HeNe tube question

Folks,
I just picked up a little HeNe tube complete with it's power supply / mounting bracket from an old supermarket checkout scanner. The supply has been modified to take a standard wall wart style 12V power supply @ .9A and even has a nice on off switch mounted to it. (Not pictured)

My question is about which way the tube fits into this power supply / i.e. which way it lases? Is the lasing end the end with the clear glass? I think this is the case, but would really like one of the gas vets to verify this before I damage the tube. Both connectors on the tube look nearly identical, other then one of them looks more copper / tarnished then the other.

Taking a look at the ebay auction pics linked here: http://laserpointerforums.com/f43/diy-hene-63170.html
It looks like the way I have it in the bracket is the correct way, but I just want to be sure. (And yes that auction is way overpriced. I got this one from an old friend for free. )

In my pics that's an 18650 for size comparison.

the clear part is where the beam exits. your last pic of the tube. the beams aperature is all the way to the left.

Thanks man. I was guessing that, but it's always good to get some confirmation.

Question though: How would someone like me know for sure, other then finding someone that knows the tube? Both ends have the same fittings / lens / mirrors (Sorry I really don't know much about gas lasers, so my terms are most likely incorrect), seem about the same. This thing can fit either way on the power supply clips.

You don' always know which side will lase. Some will have output from boh ends also (Albeit less and per Sam Laser faq, unuseable). I have a very small one that is opposite all the other ones I have.

Try this:

Sam's Laser FAQ - Helium-Neon Lasers

You will get output on both ends.. Though one will be very faint.
In almost every tube ive ever seen, the -gnd side is the lower output
of the two, and is easily noticed by the little 'filler' port where the gas
was added to the tube..

Perfect. That is exactly the way this one is. Both ends produce beams, but it's hard for me to tell how much the rear actually produces because of the way the holder is. (The back wall of the holder is nearly touching the back end of the tube, only the front end is open)

I just checked though and sure enough there is a little crimped glass fill tube on the rear of the tube. I'll file that info away for the future.

Here is an image of it compared to a little 650nm pen pointer. (Most likely under 5mw) I love that plasma glow from the tube, too bad so much of it is hidden on this one though.

I forgot to mention, the rear of the tube is emitting the same single beam..
The difference is the optics at each end. To give an idea have a look below..



Out of the front your beam will probably be around 1mW and from the rear
in the microwatts.

wannaburn said:

I forgot to mention, the rear of the tube is emitting the same single beam..
The difference is the optics at each end. To give an idea have a look below..

Out of the front your beam will probably be around 1mW and from the rear
in the microwatts.

Click to expand...

Like I said, all of my big ones are like that, but my little 6" Melles Griot is reversed. Weird!

http://repairfaq.cis.upenn.edu/Misc/sale/lsk1ins.gif

icecruncher said:

Like I said, all of my big ones are like that, but my little 6" Melles Griot is reversed. Weird!

http://repairfaq.cis.upenn.edu/Misc/sale/lsk1ins.gif

Click to expand...

That is weird.. :thinking:

Ive had a few different types, but I think the only melles I have is still
sealed in the aluminum housing.. Perhaps I have one and dont even
know it

Had a bunch of uniphase , siemens etc, of various sizes.. Never seen one
reversed...

Most HeNe tubes have the OC (output coupler) on the cathode end, that is the end with the aluminum cylinder. This is not a standard though, my recollection is that small Uniphase tubes usually have the OC on the anode end, as do most of the older "other color" Melles Griot tubes. Putting the OC on the anode end allows for slightly more power output for reasons that I don't really understand, but results in the output end being at a high voltage potential.

Whatever the case, make sure that you always power it with the + wire out of the power supply going to the anode, the end *without* the bit metal cylinder. Connecting it backwards will ruin the tube very quickly.