PFT seems to increase laser energy

[bzdjordje]

Modifying just the PFT beta with a sweep of values -0.4e-15, -0.2e-15, 0, 0.2e-15, 0.4e-15 seems to increase the laser energy away from the baseline Gaussian mode, while I believe it should remain constant. The field energy corresponds to the maximum field energy in the simulation box using reduced diagnostics. @MaxThevenet @RemiLehe

input_pft.txt

[ax3l]

Thanks! Is this only a problem in 2D (but conserved in 3D)?

[bzdjordje]

I have only tried this in 2D since it's for an ion acceleration application, but I can check in 3D as well.

[RemiLehe]

Thanks for reporting this @bzdjordje
Could you also post the script that you used in order to compute the energy?
Also: in which units is the energy that you quote on the plots?

Note that the formulas are defined here
In principle, this should always have the same energy (as beta changes - at least in 3D), but this formula does make a number of approximation, including the paraxial approximation, and it assumes that the longitudinal field (Ez) is negligible in the total energy.

[RemiLehe]

Well, actually, I had a look at the code, and it looks like my comment above is incorrect: the current code does not preserve the energy.
@bzdjordje Would you be able to try the code here: #3054 and to recompile and rerun your test?