Qinlao Yang

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.

A sort of pulsed microfocal x-ray source

A sort of pulsed microfocus x-ray source has been theoretically and experimentally studied. The portable x-ray source is composed of three portions: LaB6 crystal cathode electron gun emitting system, electrostatic focusing system, and metal target system. The electrons are emitted form the hot crystal cathode, and controlled by modulated Wehnelt grid bias value and the ratio Dw/H, and concentrated by two-equal-radius-cylinder-electrodes focusing system. The x-ray photons are irradiated by high energy electron beam bombarding metal target. The new x-ray sources general-purpose capabilities such as pulsed radiation, focal spot size and luminance were preliminary tested. When the temperature of LaB6 cathode is about 1900K and partial pressures being kept below 10-7 torr, the minimal focus diameter is merely about 10 microns with the pulse width 65ms.

Design and theoretical investigation of a digital x-ray detector with large area and high spatial resolution

X-ray phase contrast imaging is a promising new technology today, but the requirements of a digital detector with large area, high spatial resolution and high sensitivity bring forward a large challenge to researchers. This paper is related to the design and theoretical investigation of an x-ray direct conversion digital detector based on mercuric iodide photoconductive layer with the latent charge image readout by photoinduced discharge (PID). Mercuric iodide has been verified having a good imaging performance (high sensitivity, low dark current, low voltage operation and good lag characteristics) compared with the other competitive materials (α-Se,PbI2,CdTe,CdZnTe) and can be easily deposited on large substrates in the manner of polycrystalline. By use of line scanning laser beam and parallel multi-electrode readout make the system have high spatial resolution and fast readout speed suitable for instant general radiography and even rapid sequence radiography.

Fabrication and characterization of large area mercuric iodide polycrystalline films

Mercuric iodide (HgI2) polycrystalline films are being developed as a new photoconductor layer for direct converter X-ray imaging detector. A physical vapor deposition (PVD) device for HgI2 deposition was developed specially. Depending on the device and low purity (99.5%) low-cost HgI2 source material, polycrystalline HgI2 films have been grown with dimensions Φ130 mm in diameter onto ITO-coated glass substrate. The grown techniques used can be easily extended to produce much larger films areas and the thickness of the grown layers, size of the grains and crystallinity can be regulated in a controlled way by adjusting the growth parameters. The basic physical characteristic, dark current and response characteristic to X-ray for the grown polycrystalline film were tested and the results show that the film has preferred crystalline orientation (00l), low dark current density less than 10 pA/mm2, high volume resistivity in the order of 1013 Ω•cm and high X-ray response sensitivity of about 16 μC/(cm2•R), and the results put HgI2 polycrystalline films in position as a leading candidate material for use in digital X-ray imaging system.

Study of a new portable x-ray source with micro-beam

A novel X-ray source with micro-beam has been studied in theory and experiment. The source is composed of three portions: LaB6 crystal cathode electron gun emitting system, electrostatic focusing system, and permutable metal target system. The electronic current emitted by the electron-gun are controlled by modulating cathode temperature and Wehnelt grid voltage and ratio Dw/H, two-equal-radius-cylinder-electrodes focusing system concentrates electron beam, the X-ray photons are irradiated by high energy electron beam bombarding the metal target. The new x-ray sources general-purpose capabilities such as continuous radiation and pulse radiation, focus size and luminance, are also tested. When the temperature of LaB6 cathode is about 1900K and partial pressures being kept below 10-7 torr, the minimal focus diameter is merely about 10 microns. The new micro focus x-ray source has other lots of advantages such as economy, safety and facility.

Multispectral multiphoton fluorescence lifetime imaging

We report the development and detailed calibration of a multispectral multiphoton fluorescence lifetime imaging system that is the combination of a streak camera, a prism spectrophotometer, a gradient index microlens array and an ultrafast laser.