Integrated modeling of LHCD non- induc6ve scenario development on Alcator C- Mod

Transcription

1 Integrated modeling of LHCD non- induc6ve scenario development on Alcator C- Mod S. Shiraiwa, P. Bonoli, R. Parker, F. Poli 1, G. Wallace, and J, R. Wilson 1 PSFC, MIT and 1 PPPL 40th European Physical Society Conference on Plasma Physics Espoo, Finland, 1st 5th July 2013

2 Integrated plasma simulator has been adapted for interpreta6on of non- induc6ve LHCD discharges on Alcator C- Mod Goal Incorporate an advanced LHCD code to integrated plasma simulator (IPS) and apply it to C- Mod experiment Build an infrastructure to use IPS for C- Mod experiment Compare the current diffusive ballooning mode (CDBM) model predic6on with ITB discharges on C- Mod Construct opera6onal scenario to access an advanced regime using proposed upgrade of LHCD on C- Mod (x2 P LH and off- midplane launcher) Key results Integra6on of a Raytracing / 3D Fokker Planck code (GENRAY/CQL3D) is completed IPS simula6on of an ITB discharge was modeled using the Coppi- Tang transport model A test of using CDBM to reproduce an ITB forma6on observed on C- Mod has started

3 Lower hybrid current drive (LHCD) is envisioned as an efficient off- axis CD tool for reactor. Prospect of LHCD on reactors Far off- axis CD for J(r) control High efficiency required to achieve Q=5 ITER goal Remaining issues to utilize LHCD in fusion reactors Demonstrate efficient LHCD with reactor condi6ons (ne, B t, f LH, P LH (r), magne6c configura6on) Develop a robust antenna technology compa6ble with rector relevant condi6ons in SS Improve and validate predictable capability required for opera6onal scenario development J // (MA/m 2 ) SS Q=5 on ITER F. Poli 1 0 NBCD ECCD bootstrap LHCD r/a LH3 planned on C- Mod to realize ITER- like J LH (r) F. Poli, et. al., APS (2012), this conference

4 Integrated modeling using TRANSP/LSC reproduces experimental current profile evolu6on well TRANSP/LSC in interpre6ve mode. Time evolu6on of current profile is compared with kine6c- MSE constrained EFIT, showing good agreement Weakness needs to be addressed.. sta6onary solu6on of 1D FP calcula6on CD efficiency is known to be under predicted, and patchwork (increase P LH by 50%) is needed. S. Shiraiwa FEC (2012)

5 Access to advanced opera6on is studied with TRANSP/LSC showing a path to a regime of f BS >50% Key features Off- axis LHCD ICRF hea6ng Opera6on at higher density (n e ~1.5x10 20 m - 3 ) shear reversal broad pressure profile steady state with high f BS (> 50%) Issues of this modeling include Use of LSC at high density is ques6onable (see next page) Confinement improvement was assumed based on a previous ITB discharge A model based predic6on of ITB forma6on is necessary

6 Mo6va6on 1: Recent progress on LHCD modeling code needs to be incorporated to integrated modeling Early codes uses stationary solution of FP equations. Time evolution of distribution function can not captures. Improved codes (RT + FW) have several advantages 100 Coupled with 3D Fokker- Planck calcula6on Edge/SOL plasmas are included Collisional absorp6ons outside the last closed flux surface Fullwave codes are in a mature status, worth considering integra6on to 6me- domain simula6on (long term) Power absorbed [%] Forward n Inside LCFS Forward n Outside LCFS Reverse n Line averaged n e [m 3 ] 1.5 x10 20

7 Mo6va6on 2: C- Mod is planning to realized ITER- like highly off- axis LHCD exploi6ng velocity space synergy normalized power Z(m) R (m) R (m) Proposed experiment 3.5 Double LHCD power to 2MW level nd launcher is located off- midplane in order to realize high single pass 2.5 absorp6on 2.0 Goal is to demonstrate recovery of LHCD efficiency at high density by 1.5 enhanced single pass absorption J tor (MA/m 2 )

