10 March 2009 DVCM

Corrections to the energy distribution of the NBI power PPF

Background

History of the problem

Proposed changes

Affected data

10 March 2009 DVCM

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 values parameterised in terms of extracted beam current

• Fitting algorithm used to obtain power fractions in neutral beam for PPF

• Source flux or density fractions?

Wavelength (nm)

Lig

ht

em

issi

on

inte

nsi

ty (

10

³ co

un

ts/s

)

650 652 654 656 6580

1

2

3

4

D(E)

D(E/2)

D(E/3)

Impurities

D

H

Deuterium Beam Current (A)

Ion

sour

ce d

ensi

ty fr

actio

n (%

)

20 30 40 50 600

20

40

60

80

100

D+

D2+

D3+

Supercusp

10 March 2009 DVCM

History 1 - Hemsworth

• pre – 2003 implicit assumption Doppler flux fractions

• 2003 JET-DN-C(85)8 (RS Hemsworth) rediscovered

gbiii NnvDdt

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

b = beam

g = gas

gbiii NnR defines number of radiating transitions per unit length of beam

so DENSITY DENSITY fractions given by

1

22

022

2

R

Rc

D

D

,

10 March 2009 DVCM

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 onlyfor 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)

Intensity Power Fraction BES

Power Fraction PPF

E/1 1.400E11 0.746 0.841

E/2 8.506E10 0.163 0.111

E/3 7.797E10 0.091 0.048

10 March 2009 DVCM

History 3 - Investigation

• Thorough review of literature• First principles derivation

Correct form of equation linking intensity to beam components:

1

222 vD

vDc

1EI

2EI

so Doppler spectroscopy gives FLUXFLUX fractions from ion source

•Confirmation that NBTB Doppler shifted BES also computes flux fractions

10 March 2009 DVCM

Check Intensity Ratios

• Calculate intensity ratios for different source flux fractions

0

0.5

1

1.5

2

2.5

3

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

target 1020m-2

I 2/I

1

0.7/0.25

0.75/0.2

0.8/0.15

0.85/0.1

0.9/0.05

data

neut target range

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

target 1020m-2

P(E

/2)

• Calculate power ratios for different source flux fractions

10 March 2009 DVCM

Calculation of Power PPF

• Total neutral power calculated from measured data

Deuterium Beam Power - Triode PINIs(Perveance match; 11/18 mbar×l/s)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

50 60 70 80 90 100 110 120 130

Beam voltage (kV)

Bea

m p

ower

(M

W)

PINI4.1

PINI8.2

PINI8.3

PINI8.4

PINI8.5

PINI8.6

PINI8.7

PINI8.8

3

0k

kkTOT VaP

•Full, half and third fractional flux components from theoretical calculation with 4x1019m-2 target

kP

4

0k

kk

TOTii

Vb

PVfP

10 March 2009 DVCM

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

71938

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

46.85 46.9 46.95 47 47.05 47.1 47.15 47.2

t(s)

P(M

W)

Power Fraction

BES

Power Fraction new PPF

E/1 0.746 0.74

E/2 0.163 0.14

E/3 0.091 0.12