1) They were creating a plasma from a sheet of boron and sending the protons at that. From the publication: "1 in 300–3,000 protons will be able to induce a p11B fusion reaction".

2) There seems to be a fair but not infinite amount: http://www.rsc.org/periodic-table/element/5/boron. One site listed $500 per 100g.

3) It doesn't seem that such a calculation is readily available. However, now that the physics has been demonstrated, one can start to entertain such questions. Also, we are continually improving the efficiency of our laser sources, so as those improve the energy cost for this setup decreases.

4) Also from the publication: "Although our results are specific to the p11B case, a similar approach could be used to study the reaction of other light isotopes."

Bonus: Actual publication link (I'm not sure if the link is paywalled): http://www.nature.com/ncomms/2013/131008/ncomms3506/full/nco...

2) There is a lot of Boron 11, it makes up 80% of Boron.

3) Yes! You can use this for energy. In fact see my other post - I believe this is the future of fusion. The Boron doesn't need to be a plasma, so you don't need to confine it. You just leave it as a solid and hit it with protons.

4) You can also use Lithium (both isotopes) and Nitrogen (the rare 15 one).

What's more notable is that you can directly convert this to energy - the reaction yields charged particles, which will cut flux and induce current.

Simple compounds of boron used in soapmaking and household cleaning sell for order ~$1 per kg. If you can't make isotopically pure Boron 11 for under $10 per kg in bulk out of such products in far greater quantities than could ever be used in fusion, I would be very surprised.

For perspective, I figured out recently that one 76-oz box of Borax has enough fuel to power 150 average American homes for a year: http://focusfusion.org/index.php/forums/viewthread/1261/

I don't know how much energy is required to isolate Boron-11, but certainly it'd be a lot less than that. Since it's a light element it'll be relatively easy to centrifuge.

Energy output vs energy input in the reactor itself is always the big challenge for fusion. This experiment put more energy in than they got out, just like all other fusion experiments so far.

However, previous papers on boron fusion using petawatt picosecond lasers have estimated a 10,000x energy gain, once we have sufficiently powerful lasers (about an order of magnitude better than we have currently). See the references section here: http://www.climatecolab.org/web/guest/plans/-/plans/contestI...

2) It's a very rare [1] and expensive material, but has lots of awesome properties. There is only a little boron on earth and 63% of that is in Turkey, many have died fighting against outselling it there, but politicians sealed the international deals anyway, that's a widely ignore fact.

It is a low-abundance element in both the solar system and the Earth's crust.

Somebody should invest a lot of money and time into finding synthetic Boron, because I really believe into this technology. Without synthetic Boron, it's a waste of very rare resources that we have on our earth crust.

Side note: Interestingly there was even a "reference" to Boron known as Boronite in Star Trek that could be synthesized into one Omega Molecule that looked like a Fullerene [2]. The Omega molecule was known to be the most powerful substance known to exist.

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[1] http://en.wikipedia.org/wiki/Boron

[2] http://en.wikipedia.org/wiki/Fullerene