ADSA2014/Ameigs Electron temperature from high-n Balmer series at JET: A question of “n” A. Meigs, M. O’Mullane, and E. Delabie (discussions of future modelling EDGE2D/Eirene with Paula Belo and Mathias Groth) From Stark widths one can get estimate of electron density (ADAS2013, PSI2012, …) Presumably, given this knowledge of n e, then the line intensities or line ratio’s should give an estimate of T e (and possibly n n /n i )

ADSA2014/Ameigs Questions Questions: What are the best set(s) of n-levels to measure? Is the “high-resolution” spectra (left) capable of giving T e estimate? (or even shifted to cover 9-2 to 14-2) Can we do better for T e by using a survey spectra? Are other effects (MAR) possibly important? How can we tell?

ADAS2014/Ameigs KT3D Overview: Lines of sight Passive Divertor Spectroscopy Mirror-link  largest wavelength range of any JET diagnostic ( nm) D influx and recycling profiles Recombination monitoring n e and T e in recombining divertor Impurity influx and profiles (Be, C, W, O, N, Ar…)

ADSA2014/Ameigs Single Shell Model of Balmer Line Intensities Intensity of a Balmer transition u-2: Only 3-body recombination and electron impact excitation are considered (for now) Where: u = upper n-level for the transition n e = electron density n i = ion density n n = neutral density P u R (n e,T e ) = the recombination Photon Emission Coefficient from ADAS for a transition u-2 P u E (n e,T e ) = the excitation Photon Emission Coefficient from ADAS DL = the integration path length (assuming single shell model) Wrapper to ADF15 using file '/home/cxs/adas/adf15/pec12#h/pec12#h_balmer#h0.dat' so that recombination only and excitation only components could be retrieved. Too many unknown’s Needs full modelling codes to get at all parameters Can we reduce this set using line ratios

ADSA2014/Ameigs Can we do better with line ratio’s (and which ones)? Where the second formula we have created a new variable a = n n /n i Assuming the single shell model is ok, then the line ratio removes: DL, linear n e (only n e now in PEC’s)

ADSA2014/Ameigs Balmer Line Ratios: Further factoring makes apparent a “correction” term to the pure recombination ratio: So the relative size of this correction term depends on both the relative ratio of excitation to recombination for the u-state and the r-state. For a given a, a u-state dominated by recombination and a r-state driven more by excitation would provide the largest correction factor.

ADSA2014/Ameigs ADAS Balmer Line Ratios: 12/6 5.7x

ADSA2014/Ameigs ADAS Balmer Line Ratios: 9/6 2.9x

ADSA2014/Ameigs Examples of Balmer Line Ratios: 12/9 1.6x

ADSA2014/Ameigs Balmer Line Ratios: Measured in “Survey Spectra” JET pulse: Ohmic Vertical outer strike point Gas ramp to density limit disruption. 13-2

ADSA2014/Ameigs Electron density from line shape

ADSA2014/Ameigs Intensity of the 10-2 Line and ratio 10-2/6-2 Intensity 10-2 transitionIntensity Ratio 10-2 to 6-2 Some ratios above ADAS recombination only results

ADSA2014/Ameigs Intensity of the 8-2 Line and ratio 8-2/6-2 Intensity 8-2 transition Intensity Ratio 8-2 to 6-2 More ratio’s above ADAS prediction Possible reasons for too large ratios: 1)For highest n’s (14-2, 13-2, maybe 12-2) near the continuum merging/limit: incomplete baseline subtraction 2)For both high-n and lower-n: other population mechanisms  MAR?

ADSA2014/Ameigs T e from fit to line ratios: 7-12 over 6 Naively perform fit of ratio’s as function of n considering as reference the 6-2 transition All fits suffer from low-n ratio discrepancy forcing high-n under-shoot of T e t= 59.42s Is the low-n discrepancy indicative of the contribution of excitation? Certainly, the excitation term would correct the ADAS values towards the n=7 and n-8 data.

