A digital model of a grazing-incidence X-ray spectrograph and methods for reconstruction of soft X-ray spectra of a Z-pinch plasma at the Angara-5-1 facility in the 2–40 nm range have been developed. The main problems hindering reliable qualitative and quantitative reconstruction of the initial Z-pinch X-ray spectra are the superposition of signals from different diffraction orders and the complex form of the device instrumental function. Two techniques for reconstructing the spectrum are presented. In the first one, a digital model of the spectrograph was developed in the Geant4 Monte Carlo simulation toolkit, taking into account the geometry of the experiment and the processes of interaction of X-ray radiation with a diffraction grating. In this model, taking into account the specific shape of the groove profile of the diffraction grating and the differential method for solving the diffraction problem, the X-ray intensity distribution in different diffraction orders depending on the wavelength is calculated. Using the developed model of the spectrograph, its instrumental function was calculated. The second technique does not use a specific grating groove shape, but, based on the analysis of calibration spectrograms, it constructs a dispersion relation and allows one to reconstruct the spectrum. At the end of the work, the results of reconstruction by the first and second techniques are compared and fairly good agreement between the spectra obtained by different techniques is shown.

Описана экспериментальная установка, созданная на базе ускорительного комплекса ТВН–ИТЭФ для проведения радиобиологических исследований на пучках тяжелых ионов. C использованием магнитных элементов линии транспортировки и системы коллиматоров отлажена методика формирования параллельного пучка с требуемыми поперечными размерами. В рамках проводимых исследований разработана и реализована система дозиметрии, позволяющая проводить измерения пространственного распределения поглощенной дозы в веществе при воздействии импульсных пучков тяжелых ионов. С использованием данной системы исследовано распределение поглощенной дозы в воде для моноэнергетического пучка ионов углерода с начальной энергией 215 МэВ/а.е.м. На основании полученной информации проведена оценка поглощенной дозы в тонком слое воды для заданной глубины и интенсивности пучка. Использование данной методики обеспечивает точность определения поглощенной дозы не хуже 5%.

An experimental setup based on the TWACITEP accelerating complex for performing radiobio� logical studies on heavy ion beams is described. Using magnetic elements of transportation lines and collima� tor systems, the procedure for forming a parallel beam with required transverse sizes is adjusted. A dosimetric system intended to measure spatial distributions of absorbed doses in a substance exposed to pulsed beams of heavy ions has been designed and implemented in the performed studies. Using this system, the distribution of the absorbed dose in water was studied for a monoenergetic beam of carbon ions with an initial energy of 215 MeV/amu. Based on this information, the absorbed dose was estimated in a thin water layer for the given depth and beam intensity. The use of this procedure ensures the accuracy in determining the absorbed dose of no worse than 5%.

An experimental setup based on the TWAC-ITEP accelerating complex for performing radiobiological studies on heavy ion beams is described. Using magnetic elements of transportation lines and collimator systems, the procedure for forming a parallel beam with required transverse sizes is adjusted. A dosimetric system intended to measure spatial distributions of absorbed doses in a substance exposed to pulsed beams of heavy ions has been designed and implemented in the performed studies. Using this system, the distribution of the absorbed dose in water was studied for a monoenergetic beam of carbon ions with an initial energy of 215 MeV/amu. Based on this information, the absorbed dose was estimated in a thin water layer for the given depth and beam intensity. The use of this procedure ensures the accuracy in determining the absorbed dose of no worse than 5%.

Laser interferometry methods were used to measure the density of free electrons and degree of plasma ionization in a hydrogen target intended for experiments on determining energy losses of heavy ion beams in an ionized matter. It is shown that the linear electron density can be varied in the range from 3.3 × 10 17 to 1.3 × 10 18 cm −2 by varying the initial plasma parameters (the hydrogen pressure in the target and the discharge current). The error in measuring the linear electron density in the entire range of the varied plasma parameters was less than 1%. The maximum degree of plasma ionization achieved at the initial gas pressure of 1 mbar was 0.62 ± 0.05.

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.

Описан метод измерения спектральных и временных характеристик импульсных смешанных (n, )-полей. Суть метода – последовательность сигналов c (n, )-детекторов от отдельных (n, )-частиц записывается в компьютер с последующим амплитудно-временным анализом параметров сигналов. В качестве (n, )-детекторов используются быстрые сцинтилляционные и черенковские детекторы с полушириной импульсов 1.5 нс и 2.5 нс соответственно. Запись и передача сигналов в компьютер осуществляются с помощью широкополосного цифрового осциллографа TDS-3054 через интерфейс GPIB-USB. Используемая аппаратура обеспечивает эффективную регистрацию (n, )-частиц при загрузках детекторов до 2 · 108 импульсов/c. Эффективность метода апробирована при измерениях характеристик полей (n, )-излучения от импульсного нейтронного генератора ИНГ-031 и из медной мишени, облучаемой пучком ядер углерода с энергией 200 МэВ/а.е.м. ускорительно-накопительного комплекса ТВН-ИТЭФ.

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 × 10 8 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.

A digital method for pulse-shape discrimination between neutrons and γ rays was used in measurements at counting rates of up to ∼106 counts/s in the energy range of ∼2–800 keV. Pulses produced by neutrons and γ rays in a stilbene-based scintillation detector were digitized by a digital oscilloscope and transmitted to a computer for carrying out particle identification. Identification was performed for radiation of radionuclide sources and a pulsed neutron generator operating in a repeated triggering mode. Amplitude spectra of pulses identified as neutrons and γ rays of radiation from the generator were measured. At a detector counting rate of ∼8.5 × 105 counts/s, ∼90% of all recorded pulses were recognized as neutrons. In the energy range of ∼30–800 keV, the γ-ray suppression factor was ∼104–103 at counting rates of ∼1.5×105–5 × 105 counts/s, while the efficiency of identifying neutrons was >0.9. The suppression factor for γ rays with an energy of ∼10 keV was ∼300, and the neutron identification efficiency was ∼0.75.

Experimental data are presented concerning the generation and investigation of multiply charged Ti ions from the plasma produced by the second harmonic radiation of a neodymium laser (with an energy under 14 J and a pulse duration of 2.5 ns). A group of ions with multiplicities ranging from +16 to +20 was recorded with an electrostatic energy mass analyser and a collector was employed to measure the ion current of this group, which was found to be equal to ∼1 mA cm-2 for an ion pulse duration of ∼0.8 μs.

The sputtering coefficient of gold was determined experimentally as a function of the incident krypton ion energy in the inelastic region of energy loss. It is shown that this dependence does not differ from that predicted by the cascade theory. The work was carried out using the U-400 cyclotron beam at the Joint Institute for Nuclear Research, Dubna.