Hi Danila,

thanks for the question!

Which version of PIConGPU you are using?
The latest release, 0.1.2, changed the documentation in the
laserConfig.param a bit because it was not precise before it.


I got your question regarding the temporal envelope (pulse length) of
the Gaussian Beam. I actually just fixed it for 2D last year but we can
double check tomorrow if the documentation is up-to-date.

  https://github.com/ComputationalRadiationPhysics/picongpu/pull/1090

So far, great you found the implementation yourself! :) I am missing the
sqrt on the first view, too but let us check tomorrow.


Cheers,
Axel

On 02.05.2016 13:06, Khikhlukha Danila wrote:
> Hi
> all,                                                                                                                
>
>                                                                                                                        
>
> I have a couple of short questions regarding the Gaussian beam
> initialization.                                        
>                                                                                                                        
>
> 1. As far as I understood from the code comments
> (simulation_defines/param/laserConfig.param)                            
> the initialization for laser pulse is done based on the sigma of the
> intensity envelope. However in the code          
> (src/picongpu/include/fields/laserProfiles/laserGaussianBeam.hpp) it
> looks like PULSE_LENGTH is the sigma of electrical field envelope.
> I also wasn't able to find any conversion (namely
> sqrt(2))                                                            
>                                                                                                                        
>
> 2. So at the moment I'm assuming that the initialization of the Gaussian
> beam is done based on the sigma of an electrical field envelope.
> So if we consider k = 2*sqrt(2*log(2))=2.3548 as a coefficient between
> FWHM and sigma of the Gaussian curve            
> then the coefficient between sigma of an electrical field and FWHM of
> the intensity becomes sqrt(2)/k = 0.6006.        
> However, in comments for laserGaussianBeam it is stated the number
> 1./1.17741 = 0.8493 and I'm not sure what is it.      
>                                                                                                                        
>
> Can you please double check if comments are up-to-date? Otherwise I got
> something wrong in the description.          
>                                                                                                                        
>
> Thank
> you,                                                                                                  
>
> Danila.

--

Axel Huebl
Phone +49 351 260 3582
https://www.hzdr.de/crp
Computational Radiation Physics
Laser Particle Acceleration Division
Helmholtz-Zentrum Dresden - Rossendorf e.V.

Bautzner Landstrasse 400, 01328 Dresden
POB 510119, D-01314 Dresden
Vorstand: Prof. Dr.Dr.h.c. R. Sauerbrey
          Prof. Dr.Dr.h.c. P. Joehnk
VR 1693 beim Amtsgericht Dresden