PRBench / tasks /task_bude_2021 /instruction.md
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Paper Reproduction Task

You are given a plasma physics paper to reproduce. Your goal is to read the paper, understand its methodology, and implement electromagnetic wave simulations to reproduce 7 key figures and 1 table.


1. Article Information

Field Value
Title Accelerating simulations of electromagnetic waves in hot, magnetized fusion plasmas
Authors R H S Budé, D Van Eester, J van Dijk, R J E Jaspers and A B Smolders
DOI 10.1088/1361-6587/abd619
Paper File Bude2021.md (in the same task directory)

2. What You Must Do

Step 1: Read and Analyze the Paper

Read the full paper at Bude2021.md. Write a detailed analysis document at reproduction/ANALYSIS.md that covers:

  1. Methodology: Describe the three electromagnetic wave solver models (Truncated Taylor, Truncated Polynomial Fit, All-Orders)
  2. Key Formulas: List and explain every formula needed for the reproduction, including:
    • The 1D Helmholtz equation
    • Hot plasma dielectric tensor (Stix/Swanson notation)
    • Plasma Dispersion Function
    • Differential operator replacement for polynomial fit model
    • RRSE error metric
    • Power absorption calculation
  3. Algorithm Details: Describe the polynomial fitting procedure, finite difference stencil construction, and boundary condition implementation
  4. Physical Observables: Explain what each figure/table measures and its physical significance

Step 2: Implement the Simulation

Write all code under reproduction/. You need:

  • Core simulation modules (see Section 6 below)
  • Individual scripts for each figure/table

Step 3: Generate Data Files

Run your scripts to produce CSV data files under data/. See Section 5 for exact specifications.


3. Input Parameters

3.1 Machine Parameters (JET-like)

Parameter Symbol Value Unit
Major Radius $R_0$ 2.97 m
Minor Radius $a$ 1.05 m
Spill-over Radius $a_s$ 1.35 m
Magnetic Field Axis $B_0$ 3.45 T
Toroidal Mode $n_{\text{tor}}$ 27 -
Frequency $f$ 51.0 MHz

3.2 Plasma Profiles

Density ($n$) and Temperature ($T$):

  • Core ($|x| < a_p$): $G_{\text{core}}(x) = (G_0 - G_p)(1 - (x/a_p)^2)^\alpha + G_p$
  • Edge ($|x| \ge a_p$): $G_{\text{edge}}(x) = G_p e^{-|x-a_p|/\lambda}$
  • Transition point $a_p = 0.95$ m.

Specific Coefficients:

Profile Axis Value ($G_0$) Edge Value ($G_s$) $\alpha$ $\lambda$
Density ($n_e, n_i$) $7 \times 10^{19}$ m$^{-3}$ $2 \times 10^{19}$ m$^{-3}$* 1.0 0.05
Temperature ($T_e, T_i$) 5 keV 100 eV 1.5 0.05

Note: Paper text says $n_s = 2 \times 10^{19}$, $G_p$ must be calculated to ensure continuity or assumed $G_p \approx G_s$ given the context.

Species:

  • Deuterium (Major): Fully ionized.
  • Hydrogen (Minor): 5% concentration ($n_H = 0.05 n_e$, $n_D = 0.95 n_e$).

4. Banned Libraries & Practices

The following are NOT allowed:

Banned Reason
plasma-py (simulation modules) Must implement dielectric tensor and wave solvers from scratch.
Closed-source solvers Code must be pure Python/NumPy/SciPy.
Symbolic Math (SymPy) Numerical differentiation/fitting should be used as per the paper.

Allowed: numpy, scipy (specifically scipy.special for Bessel/Error functions, scipy.sparse, scipy.linalg).


5. Data Files to Reproduce

5.1 Figure 2: Plasma Profiles

File: data/fig2_profiles.csv

  • X-axis: $x$ [m] (-1.5 to 1.5)
  • Y-axes: $n_e$ [$10^{19}$ m$^{-3}$], $T_e$ [keV]
  • Description: Verify the parabolic core and exponential edge implementation.

