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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
PCB oil was the de-facto standard for dental x-ray heads up until the mid 80's. It's nothing to worry about though. Although it does absorb readily through the skin, it is nearly completely inert in the body. Sometimes a "rash" will develop, but that is just oil inside your pores.
Irregardless, you won't need to worry if you don't open up the head.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
That doesn't sound right, as I said earlier, PCB oil was banned in 1979. Do you have any references? I've also opened a few x-ray heads from the early to mid 70s, and all of them contained hydrocarbon oil.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
It was outlawed, but a few manufacturers still put it in there. In fact the head I took apart was filled with a very light PCB oil, and it was made in the mid 80's.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
kanonic wrote ...
GM tubes are unsuitable for X-ray measurement, and have no role in radiography. A calibrated ionization chamber remains the gold standard for X-ray measurement.
Proud Mary. Could you recommend any brands/suppliers. Also, what is your opinion on low dose (not CD) quartz fiber dosimeters.
For want of anything better, military/CD QFDs can be used for direct beam measurement. Those I have seen are scaled up to 200 or 500R i.e. 2 or 5Sv.
There is no reason why a competent constructor cannot build her own ionisation chambers using, for example, die cast aluminium boxes, for parallel plate types, or acrylic tube painted with aquadag for cylindrical "Farmer" types. For any air chamber of given geometry, the dose rate can be calculated from first principles - i.e. 1Gy is the quantity of X-rays that produce ion pairs carrying 1C of charge - which is to say 6.24151 × 10E18 electrons - in 1 kg of pure air. (And there are of course a whole Walpurgisnacht of chamber correction factors to be applied)
As with most hobby interests, you can expect to get more sophisticated equipment as time goes by. As an example, I posted details of my NE Technology 2570/1 Farmer Dosemeter here:
Before that, I was using a Precitron Janus Dual Channel Electrometer, which I now have for back up monitoring.
Safety for yourself and others, and staying well within the rule of law in the jurisdiction in which you live are the bedrock of this particular passtime.
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Help planning an x-ray machine build
