Used file for the fit: SDD_normalized-Efficiency_point-source_with-air_all-levels.csv

parameters
offset a	slope b
-8.073e-06	0.000457334

Covariance matrix
5.1617e-13	-2.1811e-11
-2.1811e-11	9.36223e-10

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.15	1.01806e-05	5.1627e-07	Ba133
80.96	2.34488e-06	9.10801e-08	Ba133
