"""This module provides a way to grab and store raw data for neutron scattering
lengths. This data comes from Neutron News, Vol. 3, No. 3, 1992, pp. 29-37 via
a NIST webpage (http://www.ncnr.nist.gov/resources/n-lengths/list.html). Please
contact Alan Munter, <alan.munter@nist.gov> for more information."""
from __future__ import print_function
import os
import re
import shutil
from pyne.utils import QA_warn
try:
import urllib.request as urllib2
except ImportError:
import urllib2
import numpy as np
import tables as tb
from .. import nucname
from .api import BASIC_FILTERS
QA_warn(__name__)
[docs]def grab_scattering_lengths(build_dir="", file_out='scattering_lengths.html'):
"""Grabs the scattering cross-section lengths for neutrons from the NIST website
or locally from this module."""
build_filename = os.path.join(build_dir, file_out)
local_filename = os.path.join(os.path.split(__file__)[0], file_out)
if os.path.exists(local_filename):
shutil.copy(local_filename, build_filename)
return
nist = urllib2.urlopen("http://www.ncnr.nist.gov/resources/n-lengths/list.html")
with open(build_filename, 'w') as f:
f.write(nist.read())
[docs]def nist_num(nist_data):
"""Converts a NIST style data point to a point.
Parameters
----------
nist_data : str
A nist data point.
Returns
-------
d : float or complex
a data point.
"""
nd = nist_data
while ('(' in nd) or (')' in nd):
nd_pre = nd.partition('(')
nd_post = nd.partition(')')
nd = nd_pre[0] + nd_post[2]
if (nd == "---") or (nd == ""):
nd = "0.0"
nd = nd.replace("<i>i</i>", 'j')
d = eval(nd)
return d
sl_dtype = np.dtype([
('nuc', int),
('b_coherent', np.complex128),
('b_incoherent', np.complex128),
('xs_coherent', float),
('xs_incoherent', float),
('xs', float),
])
scat_len_data = "[ aeE()<>i/.+\d-]+?"
scat_len_space = "[ \t]+"
scat_len_pattern = "<td>{space}(?P<iso>[A-Za-z\d]+){space}<td>{space}(?P<conc>{data}){space}<td>{space}(?P<b_coherent>{data}){space}<td>{space}(?P<b_incoherent>{data}){space}<td>{space}(?P<xs_coherent>{data}){space}<td>{space}(?P<xs_incoherent>{data}){space}<td>{space}(?P<xs>{data}){space}<td>{space}(?P<xs_a>{data}){space}<tr>".format(data=scat_len_data, space=scat_len_space)
[docs]def parse_scattering_lengths(build_dir):
"""Converts to scattering lenth data to a numpy array."""
build_filename = os.path.join(build_dir, "scattering_lengths.html")
# Read in cinder data file
with open(build_filename, 'r') as f:
raw_data = f.read()
sl_data = []
# Iterate over all isotopes in the table
for m in re.finditer(scat_len_pattern, raw_data):
md = m.groupdict()
slrow = (nucname.id(md['iso']),
nist_num(md['b_coherent']) * (1E-13),
nist_num(md['b_incoherent']) * (1E-13),
nist_num(md['xs_coherent']),
nist_num(md['xs_incoherent']),
nist_num(md['xs']))
sl_data.append(slrow)
sl_array = np.array(sl_data, dtype=sl_dtype)
return sl_array
[docs]def make_scattering_lengths_table(nuc_data, build_dir=""):
"""Adds the neutron sacttering lengths to the nuc_data library.
Parameters
----------
nuc_data : str
Path to nuclide data file.
build_dir : str
Directory to place html files in.
"""
sl_array = parse_scattering_lengths(build_dir)
# Open the HDF5 File
db = tb.open_file(nuc_data, 'a', filters=BASIC_FILTERS)
# Ensure that the appropriate file structure is present
if not hasattr(db.root, 'neutron'):
# Create neutron group
neutron_group = db.create_group('/', 'neutron', 'Neutron Data')
# Init the neutron fission product info table
sl_table = db.create_table('/neutron/', 'scattering_lengths',
np.empty(0, dtype=sl_dtype),
'Neutron Scattering Lengths, b [cm], sigma [barns]',
expectedrows=len(sl_array))
sl_table.append(sl_array)
# Write the table
sl_table.flush()
# Close the hdf5 file
db.close()
[docs]def make_scattering_lengths(args):
"""Controller function for adding scattering lengths."""
nuc_data, build_dir = args.nuc_data, args.build_dir
# Check that the table exists
with tb.open_file(nuc_data, 'a', filters=BASIC_FILTERS) as f:
if hasattr(f.root, 'neutron') and hasattr(f.root.neutron, 'scattering_lengths'):
print("skipping scattering lengths data table creation; already exists.")
return
# Grab the raw data
print("Grabbing the scattering length data.")
grab_scattering_lengths(build_dir)
# Make scatering table once we have the data
print("Making neutron scattering length table.")
make_scattering_lengths_table(nuc_data, build_dir)
