The paper presents experimental results from the SMOLA device that is the first facility with a helical mirror section of the magnetic system. This device was built in the Budker Institute of Nuclear Physics for the verification of the helical mirror confinement idea that is the technique of an active control of axial losses from a confinement zone. Theory predicts that, with rotating plasma, a helical mirror will provide suppression of the axial plasma flow and, simultaneously, density pinching to the axis. Experiments demonstrated the increase in plasma density in the entrance trap by a factor of 1.6 in the helical configuration. The integral axial flux from the transport section drops severalfold. The effective mirror ratio of the helical section was $R_{eff} > 10$ . Particle flux returning by the helical mirror section towards the confinement zone was observed. At high corrugation ratios, the axial flux direction is different at the magnetic axis and in the periphery of the plasma in the helical section. All axial fluxes scale linearly with the plasma density, even if the ion mean free path is comparable to the total length of the helical section. Good agreement of the experimental results with theoretical predictions is found.

The paper presents experimental results from the SMOLA device that is the first facility with a helical mirror section of the magnetic field. This device is built in the Budker Institute of Nuclear Physics for the verification of the helical mirror confinement idea that is the recently introduced technique of the active control of axial losses from a confinement zone. Theory predicts that with rotating plasma, a helical mirror will provide suppression of the axial plasma flow and, simultaneously, density pinching to the axis. Experiments demonstrated that plasma density at the exit from the transport section is suppressed with activation of the helical field, the effect is significant and highly reproducible. The most pronounced effect is observed on the plasma periphery, where the mirror ratio is the highest. The integral suppression ratio reaches 2–2.5 in the discussed experiments. Experimental results are compared with simplified theoretical estimates. The integral suppression ratio matches the simple theoretical estimates even if the transversal diffusion is neglected.

The measurements of the plasma velocity in the SMOLA helical mirror by observation of the Doppler shift of the Hα spectral lines emission were done by high spatial resolution spectrometer. A set of experiments was carried out with the different configuration and amplitude of the magnetic field. Potential is driven by plasma gun potentials. The radial distribution of the Doppler shift of the Hα line is used to calculate the velocity of neutral hydrogen, which gives the estimate of the plasma rotation velocity ω ≈ 10 6 s −1 . The indicated velocity corresponds to the presence of the radial electric field E ∼ 70 V/cm. The dependence of the plasma rotation velocity on the radial profile of the electrostatic potential is discussed.

Experimental evidence of the plasma flow suppression by the helical magnetic mirror is presented. Reported experiments were done during the first plasma campaign in the SMOLA helical mirror device at self-consistent floating potentials of all in-vessel electrodes and at minimal magnetic fields suitable for confinement regime. The experimental results are consistent with two main theory predictions for the helical mirror confinement: a reduction of the axial plasma flow and the inward particle pinch. The helical mirror technology can dramatically improve fusion reactor prospects of open magnetic configurations.