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Hydrogen Isotope Composition in Hot Plasmas


Apparatus for Measurements of the Hydrogen Isotope Composition (Hydrogen, Deuterium and Tritium) and the Studies of Isotope Effects in Hot Plasmas

Tech Area / Field

  • FUS-PLA/Plasma Physics/Fusion
  • INS-MEA/Measuring Instruments/Instrumentation

8 Project completed

Registration date

Completion date

Senior Project Manager
Pradas-Poveda J I

Leading Institute
Russian Academy of Sciences / Physical Technical Institute, Russia, St Petersburg

Supporting institutes

  • VNIIEF, Russia, N. Novgorod reg., Sarov


  • EURATOM-Ciemat, Spain, Madrid\nUKAEA, UK, Abingdon

Project summary

One of the main goals of fusion plasma diagnostic is the measurement of isotope H/D/T composition of the plasma. There are at least two objects of these measurements. One is the control of D/T fuel composition of burning plasmas to get the optimal regime of ignition and fusion burning. Deuterium and tritium are main fuel components in burning plasma. It is necessary to have the optimal D/T density ratio for achieving the most effective fusion reactor regime. The absence of this condition leads to decreasing of fusion reactor efficiency and this in turn makes the electricity production in the reactor more expensive. From this point of view the D/T ratio inside the plasma is one of the most important parameters to be measured and controlled in any fusion reactor.

Another objective is the study of energy confinement scaling in the plasmas having different hydrogen isotope compositions (H/D/T). Transport analysis performed on large plasma machines like JET (UK) and TFTR (USA) shows that plasma confinement depends on the isotope composition. These problems require the use of the diagnostics able to measure H/D/T ion density ratio inside the plasma in wide range of the ratio values.

At the moment only diagnostic which can do it is the analysis of neutral H, D and T atom fluxes emitted by the plasma. The ratio of the atom fluxes is directly connected with the ratio of proton/deuteron/triton densities. The detection of the atoms with the energies E>100 keV (~5 kTi) allows to measure H/D/T composition in the plasma core for reactor like plasma machines.

In addition the isotope ratio may be changed over the plasma cross-section due to influence of fueling plasma by pellets, neutral beam injection and different transport processes for different hydrogen isotopes. Therefore the control of isotope composition distribution over the plasma cross-section is also important.

For the isotope ratio measurements it is necessary to develop Neutral Particle Analyzers (NPAs) with high rate of H/D/T mass separation (with mass rejection<10-2), high detection efficiency in the energy range 100-300 keV (50-100%) and with low sensitivity for neutron and gamma radiation (<10-6-10-7). It is also important to develop the NPAs with many observation lines able to measure simultaneously the distribution of atomic fluxes of different masses over the plasma volume.

For this purpose it is necessary to perform following studies with the use of numerical simulation and experiments with atomic hydrogen and deuterium beams:

– the numerical modeling of neutral atom fluxes emitted from the plasma and of their source functions inside the plasma. This will give the possibility to estimate NPA count rates vs atoms energy;

– the studies of the main processes in the NPA elements (stripping in the foil and accompanying scattering, acceleration and focusing after stripping), the studies of new detectors (SCD and fast scintillators, allowing to perform spectrometric energy analysis in each NPA channel with high count rate) and their sensitivity to neutron and gamma radiation;
– the developing of the NPA dispersion system allowing to detect simultaneously the atomic fluxes along several observation lines with energy and mass analysis in each observation line.

On the basis of that studies in will be possible to create new NPA – Isotope Separator which will be able to provide the distribution of isotope composition over DT plasma cross section.

A.F. Ioffe Institute traditionally has a very good skill in the field of development of the NPAs of different models. As a result of this project the Ion Separator NPAs with one/several observation lines will be developed. Those NPAs can be used on plasma machines JET (Euratom-UK), JT-60U (Japan) and can be a prototype for future plasma machines with plasma ignition.

Total amount of the weapon scientists taking part in this project is seven.

Duration of the project is 3 years.


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