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Home Software (Windows & Mac OSX) Gamma Radiation Detector

Gamma / X-Ray Radiation Detector

The Mac OSX Application (download v1.0 / 27.12.2011) implements a high energy photon detector for Gamma and X-Ray radiation sources using the built-in iSight WebCam of a MacBook Pro.

Additionally an iOS iPhone Application wich uses the built-in front camera to detect high energy photons can be downloaded here.

The screenshot shows an active measurement where the logged EPM/PEM values of the 4th and 9th row indicate an event of high energy photon detection

 

OVERVIEW:
The application uses the CMOS Image Sensor of the MacBook Pro built-in iSight WebCam to detect high energy photons generated by X-Ray or Gamma radiation sources.
Radiation measurements are presented as relative values. The image sensor is not a calibrated device to detect ionizing radiation in a perfectly reproduceable way which prevents absolute measurements in Gray (Gy) or dose equivalent in Sievert (Sv).

SETUP & STEPS FOR MEASURING:
1.) IMPORTANT: Make sure that visible light cannot hit the sensor by obscuring the camera lens, e.g. with a piece of black tape.
2.) Place the device in a low radiation environment.
3.) Adjust the threshold slider to a value which sets the reading of the CPM to around 1-5 Counts Per Minute without a detected high energy photon. It is important that the threshold isn't set too low because the sensor noise could render the measurement results unusable. If the threshold is to high then the detector looses sensitivity.
4.) The image sensor noise depends on its temperature which implies that the threshold needs to be adapted accordingly.
5.) Position the device near to a radiation source to be measured.
6.) Because of the small size of the CMOS-Sensor it can take some time until a high energy photon hits the sensor. Plan for a longer measurement (several minutes) to detect weak radiation sources.
7.) Analyze the logged data by checking the CPM (Counts Per Minute), EPM (Average Energy Per Minute) and PEM (Peak Energy Per Minute) to identify radiation events. The application autodetects probable events and indicates them by a "+" sign in the log view.


MEASUREMENTS:

All readings are relative values by intention because the system isn't calibrated and consistent enough to calculate absolute values.
EVT
- High Energy Photon Events autodetected by the App [(EPM-Threshold) ≥ 4 and (PEM-Threshold) ≥ 5]. The resolution is limited to 1 event per minute.
CNT
- This is the overall count of activated sensor pixels. Even one high energy photon can activate several pixels which means that there is no direct correlation with the amount of X-Ray or Gamma photons hitting the sensor.
CPM - Counts Per Minute.
EPM - Average Energy Per Minute of the photons hitting the sensor during the measurement cycle. A reading significantly higher (delta ≥ 4) than the threshold value identifies most likely a high energy photon event. EPM readings near the threshold indicate normal sensor noise.
PEM - Peak Energy Per Minute represents the highest value detected by the sensor within the last measurement cycle. A significant threshold delta (≥ 5) identifies an event which will be logged if the EPM criteria is fulfilled.
MCY - The Measurement Cycle is shown by a count down.


Detector Physics & Limitations:

A semiconductor like the CMOS-Sensor in a camera is not just sensitive to photons of visible light but also to high energy photons of X-Ray and Gamma radiation. The picture below shows the Electromagnetic Spectrum and the associated wavelength/frequency of X-Ray and Gamma photons.
The other categories of radioactive radiation namely Alpha [α] (helium nucleus) and Beta [β] (electron / positron) particles cannot be detected because of the material in front of the camera sensor which mostly absorbs them.
A photon will be detected as soon as it reaches and gets absorbed by the sensor. If the energy is to high then the photon passes the sensor without any impact whereas a low energy photon probably doesn't reach the image sensor at all or gets mask by the sensor noise.

