Medical Argon Lasers???

[perseus]

Hi Piotr,

I could not find any company called "Subsea Engineering" to find out what they do (or did?). I did find this quote "Several of the more intense emission lines from the argon ion laser fall within the blue-green 'transmission window' of sea water." Perhaps it was for range finding as you suggest.

Roger

[mixedgas]

Hi Piotr,

I could not find any company called "Subsea Engineering" to find out what they do (or did?). I did find this quote "Several of the more intense emission lines from the argon ion laser fall within the blue-green 'transmission window' of sea water." Perhaps it was for range finding as you suggest.

Roger

Its a compact medical frame through, at least for the end plates. Probably somebody at HGM's parent company decided to use some off the shelf parts for a special.

My bet is company name is Subsea Engineering Associates, San Diego CA.
Made undersea scanners for oil and gas pipeline industry

take a look at us PAt # 4707128

[mixedgas]

Subsea engineering ... sounds like this was built for some underwater project, thus requiring water cooling. Soemtime ago there used to appear argon lasers on eBay, housed in sealed steel cylinder similiar to pressure tank. But what purpose of having an underwater argon laser ? Rangefinding ?

Piotr.K

The ones in the blue tanks were made by Hughes Laser Division as research project
for the US Air Force, for airborne mapping. I have the 175 page specification,schematics, and project summary for that with drawings.Its a ceramic tube, very much like a lexel. . William Bridges, the inventer of the argon laser, did that work for Hughes. You can order it on microfilm from the US department of Commerce. The place to order it from is NTIS.

http://www.ntis.gov/

And again, my apologies, if that PSU and frame assembly would have came out of the same chassis, it would be a spectrum , part of the edo series.

Steve

[perseus]

I am confused. I realize that medical Argon lasers are most likely to be pulsed but this laser appears to have been made for “Subsea Engineering Associates”. It seems unlikely that a company by that name would have made a medical laser product. Maybe it started as a tube made for a medical laser and was modified for Subsea Engineering . Their patent # 4707128 refers to a pulsed laser but it also refers to a Q-switch.. My laser has no place for a Q-switch within the resonator cavity.

Can an Argon laser produce a short enough pulse of light to be useful for range finding by pulsing the tube current? Even if it can wouldn’t that method severely limit the pulse frequency?

Is it possible that the ALC-905 was produced in different versions, with different fill pressures so that some were optimized for CW use and others for pulsed use? Does the fact that my laser happily operated at high output for 40 minutes CW suggest that it is a CW laser (or just that I likely damaged a pulsed laser???).

Steve - what is a "PC-Spectrum Hybrid"? Is it a variation of the ALC-905 tube? Is it a finished product that might have contained an ALC-905 tube? About the magnet. What magnet? I thought the large black cylinder around the outside of the laser was the outside of the cooling cavity. There are two wires coming out of it but they are much smaller gauge than the magnet wires coming from the HGM-5 PSU. I assumed these wires on the laser head were for a temperature sensor. I just measured the resistance across those two wires coming out of the laser head. It is 230 Ohms. Isn’t that a bit too high to be a magnet? There are only 5 wires on this laser – 1 anode, 2 cathode and the other 2 I just described. There is no metal tag on the fill stem so that does not help.

There are only two other labels on this laser head. They are the optic identification tags. The one on the HR end says “Part # 5MR030” and the one on the OC end says “5MR044” in case that helps.

I put a prism in the beam and only saw one beam out. The only place in my house with 230 volts and running water is the laundry room so that does not give much distance for the prism to separate the wavelengths. Result is that I still don't know if the laser is single line or multiline.

Roger

[mixedgas]

Subsea made both yag and argon scanners, I was just showing you how I found them.

Argons are not Qswitched, they have almost no upper lasing state lifetime, so no energy storage like a yag.

your tube is mounted in a medical OEM frame.

