Lihong Niu

Application of a fast electrical pulse in gated multichannel plate camera

An eight-frame gated microchannel plate (MCP) camera and a gating electrical pulse are described in this article. The gating electrical pulse is obtained by first generating a high voltage fast step pulse using avalanche transistors in Marx bank configuration, and then shaping it using avalanche diodes. The high voltage fast step pulse is about 200 ps in fall time and 4 kV in amplitude. The gating pulse wave form with width of 160 ps and amplitude of 2.5 kV is achieved. Each frame photocathode coated with gold on the MCP is part of a 12 Omega transmission line with open circuit end driven by the gating electrical pulse. The camera is tested by illuminating its photocathode with ultraviolet laser pulses, 266 nm in wavelength, which shows exposure time as short as 120 ps.

Monte Carlo simulation for microchannel plate framing camera

A microchannel plate (MCP) framing camera is simulated by using the Monte Carlo method. Considering that the laser pulse width has effect on the experimental exposure time, we simulate the experimental exposure time varying with the laser pulse width. The gain characteristics of the MCP framing camera are simulated while the MCP is applied with very short electrical gating pulses. A new method is presented using a nongain MCP instead of a gain MCP.

Demonstration of 11-ps exposure time of a framing camera using pulse-dilation technology and a magnetic lens

Abstract. A framing camera with high temporal and spatial resolution is demonstrated using pulse-dilation technology and a magnetic lens. The magnetic field of the magnetic lens is simulated using LORENTZ-3EM software, and the magnetic field distribution on-axis is similar to a Gaussian function. The temporal and spatial resolutions of the instrument are measured using light at the wavelength of 266 nm from a frequency tripled femtosecond laser. The measured exposure time of this camera is ∼11  ps, and the spatial resolution is better than 100  μm.

Note: Non-gain microchannel plate gated framing camera

An x-ray framing camera using a non-gain microchannel plate (MCP) is reported in this article. The advantage of the non-gain MCP is the less transit time spread. The non-gain MCP gated framing camera has four microstrip line cathodes with 6 mm in width. The time domain reflectometry curves of the four microstrip lines are measured, which show that the characteristic impedance of each microstrip line is about 17 Ω. While the photocathode is driven by the gating electrical pulse with width of 125 ps and amplitude of -1.48 kV with -400 V bias, the measured exposure time of this camera is about 72 ps.

Theoretical analysis of a time focus and time amplifier cavity in streak tube

During the last few years, The time resolution of X-ray streak cameras have been improved to near 300-fs. Due to the relative slower sweeping speed and initial energy distribution of electrons, It is hard to breakthrough the 100 fs time resolution barrier. In this letter, time focus and time amplifier system is proposed. The time focus system is used to compensate the time dispersion between photocathode and anode. The using of a time amplifier improves the technical time resolution. The time focus and time amplifier system is designed to a compact fast electrons cavity structure.

MCP gated x-ray framing camera

A four-frame gated microchannel plate (MCP) camera is described in this article. Each frame photocathode coated with gold on the MCP is part of a transmission line with open circuit end driven by the gating electrical pulse. The gating pulse is 230 ps in width and 2.5 kV in amplitude. The camera is tested by illuminating its photocathode with ultraviolet laser pulses, 266 nm in wavelength, which shows exposure time as short as 80 ps.

Recent advance in streak and framing cameras in Shenzhen University

In this paper, we report on the recent development of streak and framing camera techniques in Shenzhen University, such as soft X-ray streak image tube, synchroscan streak image tube, image intensifier and different kinds of newly developed electronic circuits. In particular, we present three different kinds of streak and framing cameras, including a soft X-ray streak camera with slit length of 30mm, dynamic spatial resolution of 15lp/mm and dynamic range of larger than 900; a specially designed synchroscan picosecond streak camera with a repetition rate of 1MHz, which can provide simultaneous time- and spectrum-resolved two-dimensional(2D) sampling information for biomedical imaging; and an 8 channel framing camera with exposure time of 3ns and dynamic spatial resolution of better than 20lp/mm.

Compact 8-way fast high voltage pulses generation with variable pulse width and interval time

A programmable 8-way fast high voltage pulses generation built with avalanche transistors are studied. The fall time of raw pulse is 200 ps with amplitude about 2 kV. The fall time is determined by transit time of carries in collector-base region and it can be improved much by increasing the potential in this region. The pulse width can be switched programably with 1-ns, 2-ns and 5-ns. The pulses interval time also can be switched programably. The cover time range of 8-way pulses is more than 80-ns.

Monte Carlo simulation for x-ray detector

X-ray detector based on the gated microchannel plate (MCP) is a powerful diagnostic tool for laser-driven inertial confinement fusion and fast Z-pinch experiments. In order to understand the behavior of the MCP used in such detector, the X-ray detector is simulated using the Monte Carlo method. By simulating the electron cascade in the MCP, the relationship between the MCP gain and voltage is obtained. The time, position and energy of the electrons at the MCP output surface are calculated. The transit time distribution, the electron-channel wall collision number distribution and the time distribution of the electrons travel from the MCP to the phosphor screen are given. Spatial resolution simulations of the MCP-based detector are also presented.

Improvement for exposure time measurement of the microchannel plate gated framing camera

The method of exposure time measurement for the microchannel plate gated X-ray framing camera is presented in this paper while the propagation on the microstrip line of the gating pulse is considered. The delay time of the fiber images is analyzed, which is 2 ps, 10 ps or 18 ps in different situations. While the propagation time of the gating pulse is considered, the measured exposure time of the framing camera is 96 ps, comparing to 53 ps without considering.