corrections to the energy distribution of the nbi power ppf
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Corrections to the energy distribution of the NBI power PPF. Background History of the problem Proposed changes Affected data. Background – Beam Species Determination. JET neutral beam is composed of full, half & third energy particles

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corrections to the energy distribution of the nbi power ppf

Corrections to the energy distribution of the NBI power PPF

Background

History of the problem

Proposed changes

Affected data

DVCM

background beam species determination
Background – Beam Species Determination
  • JET neutral beam is composed of full, half & third energy particles
  • Intensity of the Doppler shifted Balmer-α lines measured on NBTB
  • Relative intensities proportional to fractional distribution in source via D-α, neutralisation and dissociation cross sections for D+, D2+, D3+
  • Source valuesparameterised in terms of extracted beam current
  • Fitting algorithm used to obtain power fractions in neutral beam for PPF
  • Source flux or density fractions?

DVCM

history 1 hemsworth
History 1 - Hemsworth
  • pre – 2003 implicit assumption Doppler flux fractions
  • 2003 JET-DN-C(85)8 (RS Hemsworth) rediscovered

i=1,2,3 E, E/2, E/3

b = beam

g = gas

defines number of radiating transitions per unit length of beam

so DENSITY fractions given by

DVCM

history 2 error further compounded
History 2 – Error Further Compounded

“Doppler shifted Balmer alpha spectroscopy on JET neutral beams” G J van Rooij (1994) copies this methodology when describing NBTB system

Therefore NB Unit decided that PPF was incorrect because Doppler measurements from NBTB gave density fractions

PPF re-written April 2003 for HC triode PINIs in deuterium only

  • 2008 E Delabie (fz-Jülich) reports inconsistency between PPF and beam emission spectroscopy measurements (both into plasma and into gas)

DVCM

history 3 investigation
History 3 - Investigation
  • Thorough review of literature
  • First principles derivation

Correct form of equation linking intensity to beam components:

so Doppler spectroscopy gives FLUX fractions from ion source

  • Confirmation that NBTB Doppler shifted BES also computes flux fractions

DVCM

check intensity ratios
Check Intensity Ratios
  • Calculate power ratios for different source flux fractions
  • Calculate intensity ratios for different source flux fractions

DVCM

calculation of power ppf
Calculation of Power PPF
  • Total neutral power calculated from measured data
  • Full, half and third fractional flux components from theoretical calculation with 4x1019m-2 target

DVCM

changes to ppf
Changes to PPF
  • Only HC Triode PINIs in D are affected
  • Total power remains unchanged
  • Increased power in half and third energy
  • Decreased power in full energy

DVCM

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