ABSTRACT
The article is devoted to the development of an EUV microscope using a wavelength of 13.84â nm. Due to the use of a mirror lens with a large numerical aperture, NA = 0.27, and a short depth of focus, it has been possible to carry out z-tomography of bio-samples for the first time with this type of microscope. A 3D image was reconstructed, and a pixel resolution of 140â nm was obtained. A new simple algorithm for the 3D reconstruction of absorption images from z-tomography data has been proposed that takes into account lens aberrations and a point spread function. The algorithm reduces the inverse absorption task to the corresponding well-studied task of fluorescence microscopy, with an error of 10% for cells up to 10 µm thick.
ABSTRACT
A high-resolution laboratory reflectometer designed for operation in the soft x-ray (SXR) and extreme ultraviolet (EUV) ranges is described. High spectral resolution, up to 0.028 nm, in a wide spectral range is achieved due to the Czerny-Turner monochromator. A laser plasma generated by irradiating a solid-state target with a focused laser beam (wavelength 1.06 µm, pulse energy 0.5 J, duration 4 ns, and pulse repetition rate 10 Hz) is used as a source of SXR and EUV radiation. The goniometer allows the study of curved optical elements with an aperture up to NA = 0.5 and a diameter of up to 500 mm. The methods providing high efficiency of the optical system and spectral resolution in a wide range of wavelengths are described in detail. The problem of taking into account high orders in the recorded spectra of a laser plasma is discussed. A comparison of the measurement results with the described reflectometer and the optics beamline at the BESSY-II synchrotron is given.
ABSTRACT
Aluminum thin-film spectral filters are widely used in telescopes for space observations of the Sun in the extreme ultraviolet range of wavelengths. The main purpose of film filters is to block radiation in the UV, visible, and near-IR spectral ranges. In connection with the development of new projects for the observation of the Sun from close distances, the thermal stability of the entrance film filter is an important characteristic. In this paper, the thermal stability of Al films with 2.5 nm thick MoSi2 protective cap layers has been studied. MoSi2 was chosen as a coating material because MoSi2 caps effectively protect the Al film from oxidation and simultaneously increase the mechanical strength of the Al film. Vacuum annealing of MoSi2/Al/MoSi2 films was carried out at temperatures up to 300°C. It has been demonstrated that at an annealing temperature of more than 200°C for 24 h, a noticeable decrease in the blocking properties of the MoSi2/Al/MoSi2 film is observed in the visible wavelength range, which is caused by the appearance of semi-transparent crystalline silicon dendritic structures that are tens of micrometers in size in the film. In the annealed area of the film specimen, the intermetallic Al12Mo phase was detected by electron diffraction structure analysis, indicating a possible reason for the appearance of silicon atoms needed for dendrite growth as a result of the chemical interaction of Al and MoSi2. Due to the requirements for a high degree of visible radiation blocking (106 to 107 times), the appearance of even one dendritic structure significantly reduces the blocking properties of the film filter and is, therefore, not permissible. Based on the measurement of the transmission of MoSi2-2.5 nm/Al-72 nm/MoSi2-2.5 nm films at 633 nm for isothermal annealing at 200°C-250°C, the activation energy for the formation of dendritic structures (E=1.55±0.1 eV) was measured and the maximum permissible film temperature (130°C) at which dendritic structures did not appear during a 5-year mission was predicted.
ABSTRACT
Al, with a passband in the wavelength range of 17-60 nm, and Zr, with a passband in the wavelength range of 6.5-17 nm, thin films on a support grid or support membrane are frequently used as UV, visible, and near-IR blocking filters in solar observatories. Although they possess acceptable optical performance, these filters also have some shortcomings such as low mechanical strength and low resistance to oxidation. These shortcomings hinder meeting the requirements for filters of future telescopes. We propose multilayer thin film filters on the basis of Al, Zr, and other materials with improved characteristics. It was demonstrated that stretched multilayer films on a support grid with a mesh size up to 5 mm can withstand vibration loads occurring during spacecraft launch. A large mesh size is preferable for filters of high-resolution solar telescopes, since it allows image distortion caused by light diffraction on the support grid to be avoided. We have investigated the thermal stability of Al/Si and Zr/Si multilayers assuming their possible application as filters in the Intergelioprobe project, in which the observation of coronal plasma will take place close to the Sun. Zr/Si films show high thermal stability and may be used as blocking filters in the wavelength range of 12.5-17 nm. Al/Si films show lower thermal stability: a significant decrease in the film's transmission in the EUV spectral range and an increase in the visible spectrum have been observed. We suppose that the low thermal stability of Al/Si films restricts their application in the Intergelioprobe project. Thus, there is a lack of filters for the wavelength range of λ>17 nm. Be/Si and Cr/Si filters have been proposed for the wavelength range near 30.4 nm. Although these filters have lower transparency than Al/Si, they are superior in thermal stability. Multilayer Sc/Al filters with relatively high transmission at a wavelength of 58.4 nm (HeI line) and simultaneously sufficient rejection in the wavelength range near 30.4 nm (HeII line) have been fabricated. They are planned to be used in the project KORTES, whose telescopes will have an EUV channel at 58.4 nm.
