status of a programme for development of iter relevant diagnostics onftu

F P Orsitto 12 ITPA princeton 26-30march07

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Status of a programme for development of ITER relevant diagnostics onFTU

Francesco Paolo Orsitto

ENEA Frascati(Italy)


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motivations

• Because of the relatively harsh environment of ITER, the implementation of diagnostics on the machine is a major challenge, arguably the most difficult ever undertaken in plasma diagnostics. New diagnostic techniques, components, sensors etc, which are better suited to the environment, are needed. These have to be developed and validated on today’s tokamaks.

• FTU is a medium sized device (BT≤8T,Ip=1.6MA,R0=0.93m/a=0.33m,Paux=4.6MW)

• some of the FTU parameters similar to ITER :

density( nemax > 1 10 20 m-3), power load( P ~10MW/m2) , plasma temperature (Te > 10keV, in scenarios with central ECRH heating), magnetic field 4<BT<8T.

• FTU is well placed to contribute to the development of some new

ITER relevant diagnostic techniques and components.


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Present status of activity

• 1st meeting ( 28 nov 2005) : general discussion of proposals • 2nd meeting (31 march2006) : presentation and discussion of

technical details of the proposals already discussed in the 1st meeting.

• 3rd meeting (28 june 2006):presentation of the proposal to the ENEA management

• Presentation to ITPA TG Dia for advice and collaboration( sept 06)• Discussion inside programme committee FTU (Jan07)• Discussion on management of the programme(Feb07)


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Diagnostics discussed

• First mirror test ( G Maddaluno)• Thermography( G Maddaluno)• Techniques of detection of dust by scattering(C Castaldo/E

Giovannozzi)• CVD diamond detectors for UV(M Pillon/M Angelone)• Fast wave reflectometry (R Cesario / A Cardinali)• Proposal for evolution of Collective Thomson scattering of FTU in

ITER relevant direction ( U Tartari)• Refrattometry to measure the line integral of density( O Tudisco)• Detector GEM to measure X-ray on ITER( D Pacella/ G Pizzicaroli)• Real Time diagnostic system for detection of precursors and

reaction to disruptions and fast events of plasma( C Neri, B Esposito, M Riva)

• Test of a polarimetric system for ITER( S Segre)


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Priorities

• First mirror test ( G Maddaluno)• Fast wave reflectometry (R Cesario / A

Cardinali)• Refrattometry to measure the line integral of

density( O Tudisco)• Detector GEM to measure X-ray on ITER( D

Pacella/ G Pizzicaroli)• Proposal for evolution of Collective Thomson

scattering of FTU in ITER relevant direction ( U Tartari)


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First Mirror Test (I)G Maddaluno, M Di Fino,M Montecchi, E Nichelatti,E Serra

• Specific features: FTU is a metallic device Mo wall

• Wall load >10MW/m2.

• The absence of carbon makes interesting the comparison of exposure of mirrors with results obtained in non-metallic devices and very useful for ITER scenarios.


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First mirror test(II)

• Experimental system:• It is proposed to use the system for sample

introduction which is operating on FTU port#8bottom.

• The max diameter of a sample to be exposed is =25mm

• On axis with respect to this system and on the upper port#8 and optical window is available which could be used for a possible real time monitoring of erosion /deposition.


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First mirror test (III)

• A facility for construction of mirrors is available at ENEA-Frascati ,

• Optical tests could be carried out at ENEA Casaccia Labs( North Roma) where equipments are available for measurements of optical figures like reflectance vs wavelength, planarity, roughness.


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Manufacture, characterization and exposure in TEXTOR of Rh-coated molybdenum mirrors

Abstract presented at the 34° EPS conference:

Tests of rhodium -coated molybdenum first mirrors for ITER diagnostics

G. Maddaluno, M. Di Fino , F. Orsitto , A.Rufoloni , M. Montecchi , E. Nichelatti , E. Serra , A. Litnovsky , G. Sergienko , G. De Temmerman , L. Marot

ENEA mirror

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Rh theoretical mirror #1 mirror #3 mirror #4

In the frame of EFDA task TW5-TPDS-DIADEV

TEXTOR mirror holder


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Comparison between pre- and after-exposure (to 19 high power NBI-heated

discharges) hemispherical reflectance of ENEA Rh-coated Mo mirror

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Rh theoretical mirror #1 mirror #1 (after use)


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Techniques for detection of dust by scatteringC Castaldo,E Giovannozzi(ENEA Frascati);S Ratynskaia(MPE Garching);

