gctransform.c File Reference

Module for performing guiding center transformations. More...

#include "offload.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "ascot5.h"
#include "consts.h"
#include "physlib.h"
#include "gctransform.h"

Go to the source code of this file.

Functions
void	gctransform_setorder (int order)
	Set the order of the transformation.
void	gctransform_particle2guidingcenter (real mass, real charge, real *B_dB, real r, real phi, real z, real pr, real pphi, real pz, real *R, real *Phi, real *Z, real *ppar, real *mu, real *zeta)
	Transform particle to guiding center phase space.
void	gctransform_guidingcenter2particle (real mass, real charge, real *B_dB, real R, real Phi, real Z, real ppar, real mu, real zeta, real *r, real *phi, real *z, real *pparprt, real *muprt, real *zetaprt)
	Transform guiding center to particle phase space.
void	gctransform_pparmuzeta2prpphipz (real mass, real charge, real *B_dB, real phi, real ppar, real mu, real zeta, real *pr, real *pphi, real *pz)
	Transform particle ppar, mu, and zeta to momentum vector.

Variables
static int	GCTRANSFORM_ORDER = 1

Detailed Description

Module for performing guiding center transformations.

The guiding center transformation is done both ways between particle phase-space [r, phi, z, pr, pphi, pz] and guiding center phase-space [R, Phi, Z, ppar, mu, zeta] to first order (both in spatial and momentum space coordinates).

The guiding genter motion is defined from a basis {bhat, e1, e2}, where bhat is magnetic field unit vector. e1 and e2 are chosen so that e1 = (bhat x z) / |bhat x z| and bhat x e1 = e2. Thus we are assuming that magnetic field is never parallel to z axis.

This module works as follows:

• particle to guiding center transformation is accomplished by calling gctransform_particle2guidingcenter()
• guiding center to particle transformation is accomplished by calling gctransform_guidingcenter2particle() which gives [r, phi, z, ppar, mu, zeta] in particle coordinates. To obtain [r, phi, z, pr, pphi, pz], first evaluate magnetic field at particle position and then call gctransform_pparmuzeta2pRpphipz().

The transformation is relativistic.

Reference: "Guiding-center transformation of the radiation-reaction force in a nonuniform magnetic field", E. Hirvijoki et. al. https://arxiv.org/pdf/1412.1966.pdf

Definition in file gctransform.c.

Function Documentation

gctransform_setorder()

void gctransform_setorder

(

int

order

)

Set the order of the transformation.

Parameters

order

order which is either zero or one

Definition at line 62 of file gctransform.c.

gctransform_particle2guidingcenter()

void gctransform_particle2guidingcenter	(	real	mass,
		real	charge,
		real *	B_dB,
		real	r,
		real	phi,
		real	z,
		real	pr,
		real	pphi,
		real	pz,
		real *	R,
		real *	Phi,
		real *	Z,
		real *	ppar,
		real *	mu,
		real *	zeta )

Transform particle to guiding center phase space.

The transformation is done from coordinates [r, phi, z, pr, pphi, pz] to [R, Phi, Z, ppar, mu, zeta]. If particle is neutral, the transformation will be in zeroth order both in real and momentum space as that transformation is valid when q = 0.

Parameters

mass	mass [kg]
charge	charge [C]
B_dB	gradient of magnetic field vector at particle position
r	particle R coordinate [m]
phi	particle phi coordinate [rad]
z	particle z coordinate [m]
pr	particle momentum R component [kg m/s]
pphi	particle momentum phi component [kg m/s]
pz	particle momentum z component [kg m/s]
R	pointer to guiding center R coordinate [m]
Phi	pointer to guiding center phi coordinate [rad]
Z	pointer to guiding center z coordinate [m]
ppar	pointer to guiding center parallel momentum [kg m/s]
mu	pointer to guiding center magnetic moment [J/T]
zeta	pointer to guiding center gyroangle [rad]

Definition at line 90 of file gctransform.c.

gctransform_guidingcenter2particle()

void gctransform_guidingcenter2particle	(	real	mass,
		real	charge,
		real *	B_dB,
		real	R,
		real	Phi,
		real	Z,
		real	ppar,
		real	mu,
		real	zeta,
		real *	r,
		real *	phi,
		real *	z,
		real *	pparprt,
		real *	muprt,
		real *	zetaprt )

Transform guiding center to particle phase space.

The transformation is done from coordinates [R, Phi, Z, ppar, mu] to [r, phi, z, ppar_prt, mu_prt, zeta_prt]. If particle is neutral, the transformation will be in zeroth order both in real and momentum space as that transformation is valid when q = 0.

Parameters

mass	mass [kg]
charge	charge [C]
B_dB	gradient of magnetic field vector at guiding center position
R	guiding center R coordinate [m]
Phi	guiding center phi coordinate [rad]
Z	guiding center z coordinate [m]
ppar	guiding center parallel momentum [kg m/s]
mu	guiding center magnetic moment [J/T]
zeta	guiding center gyroangle [rad]
r	pointer to particle R coordinate [m]
phi	pointer to particle phi coordinate [rad]
z	pointer to particle z coordinate [m]
pparprt	pointer to particle parallel momentum [kg m/s]
muprt	pointer to particle magnetic moment [J/T]
zetaprt	pointer to particle gyroangle [rad]

Definition at line 329 of file gctransform.c.

gctransform_pparmuzeta2prpphipz()

void gctransform_pparmuzeta2prpphipz	(	real	mass,
		real	charge,
		real *	B_dB,
		real	phi,
		real	ppar,
		real	mu,
		real	zeta,
		real *	pr,
		real *	pphi,
		real *	pz )

Transform particle ppar, mu, and zeta to momentum vector.

The transformation is done from coordinates [R, Phi, Z, ppar, mu] to [r, phi, z, pr, pphi, pz]. The transformation is done to first order.

Parameters

mass	mass [kg]
charge	charge [C]
B_dB	gradient of magnetic field vector at particle position
phi	particle phi coordinate [rad]
ppar	particle parallel momentum [kg m/s]
mu	particle magnetic moment [J/T]
zeta	particle gyroangle [rad]
pr	pointer to particle momentum R-component [kg m/s]
pphi	pointer to particle momentum phi-component [kg m/s]
pz	pointer to particle momentum z-component [kg m/s]

Definition at line 554 of file gctransform.c.

Variable Documentation

GCTRANSFORM_ORDER

int GCTRANSFORM_ORDER = 1

static

Order to which guiding center transformation is done in momentum space.

Definition at line 53 of file gctransform.c.