Alexei Petrov, Vladimir Petrov, Massimo De Benedetti, Onofrio Tudisco. 10-Apr-06 ITPA-10 Progress in Development of Time-of- Flight Refractometer for ITER

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Alexei Petrov, Vladimir Petrov, Massimo De Benedetti, Onofrio Tudisco. 10-Apr-06 ITPA-10

Progress in Development of Time-of-Flight Refractometer for ITER

Alexei Petrov, Vladimir Petrov, MassimoDe Benedetti, Onofrio Tudisco (FTU)

2006

SRC RF TRINITI, Troitsk Moscow region, RussiaE-mail: [email protected]

ITPA-10


OUTLINE

SPECIFIC FEATURES

PROBLEMS, TASKS

PROGRESS

RECENT EXPERIMENTS, STATUS

CONCLUSION, PLANS, TASKS


A robust measurement of line integrated electron density (without fringe jumps) needed for many application, in particular for real time control. Measure time delay

SPECIFIC FEATURES

•Unambiguous line int. density for feedback control

•Microwave pulse - just above Xl cutoff freq. from LFS:

single or double pass

•ITER– using transparency window on X-mode in low

frequency band (60 – 100 GHz): to avoid “first mirror”

problem

•Less sensitive to the reflection surface quality

l

g dzznd

d)(

)(


• SNR – long distances, long waveguides, accuracy of measurements ~

• Refraction – attenuation, change of wave trajectory- need ray-tracing/(Full wave-analysis) to take into account

• Additionally, for high Te (45keV) regimes: absorption, relativistic effects). Transparency window – 60-80-100 GHz - ?

• Choose of probing geometry: double- or single pass

• Multi-freq. probing to avoid profile dependence

• Experiments on tokamaks

• Integration with ITER-chamber, LFS-X reflectometer (76-220 GHz; F.02 system, Eq#11)

PROBLEMS, TASKS -1

SNR/1


SNR – accuracy of measurements:

• Optimization of probe geometry, optimization of antenna-

waveguide system, use scheme with low-noise microwave

amplifier, measure time delay by phase measurements

• Probe geometry:– 1. Double-pass (DB).

• Pro - use only LFS antennas.

• Contra –absorption higher. Influence of refraction larger?

– 2. Single pass (SP), using HFS antenna and LFS antenna.• Pro – absorption less.• Contra – complicate HFS antenna system.

Compare two systems: k = P1/P2 ~ A1·L22/A2·L1

2, A1~ 9*9 cm2, A2~9*1 cm2; L1~2·(2a+l), L2~(2a+l). k~10 dB (DB - better), w/o absorption and refraction

PROBLEMS, TASKS - 2


Integrated absorption for equatorial trajectories at different frequencies (60-100 GHz) and Te values (25-45 keV), ne(0) = 1.03·1020 m-3

- 50dB (single pass)

- 10dB

- 0.4dB

dle

dle

Total single pass transmission:

G. Vayakis, J. Sánchez, ITPA-6Absorption, choice frequenciesPROBLEMS, TASKS - 3

At least 3 freq. in a range 60-78? GHz to secure immunity to density profile, 95-96 GHz – up to 25 keV

Reference Te profiles

~4.7 dB


PROGRESS - 1SNR• 1. Development of the prototype of a receiver for a refractometer

with a pulse microwave amplifier (PMA) based on a IMPATT-diode (SNR): – Frequency 60.0±0.5 GHz– Gain >20 dB– Noise <5 dB– Net effect – 15 dB

• 2. Improved prototype of a time delay measurements unit with a fast peak detector (PD) - enhanced accuracy of time delay measurements (for low SNR), net effect - 2-3 times better accuracy

• 3. Method of a double-frequency differential refractometry (DFR) for time delay measurements is offered and tested in T-11M (higher SNR, sensitivity) [1,2] (CW, net effect +10 dB and more)

1221

,

)(d

dOgr

Measurements of phase shift between 2 waves with close frequencies (fringe jump-free) : 1 2, 12 < 2

[1]. V. Petrov et al. Plasma Physics Reports, 2006, Vol. 32, No. 4, p. 317.[2]. V. Petrov et al. Instr. and Exper. Techn., 2006, Vol. 49, No. 2, p. 238.


