I've had 18 lines out of a customized Air-cooled. We adjusted the Ar/KR ratio and pressure for maximum color. Not maximum power, or best color balance, that is a different thing.
I'm assuming from your other posts, you have a 643 or similar Air Cooled.
Different gas mixture ratios support different lines. Just because you have a mix, does not mean you'll get everything that can theoretically lase. This is tuned at the factory.
If you have an Omnichrome 643, generally if it has mixed gas or krypton in it, it usually ships with an "All Lines" rear mirror that covers violet through deep red. Argon only models get a Argon Lines Only HR.
Now for the bad news, the "All Lines/Whitelight " OC is exceptionally rare. Here is why. The 568 Yellow and 647 Red compete with each other for power. The Red/Yellow ratio is dependent on tube pressure, cataphoresis, operational current, gas ratio and magnetic field. Especially magnetic field. While the 643 does not have a field electromagnet, it very much has cataphoresis. So the arc causes the krypton and argon to want to separate from each other, and this does weird things when the heavier atom is slower to pass down the internal gas returns. Cataphoresis driven gas pumping happens in all gas lasers to some extent. It is not unusual for a mixed gas laser to be very sensitive and shift the yellow/red ratio back and forth. Which is why early laser show ion lasers had variable magnet current to tune the field. A second very weak yellow is often available at 575 nm that does not compete like 568 nm does with 647.
Short story, very few Biological customers want green, as it causes cross talk in DNA scanners, Confocal Microscopes, and Cell Sorters. So most optics out there are "kill green" by having extra transmission in the coating at 515-532 nm. That dispatches the unwanted lasing. A secondary reason is the 530 nm KR line steals energy from two other lines, one of which, if I remember right, is the yellow.
I have a chart of the optics groupings some place. If you can find a dead prism tunable RYGB 643 head, guess what the OC is! There are a few all lines systems out there, but the main customer for mixed lasers, Biological Imaging, did NOT want either the power ratio issue or green light to mask their desired signals. if its stained or dyed biological tissue, odds are the primary fluorescence is blue for nuclei (DAPI dye) or green or yellow (TRITC dye ) for everything else like cell walls. We use DAPI and TRITC at work, and any stray green light kills the experiment in our case.
I'll find the model chart.
I do have about 70 pieces of used, old 15 mm small, medium , and large frame Whitelight Optics, but you use a 0.25" / 7 mm optic if I'm correct. My bet is I may have a older large frame all lines HR that leaks enough for you to have some fun. Small and mediumframe HRs don't leak much , but the tailored coatings on large frame HR optics often leak @ say 0.25%. I don't know why, but they do.
Yes, the super magnet trick has been done, but its easy on ALC as they have a steel cooling box. On Omni products with the aluminum fins, it is not so easy to get a magnet close enough. The magent(s) tends to want to fling itself towards the magnetic Nickle/iron alloy end bells, either shorting something or breaking the Brewster Stems, even if you use epoxy or 3D printing to make a magnet holder.
My immediate thought when I considered selling you my sole remaining all lines miniature OC, was "over my dead body". At 0.5% average transmission, that is one rare optic when a larger tube starts at 1.5 and up. More common is a RRYB or RYYB OC.
A trick you could try is to align an external , long radius, red hene OC with your current all lines configuration, using a mirror mount like a MM1 or MM2 with 80 pitch screws. You may see a weak set of All Lines. Watch your eyes when aligning a back reflector aka "three mirror" cavity. Not to mention it was a 250$ piece of glass, in 1990s Dollars.
These optics are all tuned to a purpose when coating. Lines with more gain get less reflectivity in the coating, as to let out more power from the cavity.
I have some strange broadband and narrowband mirrors in my rather large collection, drop me a PM and I might have some things you can play with cheap. Some are even 7 mm.
I own two ILT krypton only heads, so I have already done this experiment long ago.
Steve
Last edited by mixedgas; 01-07-2021 at 09:55.
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