ADSA2014/Ameigs T e from fit to line ratios: 7-12 over 6 t= 60.22s

ADSA2014/Ameigs T e from fit to line ratios: restrict N upper 9-12 t= 60.22s Still a small problem with n=9

ADSA2014/Ameigs ADAS Balmer Ratio: 7/6

ADSA2014/Ameigs Look at individual ratios Infer T e thru interpolation: given a ratio, interpolate ADAS ratio to obtain T e (still using n e from line shape) Ensure no extrapolation beyond the T e grid passed to ADAS (T max = 10.0eV)  if result > max T e of grid, then T e = -1.0 Not (yet) ensuring that the ratio is in “useful range” or even above ADAS limit (extrapolation limit will get probably all of the above limit values) **After doing this I think the limit should have been ~3.0eV (but need to look at the individual ratio curves to find max)

ADSA2014/Ameigs Look at individual ratios 10/6 Electron density Zoomed away from x-point T e 10/6

ADSA2014/Ameigs Look at 9-12 fit vs individual ratios Comparison of Te from individual ratios 10/6,11/6, 9/6, 12/6 and the fitted 9-12 N-fit error bars are 2-s

ADSA2014/Ameigs High resolution setting: L-mode Density Limit 1.46x

Ratio 11/10 ADSA2014/Ameigs High res. setting: L-mode DL, Horizontal target 11-2 Intensity nene 12-2 Intensity Ratio 12/10 Restricted (for now) to 11-2 and 12-2 as 13-2 and 14-2 may not be “reliable” (later, this is questioned)

ADSA2014/Ameigs High resolution setting: L-mode Density Limit T e from 11/10 T e from 12/10 Gibberish….. Why? Dn too small so dynamic range of ratio too restricted? Does horizontal target delocalize the measurement too much? Are MAR effects more important in this higher density plasma compared to the Ohmic case?

T e max= 4eV for inferred results ADSA2014/Ameigs n-fit 11/10 and 12/10 only vs infered 11/10,12/10 Large errors indicate one or other ratio at or near limits

ADSA2014/Ameigs High resolution setting: L-mode Density Limit Ratio 12/10 The sky blue areas are above the ADAS limit

ADSA2014/Ameigs : extend to 13-2 and 14-2 over 10-2… For fun, I thought to include 13-2 and 14-2 ratios….. Note: 13-2 may experience more of the continuum merging baseline which is not accounted for in current fits will have more of this baseline, plus it is under the Be III triplet! (how much to trust the intensity) Peak near strike point!

ADSA2014/Ameigs profiles versus time Nice correlation with ne versus time (but is it “just” a correlation) Are the fits believable yet? NO, I think not.

ADSA2014/Ameigs Conclusions? And further work Conclusions: Survey spectra may allow some determination of electron temperature and possibly identify when excitation comes in; plus maybe n n /n i estimation Further work: 1.Check if 80821, a clean Ohmic plasma, has problems with 11/10 and 12/10 ratio’s in the survey spectra 2.Look at the 9-14 spectra (started but mixed results and way too many slides as it is) 3.Most measurements since ~Feb use the 9-14 spectral setting and where repeats are possible the 6-14 survey spectra is taken  Some H-mode plasmas fitted for ne but none looked at for line ratio’s 4.EDGE2D/Eirene (plasma modelling codes) have implemented simulation of the KT3 diagnostics lines of sight and have imported ADAS results to calculate the LOS-integrals for the high-n Balmer series (need to make sure the ADAS dataset is correct one)  Look at LOS-integrals and ratios from modelling codes compared to experimental results. 5.Nail down some constraints on the n-fit so that acceptable ranges are not exceeded and so that periods where the data ratio’s exceed the ADAS ratio’s are identified more easily 6.Look into the state of the art on MAR and see how to include it in the CR modelling of the Balmer populations. 7.For survey try to fit getting n n /n i from the 7/6 and 8/6

ADSA2014/Ameigs Look at L-mode Vertical target: new range outer vertical target L-mode density limit

ADSA2014/Ameigs Recombination only“Intensity” vs n for several T e Assuming recombination only Setting n i = n e

ADSA2014/Ameigs for two densities

ADSA2014/Ameigs Wrapper to ADF15 for high-n Balmer lines FUNCTION agm_readadf15_balmer, nupper, $ dens = dens, $ ;; input, if not present then ADAS grid returned te = te, $ ;; input, if not present then ADAS grid returned exciteonly = exciteonly, $ recombonly = recombonly, $ all = all, $ ;; if want 2D grid on Te and Ne values-- this is a ;;keyword to read_adf15. If not set then 1D results ;;numbering the smaller of Te and dens arrays verbose = verbose filename = '/home/cxs/adas/adf15/pec12#h/pec12#h_balmer#h0.dat'