RECENT EXPERIMENTS - 1•Experiments in tokamaks – T-11M, FTU

T-11M FTU ITER

BT [T] 1.2 5.0– 8.0 5.3

R [м] 0.70 0.935 6.2

a [м] 0.2 0.305 2.0

R/a 3.5 3.07 3.1

Ne [м-3] 0.5*1020 >1*1020

TokamakParameter

Te [keV] 0.5 10-12 15

• Testing 60 GHz prototype of refractometer (X-mode) in ITER-like conditions on the FTU tokamak (Frascati, Italy)

>1*1020


The behavior of cut-off and ECE frequencies on FTU for typical plasma parameters

N= N0(1-2)

Transparence window on FTU: f =50-120 GHz

N0 f flc

B0 f flc fuc

B0 > 3.5 T needed

•Experiments in tokamaks – FTU

RECENT EXPERIMENTS - 2


• MO – microwave oscillator, I-isolator, DC-directional coupler, PCS- pulse current source, A1, A2 – amplifiers, D1, D2 – detectors, PD – adaptive threshold pulse discriminator, TVC – time-to-voltage converter

•Experiments in tokamaks – T-11M, FTU

P ~ 200 mW, tpulse = 5 ns, tfr < 2 ns, f (PRR) ~ 500 kHz



CO2/CO

interferometer


•Experiments in tokamaks – FTU, geometry and picture

Refractometer

Antenna system of ECE and reflectometer for the firstexperiments in FTU, antennae directed along minor radius – refraction minimal

Signal detector with pulse amplifier

Pulse microwave oscillator

Electronic unit for signal handling (PD)


Time delays ~1.5 nsNow accuracy ~10 ps (~1 ms time resolution)

Sensitivity of density measurements ~ 1.5 ns/1020 m-3. Lower density limit: 0.7% of max density.

The behavior of the calculated time delays for X-mode versus density for typical plasma parameters

N= (N(0)-N(a))·(1-2)N(a)

J= J0(1-2) = q(a)-1

Ip = 500 kABt = 6 T<N> = 0.8

Time delay, ns

RECENT EXPERIMENTS - 5•FTU experiments


Raw data of TFR: Time delay (code ADC) versus shot time for the typical shot # 27992 (Bt = 6 T, Ip = 500 kA, Ohmic heating


Time, ms

ADC, code

0.8ns

Mean density, 1020 m-3: Refractometer (blue) and Interferometer (red) for the shot #27982

Time, s

0.8

0.4

FTU experiments


Mean density: Refractometer (blue line)and Interferometer (red) for the shot #27983


Cut-off at the density 1-1.1•1020 m-3;Adequate density measurements up to cut-off

Time, s

Mean density1020 m-3

FTU - Reflectometry regime

1

1

-3

Time, s

Td, ns


Blue – refractometerRed –IR-interferometer (22.5 cm)


Time, ms

Mean density, a.u.


Integration in ITER:

STATUS -1

Eq#11

•TFR probing geometry is part of HFS/LFS antennae-wave guide system (A. Malaquias)


E11 DIAGNOSTICS packageE011 Port Cell P15

E05 E05-X-Ray Crystal Spectrometry (Survey) P07

E03 E03-VUV Spectroscopy (main & divertor) P04

F02 F02-Refl, Doppler Reflectometry & Refractometry P10

E08 E08-Neutral Particle analyser (NPA) P15N01 N01-In-Vessel Diagnostic Services P14N02 Equatorial BSM Bl-xxxN03 N03- Diagnostic Port Plugs & First Closures P14N04 N04-Interspace Blocks and Second Enclosures P14N06 N06-Ex-Bioshield_ Electrical Equipment P14N07 N07-Window assemblies P31

Eq#11

C.I.Walker, et.al, ITPA-6

STATUS - 2


1. Development of the prototype of a receiver with a pulse microwave amplifier (PMA) based on a IMPATT-diode (SNR): + 15 dB.2. Improved prototype of a time delay measurements unit with a fast peak detector (PD) - enhanced accuracy of time delay measurements (for low SNR), net effect - 2-3 times better accuracy 3. Method of a double-frequency differential refractometry (DFR) for time delay measurements is offered and tested in T-11M. +10 dB and more.4. Testing of TFR in ITER-like configuration (X-mode, double-pass horizontal probing, the same frequency) has been performed successfully in FTU. The first measurements of plasma density with TFR on X-mode have been performed, up to the cut-off density, influence of refraction is low for reflectometry type antenna system (looking along density gradient).Good signal-to-noise ratio is obtained with time resolution of ~50 s

CONCLUSION, PLANS, TASKS -1


Density measured by TFR corresponds to the one measured by interferometer (along vertical chord) within 10%.

Double-pass scheme of TFR is preferential.

Plans: to proceed testing of TFR in different regimes of FTU (ITER-relevant regimes), to develop algorithms of data elaboration (refraction, relativistic effects), hardware modernization (ADC, signal handling electronic);

test measurements in JET (D-shape large plasma);

testing in T-11M of prototypes of TFR;

development of multifrequency prototype;

Tasks.

•Integration in ITER.

•Study influence of refraction – experimentally and numerically.

CONCLUSION, PLANS, TASKS - 2

Documents

Alexei Petrov, Vladimir Petrov, Massimo De Benedetti, Onofrio Tudisco. 10-Apr-06 ITPA-10 Progress in Development of Time-of- Flight Refractometer for ITER