Happy New Year 2013 from SSX!

Happy New Year 2013 from SSX!
Here’s a review of 2012 as well as plans for 2013. It’s hard to believe,
but we’ve been at it for nearly 20 years now (and I’ve been doing these
summaries since 2001). Our very rst vacuum and plasmas were down in the
\research wing” (kind of where the chemistry building sits now). The SSX
mode of operation has been the same all along: we merge high temperature,
magnetized plasmas together at high velocity. Interesting stu has always
happened. We can look locally at small-scale reconnection events (a few cm),
or we can study the evolution and relaxation of large-scale structures (up to a
meter). Lately, we’ve been studying the statistical aspects of these dynamic
events using the tools of uid turbulence ( uctuation spectra like
E
B
(
!;k
)
and correlations after dynamic merging events).
For the last few years, we’ve kept the plasma con ned in a long conducting
pipe called a plasma wind tunnel. Think of it like a conventional air wind
tunnel (maybe smaller than the ones they use for aircraft wings) but the
merging velocity is 100 km/s (as opposed to 100 m/s, or just 220 mph used in
regular wind tunnels), the temperature well over 100,000 K (instead of room
temperature, 300 K), and the uid is a MHD plasma (not just air). Our
densities tend to be higher than earlier SSX con gurations (
n
e
10
15
cm
3
for most of the shot), magnetic eld higher (0
:
25
T
), and our lifetimes shorter.
We have also backed o on the number of magnetic probes (now fewer than
100 in two small quartz shafts, rather than many 100’s in 4 or 12 or 25
stainless steel tubes). In the machine at the moment, we have 4 sets of 48
probes (two are Alexandra’s, one is Ken’s, one is Tim’s).
I guess the big news from 2012 is the departure of Tim Gray after about
4 years at SSX, and the recent hiring of David Scha ner from UCLA. David
will be arriving in a few weeks with his wife Erin. Tim has relocated to
Cleveland, OH. We wish him well! Since Tim left in August, not much has
happened in the SSX lab except preparations for the APS-DPP meeting in
Providence (me, Alexandra Werth ’14, and Ezra Day-Roberts ’13… more on
that below).
The new SSX postdoc David Scha ner is just now defending his PhD
thesis at UCLA. His area of expertise is experimental analysis of plasma
turbulence. He recently had an important paper appear in Physical Review
Letters called \Modi cation of Turbulent Transport with Continuous Vari-
ation of Flow Shear in the Large Plasma Device”. The idea is that he is
able to turn turbulence (and turbulent transport) on and o by modifying
how much the azimuthal ow is sheared. Lots of shear (i.e. di erent layers
moving a di erent velocities) tended to diminish the turbulence. The tools
that David developed at UCLA will have an immediate impact here at SSX.
A scienti c highlight of 2012 was the appearance of our \jets” paper
in Physics of Plasmas, and more exciting is the likely acceptance of Tim’s
selective decay paper in Physical Review Letters, called \Observation of a
relaxed plasma state in a quasi-in nite cylinder”. Tim just responded to
1


 

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