CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 6:47 am 
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http://www.laserfocusworld.com/articles ... tions.html

well......it seems cool from many point of view....
ciao
alberto

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 8:01 am 
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Wow, they assert that this lamp is "economical"...
http://www.energetiq.com/html/eq99.html#
Alberto do you know about the price for this beautiful source light?

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 8:27 am 
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Ciao Paolo,

paolocerruti wrote:
Wow, they assert that this lamp is "economical"...


well, you know, economical is a relative word........... 13 k euros if i'm not wrong... :lol: :lol: :lol:
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albé

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 10:22 am 
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Wow that is pretty cool Alberto, thanks for bringing it to our attention. As those of us dabbling in gem spectroscopy have found out, the light source is as critical as the spectrometer. And a good UV range light source is the most difficult nut to crack.

This new source is more collimated (and thus brighter) than conventional UV sources. But just as exciting is its smooth, relatively flat distribution across the UV and visible range. I've been waiting for something like this for quite a while.

I have to have one of these!


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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 10:33 am 
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hey Brian,

Brian wrote:
As those of us dabbling in gem spectroscopy have found out, the light source is as critical as the spectrometer.


i dare to say, probably more......

i've read some papers and it seems really cool from MANY point of view.....

Brian wrote:
.
I have to have one of these!


yeah i wish i could afford it......dang 13.000 euros are definitely NOT a joke :shock: (at least for me.... :wink: )
ciao
albé

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Apr 05, 2012 6:28 pm 
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Yep Alberto, that many euros are no joke for me either. Not going to happen soon, but eventually I will have one.


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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Fri Apr 06, 2012 2:35 pm 
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Quote:
I have to have one of these!


lmao

I have a vision of Brian pestering everyone at the university for years (hopefully months) till they buy him one and tell him to "go play" :lol: :lol: :lol:


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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Fri Apr 06, 2012 2:41 pm 
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Frank wrote:
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I have to have one of these!


lmao

I have a vision of Brian pestering everyone at the university for years (hopefully months) till they buy him one and tell him to "go play" :lol: :lol: :lol:


:lol: :lol: :lol: :lol: :lol:

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Sun Apr 08, 2012 10:31 pm 
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Frank wrote:
I have a vision of Brian pestering everyone at the university for years (hopefully months) till they buy him one and tell him to "go play" :lol: :lol: :lol:


Frank, your vision is entirely too close to the truth. :oops:


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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Thu Jun 07, 2012 6:31 am 
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Another one:

Coming soon Avantes AvaLight-LDXE

I just hate the logarithmic output spectrum trick. :D
There is still more than one order of magnitude difference between SWUV and infrared.

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Sat Jun 09, 2012 12:37 am 
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These lamps present an amusing irony. Back in the day when the ruby laser was invented they used xenon flashlamps to pump the ruby rod into lasing. Later xenon flashlamps and xenon long arc lamps (continuous operation, HOT lotsa watts) were used to pump Nd YAG lasers.

Now lasers are being used to pump xenon flashlamps. I know I should get a life but I do find that amusing.

I cant thing of much use for these in gemology. Their main use would be for someone who needs high radiance. That has always been something that is very tricky. And it used to require lasers , if you were able to make use of monochromatic light. Even the most ordinary laser when focused with a very simple lens gives extraordinary radiance. (Combination of small spot size and brighness)

These lamps will experience (if I understand what is going on and Brian please correct me if I don't) competition from super continuum lasers. These are often made with fiber optics. Also pumped with lasers.

One of our physicists has been playing with one and I was in his lab while it was running. He had the continuum thrown onto a white screen, probably just a white shirt cardboard. I think it was one of the most beautiful things I have ever seen. It was like a spectrum of a xenon arc lamp only with bands of intense and bright color. Like a projected gem. Just amazing. I will ask him if I can try to photograph it or video it.

The continuum fiber was being pumped by red laser light from a really expensive laser.



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I just hate the logarithmic output spectrum trick.

Spectra are almost always plotted that way when the range is needed. And photometers read out that way too. And Absorbance is a log phenomena too.
Why would you hate it. It is not an attempt to deceive.

Quote:
There is still more than one order of magnitude difference between SWUV and infrared.

