need help (netherlands) spectra-physics 168-35 whitelight

[Stoney3K]

i cant find it but somewhere i explained how to do it with a shadow box. These lasers have so much gain you dont need to shoot them...it is all about technique. I wish I could come over there and just do it...i've never been to the Netherlands.

OK, that does save us a lot of fiddling about with the mirrors. Basically it's just 'rock the hell out of the HR at the back end until you hit bulls-eye, then dial the beam to center'. Should be easy enough!

I'd like to know how to take off the Brewster covers as Rob described, just to avoid any damage. Am I correct when I spotted an Allen-type bolt (the inside hex nut kind, not the pro DJ ) and the covers can be taken off in two halves?

Are there any points I should avoid stressing too much to risk damage to the head?

[Stoney3K]

OK, breaking news, because this 25-year-old whitelight saw coherent today!

We started in the afternoon to fire her up, setup was pretty quickly this time, and fortunately, on a lot more stable work surface than the last run.

The head startup was a bit iffy at first, because the PSU interlock kept buzzing and trying to trip, and we couldn't get enough juice to crank the current up to 30A without the breakers triggering. I ultimately traced that back to a loose 400V wire on the step-down transformer (so the L3 was going via neutral, luckily without any damage), and wiring that back up, we had full power at our disposal.

Water flow was better this time as the head was lower to the ground, and it even convinced the PSU's 'WATER ON' light to give a glimmer. Flow isn't optimal yet, I suspect a crudded up filter, and possibly the 'Overpressure Drain' plug/switch which was plugged into the back of the PSU. Unplugging it seemed to have no ill effects, and flow through the head was perfect with no air.

We proceeded to alignment, first using Pat's trick to no avail, and I ultimately decided to give the bore a bit of a shoot-through. We spent more time looking for a reference laser (ultimately a 200mW DPSS green handheld) than we spent aligning it, and the most time-consuming job during the alignment was getting the green in position so it hit the wall 6 feet from the other end of the bore. Removing the mirrors WITH their mounts proved easier (just needed a Torx screwdriver) than trying to pull the mirrors only, and our shooting-the-bore record for the 168 currently stands at 17,5 minutes.

Once the reference laser was in place and the HR put back, we decided to give the beam a return to sender, and put the OC back on. Lucky on the first try -- only 4 twists of the knob and we got a bright cyan flash, a tell-tale sign of 488nm photons standing attention and ready to run through the OC to hit a brick on the other end of the beam!

Subsequently, we did a few measurements and tried to max it out a little more, peak power at that time was about 800mW on the 265 power meter. I measured 600mW of 488nm on a Coherent Lasercheck, so any stray power in the other wavelengths would make sense.

There wasn't a lot of krypton lasing going on though, probably because the optics were filthy and we did alignment on a shoe-string. I did notice some more lasing in the high-nanometre range when I dropped the field current on a low-power run, but I was a little reluctant to turn the regulator all the way down. At least we're certain it's a white light!

I unfortunately lost the lasing alignment about half an hour later trying to walk the beam to the center (it was way off to the left), but at least, now we know how this thing works. It's not difficult, just time-consuming, and Danny is going to give it another shot tomorrow.

When we've got more time, I'll probably give everything a good clean-over and get a proper reference laser to get the alignment sorted out. I'll have an ILT argon laser at my disposal shortly for that, and we've already arranged a Nexos 8-channel PCAOM and Cambridge CT6800HP scanners for the laser, which would make this a seriously top-end system as it was intended.

I'll do a little photo write-up tomorrow.

