"""Some helper functions for determining which rates need screening"""
from pynucastro.nucdata import Nucleus
from pynucastro.rates import ApproximateRate
[docs]
class ScreeningPair:
"""a pair of nuclei that will have rate screening applied. We store a
list of all rates that match this pair of nuclei"""
def __init__(self, name, nuc1, nuc2, rate=None):
self.name = name
self.n1 = nuc1
self.n2 = nuc2
if rate is None:
self.rates = []
else:
self.rates = [rate]
[docs]
def add_rate(self, rate):
if rate not in self.rates:
self.rates.append(rate)
def __str__(self):
ostr = f"screening for {self.n1} + {self.n2}\n"
ostr += "rates:\n"
for r in self.rates:
ostr += f" {r}\n"
return ostr
def __eq__(self, other):
"""all we care about is whether the names are the same -- that conveys
what the reaction is"""
return self.name == other.name
[docs]
def get_screening_map(rates, *, symmetric_screening=False):
"""a screening map is just a list of ScreeningPar objects
containing the information about nuclei pairs for screening If
symmetric_screening=True, then for reverse rates, we screen using
the forward rate nuclei (assuming that we got here via detailed
balance).
"""
screening_map = []
# we need to consider the child rates that come with ApproximateRate
all_rates = []
for r in rates:
if isinstance(r, ApproximateRate):
all_rates += r.get_child_rates()
else:
all_rates.append(r)
for r in all_rates:
screen_nuclei = r.ion_screen
if symmetric_screening:
screen_nuclei = r.symmetric_screen
# screen_nuclei may be [] if it is a decay, gamma-capture, or
# neutron-capture
if not screen_nuclei:
continue
nucs = "_".join([str(q) for q in screen_nuclei])
scr = [q for q in screening_map if q.name == nucs]
assert len(scr) <= 1
if scr:
# we already have the reactants in our map, so we
# will already be doing the screening factors.
# Just append this new rate to the list we are
# keeping of the rates where this screening is
# needed -- if the rate is already in the list, then
# this is a no-op
scr[0].add_rate(r)
# if we got here because nuc == "He4_He4_He4",
# then we also have to add to "He4_He4_He4_dummy"
if nucs == "He4_He4_He4":
scr2 = [q for q in screening_map if q.name == nucs + "_dummy"]
assert len(scr2) == 1
scr2[0].add_rate(r)
else:
# we handle 3-alpha specially -- we actually need
# 2 screening factors for it
if nucs == "He4_He4_He4":
# he4 + he4
scr1 = ScreeningPair(nucs, screen_nuclei[0], screen_nuclei[1], r)
# he4 + be8
be8 = Nucleus("Be8", dummy=True)
scr2 = ScreeningPair(nucs + "_dummy", screen_nuclei[2], be8, r)
screening_map.append(scr1)
screening_map.append(scr2)
else:
scr1 = ScreeningPair(nucs, screen_nuclei[0], screen_nuclei[1], r)
screening_map.append(scr1)
return screening_map