---
title: GRAY user manual
author:
  - D. Farina[^1]
  - L. Figini[^1]
  - A. Mariani[^1]
  - M. Guerini Rocco[^2]
date: 'November 30, 2012. Updated: November 30, 2021'

lang: en-GB
language: english

# Bibliography
link-citations: true
citation-style: res/style.csl
reference-section-title: Bibliography
references:
  - id: gray
    title: 'A quasi-optical beam-tracing code for electron cyclotron
      absorption and current drive: GRAY'
    author:
      - family: Farina
        given: D.
    container-title: Fusion Science and Technology
    doi: 10.13182/fst07-a1494
    issue: 2
    issued: 2007-08
    page: 154-160
    publisher: Informa UK Limited
    type: article-journal
    volume: 52

  - id: gaussian-beam
    title: 'Gaussian light beams with general astigmatism'
    author:
      - family: Arnaud
        given: J. A.
      - family: Kogelnik
        given: H.
    container-title: Applied Optics
    doi: 10.1364/ao.8.001687
    issue: 8
    issued: 1969-08
    page: 1687
    publisher: The Optical Society
    type: article-journal
    volume: 8

  - id: cocos
    title: 'Tokamak coordinate conventions: COCOS'
    author:
      - family: Sauter
        given: O.
      - family: Medvedev
        given: S.Yu.
    container-title: Computer Physics Communications
    doi: 10.1016/j.cpc.2012.09.010
    issue: 2
    issued: 2013-02
    page: 293-302
    publisher: Elsevier BV
    type: article-journal
    volume: 184

  - id: marushchenko
    title: 'Current drive calculations with an advanced adjoint approach'
    author:
    - family: Marushchenko
      given: N. B.
    - family: Beidler
      given: C. D.
    - family: Maassberg
      given: H.
    container-title: Fusion Science and Technology
    doi: 10.13182/fst55-180
    issue: 2
    issued: 2009-02
    page: 180-187
    publisher: Informa UK Limited
    type: article-journal
    volume: 55

  - id: dispersion
    title: 'Relativistic dispersion relation of electron cyclotron waves'
    author:
    - family: Farina
      given: Daniela
    container-title: Fusion Science and Technology
    doi: 10.13182/fst08-a1660
    issue: 1
    issued: 2008-01
    page: 130-138
    publisher: Informa UK Limited
    type: article-journal
    volume: 53

  - id: angles
    title: ???
    author:
      - family: Zvonkov
        given: A.
      - family: Gribov
        given: Y.
      - family: Bindslev
        given: H.
    issued: 2003-3-5, 2003-4-5

# Font
mainfont: Libertinus Serif
mathfont: Libertinus Math
monofont: Fira Mono

# PDF output options
classoptions:
  - a4paper
  - 14pt
geometry:
  - top=2cm
  - bottom=2cm

# HTML output options
css: res/style.css

# pandoc-crossref options
linkReferences: true
tableEqns: true
...

[^1]: Istituto per la Scienza e Tecnologia dei Plasmi,
    Consiglio Nazionale delle Ricerche
    Via R. Cozzi, 53 - 20125 Milano, Italy

[^2]: Università degli Studi di Milano-Bicocca,
    Piazza dell'Ateneo Nuovo, 1 - 20126, Milano


# Introduction

The beam tracing code GRAY performs the computation of the quasi-optical
propagation of a Gaussian beam of electron cyclotron waves in a general tokamak
equilibrium, and of the power absorption and driven current [@gray].
The propagation of a general astigmatic Gaussian beam is described within the
framework of the complex eikonal approach in terms of a set of "extended" rays
that allow for diffraction effects. The absorbed power and the driven current
density are computed along each ray solving the fully relativistic dispersion
relation for electron cyclotron wave and by means of the neoclassical response
function for the current.

The aim of the present note is to document the current version of the GRAY
code, by describing the main code features and listing the inputs and outputs.
To this goal in [@sec:physics] the main equations and models used in the GRAY
code to compute Gaussian beam propagation, absorption and current drive are
summarized shortly. In [@sec:io-files], the details on the code inputs and
outputs are presented.