 

Example Measurements comparing environmental natural radiation with a weak radioactive mineral:

 

Environmental Measurement (3 Events of cosmic rays, natural Radon, etc.):

Time:                     CNT:                       EPM/PEM:                         Events:
08:23:27                  000                        000/004                          
08:24:27 000 000/004
08:25:27 002 005/005
08:26:27 000 000/004
08:27:27 000 000/004
08:28:27 000 000/004
08:29:27 000 000/004
08:30:27 000 000/004
08:31:27 039 037/144 +
08:32:27 002 005/005
08:33:27 000 000/004
08:34:27 000 000/004
08:35:27 000 000/004
08:36:27 000 000/004
08:37:27 000 000/004
08:38:27 002 007/007
08:39:27 000 000/004
08:40:27 002 007/007
08:41:27 000 000/004
08:42:27 000 000/004
08:43:27 000 000/004
08:44:27 000 000/004
08:45:27 002 007/007
08:46:27 000 000/004
08:47:27 000 000/004
08:48:27 000 000/004
08:49:27 000 000/004
08:50:27 002 007/007
08:51:27 000 000/004
08:52:27 002 007/007
08:53:27 002 007/007
08:54:27 000 000/004
08:55:27 000 000/004
08:56:27 009 010/013 +
08:57:27 000 000/004
08:58:27 000 000/004
08:59:27 002 007/007
09:00:27 004 005/005
09:01:27 040 012/027 +
09:02:27 002 007/007
09:03:27 006 007/007
09:04:27 002 007/007
09:05:27 000 000/004
09:06:27 002 007/007
09:07:27 000 000/004
09:08:27 000 000/004
09:09:27 002 007/007
09:10:27 002 005/005
09:11:27 002 007/007
09:12:27 000 000/004
09:13:27 000 000/004
09:14:27 000 000/004
09:15:27 000 000/004
09:16:27 000 000/004
09:17:27 002 007/007
09:18:27 000 000/004
09:19:27 000 000/004
09:20:27 000 000/004
09:21:27 002 005/005
09:22:27 000 000/004
09:23:27 000 000/004



Weak radioactive mineral directly positioned above the camera lens (12 Events):

Time:                     CNT:                       EPM/PEM:                         Events:
09:28:12                  000                        000/004                          
09:29:12 046 022/043 +
09:30:12 000 000/004
09:31:12 000 000/004
09:32:12 007 014/023 +
09:33:12 045 044/159 +
09:34:12 000 000/004
09:35:12 001 005/005
09:36:12 000 000/004
09:37:12 015 014/026 +
09:38:12 000 000/004
09:39:12 000 000/004
09:40:12 008 013/035 +
09:41:12 000 000/004
09:42:12 000 000/004
09:43:12 002 007/007
09:44:12 000 000/004
09:45:12 000 000/004
09:46:12 000 000/004
09:47:12 015 010/020 +
09:48:12 000 000/004
09:49:12 000 000/004
09:50:12 002 005/005
09:51:12 006 011/025 +
09:52:12 012 008/015
09:53:12 036 016/049 +
09:54:12 000 000/004
09:55:12 000 000/004
09:56:12 002 009/009
09:57:12 000 000/004
09:58:12 002 007/007
09:59:12 000 000/004
10:00:12 000 000/004
10:01:12 000 000/004
10:02:12 002 007/007
10:03:12 004 007/007
10:04:12 003 006/006
10:05:12 000 000/004
10:06:12 000 000/004
10:07:12 002 007/007
10:08:12 000 000/004
10:09:12 021 018/048 +
10:10:12 002 007/007
10:11:12 000 000/004
10:12:12 000 000/004
10:13:12 000 000/004
10:14:12 000 000/004
10:15:12 002 007/007
10:16:12 002 014/014 +
10:17:12 000 000/004
10:18:12 000 000/004
10:19:12 000 000/004
10:20:12 000 000/004
10:21:12 002 005/005
10:22:12 000 000/004
10:23:12 003 007/009
10:24:12 012 016/023 +
10:25:12 053 034/134 +
10:26:12 000 000/004
10:27:12 002 007/007
10:28:12 008 006/009
10:29:12 000 000/004


Disclaimer:

This Software is provided "as-is", without any express or implied warranty.
In no event will the author be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software except for commercial use.
Please contact me if there is a wish for a commercial implementation.