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Charge Exchange Neutral Particle Diagnostic on HL-2A G. Zhong Plasma Diagnostic Division, SWIP IPP, Hefei, April 27, 2005. Outline. Goals Gas stripping neutral particle analyzer on HL-2A(G-NPA) Primary design of a multi-channel neutral particle analyzer on HL-2A Summary.

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  1. Charge Exchange Neutral Particle Diagnostic on HL-2AG. ZhongPlasma Diagnostic Division, SWIPIPP, Hefei, April 27, 2005

  2. Outline • Goals • Gas stripping neutral particle analyzer on HL-2A(G-NPA) • Primary design of a multi-channel neutral particle analyzer on HL-2A • Summary

  3. Goals of NPA diagnostic on HL-2A Integrated energy spectra of CX particle of multi-sightlines Ion temperature profile Study on heating and advanced configuration in HL-2A Particle physics on HL-2A

  4. Semiconductor? C foil Gas H0 Beam 1000 100 1 10 0 Particle Energy(keV) Neutral Particle Diagnostic on HL-2A: Particle Energy

  5. G-NPA: Features • H2 Stripping cell • Electrostatic energy analyzer of 450 parallel plates • 8 energy channels • Energy from 0.5 keV to 10 keV

  6. G-NPA Setup G-NPA on HL-2A • 1 Perpendicular viewing at central chord in the plasma • 2 H0 radiated from plasma • 3 Deflection plates to remove H+ • 4 H2 stripping cell to ionize H0 • 5 450 parallel-plate electrostatic analyzer with 8 exit slits • 6 Trajectory of H+ bent by E-field in the analyzer • 7 8-channeltron array to record H+ • 8 Amplifiers and discriminators • 9 Counters • 10 and 11, optical isolating interface and pc splasma 23.5 cm 339 cm Collimator factor:

  7. G-NPA on HL-2A Improvement to recording weak H0 beam by strong pulse feeding of H2 into stripping cell

  8. G-NPA: energy spectra of CX particles

  9. Ti in repeated discharges on HL-2A

  10. 600 400 Ti/eV 200 0 9.00 NPA_C8 4.00 -1.00 23.00 NPA_C7 10.22 -2.56 91.00 NPA_C5 40.44 -10.11 170.00 NPA_C1 75.56 -18.89 0.08 LHW -0.52 -1.13 160.44 Ip/kA 70.97 -18.50 0 100 200 300 400 time/ms LHW heating: core plasma • Ions were heated during LHW with plasma density of 2-3×1019 m-3 Shot 5559

  11. 200 NPA_Ch8 100 0 600 NPA_Ch1 300 0 0.08 LHW -2.74 -5.57 200 325 450 575 700 time/ms LHW Power Dependence of 4.5 keV Neutrals Density Dependence of 4.5 keV Neutrals 100 40 100 kA 30 80 with and without LH Ratio of Neutrals 20 60 Ratio of Neutral Flux with and without LH 10 40 0 20 0 100 200 300 400 0 LHW Power(kW) 0 1 2 3 4 5 6 Density(10^19/m^3) LHW heating: edge plasma Generation of energetic ions is dependent on • plasma density • wave power • plasma current 100 kA 160 kA

  12. G-NPA Calibration • Diplasmatron ion source • H0 beams after mass analysis • Energy calibration • Registration calibration • Calibration of the scattering effect

  13. 10 1 3 6 8 4 2 5 7 6 Analysis Voltage(kV) 8 4 2 0 0 2 4 6 8 10 Ion Energy(keV) G-NPA Calibration: Energy Ch 6, theoretical

  14. G-NPA Calibration: Energy Resolution X-axis: analysis voltage in volts; Y-axis: counting rate for H0 beam of 2 keV

  15. Registration Coefficiency Ch1 1 Ch2 Ch3 Ch4 0.1 Ch5 Efficiency Ch6 Ch7 Ch8 0.01 0 2 4 6 8 10 Neutral Particle Energy(keV) G-NPA Calibration: Efficiency Registration Efficiency of Ch6 1 Efficiency(a.u.) 0.1 1 Pa 5 Pa 0.01 0 2 4 6 8 10 Neutral Particle Energy(keV)

  16. G-NPA Calibration: Scattering 1 0.9 0.8 Permeation 0.7 0.6 0.5 0 2 4 6 8 10 Neutral Particle Energy(keV)

  17. Conception of MC-NPA • Analysis of particles from thermal to beam energies • Compact • Electrostatic energy analyzer • Step-wise analysis voltage • Charge stripping with carbon foils • Detectors of channeltron • Soft iron vacuum chamber with additional magnetic screen • Pumping by HL-2A machine • No mass analysis

