Wenda Peng

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.

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.

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.

The MCP dynamic characteristics with different bias voltage

Microchannel plate (MCP) is a core part of the X-ray framing camera. Studying the dynamic characteristics of the MCP is critical to understanding the data obtained by the framing camera. The dynamic characteristics of the MCP with different dc bias voltage are simulated by using the Monte Carlo method. The relationship between the theoretical exposure time and the MCP bias voltage is obtained. A MCP gated X-ray framing camera is developed. The measured exposure time increase 9 ps while the MCP bias voltage is -300 V comparing to -200 V. The simulation and experimental results show that the exposure time and gain of the MCP are both increased while the negative bias voltage is increased.

Design of remote control system for x-ray framing camera

This paper describes the implementation of a remote control system, where a PC and a single chip microprocessor are used in a dedicated application to remote control an X-ray framing camera. It can implement some programmable functions, such as driving pulse width adjustment, delay time adjustment between drivin8g pulses, MCP and phosphor screen bias voltage control. These parameters can be selected with the key board in front panel or with the host computer. A very simple communication link is presented using the ordinary communication protocol RS-232.