Multi-energy SXR imaging for magnetically confined fusion studies

NSTXNSTX APS – April 2010, Washington, DC– ME-SXR imaging (Delgado-Aparicio) February, 12-17th, 2010

Multi-energy SXR imaging for magnetically confined

fusion studies

Multi-energy SXR imaging for magnetically confined

fusion studies

Luis F. Delgado-AparicioPrinceton Plasma Physics Laboratory

APS – April meeting, Washington, DC, USAFebruary, 12-17, 2010

College W&MColorado Sch MinesColumbia UCompXGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton UPurdue USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU IllinoisU MarylandU RochesterU WashingtonU Wisconsin

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAEAHebrew UIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

POSTECHASIPP

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech RepU Quebec

NSTXNSTX Supported by

NSTXNSTX APS – April 2010, Washington, DC– ME-SXR imaging (Delgado-Aparicio) February, 12-17th, 2010 2

In collaboration with…

K. Tritz, D. Stutman, M. Finkenthal and D. Kumar

Plasma Spectroscopy Group (PSG)The Johns Hopkins University (JHU)

M. Bitter and K. HillPrinceton University Plasma Physics

Laboratory (PPPL)


Outline

1. Introduction and motivation

1. Main diagnostic and multi-energy technique

2. Applications

1. Diagnostic improvements and development of new edge and core systems

1. Summary


Magnetic fusion schemes = harsh environment

Tokamak(toroidalnaya kamera – magnitnaya katushka)

Plasma measurements in harsh environment are quite a challenge

1. Hot plasma temperatures

2.Fast charged particles

3.Strong plasma currents

4.High magnetic fields & EM-noise

5.100’s keV – MeV ions

6.MeV neutrons

7.Gamma rays


Motivation for the development of Multi-Energy Soft X-ray (ME-SXR) systems

1. The motivation for the construction of ME-SXR arrays is the development of versatile diagnostics which can serve a wide range of MCF experiments for a number of critical simultaneous profile

measurements.

2. Useful in a wide variety of applications.

1. Compared to magnetic measurements at the wall, the ME-SXR technique has advantages for low-f MHD detection, such as spatial

localization and insensitivity to stray magnetic fields.

1. Evaluate discrepancies between Thomson Scattering and Electron Cyclotron Emission diagnostics for electron temperature

measurements


Outline



2. Applications


1. Summary


1st prototype: multi-energy “optical” SXR array

L. Delgado-Aparicio, et al.,

RSI, 75, 4020, (2004).

JAP, 102, 073304 (2007).

PPCF, 49, 1245 (2007).

NF, 49, 085028, (2009).

NSTXTopview

Magnetic

axis

(core)


“Description” of multi-energy/multi-color technique

Probe the slope of the continuum:

Synthetic X-ray Spectrum


1st prototype: multi-energy “optical” SXR array

L. Delgado-Aparicio, et al.,

RSI, 75, 4020, (2004).

JAP, 102, 073304 (2007).

PPCF, 49, 1245 (2007).

NF, 49, 085028, (2009).

NSTXTopview

Magnetic

axis

(core)


Principle 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

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 detectors (PMT, APD, Image intensifier)

+ (RC/TIA) amplifiers

Conversion of XUV emission to visible light

X-rays from NSTX plasma(vacuum side)

Fiber optic vacuumwindow (FOW)20 m CsI:Tl

deposition

Visible light system(airside)=550 nm


Outline



2. Applications


1. Summary


a) Plasma heating using RF waves

• Laser-based TS system probes

the plasma every ~ 16 ms.

• Three ME-SXR emissivities appear

to be different (different sensitivity

to ne and Te).

• Fill in between Thomson scattering

measurements!


Te0~4keV in between Thomson Scattering time slices

L. Delgado-Aparicio, et al., JAP, 102, 073304 (2007).

L. Delgado-Aparicio, et al., PPCF, 49, 1245 (2007).

• Fill in between Thomson scattering

measurements!

• Error bars: 50-80 eV

• Application to RF heating heat

deposition studies.


b) Impurity transport is one of the challenges facing the current fusion research

For instance: Tungsten, is an attractive candidate as fusion wall material due to its very high

melting point and high thermal conductivity.

Nevertheless it can melt within one millisecond when in direct contact with the plasma.

ITER tungsten walls


Adding an extrinsic impurity for transport studies

15


Example: ion-gyroradius scan at fixed q-profile

Ne puff Ne puff Ne puff

L. Delgado-Aparicio, et al., PPCF, 49, 1245 (2007).


Reproducible properties in subsequent plasmas

Plasma current, NBI heating and q-profile

Controlled experiment reproduced elongation and triangularity


Example of experimental and simulated SXR profiles

L. Delgado-Aparicio, et al., Nucl. Fusion, 49, 085028, (2009).


Penetration of impurities changed at high fields



Experimental diffusivity in good agreement with theoretical models


Note large increase in Dneo and Dexp at r/a>0.8


Convective velocity changes sign with BT


VZ<0 at r/a>0.5 at low-field is anomalous instabilities?⇒


c) Resistive Wall Mode (RWM) research in NSTX

• RWM is an external kink modified by presence of resistive wall.

• RWM Characteristics:

– slow growth: 1/≲ wall

– slow rotation: fRWM 1/2≲ wall

– wall~5-10 ms

– stabilized by rotation & dissipation

• High toroidal rotation passively stabilizes RWM at high-q.

• RWM can affect both the outer and inner plasma.

