Response of RS111 and TLDs to cosmic rays (Was: Dose Rates vs. Altitude)

["Lieskovsky, Miro" <MLieskovsky@nbpower.com>]

RADSAFERS:
  
Little bit more from the days of after the Chernobyl surveys.  The
information given here is in terms of RS111 response (Roeter/Stokes
Ar-filled, pressurised ion chamber), and the units happened to be microR/h.
(BTW, I  calibrated this chamber with a Ra source, thus for terrestrial
gammas the RS111 response was pretty close to the actual exposure rate from
the ambient photons.) 

Do not flame me! I know the exposure is defined for photons in air. 

1)  RS111 cosmic ray response. 

I used the RS111 in a plane. We flew the plane at different heights up to  ~
3000m and confirmed the expected cosmic ray response versus barometric
pressure of this instrument.  The expected data are tabulated in the RS111
manual.  To my knowledge, it is the only product that would provide such a
function.  The thing I remember was a consistent difference of approximately
1microR/h between the predicted and measured values in all elevations.  This
was a pretty good confirmation of the tabulated data. (The 1microR/h
difference was a combination of the instrument's own background, plane's
background, outside air residual contamination, latitude and longitude
factors, solar cycle, etc.) 

 2) TLD cosmic ray response.

The TLDs will respond to the cosmic rays.  We have exposed various TLDs
(LiF, CaF2, CaSO4:Dy, CaSO4:Tm, AlP glass and MgSiO4) at different
elevations.  The components of TLD response were analysed against the
response of the RS111.  We established that the cosmic ray readings of the
TLDs were approximately from 0.75 to 0.85 of the RS111 cosmic rays response.

Yet, interestingly, the environmental TLDs readings are often expressed as
the external gamma doses and do not subtract/correct for the cosmic ray
response.  

Thank you for your attention.
Regards, 

Miroslav Lieskovský 
Health Physicist 
NB POWER - PLGS
P.O. BOX 600
Lepreau, N.B.
Canada, E5J 2S6 
tel. (506) 659 7421
fax. (506) 659 6507
mlieskovsky@nbpower.com <mailto:mlieskovsky@nbpower.com> 






   



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