S. A. Kolesnikov

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.

Effect of the Initial Density on the Structure of Detonation Waves in Heterogeneous Explosives

Reaction zones in steady detonation waves in RDX, HMX, TNEB, and ZOX with different initial densities are studied with the use of a VISAR interferometer. The critical initial density which causes the qualitative change in the reaction-zone structure is determined: below the critical density, a chemical spike is registered, whereas above this density, the chemical spike disappears and an increase in pressure is observed. It is shown that the critical density for a given dispersion of high explosives depends on the method of charge pressing and equals 1.73, 1.84, 1.56, and 1.71 g/cm3 for RDX, HMX, TNETB, and ZOX, respectively. It is concluded that the unusual structure of the detonation wave is caused by the reaction of the high explosive directly in the shock-wave front. Key words: high explosives (HE), HE density, structure of detonation waves.

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.

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.

Reaction Zone of Steady‐State Detonation Waves in Dinitrodiazapentane and RDX

The detonation waves structure of pressed high explosives (HE) dinitrodiazapentane (DNP) and RDX with different initial densities was investigated by the laser interferometric system VISAR. The experimental results are the profiles of surface velocity of foils placed at the boundary between a HE sample and a water “window”. In DNP the Von Neumann spike was observed for all studied initial densities, and one of the most interesting features in these results is the unexpectedly large ratio (reaching two) of the von Neumann peak to C‐J point parameters. Earlier it was found that in RDX with initial particle size of ∼80 μm existed the critical initial density of 1.73 g/cm3 above which the monotone increase of parameters in the reaction zone was observed. Now it is shown that in acetone‐recrystallized RDX with initial particle size of ∼5 μm this critical density is much lower (∼1.30–1.35 g/cm3). Above this density the Von Neumann spike was observed. The experimental results are explained by chemical reaction i...

ITEP proton microscopy facility

The proton radiography facility which uses magnetic optics (proton microscope PUMA [7]) was developed at TWAC-ITEP accelerator [1,2,6]. PUMA proton microscopy facility was specially designed for studies in the field of high energy density physics, including the research of equations of state and phase transitions of matter at extreme conditions, shockwave and detonation physics, hydrodynamics of high energy density flows, and dynamic material strength and damage studies [10,11]. Proton microscope PUMA allows the measurement of density distribution within static and dynamic objects by using a proton beam with energy of 800MeV. Proton-radiographic image of the object is formed in the plane of the detector with magnification k=4. An image of the object is formed using a magneto-optical system consisting of four quadrupole lenses on permanent magnets (PMQ). PUMA facility is designed for the measurement of objects with areal density of 20 g/cm2 and field of view of 20 mm. For the facility, the spatial resolution is from 60 microns to 115 microns for objects with areal density from 0.46 g/cm2 to 17 g/cm2, respectively. Research was also performed on nondestructive testing of static objects (including tomographic methods) and radiobiological studies.

Application of interference-polarization filters for the optical absorption method of gas analysis

A number of B.N. Grechushnikov’s works were devoted to the application of interference-polarization filters as a two-beam interferometer for Fourier-spectroscopy. In this paper the potential of these filters for the optical absorption method of gas analysis (specifically, the selective measurement of components with overlapping absorption spectra) is considered.

Selectivity of the optical-absorption method based on an instrumental pick out of Fourier components in the absorption spectrum

The introduction of interference–polarization filters (IPFs) in the structure of an optical–absorption analyzer makes it possible to pick out a harmonic (a Fourier component of the absorption spectrum) providing measurement with the highest sensitivity. The selectivity of such a method of analysis is determined by overlapping the oscillations of the measured and interfering components. By the example of measurement in benzene in the presence of an interfering component (toluene), the possibility is considered for the optimization of selectivity due to the variation of the path-difference dispersion for ordinary and extraordinary interfering rays. The metrological characteristics of the interference–polarization analyzer of C6H6 confirming the results of calculations are given.

Sensitivity of the optical absorption method based on instrumental selection of Fourier components of the absorption spectrum

A new analytical method of optical absorption analysis, based on selection of a Fourier component of the absorption spectrum (characteristic of the material under study) by a polarization interference filter, has been proposed and tested experimentally.