LB Feb2017 Se Investigations
Neutron knockout on Se-82
While looking to see if certain lines are indeed selenium within the spectrum, it is worth noting that there are 2 states for Se-81. There is a metastable state with a 57 minute half life and a gamma emission of 103 keV. First I will attempt to show that this metastable state can indeed be seen in the spectrum.
Pure Selenium Sample
Below is an overlay of 5 plots with different cuts in time.
The half life was calculated using the program /data/IAC/Se/Feb2017Run/LB_WeightedFit.C
Using the slope, the half life can be found to be 58.9 +/- 11 minutes
Below is a plot of the data when it is exponentiated
Since the constant term is inside of the exponent, we must exponentiate the constant to get the (efficiency uncorrected) Activity at t=0.
So the uncorrected activity at t=0 is 379.56 +\- 25.04 Hz. Using the Ba-133 87 keV efficiency at 3.9 cm away from the face of detector B, which is 0.017, the corrected activity can be found to be
22327.06 +\- 1472.94 Hz which converts to 603.43 +\- 39.81 nCi
The sample was measured 55 minutes after the beam was shut off, which brings the activity to
1.14 +\- 0.07 uCi
10% Se Mixture
Below is an overlay of the spectra to see the decay over time of the line of interest
Now plot the activity as a function of time to get the half life.
ROOT gives values for the constant and the slope as 6.25731 +\- 0.0347460 and 0.000187704 +\- 0.0000213562 respectively. Using the values for the slope, the half life is found to be 61.55 +\- 7.00 minutes.
The uncorrected activity at t=0 can be found to be 521.65 +\- 18.26 Hz. Using the efficiency of Ba-133 at 3.9cm away from the face of detector B, the corrected rate is found to be 30685.29 +\- 1074.12 Hz. Converting this we get 0.83 +\- 0.03 uCi. Now the beam was shut off 140 minutes before the counting began, so tracing that back the initial activity of the sample as it came out of the beam is 4.02 +\- 0.15 uCi.
50% Se Mixture (reirradiated)
Below is an overlay of the line of interest
