TM_Re: Langmuir - Mirnov joint experiment.eml

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From: Tomas Markovic <markovic6453@gmail.com>
Date: Mon, 22 Apr 2013 14:08:46 +0200
Message-ID: <CAKmn6J3ak051QECUc4ZZGpGuhAKVniN7e8cx9cTqAKqY3cLBJg@mail.gmail.com>
Subject: Re: Langmuir - Mirnov joint experiment
To: =?ISO-8859-1?Q?R=E9fy_D=E1niel?= <refy.daniel@wigner.mta.hu>, "Vojtech
 Svoboda" <svoboda@fjfi.cvut.cz>, <pokol@reak.bme.hu>, Jana Brotankova
	<brotance@gmail.com>, <stockel@ipp.cas.cz>
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This idea to measure poloidal rotation by both probes and Mirnov coils
simultaneously is not something we did on GOLEM before, so it is hard to
tell how will it turn out. Currently, motivation is driven by the fact that
some aspects of rotation detected by Mirnov coils surprisingly seem
correspond to specific findings by rake probe -- namely to
close-to-constant E_r field at plasma edge regions. The arrangement will
need to be flexible. To succeed we need nice magnetic island of low m at
plasma edge (or close to it) -- i.e. low B_tor and high I_p -- have there
been successful rake probe measurements at such parameters? It will also
take some time to find optimal parameters, but island tailoring can be
arranged relatively easily. Also, rake probe should be inserted at the same
time into plasma region while island is there -- however if perturbation of
plasma by probe does not allow for existence of magnetic islands, two or
more shots of same parameters would be necessary -- to get usable data and
to confirm that velocity of rotation is reproducible.

The latter is not trivial thought -- my recent findings are that magnetic
islands on GOLEM accelerate their rotation in presence of external poloidal
field used for control of plasma position.  At least such are findings by
magnetic diagnostics, how is it for probes is not known to me -- we can
investigate on-site. Gomtraic experiments up till now did not use plasma
position control, but we will probably need to use horizontally-oriented
poloidal field to prevent motion of plasma during experiment for better
interpretation of data. However, this might have some impact on signal of
islands -- it seemed to me that islands from when plasma is left alone to
do what it wants were more stable than those detected with stabilisation
winding on...

Basically, we will need 1-2 days (depending on how machine will cooperate).
First, discharge parameters will need to be found where nice and
reproducible island at plasma edge (i.e. known r coordinate) is present --
as well as to identify time of its occurence. Reproducible island will also
enable to investigate, whether plasma rotation changes between shots of
same parameters. Then probe can be inserted into plasma to see if island
will still be there -- if not, separate measurements by probe and magnetic
diagnostics need to be done -- but then relation between velocity by probes
and by magnetics will not be clear. Also, multiple measurements are advised
as data on GOLEM are not always that reliable -- fluctuations and such.
Poloidal field might be used for stabilization of plasma position, or
perhaps not -- could be contraproductive. But it will need to be tried
first. Not to mention that poloidal field windings are not remotedly
controlled.

Basically, it is more of scientific investigation with high cooperation
requirements, than ordinary excercise for students, so if we will go
through with this, Gomtraic participants should be properly prepared as
well.

Regards,
Tomas


2013/4/22 R=E9fy D=E1niel <refy.daniel@wigner.mta.hu>

> Hello guys,****
>
> ** **
>
> First we will have to comment the report, now the export feature of the
> wiki is working, so i will do commenting of the MHD report in pdf, and se=
nd
> it to you for review.****
>
> Second, following the proposal of Tomas, we should make a document which
> describes the idea of this experiment. I am sure about that we already ha=
ve
> documents those describe the basic principles of both measurements, i
> attached 2 files those you already know. Is there a description on the wi=
ki?
> ****
>
> What about the measurement itself? Thomas, could you please write
> something about that! If application of both diagnostics simultaneously i=
s
> possible (i dont know how bad probes disturb the plasma) even toroidal
> rotation could be resolvable from long range correltaion (?).****
>
> ** **
>
> cheers: Daniel****
>
> ** **
>



