The influence of shielding reinforcement in a vault with limited dimensions on the neutron dose equivalent in vicinity of medical electron linear accelerator

Figure 1

Figure 2

Figure 3

Neutron dose equivalents in μSv per Gy photon dose in isocenter for all measuring positions and gantry angles 0° and 270°

		Gantry 0°					Gantry 270°
		A	B	C	D	E	A	B	C	D	E
		(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)	(μSv/Gy)
Poje	LR 115	0.04	0.08	10	0.04		0.1	0.17	20	0.13
et al.5	Active detector	0.052	0.1	14.3	0.052
Our		0.008	0.0006	8.2	1.3∙10-12	3297	0.01	0.004	10.3	4.21∙10-11	3333
results	CR-39	(0.0006)	(0.00004)	(0.6)	(7∙10-14)	(264)	(0.008)	(0.0002)	(0.5)	(2∙10-12)	(202)

Total MC calculated neutron fluence in measuring positions A, B, C, D and E for gantry angles 0° and 270°_ Neutron fluence is in number of neutrons per cm2 per electron impinging on target_ Results are normalized to source particle

Measuring position
Gantry angle	A	B	C	D	E
0°	5.6 ∙ 10-13	5.3 ∙ 10-14	3.6 ∙ 10-10	8.4 ∙ 10-24	1.5 ∙ 10-8
270°	6.6 ∙ 10-13	3.4 ∙ 10-14	4.2 ∙ 10-10	1.6 ∙ 10-22	1.5 ∙ 10-8

Calibration coefficients for neutron detector CR-39 for measuring positions C and E for gantry angles 0° and 270°

Position	G 0°	G 270°
	μSv/(track/mm2)	μSv/(track/mm2)
C	6,52	11,20
E	151,61	194,97