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Thread: SP 127 HeNe - Cleaning & Adjustment

  1. #1
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    Default SP 127 HeNe - Cleaning & Adjustment

    Hi all

    I've just acquired a Spectra Physics 127 HeNe, a laser of pure beauty

    When I first switched the laser on it produced a <1mW faint red dot. On removing the cover I see three adjustment points along the tube. After Googling and watching a YouTube video I made a *very* small adjustment to these pots and the result is that the laser now outputs 15mW. I'm reluctant to make too much adjustment as I really am quite unsure how much movement the tube will take and whether or not there is a risk of cracking the tube through over adjustment. There are also some artefacts around the beam which I suspect may be from the OC (or other optic) being dirty.

    Can anyone offer any basic advice on how to get the best from the laser? Things such as the correct adjustment procedure for tube alignment. Removal, cleaning & refitting of the HR and OC etc

    I'll probably wait until the UKLEM to do the work but I figured there would be no harm in asking the question here first.

    Many Thanks

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  2. #2
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    Use the set screws on the sides of the mirror mounts to fine adjust alignment. Very tiny movements have a huge effect on the output. Removal of the mirrors should only be done after you've first mounted the head with another he-ne laser's beam going backwards down the beam so you can get it to lase again after cleaning the optics.

  3. #3
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    Jem, there are 2 types of mounts on the 127, the type Eidetic describes and the torturous ones I have on mine which were clearly never meant to be adjusted; I hope for your sake you have the former! If you're coming to the UKLEM, I'll walk you through the mirror adjustments as I've done quite a few open frame HeNes and ions. Presumably you bought one of the 3 advertised by an ebay seller recently?

  4. #4
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    Thanks guys.

    Yes, recent purchase from eBay, and there are still two left at <£200.00

    I love HeNe lasers and have to confess to always having had a craving to own one of these beauties for quite some time.

    I'm going to resist the temptation to fiddle any further and will bring it to the UKLEM. Do I need to bring a small HeNe and Newport scissor mount to aid adjustment? (anything else?).

    Thanks for the offer of help, there'll probably be a few 'ion heads' there so i'm hopeful of teasing 30mW + out of it
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  5. #5
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    Yes, bring a HeNe along and whatever you have got to mount it on; I have a scissor platform and some tube mounts. Worth bringing some cleaning materials along as well, although I'll try to bring some along.

  6. #6
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    I'd be very careful about how I'd mount the SP-127 and the alignment he-ne. They both have to be solid as a rock for success. Best bet is to use two steering mirrors between the two lasers, for easiest and least frustrating alignment.

  7. #7
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    Thanks for the tips Bob, very much appreciated
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001

  8. #8
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    Quote Originally Posted by Eidetic View Post
    Best bet is to use two steering mirrors between the two lasers, for easiest and least frustrating alignment.
    Can you describe this arrangement further? I'm having a hard time wrapping my head around it...

    DZ aligned an old SP-127 at SELEM many, many years ago, and it was amazing to watch him work. Took him a couple hours, but once he got it dialed in it was making quite a bit of red. Don't remember who brought that laser, but I do remember it was the biggest damned HeNe I'd ever seen!

    Anyway - just curious about the "steering mirror" comment...

    Adam

  9. #9
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    He-Ne lasers have really long, small diameter bores. To get a long one to lase usually takes an alignment he-ne going backwards down the bore to set the high reflector at the back to retroreflect the alignment beam back down the bore. Because adjustments to the alignment he-ne are soooo sensitive, it's important to firmly secure both laser heads to a common base so they don't get bumped, or drift out of alignment. Placing two beam steering mirrors on tilters allows the user to do this fine alignment quickly and accurately. The first one catches the alignment beam and sends it toward the second. The second one directs the alignment beam into the tube being aligned. It's best to poke a small hole cleanly in a business card and tape it to the output end of the alignment he-ne. Make the hole as small as possible to pass the output beam. This will make aligning the retroreflection to that output way more accurate. Without taking the time up front to bolt everything down firmly, one could be hunting for alignment for hours.

  10. #10
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    Got it now. For some reason I was trying to picture the beam path with the aiming laser in-line with the one to be aligned (like this: - - ) rather than being parallel and adjacent (like this: =). With the second arrangement, it totally makes sense to have a pair of bounce mirrors on MM1s to give you perfect aiming control of that beam to get it directly down the center of the bore.

    Adam

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