Please ponder the following "beta-decay" reaction:

 

[math]p^{+} + \bar{\nu}_e \rightarrow n^0 + e^{+}[/math]

So, if you propelled a powerful beam, of anti-neutrinos [math]\bar{\nu}_e[/math], into a star, then would you convert protons to neutrons?

 

And, then, would those neutrons not fuse, with remaining protons, ultimately into helium nuclei??

 

So, could you not "stimulate" fusion, inside stars, and produce powerful "pulses" of helium production, i.e. generating an artificially-induced super-novae explosion (possibly powered by positron-electron annihilations too) ??

Quantitatively it is impossible.

 

The sun itself is producing far more neutrinos than anything that could ever be made by ordinary mortals. Furthermore most of them pass right through the sun without interacting.