I?ve been looking at these forums for ages and never once stumbled into the sci-fi section boy have I have been missing out.

There is an additional advantage's to using a laser over a kinetic energy weapon. High intensity plasma windows would vaporise any conceivable conventional KE round, where as a photon based weapon will be unaffected, unless the KE round was formed from degenerate matter (or something even crasier, like a singularity) which does not lose structural integrity regardless of temperature.

While admittedly being to lazy to bother drawing a graph of Uranium?s depletion vs velocity of round on a set high temperature plasma window at fixed width, even typical ?weak? windows used today run at about 15,000k is still enough to vaporise diamond given time. If you make sure the object you are protecting is effectively shielded and far away for the window, thee is no real reason why you couldn?t make it million of even billions of degrees Kelvin, Alternatively you could simply layer multiply windows one after the other. To be honest I was more intending the ?plasma window vs KE application? to take place in a vacuum i.e. space much like where lasers will themselves will shine without much of there atmospheric problems (such as energy loss through heat)

Basically, despite being unsure of how best to weaponise plasma windows I would be surprised if they weren?t in time. When they are utilised at extreme temperatures only objects with extreme density or high relativistic velocities (which by default become extreme densities if travelling fast enough due to the relativistic mass increases) will survive comparatively intact. There?s not a great deal denser than Uranium that we can effectively use and its huge jump between that and degenerate matter.

To put it more generalised:

As energy output increases and technology improves we will increasingly see more electromagnetic weapons/defences. Photons are charge neutral in addition to being massless, they are unaffected by these effects.

Other than this, photons (massless particles) real advantage is its absolute speed advantage and infinite acceleration, which can only really be counter with armour or precognition of the event.

This answer was a bit fuzzy but never mind, it?s past 3am and I?ve consumed 7 cans of Lager, so cut me some slack.

Plasma windows are already built at sufficiently high temperature to damage any man made object. If I were to use exotic materials like metallic hydrogen at extremely high pressure as the superconductor for the electron flow to generate the electromagnetic field, you could build a plasma field in excess of 100,000s of Kelvin which would not ?melt? under its own temperature. You get some of these odd effects round neutron stars, at billions of Kelvin. There is also nothing stopping you from layering ?weak? ones, one after the other, or simply moving the plasma field to the desired location of impact. Would it incinerate its surroundings? Sure it would, but if your in space who cares. There?s no theoretical reason why you can?t use them to hinder KE rounds as long as you can maintain the high energy requirement, you don?t even have to completely vaporise the round merely weakening its structure, combined with good old fashion dense armour may be enough.

I?m going to leave it to the engineers to work out the most appropriate way of weaponising a plasma window. As another poster has already commented it might not be used ?defensively? but to shield a high yield weapon.