Download - L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal The Plasma Spectroscopy Group
Tangential multi-color “optical” soft X-ray array for fast electron temperature and
transport measurementsL. F. Delgado-Aparicio, D. Stutman, K. Tritz, and M. Finkenthal
The Plasma Spectroscopy Group
The Johns Hopkins University
R. Bell, D. Johnson, R. Kaita, B. LeBlanc and L. Roquemore
Princeton Plasma Physics Laboratory
Princeton Plasma Physics Laboratory NSTX Results/Research Forum
December, 12-17, 2005Princeton, New Jersey, USA
Principles of the “optical” soft x-ray (OSXR) array
20 m CsI:Tl deposition
X-rays from NSTX plasma (vaccum side)
Visible light system (air side)
Fiber optic vaccum window (FOW)
=550 nm Eight, 4x4 mm x 1.5 m long plastic light guides
8" CF
8-4 1/2" CF adaptor
Hard X-ray shield
5 mm Be foil + pinhole
CsI:Tl + FOP + FOW
Vacuum T
X-rays
Visible light
Conversion to visible light OSXR array head tested on CDX-U & NSTX spherical tokamaks (2004)
It’s a system that uses a fast (1 s) and efficient scintillator (CsI:Tl) in order to convert soft x-ray photons (0.1<Eph<10 keV) to visible green light (550 nm).
To discrete channels and light (PMT and/or APDs) amplifiers
vacuum
vacuum
Motivation
• Fast ( 100 s) Te measurements. (ECE-like diagnostic for STs and Tokamaks)
Perturbative electron heat and particle transport (ELMs, pellets, gas-puff and/or SGI).
MHD related Te perturbations (ELMs, MHD-modes, RWMs, FISHBONES/EPMs).
• Perturbative impurity transport. (Gas puff (Ne), Impurity pellets (C, B) and/or SGI)
Our previous work with the USXR and the 1-color OSXR systems have shownthat the measurements proposed are feasible.
• Explore the possibilities of the proposed diagnostic in poloidal configuration.
Viewing the same plasma volumes at three energy ranges. Higher SNR in comparison to diode-based arrays.
How to design a diagnostic to measure Te(r,t)?
SXR filters (e.g. Be 10, 100, 300 m)
X-rays from NSTX plasma (midplane: 0<<0.9)
To fiber optics + PMTs + TIAsEc1
Ec2
Ec3
Tangential multi-color (3) optical soft x-ray (tMC-OSXR) array
Multi-color technique (two-foil method):• The Te measurement is obtained by rationing the localized radiation
intensities from two energy ranges, rather than from an absolute intensity measurement, as is in the case of a single color instrument.
• This design approach naturally eliminates a number of factors that degrade the accuracy of the conventional single color SXR diagnostics for Te measurements.
1, x ph(r)
2,x ph(r)
0, Ec1 kBTe(r) 0, Ec 2 kBTe(r)
Absolute value of the Te(r) by minimization techniques!
Feedback ne(r,t)nZ(r,t)
NSTX tangential “optical” soft x-ray (tOSXR) array
F
H
G
I
I
F
Center stack
R =85 cm0 TFcoil
Rtg00~146.5 cm
Rtg15~84 cm
FOC
8” CF flange with FOW
Soller slits8” CF flange
Filter holders (10, 100 and 300 m)
4”
8”
Baffles
2 cm
Details of the optical head
Filter holder
Baffles
2 cm
Components1. Baffles + filters2. Soller slits3. Scintilator + FOW4. Fiber optics5. PMTs + shield6. Amps7. DAQs
NSTX shot # 117951
What happen with Sn & Te for t [0.2,0.35] ?
150 ms 150 ms
SNR10 um ~ 247SNR100 um ~558 SNR300 um ~ 953
Ip
NBI
RF
Sn
Sn
D
Te0 from tangential line-integrated multi-color ratioTime history of soft X-ray signals
SNR100/10 ~ 171SNR300/10 ~ 196
(RS L-mode)
t1
t2
60 eV
t1
1.6
1.54
Te(r,t) and neutron rates (Sn) crashes
keV
130 eV
t2
1.97
1.84
“First cut”Te(r,t)tOSXR space-time profile
1.3
2.2
keV
“First cut”Te(r,t)tOSXR space-time profile
1.3
2.2
keV
1
2
60 eV
1.6
1.54
5 ms
Fishbone
130 eV
1.97
1.84
5 ms
Fishbone
Te(r) drops: what is preventing the Te0 from peaking?
