Greetings:


We use BBO-based optical parametric oscillators with additional
frequency doubling, pumped by 355nm from a pulsed ND:YAG laser to
produce wavelengths in the range of 220nm to 290nm at rather high
energies of 10-30mJ per pulse, with about a 8ns pulse width, and at 10Hz.

The OPO systems are extremely cantankerous since the energies starting
with the YAG pump source, and all the way down the line are right at the
damage thresholds of readily obtainable optics.

The systems work, but break frequently, and require constant fussing and
tweaking to keep the energy output optimized. The slightest
perterbations of temperature, long term surface degradation from high UV
fluences on the optical surfaces, etc. cause the thing to degrade.

We wish there was a better way, but there doesn't seem to be one
commercially available. A custom built system is not yet under
consideration, but might be the right way to go. Unfortunately it would
be very expensive to build, so it might never happen.

I'd like to get some basic understanding of synchrotron radiation. I am
aware that synchrotrons are much more expensive than commercial lasers,
so don't bother pointing that out. If it were a viable radiation source
for our experiments, I would consider applying for access to one of the
existing synchrotron light source labs. Though I sure wouldn't mind it
if we did build one here ;-)

I simply want to know:

1. if the synchrotron radiation that is generated by typical
synchrotrons intended for radiation generation (electron synchrotrons
such as the ALS and others), can be provided in the 220-290nm range?

2. if it is continuous or pulsed, and what is the typical power and
power density (power and beam diameter) for CW systems, or the energy
per pulse, pulse width, and period for pulsed radiation.

3. Can it provide very smooth beam profiles?

We do laser induced fluorescence imaging of combustion processes, in
case you are wondering. Typically of NOx, CO, and OH. So far only
qualitative imaging, but we would like to do it quantitatively. This
requires well behaved beam profiles, which our OPOs cannot provide, when
they even emit light in the first place.

Ok, thanks for your comments.


Good day!





--
__________________________________________________ _____________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
-- NOTE: Remove "BOGUS" from email address to reply.

Greetings:


We use BBO-based optical parametric oscillators with additional
frequency doubling, pumped by 355nm from a pulsed ND:YAG laser to
produce wavelengths in the range of 220nm to 290nm at rather high
energies of 10-30mJ per pulse, with about a 8ns pulse width, and at 10Hz.

The OPO systems are extremely cantankerous since the energies starting
with the YAG pump source, and all the way down the line are right at the
damage thresholds of readily obtainable optics.

The systems work, but break frequently, and require constant fussing and
tweaking to keep the energy output optimized. The slightest
perterbations of temperature, long term surface degradation from high UV
fluences on the optical surfaces, etc. cause the thing to degrade.

We wish there was a better way, but there doesn't seem to be one
commercially available. A custom built system is not yet under
consideration, but might be the right way to go. Unfortunately it would
be very expensive to build, so it might never happen.

I'd like to get some basic understanding of synchrotron radiation. I am
aware that synchrotrons are much more expensive than commercial lasers,
so don't bother pointing that out. If it were a viable radiation source
for our experiments, I would consider applying for access to one of the
existing synchrotron light source labs. Though I sure wouldn't mind it
if we did build one here ;-)

I simply want to know:

1. if the synchrotron radiation that is generated by typical
synchrotrons intended for radiation generation (electron synchrotrons
such as the ALS and others), can be provided in the 220-290nm range?


I think it can and even smaller range.


2. if it is continuous or pulsed, and what is the typical power and
power density (power and beam diameter) for CW systems, or the energy
per pulse, pulse width, and period for pulsed radiation.


http://www.srs.ac.uk/srs/



3. Can it provide very smooth beam profiles?


As far I know yes.


We do laser induced fluorescence imaging of combustion processes, in
case you are wondering. Typically of NOx, CO, and OH. So far only
qualitative imaging, but we would like to do it quantitatively. This
requires well behaved beam profiles, which our OPOs cannot provide, when
they even emit light in the first place.

Ok, thanks for your comments.


Good day!



