Five-dimensional phase space measurement at the Spallation Neutron Source Beam Test Facility

This data set consists of 285,082 two-dimensional images which collectively describe the five-dimensional phase space distribution \(f(x, x', y, y', w)\) of a 2.5 MeV, -25.6 mA H\(^-\) ion beam in the Spallation Neutron Source Beam Test Facility (SNS-BTF). Here, \(x\) and \(y\) are the transverse positions, \(x' = dx/ds\) and \(y' = dy/ds\) are the transverse slopes, \(s\) is the position along the reference trajectory, and \(w\) is the deviation from the kinetic energy of the synchronous particle.

The measurement plane is located in the medium energy beam transport (MEBT) section of the SNS-BTF, 1.3 meters after a radio-frequency quadrupole (RFQ). The measurement apparatus consists of three transverse slits (one horizontal, two vertical) and a 90-degree dipole bend followed by a fluorescent screen. The horizontal slit selects \(y\); two vertical slits select \(x\) and \(x'\); \(y'\)is a function of \(y\) and the vertical position on the screen, \(w\) is a function of \(x\), \(x'\), and the horizontal position on the screen. Thus, the image on the screen gives the density \(f(y', w)\) within a small three-dimensional region in \(x-x'-y\) space. The five-dimensional density is obtained by scanning the slits in a nested loop.

The data set consists of 285,082 images (20 GB). Jupyter notebooks are included to interpolate the data on a regular grid in five-dimensional phase space, as well as to generate interactive figures. See 'README.md' for instructions. (The interpolated five-dimensional image is also included in a separate folder.)

More information can be found in a publication forthcoming in Physical Review Accelerators and Beams (preprint).