[stanwax]

great news - I look forward to a progress report with images
Rob

[laserwinkel]

Here we have the pictures of a nice shiny Whitelight doing around 800mW at first run

http://www.laserwinkel.nl/fotos/DSC03355.JPG
http://www.laserwinkel.nl/fotos/DSC03356.JPG
http://www.laserwinkel.nl/fotos/DSC03357.JPG
http://www.laserwinkel.nl/fotos/DSC03358.JPG
http://www.laserwinkel.nl/fotos/DSC03359.JPG
http://www.laserwinkel.nl/fotos/DSC03360.JPG
http://www.laserwinkel.nl/fotos/DSC03361.JPG
http://www.laserwinkel.nl/fotos/DSC03362.JPG
http://www.laserwinkel.nl/fotos/DSC03363.JPG

[Laserman532]

Great Job Guys! Ok the only thing I see (other than power) is either the outside of the output mirror is dirty or the beam splitter in the OC holder is dirty. It is very easy to take apart and clean and re install without fussing with the alignment. Just another suggestion...I would not leave the bellows on the stem like that. I would back off of the small knurlled knob and remove the bellows completely leaving the nut and o ring on the brewester stem.

I would also be very interested to know what the tube voltage is when the current is set to 30 amps and the magnet is full...then measure DCV across the tube (red on anode and black to ONE SIDE of the cathode wires)

PS...DONT touch the magnet accidentally when measuring the tube volts

EDIT- Forgot to add...NOW THAT IS ONE NICE ADJUSTABLE HEIGHT TABLE!!! Very Heavy Duty...Could you change the oil while you are there

[Stoney3K]

Great Job Guys! Ok the only thing I see (other than power) is either the outside of the output mirror is dirty or the beam splitter in the OC holder is dirty. It is very easy to take apart and clean and re install without fussing with the alignment. Just another suggestion...I would not leave the bellows on the stem like that. I would back off of the small knurlled knob and remove the bellows completely leaving the nut and o ring on the brewester stem.

That's what I did for the first alignment attempt, and you can see everything is off (including the mirror mounts!) when we shot the DPSS through the bore. I can understand leaving the bellows on the stem might put a little strain on them because of the weight.

A cleanup job is on the to-do list. Now that we know how to take the optics apart, that's not a difficult, yet tedious job.

I would also be very interested to know what the tube voltage is when the current is set to 30 amps and the magnet is full...then measure DCV across the tube (red on anode and black to ONE SIDE of the cathode wires)

Last time I measured the tube voltage to be 234V, but I can't be 100,0% sure it was measured at 30 amps current. The fill gauge indicates the same voltage, just over 230V, so that's in the OK ballpark. The tube may be a little low on krypton.

EDIT- Forgot to add...NOW THAT IS ONE NICE ADJUSTABLE HEIGHT TABLE!!! Very Heavy Duty...Could you change the oil while you are there

Hey, what can I say, we had two choices: Use the floppy frame again, or just clamp it to the ramp. I chose for the latter, for obvious reasons, since there's plenty of space on one of those.

Note to self: Get a 400V extension cable so we can get the power supply and transformer on there as well, instead of having to put them all over the place. The cables were a bit short.

[mixedgas]

Winkle, don't loose the password twice this time, I may not be able to remember it again!!
And I'm NOT scanning it a 3rd time... But I may had draw small fragments if you need them.

Will delete in 1 week per EDUCATIONAL USE COPYRIGHT...


see inline attachments

[laserwinkel]

Great thanks, i saved them on my laptop.
thanks very much!

anyways i did not have time to realign the laser yet but tomorrow i will try it again
and if i got it i will try to center it to get the most power

[Stoney3K]

Great thanks, i saved them on my laptop.
thanks very much!

anyways i did not have time to realign the laser yet but tomorrow i will try it again
and if i got it i will try to center it to get the most power

Tip: Be sure to use either the HeNe of the ILT Argon we pulled out of the Datronik frame as a reference laser.

They're a lot easier to mount in a stable position than handheld pointers. If we can clamp the 168 frame down, we can also do it with the reference laser.

Bring everything up to height with some shims (yes, coasters actually DO work great for that) and make sure the spirit level is put to good use (for angular alignment).

If you're really picky, you can try to straighten the whole lot to 0,1mm with a caliper and a steady hand, but there's no way you can be sure the plasma tube is exactly dead center. (Don't even bother trying to move it, though.)

[laserwinkel]

i got the beam back today
did a bit of adjustment and got around 1100mW today

any tips to get it really close to the center?