Simulation of the discharge waveforms of power supplies of HL2A by a plasma resistance model

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Simulation of the discharge waveforms of power
supplies of HL-2A by a plasma resistance model

• Song Xianming, Mao Suying, Chen Liaoyuan
• Li Bo,Yao Lieying
• Southwestern Institute of Physics
• P.O.Box 432, Chengdu, Sichuan, 610041, China

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content

• 1) plasma resistance mode
• 2) simulation results
• 3) summary

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1) Plasma model

• The 4 stages of plasma discharge
• 1) Electron avalanche according to Townsend
  mechanism
• 2) Ionization, electron temperature is constant,
  ne increases linearly, Rp drops with 1/ne
• 3) Ohmic heating, complete ionization, Te
  increases linearly, Rp drops with 1/Te3/2.
• 4) Flat top, ne and Te is constant, So Rp is
  constant

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Typical traces of Ip,Te and Rp
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The plasma resistance as a function of time
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Plasma resistance (m?)
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model

• 1) length of first stage (the electron avalanche)
  is determined mainly by maximum applied loop
  voltage (v higher, length shorter) and level of
  stray field (field lower, length shorter).
  Typical values 8V 15ms 10V 8ms 15V lt5ms
  300V lt1ms (ASDEX)
• 2) length of second stage (Ionization) is
  determined mainly by loop voltage(v higher,
  length shorter) and level of stray field (field
  lower, length shorter). Typical values are from 5
  to 15ms.

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model

• 3) length of third stage (Ohmic heating) is
  determined by the preset plasma current waveform.
  Typical values are from 50ms to 200ms.
• 4) length of third stage (Flat top) is determined
  by the preset plasma current waveform. Typical
  values are from 200ms to 5000ms.

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model

• 5) R(t0) is determined by the loop voltage and
  the gas density. Typical values are from 3m? to
  50m?.
• 6) R( t1) is determined by the impurity and
  limiter position. Typical values are from 0.05m?
  to 3m?. .
• 7) R( t2) is determined by preset plasma current
  waveform and limiter position. Typical values are
  from 0.0005m? to 0.03m?.

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The involved ODE set
Here subscript V, P, ? and m denotes vertical,
plasma ,ohmic and multiple respectively.
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equilibrium condition

• In order to solve the ODE set, the equilibrium
  condition should be exploited. That is for a
  given plasma configuration, the equilibrium
  requires Im/Ip and Iv/Ip remain constant.
• Im/Ip 0.07-0.11, Iv/Ip 0.06-0.09

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The parameters of coils

• The inductances and resistances of coils are
  calculated, and some of them are validated by
  experimental data

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2) simulation results

• We choose 6 sets of parameters for simulation

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case 1, Ip150kA
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case 2, Ip150kA
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case 3, Ip150kA
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case 4, Ip150kA
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case 5, Ip150kA
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case 6, Ip150kA
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3) summary

• 1) This code provides a promising platform for
  further work. Extensive studies are being
  prepared to understand the quantitative relations
  between resistance model parameters and
  engineering or physical parameters.
• 2) The power supply model also needs to be
  modified to validate this plasma resistance
  model. The present discrepancy between the preset
  voltages and the voltage output of power supply
  is from 20 to 60.

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• Thank you for your attention!