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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. 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

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  1. Corrections to the energy distribution of the NBI power PPF Background History of the problem Proposed changes Affected data DVCM

  2. 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

  3. 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

  4. 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

  5. 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

  6. Check Intensity Ratios • Calculate power ratios for different source flux fractions • Calculate intensity ratios for different source flux fractions DVCM

  7. 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

  8. 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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