Re: Unsafe High School Science Project

["Frank R. Borger_(FRB)" <frb@gammex.com>]

>>> "William G. Nabor" <wgnabor@uci.edu> April 13, 2000 11:52 >>>
Dear RADSAFER's:
<snip>
>The project was a home-made X-ray machine constructed by a 15
>year-old high school student in the following manner:  The power
>supply was a 12 volt DC 10 amp commercial automobile battery
>charger, the output from which was connected to a vibrator.  No,
>not that kind of vibrator.  This one was a voltage booster. 

Sounds like the old Ford model T spark coils, worked kind of like a
Tesla coil, but without the resonance. 

>The negative output lead from the vibrator was connected to the base of
>an ordinary incandescent lightbulb.  The positive lead was
>connected to the tip if the glass globe under several layers of
>aluminum foil, uncalibrated eyeball estimate 1mm thick.  The
>student _claimed_ that she used a "geiger counter" to measure the
>output from this device and got a 300 to 1000 mR/hr dose rate.

Considering a SWAG of 15kV from the coil, 1mA or so from the
spark coil, and lowZ aluminum foil, (outside the glass which would be
an insulator,) I seriously doubt there was any radiation at all.

What she probably saw was the meter responding to the large
amount of RF radiation generated by the spark coil. Lots of people
have been fooled by that. I'm surprised she didn't have the FCC 
descending on her house.

>Our safety concerns are three:  First, the electrical safety, of
>which there was none.  With the exception of the power cord to the
>commercial battery charger every connection was bare.  Alligator
>clips, aluminum foil, bare wires, even the connections to the
>lightbulb and the 120 volt AC mains, all were fully exposed.  This
>represents a potentially lethal and fully unacceptable situation
>which we will communicate to the teacher.

I hope the communication consists of the proverbial "Slap up side the head."
I wouldn't want my children anywhere near a teacher that couldn't recognize
the electrical hazard. Where do we get these _educators_? ...sigh

<snip>  
>   1)  Remembering that the target is thin glass and about 1mm of
>Al, and that the positive lead is connected to the outside of the
>glass globe, how likely do you think it that this device could
>produce X-rays or beta rays?
>   2)  If it can produce ionizing radiation, how likely is it that
>it can produce 300 to 1000 mR/hr?  We were not about to suggest
>that she turn it on in the exhibition hall so we could take
>measurements!

See above. Also remember that the bulb has an inert gas, not vacuum.



Frank R. Borger - SeniorSupport Engineer, Gammex RMI
fborger@gammex.com phn 608-828-7289 fax 608-828-7500

Oh NO!!! Captain America's traded in his T28 for a Rooski Jet!
Say it isn't so, Gail Richards!


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