Network Generator v3.00 Tutorial 2.

THE NETWORK GENERATOR TUTORIAL

2. How to select reaction rates other than the default ones. 2a. First step: go to Individual Reaction. Type in the requested reaction, and
provide the bibliographic index for the requested rate:

for reactions from NACRE:

1 = NACRE nominal rate
2 = NACRE lower limit
3 = NACRE upper limit

10 = Hauser-Feshbach (if Z >= 8)
11 = most recent rate in use before NACRE (generally CF88, as listed here)
12 = second most recent rate in use before NACRE
13 = etc..

100 = forces the use of Iliadis et al. table of proton-capture rates on 20 < A < 40 nuclei (2001, ApJS 134, 151), when available

401 = forces the use of nominal value...
402 = forces the use of lower value...
403 = forces the use of upper value...

Descouvemont et al. compilation of Big Bang nucleosynthesis reaction rates

for reactions not in NACRE:

1 = most recent rate [usually Iliadis et al. 2001 for proton-capture reactions, or Descouvemont et al. (2004)]

10 = Hauser-Feshbach (if A > 8)
11 = most recent rate before Iliadis et al. (usually CF88, as listed here)
12 = second most recent rate etc.. (as listed here)

100 = forces the use of Iliadis et al. rate when available

200 = forces the use of Bao et al. table of radiative neutron-capture rates (2000, Atomic Data and Nucl. Data Tables 75, 1)

401 = forces the use of nominal value...
402 = forces the use of lower value...
403 = forces the use of upper value...

Descouvemont et al. compilation of Big Bang nucleosynthesis reaction rates

for weak-interaction rates:

1 = nominal rate from Goriely (1999, Astron. Astrophys. 342, 881; Table available in electronic form), updating Takahashi & Yokoi (1987, Atomic Data Nucl. Data Tables 36, 375) table
2 = low rate from Goriely (1999)
3 = high rate from Goriely (1999)

4 = forces the use of Takahashi & Yokoi (1987, Atomic Data Nucl. Data Tables 36, 375) table

300 = forces the use of Langanke & Martinez (2000, Nucl.Phys. A 673, 481) table
301 = forces the use of Oda et al. (1994, Atomic Data and Nuclear Data Tables 56, 231) table

For non-NACRE reactions, the list of available rates may be consulted beforehand at http://www-astro.ulb.ac.be/Netgen/references.html .
No such list is available for NACRE reactions. However, by setting the bibliographic index to 11, the log file will return all rates available before NACRE. In a second step, the bibliographic index may then be set to either 11, 12, or 13... according to the list provided in the log file.

Click on the button 'Add reaction to network'

Note: If this is not the first time Netgen is run from your current IP address, it might be necessary to click first on `Clear network'; otherwise, the selected reaction will be appended to the network generated by the previous Netgen run.

Proceed to step 2b below

Here is a screen copy of the form corresponding to step 2a:

II. Individual reactions

Enter Reaction (Click here for help):

Bibliographic index (1 = default = most recent rate):
+
|
|
V
+

First construct the network by clicking on Add reaction to network,
the button Compute reaction rate will appear in the next form.

2b. Second step: Provide the temperature grid. The network constructed so far appears at the end of the form. It is still possible to add reactions at this step by clicking on Back to network construction.
Click on Compute rates to start the computation of the reaction rates. At this stage, duplicate reactions are removed, and the network is re-ordered in terms of increasing mass number of the first nucleus in the entrance channel. Since this process may take a while, it is possible to provide an e-mail address to be informed when the rates are ready.

It is possible to edit the network at this stage by removing some reactions. Go to the list of reactions at the bottom of the form, and select the reactions to be deleted from the network. Then click on the button Delete selected reactions. The edited network will appear in a similar form, and the editing process may be pursued as many times as required.

Results are described in step 2c.

Here is a screen copy of the form corresponding to step 2b:

Request from: astrohp5.ulb.ac.be (164.15.125.42)

Please send comments and suggestions to ajorisse%astro.ulb.ac.be

List the current network

The Network Generator

Provide temperature grid:
Minimum Temperature (in units of T₈, >0.01):
Maximum Temperature (in units of T₈, <10.0):
Number of grid points (max. 250):
E-mail address to inform when the rates are ready (not mandatory!):

Back to network construction

Current network is:

bib 
code Reaction

2c. Results: Reaction rates:

Three files have been created at the end of the process, and are available at http://www-astro.ulb.ac.be/tmp.
They contain:

the network
the table with the reaction rates
the log file listing the bibliographical references of all the rates available for the reactions included in the considered network, and the rate provided in the table. Possible problems in finding or computing the rate are also reported in this file.