8 Mo6va6on- 3 : validate a transport model using ITB discharges on C- Mod [MA] [V] [kev] I p & P LH LH Loop Voltage T e

9 Integrated Plasma Simulator (IPS) Plasma State : stores information of tokamak plasma (equilibrium, profiles,,) Components : compute each physics (equilibrium, transport, H&CD, stability) Wrapper : handles interaction with PS Driver : runs components

10 GENRAY/CQL3D (Raytrading/3D FokkerPlanck) for LHCD calcula6on was integrated to IPS plasma state ψ(r, Z), T(r), n(r) GENRAY ψ(r, Z), T(r), n(r) P LH (R), J LH (r) ψ(r, Z), T(r), n(r) Ray trajectory CQL3D TSC Itera6on loop 1ms on C- Mod

11 MDS plus experimental data Python based interface for preparing input and visualizing IPS results is being developed Data browser for NETCDF, mdsplus, namelist Built- in python consol (running on Hopper)

12 First test was run using the Coppi- tang transport model Target plasma I plamsa ~ 500 ka Density ~ 5x10 19 m - 3 Experimental plasma parameters (T e, shape) are reproduced reasonably well q 0 > 1 after 1s while sawtooth suppression in the experiment was ~0.98s V loop is slightly higher than the experiment resul6ng in low NI frac6on. due to lower Te than the experiment

13 IPS captures evolu6ons of current profile, q profile, V loop,,, 0 ms At LH turn- on, V loop near the center drops first Due to low (2keV) T e0, LH power deposited near the center. 600 ms Time scale of LH driven current profile evolu6on is much longer compared to T e change

14 Radial profile : f ( v para, v perp =0, r),,, and 3D distribu6on func6on Velocity space : f ( v para, v perp, r/a=0.6) LH turn on (0ms) 5 ms 10 ms

15 Current diffusive ballooning mode (CDBM) model CDBM involves reduction of thermal diffusivity by ExB shear flow. Magne6c shear Normalized pressure gradient Magne6c curvature Rota6on shear Theory developed by A. Fukuyama 1 and has been used ITB discharges 2 A code for TSC was implemented by F. Poli and used for predicting steady-state scenarios in ITER 3 1 A. Fukuyama, et. al., PPCF (1995) 2 M Honda, et. al., NF (2006) 3 F. Poli, et. al., FEC (2012)

16 Valida6on using an ITB discharge is on going Initial plasma was setup using the Coppi-Tang model Switch to CDBM at ~400ms Sawtooth parameters are fixed to better reproduce exp. CDBM Initial result is promising Smooth transi6on from Coppi- tang model T e amplitude and frequency due to sawtooth are bener consistent with experiment Still need to address Bener match of T e and V loop Possible nonlinear interac6on of shear modifica6on due to sawtooth and CDBM

17 Summary A LHCD modeling using ray-tracing/3d Fokker-Planck code was integrated to Integrated plasma simulator (IPS) framework Evolu6on of 3D distribu6on func6on consistent with 6me evolu6on of bulk T e, n e and Ohmic electric field profile Parasi6c absorp6on based on a collisional SOL plasma model, extending consistency with C- Mod LHCD data to higher density IPS was applied to an ITB discharge on C-Mod With the Coppi- Tang transport model, good reproduc6on of T e0, V loop, and q 0 was obtained (comparison with current profile measurement is underway) Evolu6on of distribu6on func6on in 4D space is demonstrated A test of using current diffusive ballooning mode (CDBM) mode is underway Future works include.. Resolve remaining issues Lower NI frac6on and higher V loop (by ~ V) T e0 lower by 10-20%, resul6ng in LH power deposi6on closer to axes Compare the predic6on of the CDBM model with experiments Improve LHCD discharge scenario and performance predic6on for proposed LHCD experiment using LH2 + LH3