A new ultrafast all-optical solid-state framing camera (UASFC) capable of single-shot ultrafast imaging is proposed and experimentally demonstrated. It is composed of an ultrafast semiconductor chip (USC), an optical time-series system (TSS), and a spatial mapping device (SMD) with an USC to transform signal beam information to the probe beam, a TSS to convert the time axis to wavelength-polarization, and a SMD to map wavelength-polarization image to different spatial positions. In our recent proof-of-principle experiment, better performance than ever of this technique is confirmed by giving six frames with ~3 ps temporal resolution and ~30 lp/mm spatial resolution.
The streak tubes with a large effective photocathode area, large effective phosphor screen area, and high photocathode radiant sensitivity are essential for improving the field of view, depth of field, and detectable range of the multiple-slit streak tube imaging lidar. In this paper, a high spatial resolution, large photocathode area, and compact meshless streak tube with a spherically curved cathode and screen is designed and tested. Its spatial resolution reaches 20 lp/mm over the entire Φ28 mm photocathode working area, and the simulated physical temporal resolution is better than 30 ps. The temporal distortion in our large-format streak tube, which is shown to be a non-negligible factor, has a minimum value as the radius of curvature of the photocathode varies. Furthermore, the photocathode radiant sensitivity and radiant power gain reach 41 mA/W and 18.4 at the wavelength of 550 nm, respectively. Most importantly, the external dimensions of our streak tube are no more than Φ60 mm × 110 mm.
The double-cone ignition scheme is a novel approach with the potential to achieve a high gain fusion with a relatively smaller drive laser energy. To optimize the colliding process of the plasma jets formed by the CHCl/CD shells embedded in the gold cones, an x-ray streak camera was used to capture the spontaneous x-ray emission from the CHCl and CD plasma jets. High-density plasma jets with a velocity of 220 ± 25 km/s are observed to collide and stagnate, forming an isochoric plasma with sharp ends. During the head-on colliding process, the self-emission intensity nonlinearly increases because of the rapid increase in the density and temperature of the plasma jets. The CD colliding plasma exhibited stronger self-emission due to its faster implosion process. These experimental findings effectively agree with the two-dimensional fluid simulations.
This article has introduces the basic components and characteristics of a femoto-second electron diffraction system, i.e. the photo-cathode, magnetic lens, deflector and detector with doubled MCP etc., and demonstrated our design method and results. The photo-cathode is an Ag film deposition on a sapphire disk and the femtosecond electron pulses are accelerated to 50 keV through an extraction electric field of 10kV/mm between the photocathode and the extraction mesh. After extraction, the electron pulses are reshaped in size by a 100 μm pinhole, which screens out electrons with larger elevation angle and makes the passed electrons flying almost parallel to the axis, which results in a reduced electron beam spot. The beam is collimated with a magnetic lens and positioned to the sample by a pair of deflection plates for diffraction measurements. The electron diffraction images are recorded with a two-dimensional imaging system composed of a Chevron-type microchannel plate and a P20 phosphor screen on an optical-fiber faceplate. The initial position, kinetic energy and angle distribution of the photoelectrons is sampled with Monte Carlo method. The electric field is calculated with finite difference formula, and the magnetic flux of the focus region is calculated with finite elements methods, and the electron trajectory is traced with Runge-Kutta method. We analysized the temporal and spatial distribution of 3000 electrons when they reached the prime plane and give out the temporal and spatial modulation transfer function of the femoto-diffraction system.
In this paper, a high spatial resolution, high gating speed framing camera capable of four separate two-dimensional images is designed and tested. A mirror-based image splitter has been designed and developed to provide a separate image for each arm with equal path length and equal intensity splitting while having a spectral flat response. Fast gating of a single frame is accomplished by using a proximity-focused microchannle-plate image-intensifier (MCPII) gated by a MOSFET-based pulse module with adjustable gate width from 3 ns to D.C. operation. Multiple frames are obtained by using multiple gated tubes with time intervals between consecutive frames can be adjusted flexibly. Its spatial resolution reaches 36.5 lp/mm with each frame having a 4.6-ns gate width. Furthermore, a three-dimensional MCPII model is developed to investigate the transit time and spatial resolution of the proximity-focused MCPII based on the Finite Integral Technique (FIT) and Monte Carlo method (M–C method).
Qualitative and quantitative measurements of complex flows demand for fast single-shot fluorescence lifetime imaging (FLI) technology with high precision. A method, single-shot time-gated fluorescence lifetime imaging using three-frame images (TFI-TGFLI), is presented. To our knowledge, it is the first work to combine a three-gate rapid lifetime determination (RLD) scheme and a four-channel framing camera to achieve this goal. Different from previously proposed two-gate RLD schemes, TFI-TGFLI can provide a wider lifetime range 0.6 ~ 13ns with reasonable precision. The performances of the proposed approach have been examined by both Monte-Carlo simulations and toluene seeded gas mixing jet diagnosis experiments. The measured average lifetimes of the whole excited areas agree well with the results obtained by the streak camera, and they are 7.6ns (N2 = 7L/min; O2 < 0.1L/min) and 2.6ns (N2 = 19L/min; O2 = 1L/min) with the standard deviations of 1.7ns and 0.8ns among the lifetime image pixels, respectively. The concentration distributions of the quenchers and fluorescent species were further analyzed, and they are consistent with the experimental settings.