Use unit.name as key cache

[EdgarGF93]

For two units called scattering_angle_horz and scattering_angle_vert ; the key to cache the arrays is the same for both units (scattering).
Can we change it and use just the full unit.name?

[kif]

If I understand correctly, the issue comes from the _ in your unit name.
If we agree that the second half should never gave a _ as separator, wouldn't it be simpler to use:
space = "_".join(name.split("_")[:-1]))
instead of
space = name.split("_")[0]
This would avoid different behaviour for azimuthal- and fiber- units ?