Fast digitization and discrimination of prompt neutron and photon signals using a novel silicon carbide detector Page: 8 of 9
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Pulse Amplitude (V)
-1ZBz 20m 40m 60m 80m 10Dm 120m 140m 160m 180m 20Dm
10000-
,Neutrons I' 3105 I
Pulse Height Spectra amns 3126858
iDOD - I am5 65
2 100-
0
10 -
S.Sn -
Sn -
4.5n -
4n-
3.sn-
3n -
w 2.Sn-
2n- ' t
1.5n -
in- '.n d
SD0p -
0-I
0 20m 40m 60m 80m 10Dm 120m 140m 160m 180.02m 200m
Amplitude (V)
Figure 7. PSD applied to a mixed field radiation environment resulting in improved n:y detection ratio.
4. CONCLUSIONS
PSD has been demonstrated to be a viable mechanism to differentiate between gamma and neutron produced signals in
SiC detectors. PSD is possible in a SiC diode because the shape and timing of the signal produced is dependent largely
on the type of radiation causing the interaction. Gamma radiation will interact primarily through Compton scattering
with atomic electrons of the silicon, carbon, or nitrogen dopants in the materials. Recoil electrons are then emitted with
ranges that are generally much larger than the thickness of the active layer. As these electrons pass through the active
layer they generate ion-hole pairs which are collected and registered as signal. Photons greater than 1.022 MeV can also
lead to pair production in the material, primarily the silicon, but this is typically 10-100 times less likely than Compton
scattering for photons below 10 MeV. Because the ion-hole pairs generated through gamma interactions are dispersed
throughout the active volume, the charge collection time is slightly greater than that caused by heavier charged particles.
Neutrons, on the other hand, interact either through proton recoils generated in the polyethylene conversion layer placed
on the upper edge of the diode or through (n,cx) or (n,p) reactions directly in the silicon or carbon, if the neutron energy
is sufficient. These heavy charged particles deposit their energy within a few tens of microns of the originating location.
This results in a faster charge collection time when compared with gamma events. Exploitation of these differences in
the risetime of the signal has been shown to separate gammas and neutrons in intense mixed fields which are indicative
of active interrogation applications. Neutron signals were found to have broad amplitude spectra with risetimes falling
within a narrow band centered around 1.25 ns. Gamma signals were found to have a much broader spectrum of
risetimes and to have amplitudes of less than a few tens of mV.
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Blackburn, Brandon W.; Johnson, James T.; Watson, Scott M.; Chichester, David L.; Jones, James L.; Ruddy, Frank H. et al. Fast digitization and discrimination of prompt neutron and photon signals using a novel silicon carbide detector, article, April 1, 2007; [Idaho Falls, Idaho]. (https://digital.library.unt.edu/ark:/67531/metadc887413/m1/8/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.