Modified hartmann method for measuring wide-aperture adaptive mirrors

Various laser systems use wide-aperture adaptive mirrors containing dozens or hundreds of drives. Thousands of high-precision measurements are based on the use of such mirrors. A simple, cheap, high-precision, and rapid method specifically designed to study the characteristics of these mirrors with a large number of degrees of freedom is described.     

A source of a wide-aperture gas-discharge plasma flow

The described generator produces a wide-aperture flow of charged plasma particles (electrons, positive and negative ions) with a cross-sectional diameter of at least 120 cm, which propagates to a distance of 50 cm or more (depending on the operating mode and the geometric dimensions of the vacuum chamber). The uniform distribution of charged particles in the cross section of the plasma flow is at least 98%. The discharge current reaches 1 A or more at an accelerating voltage of 0.3–6 kV. The energy of particles in the plasma flow under such conditions was 10–6000 eV at current densities of up to 10 mA/cm². The generator structure contains coaxially positioned meshes of the anode grid and the cathode grid. The latter closes the cavity inside the cathode volume at a depth of 3–5 mean free paths of electrons in the gas-discharge plasma flow. The cathode is manufactured so that the cavity diameter exceeds the diameter of the through cavity in the cathode insulation, the latter being determined by the size of the plasma-flow cross section. The distance between the grid anode and the cathode grid is equal to the Aston dark space of a glow discharge, thus permitting the cathode lifetime to be increased to 3 years. It is shown that the duration of the cathode continuous operation is determined by the chosen values of its cavity depth and accelerating voltage.     

A wide-aperture Cerenkov counter with a water radiator

The design of a Cerenkov counter with a water radiator (200×400 mm), containing a wavelength shifter, is described. The counter was used for π- andK-meson selection in a positive-particle beam with 250–1000-MeV/c momentum.     

A system of multiwire drift chambers for wide-aperture spectrometers

A system of wide-aperture drift chambers with an operating area of 2.5×1.9 m² and 1.5×1.5 m² is described. The chamber, operating with two gas mixtures, is studied. The dependence of the chambers efficiency on the high voltages applied to the cathodes and potential wires, and the time distributions are presented. Using the system of drift chambers, a spatial distribution of ∼ 180 μm was achieved for straight tracks in a 8-mm drift gap. The chambers were included in the track systems of the VES and GAMS spectrometers at the Y-70 accelerator of the Institute for High-Energy Physics (Protvino).     

A time-of-flight measurement system for the HADES wide-aperture dielectron spectrometer

The HADES spectrometer and a time-of-flight detector based on long-sized (50–250 cm) scintillation counters are described. The detector is designed for identification of electrons, pions, and protons with momenta of 0.1–1.5 GeV/c at a flight distance of 220–250 cm. The operating conditions are analyzed, and the requirements to the detector and counter design are formulated. The design of the counters and their arrangement in the spectrometer are considered. The results of experimental studies of such characteristics of long counters as the light attenuation length in a scintillator and temporal and spatial resolutions, dependeing on the location of the point of the particle’s hit on the counter, are presented. Analysis of the data has shown that the main factor determining the spatial resolution of long counters is the quality of the polishing of the side faces of the scintillators, which determines the effective (averaged over the scintillator side surfaces) coefficient of total internal reflectionR. It is shown that, forR>-0.99, it is quite possible to achieve temporal and spatial resolutions of 100 ns and 2–3 cm, respectively, for scintillators with a length of up to 250 cm and a cross section of 1–20 cm². Foreign and Russian photomultipliers were used in the counters.     

A wide-aperture x-ray source with high intensity and uniformity of radiation

The results of experimental research on an x-ray source intended for preionizing the laser mixture in wide-aperture electric-discharge excimer lasers are presented. An experimental prototype of the source in which an x-ray radiation pulse is formed in an inverted-type vacuum diode during braking of accelerated electrons in a tantalum foil has been developed. It is shown that the use of a metal-dielectric cathode allows generation of x rays with nonuniformity of the intensity distribution within limits of 10% at an energy of quanta no higher than 55 keV and a radiation exposure dose 160 mR.     

The data-acquisition system of a muon tomograph based on on-chamber electronics

The data-acquisition system of a muon tomograph based on the on-chamber electronics is described. Its advantages over the previously used system based on the electronics made to the VME-9U standard are considered. The hardware component and the software of the new data-acquisition system are presented.     

