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

parameters
offset a	slope b
-5.9008e-06	0.000336314

Covariance matrix
1.07165e-13	-4.36811e-12
-4.36811e-12	1.85012e-10

used data points for fitting
energy [keV]	efficiency	efficiency error	nuclide
53.16	7.71931e-06	3.94357e-07	Ba133
80.99	1.74607e-06	6.53776e-08	Ba133
26.34	5.61625e-05	3.8763e-06	Am241
33.19	2.90054e-05	2.61272e-06	Am241
59.53	5.42361e-06	3.71007e-07	Am241
