BEER_optics

Neutron optics model for the diffractometer BEER at the European Spallation Source.
Author: Jan Saroun, saroun@ujf.cas.cz
Copyright (c) 2020 Nuclear Physics Institute, CAS, Rez, http://www.ujf.cas.cz

Repository: https://github.com/saroun/ess_beer_model

Summary

This Python package provides the definition of neutron optics geometry for the diffractometer BEER@ESS and associated tools:

• Export of neutron beam axis coordinates and various functions for coordinate transformations between target, beamport and instrument reference frames.
• Export of the table of neutron optics components (a text version of the document ESS-0478295 - BEER Optics Specifications)
• Definition of components settings for reference operation modes of BEER (see ESS-0238217 - Optics Report for the BEER Instrument)
• Calculation of chopper transmission functions for these reference modes
• Binding to the simulation program McStas: export of instrument configuration files, functions for running simulations and plotting results.
• Binding to the simulation program SIMRES: export of input scripts, functions for running simulations and plotting results.

See also:

Diffractometer BEER: https://europeanspallationsource.se/instruments/beer
McStas: http://www.mcstas.org
SIMRES: https://github.com/saroun/simres

Quick guide

Install:

# from root package directory call
pip install -e .
# check pip docs for other ways of installation

Jupyter notebook:

Examples of basic usage and simulations of the primary instrument are provided in Jupter notebook files:

• ess_beer_model.ipynb
• ess_beer_simulation.ipynb

Python scripts:

Get beam axis, beam size and coordinate conversions:

import beer.geometry as bg

# get beam axis coordinates for given distance. The result is converted 
# to required coordinate system (ISCS, TCS or FP). Distance is always defined
# as x_ISCS.
r_ISCS = bg.beamAxis(145000, coord='ISCS')

# get beam axis angle in [rad] with respect to x-axis of given coordinate system
angle = bg.beamAngle(145000, coord='FP')

# get beam size at given distance: left, right, top, bottom, width and height, converted to required coordinates.
[left, right, top, bottom, width, height] = bg.beamSize(145000, coord='FP')

# convert a point from ISCS to TCS coordinates
r_TCS = bg.ISCS2TCS(r_ISCS)
# or to FP (W2 focal point) coordinates
r_FP = bg.ISCS2FOC(r_ISCS)

Export configuration tables for BEER into given directory:
BEER_components.txt, the contents of the components table, ESS-0478295.
BEER_beam.txt, a table with beam axis coordinates in three reference frames (TCS, W2, ISCS).
BEER_modes.txt, reference operation modes with corresponding components settings.
The latest versions of these tables are stored in the repository (see ./data/*)

import beer
beer.reportTables(outdir='') # you can specify output directory

Calculate and plot chopper transmission functions for various operation modes:

beer.reportChoppers(outdir='')

Plot profiles of neutron guides in given coordinate system. Options are: ISCS or FP (focal point for W2 beamport):

beer.plotGuides(outdir='', coord='ISCS')

Run simulation with McStas (if installed):

The latest BEER instrument file for the primary beamline (source to sample) is available at beer/resources/BEER_reference.instr. The beer package can be used for running the simulations as follows.

Try the script run_mcstas.py, e.g.:

python run_mcstas.py n=1e6 modes=F0 force=1 plot=1 workpath=my_path

or use the beer.mcstas package:

import beer.mcstas as mcstas

# configure workspace and McStas environment 
mcstas.configure(workpath='my_path',
                PATH='/usr/bin', 
                MCSTAS='/usr/share/mcstas/3.4')

# create instrument file 
mcstas.create_instrument()

# compile instrument file
mcstas.compile_instrument(force=True)

# run simulation for selected modes
result = mcstas.execute(modes='F0,F1', n=1e6, plot=True)

# or run simulation for all modes 
result = mcstas.execute(modes='all', n=1e7, plot=True)

# to replot results:  
mcstas.plot_result(result, title='Test simulation', pdf='myresult')

# or run simulation for selected modes
result = mcstas.execute(modes='F0,F1', n=1e6, plot=True)

# or run simulation for all modes 
import beer.modes as bmodes
result = mcstas.execute(modes=bmodes.getModeKeys(), n=1e7, plot=True)

# Simulation using an instrument template provided by user
mcstas.create_instrument(template='BEER_user', 
                        inpath='.', 
                        instname='BEER_Vexperiment')
mcstas.compile_instrument(force=True)
result = mcstas.execute(modes='F0', n=1e6, plot=True, monoutputs=1)

# Only generate the instrument file
mcstas.conf.parseTemplate(instname='my_instrument_name', 
                        template='my_instrument_template',
                        inpath='.',
                        outpath='.')

Run simulations with SIMRES (if installed):

First define the JRE environment variable to point to the Java RE interpreter.

Then try the script run_simres.py, e.g.:

python run_simres.py runetup=1 modes=F0,PS1 n=1e4 

or use the beer.simres package:

import beer.simres as simres
import beer.modes as bmodes

# Configure environment to define workspace directory.
# Optionally, you can also set `java` path and `simresdir` to define the 
# JRE interpreter and SIMRES installation directory, respectively.
simres.configure(workpath='my_path')

# Create script `BEER_setup.inp`  for updating instrument configuration. 
# Set scriptonly=False to also start SIMRES and run the script.
simres.update(scriptonly=False)

# Run a single simulation for given BEER operation mode
simres.execute(modes='PS2', n=10000, plot=True)

# Run simulation for all reference modes (takes a long time):
simres.execute(modes=bmodes.getModeKeys(), n=10000, plot=True)