Re: Electron Beam device

["Scott O. Schwahn" <schwahn@CEBAF.GOV>]

At 07:39 PM 10/2/96 -0500, you wrote:
>...The electron energy that the unit is capable of is 200kV at 
>20milliamp.  Safety features include lead shielding,  interlocks to the
reaction 
>chamber and access panels, and a  monitor interlocked to shut down the 
>high voltage and beam if normal background radiation increases.
>
>As we have no experience with this type of device, I am seeking 
>information or advice on performance characteristics or any special
>considerations that may apply to this type of equipment.

Although this is a commercial device, and so p-r-o-b-a-b-l-y has all its
safety features working appropriately, I would highly recommend the
following course of action as a minimum:

1) Ensure there was no damage during shipment.  Especially make sure that
the monitoring device was not damaged and that there are no cracks/gaps in
the shielding.

2) With the high voltage removed from the power source, verify that the
radiation interlock works correctly for a low-energy x-ray or gamma isotopic
source at the desired dose rate cutoff level.

3) Verify that all access interlocks function.

I assume that when you said, "to shut down the high voltage and beam if
normal background radiation increases," you did not really mean normal
background radiation, but ambient radiation levels.  Other than that, just
be aware that 200 kVp electrons produce x-rays with average energy ~2/3 that
energy, so use the appropriate energy check source.  My choice reference for
this type of operation would be:
National Council on Radiation Protection and Measurements, Structural
Shielding and Evaluation for Medical Use of X Rays and Gamma Rays of
Energies up to 10 MeV, NCRP Report No. 49, Washington, D.C., 1976.

I don't know the ICRP equivalent, so that may not be very good for you "down
under."  Good luck.

Scott O. Schwahn, CHP
Accelerator Division, M.S. 12A1
Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue
Newport News, VA 23606
(757)269-7551 (w)
(757)269-7363 (fax)
schwahn@cebaf.gov