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FrozenGate by Avery

Blue Kiss of Death to HeNe

pschlosser

pschlosser

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I have an orange HeNe that is near of life, outputting <25uW and I thought (after reading Sam's Repair) if I let it cook for a few weeks, its output might improve. One of the things to check, is the emission spectra of the plasma and the output of the tube for "new colors" meaning, signs other gasses have leaked in to the tube over the years.

When a soft-seal HeNe gets on in age, it tends to allow an oxygen and nitrogen inside, from time to time, and helium out, too. The specimen emits a faint beam, pink, near magenta in color.
IMG_4576_zps0a5fd0e6.jpg:original


Magenta = blue = oxygen spectra, right?

IMG_4611_zps58a17553.jpg:original


I dropped this RGB cube in front of beam. You may be able to see the blue and red dots faintly to the left and right of the cube.

IMG_4604_zpsc4f23c49.jpg:original


sorry, camera not wide enough.

IMG_4605_zpsb6171e46.jpg:original


I kid you not, that blue dot looked, in real life, just like a 405nm dot, so it's possible my camera filters out near UV.

Anyway, all that blue and purple is not good. And the magenta dot in the back appeared more... pink, in real life. I hope to fire another (7mw 633nm) through the RGB cube, tonight. I dichroic would work, too. I gotta root around and see if I can split off the blue from a red HeNe, lol.
 
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I doubt it's lasing - just the non-coherent emission from contaminants.
 
RIP indeed. But do keep in mind there are blue and violet lines in the normal emission spectra from a HeNe, they just do not lase. Check the non-lasing output of the cavity through the glass sidewall with a prism or a diffraction grating to see. If you see any kind of a continuum insead of discrete lines you have a sure sign of contamination. Helium loss is almost always the cause of death for well treated HeNes. On all my fully working HeNes I can see a blue halo around the 632.8nm beam if I look off axis a few degrees or filter out the red beam and let the blue pass. The OC mirror is not 100% reflective to the blue region.
 
Sigurthr said:
RIP indeed. But do keep in mind there are blue and violet lines in the normal emission spectra from a HeNe, they just do not lase. Check the non-lasing output of the cavity through the glass sidewall with a prism or a diffraction grating to see. If you see any kind of a continuum insead of discrete lines you have a sure sign of contamination. Helium loss is almost always the cause of death for well treated HeNes. On all my fully working HeNes I can see a blue halo around the 632.8nm beam if I look off axis a few degrees or filter out the red beam and let the blue pass. The OC mirror is not 100% reflective to the blue region.
Click to expand...

I see a similar effect if I put my finger in the path of the dot on my argon, there is a blue aura around 430-450 around the dot. Very interesting.
 
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