Methods of Radiation Detection - Atoms, Radiation, and-Radiation Protection - page 238

Fig. 10.1 (a) Monoenergetic beam of particles stopping in
parallel-plate ionization chamber with variable potential
difference V applied across plates P 1 and P 2 (seen edge on).
(b) Plot of current I vs. V .

e ˙

AE
W .

Ne ˙ (10.1) I 0 = A =

It follows that

I 0 W
eA ,

˙

= ˙ E =

(10.2)

showing that the beam intensity is proportional to the saturation current.
The important relationship (10.2) is of limited use, because it applies to a uni-
form, parallel beam of radiation. However, since the rate of total energy absorption
in the chamber gas, E abs ,isgivenby E abs = ˙

A , we can write in place of Eq. (10.2)

I 0 W
e

E abs =

.

(10.3)