Michael Foster wrote: > > > Fred wrote: > > > Astute calculations show that dissociation > > of an Iodine molecule at the filament, with > > uptake and subsequent discharge of an > > electron attached to an Iodine atom > > at the bulb (internal) reflector coating could > > yield up to 20 amperes at ~ 0.5 volts from > > the 12 watts of solar energy focused on > > filament of 1 square cm area. > > But here's the problem. The quartz halogen bulbs > are usually small quartz tubes isolated from the > reflectors, A PAR (PARABOLIC ALUMINIZED REFLECTOR) Tungsten-Iodine flood lamp has the filament exposed to the iodine atmosphere. I used a millitorr for the calculations.
> as opposed to something like the heat > lamp you tried where there is a partial vacuum within > the entire bulb including the outer envelope and the reflector. > Correct. I used that "flood type" heat lamp to see if I could get the filament to warm up some. > Usually, such bulbs have no halogens, but > are simply argon filled at low pressure. > Of Course. > > You wouldn't want to use a floodlamp anyway, because > by definition, their reflectors are not parabolic, > Go back. > > Please pardon me for being excessively punctilious > about this, but I've actually played around with this > basic idea for years. However, I never thought of a > Langmuir type dissociation, but was merely entranced > with the idea of solar driven vacuum tube thermo- > electricity. I have in fact used old radio amplifier > vacuum tubes, externally heating the filaments with > focused sunlight. This produced encouraging but not > useful results. The filaments are never really the right > shape to get the desired concentration. Ditto lightbulbs. > Right. But, the principle stands, and can be applied to the right emitter configuration. > > You would probably need a custom built tube to take > advantage of the effect you would like to demonstrate. > Or put a tungsten plate in a millitorr of iodine vapor, and a collector plate, and use your Fresnel concentrator on it. > > It wouldn't be a bad idea to resurrect Philo Farnsworth > and ask him how to do it. > Not practical. > >The guy probably knew more > about the practical aspects of vacuum tube thermo- > electrics than anyone before or since. Anyone out > there channeling Philo? ;-) > > Here's an odd possibility, though. If you want to try > to extract a charge from the internal reflector, you > could try attaching aluminum foil to the outside of the > bulb and then vary the exposure to sunlight. This > would give a time varying charge to the reflector and > then the capacitive coupling the external foil might > result in an accessible AC current. Just a thought. > Sounds reasonable, but, for minimal effort I only do thought experiments. Frederick > M. > > > > > > > > _______________________________________________ > Join Excite! - http://www.excite.com > The most personalized portal on the Web! >
