Labs excel

Question 1

How to find the optimal ID level?

Answer 1

1) calculate the pulse count without noise (signal)
2) calculate the signal to noise ratio
3) plot signal to noise ration as a function of discriminator value
4) find first peak in the graph
(ID-Level at around 1,25V)

Question 2

Dosimetry Lab

1. Name the visible ranges?
2. Find the equivalent dose rate?

Answer 2

Crucial steps

1) plot the chamber current as a function of chamber voltage
2) name the Visible ranges
3) Using the exposure formula and equivalent dose rate formula

Question 3

Dosimetry Lab

Explain the recombination region?

Answer 3

At low voltage, the electric field is not large enough to accelerate electrons and ions.

• > The electrons and ions can recombine soon after they are produced, and only a small fraction of the produced electrons and ions reach their respective electrodes.
• > Detectors are not operated in this region, because neither the number of recombinations nor the number of ion-pairs initially produced can be determined accurately.
• > As the detector voltage is increased, however, an increasingly large fraction of the ions produced will reach the electrodes. This increase continues until the “saturation” voltage is attained.

Question 4

Dosimetry Lab

Explain the saturation region (ionization region)?

Answer 4

In the ionization region, an increase in voltage does not cause a substantial increase in the number of ion-pairs collected.
-> The number of ion-pairs collected by the electrodes is equal to the number of ion-pairs produced by the incident radiation, and is dependent on the type and energy of the particles or rays in the incident radiation. Therefore, in this region the curve is flat.

( The voltage must be higher than the point where dissociated ion-pairs can recombine)

Question 5

Dosimetry Lab

Explain the counting proportional region?

Answer 5

In the proportional region, the charge collected increases with a further increase in the detector voltage, while the number of primary ion-pairs remains unchanged.

( When instruments are operated in the proportional region, the voltage must be kept constant. If a voltage remains constant the gas amplification factor also does not change.)

Question 6

GAMMA ABSORPTION LAB

Find the linear attenuation coefficient!
Find the mass attenuation coefficient!
Calculate the half value layer!
Estimate the photonenergy if the absorbing material was lead!

Answer 6

1. Plot the graph “ the thickness as a function of pulse count”
2. Read the exponent -> linear attenuation coefficient
3. Mass attenuation coefficient = µ/p
4. Half value layer = ln2/µ
5. Using the lab manual, in the “components of the mass attenuation coefficient of lead” section -> estimate photoenergy

Question 7

GAMMA ENERGY LAB

=> Find the photon energy of the unknown isotope!

Answer 7

1. plot pulse frequency distribution of all the measurements
2. Find the photopeak according to ID level
3. The ratio of the 2 photopeak = the ratio of the activity (photon energy) of the 2 isotopes

Question 8

COULTER COUNTER

Find the discriminator level for the RBC setting
Find the concentration of the tested suspension
Create a DD-spectrum of the data

Answer 8

1. Plot the graph “pulse number vs ID level” (amplitude frequency distribution)
2. Find calibration factor
3. We start the range when there is a significant change
4. Calculate the pulse frequencies for amplitude of classes width 0.5V
5. Why do we need a DD-spectrum for the data?
   - > Because DD is used to find the size distribution of the pulses
   - > Therefore, we need to determine the frequency distribution
6. What happen at the start of the ID graph (upper one)
   - > I think because there are still platelets counted and we haven’t counted the RBCs or WBCs at this point yet

Question 9

FLOW LAB

1. Check if the prediction of the Hagen-Poiseuille law holds (pressure and radius dependence of the volumetric flow rate)!
2. Find the viscosity of the liquid!

Answer 9

For question 1.

• Go to the 1st experiment
  (1) Find the average pressure drop = gravity x density x average height; the volumetric flow rate = flow through VOLUME/flow through TIME
  (2) Plot a linear graph between pressure drop and Iv -> Iv ~ pressure drop
• Refer to the 2nd experiment
  (3) Find Iv based on radius
  (4) Plot a graph between Radius (do NOT power it to 4) and Iv
• > power relationship

Conclusion: the Hagen-Poiseuille law holds

For question 2, pls refer to the 2nd experiment
(1) Choose a radius with corresponding Iv
(2) Find the viscosity = (pi x r^4 x pressure difference)/(8 x Iv x length of measuring tube)
!!! Iv already including the time, so please don’t multiply it with extra time

Question 10

DIFFUSION LAB

Find the diffusion coefficient!
Find the time needed to for the diffusing molecules to cover on average a distance of 2.4 mm!

Answer 10

Q#1
1) The average distance is proportional to square root of time
=> Find square root of time in second
=> Plot the graph average distance as a function of square root of time
=> finding the slope and then find the diffusion coefficient

Q#2
Convert the distance into meter
=> Apply the formula to find the time needed (The R average ~ square root of time)
=> Find the time needed

Question 11

CT LAB

Reconstruct the plane

Answer 11

1. Find the photon count w/o back ground
2. Find the Density = log (Jo/J)
3. Construct the plane
4. The higher the value = the more attenuation -> it means there must be sth there

Question 12

X-ray 1

Check the validity of the Duane-Hunt law!

Answer 12

1. Plot 5 series with wavelength corresponding to pulse count
2. Find the cut off frequency
3. Plot the graph cut off wavelength as a function of 1/anode voltage
4. Add trendline
5. Increasing wavelength -> anode voltage decreases

Question 13

X-RAY 2

How does the emitted X-ray power depend on the anode current?

Answer 13

Plot sums of pulse counts as a function of anode current

-> linear function

Question 14

X-ray 3

Find the dependence of the partial mass attenuation coefficient of photoeffect on the atomic number!

Answer 14

1. Find the attenuation coefficient (X-ray formula) by using incident intensity (photon count without material) and intensity with materials
2. Find mass attenuation coefficient
3. Find partial mass attenuation coefficient
4. Plot the graph partial mass attenuation coefficient of photo effect as a function of photoeffect on the atomic number
5. Power function is best fit