Tritium and neutron measurements of a solid state cell Page: 4 of 17
16 p.View a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
2
important. The silicon oxide layer is approximately 150 A thick. Figure 2
shows the unusual morphology of the palladium powder (formed during
precipitation) and also the silicon powder size and shape. After pressing,
the powdei ^s as shown in figure 3.
A voltage current plot of the cell indicates that the resistance of the
cell is primarily controlled by the silicon oxide layer. Shown in Figure U
are the V-I curves, for cells 10 and 12. Typically the curves are highly
non linear suggesting the current is due to tunnelling or a variety of
ocher conduction mechanisms that have been observed in MIS devices. The
V-I curve is taken under pulsed conditions so as not to heat the cell by
more than a few degrees.
To enhance the detection of the neutrons and to obtain the highest current
densities possible, a pulsed excitation source was used in all the
experiments. The voltage and current pulse used was of 1 microsecond to 1
millisecond in duration at up to 3000 V at currents as high as 0.5 amp with
a low duty cycle (such as 10 milliseconds) to reduce joule heating.
Usually the pulse width and duty cycle were adjusted so that one watt of
power was dissipated in the cell, however, the peak power was often 100 or
more watts. This limited the Joule heating to a few degrees resulting in
little change in the average D/Pd ratio. The neutron detector consisted of
a bank of 15 helium 3 proportional counters moderat^^by polyethylene. The
efficiency of this system as measured with a Cf source was 1.3%.
Instead of energy discrimination, time correlation was used. The pulse to
the cell triggered the time of flight electronics of the Low-Q diffracto-
meter at LANSCE. This was intended to give a concurrent background
measurement by recording counts well after the current pulses. A schematic
of the experimental apparatus is shown in Figure 5.
To test for tritium by-products, a gas line was constructed using an
ionization gauge as the measurement device. These devices reject radon and
other ionization mechanism that do not produce ionization characteristic of
18.6 KcV electrons. A schematic of the system is shown in Figure 6. The
system is used to pump down and fill the cell as well as measure the
tritium in the deuterium gas initially and after operntion of Lite cell.
ResultB:
Eleven cells have been built to date. The most, positive results were
obtained on cell 2, which was pulsed with 500 to 2000 V /it ‘100 to 25
microsecond pulse widths with pulse rates of 80 Hz or less. The Input
power from Joule heating was usually held at 500 to 2000 milliwatts so that
the D/I’d rat In would not change !: I gnl f I cant I y. At one w/it t tin' cell heated
to ahum 6 C above ambient in t lie neutron counter rave.
Tin- neutron counting results did not show unv definite time correlation on
t line scales shorter that the pulse repet It ion rate. Instead of t line
correlat Ion. it was found that the count rate when the sample was pulsed
was higher t halt (lie bar h. ground with or without the eel] or when a resistor
was pulsed. Measurements taken e.-irlv n the ’lie of the cell gave higher
lie'll i on counts than those taken live days later. Tills Is shown most
clearly In Figure / where the neutron count has hern roughly eoiielated
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.
Claytor, T. N.; Seeger, P. A.; Rohwer, R. K.; Tuggle, D. G. & Doty, W. R. Tritium and neutron measurements of a solid state cell, article, January 1, 1989; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1064944/m1/4/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.