Difference between revisions of "Calibration Info"
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::The setup for the custom calibration uses a distance of 30cm from the faceplate of the source to the OSLs in an attempt to achieve some uniformity of the radiation field across the subjected OSLs. The distance from the faceplate to the surface of the source needs to be taken into account given the <math>\frac{1}{D^{2}}</math> dependency of the exposure rate. The total distance D is then, D = (Distance to faceplate +11.2cm) ''{as provided by the Technical Safety Office at Idaho State University''}. The exposure rate for any given distance is calculated in units of Roentgen using the equation <math> \dot R = \frac {\Gamma A }{ D^2} </math>. A gamma factor of, <math> {\Gamma} = 0.33 \frac {(m^2)(R)}{(Ci)(hr)} </math> and activity <math>{A} = 9.3 Ci </math> is used in these calculations. With the exposure rate found with these known variables, it is possible to find the total exposure given to the Nanodot OSLs by integrating the exposure rate over the time the OSL was exposed to the source, <math>R_{tot}=\int\limits_{t_0}^{t_f}\dot R\ dt </math>. ''It is necessary when working with exposure to be able to convert to units supplied by the OSL reader and through unit analysis it was found that 1.14554 Roentgen = 1 Rad''. | ::The setup for the custom calibration uses a distance of 30cm from the faceplate of the source to the OSLs in an attempt to achieve some uniformity of the radiation field across the subjected OSLs. The distance from the faceplate to the surface of the source needs to be taken into account given the <math>\frac{1}{D^{2}}</math> dependency of the exposure rate. The total distance D is then, D = (Distance to faceplate +11.2cm) ''{as provided by the Technical Safety Office at Idaho State University''}. The exposure rate for any given distance is calculated in units of Roentgen using the equation <math> \dot R = \frac {\Gamma A }{ D^2} </math>. A gamma factor of, <math> {\Gamma} = 0.33 \frac {(m^2)(R)}{(Ci)(hr)} </math> and activity <math>{A} = 9.3 Ci </math> is used in these calculations. With the exposure rate found with these known variables, it is possible to find the total exposure given to the Nanodot OSLs by integrating the exposure rate over the time the OSL was exposed to the source, <math>R_{tot}=\int\limits_{t_0}^{t_f}\dot R\ dt </math>. ''It is necessary when working with exposure to be able to convert to units supplied by the OSL reader and through unit analysis it was found that 1.14554 Roentgen = 1 Rad''. | ||
| − | ::The Microstar reader used to analyze the OSLs produces a numeric quantity for the total accumulated dose by reading the PMT counts, which is then input into <math> \ | + | ::The Microstar reader used to analyze the OSLs produces a numeric quantity for the total accumulated dose by reading the PMT counts, which is then input into <math> accumulated\ dose = \frac{PMT Counts}{(Cal. Factor)(OSL Sensitivity)}</math> along with the OSL sensitivity and calibration factor. By creating a custom calibration, the calibration factor has no effect on subsequent OSL analyzation as a direct relationship is found between PMT counts and total exposure. |
Revision as of 02:24, 18 May 2018
- It is this calibration factor, found by creating a calibration with the provided pre-dosed OSLs that is brought into question. By subjecting the OSLs to a known total exposure, it is possible to eliminate the effect of any unknown factors in the listed dose on the provided OSLs. Therefore to fully understand the relationship between background subtracted PMT (photo multiplier tube) Counts and total exposure for the Nanodot OSLs, a custom calibration is needed. This calibration is used in lieu of the calibration given by the OSL reader, which is created using the pre-dosed OSLs. To begin the calibration, a set of fifteen previously unexposed Nanodot OSLs is chosen at random and exposed to a 9.3Ci Cesium-137 source.
- The setup for the custom calibration uses a distance of 30cm from the faceplate of the source to the OSLs in an attempt to achieve some uniformity of the radiation field across the subjected OSLs. The distance from the faceplate to the surface of the source needs to be taken into account given the dependency of the exposure rate. The total distance D is then, D = (Distance to faceplate +11.2cm) {as provided by the Technical Safety Office at Idaho State University}. The exposure rate for any given distance is calculated in units of Roentgen using the equation . A gamma factor of, and activity is used in these calculations. With the exposure rate found with these known variables, it is possible to find the total exposure given to the Nanodot OSLs by integrating the exposure rate over the time the OSL was exposed to the source, . It is necessary when working with exposure to be able to convert to units supplied by the OSL reader and through unit analysis it was found that 1.14554 Roentgen = 1 Rad.
- The Microstar reader used to analyze the OSLs produces a numeric quantity for the total accumulated dose by reading the PMT counts, which is then input into along with the OSL sensitivity and calibration factor. By creating a custom calibration, the calibration factor has no effect on subsequent OSL analyzation as a direct relationship is found between PMT counts and total exposure.
Using this conversation allowed for a linear fit calibration to be created to visualize the relationship between background subtracted PMT counts and calculated dose. This calibration is then used to get well understood measurements during experiments involving the Nanodot OSLs.
It is this calibration factor that is determined by the pre-dosed OSLs and can see the relationship between the PMT counts and exposed dose.
Add formula for OSL reader (maybe better in OSL reader section?)
Add linear fit
High dose and low dose