Yeah, I think I am going to do some research also....The thing that caught my attention is the spectral out put of the plasma..In theory, it should be very close to the sun, at least that is how I understand it...Let me know if you find some good info on the topic...
Before you go becoming a devotee of full spectrum lamps, think about this; cannabis is responsive to light of differing bands of colour in different phases of growth. It is most reactive to a bluish spectrum in veg, but a red-orange spectrum in flower. The reason for this is that the angle of the sun is high in the sky in spring and summer, passing through a comparatively short path through the atmosphere compared to autumn. The short path filters less blue than the long path late in the season. Autumn sunlight is decidedly more yellow-red in the latitudes indigenous to cannabis. The red-yellow light light colour prominence is a co-trigger for flowering along with the shorter photoperiod (day length).
While you can only do this in a grow room, you'll find the plant produces a slightly different habit with the differing light colours, independent of the photoperiod. If you veg with HPS, plants will be somewhat elongated compared to the more bluish MH, which will produce shorter internodal lengths and denser vegetative growth. Buds flowered under MH tend to be somewhat more leafy than those raised under HPS. Vegging with MH and flowering with HPS are the normal usages as these colours best complement the phase of growth.
However, cannabis does not need the
full spectrum at any single time in growth. If a lamp produces light that can't be used, it's wasted. Moreover, if a lamp produces a broad spectral output, its overall intensity will be lower for a given power input.
This more-is-less is the case with Ceramic Metal Halide lamps, which produce a very broad spectrum but only 40K lumens for a 400, compared to 56K lumens for the ordinary 400HPS. CMH is being trialled by a number of growers at the moment, but it's been around since 1994. CMH is supposed to make a lot less heat output than HPS or MH and runs on HPS control gear. However, remember that it's luminous intensity which drives photosynthesis, not light colour, so at the end of the day, it's only 102 lumens/watt, wasting light in bands not used by the plant. Dramatically reducing thermal load on the grow op can be done with cooltubes- a 'tubed 400 HPS will be cooler than a naked 400CMH, so lower heat output lighting, while nice, isn't all that important.
HPS and MH produce greater luminous intensity because they don't attempt to generate light across a full spectrum, rather concentrating the output in certain frequency bands- coincidentally, those which cannabis likes best at particular stages of growth.