# Introduction

## Case studied

This case is a benchmark case of ITG in W7-X stellarator using V4.2.0, and results are compared with V4.0.2.
Petsc solver is used in this case. Command: module load cray-petsc/3.6.1.0 cray-hdf5-parallel/1.8.16 cray-netcdf-hdf5parallel/4.4.0

## Physics included

This is currently an adiabatic electron, electro-static simulation.

# GTC version requirement

GTC after 2015, and results of V4.2.0 are given in this document.

# GTC Run Preparation

1. build the source code with 

        $ ICONFIG=TOROIDAL3D

2. change in source code: call smooth_para twice in smooth.F90, Line83 is added.

Line82      call smooth_para(farraytmp)
Line83      call smooth_para(farraytmp) !only used in W7-X ITG case, added by hongyu wang.

3. prepare the input files and job submission files as follows. 

# Datafiles needed for VMEC run

## general data file

* maxwell.dat: data lookup table for collision process in Maxwellian

## specific data files

* profile.dat: 1D equilibrium profiles, specific to a shot number and time,
  the same as other GTC runs. See [DataFileFormat.md](../input/DataFileFormat.md) for details.
  **profile.dat is updated in V4.2.0, and new profile.dat for v4.2.0 and old profile.dat for v4.0.2 or early versions are all included.

* spdata.dat: VMEC equilibrium file, specific to a shot number and time.
  See [DataFileFormat.md](../input/DataFileFormat.md) for details.

# Example data files

Same data files can be found on UCI phoenix server:
/home/hwang/w7x/v4.2.0benchmark_w7x_itg/

#error
Growth rate is 2.95, and error is 2.93%. Real frequency is 4.1888, and error is 4.33%. Growth rate and real frequency are normalized by Cs/R0. [n, m]=[185, 205].