Update on Mago Progress

The research area known as MAGO (Russian abbreviation for
magnetic implosion
) in Russia and as MTF (Magnetized Target Fusion) in the United States is an alternative to the main CTF approaches (magnetic confinement systems and inertial confinement fusion). The MAGO/MTF approach consists of two phases: 1. First magnetized hot plasma is produced suitable for further compression (with magnetic field ~0.1 MGs having a closed field line configuration; the plasma is of density ~10 cm
^-3
, temperature -300 eV, and small impurity content, as impurities can contribute to the losses caused by radiation). 2. Then the plasma is compressed in the quasi-adiabatic manner by liners (at velocities on the order of 1 cm/μs) using powerful drivers (e. g., explosive magnetic generators, EMG) and its parameters are brought to the ones meeting the Lawson criterion. Here it is necessary to provide the plasma lifetime of ~10
^-5
s. To implement this approach, it is necessary to combine two essential elements: hot magnetized plasma generation system and highly energetic compression system. In the MAGO chambers, DT plasma of the following parameters has been produced in a cylindrical bulk with 5-8 cm height, 6-10 cm outer radius, and 0.9-1.2 cm inner radius: average density 8·0 cm
^-3
, average temperature 200-250 eV , characteristic azimuthal magnetic field in the plasma ~0.15 MG . In the joint VNIIEF/LANL experiment HEL-1 a liner with the parameters (~25 MJ energy, ~0.8 cm/μs velocity) necessary to reach ignition at compression stage was obtained. As ID and 2D computations of pure plasma compression by a liner with the parameters close to those in the experiment HEL-1 show, the plasma with the characteristics corresponding to the Lawson criterion can be produced in this case. However, the data obtained in preliminary heating experiments using X-ray diodes, suggests ~2-3 μs plasma lifetime, which is insufficient to ensure the ignition in compression. Basing on the computed and experimental data one can conclude that the most important mechanism that contributes to MAGO plasma cooling is contamination of the plasma with impurities and it's cooling due to irradiation on impurities. This plasma contamination can result from the plasma mixing with the insulator vapors (which can be produced from
H
-pushed discharge) and wall material washout by the plasma. During the plasma compression in the MAGO chamber the mass washed out from the chamber walls can be even larger than that at the preheating phase. So light materials (carbon, beryllium or lithium for walls, beryllium oxide, boron carbide, boron nitride for insulator) should be used in experiments on DT plasma compression in the MAGO chamber. Using light materials for the chamber walls and insulator can increase the plasma lifetime and make the plasma suitable for the liner-plasma experiments.