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Applying the pulsed ion chamber methodology to full range reactor ...

Applying the pulsed ion chamber methodology to full range reactor ...

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They were placed side by side in a cylindrical styrofoam mold and lowered in 6 inch increments down into the radiation port, while the computer system, recorded v(t ) and J of both chambers at each point. The code used to control the system is given in the Appendix under the title PIC System Data Recording Code. Note this code was used to take all the v(t ), R/hr, and I data reported in this chapter. Typical plots of the v(t ), I , and R/hr data taken are shewn in figures 4-3, 4-4, and 4-5. It is immediately apparent from figures 4-3 and 4-4 that the chamber with the U deposited on its walls was 3 times more sensitive to gamma radiation. This fact shows that the composition of the wall material has a strong effect on the gemma sensitivity of a giver, chamber. The non- linearity observed in the low-end response of the neutron sensitive 234 chamber was dv,e to ionization produced by the ° U alpha activity in the uranium coating on its inner walls. In the plot of v(t ) versus I it can be seen that the curves for the two chambers lie virtually on top of each other. It shall be remembered that S, the ionization source strength is linearly related to I s _, i.e., S . 13* eu where e and U denote, the unit of electronic charge in coulombs and sensitive volume of the chamber, respectively. Thus figure 4-5 shows that., at a given ion production rate S, regard- less of which chamber is used, the resulting measured v(t c ) is the same. This proves that the chambers and electronics fcr each channel are closely matched, a very basic requirement for gamma compensation. Note, however.