Transcript ht-7u asipp
ASIPP Magnetic Diagnostics of HT-7U Tokamak Shen Biao Wan Baonian Institute of Plasma Physics, CAS P.O.Box 1126, Hefei, Anhui 230031, P.R.China (e_mail: [email protected]) HT-7U ASIPP HT-7U Outline • Brief introduce of ht-7u. • Principle and purposes of magnetic diagnostics. • HT-7U magnetic diagnostic system. • Summary. ASIPP HT-7U Tokamak HT-7U Main Parameters Toroidal Field, Bo 3.5 T Plasma Current, IP 1 MA Major Radius, Ro 1.7 m Minor Radius, a 0.4 m Aspect Ratio, R/a 4.25 Elongation, Kx 1.6 - 2 Triangularity, d x 0.6 - 0.8 Heating andCurrent Driving: ICRH 3 - 3.5 MW LHCD 3.5 MW ECRH 0.5 MW Pulse length 1000 s Configuration: double-null divertor, single null divertor, pump limiter HT-7U ASIPP Magnetic Diagnostics Principle • Electromagnetism • Maxwell’s equations B ( j D ) t B 0 E D B t Purposes •Equilibrium plasma configuration determination. • for real time plasma control. (current, position, shape, current profile, and disruption control) . •MHD phenomena. •Transient electromagnetic phenomena studies. HT-7U ASIPP Position/shape Time resolution Rate of change Accuracy Rin,Rout 1ms 100cm/s 0.5cm Rx,Zx 1ms 100cm/s 0.5cm Zc 1ms 100cm/s 0.5cm Ip range Time resolution Rate of change Accuracy 0.1-1MA 1ms 5MA/S 2% Beta range Time resolution Rate of change Accuracy 0.01<βp<5 1ms 1mWb/s 10-5 Parameter Max.frequency Spatial resolution Accuracy MHD >100kHz 5cm 10% ASIPP HT-7U Sensor Number Position Two-component Magnetic probe (42+27)*3 pol.*tor. Inner vacuum vessel wall and behind the carbon shield MHD probes (Mirnov coils) 20*3 pol.*tor. Inner vacuum vessel wall Poloidal flux loops 31 Inner vacuum vessel wall Saddle/locked loops 10*3 pol.*tor. Inner vacuum vessel wall In the low field area Voltage loop 5 Inner vacuum vessel wall Rogowski coil 1*3 por.*tor. Inner vacuum vessel Diamagnetic loop 1*3 por.*tor Inner vacuum vessel and outer of vacuum vessel 8*4 behind the divotor Vessel monitor structure current HT-7U ASIPP HT-7U Magnetic Diagnostic System 1. Magnetic probes and Flux/voltage loops Magnetic probes are used to measure poloidal magnetic field, and flux loops are for poloidal magnetic flux measurement. 30 magnetic probes on vacuum vessel wall 17 behind carbon shield 39 flux loops on vacuum vessel wall HT-7U ASIPP Magnetic probes four arrays in different positions . •for feedback control of plasma position and shape •combine with other diagnostics is used for reconstruction of plasma parameters •study the MHD activities •one array placed in toroidal direction equably ASIPP HT-7U • Isolation voltage >1000v • Inductance: 2.20uh (tangential direction). 1.18uh (Normal direction) • Resistance: 4.00 ohm (tangential direction). 2.50ohm • Analogue bandwidth: >10kHz (Normal direction) • Number of layers: 2 • Number of windings per coil: 160 • Effective winding area (A*N): tangential direction 1133cm2 Normal direction 1431cm2 ASIPP Flux/voltage loops cover all 16 segments in the horizontal plane (toroidal direction). 31 flux loops are located inside the vacuum vessel expect the horizontal window and upper and down windows near the divertor. HT-7U ASIPP HT-7U 2. Plasma Current Rogowasky Coil • Rogowski coil is a solenoidal coil whose ends are brought around together to form a torus. • It is used to measure plasma current • One set include 2 Rogowski coils One will be set around plasma inside vacuum wall. Another one will be set outside the vacuum wall. • Three sets will be set in different toroidal directions. ASIPP 3. Saddle/locked-mode coils One set of saddle/locked-mode coil on the inside vacuum vessel wall HT-7U ASIPP HT-7U • These coils are used to measure poloidal magnetic flux and detect the non-rotating or slowly rotating of magnetic perturbations. • The locked-mode coil will be placed on the outer mid-plane inside the vacuum vessel . • 5 saddle coils will be placed in the upper and 5 in down positions near the divotors. • Six to eight arrays will be installed in different toroidal directions symmetrically. ASIPP HT-7U 4. Diamagnetic Loops • Diamagnetic loops system includes measurement loops, compensation coils and associated processing electronics. • It is used to measure plasma βp and plasma energy. • Three sets are going to be mounted on the inner of the vacuum vessel wall. ASIPP HT-7U Requirement • The very small signal need to improve the signal to noise ratio. • Position must be vertical direction of the toroidal field strictly to decrease the influence of toroidal field. • The diamagnetic loop and compensation coil must be parallel. Both of them set on the same framework. • The position of system need to be adjusted to minimize the influence of the poloidal field. • Use ceramic or BN as framework. ASIPP HT-7U 5. Measurement of Halo current A poloidal halo current due to VDE is observed in most large tokamak experiment. During plasma disruptions, a current flow directly into a vacuum vessel from plasma. It will produce an intense electromagnetic force on the invessel components. • four sets of Rogowski coils are installed behind the divertor tiles in each toroidal location. • The coils are installed to round the roots of the divertor tiles. • Four groups of these coils will be set in different toroidal positions HT-7U ASIPP Special material 1. Cables (fiberglass) • good vacuum 70 (1000) 0.000006 0.000005 Leakage ratio< 10e-6 • insulation (Isolation voltage >1000v) • heat-resistant >=300 Y Axis Title 0.000004 0.000003 0.000002 0.000001 0.000000 0 20 40 60 X axis title 80 100 ASIPP 2. framework • ceramic different to machine • NB brittleness 3. vacuum feed-through •32 molybdenum conductor pins which gold plated • Each pin is fasted and insulated with glass sinter. •The leak ratio is litter than 10-5Pal/s HT-7U ASIPP HT-7U Protection and Improve the signal to noise ratio Protection • put behind graphite tiles • put in a box or behind a sheet Improve the signal to noise ratio • output cable need to be twisted each other. • stainless steel boxes or tapes could be used as electric-magnetic shield. • to avoid ground loops . HT-7U ASIPP Digital Integrator Digital Signal Processor Integrator D0~D31 Gain ratio DSP FPGA V/F Converter Controler PGA analog signals digital signals ASIPP HT-7U Summary • The progresses of HT-7U project in building, and it is possible to get the first plasma around 2005. • Physical design of magnetic diagnostic for HT-7U has been completed. • Final engineering design for magnetic diagnostics are under preparation. HT-7U ASIPP End and thanks