# Energy Calibration by a 152Eu source

The γ-ray energies from the 152Eu decay is well determined, and it is a popular source to do energy calibration forγ-ray Germanium detectors. The disadvantage is that the highest energy for the easily-identifiable γ-ray line is relatively low, only at 1408 keV. There could be some deviations for the higher energy region.

Before Energy calibration, the channel number is reading from the electric modules not the energy yet. Typically the relation between the energy and channel number can be considered as linear.
In other word: E = c0 + c1*ch + c2*ch^2 + ...
c2 and the higher order coefficients c's are extremely small.

you can use any tool to do the linear regression to find the c0 and c1 term, and you can also check my calibration code that automatically find the peaks for you, and print pretty results for you. FSU_calib

Figure: a spectrum of 152Eu source

# Relative efficiency calibration by a 152Eu source

You may also interest in getting detecting efficiency (eff) for your Germanium detectors. 'eff' is a function of γ-ray energy. We usually interpret the eff(Egamma) function as:

$\dpi{120}&space;\LARGE&space;\large{&space;\epsilon_{eff}&space;=&space;10^{A}\cdot(E_{\gamma})^{B}\cdot(E_{\gamma}^{2})^{C}\cdot(&space;10^{\frac{D}{E_{\gamma}^{2}}&space;}&space;),&space;\textrm{&space;or}&space;}&space;\\&space;\large{\mathrm{log_{10}}(\epsilon_{eff})&space;=&space;A&space;+&space;B\cdot\mathrm{log_{10}}(E_{\gamma})&space;+&space;C\left(&space;\mathrm{log_{10}}(E_{\gamma})&space;\right)^{2}&space;+&space;\frac{D}{&space;(E_{\gamma})^{2}&space;}.&space;\label{eqn:photoelectric_absorption_efficiency}&space;}$

Because the intensities of the γ-ray lines from the 152Eu source are well determined as well. We use the counts of the peaks to do the relative efficiency calibration. ECAL is one of the available tools to fit and get the coefficients of A, B, C, D, E in the above equations.

Figure: Relative efficiency curve for detecting γ rays