TRANSP

TRANSP[1] is a computational tool developed at the Princeton Plasma Physics Laboratory (PPPL) for the interpretive and predictive modeling of plasma behavior in magnetic confinement fusion experiments. The goal of this research is to develop clean, abundant, and sustainable energy to mitigate rapid climate change, enhance energy security, and provide long-term solutions to global energy needs. TRANSP has been primarily used to analyze data from tokamak experiments and is also applied to other magnetic confinement devices. TRANSP supports studies related to plasma transport, fast ion dynamics, heating, particle fueling, and momentum transport. The web site for TRANSP is https://transp.pppl.gov

TRANSP uses Fortran, C/C++, Java, Python, Perl, Bash, and C shell scripts. It supports OpenMP, Open MPI, and Open ACC. TRANSP is stored on GitHub. TRANSP implements Monte Carlo methods with MPI to calculate with message passing interface (MPI) processing for computing kinetic properties of fast ions, such as neutral beam injected ions and fusion alpha particles. The properties computed include the distributions fast ions energy in space, energy, and the ratio of parallel to the plasma current velocity to perpendicular to the plasma current. It incorporates an electromagnetic wave solver for computing effects of Ion cyclotron resonance heating of the plasma ions and electrons.

TRANSP development started in the late 1970s.[2] It was first used to model plasmas from experiments in the Tokamak Fusion Test Reactor (TFTR) at PPPL.[3] As of 2025, the program has been continuously and extensively developed and maintained at PPPL, with ongoing contributions documented in recent updates and publications. It supports 55 tokamak configura­tions, performing around 10,000 simulations per year to support current and future fusion energy experiments.

TRANSP plays important roles in studies, and is used in many publications related to theory and experiments conducted in tokamaks such as Joint European Torus in the UK; ASDEX Upgrade and TEXTOR Forschungszentrum Jülich in Germany; KSTAR in Korea, EAST Experimental Advanced Superconducting Tokamak and HL-2M in China; Tore Supra WEST (formerly Tore Supra) in France; and in DIII-D DIII-D (tokamak) and NSTX-U National Spherical Torus Experiment in the US.

TRANSP was employed in predictive modeling studies, such as those related to expected fusion reaction rates in TFTR's deuterium-tritium campaigns. An early example is a prediction of fusion reaction rates expected from later experiments in TFTR using deuterium and tritium. TRANSP was the first integrated computer program used for studying phenomena within the plasma boundary of tokamak discharges.[4] It is used to compute properties which cannot be measured directly, such as the radial transport of plasma species, energy, toroidal momentum, and angular momentum. It computes the effects of actuators used to heat and fuel the plasma. The program generates parameters that can be compared with real measurements to verify the accuracy and credibility of the digital model.

Applications in Fusion Research

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TRANSP was used to accurately model a precursor TFTR experiment with deuterium plasma, and then was further used to substitute a mix of deuterium and tritium into the model. The predicted fusion gain, (QDT), defined as the ratio of fusion energy produced to the external heating power applied to the plasma, was 0.32. Later, deuterium-tritium experiments in 1993–1996 achieved a maximum QDT of 0.28[5] indicating that there were foreseen processes besides the straight forward mix of tritium with deuterium.

TRANSP with NUBEAM have been used to provide data for theoretical studies and to benchmark other fast-ion codes. One example of the benchmarking the particle following Monte Carlo code ASCOT and other neutral beam following codes [6]

Publications using TRANSP for JET results include a summary of analysis of modeling of deuterium-tritium experiments in JET[7] and calculations of the fusion gain ratio in the plasma core[8] and simulation of multiple fast ion species[9] studies of optimizing non-thermal fusion power.[10] [11] [12] [13] and [14]

Publications of results from experiments in NSTX-U National Spherical Torus Experiment also rely on TRANSP-generated results. Studies of ways to create reverse magnetic shear are in[15] TRANSP is being used in studies of fast ion transport and Alfvén wave interactions.[16]

TRANSP is being used to predict results from future experiments in ITER. Many examples are discussed in. [17] An early example[18] supports the prediction of achieving QDT in the range 5–14, and a study predicted QDT values in the range 5–14, based on TRANSP modeling under specific assumptions. Other examples include[19] and[20] which projected fusion gains of 3.5-7 in a steady-state mode and 5.6-8.3 in a hybrid mode, depending on the assumptions used for transport and source modeling.

