FLUKA simulations for the X17 test measurement

Target setup

target setup matrix
shape	cylinder
material	ERGAL (5.85% Zn, 2.3% Mg, 1.4% Cu, 90.45% Al)
thickness	0.8 and 1.4 mm
diameter ⌀	1 inch
length	20 cm
gas pressure (He-3)	300 atm
scoring	plane, 20 cm wide (x-axis), 20 cm long (z-axis), at 10 cm from the beam axis

Setup for the 1-inch target

Electron source

A source of 8 MeV e- placed at the center of the He-3 container (0,0,10) cm. The beam feeds the vertical direction and at 30 degrees with respect to the vertical direction, toward the scoring plane.

sampled hits on the scoring plane

sampled hits on the scoring plane

Beam divergence

⌀ 1 inch, 0.8 mm thickness

angular distribution, FWHM is 16.0 deg

angular distribution with beam incident at 30 deg, FWHM is 17.3 deg

⌀ 1 inch, 1.4 mm thickness

angular distribution, FWHM is 16.7 deg

angular distribution with beam incident at 30 deg, FWHM is 21.9 deg

Summary

target wall thickness [mm]	FWHM [deg]
	beam at 0 deg	beam at 30 deg
0.8	16.0	18.3
1.4	16.7	21.9

No influence of the He-3 gas pressure noted on the beam divergence. At 1 atm pressure and the beam incident at 30 degrees, the FWHM of the angular divergence is 21.6 deg, to be compare with the 21.9 deg of the 300 atm case.