5.2 Figures 3 & 4: Dielectric Tensor Approximation

File: data/fig3_4_tensor_fit.csv

  • Context: $x = -0.1$ m (Hydrogen resonance layer).
  • X-axis: Normalized wavenumber $k_x \rho_{LH}$ (-3 to 3).
  • Y-axes: $\text{Re}(\epsilon_{11})$.
  • Series: Calculated exact values, 2nd Order Taylor, 6th Order Polynomial Fit.
  • Fit Window: $W = 1.0$ (approx, check paper visual).

5.3 Figure 5: Electric Field Comparison

File: data/fig5_efield.csv

  • Domain: $-0.9 < x < -0.1$ m (IBW region).
  • Resolution: $N = 2017$.
  • Y-axis: $|E_x|$ [V/m].
  • Series: Truncated Taylor, Truncated Polynomial ($N_p=8, W=1.2$).
  • Note: The paper compares these against All-Orders. If All-Orders is too expensive, comparing Taylor vs Poly is sufficient.

5.4 Figure 6: Absorbed Power Distribution

File: data/fig6_power.csv

  • Description: Comparison of power absorption profiles derived from Poynting flux (Eq 50).
  • X-axis: $x$ [m] (-1.5 to 1.5).
  • Y-axis: $P_{abs}$ [arbitrary units].
  • Series:
    • Per Species: Electron (e), Hydrogen (H), Deuterium (D).
    • Total Power.
  • Models:
    • Truncated Taylor (illustrating unphysical oscillations/smearing).
    • Truncated Polynomial Fit ($N_p=8$) (proxy for All-Orders if necessary, as they are visually identical in the paper).
  • Calculation: $\vec{J}p$ must be calculated by applying the respective differential operator ($\bar{\bar{M}}{op}$) to the solution field $\vec{E}$.

5.5 Figure 7: Convergence (RRSE)

File: data/fig7_error_scaling.csv

  • X-axis: Number of grid points $N$ (Log scale, 100 to 10,000).
  • Y-axis: RRSE (Log scale).
  • Series: Truncated Taylor, Truncated Polynomial Fit ($N_p=8$).
  • Reference: High resolution Polynomial Fit ($N=12601$) can act as proxy for "All-Orders" if full spectral code is not implemented.

5.6 Figure 8: Computational Time

File: data/fig8_timing.csv

  • X-axis: $N$ (Log scale).
  • Y-axis: Time [s] (Log scale).
  • Series: Matrix Setup Time, Matrix Solve Time (for Poly and Taylor models).

5.7 Table 1: Computational Cost Extrapolation

File: data/table1_extrapolation.csv

  • Description: Extrapolation of runtime scaling to 2D and 3D cases based on 1D benchmarks.
  • Inputs: Slope ($\alpha$) and intercept data derived from Figure 8 (Timing).
  • Methodology:
    1. Fit: Perform linear regression on log-log timing data (from Fig 8) for $N > 2000$ to obtain scaling laws $T \propto N^\alpha$ for Setup and Solve phases.
    2. Extrapolate: Calculate predicted times for:
      • $N_{2D} = 200^2 = 40,000$
      • $N_{3D} = 200^3 = 8,000,000$
    3. Dimensional Scaling: Apply the paper's approximation that computational time scales with stencil size $s$ raised to the dimension $D$ ($t \propto s^D$).
      • Truncated Taylor: $s=3$.
      • Truncated Polynomial: $s=9$ (for $N_p=8$).
  • Output Columns: Model Name, Matrix Setup $\alpha$, Matrix Invert $\alpha$, Stencil Size, Time (1D), Time (2D), Time (3D).

