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Fitting transport models to 14MeV neutron camera data

Fitting transport models to 14MeV neutron camera data. D C McDonald, K D Zastrow and I Voitsekhovitch. KN3 data for T puff. Puff diffuses to core. puff seen by KS3. KN3 D-T neutron flux (vert.). Inner channels see puff later than outer ones. Time [s]. Methods for fitting transport models.

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Fitting transport models to 14MeV neutron camera data

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  1. Fitting transport models to 14MeV neutron camera data D C McDonald, K D Zastrow and I Voitsekhovitch

  2. KN3 data for T puff Puff diffuses to core puff seen by KS3 KN3 D-T neutron flux (vert.) Inner channels see puff later than outer ones Time [s]

  3. Methods for fitting transport models run TRANSP to produce nT(r,t) and RKN3i(t) choose a D(r) and v(r) • TRANSP models the expected 14MeV neutrons from given diffusion and pinch profiles • Time consuming to optimise the profiles • not clear how to discuss errors TRANSP run SANCO to produce nT(r,t) then calculate RKN3i(t) choose initial D(r) and v(r) calculate c2 and choose new D(r) and v(r) UTC • Automatically finds an optimised parameterised solution with correlated errors • Initial version only treats neutron reactivity in 1d

  4. Poloidal asymmetry in 14MeV emission stronger inboard emissivity in core similar inboard/outboard emissivity at r/a0.6 TRANSP fast ion density r and  dependencies artificially plotted on concentric ellipses • Beam-plasma neutron emissivities are not constant on a flux surface • For JET beam trajectories fast ion birth orbits can be divided into radial 3 zones: • passing orbits in the plasma core • trapped orbits at mid-radius with inboard banana tips • trapped orbits in the plasma periphery with outboard banana tips • This results in a poloidal dependence of the parallel velocity and hence fast particle density / fusion emissivity (also volume and field line angle) C. Challis

  5. Poloidal asymmetry in 14MeV emission • The result of the asymmetry is that UTC cannot match the • This is a clear sign that the 1d model really is inadequate • Some method is required to include the poloidal asymmetry in UTC

  6. Linearised neutron emission • For trace tritium DT neutron emission is the sum of the emission from individual elements of the T profile • If we could take the TRANSP predicted signals from each element, we would completely describe the 2d neutron profile • PPPL has a long term (~6 months) plan to output this data • We can do it with 1 TRANSP run for each element

  7. The TRDT DDA and how to use it TRDT PPF (61097 UID=dmcd) DTrr: rr=01,..., 19 The simulated KN3 signal for each unit density profile element (channel, t) (cts m/s) RHOT: radial position of each element in root normalised toroidal flux (r) RTOT: total 14MeV count rate for each unit density profile element (r,t) (cts m3/s) SVrr: simulated volume fuelling SWrr: simulated wall fuelling Using the PPF • Form DT(channel,r,t) and RTOT(r,t) • Put your T density profile onto the RHOT grid nT(r,t) • Sum over channels to get predicted 14 MeV signals Rtot(t) = SrRTOT(r,t)  nT(r,t) KN3(channel,t) = SrDT(channel,r,t) nT(r,t)

  8. Consistency of method TRANSP matrix t = 23.35s • First cross-check is against a TRANSP run with a full nT(r,t) profile • The plots show that the matrix method agrees with the full run for both • total 14 MeV neutrons • individual cameras • Small disparity in the central cameras is largely due to noise from TRANSP Monte-Carlo simulation

  9. Effect of method on UTC Fit to vertical 14 MeV cameras • The initial UTC runs, with 1d reactivity, could not match the inner and outer vertical KN3 cameras together • With the matrix method we get much better agreement on the KN3 vertical cameras • The c2’s are still too big on some channels, which is believed to be due to effects from... • sawteeth • ELMs • neutral particles UTC with 1d reactivity model UTC with 2d TRANSP reactivity Poor match on outer channels Much better match on outer channels

  10. Plan of action 20 shots selected for EPS All done ~half done • Method requires a TRANSP runs for all tritium puff shots, so these need to be requested • We propose that these runs are started now and that they are carried through to a UTC analysis • Timing: • Initial TRANSP run and validation~ 3 days • 20 basis function runs and TRDT ~ 1 day • Basic UTC analysis ~ 1/2 day

  11. Summary • TRANSP fitting of D(r) and v(r) to neutron data is slow, tedious and does not result in a measure of significance for the results • UTC resolves these problems, but its original 1d reactivity model couldn’t reproduce the asymmetric neutron emission • Solution is to use UTC with a 2d description of the neutron model passed from TRANSP as a matrix • Greatly reduces asymmetry of UTC fit to neutron data • Do require TRANSP runs for all tritium puff shots • Further problems: saw teeth/ELMs transport, the effect of CX with neutral particles

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