Re: Radiation Generating Devices

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>A colleague of mine had a question involving rad controls for Radiation 
>>Generating Devices.  She is currently requiring 'radiological controls' 
>>for X-ray RGDs with max accelerating potentials of 5keV and above.  The 
>>scope of the 'rad controls' is dependent on safety features built into the 
>>device. 

>>Does anyone out there use a similar energy dependent screen for evaluating
>>the hazards from these devices?

At LBNL I wrote into the scope of the x-ray regulations a definition of an 
x-ray machine as "Designed to emit x-rays beyond a contiguous vacuum".  This 
lets off ESCA machines and electron microscopes and well as ALL VDTs.  These 
are just NOT a problem.  (even our HVEMs - 1.5 and 3 meV - are NOT a 
problem!).

This lets off most devices not generally thought of as x-ray machines.

Anything else that happens to generate x-rays is a miscellaneous emitter - 
HV power supplies/assemblies/devices, micro-mave cavities, and hi-potters 
(when used in a vacuum) - and handled on a case by case basis (usually 
shielded enough to NOT be a problem and with labels warning about removing 
shielding.  NOTE this is a considerable simplification of consideration 
involved and actions taken - but sufficient for a capsule description 
appropriate to this forum.

While I did not define a specific energy threshold - I GENERALLY consider 
about 15 keV to be the bottom limit UNLESS high beam currents (amps) are 
involved.

I think 5 keV is a bit low since it catches all B&W and Color TV sets and 
monitors!!! (except LCD).

At least at 15 keV I rule out most B&W TV's!!

If one thinks about it it SHOULD be possible to come up with a reasonably 
intelligent kV/current threshold - and that would be the current limit of 
the power supply and NOT what the device "normally" draws.