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Efficiency and time jitter measurement results are presented for proportional and drift chambers with 2 mm half gap and CF4:iC4H10 (80:20) gas mixture in the presence of magnetic field. Data were taken on the M15 beam line at TRIUMF for positrons with momentum 35 MeV/c. It is demonstrated that two layers of PCs when combined have better than 99.995% efficiency of positron detection in magnetic fields up to 6 T. The time jitter (RMS) of the sum signal from three layers of PCs does not exceed 2.3, 2.9, and 3.9 ns at B = 0, 3, 6 T, respectively. The time shift of this signal does not exceed 2.0, 2.25, and 4.4 ns at B = 0, 3, 6 T respectively for the positron incident angles (with respect to PC plane normal) ranging from 0 to 60°. Such PCs will serve as zero time trigger for PDC chambers with DME gas in TRIUMF experiment 614 [TRIUMF E614 Proposal (1990), Vancouver, B.C., Canada].

We consider an ALT-1,2-like [1,2] system to deliver up to 60-70 MA currents in the liner load and accelerate ∼20 g/cm cylindrical liners to ∼20 km/s (ALT-1,2: ∼31 MA, ∼13 g/cm, ∼12 km/s). The system is intended for the ALT-3 experiment to test the efficiency of magnetic implosion of impacting liners and to verify the possibility of shock-wave measurements at up to 1 TPa pressures.

Good longitudinal symmetry of magnetically driven metal cylindrical liners may be observed at a relatively short time of current rise, for example, in experiments at PEGASUS-2 facility. Because of interaction of the liner with current-conducting edge walls the symmetry of compression may be much worse in experiments with a longer rise time of current delivered by explosive magnetic generators (EMG). The present paper describes the results of study of near-wall effects negative influence on longitudinal symmetry of compression of liners, close in design to experiments at PEGASUS-2 facility, but at an order higher duration of current supplied by helical EMG. The work was conducted within the frames of liner technology program (LT-1 experiments).

Works on the investigation of a magnetized plasma commenced and developed in the framework of MAGO (magnetic compressuring) programme, that got its official status at VNIIEF in 1979. It was directed to the attainment of a thermonuclear ignition in dense targets (without the use of fissionable materials) by means of their compression by liners accelerated to high velocities by a magnetic field. The investigations of the magnetized plasma were focused on the production of a hot ionized low-density plasma pre-heated up to 0.2-1.5 kV and suitable for the subsequent adiabatic pressing by the liner up to thermonuclear temperatures. The development of a new type of plasma chamber has formed the basis for a new area of the works, the calculated and theoretical justification of which has been performed by the theoretical department; the experiments have been arranged and conducted at VNIIEF Electrophysical Department. This chamber has the title 'gaseous ponderomotive unit' (GPU) or gaseous PU, and the system designed for the study of dense targets has come to be known as a liner ponderomotive unit (LPU).

Experiments were conducted on the "CASCADE" electrophysical facility which was used as a source of impulse power for laboratory model of deuterium plasma chamber with a circular MHD nozzle (MAGO chamber). The modes of device's operations were investigated at various values of deuterium pressure in the chamber both with preliminary introduction of magnetic field in the plasma and without it. Depending on conditions of experiment the neutron radiation was generated at the front of increasing current, at its maximum or on a falling down branch of current. Though the experiments were conducted at low energies of plasma chamber powering (100-500 kJ), the stable generation of neutrons was observed. The length of neutron impulse achieved the value comparable to length of neutron radiation being obtained in experiments, in which explosive magnetic generators of multimegajoule energy scale are used (/spl sim/1 /spl mu/sec and more). It was defined the optimal deuterium pressure in the plasma chamber for the used operation modes of the device.

Helical explosive magnetic generators (HEMG) represent the inductive generators of electromagnetic energy. Operation of HEMG is based on compression of magnetic field, preliminary delivered to the helical coil, by the metal armature, placed coaxially in the coil center and expanding during an explosion. Circuit compression results in a decrease of its inductance, while the magnetic energy and the current increase. Current in HEMG reaches a magnitude of several dozen million amperes. When using HEMG, the designers, as a rule, try to get the maximum energy the generator is designed for. It means that usually explosive magnetic generators operate under limiting conditions. The objective of this work is to reduce the risk during explosive experiments by obtaining the possibility to develop new, and to use the available, HEMGs with guaranteed margins for the critical parameters.