U de Angelis ( Univ of Naples); C Marmolino ( Univ of Molise)

• Aim : measurement of size and concentration

• Theory of Scattering Lorentz-Mie is used

• A Thomson scattering system is proposed


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Proposed Laser light elastic scattering scheme

Collection optics (to APD & ADC)

Parabolic & planeRh-Cu mirrors

≈ (h/h)2/2 ≈ 5 msr

≈ /4h ≈ cm

h ≈ cm

60 Hz Nd:YAG laser beam (TS FTU) 1.5 J, 20 ns, 1.064 m

Scattered photons by spherical particle(radius a, refractive index m)Nph ≈ Q a2 () (/sb) (/hc)

Laser Beam sb ≈ 1 mm2

Nph ≈ 1010 Q a(m)2

Q = Q(, a, m)


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Preliminary results

Example of signals due to dusts present in FTU after a disruption.

A signal is clearly present in the channel looking at the laser wavelength, and on the other spectral channels, after the end of the plasma current.

The signal at the laser wavelength for the central channels. All signal are in counts.


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Percentage of discharges with dust

Percentage of discharges with dust seen by the Thomson scattering following a disruption.

Only the first 0.5 seconds after disruption has been taken into account.Only 7% of the discharges is without dust (as measured by the Thomson scattering).

1322 discharges with a disruption occurring after more than 300 ms from the start of the plasma has been selected.

The average dust density is about107 m-3.


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Temporal behaviour

Normalized number of dust particle in the first 500 ms after disruption compared to the amount of dust in the following 500 ms.

The number of dust particles is decreasing in time.


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Spectrometer 12 (central)

Distribution of Particle radii assuming the Rayleigh approximation.

Discharges with a dust content less than 0.1 (in order to minimize the chances of a double hit) ha been selected.

The data are well approximated by a power law with a slope of = 1.8.The value of 2 ~ 10-4 is inside the Rayleigh approximation (The average value of the laser power has been used).


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Proposal for evolution of Collective Thomson scattering of FTU in ITER relevant direction

U Tartari, G Grosso, G Granucci -IFP CNR Milano

• A gyrotron based CTS system is installed on FTU and operating .

• Working at fgyr<fECE : this configuration is proposed for ITER ( F Orsitto,G Giruzzi Nucl Fus 1997, Bindslev,Meo,Korsholm Feas.Study CTS for ITER 2003, Meo et al RSI 2004, EPS2005 Tarragona, and ITPA meet Culham2005)

• Gyrotron used : 140GHz Gycom• The ITER relevant configuration (i.e. fgyr<fECE) can be

realized only on a device with high magnetic field like FTU.

• Geometry : 90° scattering angle • Aim: measurement of Ti


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proposal

• Proof of principle of CTS in X-mode • At high density• Using the ITER configuration • On thermal plasma to measure Ti• On plasmas with non-thermal ions ( when a H beam will

be installed on FTU)• With new ( receiving and transmitting) antennas

designed to prevent breakdown inside the port.• 1° phase :In the present configuration and with 140GHz

gyrotron and • 2° phase: using a 60GHz gyrotron ( and at B=5T) as a

true prototype of a ITER CTS system


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Refrattometry to measure the line integral of densityA. Petrov(1), V. Petrov(1), A. Malishev(1),

M. De Benedetti, O. Tudisco(2)(1) Triniti, Moscow, Russia.(2) ENEA Frascati

• Refractometry is a technique similar to reflectometry, but without any cut-off present into the plasma.

• The launched wave is reflected directly by the inner wall of the vacuum vessel. The phase velocity of the wave depends on the refracted index of the plasma, and hence on its density. The Time Of Flight (TOF) refractometer measures the time delay that a small package wave takes crossing the vacuum vassel, that is a direct measure of the wave group velocity. As usual using the cold plasma refractive index the line integrated density can be inferred.


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Proposal

• The prototype was tested on FTU using a single frequency( 60GHz, X-mode) but two subsequent phases are envisaged to extract the feature related to the density profile

• The proposal is :• 1° phase : to use a two frequency system• 2° phase using a swept oscillator to cover a

range of frequencies • 3° phase : a system mounted on a vertical port.


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Prototype and first results on FTU


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Conclusions

• A programme of development of ITER relevent diagnostics is proposed by FTU Team.

• ITPA TG Diagnostics( and the SWGs) are invited to participate and/or to give advice

to define a final version of the programme.

status of a programme for development of iter relevant diagnostics onftu

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