Quadrupole lenses on the basis of permanent magnets for a PRIOR proton microscope prototype

Four quadrupole lenses based on permanent magnets of the NdFeB material (PMQ) were developed for the imaging section for forming images of the ion-optical system of the PRIOR proton microscope prototype: the effective length of two of them is 144 mm, and the other two are 288 mm long. The field induction at the radius of the lens aperture is 1.77 Т, and the aperture is 30 mm in size. The modular design of the PMQ makes it possible to vary the length of the lenses, compensate for the offset of the magnetic axis from the ion optical axis of the microscope channel, and decrease the variation of the angular position of the magnetic medians. The PMQ magnetic field was adjusted, scanned, and its main characteristics were determined. The 3D mathematical models of the magnetic-field distribution that are obtained as a result of PMQ measurements are intended for the use in calculations of the beam dynamics during adjustment of the ion-optical system of the proton microscope and for attaining the highest spatial resolution. The developed lenses were used in the first experiments on the PRIOR facility.     

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.

     

A method for measuring spectral and time characteristics of mixed pulsed gamma-neutron fields with scintillation and Cherenkov detectors with nanosecond time resolution

A method for measuring spectral and time characteristics of pulsed mixed (n, γ) fields is described. The essence of this method is that a sequence of signals from individual (n, γ) particles registered by (n, γ) detectors is written in a computer with the subsequent amplitude-time analysis of the signal parameters. Fast scintillation and Cherenkov detectors with FWHM of pulses of ～1.5 and 2.5 ns, respectively, are used as (n, γ) detectors. A TDS-3054 broadband digital oscilloscope records signals and transmits them to the computer through a GPIB-USB interface. The equipment used ensures efficient detection of (n, γ) particles at detector counting rates of up to ～2 × 10⁸ pulses/s. The efficiency of this method has been tested in measurements of characteristics of (n, γ) radiation fields from an ИНГ-031 pulsed neutron generator and from a copper target irradiated with a beam of carbon nuclei with an energy of 200 MeV/amu from the TVN-ITEF acceleration-storage complex.     

Calculation and Analysis of Unsteady-State Flow of Gas past a Deformable Plane Lattice

A numerical code is developed for solving the problem on unsteady-state flow of a gas past a multiply connected region, the position of whose boundaries depends on the force effect of the flow. Calculations of unsteady-state wave flows are performed using the example of a model of rupture in the process tube of a boiling graphite–water reactor (RBMK—high-power channel reactor). It is found that, in the case of rupture, a leak may arise in its neighborhood, exhibiting an unsteady-state wavelike behavior with pulsations of the flow rate and pressure.     

Grazing incidence extreme ultraviolet spectrometer fielded with time resolution in a hostile z-pinch environment

This recently developed diagnostic was designed to allow for time-gated spectroscopic study of the EUV radiation (4 nm < λ < 15 nm) present during harsh wire array z-pinch implosions. The spectrometer utilizes a 25 μm slit, an array of 3 spherical blazed gratings at grazing incidence, and a microchannel plate (MCP) detector placed in an off-Rowland position. Each grating is positioned such that its diffracted radiation is cast over two of the six total independently timed frames of the MCP. The off-Rowland configuration allows for a much greater spectral density on the imaging plate but only focuses at one wavelength per grating. The focal wavelengths are chosen for their diagnostic significance. Testing was conducted at the Zebra pulsed-power generator (1 MA, 100 ns risetime) at the University of Nevada, Reno on a series of wire array z-pinch loads. Within this harsh z-pinch environment, radiation yields routinely exceed 20 kJ in the EUV and soft x-ray. There are also strong mechanical shocks, high velocity debris, sudden vacuum changes during operation, energic ion beams, and hard x-ray radiation in excess of 50 keV. The spectra obtained from the precursor plasma of an Al double planar wire array contained lines of Al IX and AlX ions indicating a temperature near 60 eV during precursor formation. Detailed results will be presented showing the fielding specifications and the techniques used to extract important plasma parameters using this spectrometer.     

Laser optoacoustic method for measuring thermal characteristics of condensed substances under the action of an intense heavy-ion beam

The results of the development of a contactless remote technique for studying thermal characteristics of condensed matter under a pulsed action of an intense heavy-ion beam are presented. This technique is based on measuring the velocity of sound from the time of passage of a probing optoacoustic pulse in a target exposed to an ion beam. To record an acoustic response, we have developed a schlieren system based on the shadow technique for visualizing optical phase nonuniformities. The efficiency of this technique was checked in test experiments on the TWAC-ITEP facility.     

X-ray spectroscopy of Cu impurities on NSTX and comparison with Z-pinch plasmas

X-ray spectroscopy of mid-Z metal impurities is important in the study of tokamak plasmas and may reveal potential problems if their contribution to the radiated power becomes substantial. The analysis of the data from a high-resolution x-ray and extreme ultraviolet grating spectrometer, XEUS, installed on NSTX, was performed focused on a detailed study of x-ray spectra in the range 7-18 A?. These spectra include not only commonly seen iron spectra but also copper spectra not yet employed as an NSTX plasma impurity diagnostic. In particular, the L-shell Cu spectra were modeled and predictions were made for identifying contributions from various Cu ions in different spectral bands. Also, similar spectra, but from much denser Cu plasmas produced on the UNR Z-pinch facility and collected using the convex-crystal spectrometer, were analyzed and compared with NSTX results.     

Nonperturbing gas diagnostics of ion beams

The usability of the gas scintillation method in almost nonperturbing diagnostics of ion beams was investigated. The width of the beam was measured on the ITEP-TWAC setup by its image in argon atmosphere at different gas pressures and beam intensities. The dependences of the luminescence intensity of argon atoms on the number of ions in a pulse and the gas pressure in the diagnostic chamber were obtained.     

An integrated automation system for experiments on the fast extraction beamline of the TWAC-ITEP accelerator-accumulator facility

The integrated automation system (IAS) for proton radiography and ion radiobiological experiments on the fast extraction beamline of the TWAC-ITEP accelerator-accumulator facility has been developed and successfully used. The subsystems that are parts of the IAS perform the following functions: acquisition, storage, and processing of experimental data; control of the magnetic lenses of the charged-particle beam transport line; beam diagnostics; and radiation safety and monitoring. The subsystems are composed of hardware-software modules, each dealing with a particular measuring or actuating device and a program for readout, storing, and processing of experimental data corresponding to this device. The modules communicate via a TCP/IP socket in a configuration dependent on the requirements of a particular experiment. Data are transmitted from one module to the other in the real time mode within the closed ring network, which allows consecutive processing of incoming experimental data. The status of the system elements, incoming experimental data, and results of their rapid analysis are displayed in the real time mode on the web server. Owing to the flexible structure of the integrated automation system, it is possible to promptly create new configurations for acquisition and processing of experimental data.     

Determination of the characteristic velocities of a set of hydrodynamic equations for bubble flow

Analysis is made of the effect of the form of pulsation terms in a set of averaged hydrodynamic equations for bubble flow with incompressible phases on the wave properties of the model. Relations are derived which define the roots of characteristic equation of the set.