Re: Ionization at 80 eV?

["Mike Malaxos" <rss@arach.net.au>]

Even though x-radiation can be produced at very low energies. For
protection purposes energies less than 5 keV can not penetrate the vacuum
container wall unless a special low absorbtion (ie one micron Be) window is
incorporated. Therefore they can be neglected???. Is this a fair
assumption.?

M.Malaxos
Radiation Safety Services
Fax 61 294 1533
email rss@arach.net.au
 


---------
> From: Pickett, Bruce D <Bruce.Pickett@PSS.Boeing.com>
> To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject: Ionization at 80 eV?
> Date: Saturday, 17 May 1997 3:39
> 
> >Someone called our office with questions about the safety of a device
they
> >are using. Apparently, this is some type of a mass spec device that is
used
> >as a helium leak detector, and which has an electrical potential across
a
> >cathode and anode. We were told that the "amount of radiation produced
is 80
> >electron volts of ionized radiation"; we don't know if this information
comes
> >from a label on the device, or the operator's manual, or somewhere else.
> >
> >In talking this over in our office here, we're not certain that
ionization
> >would even occur at such a low potential as 80 eV (we're normally
working
> >with thousands to hundreds of thousands of times this potential).
However, we
> >do agree that even if ionization does occur, any resulting x-rays would
be so
> >soft that they would be stopped by a small amount of air, so our
conclusion,
> >based on the little we know of this device, is that there would be no
> >ionizing radiation hazard associated with its use.
> >
> >Now, in order to satiate our curiosity, can anyone on RADSAFE tell us
what
> >the lowest electrical potential would be that would result in ionization
and
> >the formation of x-rays. I presume that we would need to known the
ionization
> >potential of the materials in the device's anode, but knowing almost
nothing
> >of the device itself, we could only guess at what this would be made of.
> >
> >Bruce Pickett
> >Radiation Health Protection
> >The Boeing Company
> >PO Box 3707 M/S 6Y-38
> >Seattle, WA  98124
> >(425)393-3098, FAX (425)393-3060
> >bruce.d.pickett@boeing.com
> >
> >
> >
> >
> >