Sub-keV energy deposition reporting issue?

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1

Hi, I have constructed a diamond material for which electrons are incident. I noticed that the energy deposition tracking of an electron through the material is sensible at the range of 1.2keV and above. However as I get to energies at the eV scale the Edep reporting simply drops off and treats the detector seemingly like a vacuum. I don’t believe this is the actual physics of what would happen and I would think that the electrons would most often deposit all their energy through ionization (band-gap for diamond is approx 13.6 eV). The diamond is super thin (50 micrometers). I am using the physics list FTFP_BERT_LIV and I am using a step size of .0001mm. Here is an example output for a single event for a 400eV incident electron where Det1 (boundary defined in global coordinates from 999.975 to 1000.025 mm) is the volume containing the diamond:

=================== Event 2 ==================
=========== EventID 2 TrackID 1 e- ParentID 0 KE=0.000MeV CreatorProcess=Beam ===========
Step StepLen CL: X Y Z dxdz dydz KE(MeV) This Volume Particle Ex,Ey,Ez (MV/meter) Process
1 5.00000 0.0000 0.0000 5.0000 0.0000000 0.0000000 0.0004 BeamVis e- 0.0000 0.0000 0.0000 Transportation
2 100.00000 0.0000 0.0000 105.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
3 100.00000 0.0000 0.0000 205.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
4 100.00000 0.0000 0.0000 305.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
5 100.00000 0.0000 0.0000 405.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
6 100.00000 0.0000 0.0000 505.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
7 100.00000 0.0000 0.0000 605.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
8 100.00000 0.0000 0.0000 705.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
9 100.00000 0.0000 0.0000 805.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
10 100.00000 0.0000 0.0000 905.0000 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 StepLimiter
11 94.97500 0.0000 0.0000 999.9750 0.0000000 0.0000000 0.0004 World e- 0.0000 0.0000 0.0000 Transportation
12 0.00010 0.0000 0.0000 999.9751 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
13 0.00010 0.0000 0.0000 999.9752 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
14 0.00010 0.0000 0.0000 999.9753 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
15 0.00010 0.0000 0.0000 999.9754 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
16 0.00010 0.0000 0.0000 999.9755 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
17 0.00010 0.0000 0.0000 999.9756 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
18 0.00010 0.0000 0.0000 999.9757 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
19 0.00010 0.0000 0.0000 999.9758 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
20 0.00010 0.0000 0.0000 999.9759 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
21 0.00010 0.0000 0.0000 999.9760 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
22 0.00010 0.0000 0.0000 999.9761 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
23 0.00010 0.0000 0.0000 999.9762 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
24 0.00010 0.0000 0.0000 999.9763 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
25 0.00010 0.0000 0.0000 999.9764 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
26 0.00010 0.0000 0.0000 999.9765 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
27 0.00010 0.0000 0.0000 999.9766 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
28 0.00010 0.0000 0.0000 999.9767 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
29 0.00010 0.0000 0.0000 999.9768 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
30 0.00010 0.0000 0.0000 999.9769 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
31 0.00010 0.0000 0.0000 999.9770 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
32 0.00010 0.0000 0.0000 999.9771 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
33 0.00010 0.0000 0.0000 999.9772 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
34 0.00010 0.0000 0.0000 999.9773 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
35 0.00010 0.0000 0.0000 999.9774 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
36 0.00010 0.0000 0.0000 999.9775 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
37 0.00010 0.0000 0.0000 999.9776 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
38 0.00010 0.0000 0.0000 999.9777 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
39 0.00010 0.0000 0.0000 999.9778 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
40 0.00010 0.0000 0.0000 999.9779 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
41 0.00010 0.0000 0.0000 999.9780 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
42 0.00010 0.0000 0.0000 999.9781 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
43 0.00010 0.0000 0.0000 999.9782 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
44 0.00010 0.0000 0.0000 999.9783 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
45 0.00010 0.0000 0.0000 999.9784 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
46 0.00010 0.0000 0.0000 999.9785 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
47 0.00010 0.0000 0.0000 999.9786 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
48 0.00010 0.0000 0.0000 999.9787 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
49 0.00010 0.0000 0.0000 999.9788 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
50 0.00010 0.0000 0.0000 999.9789 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
51 0.00010 0.0000 0.0000 999.9790 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
52 0.00010 0.0000 0.0000 999.9791 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
53 0.00010 0.0000 0.0000 999.9792 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
54 0.00010 0.0000 0.0000 999.9793 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
55 0.00010 0.0000 0.0000 999.9794 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
56 0.00010 0.0000 0.0000 999.9795 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
