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