--=20
Tomas

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<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-=
1"><div dir=3D"ltr">This idea to measure poloidal rotation by both probes a=
nd Mirnov coils simultaneously is not something we did on GOLEM before, so =
it is hard to tell how will it turn out. Currently, motivation is driven by=
 the fact that some aspects of rotation detected by Mirnov coils surprising=
ly seem correspond to specific findings by rake probe -- namely to close-to=
-constant E_r field at plasma edge regions. The arrangement will need to be=
 flexible. To succeed we need nice magnetic island of low m at plasma edge =
(or close to it) -- i.e. low B_tor and high I_p -- have there been successf=
ul rake probe measurements at such parameters? It will also take some time =
to find optimal parameters, but island tailoring can be arranged relatively=
 easily. Also, rake probe should be inserted at the same time into plasma r=
egion while island is there -- however if perturbation of plasma by probe d=
oes not allow for existence of magnetic islands, two or more shots of same =
parameters would be necessary -- to get usable data and to confirm that vel=
ocity of rotation is reproducible.<div>

<br></div><div style=3D"">The latter is not trivial thought -- my recent fi=
ndings are that magnetic islands on GOLEM accelerate their rotation in pres=
ence of external poloidal field used for control of plasma position. &nbsp;=
At least such are findings by magnetic diagnostics, how is it for probes is=
 not known to me -- we can investigate on-site. Gomtraic experiments up til=
l now did not use plasma position control, but we will probably need to use=
 horizontally-oriented poloidal field to prevent motion of plasma during ex=
periment for better interpretation of data. However, this might have some i=
mpact on signal of islands -- it seemed to me that islands from when plasma=
 is left alone to do what it wants were more stable than those detected wit=
h stabilisation winding on...</div>

<div style=3D""><br></div><div style=3D"">Basically, we will need 1-2 days =
(depending on how machine will cooperate). First, discharge parameters will=
 need to be found where nice and reproducible island at plasma edge (i.e. k=
nown r coordinate) is present -- as well as to identify time of its occuren=
ce. Reproducible island will also enable to investigate, whether plasma rot=
ation changes between shots of same parameters. Then probe can be inserted =
into plasma to see if island will still be there -- if not, separate measur=
ements by probe and magnetic diagnostics need to be done -- but then relati=
on between velocity by probes and by magnetics will not be clear. Also, mul=
tiple measurements are advised as data on GOLEM are not always that reliabl=
e -- fluctuations and such. Poloidal field might be used for stabilization =
of plasma position, or perhaps not -- could be contraproductive. But it wil=
l need to be tried first. Not to mention that poloidal field windings are n=
ot remotedly controlled.</div>

<div style=3D""><br></div><div style=3D"">Basically, it is more of scientif=
ic investigation with high cooperation requirements, than ordinary excercis=
e for students, so if we will go through with this, Gomtraic participants s=
hould be properly prepared as well.</div>

<div style=3D""><br></div><div style=3D"">Regards,</div><div style=3D"">Tom=
as</div></div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote"=
>2013/4/22 R=E9fy D=E1niel <span dir=3D"ltr">&lt;<a href=3D"mailto:refy.dan=
iel@wigner.mta.hu" target=3D"_blank">refy.daniel@wigner.mta.hu</a>&gt;</spa=
n><br>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><div lang=3D"HU" link=3D"blue" vlink=3D"purp=
le"><div><p class=3D"MsoNormal">Hello guys,<u></u><u></u></p><p class=3D"Ms=
oNormal">
<u></u>&nbsp;<u></u></p>
<p class=3D"MsoNormal">First we will have to comment the report, now the ex=
port feature of the wiki is working, so i will do commenting of the MHD rep=
ort in pdf, and send it to you for review.<u></u><u></u></p><p class=3D"Mso=
Normal">

Second, following the proposal of Tomas, we should make a document which de=
scribes the idea of this experiment. I am sure about that we already have d=
ocuments those describe the basic principles of both measurements, i attach=
ed 2 files those you already know. Is there a description on the wiki?<u></=
u><u></u></p>

<p class=3D"MsoNormal">What about the measurement itself? Thomas, could you=
 please write something about that! If application of both diagnostics simu=
ltaneously is possible (i dont know how bad probes disturb the plasma) even=
 toroidal rotation could be resolvable from long range correltaion (?).<u><=
/u><u></u></p>

<p class=3D"MsoNormal"><u></u>&nbsp;<u></u></p><p class=3D"MsoNormal">cheer=
s: Daniel<u></u><u></u></p><p class=3D"MsoNormal"><u></u>&nbsp;<u></u></p><=
/div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br><=
div>Tomas</div>


</div>

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