TRANSP can follow the fusion products using the NUBEAM MonteCarlo.

- NPTCLF
- Number of particles to be tracked in the MonteCarlo code. The default is 1000
- NLFST
- Set equal to
**TRUE**to calculate products from D(D,T)p reactions [Eq.1]. - NLFSP
- Set equal to
**TRUE**to follow protons from D(D,T)p reactions [Eq.1]. - NLFHE3
- Set equal to
**TRUE**to calculate products from D(D,He3)n reactions [Eq.2]. - NLFHE4
- Set equal to
**TRUE**to calculate alpha products from D(T,He4)n reactions {Eq.3}. - NLFATOM
- Set equal to
**TRUE**to compute atomic physics effects on fusion products fast ions slowing down.

The T(T,He4)2n reactions [Eq.4], as a by-product of D(D,T)p reactions, are also calculated in TRANSP.

### New fitting for T-T reactivities

With version 18.2 new fittings over DPC have been implemented for T(T,2n)4He fusion reactions, based on the work by David Coster [IPP, Garching].

The input data are available on the SVN repository

https://gforge6.eufus.eu/svn/amnsproto/curation/nuclear [password-protected page]. Please check for Revision 642.

Set:

- LEV_TTNUK = 1
- To use the new fittings by David Coster. The figure below shows a comparison between the old fitting in TRANSP and the new fit by D. Coster.

## Power threshold

It is possible to set a power threshold above which the number of particles **NPTCLF** in the MonteCarlo calculations is maintained. If the actual source power is lower than the set power threshold, then a population of f*NPTCLF MonteCarlo particles is maintained, where f=[actual source power]/threshold power. The default values for the various fusion reactions are as follow:

- PLFST [=100.0 W]
- power threshold for D(D,T)p reactions
- PLFSP [=100.0 W]
- power threshold for D(D,T)p reactions
- PLFHE3 [=100.0 W]
- power threshold for D(D,He3)n reactions
- PLFHE4 [=10.0 kW]
- power threshold for D(T,He4)n reactions

## Model Options for alphas

- NALPHA=0
- This is the default value, to calculate the alphas from the MonteCarlo model.
- NALPHA=1
- Fast, non-Monte Carlo model by D. Mikkelsen. This model has no orbit effects and assumes instant equilibration of the alpha slowing down distribution on the background plasma.

## Renormalisation

It is possible to use 1D input Ufile data for the total production rates of the various fast ion populations as a function of time to renormalise the profiles determined from simulation. This is done using the following switches:

- NLUSFA
- Set this flag to
`TRUE`

to read in He^{4}data from UFILES`PRESFA/EXTSFA`

. - NLUSF3
- Set this flag to
`TRUE`

to read in He^{3}data from UFILES`PRESF3/EXTSF3`

. - NLUSFT
- Set this flag to
`TRUE`

to read in He^{3}data from UFILES`PRESFT/EXTSFT`

. - NLUSFP
- Set this flag to
`TRUE`

to read in He^{3}data from UFILES`PRESFP/EXTSFP`

.