Smart's Alt. Physics News Group
http://pub39.bravenet.com/forum/show...20272813&cpv=1
S. Enterprize (Science Journal)
http://smart1234.s-enterprize.com/

In article , Chris Carlen writes:
Greetings:


We use BBO-based optical parametric oscillators with additional
frequency doubling, pumped by 355nm from a pulsed ND:YAG laser to
produce wavelengths in the range of 220nm to 290nm at rather high
energies of 10-30mJ per pulse, with about a 8ns pulse width, and at 10Hz.

The OPO systems are extremely cantankerous since the energies starting
with the YAG pump source, and all the way down the line are right at the
damage thresholds of readily obtainable optics.

The systems work, but break frequently, and require constant fussing and
tweaking to keep the energy output optimized. The slightest
perterbations of temperature, long term surface degradation from high UV
fluences on the optical surfaces, etc. cause the thing to degrade.

We wish there was a better way, but there doesn't seem to be one
commercially available. A custom built system is not yet under
consideration, but might be the right way to go. Unfortunately it would
be very expensive to build, so it might never happen.

I'd like to get some basic understanding of synchrotron radiation. I am
aware that synchrotrons are much more expensive than commercial lasers,
so don't bother pointing that out. If it were a viable radiation source
for our experiments, I would consider applying for access to one of the
existing synchrotron light source labs. Though I sure wouldn't mind it
if we did build one here ;-)

I simply want to know:

1. if the synchrotron radiation that is generated by typical
synchrotrons intended for radiation generation (electron synchrotrons
such as the ALS and others), can be provided in the 220-290nm range?

That's towards the low energy extreme of what is usually done but
there is no essential reason why not. Didn't check details but
off-hand, one of the low energy machines (like the ALS you mentioned
or the VUV ring at the NSLS, in Brookhaven) should be able to cover
this range (especially when coupled with an appropriate undulator).

2. if it is continuous or pulsed, and what is the typical power and
power density (power and beam diameter) for CW systems, or the energy
per pulse, pulse width, and period for pulsed radiation.

Synchrotron beam is always pulsed. The frequencies are high (typical rep
rates in the MHz to tens of MHz range) so for many application the
time structure may be ignored and the beam considered to be CW.
Whether that's true for your application, you'll know best.

As for power, my experience is with much higher energy systems (the
APS, Argonne) where total powers radiated are in the few kW range (per
insertion device), say, up to 10 kW or so, and power densities (at 30
meters from the source) approach 200 W/mm^2. That's non-focused.
With perfect focusing you could, in theory, get to something like 10^5
W/mm^2 but there ain't such thing as perfect focusing. 10^4 is
doable. That's broadband, not monochromatic, mind you.

Now, for lower energy machines, all else being equal, total power
drops roughly proportional to ring energy squared. Power density
(unfocused) drops lie ring energy to the fourth but with focusing you
may be able to get back to E^2. So, the numbers for UV rings may be
two orders of magnitude lower from what I wrote above. But, all else
is usually not equal and you can run a low energy ring at higher current,
getting back an order of magnitude or so.


3. Can it provide very smooth beam profiles?

That's no clear. Do you mean "smooth" as function of energy or as a
spatial distribution?

We do laser induced fluorescence imaging of combustion processes, in
case you are wondering. Typically of NOx, CO, and OH. So far only
qualitative imaging, but we would like to do it quantitatively. This
requires well behaved beam profiles, which our OPOs cannot provide, when
they even emit light in the first place.

Something to consider when you do the comparisons. Synchrotron beam
is broadband. Even an undulator beam will typically have dE/E in the
few percent range. Of course, you can monochromatize it but then the
power numbers come way down. So, the question is whether for your
application it is essential to have a coherent (both longitudinal and
transverse coherence) beam or not. If the answer is "yes", then it is
not at all sure that synchrotron will be an improvement. If it is
"no", than I'm sure it will be an improvement.

Anyway, contact the folks at the ALS and the NSLS. I'm sure they'll be
glad to provide you with more detailed answers

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"