Radiation loss studies on T-10 tokamak using AXUV-detectors - - PowerPoint PPT Presentation

Christian Schlatter Radiation loss measurements with AXUV

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ÐÎÑÑÈÉÑÊÈÉÍÀÓ×ÍÛÉÖÅÍÒÐ RUSSIANRESEARCHCENTER “KURCHATOVINSTITUTE”

Radiation loss studies on T-10 tokamak using AXUV-detectors

Christian Schlatter

Presentation of the diploma work

2003, 28th of March

28th of March 1

Christian Schlatter Radiation loss measurements with AXUV

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Aim and interest of the present diploma work

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⋆ AXUV-detectors were installed on T-10 as fast bolometer for the measurement of the total radiated power ⋆ Precise calibration of the detectors was not performed since the start of the operation of the detectors ⋆ Main task of this diploma work: Calibration and characterization

• f the detectors

⋆ Investigation of different regimes of confinement

28th of March 2

Christian Schlatter Radiation loss measurements with AXUV

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Structure of the presentation

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⋆ AXUV-detectors for radiation measurements ⋆ AXUV-setup and calibration on T-10 ⋆ Radiation loss measurements – Calculation of the total radiated power – Reconstruction of the emissivity profile – Study of fast radiation processes ⋆ Conclusion

28th of March 3

Christian Schlatter Radiation loss measurements with AXUV

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Absolute eXtreme UltraViolet

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⋆ Si-based ⋆ time resolution

• f

2×10−10 s ⋆ high photon sensitiv- ity ⋆ miniaturized ⋆ insensitive to low- energy neutrals (< 500 eV)

28th of March 4

Christian Schlatter Radiation loss measurements with AXUV

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AXUV photon sensitivity

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⋆ flat sensitivity for Eph > 100 eV ⋆ The manufacturer advertises AXUV for applications in the energy range from 7 eV to 6000 eV.

28th of March 5

Christian Schlatter Radiation loss measurements with AXUV

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AXUV low-energy sensitivity hole

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⋆ Two lines of CIII ionization stage and the Dα-line lie in the sensitivity hole. ⋆ But: The radiation at photon energies located in the region

• f reduced sensitiv-

ity is not dominant.

28th of March 6

Christian Schlatter Radiation loss measurements with AXUV

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Limited lifetime of AXUV

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⋆ The stability of sen- sitivity is guaranteed up to a flux of 1016 photons of 100 eV ⋆ The radiation dose was

• ne
• rder
• f

magnitude below this limit for the totality of discharges in 2002.

28th of March 7

Christian Schlatter Radiation loss measurements with AXUV

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16channel AXUV-detector pyroelectric bolometer

Detector setupon T-10

chord resolution inthe centerofthe vessel 4cm timeresolution 10ms timeresolution

• 20

s

28th of March 8

Christian Schlatter Radiation loss measurements with AXUV

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AXUV-detector calibration

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lamp slit AXUV- array pinholecamera

• 200
• 150
• 100
• 50

50 100 150 200 10 20 30

lampposition[mm] ampvoltage[mV]

⋆ The spreading of sensitivity and amplifiers of the individ- ual channels is compensated by weighting factors fi (of or- der of unity), which are mul- tiplied with the detector sig- nals. ⋆ fi were determined in the laboratory using a simple lamp as radiation source.

28th of March 9

Christian Schlatter Radiation loss measurements with AXUV

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Calculation of the radiated power

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• 400
• 200

200 400 710 55 14

topview

• fthe

flange toroidal viewof theflange

⋆ The geometry of the fields of view of the detectors is precisely calculated tak- ing into account the diagnostics flange. ⋆ The absolute power values pi (power radiated power per unit of toroidal length) are calculated using an average sensitivity

• f < η > = 0.24 A/W

⋆ Simple calculation of the total radiated power by P = 2π · R · 16

i=1 pi

28th of March 10

Christian Schlatter Radiation loss measurements with AXUV

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AXUV as fast bolometer

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#32441, Ip = 250 kA, BT = 25 kG, <ne> = 2.6×1013 cm−3 (@ t=700 ms). ⋆ The power loss is dom- inated by tungsten line radiation (flat η region) from the center. ⋆ AXUV and the pyro- electric detector show good agreement for this discharge.

28th of March 11

Christian Schlatter Radiation loss measurements with AXUV

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Checking of the sensitivity hole

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Discharge #34593 without and #34596 with neon gas puffing. ⋆ The neon-puffing started in t = 700 ms (#34596). ⋆ AXUV sees the most intense neon lines (around 30 eV) with a reduced sensitivity of ηneon = 0.18 A/W. ⋆ The calculation of the addi- tional radiation due to neon (with ηneon) agrees with the pyroelectric detector.

28th of March 12

Christian Schlatter Radiation loss measurements with AXUV

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Thin carbon film

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⋆ After operation on T-10, a thin film of probably carbon was deposited on the detectors. ⋆ The color of the film suggests a thickness of at least 70 nm. ⋆ The example of neon puffing showed no decrease in sensitivity at Eph ≈ 30 eV. ⋆ The checking with an He-Ne laser (Eph = 2 eV) did not show a drop in sensitivity at the lower end of photon energy.

