TABLE I.

Apertures and beam properties available at the NIST neutron imaging facility. Apertures with only one dimension listed are circular and the dimension is the diameter; the apertures with two dimensions listed are slits.

Aperture dimension	≈ L/D (x,y)	Fluence Rate (cm−2 s−1)
20 mm	300	3.3 × 107
15 mm	450	1.4 × 107
10 mm	600	5.0 × 106
3 mm	2000	5.2 × 105
10 mm × 1 mm	600, 6000	7.5 × 105
1 mm × 10 mm	6000, 600	8.0 × 105
20 mm × 2 mm	300, 3000	3.2 × 106
2 mm × 20 mm	3000, 300	3.4 × 106