Plasma density profile from file

[dmargarone]

Hi guys !!

Like external electron beam or field, is it possible to read the plasma density profile from file ?

For example, I have a density profile measured experimentally, I could fit this profile and make a similar density profile numerically. However, if we can read the experimentally measured profile directly in to the code it may be more realistic and accurate.

Thanks in advance. DM

[hightower8083]

dear @dmargarone

the question concerns rather python than FBPIC itself. The code accepts any function dens_func that can be 2D in (z,r) space or 3D in a full Cartesian space (x,y,z). In a simplest case, if you have 1D longitudinal profile, i.e. some array z_coord in microns and corresponding density n_p normalized to 1 (measured or from CFD simulation), you may define it with something like this:

dens_func = lambda z, r : np.interp(z, z_coord, n_p, left=0, right=0)

For 3D profiles, depending on your data, you may either consider combinations of 1D interpolators (like np.interp above), or a full 3D interpolator of you taste (see scipy.interpolate for more options)

[dmargarone]

Thank you so much @hightower8083 for answering this question.

Exactly as you mentioned, I have 1D longitudinal profile (data of 2 columns ). 1st column z-coordinate and 2nd column plasma density.

Sorry, but I have one query here ....

(1) why you wrote "lambda" in the dens_func ?

Thank you so so much. DM

[hightower8083]

lambda is a standard inline function definition in python, but if you are not familiar with it you may prefer to use a more common way:

import numpy as np

def dens_func(z, r):
    value = np.interp(z, z_coord, n_p, left=0, right=0)
    return value

or even better consider a scipy method (avoids reinititalization at each call, but make sure there's no NaN values in the input arrays)

from scipy.interpolate import interp1d

dens_func_interp = interp1d(z_coord, n_p, bounds_error=False, fill_value=0.0)

def dens_func(z, r):
    value = dens_func_interp(z)
    return value

[dmargarone]

Thank you Thank you Thank you @hightower8083

You are great teacher. You realized correctly that I am not good in Python. Actually, I started Python only after becoming a user of FBPIC. Basically, I am a C and Matlab user. Nowadays, I am trying to learn Python in parallel to FBPIC.

You all guys are so wonderful and kind that I have no words to praise you .... simply great !!

Thank you for helping on this issue. It is now really clear.

Lovingly, DM