Lasertastic

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Fried Power Supply

2008-06-26T11:10:00.000-07:00

After all the troubles we've had with the SpectraPhysics Evolution/Spitfire system (see JP's blog below) it came as a shock to actually have other problems. Our OPA (Light Conversion Ltd. Quantronix TOPAS) had been a trooper, finicky yet appeasable. In fact, 98% of the time when we have issues getting power out of the TOPAS it's because the pulses out of the amplifier are not quite what they should be. It has had it's frustrating moments, it not really being calibrated means we usually have to go through the extensive guess-and-check procedure of setting the wavelength out, realigning the DFG, and finding the beam after the spectrograph to discover that we're nowhere near where we set it (wash, rinse, repeat). But in recent months it had settled down, giving us reliable powers without any realignment and dutifully managing to output the exact wavelength of light we required on the first try. Life was good...

...Until we tried to change the wavelength again (for the 4th time in as many weeks) and nothing happened. No crystals turning, no grating being adjusted, no stepper motors at all, in fact, doing what they are supposed to do. The computer program, WinTOPAS, thought it was doing something, but nothing was changing. After attempting the tried-and-true method of turning off everything and unplugging it, then plugging it back in and turning it back on, it was clear that something serious had gone wrong. The SOS to Lithuania was sent out and the following day we received an answer: "Sounds like the power supply. Turn the TOPAS over, take the bottom off and take some pictures for me." Needless to say we were not excited about turtling the TOPAS, but we obviously couldn't do any work otherwise so over it went. Immediately it was apparent that the power supply had blown; the board was blackened, the capacitors were swollen and gooey, and some type of explosion had left splatter on the nice white case.

The next day we had two new emails from our peeps in Lithuania, one from the sales associate giving us an unofficial quote for the pieces we may have to replace (that also happened to be in stock), and one from the electronics tech giving us specific instructions to test the control board to see if that needed replacing as well. The testing went smoothly, only the power supply needed replacement, and the official quote for the part was emailed to us within an hour of our request. (Donatas must have been working late that day, Lithuania is 10 hours ahead of us.)

Overall, this TOPAS catastrophie turned out to be a minor hassle. The quality of service we received from Light Conversion Ltd (Quantronix) and the snappy responses from the well-coordinated support team, despite the 10 hour difference, put them miles ahead of SpectraPhysics. The whole snafu has completely allayed any anxiety I may have had about the tech being in Lithuania (as opposed to California). The $150 power supply is being ordered and sent to us with UPS Express and I have no doubt that the TOPAS will be up and running shortly after the 4th of July. Our special thanks go out to our contacts, The Big G, Donatas, and Darius, for proving that it really is a small world afterall and you don't need to be in the same hemisphere to provide good service.

Never Thought I'd Be A Laser Jock

2008-05-08T12:14:00.000-07:00

At some point when I was looking for an advisor and was interested in Phil Reid I was discussing the option with one of my fellow first-years and she said that she had been interested in his research as well but didn't want to be a laser jock. I didn't think much of the comment, I shrugged it off and convinced myself that really, just knowing how to run your instrument is not a bad thing and I would definitely learn more than the shmo down the hall who just flips a switch and expects things to work. Plus, I'm sure, it was a matter of ego at the time... being a member of the small community of scientists who know how to run an ultrafast laser system was appealing to me. It still is. But five years later and with 8 months of serious laser jock-ing (pretending to be a laser tech) under my belt, I have a slightly different idea of what it means to be a member of this community. I never thought I'd be a laser jock, in the back of my mind I still always just expected things to work, but now I know you can't really do research in this field without becoming one. And so I will embrace it.

Troubles With Lytron Kodiak Chillers

2008-04-30T10:12:00.000-07:00

While this post itself might not be too lasertastic, hopefully it spare someone from the pain and frustration that my lab has had to go through regarding Lytron chillers.

Just for a little background, Lytron Kodiak chillers seem to be the standard chillers that come with laser systems produced by Spectra-Physics/Newport. We currently have three in our lab, but the most trouble has been with the chiller hooked to our Evolution pump laser for a Spectra-Physics Spitfire. Here are a list of a few problems we've had and how to fix/prevent them from happening to you.

1. The PVC t-joint that contains the thermocouple for the chiller is prone to break. Cracks usually occur at the top of the t-joint where the compression fitting for the thermocouple is. There is a small groove at the top of the joint that seems to be the culprit. Lytron offers newer replacement fitting that don't contain this groove, but if you've got the dark gray PVC t-joint you should consider replacing it or at least keeping a close eye on that piece.

2. The brass pump heads contain a graphite impeller that has a tendency to slough off graphite into the chiller lines. These particles can build up in your laser cooling lines and create all sorts of problems (Don't worry, I'm already planning another post discussing all those problems). You can purchase a stainless steel pump head for around $300 from Lytron that doesn't have these same problems. Considering it's a relatively cheap part in comparison to the cost of your laser, it's worth the money to replace it.

3. In an attempt to also avoid getting particulate matter into your chiller lines your should also upgrade your filtering system to include both 5 and 1 micron filters. IF YOU DON'T HAVE ANY FILTERS GET SOME NOW! You'll most likely need to get another filter basket to house the additional filter, but they're pretty easy to find at the Home Depot. The 1 micron filters however, you'll probably have to buy online. Once again, this is a pretty inexpensive upgrade to your laser that will keep it running smoothly.

4. One last note, don't have ever add dilute HCl to your chiller reservoir in an attempt to flush out algae. You'll get the algae out sure, but the HCl will also corrode the Teflon chiller lines, or at least the ones in an Evolution. And no, adding the HCl was not my idea. I would recommend Nalco Cleanser for that purpose. I would pretty well. Just make sure you dilute it first. About 19 mL per 1/2 gallon of water is the recommended concentration.

I hope someone finds this useful. Not taking care of these things put my laser out of commission for 6 months. Even almost another 6 months later we are still occasionally feeling the repercussions of poor chiller maintenance and construction.

Best of luck lasering,

JP

Hope this is semi-lasertastic.

2008-04-29T14:40:00.001-07:00

Over the past few months we have attempted to measure single-molecule SERRS... oh yes, as a function of excitation wavelength. We have this fabulous excitation source (Mira OPO) that puts out (reliably) from about 490 to 650 nm or so... awesome! But turns out the pulses out of this thing appear to be blowing up molecules. (No es bueno) So the big feat of the day was replacing the single spectrograph/CCD for the triple, aka "photon motel". By the way, my love of the term photon motel is endless. We hope that by putting our photons in the Hilton (bad), we can lower our acquisition time before the onset of photobleaching/annealing? We'll see. I'm mostly excited about getting this blog working. I will to improve upon my blogging skills.