[ RadSafe ] Skyshine measurements
Ted de Castro
tdc at xrayted.com
Wed Mar 6 20:38:34 CST 2013
Sounds like lots of very expensive instrumentation!
I set up an active area monitoring network at Lawrence Berkeley
Laboratory many years ago - maybe you were at the San Jose mid year some
time ago and heard my paper on it. My work was basically an improvement
on a system started by Lloyd Stephens there in 1963.
In any event - it uses cheaper, simpler and very reliable
instrumentation to good effect: A 1 inch dia by 12 inch long energy
compensated GM and a Hankins Modified, high energy modified moderated
He3 detector. The system runs reliably for years on end and is
sensitive enough to clearly show variations in background radiation - be
it seasonal or even when its raining! The system integrates data in 10
minute intervals - this allows tracking changes with changes in
accelerator operations - either by comparison to accelerator running
logs and/or by comparing readings from local instruments with those from
the perimeter instruments on the network.
Using this I've been able to characterize things like perimeter
contributions from the ALS accelerator during fill as opposed to normal
running conditions. Never got around to writing that up as a paper -
just an internal note.
These instruments would certainly be able to characterize the fields
discussed in this thread under the various conditions mentioned as a
temporary set-up and probably even be of use as a permanently installed
monitoring system (not requiring the high energy neutron configuration -
On 3/6/2013 10:40 AM, JPreisig at aol.com wrote:
> Dear Radsafe,
> Skyshine is discussed in Patterson and Thomas's Accelerator Health
> Physics and/or
> Cossairt's Course notes on Accelerator Health Physics.
> Guess other Radsafers have commented on the meteorology of skyshine
> For field measurements of Skyshine, perhaps use a portable MCA
> counting system with NaI or Ge
> detector, or whatever you have available. If there is a neutron
> component, you can make flux density
> spectra measurements with a set of Bonner Spheres and one or two LiI(Eu)
> detectors. Hopefully
> reactor neutron and/or photon/gamma signals are not highly variable in
> time, so you don't need
> 7 LiI(Eu) detectors, just one or two. Bonner Spheres (polyethylene) are
> fairly expensive. You can analyze Bonner data with BON4/BON5, LOUHI???,
> MAXED??? or other unfolding codes available from
> RSICC (Radiation Shielding Information Center at ORNL). If you end up
> using an Anderson-Braun
> detector only, maybe you would want to make a set of measurements as a
> function of angle (measured
> from horizontal) pointed up towards the sky.
> Like the other guy said, you can mathematically model the problem
> using MCNP (Monte Carlo
> Neutral Particle Program). MCNPX can be used for high energy
> neutron/hadron transport, but that may
> not be necessary in this case.
> Have fun. Regards, Joseph R. (Joe) Preisig
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