大面积纳米压印光刻晶圆级复合软模具制造

为了解决大面积纳米压印所面临的大尺寸晶圆级复合软模具低成本制造的难题,对于当前广泛使用的大尺寸晶圆级双层复合软模具开展了理论分析、数值模拟和制造方法的系统研究。提出并建立了复合软模具脱模过程和气泡缺陷理论模型;利用ABAQUS工程模拟软件,揭示了大尺寸复合软模具影响脱模的因素和内在规律;提出一种大尺寸晶圆级双层复合软模具低成本制造方法,并完成了10.16cm(4inch)满片双层复合软模具复制的实验验证。研究结果为大尺寸复合软模具制造奠定了理论基础,并提供了一种低成本高质量制造大尺寸晶圆级双层复合软模具切实可行的方法。     

The output window of a large-area accelerator with an increased electron-beam current density

The results of theoretical and experimental investigations of a large-area accelerator with a new type of output window are presented. With this window, it is possible to increase the current density of the extracted electron beam, reduce the operating temperature of the foil, and extend its service life. A two-level support structure with cooling of each level is used for this purpose. The heat load of the foil mounted on the second level of the support structure that carries the main mechanical load is reduced by partial interception of the thermal power due to direct loss of the electron beam, which is released on the first level experiencing no mechanical load. The current loss at the structural elements of the output window is estimated, and the hydraulic characteristics and foil temperature in the output device are calculated. A higher current density of the beam extracted over the foil is attained in comparison with the conventional design of the support structure.     

Highly uniform manufacturing method for large-area microlens arrays

The microlens array is a key microstructure component in imaging systems, such as in light field cameras. A resolution of the light field camera can facilitate the use of a small-area microlens array. However, fabricating a large-area microlens array with a highly accurate and consistent surface finish is still difficult and high-cost. A low-cost manufacturing method is proposed in this study, where the mould core of the microlens array is fabricated with high precision and high uniformity by cylindrical ultra-precision diamond turning. The proposed tool path strategy is employed to achieve superior surface quality and avoid the dynamic vibration of an unsmooth path. Light field camera prototypes are developed using a commercial DSLR camera with a fabricated microlens array. The successful performance of the prototypes confirms that the proposed manufacturing method satisfies the application demands of large-area microlens arrays.     

A muon monitor for neutrino flux measurement

A method of determining the intensity of slow spill neutrino beams by monitoring the associated muons is described. Muons from poin and kaon decays which give rise to the beam neutrinos are sampled by a computer-controlled movable array of scintillation counter telescopes. The neutrino flux is obtained by matching the observed muon intensity distribution downstream of the hadron beam dump with that predicted by a Monte Carlo simulation of the decay process and the neutrino detector acceptance. Results from an experiment using a Fermilab narrow band neutrino beam gave a flux measurement accuracy of about 10%.     

Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.     

Laser interference fabrication of large-area functional periodic structure surface

Functional periodic structures have attracted significant interest due to their natural capabilities in regulating surface energy, surface effective refractive index, and diffraction. Several technologies are used for the fabrication of these functional structures. The laser interference technique in particular has received attention because of its simplicity, low cost, and high-efficiency fabrication of large-area, micro/nanometer-scale, and periodically patterned structures in air conditions. Here, we reviewed the work on laser interference fabrication of large-area functional periodic structures for antireflection, self-cleaning, and superhydrophobicity based on our past and current research. For the common cases, four-beam interference and multi-exposure of two-beam interference were emphasized for their setup, structure diversity, and various applications for antireflection, self-cleaning, and superhydrophobicity. The relations between multi-beam interference and multi-exposure of two-beam interference were compared theoretically and experimentally. Nanostructures as a template for growing nanocrystals were also shown to present future possible applications in surface chemical control. Perspectives on future directions and applications for laser interference were presented.     

Forward scintillation hodoscope for nuclear fragment detection at the high acceptance dielectron spectrometer (HADES) setup

The main characteristics of the forward scintillation hodoscope and readout electronics of the high acceptance dielectron spectrometer (HADES) at GSI (Darmstadt, Germany) are presented. Methods for adjustment and amplitude-time calibration of hodoscope detectors using cosmic rays and results of measurements of the Au + Au reaction at a beam energy of 1.24 GeV/nucleon are described. The use of the forward hodoscope for tagging the n + p reaction by means of the deuteron beam incident on a liquid hydrogen target is discussed. A procedure for determining the reaction plane angle in event-by-event analysis of the Au + Au reaction data (at 1.24 GeV/nucleon) is presented.     

