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. The window in root was [98:108] on the energy axis. Looking at the counts, dividing by the total run time, and taking the natural log of the activity is how the linear fit is created.

50% Se Mixture

PAA_Selenium