egs_gammaspec: energy threshold in beta spectrum used in simulation

[ZootPaul]

Hi there,

the egs_gammaspec is a very useful code for detector simulations that I am currently working on.

The sources in these simulations are typically radionuclides e.g. Tl-204, which has a beta spectrum. To check what the beta spectrum used by the code looks like, I set 'output beta spectra = yes':

:start source:
name = filter_source
library = egs_radionuclide_source
base source = filter_source_iso
:start spectrum:
type = radionuclide
nuclide = Tl-204
atomic relaxations = eadl
output beta spectra = yes
:stop spectrum:
:stop source:

The file 'Tl-204_0.7637.spec' is output to the code folder. However, the spectrum starts at approximately 11 keV:
0.0008 0
0.0016 0
0.0024 0
0.0032 0
0.004 0
0.0048 0
0.0056 0
0.0064 0
0.0072 0
0.008 0
0.0088 0
0.0096 0
0.0104 0
0.0112 2.87724
0.012 2.87415
0.0128 2.87104
0.0136 2.86793
0.0144 2.86481
0.0152 2.86168
0.016 2.85854
...

although the theoretical spectrum begins at 0 keV. Could you please let me know how the energy threshold for the beta spectrum simulation using ENSDF input, can be reduced to say 1 keV?

The cut-off energies in my input file should allow for that:

Global ECUT = 0.5115 # Global electron transport cutoff
Global PCUT = 0.0005 # Global photon transport cutoff

[rtownson]

This is due to the algorithm that we use for the beta spectra, it is a known issue/approximation. My plan for the future is to integrate or allow for inputs from BetaShape. For now, unfortunately I don't have a good solution aside from editing the code yourself.