[Sneap] Active controls to limit current of high energy protons

[jonesn7 at comcast.net]

At the ORNL EN-12, we had rad protection and our safety people supervise a test where we secured the tank room and ran up to different currents and terminal voltages with the beam on the downstream viewer/cup. Rad instruments placed around it were monitored by CCTV. We set the terminal voltage at 3 MV and turned control off with about a micro amp going in (about the best that I could do with a standard TiH source cathode, no gas). The terminal voltage sagged. Then we upped the charge and could only get to about 4 MV as I remember due to the corona probe position, so I had to pull it out. Finally we were up to ~5MV, and still had less than 100 mR total ~1 meter from the cup (downstream). Not a High Rad area, and required intervention to force it up so were permitted to use administrative controls (late 90's) I would think that a lock-out of the corona probe control would have added the necessary engineering controls. We also would not permit deuterium or tritium in the target 
 areas 
except for that contained in NMR probes.

Stay out of the High Voltage,

--
Nathan Jones
jonesn7 at comcast.net
"Love 'em all.... Let God sort 'em 
out!"

 -------------- Original message ----------------------
From: "Doyle, Barney L" <bldoyle at sandia.gov>
> 
> As part of our new Ion Beam Lab (IBL) project at Sandia, a concern is
> being raised that, while we will have adequate rad shielding for nA
> currents of 10MeV protons, how do we prevent someone from increasing the
> current to a uA, and then the shielding is not adequate.  We have the
> same problem in our current lab, and just use administrative controls
> (i.e. the SOP limits the energy of proton beams from the tandem to 4.5
> MeV, and for higher energies, Rad Protection is called in and I have to
> be present).  Does anyone know of active engineering controls that could
> be used for this situation?  Any ideas out there?  This has to be a
> pretty common problem.
> 
> -Barney
> 
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