• Long-pulse, high-N requires stabilization.(interior view)(exterior view)

S. A. Sabbagh, et al., NF, 46, 635, (2006).

RWM RWM

Sensors (BSensors (Brr))

RWM activeRWM active

stabilizationstabilization

coilscoils

PassivePassive

platesplates

RWM RWM

Sensors (BSensors (Bpp))


Actively-stabilized RWM plasmas show n=1 mode


ME-SXR reconstructions indicate n=1 stable mode

Fast SXR-based Te(R,t)

measurements

L. Delgado-Aparicio, et al., to be submitted, NF (2010).


d) Pressure -collapse and plasma recovery

• Three ME-SXR emissivities have different sensitivity to ne and Te.

•All arrays are sensitive to the peripheral and core Te crash.


Fast Te(R,t) estimate for -collapse

• 0th order approx. since collapse is not axysimmetric.

• Te,core~200 eV , Te,mid-radius~600 eV and Te,edge~300 eV.

L. Delgado-Aparicio, et al., to be submitted, NF (2010).


Outline



2. Applications


1. Summary


Room for “desirable” improvement

28

1. Increase spatial resolution (from present 4 cm to 1 cm)a) Particle transport at the edge: D~q2

b) Resolve edge plasma profilesc) Observe cooling of NTM O-points.

2. Increase spectral resolution (# of SXR filters)a) Better constraint for Te(R,t) measurements.

b) Thinner filters will allow measurements/imaging of pedestal & gradient region using continuum & line emission.

3. Increase number of ME-SXR cameras for study of non-axisymmetric perturbations (3D-effects).


Benefits of optical-based SXR array• High spatial resolution (~1 cm)• Spatial oversampling• Filter/energy band versatility• Simple design and components

29

Edge optical-based ME-SXR system under construction for NSTX (2010 run)

K. Tritz (JHU)


Alternative: edge diode-based fast (>10 kHz) system

Benefits of diode-based SXR array• High dynamic range• High bandwidth• Modular components• Compact detector and electronics

K. Tritz (JHU)


• Pilatus: PIxelated Large Area detector.

• Dectris - Pilatus 100k Module (~100k pixels)1. Sensor: Silicon (320 m) diode array.

2. Pixels: 172x172m2 (487x195)

3. Parameters are adjustable on a per-pixel basis•Amplifier, shaper and lower level discriminator•Energy Range: 2.5 - 20 keV•Area: 8.4 x 3.4 cm2

•Count Rate/pixel: < 2x106 x-rays/s•Min readout time 2.54 ms•Latest version of Pilatus, called “EIGER” has 75 m

pixel size and ~24 kHz framing rate capability with only 1 s dead time between frames.

31

Core diode-based system for C-mod & NSTX

Pilatus pixelated photon-counting detectors enable new diagnostics ~8cm

K. Hill & M. Bitter (PPPL)


Pilatus “pinhole camera” can measure spatially resolved broad-band soft x-ray spectra, 2-20 keV

Concept:

• Energy resolution ~500 eV FWHM

• Example: Emin= 2 keV, 2.5, 3, 3.5, 4, 5, 7, 10 and 14 keV.

• Few columns (5) at low-energy, where count rate is high and many columns (50) at high-energy where count rate is lower.

• Sum 487 rows vertically to form 49 spatial sightlines and improve statistics.

Aplications:

• Poloidal tomographic reconstructions.

• Model Max. continuum + lines emission.

• 2D picture of Te, Zeff, nmetals.

• Electron thermal and impurity transport.

• Easy to adapt to different tokamak sizes.K. Hill & M. Bitter (PPPL)


Summary

1. The motivation for the construction of ME-SXR arrays is the development of versatile diagnostics which can serve a wide range of MCF experiments for a number of critical simultaneous profile measurements.

2. Useful in a wide variety of applications: a) RF heating, b) particle transport, c) thermal transport and d) a variety of MHD events.

3. Compared to magnetic measurements, the ME-SXR technique has advantages for low-f MHD detection, such as spatial localization and insensitivity to stray magnetic fields.

4. The use of thinner filters will allow imaging and measurements of pedestal & gradient regions using continuum and impurity line-emission.

5. Recommend the use of few ME-SXR cameras (tangential/poloidal views) in multiple toroidal locations for study of non-axisymmetric perturbations.


Acknowledgements (I)

The Johns Hopkins University (JHU) Plasma Spectroscopy Group (PSG)

K. Tritz, D. Stutman, M. Finkenthal and D. Kumar

Princeton University Plasma Physics Laboratory (PPPL)

R. Bell, M. Bitter, W. Blanchard, E. Fredickson, S. P. Gerhard, K. Hill, J.

Hosea, R. Kaita, S. Kaye, B. LeBlanc, J. Manickam, J. Menard, C.

K. Phillips, L. Roquemore, W. Solomon and B. Stratton

Columbia University (CU)S. A. Sabbagh, J. Berkekey,J. Bialek and J. Levesque

Oak Ridge National Laboratory (ORNL)

R. Maingi, J.M. Canik and A.C. Sontag

Nova PhotonicsH. Yuh

University of Wisconsin-MadisonF. Volpe


Acknowledgements (II)

• The Johns Hopkins University: Gaib Morris, Scott Spangler, Steve Patterson, Russ Pelton and Joe Ondorff.

• Princeton Plasma Physics Laboratory: Bill Blanchard, Patti Bruno, Thomas Czeizinger, John Desandro, Russ Feder, Jerry Gething, Scott Gifford, Bob Hitchner, 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

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Multi-energy SXR imaging for magnetically confined fusion studies