Fabrication, integration and operation of multi-function radiation detection systems
Radiation detectors and methods of use thereof that produce more accurate results. A region of the radiation detector is covered by a conversion layer. A reference region is covered by a light barrier material such as a metal, and not the conversion layer. The reference region incurs less radiation damage than the region under the conversion layer. The dark current produced by the reference region can be used to more accurately calibrate the detector, provide real time normalization of the current produced by the conversion layer region, and determine when the detector has been damaged sufficiently to be replaced.
1. A radiation detector comprising:
a first region of a silicon detector covered by a conversion layer; and
a second region of the silicon detector covered by a light barrier and not the conversion layer.
2. The radiation detector of claim 1 wherein the second region is located along the outer edge of the silicon detector.
3. The radiation detector of claim 2 wherein the second region extends between approximately 1 and 10 microns from the edges of the silicon detector.
4. The radiation detector of claim 1 wherein the light barrier comprises a metal.
5. The radiation detector of claim 1 wherein the light barrier blocks photons having an energy approximately below that of soft x-rays.
6. The radiation detector of claim 1 further comprising a third region of the silicon detector not covered by either the conversion layer or the light barrier.
7. The radiation detector of claim 6 wherein the third region is between the first region and the second region.
8. A method for measuring current produced by a radiation detector, the method comprising:
determining which detector pixels in a first region of a silicon detector covered by a conversion layer are non-faulty detector pixels;
measuring a current produced by detector pixels in a second region of the silicon detector beneath a light barrier but not beneath the conversion layer;
averaging the current to a per-detector-pixel value; and
subtracting the value from a current produced by each non-faulty detector pixel in the first region.
9. The method of claim 8 wherein the determining step comprises:
placing the radiation detector in a shielded environment;
measuring dark current produced by detector pixels in the second region;
averaging the dark current to a per-detector-pixel dark current value;
subtracting the dark current value from the dark current produced by each detector pixel in the first region to produce a calibration dark current value; and
labeling each detector pixel in the first region that has a calibration dark current value of approximately zero as a non-faulty detector pixel.
10. The method of claim 9 further comprising;
placing the radiation detector in a shielded environment after the radiation detector has been in normal use for a period of time;
measuring dark current produced by detector pixels in the second region;
averaging the dark current to a per-detector-pixel dark current value;
subtracting the dark current value from the dark current produced by each detector pixel in the first region to produce a final dark current value;
determining the number of detector pixels in the first region that each have a dark current value of approximately zero; and
replacing the radiation detector when the number of non-faulty detector pixels in the first region is a predetermined number less than the number of non-faulty detector pixels measured in the determining step.
11. The method of claim 9 further comprising:
placing the radiation detector in a shielded environment after the radiation detector has been in normal use for a period of time;
measuring dark current produced by the detector pixels in the first region; and
replacing the radiation detector when the dark current is greater by a predetermined amount than a dark current produced by the detector pixels in the first region measured during the determining step.
12. The method of claim 9 further comprising;
placing the radiation detector in a shielded environment after the radiation detector has been in normal use for a period of time;
measuring dark current produced by detector pixels in the second region;
averaging the dark current to a per-detector-pixel dark current value;
subtracting the dark current value from the dark current produced by each detector pixel in the first region to produce a final dark current value; and
replacing the radiation detector when the final dark current value is greater by a predetermined amount than the calibration dark current value.
13. The method of claim 8 wherein the second region is located along the outer edge of the silicon detector.
14. The method of claim 13 wherein the second region extends between approximately 1 and 10 microns from the edges of the silicon detector.
15. The method of claim 8 wherein the light barrier comprises a metal.
16. The method of claim 8 wherein the light barrier blocks photons having an energy approximately below that of soft x-rays.
17. The method of claim 8 wherein the radiation detector further comprises a third region of the silicon detector not covered by either the conversion layer or the light barrier.
18. The method of claim 17 wherein the third region is between the first region and the second region.
19. The method of claim 17 wherein a dark current produced by detector pixels in the third region is used to determine a total radiation dose measured by the radiation detector.