Method and device for measuring gamma radiation

A method for calibrating a device for measuring gamma radiation within a multiple channel energy spectrum measurement range having lower and upper channels corresponding, respectively, to minimum and maximum energy values of the energy spectrum, said method comprising:

• (a) determining a minimum count channel and a maximum count channel within the range;
• (b) determining whether a peak has been detected within the range by the relationship between the counts of the minimum and maximum count channels;
• (c) upon determining that a peak has been detected, determining a first channel having approximately one-half of the maximum number of counts;
• (d) determining a second channel representing Compton background energy;
• (e) computing a peak energy centroid channel from the first channel and the second channel;
• (f) computing a channel to energy conversion factor from the peak energy centroid channel;
• and
• (g) computing lower and upper calibrated measurement range channels respectively by multiplying the energy to channel conversion factor by the minimum energy value and the maximum energy value

An apparatus for measuring gamma radiation comprising:

• means for detecting gamma radiation emissions and for producing electrical signal each of said signals being of a magnitude proportional to a level of energy of each emission;
• conversion means for converting the electrical signals produced by the detecting means to digital words each of said words corresponding to a particular emission energy level;
• means for counting the number of words corresponding to each emission energy level within a gamma ray stripping window having a lower boundary word corresponding to a lower boundary energy level and an upper boundary word corresponding to an upper boundary energy level;
• means for computing a word to energy conversion factor;
• means for computing a stabilized lower boundary word by multiplying the lower boundary energy level by the word to energy conversion factor;
• and
• means for computing a stabilized upper boundary word by multiplying the upper boundary energy level by the word to energy conversion factor.

A method of stabilizing a gamma ray stripping window in a gamma ray energy spectrum, said stripping window having a lower boundary energy value, an upper boundary energy value, and a peak energy value positioned between said lower and upper boundary energy values, which comprises the steps of:

• partitioning said gamma ray energy spectrum into a plurality of channels, each of said channels corresponding to a particular energy within said spectrum;
• computing a channel to energy conversion factor;
• computing a stabilized lower boundary channel by multiplying the lower boundary energy value by the channel to energy conversion factor;
• and
• computing a stabilized upper boundary channel by multiplying the upper boundary energy value by the channel to energy conversion factor.