S. V. Dudin

Diagnostics of fast processes by charged particle beams at TWAC-ITEP accelerator-accumulator facility

A new setup for the experimental investigation of rapid dynamic processes using proton radiography techniques has been created at the TWAC-ITEP terawatt accelerator-accumulator facility. A set of equipment for conducting shock-wave experiments has been designed, constructed, and tested, and an instrumentation-software complex has been developed for the automation of experiments. The first series of experiments with dynamic targets representing high explosives have been carried out, in which the density distribution in detonation waves initiated in these explosives has been measured.

Measurements of the electron concentration and conductivity of a partially ionized inert gas plasma

The results are presented of experiments performed to measure the electron concentration and conductivity of a partially ionized inert gas plasma in a magnetic field. The plasma was generated behind the front of incident and reflected shock waves excited by explosively driven linear generators. A magnetic field of about 5 T was formed inside a solenoid wound on the generator channel. Measurements were taken at P=30−650 MPa, T=6000−17000 K, and a Coulomb nonideality parameter of 0.01–2.8. Electron concentrations calculated from measured Hall voltages reached 1.6×1021 cm−3. The recorded conductivities were in the range 0.1–200 Ω −1 cm−1. The experimental results were compared with various models of the thermodynamic and transport properties of a nonideal plasma.

Shockwave-driven, non-ideal plasmas for interaction experiments with heavy-ion beams

Plasma targets for measuring energy loss and charge-state distribution of heavy ions in non-ideal plasmas have been developed. Ar plasmas with Γ-parameters 0.55–1.5 could be realized and the interaction with several ion species studied. Here, the results for 5.9 MeV/u C ions are presented. The energy loss in plasma was reproduced in different experiments.

Application of charged particle beams of TWAC-ITEP accelerator for diagnostics of high dynamic pressure processes

The 800 MeV proton radiography facility for high dynamic pressure research in condensed matter has been commissioned at the Terrawatt Accelerator of Institute of Theoretical and Experimental Physics (TWAC-ITEP) in Moscow. Spatial resolution of the facility measured in static experiments with a variety of test objects was found to be 0.30±0.01 mm in current experimental arrangement. First dynamic experiments on the observation of a shock loading of steel surface and a propagation of the detonation wave in a high explosive charge were conducted. Good quantitative agreement of density profiles reconstructed from obtained radiographic images with theoretical and simulated data showed the capabilities of high energy ion beam radiography as an excellent tool for bulk density measurements in high dynamic pressure studies.

Hall Effect in Nonideal Argon and Xenon Plasmas

The Hall constant and conductivity of nonideal partially ionized argon and xenon plasmas are measured by the probe methods. Plasmas were generated behind the front of powerful shock waves using linear explosive generators. The results are compared with some plasma models.

TWAC-ITEP proton microscopy facility

A proton radiography facility with the use of magnetic optics (PUMA proton microscope) has been developed at the TWAC-ITEP accelerator-accumulator facility (the ITEP terawatt accumulator) for measuring the substance density distribution inside static and dynamic objects using the proton beam with an energy of 800 MeV. The proton radiographic image of an object of investigation placed in the object plane of the setup is formed in the plane of the detector with magnification K = 4 with the aid of the magneto-optical system consisting of four quadrupole lenses on permanent magnets. The PUMA facility is intended for measuring objects with an areal density of up to 20 g/cm2 with a field of vision as large as 20 mm in diameter. The spatial resolution of radiographic images depends strongly on the areal density of the object of investigation. For the PUMA facility, the spatial resolution varies from 60 to 115 μm at an areal density of 0.46–17 g/cm2, respectively. The dynamical state of substance can be investigated in four consecutive radiographic images, since the time structure of the proton beam consists of four pulses, each with a duration of 47 ns (full width at half maximum (FWHM)) and an interval of 250 ns between them. This article is devoted to the description of the proton microscope construction. The main metrological characteristics of the facility are described using experiments with static and dynamic objects as an example.

Laser interferometer for measuring the mass velocity of condensed substances in shock-wave experiments on the TWAC-ITEP proton-radiographic facility

The results of development of a laser interferometer designed for measuring the mass velocity of condensed substances in shock-wave experiments in the field of high-energy-density physics are presented. The interferometer is incorporated in the measuring complex of the TWAC-ITEP proton-radiographic facility. The developed laser system allows measurements of the velocity of free surfaces of samples in shock-wave experiments with an error no worse than 10 m/s for the entire range of velocities attained experimentally. The time resolution of measurements is limited by the response speed of the used PMTs and amounts to 2.5 ns. Combined investigations of shock-wave loading of metal targets and scabbing-fracture and jet-formation processes on free metal surfaces were performed by the proton-radiography and laser-interferometry methods.

Measurement of the temperature of the copper plasma generated in the process of release of a shock-compressed target

The processes associated with the arrival of a strong shock wave at the surface of a metal have been considered. It has been experimentally revealed that the withdrawal of the wave from a shock-loaded sample under release is accompanied by the formation of not only a dusty flow, but also a metal plasma. The temperature of the plasma component, which is about 1 eV, has been determined from the relation of the line intensities using the spectral diagnostics of the plasma.

Measurements of static electrical conductivity of a dense plasma in a magnetic field

New experimental setup for generation of a non-ideal plasma, placed in a magnetic field of up to 25 T, is presented. The plasma generation technique is based on gas compression and heating behind the front of a shock wave with the use of an explosively driven linear generator. The magnetic field is produced by a discharge of a capacitor through a solenoid reeled on the generator channel. DC electrical conductivity of the plasma is determined by two and four contact techniques. Possibilities of magnetized dense plasma generation are discussed.