MHD fishbones affect background plasma during fish<sd
[1] M. F. F. Nave, et al., Fishbone activity in JET, NF, 31, 697, (1991).[2] T. Kass, et al., The Fishbone instability in ASDEX Upgrade, NF, 38, 807, (1998).
[3] S. Günter, et al., The influence of Fishbones in the background plasma , NF, 39, 1535, (1999).
n=1 Fishbones (5 kHz < f < 30 kHz)
1.3
2.2
keV
Observations1. Each fishbone burst affect the Te distribution (Te<0)
only during the phase of largest amplitude of the MHD oscillation, that is ~ 2-3 ms (fish<sd) .
2. The magnitude of the central Te0 is generally correlated with the amplitude of the individual fishbone.
3. The USXR array identifies fishbones as a reconnection-sawtooth-like processeses (but in a slower time-scale in accordance with tOSXR array).
4. Fishbones can also affect impurity density profiles, avoiding their central peaking.
5. ne measured by UCLA reflectometer
6. q0 after the fishbones have disappeared
q0~0.4
q0~0.7
Fishbones in NSTX can lead to a redistribution of Te and nZ similar in form to a sawteeth, but with the plasma parameter
variation occurring on a significantly longer time-scale (fish<sd).
2-4 ms 2-4 ms
D
NS
TX
sho
t # 1
1790
3
• Normalized contour plots of tangentially-line-integrated soft x-ray signals, filtered with Be foils with thicknesses of 10, 100 and 300 m, respectively.
• Shown here is the effect on the soft x-ray intensity of an edge-localized-mode (ELM) occurring at 327 ms
5 ms
1
0.5
0 t1
t2
t1
Type I ELMs study (see also K. Tritz presentation)
Type I ELM Te(r,t) profiles: t1N
ST
X s
hot #
117
903,
t
[0.3
,0.3
5]
5 ms 5 ms
50 eV
850 eV
edge
core
inboard
ELM
Type I ELM SXR and Te(r,t) profiles: t2
50 eV
1050 eV
NSTX shot # 117903, t[0.35,0.4] (Be10/Be300)
6 ms
edge
core
inboard
Future: re-entrant “multi-color” OSXR system?
OSXR array head tested on NSTX
NSTX (07) & NCSX
It’s a system based on the OSXR concept with an optimized plasma access and the capability of recording MHD phenomena from the core to the periphery SIMULTANEOUSLY!
Further work
• Perform the Abel inversions!• Modify the filter holder to enable photometric calibration in absence of foils.• Use 500 m Be foil for increase contrast.• Use transimpedance amplifiers (bandwidth: DC-50 kHz) module behind PMT.• Rotate the tOSXR for better plasma access.
Conclusions1. We have designed, build, installed and tested the prototype version of a tangential
multi-color optical SXR array for fast electron temperature measurements.
2. Line integrated signals enabled the measurement of fast electron temperature profiles in good agreement with the (slow) Thomson Scattering measurements.
3. The tosxr array can work in a variety of plasma scenarios (L-mode & H-mode).
4. However in the cases of strong inhomogeneities in the local plasma characteristics the limitation of the use of line integrated signals become apparent.
Acknowledgments
• The Johns Hopkins University: Gaib Morris, Scott Spangler, Steve Patterson, Russ Pelton and Joe Ondorff.
• Princeton Plasma Physics Laboratory: Mike Bell, Bill Blanchard, Thomas Czeizinger, John Desandro, Russ Feder, Jerry Gething, Scott Gifford, James Kukon, Doug Labrie, Steve Langish, Jim Taylor, Sylvester Vinson, Doug Voorhes and Joe Winston (NSTX).
• This work was supported by The Department of Energy (DOE) grant No. DE-FG02-86ER52314ATDOE