Hello:
Just for fun check this little $1200 gadget, the end result is quite impressive, this device is what gave me the idea to pack an "improved" version into an Altoids can. 1 uR/ Hr sensitivity is pretty good. Reference BGO: Yes it can work with silicon devices, but you end up with 25% (or less) of the total sensitivity, when compared to the longer 550nm wavelength of CsI(Tl), and especially when considering the much higher total scintillation efficiency of CsI(Tl), it just looks better. I started with the idea of using the Ebay BGO product, but after doing some research I was sold on CsI(TL) big time. CsI(Tl) scintillator is also not hygroscopic, and fragile like its NaI(Tl) cousin, and it is almost "plastic" in nature, with no fracture problems, real tuff stuff. Yes you have to keep it out of water, or direct condensation, but with our vacuum experience, sealing it would be simple for us, plus it already comes sealed in Al, or even Be with a glass or sapphire window, in a 1cm, and 1.8cm size from China. St. Gobain also uses it in their extreme condition probes, which are designed to go down hot bore holes on oil rigs, it is also the scintillator of choice in solid state surgical gamma probes.
The posted Perkin Elmer product link has my full attention for the time being.
Reverse engineering of a successful commercial product is sometimes a nice starting point, because it often saves you from having to re invent the wheel so to speak. Below are the specs for the unit which I thought represented a good starting point. I think the detector /scintillator setup in it is pretty good and reasonably well engineered, the improvement I think would be in making the readout more useful for folks like us, who enjoy the science portion a little more
[i]Gamma Radiation Detector & Dosimeter in One
* Overview
* Features
* Specs
* Applications
* Downloads
The GammaRAE II R is a gamma radiation detector and full-range dosimeter in a single instrument. Designed specifically to meet the needs of first responders, it has the rapid response of a detector and the accurate dose measurement of a dosimeter.
Key Features
* Sensitive CsI scintillator for excellent search capability and fast response
* Energy-compensated PIN diode sensor for high dose rate range and accurate dosimeter capabilities
* Prominent visible, audible and vibration alarms
* Alerts first responders to radioactive threats
* Accurately measures accumulated dose to the wearer
* Immersible in water for easy decontamination
* Top-mounted, invertable display
* Continuous digital readout in Rem/hour (μR/h & mR/h) or in Sievert/hour (μSv/h & mSv/h) and counts per second (cps)
* Two operation keys, simple intuitive programming
* Long calibration life
* Two AA Alkaline batteries last up to 600 hours
* Large, 30,000-point datalog capacity, downloaded via cable-free Bluetooth® connection
Sensor
Radiation Sensors 3cc CsI (TI) with Photodiode (Low channel) Energy-Compensated PIN Diode (High channel)
Energy Range 0.06 to 3.0 MeV
Dose Equivalent Rate (DER) Range for 137Cs 1 μR/h to 600 R/h (0.01 μSv/h to 6 Sv/h)
Accuracy of DER ±20%
Dosage Range 1 μR to 999.9 R (0.01 μSv to 9.9 Sv)
Background Reference Background level reference set automatically on start-up (Search Mode only), plus user-initiated as needed
Calibration None required. Periodic functional test recommended using 1 μCi and 16 μCi 137Cs check sources. Factory calibration available if needed.
Not bad ehhh.....Now a built in CdTe spectrometer, now that would make a cool addition as well. I did also find some interesting references to the new SiPMT technology, which is a silicon device operating in a high revers bias Geiger mode. In a nutshell I just have a feeling that there is some real interesting new stuff out there in the silicon world, but we do not see it as much because we are wearing our familiar PMT colored glasses. LaBr3 is real cool also with 2 x the resolution of NaI(Tl) for spectroscopy, sadly for good SS efficiency it would need to be shifted to something longer than 380nm, plus try to get some LaBR3? So what do you guys think, not interested? or worth at least talking about? No worries, my ego is not in this so if it does not generate any interest, then it was simply not meant to be. Take care......Lutz