References

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  1. ^ 'The tokamak Monte Carlo fast ion module NUBEAM in the National Transport Code Collaboration library' Alexei Pankin, et al., 2024 Computer Physics Communications 159 (2004) 157–184
  2. ^ Hawryluk, R. J., 1980, in Physics of Plasmas Close to Thermo-nuclear Condition, edited by B. Coppi, G. G. Leotta, D. Pfirsch, R. Pozzoli, and E. Sindoni (Pergoma, New York/CEC, Brussels), Vol. 1, p. 19.
  3. ^ 'Results from deuterium-tritium Tokamak confinement experiments' R.J. Hawryluk, 1998 Reviews of Modern Physics 70 537 https://doi.org/10.1103/RevModPhys.70.537
  4. ^ Hawryluk, R. J., 1980, in Physics of Plasmas Close to Thermo-nuclear Condition, edited by B. Coppi, G. G. Leotta, D. Pfirsch, R. Pozzoli, and E. Sindoni (Pergoma, New York/CEC, Brussels), Vol. 1, p. 19.
  5. ^ R.V Budny; M.G Bell; H Biglari; et al. (March 1992). "Simulations of deuterium-tritium experiments in TFTR". Nuclear Fusion. 32 (3): 429–447. doi:10.1088/0029-5515/32/3/I07. ISSN 0029-5515. Wikidata Q134468646.
  6. ^ 'Modelling neutral beams in fusion devices: Beamlet-based model for fast particle simulations' Asunta O.A., et al. 2015 Comput. Phys. Commun. 188 33 https://doi.org/10.1016/j.cpc.2014.10.024
  7. ^ 'Overview of interpretive modelling of fusion performance in JET DTE2 discharges with TRANSP', Z. Stancar, et al., Nucl. Fusion 63 126058 https://doi.org/10.1088/1741-4326/ad0310
  8. ^ 'Core fusion power gain and alpha heating in JET, TFTR, and ITER' R.V. Budny, J.G. Cordey and TFTR Team and JET Contributors Nuclear Fus. (2016) <56> 056002 https://iopscience.iop.org/article/10.1088/0029-5515/56/5/056002
  9. ^ Podesta M., et al., 2022 'Extension of the energetic particle transport kick model in TRANSP to multiple fast ion species' Nuclear Fusion. 62 (12): 126047 htpps://doi.org/10.1088/1741-4326/ac99ee. ISSN 0029-5515
  10. ^ 'JET D-T scenario with optimized non-thermal fusion' M. Maslov, et al., 2023 Nucl. Fusion 63 112002 https://doi.org/10.1088/1741-4326/ace2d8
  11. ^ 'Local physics basis of confinement degradation in JET ELMy H mode plasmas and implications for tokamak reactors"', R.V. Budny, et al., Nuclear Fus. (2002) <42> 66 https://iopscience.iop.org/article/10.1088/0029-5515/42/1/310
  12. ^ 'Microturbulence and flow shear in high-performance JET ITB plasma' R V Budny, et al, 2002 Plasma Phys. Control. Fusion 44 1215-1228 PII: S0741-3335(02)31531-8
  13. ^ 'Local transport in Joint European Tokamak edge-localized, high- confinement mode plasmas with H, D, DT, and T isotopes' R. V. Budny, et al., 2000 Physics of Plasmas 7 5038 https://doi.org/10.1063/1.1320466
  14. ^ 'Validation of D–T fusion power prediction capability against 2021 JET D-T experiments' Hyun-Tae Kim et al 2023 Nucl. Fusion 63 112004 DOI 10.1088/1741-4326/ace26d
  15. ^ Galante,M.E. et al., 'Reversed magnetic shear scenario development in NSTX-U using TRANSP' Nuclear Fusion 65 026035 https://doi.org/10.1088/1741-4326/ad9e03
  16. ^ Podestà, M, et al., 2009 'Experimental studies on fast-ion transport by Alfven wave avalanches on the National Spherical Torus Experiment' Physics of Plasmas 16, 056104 https://doi.org/10.1063/1.3080724
  17. ^ 'Integrated Operation Scenarios: On the Path to Burning Plasma Operation, Chapter 6' Yong-Su Na, et al., 2025 submitted to Nuclear Fusion (see section 7 Actuators for Integrated Scenario Operation))
  18. ^ R.V.Budny, et al 'Predictions of H-mode performance in ITER' 2008 Nuclear Fusion 48 075005
  19. ^ Murakami M. et al 2011 'Integrated modelling of steady-state scenarios and heating and current drive mixes for ITER' Nuclear Fusion 51 103006 https://iopscience.iop.org/article/10.1088/0029-5515/56/5/056002
  20. ^ Kessel C. et al 2007 'Simulation of the hybrid and steady state advanced operating modes in ITER' Nuclear Fusion 47 1274-1284
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