titles_mcds
Titles: MCDS
=============
Contact: D. Wark, Oxford.
Revision History:-
================
2.03 D. Wark First version.
2.06 R. Komar Inclusion of shape factors for forbidden decays.
S. Brice Neutron capture MCDS included.
2.08 N. West New bank numbering scheme.
S. Brice Neutron capture MCDS broken into one for each isotope.
2.09 N. West Correct mistake in the HTML file.
3.02 G. McGregor Update neutron capture type 3 MCDS bank for new Cl
decay scheme.
Titles Files
------------
mc_generator.dat
Verification
------------
Description
-----------
These banks (MCDS = Monte Carlo Decay Scheme) contain decay schemes for
beta-gamma events and for the gammas resulting from neutron capture.
For a list of currently defined beta-gamma events see the file
mc_generator.dat.
Bank Number
----------
The bank number is the same as the interaction code (see id_interaction.html)
that the decay scheme describes, except the ccc is replaced by the decay scheme
variant number nnn, where nnn = 0 is ALWAYS the standard form. For example:-
341103000 Beta gamma decay of 24Na
341103001 Beta gamma decay of 24Na(IT) IT = Isomeric state
and:-
502103000 Beta gamma decay of 40K
502103002 Beta gamma decay of 40K (electron emission only)
Beta-Gamma Event Data Words
===========================
===========================
Fixed length Database Header. See titles_dbhdr.html
The first line contains information used for calculating the Fermi
function for the decay:
Entry Type Variable Description
----- ---- -------- -----------
1 I Z The atomic number Z of the daughter nucleus.
For positron emission, set Z negative.
2 I A The number of nucleons A in the nucleus.
Following this, there is one line for each decay branch. Each line has
thirteen entries, which are:
Entry Type Variable Description
----- ---- -------- -----------
1 F Prob. This is the branching ratio to this branch plus the
sum of all previous branches. For efficiency, the
branches are listed in order of descending probability.
The schemes do not necessarily list all possible
branches, if not, the probabilities are all scaled up
by the same amount to yield a total probability of 1.
(The last prob. is listed as 1.0001 to allow for error).
2 I Beta type This identifies the type of beta decay, 0 = allowed,
1 = 1st parity forbidden, 2 = second parity
forbidden, 11 = first unique forbidden, 12 = second
unique forbidden, 13 = third unique forbidden.
3 F E0 This is the endpoint for the decay electron (kinetic).
4 I NGAMMA The number of gammas in this branch (<=6).
5-10 F E gam. These are the gamma energies (padded with zeros).
11-13 F A,B,C Shape factor coefficients for the parity forbidden
decays. Unless you know the actual values, leave
them set to 0.
For FIRST parity forbidden decays, the shape factor is:
SF = 1 + A*E + B/E + C*E^2
where E is the total beta energy in electron mass (mc^2)
units, and A,B,C are in the appropriate units to make
the shape factor dimensionless. For a different
representation, see below.
For SECOND parity forbidden decays:
SF = q^2 + A*p^2 ( + B )
where q and p are the neutrino and electron momenta,
repsectively, and A is dimensionless. If the
absolute value of A is set smaller than 10^-10 in
the bank, then a default value of 1 is used in the
calculations. The value of B is 0 for second parity
forbidden decays, however, it has been included since
some FIRST parity forbidden decays are expressed using
the formula shown above. In such a case, set A and B,
and set the beta type to second parity forbidden.
Neutron Capture Event Data Words
================================
================================
Fixed length Database Header. See titles_dbhdr.html
There are three template for the MCDS banks for the gammas resulting from
neutron capture.
Type 1:- Single Resultant Gamma
===============================
Entry Type
----- ----
1 F Energy(MeV) of gamma
Type 2:- Many Resultant Gammas, Simple Decay Scheme
===================================================
Entry Type
----- ----
1 F Cumulative isotope braching ratio. If more than
one isotope of the same element can has its neutron
capture modelled then each isotope has its own MCDS
and this entry tells the code how to chose which
isotope captured the neutron. It is necessary as
the neutron transport code only deals with cross-
sections for natural abundances and so only signals
capture on, for instance, "natural" nickel
2 I The number of gamma branches modelled.
i+.. (i=3,8,13,...)
1 Cumulative branching ratio of the gamma branch
2 Energy of 1st gamma in the branch
3 Energy of 2nd gamma in the branch
4 Energy of 3rd gamma in the branch
5 Energy of 4th gamma in the branch
Type 3:- Many Resultant Gammas, Complex Decay Scheme
====================================================
Currently this MCDS type is only used for neutron capture on 35Cl.
The first six lines contain information on the six gamma cascades in
chlorine for which the angular correlations are known.
Entry Type
----- ----
i+.. (i=0,2,4,6,8,10)
+1 F The coefficient of the second Legendre polynomial
in COS theta describing the angular correlation
between the two gammas above.
+2 F The coefficient of the fourth Legendre polynomial.
There then comes a list of chlorine energy levels.
Entry Type
----- ----
13->87 F The energies(MeV) of the ground state, 73
excited states, and the capturing state of chlorine.
Then comes the top triangle of a 75x75 matrix where columns and rows
represent energy levels from the list above and the matrix entries give the
cumulative branching ratios from one level to the next.
Entry Type
----- ----
88->2862 F Cumulative branching ratios from one energy level to
another.
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