implement python method to convert E-field values to photon number density

radiasoft / rslaser_old

Integrated modeling of CPA crystal-based laser amplifiers

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implement python method to convert E-field values to photon number density #13

Closed bruhwiler closed 1 year ago

bruhwiler commented 1 year ago

We've decided to use the 'arbitrary units' setting in SRW, so that we can use SI units for our calculations.

The following sub-issues need to be resolved:

[ ] from user-specified pulseE [J] and laser pulse dimensions; infer the correct multiplicative factor to obtain E [V/m] from SRW
[ ] for an SRW wavefront, wavelength & slice width (in [s] or [m]), calculate the number of photons in each grid cell

bruhwiler commented 1 year ago

A secondary consideration is where on the cell (side, vertices, center) are the E-field values are known. Initially, we can assume they are known in the cell centers.

bruhwiler commented 1 year ago

Start by creating a notebook to demonstrate.

bruhwiler commented 1 year ago

In the LaserPulseSlice constructor, the ds variable should be self.ds so that the slice length can be obtained. For now, a work around is to use self.num_sig_long, self.sig_s and the number of slices to calculate this externall.

pulseE is specified in the params object for LaserPulseSlice, which I think is kind of strange. It would be more natural to specify the energy in the LaserPulse as a whole, although either approach can work.

Our working model is that slices do not have longitudinal structure, so one must assume each slice is a flat top. If one specifies a single slice, then this is obviously wrong. However, maybe that's OK, because a single-slice representation is not going to be accurate in any case. We want the algorithm to work well in the limit that N >> 1

bruhwiler commented 1 year ago

@k-wolfinger -- please check whether the wavefront intensity that results from a single-slice instantiation is consistent with the user-specified value of self.pulseE

bruhwiler commented 1 year ago

Neither the LaserPulse nor the LaserPulseSlice constructors are creating a data member from pulseE, so it is not possible to query a pulse or a slice for its energy.

k-wolfinger commented 1 year ago

Currently not passing information on the pulse length to srw. Fix this by multiplying pulseE by a factor proportional to the length of the slice.