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Monte Carlo Fast Ions

Monte Carlo Fast Ions. NUBEAM – Neutral Beam Injection and Fusion Product fast ion model. Available at: http://w3.pppl.gov/NTCC See also: A. Pankin, D. McCune, R. Andre et al. CPC Vol. 159 No. 3 (2004) 157-184. Mathematical Model.

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Monte Carlo Fast Ions

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  1. Monte Carlo Fast Ions NUBEAM – Neutral Beam Injection and Fusion Product fast ion model Available at: http://w3.pppl.gov/NTCC See also: A. Pankin, D. McCune, R. Andre et al. CPC Vol. 159 No. 3 (2004) 157-184 D. McCune

  2. Mathematical Model Each fast species distribution function f_i(x,v) is approximated by a set of N Monte Carlo test particles {w(i),x(i),v(i); i=1 to N} (w, “weight” designates the number of physical particles represented; x and v are position and velocity). The model computes for each species: d[f_i]/dt = S_dep(f_i) – S_cx(f_i) + Orbit(f_i) + C(f_i) + RF(f_i) + MHD(f_i), where the operators are: S_dep – deposition. S_cx – charge exchange (interaction with neutrals) with recapture. Orbit – guiding center drift orbiting with FLR enhancement. C – collisional interaction with target thermal plasma. RF– interaction with RF wave field*. MHD– interaction with MHD events and/or field perturbations**. *not yet in NUBEAM. **Ad hoc models only in NUBEAM. D. McCune

  3. Timestep. Plasma MHD equilibrium geometry. Plasma temperatures and densities. Neutral temperatures and densities. Beam geometries & powers & voltages. Fast ion densities & <E_perp>, <E_pll>. Plasma fueling (ion & electron sources). Plasma heating. Torques to plasma. Current drive. Neutral sources, sinks. Nuclear fusion rates. Essential Inputs and Outputs INPUTS OUTPUTS D. McCune

  4. Grid (binning for Monte Carlo sums). Random Number Seed. Physics model options: Atomic physics, FLR… Geometrical information for diagnostic simulations. Sources separated by beam or fast species. Scalar particle, power, momentum balances, each fast ion species. Binned distribution functions. Diagnostic simulation results. “Auxilliary” Inputs and Outputs INPUTS OUTPUTS D. McCune

  5. Model Assumptions -- NUBEAM • MHD equilibrium with nested axisymmetric flux surfaces (i.e. 2d equilibrium & field). • Plasma temperatures and densities constant on flux surfaces. • No strong interaction with edge plasma. • Simplified models for TF ripple loss. • Simplified models to represent MHD loss. • No RF operator yet. D. McCune

  6. Resource Requirements • Parallel cluster (modest interconnect – “embarrassingly parallel MC algorithm). • For power balance and experimental data analysis, serial runs are often sufficient. • System tools for distributed computing and resource allocation. • NUBEAM parallel server deployment planned in current year– SciDAC Fusion Collaboratory. D. McCune

  7. Beam-ion distribution function for NSTX beam source A as calculated by TRANSP: 100,000 vs. 1,000,000 Monte Carlo beam particles Typically NPTCLS=5-10,000: fast execution (1-2 hours) on the sunfire cluster, but beam distribution output is noisy (not shown) Runs with NPTCLS=100,000: finish in reasonable time (~10 hours CPU time) and have good beam-ion distr. function resolution. 113525A06, A07_0.17s E. Ruskov D. McCune

  8. MPI-Parallel Module Server Serial TRANSP Run (Client #1) Input File* Package, e.g. XPLASMA** NetCDF state. Server Queue • MPI-Parallel TRANSP • Module Server(s): • NUBEAM monte carlo • TORIC5 full wave • GenRAY ray tracing • CQL3D fokker planck • GCNM transp. solver • ... … … Serial TRANSP Run (Client #2) Output File* Package, e.g. XPLASMA** NetCDF state. Serial TRANSP Run (Client #3) … *viability of method depends on keeping files small. Serial TRANSP Run (Client #N) **NTCC container module for equilibrium, profiles, distribution functions, etc. (http://w3.pppl.gov/NTCC) to be used for Fusion Simulation Project prototype and tested in TRANSP deployment. network D. McCune

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