Table 2. Computed scattered photons under measurement conditions for various device components and other potential sources of background scattering.

Material	Thickness	Energy (keV)	Total scattered photons at 1 mJ pulse−1
Graphene	8 layers	7.5	1.0 × 105
PMMA	80 nm	7.5	1.8 × 106
Water	1 µm	7.5	7.8 × 106
	20 µm	7.5	1.6 × 108
	1 µm	9.5	6.6 × 106
Water vapor at 100% humidity at 20°C in He	1 cm	9.5	2.6 × 108
He at 20°C	1 cm	9.5	7.2 × 105
Mylar	5 µm	7.5	1.4 × 108