Axially Symmetric Magnetic Mirror Traps: Status and Prospects

Flute mode fluctuations in the divertor mirror cell

“…Applying the stability criterion to the outermost magnetic flux tube r = a with the con-servation of magnetic flux inside the outermost magnetic flux tube, the stability criterion for GDT 15 The idea of the gas dynamic trap ͑GDT͒ makes use of the good curvature region just outside the outermost mirror throat of the mirror machine where the large plasma loss flux exists, and it can contribute to the MHD stability in a high density operation. It has been reported in the GDT experiment 16,17 that the plasma was sustained stably. The similar approach to the axisymmetric mirror is proposed by Post,18 where the peaked plasma density in the good curvature region outside the outermost mirror throat is produced by the ion beam injection from the end-wall direction, which stabilizes the confined plasma by its presence.…”

Modern magnetic mirrors and their fusion prospects

“…Plasma expansion along the mirror cells excited an instability, which resulted in an effective exchange between the passing and trapped ions in the cells. Therefore, an effective mean free path of ion scattering appears to be about a length of the cell even for rather small plasma densities in the range 10 21 -10 22 m −3 , which corresponds to the longest time of plasma axial confinement (figure 11) [17]. As is always true, MHD stability is absolutely necessary to achieve high plasma performance.…”

“…In the multi-mirror GOL-3 device [17,20], plasma is confined in a 12 m long solenoid composed of mirror cells connected to each other. The magnetic field changes from 4.8 T at the mirrors down to 3.2 T at the mid-plane of the individual mirror cells with a spatial period of 22 cm.…”

“…The safety factor for linear systems, as the GOL-3 device is, can be written as q = (H z /H ϕ ) • (2π r/L), where H z and H ϕ are the longitudinal and azimuthal components of the magnetic field, and r and L are the plasma radius and the column length. The results of measurement of µ = 1/q are given in figure 12 [17,25] in the stable operation regime of GOL-3. This regime is characterized by the occurrence of a sheared helical magnetic field and the formation of a magnetic surface with an azimuthal field equal to zero inside the plasma column.…”

Start of experiments in the design configuration of the GOL-NB multiple-mirror trap

“…The GOL-NB device is the successor of the highly productive GOL-3 multiple-mirror experiment in the Budker Institute of Nuclear Physics, which demonstrated the expected confinement improvement of turbulent plasma [20]. The GOL-3 device was a 'brute force' experiment where plasma of n e ∼ 10 21 m −3 was collectively heated up to several keV with a high-power relativistic electron beam (∼1 MeV, ∼30 kA, ∼10 μs).…”