In this example the trajectory is calculated for a field coming from an imported data file. We first creat the data file by adding some undulator field, some noise, and exporting the field to a file. Several formats are possible (for more information see the All About Magnetic Fields tutorial.
# This has nothing to do with OSCARS, but it puts the matplotlib plots inline in the notebook %matplotlib inline # Import the OSCARS SR module import oscars.sr # Import basic plot utilities (matplotlib). You don't need these to run OSCARS, but it's used here for basic plots from oscars.plots_mpl import *
OSCARS v2.1.8 - Open Source Code for Advanced Radiation Simulation Brookhaven National Laboratory, Upton NY, USA http://oscars.bnl.gov firstname.lastname@example.org
# Create a new OSCARS object. Default to 8 threads and always use the GPU if available osr = oscars.sr.sr(nthreads=8, gpu=1)
We are only doing this so you don't have to download many data files.
# Clear any existing fields (just good habit in notebook style) and add an undulator field osr.clear_bfields() osr.add_bfield_undulator(bfield=[0, 1, 0], period=[0, 0, 0.049], nperiods=41) # Add some random imperfections for i in range(10): osr.add_bfield_gaussian( bfield=[0, 0.001 * (osr.rand() - 0.5), 0], sigma=[0, 0, 0.1*(osr.rand())], translation=[0, 0, 2 * (osr.rand() - 0.5)] ) # Export the field osr.write_bfield(ofile='EX006.dat', oformat='OSCARS', zlim=[-3, 3], nz=50000)
# Clear all magnetic fields! osr.clear_bfields() # Import the field from the file created above osr.add_bfield_file(ifile='EX006.dat', iformat='OSCARS') # Plot imported field plot_bfield(osr, -2, 2)
Here we add a particle beam making use of some of the defaults, namely:
* type='electron' * t0=0 * d0=[0, 0, 1]
One must specify ctstartstop. This is the start and stop time of the calculation. In this example we will start the calculation at t=0 and go to t=6 (given in units of ct) since the beam is relativistic. In this example you can specify the start time as less than 0 which is useful if you want to propogate the particle backwars in time. This is useful for instance if you have a bending magnet before the undulator that you wish to include.
clear_particle_beams() is called, again for convenience, but it is not necessary.
# Setup beam similar to NSLSII with different starting position from above # (this makes more sense for some scenarios) osr.clear_particle_beams() osr.set_particle_beam(x0=[0, 0, -3], energy_GeV=3, current=0.500) # Set the start and stop times for the calculation osr.set_ctstartstop(0, 6)
Now we calculate the trajectory and plot it. It is enough to call calculate_trajectory(). If you are doing other calculations (flux, spectra, power density) it is not necesary to call this since it is called internally.
# Run the particle trajectory calculation trajectory = osr.calculate_trajectory() # Plot the trajectory position and velocity plot_trajectory_position(trajectory) plot_trajectory_velocity(trajectory)