————
(# disintegrations)

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16
Q

Sample atoms (and activity) from counts equation

A

N= C
———————– and
E(1-e^(-λT)

A= λN or Count rate/Efficiency

17
Q

air sample activity from counts equation

A

A(T1)=. λC
_____________
E(1-e^(-λT3))e^(-λT2)

18
Q

What are the Neutron Energy classes?

A

Thermal (0.025 eV), Epithermal/slow (0.025-100 eV), Intermediate (100-10^5 eV), Fast (10^5-2x10^7 eV) Relativistic (2x10^7 eV)