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TJ

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Message 33386 - Posted: 20 Nov 2009, 11:41:04 UTC

Congratulations Dr. T. Desell to a job very well done. An impressive slide show and very nice that Milky Way was a part of your PhD.
This is a milestone in your scientific career and I wish you all the best on your way through science wherever you go.

Good luck also with the hard disks and servers in the coming weeks doctor Trais.

Greetings from,
TJ
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ProfileMartin Ryba
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Message 33424 - Posted: 21 Nov 2009, 3:46:42 UTC

Second the congratulations! Welcome to the club! I know you have a postdoc through next summer...then the real challenge begins. I bailed and went corporate. Good luck Travis!
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ProfileTravis
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Message 34593 - Posted: 16 Dec 2009, 20:03:22 UTC - in response to Message 33424.  

Thanks everyone ;) I'm hoping I get lucky with a professorship somewhere :)
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Cluster Physik

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Message 34664 - Posted: 18 Dec 2009, 14:29:43 UTC - in response to Message 34593.  
Last modified: 18 Dec 2009, 14:30:12 UTC

Congratulations Travis!

You first had the defense and then finished your thesis? I have to do it the other way around ;)

I submitted my thesis earlier today and will defend it in 5 weeks if all goes well. At least that's the plan, the referees have to be fast enough with their reports.
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ProfileGary Roberts

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Message 34675 - Posted: 18 Dec 2009, 23:19:07 UTC - in response to Message 34664.  
Last modified: 18 Dec 2009, 23:20:16 UTC

I submitted my thesis earlier today and will defend it in 5 weeks if all goes well ...

Looks like we'll all be saying, "Congratulations, Dr CP ..." as well :-).

What is your field of research and what is the title of your thesis?

What do you plan to do when all formalities are completed? Enter Academia like Travis or bail like Martin? :-)
Cheers,
Gary.
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Message 34686 - Posted: 19 Dec 2009, 9:32:05 UTC - in response to Message 34675.  
Last modified: 19 Dec 2009, 10:03:46 UTC

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ProfileGary Roberts

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Message 34750 - Posted: 21 Dec 2009, 8:43:44 UTC - in response to Message 34686.  

Thank you very much for your detailed response. I'm sorry if I got you to repeat stuff but I don't think I'd seen all that anywhere else before. That's probably not too surprising as sometimes the bleeding obvious does escape me :-). For instance I hadn't twigged to the identity of one of the authors of the ppam paper until very recently!

Anyway, I'd just like to wish you all the very best for the productive career that obviously lies before you. And Travis too, of course (to bring the thread somewhat back on topic) :-).

Cheers,
Gary.
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ProfileMartin Ryba
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Message 34832 - Posted: 25 Dec 2009, 2:43:40 UTC - in response to Message 34686.  


And there is one now at the NIF (took almost a year for all the security checks before he was allowed to ink his contract ;).


That's not surprising. Los Alamos does do an interesting mix of physics research with international collaborators (such as on NIF) along with super-secret nuclear weapons research (some NIF data feeds that as well, at least according to open sources). Does cause a bit of institutional schizophrenia. For a foreign national to get direct exposure to that environment must take a fair amount of background checking. The Department of Energy has a separate clearance process from the Department of Defense, but where we work people do have to wait many months to get some of the higher level accesses processed. I've had a clearance for nearly 20 years, so it's old hat to me by now. A bit of a culture shock to a recent academic though.

Better is the enemy of the good. -Voltaire
Never ascribe to malice that which is adequately explained by incompetence. - Napoleon
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Matthew
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Message 35114 - Posted: 6 Jan 2010, 18:55:24 UTC - in response to Message 34686.  

Yes, Congratulations to Dr. Travis Desell!

I couldn't help but notice:
What I do is to produce very small helium droplets (smaller than a micron, temperature only 0.37K, they are superfluid!) flying with some 150 mph through a vacuum.


I did a lot of materials research before switching to astrophysics, and I was curious about a few things. Do you use helium-3 or helium-4? I am guessing helium-4, it has a higher superfluid temperature, but in any case, superfluids have exciting quantum mechanical properties; how to you keep the droplets from being destroyed so that you can analyze them? Or is the analysis done while the drop is still moving? Which metals do you use, and are they in a magneto-optical trap (MOT)?

I should just read the publications, lol. Could you link me to them, please? Thanks a bunch!
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Message 35128 - Posted: 6 Jan 2010, 23:13:00 UTC - in response to Message 35114.  
Last modified: 6 Jan 2010, 23:13:58 UTC

I couldn't help but notice:

What I do is to produce very small helium droplets (smaller than a micron, temperature only 0.37K, they are superfluid!) flying with some 150 mph through a vacuum.

I did a lot of materials research before switching to astrophysics, and I was curious about a few things. Do you use helium-3 or helium-4? I am guessing helium-4, it has a higher superfluid temperature, but in any case, superfluids have exciting quantum mechanical properties; how to you keep the droplets from being destroyed so that you can analyze them? Or is the analysis done while the drop is still moving?

Yes, helium-4. One would need much lower temperatures to get helium-3 superfluid. Sometimes one uses helium-3 to compare with a normal fluid and to see what the superfluidity actually adds to a certain effect. But as helium-3 is really expensive, this is done only for quite limited experiments.

But the helium droplets are primary a tool for me. The focus is actually on the atoms, molecules and clusters I put in those droplets. The quantum nature of the helium surrounding has sometimes interesting effects on the embedded particles.
And yes, it is basically a molecular beam experiment, so one does the measurements on the moving droplets. By the way, I just see that I confused a bit my conversion to mph of the speed figure I gave for the droplets (I'm more accustomed to metric units ;). They are actually moving with a speed of roughly 500 to 550 mph.

Which metals do you use, and are they in a magneto-optical trap (MOT)?

I used mainly silver and magnesium (but did experiments with copper, gold, and cadmium, too). But it doesn't even need to be metals. Quite a lot of the experiments with the high power femtosecond lasers are done with the rare gas Xenon.
As we just want the doping material to be picked up by the droplets, there would be no sense in using a MOT. For gases you just let it into a vacuum chamber the droplets pass (in a controlled way and very tiny amounts of course). For solid materials you normally heat them simply in an oven to evaporate them, a very low vapour pressure (10^-5 to 10^-4 mbar, 1.0 torr = 0.76 mbar) is enough. Most materials don't even melt at the needed temperatures, they sublimate enough atoms below their melting point.

I should just read the publications, lol. Could you link me to them, please? Thanks a bunch!

Just search for me on ISI Web of Knowledge ;). Your insitute should have access.

But to directly link a few:

One of the last papers I was involved in (already accepted by Physical Review A, but not published yet) deals with the optimization of femtosecond laser pulses to control the coulomb explosion of clusters. We also used a genetic algorithm, not to fit some streams to the observed stars of the milkyway, but to get the optimal laser pulse shape ;)

Another one shows that several Mg atoms in a single helium droplet exhibit a peculiar behaviour, which is linked to the very low temperature and the formation of a special structure under those circumstances.

The low temperature is again the reason, why we were able to measure some electronic states of silver dimers here, which are not stable at the higher temperatures in "normal" experiments.
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Matthew
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Message 35168 - Posted: 7 Jan 2010, 20:42:20 UTC - in response to Message 35128.  
Last modified: 7 Jan 2010, 20:42:46 UTC

Thanks a bunch, CP! I now have some weekend reading... :)
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