The files are named, respectively:

tmpIP_address.tail
tmpIP_address.rates
tmpIP_address.refs

where IP_address is the IP address of the client, as indicated here. Example: tmp164.15.125.42.rates

What is to be found in the table of reaction rates?

This table provides the number of reactions per sec per (cm³mole^-1)^(N-1), where N refers to the number of particles in the entrance channel:

Multi-particle reactions: Maxwellian-average N_Av^(N-1) < sigma v> [(cm³mole^-1)^(N-1) s^-1]

Radiative neutron capture reactions: Maxwellian-average N_Av < sigma v > [cm³mole^-1 s^-1]

N_Av < sigma v >

is generally derived from the Maxwellian-averaged cross section <sigma v>/v_T using the formula

N_Av < sigma v > = 2.645 10⁴ (kT)^(1/2) <sigma v>/v_T

, with N_Av < sigma v > expressed in cgs units, kT in keV and <sigma v>/v_T in mb

Beta-decays, electron captures, or photodesintegrations: decays per s [lambda (s^-1)]

Some beta-decay rates from Takahashi & Yokoi (1987) consist of four successive columns, corresponding to electronic number densities of 1, 3, 10 and 30 x 10²⁶ cm^-3 A special treatment applies to electron captures by 7Be, as indicated in the corresponding log file

The reaction kind is coded in the header line labelled Type in the following way:

--: two-particle reactions
---: three-particle reactions
----: four-particle reactions
+: photodissociation or beta-decay
++: electron capture
+++: electron capture on Be7
nE+mm: value of the electron number density (in units of electrons/cm³) for beta-decay rates dependent upon electron number density

NaN (`Not a Number`) symbols are given in the table for temperatures at which no data are available
Reverse reaction rates with no data available for the direct reaction are set to NaN or to .1000E-98,
although the exact value may possibly be much larger than .1000E-98 (especially for neutron-capture reactions)!

The energetics (Q = Qrad + Qnu) of the reaction is also provided in the header.
Q is computed from Audi & Wapstra mass table (Audi G., Wapstra A.H., 1995, Nucl. Phys. A595, 409), as the difference between the mass excess in the entrance and exit chanels.
Qrad provides the radiative losses, i.e., Q - Qnu, where Qnu is the energy possibly carried away by neutrinos.
The neutrino loss Qnu is computed according to Eqs. 1 and 2 of Fowler W.A., Caughlan G.R. & Zimmerman B.A. (1975, ARA&A 13, 69).

A fortran routine is available to read the table of reaction rates.

Here is an example of reaction rates from Netgen:

#             1 C  11    
#                 +      
#             1 PROT    
#                 =      
#             0 OOOOO   
#                 +      
#             1 N  12    
#
# Qrad(MeV)       .602    
# Qnu (MeV)       .000    
# Type              --   
#
#       T8
#
      .5000  .4422E-10  
     1.0000  .5789E-07  
     1.5000  .1825E-05  
     2.0000  .1862E-04  
     2.5000  .2045E-03  
     3.0000  .1855E-02  
     3.5000  .1000E-01  
     4.0000  .3552E-01  
     4.5000  .9403E-01  
     5.0000  .2021E+00  
#

Here is an example of the associated log file:


     1   1 C  11 ( 1 PROT , 0 OOOOO)  1 N  12 

 Number of rates available = 3

 #  Date    Reference 
 1       0  WARNING: Not valid above T9 = 1!! Descouvemont P., Baraffe I
            ., 1990, Nucl.Phys. A514, 66                                
 2       0  Wiescher M., Goerres J., Graff S., Buchmann L., Thielemann F
            .K., 1989, ApJ 343, 352                                     
 3       0  CF88                                                        

 Ref. # 2 selected for reaction 1 C  11 ( 1 PROT , 0 OOOOO)  1 N  12 
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