28th of March 13

Christian Schlatter Radiation loss measurements with AXUV

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Reconstruction of the emissivity

⋆ The cylindrical symmetry of the discharge is assumed → ε(r) ⋆ The pixels A = {aij} are defined by the intersection of the rings with constant emissivity εj with the ith detector chord of bright- ness gi = 8

j=1 aij · εj

⋆ Reconstruction by εj = A−1gi

method described in: Кузнецов, Щеглов; Методы диагностики высоко-температурной плазмы; Москва, 1974 г.

g1 g2 g3 gi gm 1 2 3 j m

a11 a21 a31 a32 ai1 ai2 aij a22 aii

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Christian Schlatter Radiation loss measurements with AXUV

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An example

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Discharge #31899 (T-10 H-mode regime)

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Christian Schlatter Radiation loss measurements with AXUV

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Deuterium pellet: total power

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28th of March 16

Christian Schlatter Radiation loss measurements with AXUV

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Power lost by low-energy neutrals

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⋆ The power lost by low-energy neutrals can be

• btained

by the difference between the pyro- electric bolometer and the sum of the AXUV-chords.

as suggested in: Boivin et al., High resolution bolometry

• n

the Alcator C- Mod tokamak (invited); Rev. Sci. Inst., 70, (1999).

28th of March 17

Christian Schlatter Radiation loss measurements with AXUV

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Deuterium pellet: individual chords

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28th of March 18

Christian Schlatter Radiation loss measurements with AXUV

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Deuterium pellet: emissivity & Zeff

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AXUV: ZAXUV

eff

(r = 0) = ε(r=0)·Z2

n2

e·R(Te,Z)

Spitzer: < σSpitzer >= 8.7 × 1013 r(q=1)

−r(q=1) dr T 3/2

e

ln Λ 1 Zeff

• 0.29+
• 0.46

Zeff +1.08

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Christian Schlatter Radiation loss measurements with AXUV

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Fast processes : Pellet-Injection

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Discharge #35886

−30 −20 −10 10 20 30 556 556.2 556.4 556.6 556.8 557 557.2 1 2 3 x 10

1

time t [ms] minor radius r [cm] channel power [W/cm]

t1 t2 t3

⋆ D-Pellet injection speed 1 km/s. ⋆ Snakelike radiation pattern. ⋆ t1 = 556.4, t2 = 556.6 and t3 = 556.8 ms.

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Christian Schlatter Radiation loss measurements with AXUV

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Fast processes : Pellet-Injection

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geometryofthesnake

⋆ The q=1 surface is lo- cated at the position of the radiation peak ⋆ The geometry

• f

the snake is a tilted and displaced circle, turning toroidally. ⋆ The corresponding rota- tion speed is 23 km/s.

Wesson, J.A.; Snakes, Plasma Physics and Controlled Fusion, vol. 37, (1995).

28th of March 21

Christian Schlatter Radiation loss measurements with AXUV

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Conclusion

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⋆ Precise calculations and measurements of the geometry of the AXUV-detector diagnostic have been performed. Coefficients for absolute power measurements have been determined. ⋆ The radiated power measured by AXUV was compared to the pyroelectric bolometer signal for many shots and agreement was found when high-frequency line radiation dominated the power losses. ⋆ The emissivity profiles were calculated from the AXUV chord measurements for different regimes of confinement. ⋆ In selected discharges the emissivity profile gave further understanding of the behavior of impurities.

28th of March 22

Christian Schlatter Radiation loss measurements with AXUV

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Conferences

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⋆ Звенигородская конференция по физике плазмы и УТС, 24 – 28 февраля 2003 г.: Д.В. Сарычев, Н.Н. Тимченко, Л.Н. Химченко, К. Шлаттер; ИЗУЧЕНИЕ РАДИАЦИОННЫХ ПОТЕРЬ ПЛАЗМЫ ТОКАМАКА Т-10 С ПОМОЩЬЮ AXUV-ДЕТЕКТОРОВ. ⋆ Upcoming EPS conference in St. Petersburg, 2003:

• N. N. Timchenko, L. N. Khimchenko, D. V. Sarichev, Ch.

Schlatter; Radiation Losses Study on the Tokamak T-10 Using AXUV-Detectors.

28th of March 23

Christian Schlatter Radiation loss measurements with AXUV

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Acknowledgements

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⋆ I’m deeply indebted to Dr. Lenonid Khimchenko and Dr. Natalia Timchenko for the organisation of my diploma work and their excellent support. They sacrificed a lot of their energy to make my stay at Kurchatov institute a wonderful time. ⋆ I’m very grateful to Dmitry Sarychev, Gennady Kirnev, Eugeny Gerasimov, Natalia Kirneva, Viacheslav Budaev and all other working

• n T-10.

⋆ The professors Dr. Yurij Dnestrovskij (Moscow State University) and

• Dr. Minh Quang Tran (Swiss Federal Institute of Technology in

Lausanne) had the gratitude to supervise, analyze and judge my work in plasma physics. I owe them many thanks for going along with it. ⋆ Many thanks to the administration of the Nuclear Fusion Institute of Kurchatov Institute for making this work possible. 28th of March 24