57 0.00010 0.0000 0.0000 999.9796 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
58 0.00010 0.0000 0.0000 999.9797 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
59 0.00010 0.0000 0.0000 999.9798 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
60 0.00010 0.0000 0.0000 999.9799 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
61 0.00010 0.0000 0.0000 999.9800 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
62 0.00010 0.0000 0.0000 999.9801 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
63 0.00010 0.0000 0.0000 999.9802 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
64 0.00010 0.0000 0.0000 999.9803 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
65 0.00010 0.0000 0.0000 999.9804 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
66 0.00010 0.0000 0.0000 999.9805 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
67 0.00010 0.0000 0.0000 999.9806 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
68 0.00010 0.0000 0.0000 999.9807 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
69 0.00010 0.0000 0.0000 999.9808 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
70 0.00010 0.0000 0.0000 999.9809 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
71 0.00010 0.0000 0.0000 999.9810 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
72 0.00010 0.0000 0.0000 999.9811 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
73 0.00010 0.0000 0.0000 999.9812 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
74 0.00010 0.0000 0.0000 999.9813 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
75 0.00010 0.0000 0.0000 999.9814 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
76 0.00010 0.0000 0.0000 999.9815 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
77 0.00010 0.0000 0.0000 999.9816 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
78 0.00010 0.0000 0.0000 999.9817 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
79 0.00010 0.0000 0.0000 999.9818 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
80 0.00010 0.0000 0.0000 999.9819 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
81 0.00010 0.0000 0.0000 999.9820 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
82 0.00010 0.0000 0.0000 999.9821 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
83 0.00010 0.0000 0.0000 999.9822 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
84 0.00010 0.0000 0.0000 999.9823 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
85 0.00010 0.0000 0.0000 999.9824 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
86 0.00010 0.0000 0.0000 999.9825 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
87 0.00010 0.0000 0.0000 999.9826 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
88 0.00010 0.0000 0.0000 999.9827 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
89 0.00010 0.0000 0.0000 999.9828 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
90 0.00010 0.0000 0.0000 999.9829 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
91 0.00010 0.0000 0.0000 999.9830 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
92 0.00010 0.0000 0.0000 999.9831 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
93 0.00010 0.0000 0.0000 999.9832 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
94 0.00010 0.0000 0.0000 999.9833 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
95 0.00010 0.0000 0.0000 999.9834 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
96 0.00010 0.0000 0.0000 999.9835 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
97 0.00010 0.0000 0.0000 999.9836 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
98 0.00010 0.0000 0.0000 999.9837 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
99 0.00010 0.0000 0.0000 999.9838 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
100 0.00010 0.0000 0.0000 999.9839 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
101 0.00010 0.0000 0.0000 999.9840 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
102 0.00010 0.0000 0.0000 999.9841 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
103 0.00010 0.0000 0.0000 999.9842 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
104 0.00010 0.0000 0.0000 999.9843 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
105 0.00010 0.0000 0.0000 999.9844 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
106 0.00010 0.0000 0.0000 999.9845 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
107 0.00010 0.0000 0.0000 999.9846 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
108 0.00010 0.0000 0.0000 999.9847 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
109 0.00010 0.0000 0.0000 999.9848 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
110 0.00010 0.0000 0.0000 999.9849 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter
111 0.00010 0.0000 0.0000 999.9850 0.0000000 0.0000000 0.0004 Det1 e- 0.0000 0.0000 0.0000 StepLimiter

*** G4Exception: Stuck Track – Killed
*** severity: Warning
*** issued by: BLManager Stepping Action
*** description: 100 steps in a row, each less than 0.1 micron and 0.1 ps
*** EventID: 2 TrackID: 1 e- KE=0.0003912 MeV

detector Det1: EDep=0.000 VisibleEdep=0.000 Ntracks=1
Event 2 Completed 2 events realTime=1 sec 2.0 ev/sec

I am inclined to believe that these results are not to be taken literally, or is it really that the cross-section drops off so dramatically at 1.2keV and below and I am mistaken? Note using a larger step size shows the particle traversing uninterrupted through the entire detector.

Thanks!

2

Nevermind, I had not implemented the livermore package as intended for the output shown above. I corrected this and as I look through the finer steps of each process it does seem to do the job.

However the resolution in terms of the position tracker for z (the variable concerning the depth through the material) is a bit lacking for my intended analysis at this low of an energy. All the energy is being reported as lost on the surface and I wish for a finer grained response if possible. Using a very small step size does not seem to change anything. Any tips would be appreciated. However consider the initial issue solved. Thanks