Steve - what is a "PC-Spectrum Hybrid"? Is it a variation of the ALC-905 tube? Is it a finished product that might have contained an ALC-905 tube? PC-SPECTRUM was a argon medical system that would have contained a similar tube. Thats what fooled me in the picture. HGM and AMERICAN LASER were divisions of the same company, Laser Corporation. They shared a tube plant and senior engineers, but the construction lines were different. Medical systems were set up as long pulsed at a lower pressure to run at high currents, until the pressure builds up in the gas returns and limits power, that takes about 1 second in a longer tube. Most of their scientific products and OEM products were NOT pulsed.
So since we have ruled out that you have a pulsed laser, you can run cw. I'd keep the current at 10-12 amps untill we learn more about 905s.

place a amp clamp on the cathode leads, see if your cathode current increses a little when the arc is lit, like a amp or two. If so the tube is healthy, happy and has good gas pressure. If not, well will go from there.

Anode end of the tube should show north on a compass with the right magnetic field applied. No field will cause the bore of the tube to erode and bury gas
in the tube walls fast.

About the magnet. What magnet? I thought the large black cylinder around the outside of the laser was the outside of the cooling cavity. There are two wires coming out of it but they are much smaller gauge than the magnet wires coming from the HGM-5 PSU. I assumed these wires on the laser head were for a temperature sensor. I just measured the resistance across those two wires coming out of the laser head. It is 230 Ohms. Isn’t that a bit too high to be a magnet? There are only 5 wires on this laser – 1 anode, 2 cathode and the other 2 I just described. There is no metal tag on the fill stem so that does not help.

905 needs a magnet, and its around the cooling jacket. That would explain why you only got
120 mW, and were lucky the tube started without it. The 230 ohm coil on 220V rectified would make the ideal ~800 gauss field at about 1.3 amps.

Thats why your having problems, NO MAGNET!

Turn on the magnet!

keep the tube current low on the tube for a while ,say a few hours, as you might have stressed it.

Since yours is a 905 and not a spectrum, I'd say its filled for CW!

Steve

[perseus]

Steve,

This is getting interesting. Now I wish I had a working PSU so I could try out the laser with the magnet. My estimate of 130mW was based on an embarrassingly simple measurement. I looked at the photovoltaic potential appearing across a red LED placed in the path of the laser beam compared to the same arrangement with a tube known to produce about 29mW. I never suspected that the optical power to voltage relationship would really be linear over such a large range. Since the ALC-905 had no trouble burning a hole through black electrical tape in a couple of seconds I figured the output must be much higher than 130mW (?????). It is really quite bright with my Argon goggles on (OD between 0.8 & 3.2 depending on the wavelength).

Any idea how much difference the magnet is likely to make?

I do have one each Uniphase 2111 and 2114 PSU's. Before I got the HGM-5 PSU I tried the ALC-905 with the Uniphase 2111 and the igniter from my Spectra Physics 161C Argon head. With this arrangement the ALC-905 would not light. Also I am not aware of there being any magnet supply in the Uniphase PSU's.

Roger

[LesioQ]

Additionally, running the magnet should drive tube voltage down by some 10% or like at given current, decreasing it's admited power, thus reducing thermal load, also giving some breath to PS (except MJs in linear passbank).

Piotr.K

[mixedgas]

No way a small aircooled psu for a 9 amp 106 V tube is gonna light a ~20 amp 165-200V or so volt tube. You need to fix the model 5 supply. You also need to measure the tube current for any meaningful measurmentsm, a .1 ohm resistor in series with the tube is the traditional way. In your case, you'll need to mount it in the anode lead before the HV blocking diode. Wait, since that is a model 5 which uses a tickler ignitor on the outside of teh tube, you may not have a blocking diode (should be a 11RA90 in series with the anode lead) That could explain why the supply went poof, no magnet and no blocking diode to keep the HV out of the high side pass transistors in the switcher. I'll need to look at the schematics tonight at home

ditch the red led, it cant produce enought charge carriers to measure 1 watt or more. assuming multiline optics, tune for peak green then peak the low violet lines using a grating or prism if you have no power meter. Different lines will come up as you increase current, Move only one adjustment at a time, see sam's laser faq on tuning and aligning ion lasers (I wrote most of it) for dos and donts,



If that is truely a unhacked hgm suppy, a small 4 pin "molex" connector should be hanging off the back with two wires. It should be across emitter resistors in the psu as a form of current measurment for service engineers. use a floating voltmeter (DMM with battery power) to measure the small amount of voltage there as it sits at line potential, it will only be a few hundred mV DC. . I'll call my friend and get the V to I conversion factor for you.

