kf_sphere_proj

[abuts]

If one have a look at inelastic stattering signal in direct (rather than reciprocal) coordinate system, one can see clear elastic line signal at low energy transfer range. The signal can be easily approximated by double-side exponential function (see fig.2).

fig.1

fig.2

The coordinates of axis in fig 1 are X-axis -- dE, Y-axis -- roughly proportional to scattering angle $\theta$ in direct coordinate system.

There are currently no way to produce such image in Horace, as $\|Q\|$ along Y-axis changes from 0 to $2|k_i|$.

Similar image may be produced using $\vec{k_f}$ coordinates, namely $\vec{k_f}=\vec{Q}-\vec{k_i}$

This is the ticket to build spherical projection which would produce Horace image in $\vec{k_f}$ coordinates, namely $\|k_f\|$, $\theta$, $\phi$ coordinates where $\theta$, is the angle between beam and $\vec{k_f}$ directions.