Pavel V. Silin

A Powerful Soft X-ray Source for X-ray Lithography Based on Plasma Focusing

A source of soft X-ray emission (9?14?) based on the miniature 15kJ plasma focus was developed and tested. The X-ray emission was channelled along the chamber axis through an opening in the inner electrode (anode). A regime with a mean output of more than 100 J per discharge was found. At a discharge current of 280kA and repetition rate of 3.5Hz achieved by the device, its lifetime was estimated to be 107 commutations (about a year of continuous operation). A demonstration experiment on irradiation of an X-ray resist is discussed.

Fixation of the stressed state of glass plates by coating them with thin films using a plasma focus installation

Elastic deformation in transparent mediums is usually studied by the photoelasticity method. For opaque mediums the method of film coating and strain gauge method are used. After the external load was removed, the interference pattern corresponding to elastic deformation of the material disappears. It is found that the elastic deformation state of the thin glass plate under the action of concentrated load can be fixed during the deposition of a thin metal film. Deposition of thin copper films was carried out by passing of plasma through the copper tube installed inside the Plasma Focus installation. After removing of the load, interference pattern on the glass plates was observed in the form of Newtons rings and isogers in non-monochromatic light on the CCD scanners which uses uorescent lamps with cold cathode. It is supposed that the copper film fixes the relief of the surface of the glass plate at the time of deformation and saves it when the load is removed. In the case of a concentrated load, this relief has the shape of a thin lens of large radius. For this reason, the interference of coherent light rays in a thin air gap between the glass of the scanners atbed and the lens surface has the shape of Newtons rings. In this case, when scanning the back side of the plate, isogyres are observed. The presented method can be used in the analysis of the mechanical stress in a various optical elements.

Determination of the element distribution in films deposited using the plasma focus facility by Rutherford backscattering

The C, Cu and W element profiles in films deposited using a plasma focus facility are studied by the Rutherford backscattering of 2-MeV He+ ions. The films are deposited onto glass substrates in Ar plasmaforming gas. The element profiles are found to depend significantly on the kinetic energy of particles. The penetration depth of particles with the velocity ~105 m/s is about 1.5 μm. The corresponding element profiles showing the distribution of elements over the thickness of the glass are non-linear. For each element, the maximum layer depth is observed under the glass surface. The formation of Cu, W and C layers under the glass surface and their overlapping is a feature of films deposited using the plasma focus facility. Such an arrangement of layers evidences the significant difference between this method of film deposition and conventional techniques at low rates of atom deposition, as well as diffusion-based methods. The obtained films are found to have dielectric properties.

Measurement of soft X-ray radiation using the PF-4 plasma focus setup with semiconductor X-ray detectors

Soft X-rays were measured with time resolution at angles of 45° and 90° to the system axis in an argon atmosphere using SPPD 11-04 fast semiconductor detectors. The dependence of the X-ray yield was studied as a function of the voltage of a capacitor bank of the plasma focus in a range from 8 to 14 kV and argon pressures from 0.5 to 4 Torr. Generalization of the results obtained allowed possible interpretation of the nature of observed emission.

Integral and temporal characteristics of soft X-rays of the PF-4 plasma focus setup

Soft X-rays of a setup with a power from 1.5 to 5 kJ, operating with argon, were measured using X-ray pinhole cameras and SPPD 11-04 detectors. Integral measurements of X-rays in energy ranges above 1.2, 1.5, 1.8, and 2.5 keV were performed using a 4-frame pinhole camera with hole sizes of ∼250 µm. Simultaneously, the X-ray yield was measured with time resolution in the energy region of > 1.8 keV using a semiconductor detector. X-ray characteristics were experimentally studied at a capacitor bank voltage of 8–14 kV and argon pressures from 1.2 to 3 Torr. The size of hot points was estimated using the pinhole camera with a hole size of ∼20 µm as less than 13–25 µm.

Nonlinear inverse bremsstrahlung and the harmonic generation in a plasma

The phenomena of nonlinear bremsstrahlung absorption and generation of five first odd harmonics are investigated for a plasma photoionized in the Bethe regime of the suppression of the ionization barrier, in which case the velocity distribution of plasma electrons coincides with the distribution of atomic electrons. The partial nonlinear conductivities are obtained. A comparison is made between the features of the absorption and the effectiveness of harmonic generation in two different cases when atomic electrons before ionization are in the ns- or np-states. It was demonstrated that the nonlinear effective collision frequencies (NECF) have unique form in the limit of the high intensity of the pump field. On the other side NECF have the pump field dependencies near their maximum values which are different for the case of s-states and p-states. These dependencies are characterized by especial sealing functions, which give the dependencies on the pump field intensity, the values of the principal quantum number of the pre-excited states of atoms and harmonics numbers.

Powerful pulse x-ray source for high-speed x-ray photography and other applications

Dense Plasma Focus (DPF) of a compact performance is proposed as a powerful X-ray source for various applications. The general property of DPF X-ray pulse is its short duration (t approximately 10 ns). DPF X-ray spectrum reached from zero to a few hundred kilo electron volts. Hard X-ray radiation (E equals 20 ... 100 keV) generated by the DPF device with energy storage about 3 kJ makes it possible to have an X-ray photo of any fast movable object for example rotating car wheel tire. A pulse hard X-ray radiation also can be used in the dynamic flaw detection. The combination of the pulse, energy, and spectral parameters of a DPF hard X-ray radiation allow to consider DPF as a device free from a competition for mentioned applications. A DPF soft X-ray emission (9 ... 14 Angstrom) can be used for X-ray lithography. This DPF application as well as mentioned above are tested experimentally with a success. Besides we have a plan to apply a DPF soft X-ray radiation for the diagnosis of a fast hot dense plasma process by means of radiography of another DPF during its action.