How to render volume as image with alpha background?

Support Lighting and Rendering
1

I have a problem when I render this (using f12 ) node tree on my object in blender cycle I get nothing I tried to render another things and I get a results but with this node tree in my screen shot I get nothing
in render mode

when i click f12

my node tree and my transparent option

2

Why do you use the same output as both the fac and the emission strength ?
Can we see the outliner and properties window ? Or even get the blend file ?