Fast neutron damage to HPGe Detector

From New IAC Wiki
Revision as of 07:00, 29 December 2016 by Burgjeff (talk | contribs)
Jump to navigation Jump to search

An observable decrease in the energy resolution of large HPGe detectors was first seen after the irradiation of 5*10^7 n/cm^2<ref>P. H. Stelson, J. K. Dickens, S. Raman, and R. C. Trammell, “Deterioration of Large Ge(Li) Diodes Caused by Fast Neutrons,” Nuclear Instruments and Methods 98,481 (1972).</ref>, so I consider a factor of ten below this to be a good conservative amount to make the maximum.

The maximum neutron flux occurs exactly at the center of the detector, where the expression for integral flux is simply: [math]\Delta t\times n_{rate}\frac{1}{4\pi d^2}[/math].

The number of days it would take to reach an integral flux of 5*10^6 n/cm^2, as a function of the distance from source to HPGe face is shown below. The graph assumes the activity of the Cf-252 source as of 01/2017, which is 19,066 n/s.

MaxHPGeCF252Time.png

  • The formula used in the graph above is,

[math]y=\frac{5\times 10^6}{(19066 * 60^2 * 24 * \frac{1}{(4*\pi * x^2)})}[/math]


References

<references />