5.8 Figure 9: Parameter Sweep (RRSE vs Fit Window)

File: data/fig9_param_sweep.csv

  • Context: Section 6, analyzing the sensitivity of the Truncated Polynomial Fit model to the window size $W$ and polynomial order $N_p$.
  • Fixed Parameter: Grid resolution $N = 2017$.
  • X-axis: Fit Window $W$ ($0.5$ to $3.0$, step $\approx 0.1$).
  • Y-axis: RRSE (Log scale).
  • Series:
    • Polynomial Orders: $N_p \in {4, 6, 8, 10, 12}$.
    • Baseline: Truncated Taylor model error (constant line).
  • Reference: Use a high-resolution simulation ($N \approx 12601$, $N_p=12$) as the ground truth for error calculation.

5.9 Figure 10: Component Approximation

File: data/fig10_function_approx.csv

  • Context: Section 7 (Discussion), comparing approximation methods for the specific term $f(k) = I_n(\lambda)e^{-\lambda}$ (where $\lambda = \frac{1}{2} k^2 \rho^2$).
  • Parameters: Use $n=0$ (Modified Bessel function of the first kind) and normalized units where $\rho=1$.
  • X-axis: Normalized wavenumber $k \rho$ (Range: $-2.5$ to $2.5$).
  • Y-axis: Function Value.
  • Series:
    1. Exact: $I_0(0.5 k^2) e^{-0.5 k^2}$.
    2. Taylor: 4th Order Taylor expansion around $k=0$.
    3. Polynomial Fit: 4th Order fit over window $W=2$ (i.e., fit range $[-2, 2]$).

6. Code Structure

6.1 Core Modules

Path: reproduction/

  1. plasma.py:
    • Functions for $n(x)$, $T(x)$, $B(x)$.
    • get_plasma_parameters(x) returning $\omega_{pj}, \Omega_{cj}, v_{th}, \rho_L$.
  2. dielectric.py:
    • calc_K_tensor(x, k_x, ...): Implements Eq (11)-(18).
    • Uses scipy.special.wofz for $Z(\zeta)$.
  3. solvers.py:
    • TaylorSolver: Constructs sparse matrix using Eq (40)-(43).
    • PolyFitSolver:
      • Performs polynomial fitting of tensor elements.
      • Constructs sparse matrix using Eq (46)-(48).
      • Handles Finite Difference stencils for high order derivatives.
  4. run_sim.py:
    • Orchestrates the grid generation, solving, and data export.

6.2 Figure Scripts

Figure/Table Script Path
Fig 2 reproduction/fig2_profiles.py
Fig 3,4 reproduction/fig3_4_tensor.py
Fig 5 reproduction/fig5_fields.py
Fig 6 reproduction/fig6_power.py
Fig 7 reproduction/fig7_convergence.py
Fig 8 reproduction/fig8_timing.py
Fig 9 reproduction/fig9_params.py
Fig 10 reproduction/fig10_approx.py
Table 1 reproduction/table1_scaling.py

6.3 Analysis Document

Path: reproduction/ANALYSIS.md

Must contain your analysis of the paper's methodology and all formulas needed for reproduction.

6.4 Output Directories

  • Data files: data/
  • Code files: reproduction/

7. Deliverables Summary

Upon completion, the following files must exist:

  1. reproduction/ANALYSIS.md — Your methodology and formula analysis
  2. reproduction/plasma.py through reproduction/run_sim.py — Core simulation modules
  3. reproduction/fig2_profiles.py through reproduction/table1_scaling.py — Figure/table scripts
  4. data/fig2_profiles.csv through data/table1_extrapolation.csv — Output data files (9 total)

Export data with 8 decimal places (%.8e).


8. Reproduction Requirements

8.1 Computational Constraints

Requirement Value Notes
Memory 8 GB High N simulations (10k+) require sparse matrices.
Precision Complex Double complex128 in numpy is essential.
Optimization Vectorization Tensor calculation must be vectorized over $k$ or $x$.
Total Time Limit ~4 hours For all figures, assuming 1D models only.

8.2 Output Format

  • Data Files: CSV format with headers.
  • Precision: 8 decimal places for floating point values.