A CaF2 Mn TLD chip is enclosed in a capsule made of CaF2 Mn

A CaF_2: Mn TLD chip is enclosed in a capsule made of CaF_2: Mn, 0.5 g/cm2 thick, and is given a free-space^60_Co gamma-ray exposure of 2.58 times 10^-2 C/kg. The chip thickness is 0.90 mm in the radiation direction. You may assume that beta (D/K_4) = 1.003. Calculate the average absorbed dose in the TLD chip. Redo problem 4 with the CaF_2: Mn capsule replaced by an aluminum capsule having the same mass wall thickness. If the TLD chip in problem 4 gave a TL reading of 3.49 times 10^-8 C after the exposure described, what was the value of the dose calibration factor k_Co? The same TLD chip as in problems 4 and 6 is exposed to a beam of 100-keV electrons, resulting in a TL reading of 2.36 times 10^-7 C. What is the average absorbed dose in the whole chip? Assuming that the electrons strike the chip perpendicular to its 3.2 times 3.2-mm flat surface, what is the average dose within only the surface layer of thickness equal to the CSDA range of the electrons? Is this dose still in the linear-response range for CaF_2: Mn? What was the fluence of electrons that struck the chip, assuming back-scattering to be negligible? (Chip mass = 29.3 mg.) Answers 5.69 Gy. 87.9 Gy. Yes. 1.016 times 10^15 e/m^2

Solution

7. (a) average absorbed dose = 1.6 * 10^-14 /2.36 *10^-7

  ^{= 5.69* 10-7 = 5.69 Gy}

(b) average dose =(3.2 * 3.2) *5.69

= 87.9 Gy

(c) this dose is linear

(d) fluence of electrons = 29.3 *10^-3 /1.6 * 10^-19

   = 10¹⁵ e/m²