  18. NPA Collimation Geometry plasma volume NPA window Splasma ω I0 d I0ωSplasma, d fixed NPA Position of MC-NPA • Position is defined by • Machine port • Tolerable ambient magnetic field • 1.75 m away from plasma center • The position has little effect on neutral influx

  19. Angels of MC-NPA sightlines • Total viewing angle : 220 • 2.20 between neighbor sightlines • Scattering of the stripping foil on secondary ions • Overlay of viewing volume • Cross talk of neighbor sightlines

  20. 11 channels, evenly arranged • 2.20 between 2 sightlines • Pinhole is 1.75 m away from the plasma Pinhole Foil module Sightlines of MC-NPA

  21. 多道中性粒子分析器原理图 HL-2A Machine C-Foil Module Pinhole 175 cm 37-42 cm H＋ H0(1－100 keV) • 11 channels, evenly arranged • 2.20 between 2 sightlines • Pinhole 1.75 m away from the plasma • Multi stripping foils

  22. Sightlines in toroidal direction  Sightlines can be rotated in toroidal direction when using the port of 600  = 6.40 : for all channels  = 12.50: for central channel top view

  23. D Toroidal sightlines with a movable pinhole & fixed pinholes Movable Pinhole Fixed Pinholes Foil Module Toroidal angle, , is given by L and D. Maximum  is defined by the machine port HL-2A L  top view Change solid angle Fixed Pinholes Change toroidal direction

  24. Features • Charge stripping with carbon foils • Cylindrical electrostatic analyzer • Energy from 0.8-1 keV to 100 keV • Energy spectra obtained via scanning of the analysis voltage • 11 spatial channels with variable sightlines in toroidal direction • Collimation factor: 5x10-4 to 5x10-6 stcm2

  25. MC-NPA: Waveform of the Step-wise Analysis Voltage V Positive Bias t Negative Bias Over shot and down shot: < 2 % Rise time and fall time for each step: < 10 s

  26. MC-NPA: Analysis Voltage Supplies • Type: two supplies with working in the same mode and with opposite voltage output • Working mode 1). DC output • 2). Step-wise with a DC bias • 3. DC output : adjustable from 500 V to 10 keV • 4. Step voltage: adjustable from 200 V to 1000 V • 5. DC bias: adjustable from 100 V to 500 V • 6. Scanning cycle : adjustable from 5 ms to 50 ms

  27. Network PC DAS MC-NPA: layout of control & acquisition • Devices in the frame is positioned near HL-2A • Step-wise Power Supply, stand-alone manually, has an interface connected to C & A. • C&A turns off PSs when pressure is high Step-wise Power Supply Amplifier & Discriminator MC-NPA DC Power Supply Digital Output Meas. Input Counting Digital Output Control & Acquisition Meas. Input Digital Input Trigger Pressure

  28. Trigger 50m Cable Amplifier Counter Channeltron PC Protective Resistor Discriminator Interface Terminator -3 kV Software NPA: An Example Of Recording Electronics Recording electronics in G-NPA For MC-NPA, only the electronics in the frame is needed.

  29. L2 L1  D1 D2 Constraints of reduction of cross talk Diaphragm Foil module Pinhole • Constraint 1: H+ with maximum scattering angle must not enter the neighboring channel. D2 tg(m- ) < D1 tg - 0.5(dc+ d)  is given by 2.20.m is the max. scattering angle. dc and dare diameters of a carbon foil and the diaphragm • Constraint 2: L1 and L2 may be intercrossed at . No intercrossing when D2 tg > = dc+ d m  D1 D2

  30. Stray Magnetic Field A maximum field of 2 kGs is estimated at the NPA position

  31. Measured Vertical Field around HL-2A Bz-r (Iohmic =30 kA) 0 0 100 200 300 400 500 600 700 800 -50 Bz(Gauss) -100 -150 -200 -250 r(cm) MC-NPA positioned around r = 0

  32. Measured Toroidal Field around HL-2A Bt-r Curve (It=30kA) 0.030 0.025 0.020 Bt(T) 0.015 0.010 0.005 0.000 0 20 40 60 80 100 120 r(cm) MC-NPA positioned around r = 0

  33. Key Issues of MC-NPA • HL-2A port: A 600 port needed. • Vacuum: Careful operation needed. Pressure shocks damage C-foils. • Magnetic shielding: Careful magnetic shielding needed. • Carbon foil: Fragile. Not available at home. • Cross talk: Likely. • Analysis power supply: Difficult. • Data processing : Complicated. Computer simulation needed.

  34. Summary • Goals of NPA diagnostic on HL-2A is discussed • CX-neutral diagnostics on HL-2A will be implemented with combination of a gas-stripping NPA and a carbon foil-stripping NPA to analyze neutrals with energies from 0.5 keV to 100 keV. • The carbon foil-stripping NPA features in 11 poloidal sightlines and variable toroidal direction.

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