Гамма-спектрометр. Demonstration of gamma spectrometer assembly and calibration.


Uploaded by 81lmc7101 on 22.10.2012

Transcript:
In this video I show you scintillation detector for gamma-spectrometry assembly.
It consists of 63 * 63 mm (2.5" * 2.5") Caesium Iodide scintillation crystal, photomultiplier tube,
regulated adjustamble high voltage converter,
low-noise preamplifier and analog-to-digital converter with USB interface.
No special drivers needed for Windows XP or Windows 7.
It is good idea to let detector stabilize for 15-20 minutes after connecting to USB port prior to calibration and any measurement.
We will use freeware program PRA32 for detector signal processing. You can find link to the program in the description of the video.
Now I run the program. First of all I should start "pulse shape acquisition" mode for several seconds.
The program captures pulses and defines coefficients which are needed for signal processing.
Now we will use a caesium-137 activated spark gap for calibration.
Such spark gap can be easily find on Ebay.com for $10-15.
50 years ago it contained 0.9 microcuries of caesium-137.
Now most of caesium-137 decayed and this spark gap contains approximately 0.25 microcuries which is enough for calibration.
Now I put the spark gap close to the detector and start data acquisition in PRA program.
Open amplitude spectrum window and make it bigger for better visibility.
Now we see small peak of Caesium-137.
We have to wait for approximately 20 minutes.
20 minutes passed. We see nice spectrum on the screen.
Now I stop data acquisition process and proceed to energy calibration.
Open settings window and mark "Use energy calibration" checkbox.
Now we need to find centers of main peaks in arbitary units of PRA program.
Main peak (662 kEv) is 28.3 arbitary units.
X-ray peak (31 kEv) is 1.5 arbitary units.
Energy difference between these peaks is 631 kEv.
It corresponds to 26.8 arbitary units.
631 kEv/26.8 arbitary units = 23.54 kEv/arbitary unit.
Now I enter 23.54 kEv\arbitary unit into Settings window and press "apply".
We got X-ray peak at 35 kEv and main peak at 667 kEv.
It's not absolutely correct, so we need to add energy shift in Settings window.
Suitable energy shift is minus 4 kEv. Now I will enter it in Settings window and press "apply" and "save".
Calibration is finished, our system is ready for measurements.
That's all. Thank you for watching.