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AW: X-ray dose
According to ICRP 33 60 kV and Filtration 1 mm Be will give a doserate of 90 mGy.mē/(mA.min). You must measure the distance from the Focus (there should be a point on the tubehouse) and not from the window.
3mA during 1 s will give (90/60).3 = 45 mGy in a distance of 1 m.
Check the Filtration of the tube and calibrate Your TLD with an ionchamber.
Herwig from sunny Salzburg
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Von: D J Hornsey
Gesendet: Donnerstag, 23. September 1999 12:28
An: Multiple recipients of list
Betreff: X-ray dose
Dear Radsafers,
I wonder if some of you could suggest an explanation for the
following problem I have. It concerns the considerable differences I am
finding between the expected and measured dose in the main beam of an
X-ray source.
The tube is running at 60 kV with a tube current of 3 mA.
The filtration is 1 mm Be. According to my calculations, at 17cm from
the window, the dose should be 170 cGy (170 rads) for a 10 sec exposure.
A TLD in the main beam consistently records a factor of about 10x less
i.e. 140 mGy (14 rads). A series of measurements under different
conditions reproduces this factor of a 10x inconsistency. Would this be
expected? Should I not be using a TLD for this type of measurement and if
not, what should I be using?
Any suggestions will be most welcome.
David Hornsey
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