Table 2.

Left column: main parameters relevant for the operating regime of the X-ray source; the electron bunch and scattering laser pulse figures were used as input of the Thomson scattering simulation code TSST.

Thomson scattering X-ray source parameters		Imaging simulation parameters
Electron bunch		SAD	1000 mm
Size	2 μm × 2 μm (tr), 3 μm (long)	ADD	1500 mm
Divergence	10 mrad	Magnification	2.5
Bunch charge	100 pC	Detector size (transverse × axial)	50 × 25 mm2
Mean energy	$~50\mathrm{MeV}$	Detector pixel size	250 μm
Energy spread	$\lesssim \mathrm{20\%}$ rms	X-ray pulse duration	0
Scattering laser pulse		Total n. of X-ray pulses (for the entire 4D reconstruction)	6000 to 24000
Duration	500 fs (chirped)	Unattenuated no. photons per 250 μm pixel	5000
Energy	1J	Unattenuated no. photons per 50 μm pixel	200
Central wavelength	800 nm	Size of the cubic voxel in tomographic reconstructions	100 μm
Spot size	20 μm
a 0	~0.24
X-ray source
Duration	$~10\mathrm{fs}$
Source transverse size	2 μm × 2 μm
No. of photons within 10 mrad per laser shot	$~9.8\times {10}^7$

More parameters related to a possible LWFA regime able to provide the required electron bunch are given in the Supplementary Materials. Right column: parameters of the numerical simulation with the 4D mouse chest phantom (SAD: Source to axis distance; ADD: Axis to detector distance).