SSY 1's Recently?

[Ulao]

Depending on the timing between the pulses you'll have cooling (radiative at least) effects skewing your results but they just give you a slightly conservative reading compared to actual, which is not too much of an issue. Also there's the thermal impedances of the multiple layers, but we're just splitting graphite layers here =P .

Condition of the qswitch likely has a large effect on output power and I'm willing to bet it is why we see such variance between different members' findings.

I still want one of these, heh, it's on my bucket list along with a lot of other things I'm sure HMike would find fun, heh.

Another thing I noticed is that when I used a PIN diode to monitor the output on the scope was that above some voltage level (I dont remember what level) I would get multiple pulses and that wasn't really consistant.

 

[Hemlock_Mike]

I bought two of these lasers and they are a little different. One has a Q switch that I believe has a liquid inside positioned in front of the HR mirror. The other has a very thin window set at a 45 Deg angle in that space. One unit also has a rear assembly containing a photo diode behind the HR mirror.
Mike S posted some pictures showing the ringing you observe and noted that it happened when input power was increased. I don't know if the flash circuit was damped with a diode or not.
Part@Go sent me a PS for these and the first on had a HV leak. I tore it apart and found a 25 uH inductor and 5- 5.2 mFd caps rated 630 Volts. A new pack reads 26 mFd total.
At 600 volts charge, this would provide only about 5 Joules -- a safe level for the small tube.
HMike

For those following this, here is a picture of John's Spectro setup at present. He has been able to analyze some metal alloys with it.

 

[Ulao]

Yes I've seen references in your previous emails about that 45 deg. window and I can see how it would polarize the light but am mystified by how it would work in place of a q-switch.

 

[Polonium210]

So it's six and a half joules then? :wave:

I think I did my math right...

Correct me if I'm wrong but
660v at 60uF gives me 13joules..

At 30uF it would be 6joules

 

[The Lightning Stalker]

I think I did my math right...

Correct me if I'm wrong but
660v at 60uF gives me 13joules..

At 30uF it would be 6joules

Don't forget, caps in series reduce the total capacitance by 1 / ( ( 1 / C1 ) + ( 1 / Cx ) ). :beer:

Yes I've seen references in your previous emails about that 45 deg. window and I can see how it would polarize the light but am mystified by how it would work in place of a q-switch.

I don't think it's a Q-switch. Possibly it's just a dicro or a glass attenuator for a sensor that
looks down the bore to do the rangefinding. Though without the Q, the light pulse would be
so much longer, making it more difficult to get an accurate range estimate.

 

[Ulao]

Without a q-switch the pulse would probably be at least microseconds long probably have a fairly long rise time. At 12.36 microseconds per mile it's tough to get a precision measurement. No?
That system must have some alternative. Perhaps an active q-switch?

 

[Polonium210]

Don't forget, caps in series reduce the total capacitance by 1 / ( ( 1 / C1 ) + ( 1 / Cx ) ). :beer:

Oops... That was one minor oversight on my part! Thanks:beer:

 

[Hemlock_Mike]

P210 - Ain't math fun ??? You have the energy formula working.

John -- These were used for rangefinding. Mike S thinks that a polarized output would be important but I think that this is an early design and the shorter pulse was more accurate considering "C" ...... I may take the window out if I can't achieve alignment and accept a blob of photons on this one! I can see the Q on the other unit.
I like your power meter idea but I see not only radiant heat loss as a problem but also the heatsinking of the probe. Perhaps a non-contact temp meter? Protect the meter from the IR blast.
HMike

 

[Ulao]

I like the non contact thermometer idea if one can find one with a small enough sensing zone.

 

[Hemlock_Mike]

My IR temp meter which I use for cooking has an 8:1 ratio.
Placed 4" behind a 1" target, it would "see" 1/2" of target.
Suspend the target in needle points surrounding the carbon
slab. Now to find a carbon slab..............
Perhaps and old welding shop would still have carbon
welding / cutting / heating electrodes!!!! I never saw any
at the welding shop I worked at but I heard tell of them.
HMike
The largest I've seen are 1/2 " dia. At 2", an 8:1 would see only
1/4" -- That should be an easy assembly. I'll see if I can get bigger
rods and machine the material flat for a housing.

 

[Ulao]

I am working on a YouTube presentation to demonstrate how easily LIBS can be done. I will post a link here when done.
Let me post an example spectrum here as a tease.
Found a rock here in North Carolina which a geologist friend called eclogite.
Eclogite is a rather rare and interesting rock and consists of the minerals omphacite, garnet, & kyanite. The garnet was obvious. The omphacite I haven't yet done much work on (chemically it's kind of complex and variable). But I was able to confirm the kyanite spectroscopically and kyanite can only form at extreme temperature and pressure.
It is composed of silicon, aluminum, and oxygen and that is demonstrated by comparison to known samples. Oxygen won't show up.

Oops I put up the spectrum for sodalite instead of kyanite, but you get the idea.

 

[Hemlock_Mike]

WOW -- Real laser science......
None of the "will it pop a balloon?" stuff !!!!!
The Mars rover has a laser similar to the SSY-1
to do this too --- 10 to 12 pulses.
This is where the eureka part starts.
Our power meter ideas may be unique too.
That IR temp sensor could be coupled into a real
time readout so multiple pulses would not be needed.
HMike

 

[Ulao]

Sounds good to me Mike. Keep the disk small enough (mass) to keep the # of shots needed down.

 

[The Lightning Stalker]

In related news, I was looking at a high resolution setup last night. It came up on a LIBS
search (because I didn't know what it was). This thing can resolve down to like thousandths
of a nanometer.

 

[Ulao]

WOW -- Real laser science......
None of the "will it pop a balloon?" stuff !!!!!
The Mars rover has a laser similar to the SSY-1
to do this too --- 10 to 12 pulses.
This is where the eureka part starts.
Our power meter ideas may be unique too.
That IR temp sensor could be coupled into a real
time readout so multiple pulses would not be needed.
HMike

Keep in mind that even at 50 mg there is some time lag. I found that after 10 shots in 10 sec. that the reading didn't max till 12 or 13 sec. so it looks like the time lag is probably at least 2 or 3 sec. Of course I was using a thermocouple your experience may vary.

 

[Ulao]

Ok I presume "private messages" where's that?