If you add in the green line overall power can take a dive by design in order to prevent power shifts between lines. A Krypton head can oscillate between the 568 and 530 nm lines, as they share the same upper state. Yes, they do exist, the optic part number is a internal MG item, there are however head part numbers for RGB NO Yellow in the manual... In a Krypton, 647 Red and Yellow can oscillate back and forth with changes in alignment, pressure, and magnetic field. In a short tube 568 nm Yellow and 530 Green can also oscillate back and forth in power under certain circumstances...
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In a large frame this can be of little consequence, in a short, very hot, air cooled resonator that is always slightly changing in length, it can get quite noticeable, unless you adjust the fill pressure to favor one side of the gain curves.
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Hence RGBY would be a special order, likely designed with reduced power (Change in OC transmission vs wavelength, or change in fill pressure or gas ratio) in order to have stability.. From a system designer's point of view, killing either green or yellow by adjusting the OC transmittance curve made sense. You usually will find that MG broad spectrum products ship with a 400-700 nm HR, so you need a new OC. However they are scarce. I have used them.
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As most biology applications do not need the green, RYB became a standard item, and is a reasonably stable combination in a short tube.
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Sam Goldwasser may have a few of the RGB or RYGB optics, however without a spectrophotometer, he may have a hard time recognizing what is what. Mine (RYGB) is not for sale at this time.
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If you look at the IVP-RYB table on page 12 of this patent, you can understand that getting a balanced output from a small tube is difficult. Having helped a friend repump a few 543s to make 643s with a whitelight mix, I can tell you that getting a stable 643 with good color balance is exceptionally tricky. In fact I'd wager that there are internal gas flow design differences between a 543 and a 643 series tube, although externally they can look identical.
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Good color balance in a mid frame tube is say 15% argon, Good color balance in a very short tube may approach 30-40% Argon.
~ See US PAT 214658 By Ostler. Incidentally, the two tables presented are for two different tube lengths. When they wrote that patent they were not interesting in "Giving away the farm" with all the details.
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Steve
Last edited by mixedgas; 02-14-2017 at 06:49.
Qui habet Christos, habet Vitam!
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When I still could have...