Table 2.

Peak neutron doses for hybrid brass/plastic collimators with overall thickness sufficient to stop 235 MeV protons. The geometry used here (figure 1, no pre-collimator) is identical to those for the calculations shown in figure 3. Typical statistical uncertainties (1σ) in the results, related to the Monte-Carlo simulation, are ±0.3%.

Brass thickness (mm)	Plastic thickness (mm)	Total collimator thickness (mm)	Collimator-related peak neutron dose (pGy/incident proton)
65	0	65	0.36
55	25	80	0.29
50	41	91	0.25
45	59	104	0.22
40	75	115	0.20
35	94	129	0.18
25	128	153	0.17
0	195	195	0.16