Thanks all.? I do like the Alan Wood site and am very glad it is there.
Longstanding mystery is mostly resolved.?The decreased energy dissipation in
each tube results in less
efficient conversion to light somewhat analogous to two 50W bulbs producing
fewer lumens than one 100W bulb.? Had no clue the T28 heads were in series or
that more energy was left in the capacitors.? Presumptively this energy is
available for the next discharge.
In retrospect did not make sense that it would be beneficial to independently
power each head to increase the? GN by sqrt 2.? Probably more power than
typically necessary except would be nice for cross pol use.
I may try using one T28 head and a T32.? A T20 and T32 sometimes is not quite
enough.
Mike
In theory the same energy spread between two tubes should give identical total
light output as the
same energy dissipated in only one tube.
However, two things reduce this :
1) the reduced energy dissipated in each flash tube, reduces the peak
temperature of the tube
plasma. The light conversion efficiency is higher with the higher temepratures
in a single tube.
(It is a little more complex, because it depends on what is actually produced
in the visible
spectrum.)
2) the tubes are in series in the T28 (see schematic on Marks Website), so
voltage acrosss each
tube is reduced ~1/2 of single tube.
Since the capacitor does not discharge to zero but to the extinction voltage of
the tube (volt =
~60V) then with two tubes in series there is quite a bit more energy left in
the capacitor (volt=
~120V) after flash completes. (a factor of 2^2 - 1 = 3x more wasted) This is
increased wasted
energy, unsued at end of flash.
Tim Hughes
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