4 of 5
4
New developments?
Posted: 08 February 2012 11:15 PM   [ Ignore ]   [ # 46 ]
Old Timer
Avatar
RankRankRankRank
Total Posts:  257
Joined  2011-11-04

Be wary of Boron nitride. I’ve used it in plasma facing conditions before and it turns to powder pretty easily.  I have no experience with silicon nitride or zirconia.  Best of luck.

Profile
 
 
Posted: 08 February 2012 11:18 PM   [ Ignore ]   [ # 47 ]
Administrator
RankRankRankRank
Total Posts:  310
Joined  2006-05-22

Interesting—I have seen reports of it in plasma condtions. Might depend on how it is made, but I’ll make sure to check if the supplier has any plasma applications.

Profile
 
 
Posted: 08 February 2012 11:36 PM   [ Ignore ]   [ # 48 ]
Old Timer
Avatar
RankRankRankRank
Total Posts:  257
Joined  2011-11-04

In my limited experience with it, boron nitride works well in quasi steady state plasma conditions like glow discharges.  When I used it in pulse discharges (~100 A, a few microseconds) it visibly eroded in a short period of time and nitrogen showed in interesting places.

Profile
 
 
Posted: 09 February 2012 12:19 AM   [ Ignore ]   [ # 49 ]
Administrator
RankRankRankRank
Total Posts:  310
Joined  2006-05-22

hmmm…Does not sound promising.  I wonder how we can safely test any of these three possibilities. If we just leave a smaple at the bottom of the chamber, it won’t get exposed to anything near the energy density at the insulator. Unless we put it in the way of the beam, which is hardly a fair test.

Profile
 
 
Posted: 09 February 2012 12:33 AM   [ Ignore ]   [ # 50 ]
Old Timer
Avatar
RankRankRankRank
Total Posts:  257
Joined  2011-11-04

You could try putting samples parallel to the plasma flow between two cathode rods near the top of the cathode rods.  You could mount 4 samples and try the three proposed insulators and alumina.  It might not be the fairest test but it would be apples-to-apples.  If you test it with the ion beam or electron beam you need to use samples at least 0.25” thick.  I put ceramics in the base of the anode for some experiments and thin sheets will crack easily under the stress of either beam.  Alumina fairs very well in the tests I’ve completed.

Profile
 
 
Posted: 12 February 2012 09:29 PM   [ Ignore ]   [ # 51 ]
Old Croaker
Avatar
RankRankRankRankRank
Total Posts:  551
Joined  2009-12-13

Does the stress manifest the same way as heat-stress on glass?
this is due to relatively high coefficient of expansion on heating, versus the low overall heat conductivity.

borosilicate glass is therefore used in laboratory glassware, since it has a much lower coefficient of expansion.

when i look at the chemistry of this, it seems that to improve heat stress,
stuff is added to the glass that has negative coefficient of expansion, and this relieves
the overall expansion stresses.

Profile
 
 
Posted: 12 February 2012 11:22 PM   [ Ignore ]   [ # 52 ]
Old Timer
Avatar
RankRankRankRank
Total Posts:  257
Joined  2011-11-04

In the case of plasma shock behind the insulator, it is more like taking a hammer to the insulator than a heat stress.  The impact happens on a time scale much faster than the time to transfer heat into the material.  We saw evidence of plasma chemistry on the inside surface of the insulator.  The alumina discolors slightly from pristine white to a stained yellow.  It remains a hypothesis but the data at the 0.25 MA scale seems to support it.

Profile
 
 
Posted: 03 April 2013 05:11 PM   [ Ignore ]   [ # 53 ]
Old Croaker
Avatar
RankRankRankRankRank
Total Posts:  551
Joined  2009-12-13

found this interesting composite material, containing barium titanate nanoparticles, coated in a plastic.
http://apl.aip.org/resource/1/applab/v95/i13/p132904_s1

Profile
 
 
Posted: 05 April 2013 06:04 PM   [ Ignore ]   [ # 54 ]
New Friend
RankRank
Total Posts:  23
Joined  2011-05-23

I see a lot of science getting tossed around, cool :]

If someone could draw up a diagram of a geometry I can throw it in CAD real quick and run a finite element simulation to determine flashover. I can try with a few of the different materials proposed as a basis for model properties…

Profile
 
 
Posted: 14 May 2013 09:50 AM   [ Ignore ]   [ # 55 ]
Newbie
Rank
Total Posts:  4
Joined  2013-05-14

So, any updates for LPPX?  It’s been over two months now.  Just wondering.

Thanks in advance.

Profile
 
 
Posted: 14 May 2013 10:01 AM   [ Ignore ]   [ # 56 ]
Administrator
Avatar
RankRankRankRank
Total Posts:  142
Joined  2006-08-01

We’re putting the finishing touches on the new report now.

Profile
 
 
Posted: 15 May 2013 07:41 PM   [ Ignore ]   [ # 57 ]
Newbie
Rank
Total Posts:  4
Joined  2013-05-14

Just saw the update, very cool!  Hope the change to iridium wire works well and eliminates the metallic contamination.

Profile
 
 
Posted: 16 July 2013 08:05 PM   [ Ignore ]   [ # 58 ]
Newbie
Rank
Total Posts:  4
Joined  2013-05-14

It’s that time again!  Any updates?  Has the scheduled monthly updates been changed to every so often?  Just asking.  Thanks!

Profile
 
 
Posted: 19 July 2013 12:32 PM   [ Ignore ]   [ # 59 ]
Old Timer
Avatar
RankRankRankRank
Total Posts:  130
Joined  2006-08-14

Thanks for checking in—The highlight of the next progress report is our visit to Google last month, but we are waiting on the big G to post the video of Eric’s talk(s) (there were two, one general and one technical) on their “Solve For X” website.  We did hear by the end of this week, and it’s Friday, so stay tuned…...

Profile
 
 
Posted: 19 July 2013 10:46 PM   [ Ignore ]   [ # 60 ]
Newbie
Rank
Total Posts:  4
Joined  2013-05-14

Awesome, can’t wait to see it and read the report.

Thanks

Profile
 
 
   
4 of 5
4