I would not run it without a tube current measurment of some form.

when you get that tube lit, keep it at 10 amps for while.

I need to make some calls to get operating specs on a 905, I'd assume similar to a lexel 88.

how long is the distance from the window stub (ie where it bonds to the tube at a glass to metal seal) to window stub, which should be a little longer then the length of the magnet.
I can make some educated tube voltage guesses from that distance.

oh, some tubes in smaller air cooled lasers using a much lower current density per linear centimeter do not use magnets.
anything watercooled needs the magnet due to higher J/D products

Be aware that the plasma tube has a slight negitive resistance, if you are not truely running constant current, it will oscillate and blow spikes of HV back into the supply, If the supply starts to fail for any reason, the current through the transistors gets nearly infinate for a few milliseconds and melts the transistor, showing up most often as a short from lead to lead from melted metal. That supply is a hybrid, it is switcher that has a linear passbank. If the linear passbank voltage exceeds about 14 volts, set by a zener on the control card, the PWM chip starts to back off on its duty cycle
to reduce stress in the big MJs. check the small electrolytic caps in the passbanks, they often are stressed when a transistor blows, and since they protect the transistors, they can damage a new part if they are shorted/leaky.



Steve

[perseus]

Steve & all,

I understand now that the HGM-5 is intended for use with a tickler igniter on the outside of the tube but at the time I got mine going I did not know that. I wound my own series injection transformer on a toroid. A description and picture of the transformer is found earlier in this series of posts. It seems to work well to light the tube but I don’t know what problems that inductance in the anode lead might cause (it might serve to block spikes back into the PSU though???). Should I be switching to an external tickler igniter? The reason I did not use one in the first place is that I suspected that it would not work with a water cooled tube effectively connected to ground.

My PSU does have the small 4 pin "molex" connector hanging off the back with two wires. Knowing the V to I conversion factor for that will be very helpful.

Since I don’t have an optical power meter I had in mind using a thermister on a small block of carbon and a heating wire attached to the thermister. My idea was to use an op amp to control the current to the heating wire to maintain the thermister at a constant temperature well above ambient. The difference between the electrical power going to the heating wire without incident light and that with the laser light incident on the sensor should be a decent measure of the optical power of the laser. It’s not really my idea but just applying the principle of the force restoration balance to optical measurement. Does this sound like it might work?

The distance between the two points you mentioned on the tube is a hair over 12 inches. I have included photos with X’s marked on the points I used for measurement in case I used the wrong points.

The PSU appears to be made for optical feedback. The control and feedback lines into the op amps on the HGM-5 control board would have been floating when it was running the 905. I imagine that floating inputs might account for erratic behavior like perhaps the mild flickering of optical output I saw. From your look at the schematic does it appear to you that the optical feedback is essential?

I thought it was likely that I had fried more than just a couple of MJ10005 transistors when my PSU quit. Knowing where else to look for problems is very helpful. It is probably apparent that I have a few clues about electronics but ONLY a few.

All this discussion is extremely helpful to me. I hope it benefits other visitors as well.

Roger

[buffo]

Hey Rodger;

That molex connector on the back of the PSU that Steve is talking about... I checked the voltage readings on mine with the tube running. I got .46 volts with the tube at idle, and 1.48 volts with the tube running wide-ass-open. Without knowing the conversion factor, I don't know what 10 amps of tube current would work out to, but my guess is that if you stay below 1 volt on that connector you'll be OK.

Adam