A coordinate muon chamber based on thin-walled drift tubes

The design and manufacturing technology of a prototype coordinate detector module with dimensions of 2.0 × 0.5 m² on the basis of 2-m-long drift straw tubes are described. The selected design and technology allow large-area detectors to be constructed from these modules. Results of the module testing at gas pressures of 1–4 bar are described. The characteristic features of the module are a small radiation thickness, a high radiation hardness, a high detection efficiency for charged particles, as well as the feasibility of its high granularity (using small-diameter straw tubes and segmentation along the tube length). The possibility of optimizing the operating conditions of the module over a wide range of the working gas pressure is shown.     

Stroboscopic digital shearographic system for vibration analysis of large-area object

Digital shearography has become a competitive tool for vibration analysis due to its capability of full-field, high resolution, and high-speed measurements. Many stroboscopic shearographic systems have been developed in recent years. However, they are only suitable for vibration analysis of a small area. This paper presents a shearographic system that was developed to carry out the vibration analysis of a large-area object whose area is 1 m² or even bigger. The system can use both time-average and stroboscopic illumination methods to analyze the forced vibration distribution. The setup of the system is introduced and experimental results are presented.     

大面积复杂掩模图形的快速光刻仿真研究

大面积复杂掩模图形的光刻仿真,要同时满足高精度和高效率两个要求。为克服现有方法积分区域大,计算效率低等问题,提出了一种基于最有效影响区域的简化计算方法。该方法首先利用波前分割的方法确定影响光刻胶目标场点光强的最有效影响区域,以此局部区域替代原来的整体积分区域作光强的计算,将积分区域由整个掩模图形缩小为图形的一小部分。试验结果表明,该算法与现有方法比较,精度上非常接近,但速度显著加快,且稳定可靠。该方法能够快速准确地对大面积复杂掩模图形进行光刻仿真,具有重要的应用价值。     

Two-stage focus-hold system for rapid ultra-sensitive read-out of large-area biochips

We report here the development of a method for holding the focal plane in a fluorescence-based biochip scanner. The fast read-out of large (multiple cm²) glass slides as used in modern chip technology imposes severe constraints on the focal system. The limited focal depth of high-NA objectives together with the demand for single-molecule sensitivity challenges traditional focus-hold systems. Various long- and short-term effects disturb the often multiple hour-long data-acquisitioning process and cause blurred or unusable image data. Traditional focus-hold systems were often limited in terms of range, reaction time, sensitivity or demanded a large number of additional components. Our system uses the back-reflected illumination beam always present in total internal reflection fluorescence microscopy to generate an error proportional electrical signal, which in turn drives an actuator correcting the objective–sample distance. The latter consists of a fast but range-limited piezo drive attached to the objective and a slower motor coupled to the microscope's z-drive. With this combination, fast reaction times and virtually unlimited correction distances are possible. We show the applicability by scanning DNA microarrays on 27 × 18-mm² glass slides with single-molecule sensitivity over the whole array. Single-fluorescence dyes are imaged as diffraction-limited spots.     

A large-area streak tube with magnetic focusing and fast image scan

Certain problems encountered in the development of a large-area streak tube (ST) with magnetic focusing and fast image scan are considered. It is shown that the use of a spherical accelerating electrode made of fine-structure mesh makes it possible to considerably increase the ST working area. The designs of the large-area ST are described, and its estimated characteristics are presented. The large-area ST based on these calculations has found practical use in a streak camera designed to operate with a resolution of the order of 2 ps in the soft X-ray region.     

High-efficiency finishing process for metal mold by large-area electron beam irradiation

A new finishing process for metal molds by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high-energy density is irradiated without focusing the beam, and so the EB with a maximum diameter of 60 mm can be used for melting or evaporating metal surface instantly. Experimental results show that the surface roughness decreases from 6 μmRz to less than 1 μmRz in just a few minutes under proper machining conditions. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore, the surface roughness of tilting surface close to 90° could be well improved. Therefore, large-area EB irradiation method has a possibility to become a high-efficiency finishing process for metal molds.