The xenon spectrum is pretty flat in the visible but it has a bunch of nice powerful lines in near infra red which make it great for pumping ruby lasers.
That difference is a bit peculiar though. The amount of shortwave energy that the xenon discharge emits is proportional to current density and history and all kinds of atomic emmission stuff that is above my physics level.

But it IS quite peculiar that they cut the spectrum off at a wavelength longer than 200nm even while talking about whether or not you need to purge the container of air and oxygen (to prevent the formation of ozone) It is easy to get down into the ozone and vacuum UV with both xenon short arc and also guided arc (strobe) pulsed sources.
You really can get as much UV as you want. You also can get all the radiance you could possibly want or need for any gemological purpose.

I am sure that the Avantes production unit will perform better than the graph they have currently posted. I can't think of why anybody would want one of the Avantes units though. An Ocean Optics PX1 or PX2 would probably give you more SWUV energy. Avantes probably sells those in their livery too.

http://www.avantes.com/Chemistry/AvaLig ... flyer.html

The above xenon pulsed guided arc put 180 mW into a 600 micron fiber. (at 100 pulses per second) The laser pumped unit only 153 mW.


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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Sat Jun 09, 2012 3:22 am 
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I'm looking broadband light sources only from gemologist's point of view and more specifically how suitable they are for UV-VIS-NIR transmission spectroscopy. Yeah, these sources are more than that but like you said it's common practise to show logaritmic output for all kinds of light sources sold for use with CCD spectrometers.

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I can't think of why anybody would want one of the Avantes units though. An Ocean Optics PX1 or PX2 would probably give you more SWUV energy.


Excatly my point. I wouldn't call logarithmic output scale as deception but it surely is a trick .

An ideal source would be something that has flat output at same magnitude from deep UV to NIR so that good S/N transmission spectrum can be measured for the whole range with one sweep. Lower quantum efficiency of CCD spectrometers at UV combined to 10-100x lower UV- output vs. visible wavelenghts means one has to start to play with integration times and divide the measurement process to two or more sub-measurements, then trying to compose the results for making continuous spectrum from UV to NIR.

Quote:
It is easy to get down into the ozone and vacuum UV with both xenon short arc and also guided arc (strobe) pulsed sources. You really can get as much UV as you want. You also can get all the radiance you could possibly want or need for any gemological purpose.


I recently was lucky to find 60W pulsed xenon flash source made by Japan company Hamamatsu. http://jp.hamamatsu.com/products/light-source/pd025/index_en.html

It has sapphire window for allowing very high ozone forming UV output. Nominal color temperature for continous spectrum is 15000K :shock:
I was bit worried about the xenon spikes these sources always have but with some averaging transmission spectra are nice and smooth.

Only tricky part was learning to syncronise the flashes with spectrometer so that there is even count of flashes per integration time. That is not too difficult since most spectrometers today have a trigger output for commanding pulsed light sources.

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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Mon Jun 11, 2012 4:04 pm 
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While I totally agree with you that what we used to call in audio "Flat Frequency Response"
is always a good and desirable idea, there are very few situations where it is achieved.

If you look at the sensitivity curves of the silicon detectors that are mainly used they too are hardly anything like flat. This is why its good to have wide dynamic range detectors and A/D converters.

http://en.wikipedia.org/wiki/File:Respo ... odiode.svg


Have you gotten any more spectrometers to work with that badboy xenon flashlamp outfit?

Its a good idea to operate those in a metal box with only a fiber optic or the light coming out. The closer to operating inside Faraday cage , the happier all the other electronics will be.
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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Wed Jun 13, 2012 10:49 am 
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Quote:
Have you gotten any more spectrometers to work with that badboy xenon flashlamp outfit?


Yup, Ocean Optics USB2000+

Triggering works pretty ok but not perfectly with SpectraSuite. Had to write my own software for smoother operations.

I must say the Hamamatsu is awesome! One to ten strobes each of only couple of microseconds is all that is needed for single transmission measurement. One flash without UV-goggles makes the eyes sandy for the rest of the day.

Tiny bulp is packed to a massive fan cooled jacket. Middle box is essentially a faraday cage having row of BIG capacitors, giving 300-1000V for the xenon.



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 Post subject: Re: spectrometry state of the art lamp?
PostPosted: Wed Jun 13, 2012 10:58 am 
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UHU, Braggart!!! 8) :lol: :lol: :lol: :lol: :lol: :lol:
ciao
albé

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