Zhenjie Li

Design, simulation and testing of large area silicon drift detectors and detector array for X-ray spectroscopy

Large area (25 mm/sup 2/) silicon drift detectors and detector arrays (5/spl times/5) have been designed, simulated, and fabricated for X-ray spectroscopy. On the anode side, the hexagonal drift detector was designed with self-biasing spiral cathode rings (p/sup +/) of fixed resistance between rings and with a grounded guard anode to separate surface current from the anode current. Two designs have been used for the P-side: symmetric self-biasing spiral cathode rings (p/sup +/) and a uniform backside p/sup +/ implant. Only 3 to 5 electrodes are needed to bias the detector plus an anode for signal collection. With a graded electrical potential, a sub-nanoampere anode current, and a very small anode capacitance, an initial FWHM of 1.3 keV, without optimization of all parameters, has been obtained for 5.9 keV Fe/sup 55/ X-rays at RT using a uniform backside detector.

HEPS-BPIX, a hybrid pixel detector system for the High Energy Photon Source in China

A hybrid pixel detector with single photon counting mode has been designed for the High Energy Photon Source in China. It features a pixel size of 150 μm × 150 μm and a frame rate up to 1.2 kHz with 20-bit dynamic range. Six modules were assembled as the first prototype system, covering an area of 9 cm × 10 cm with 360k pixels. Images have been taken using X-ray and synchrotron radiation light, and the preliminary detector performance is presented.

A High Frame Rate Test System for the HEPS-BPIX Based on NI-sbRIO Board

HEPS-BPIX is a silicon pixel detector designed for the future large scientific facility, high-energy photon sources (HEPS) in Beijing, China. It is a high frame rate hybrid pixel detector which works in the single-photon-counting mode. High frame rate leads to much higher readout data bandwidth than former systems, which is also the difficulty of the design. Aiming to test and calibrate the pixel detector, a test system based on the National Instruments single-board RIO 9626 and LabVIEW program environment has been designed. A series of tests has been carried out with X-ray machine as well as on the Beijing Synchrotron Radiation Facility 1W2B beamline. The test results show that the threshold uniformity is better than 60 electrons and the equivalent noise charge is less than 120 electrons. Besides, the required highest frame rate of 1.2 kHz has been realized. This paper will elaborate the test system design and present the latest testing results of the HEPS-BPIX system.

Implementation of ultrafast X-ray diffraction at the 1W2B wiggler beamline of Beijing Synchrotron Radiation Facility.

The implementation of a laser pump/X-ray probe scheme for performing picosecond-resolution X-ray diffraction at the 1W2B wiggler beamline at Beijing Synchrotron Radiation Facility is reported. With the hybrid fill pattern in top-up mode, a pixel array X-ray detector was optimized to gate out the signal from the singlet bunch with interval 85 ns from the bunch train. The singlet pulse intensity is ∼2.5 × 10(6) photons pulse(-1) at 10 keV. The laser pulse is synchronized to this singlet bunch at a 1 kHz repetition rate. A polycapillary X-ray lens was used for secondary focusing to obtain a 72 µm (FWHM) X-ray spot. Transient photo-induced strain in BiFeO3 film was observed at a ∼150 ps time resolution for demonstration.

Proton irradiation effect on SCDs

The Low Energy X-ray Telescope is one of the main payloads on the Hard X-ray Modulation Telescope satellite. Swept charge devices (SCDs) are selected as detectors for the Low Energy X-ray Telescope. As SCDs are sensitive to proton irradiation, irradiation tests were carried out on the HI-13 accelerator at the China Institute of Atomic Energy. The beam energy was measured to be 10 MeV at the SCD. The proton fluence delivered to the SCD was 3x10(8)protons/cm(2) over two hours. By comparing the performance before and after irradiation, it is concluded that proton irradiation affects both the dark current and the charge transfer inefficiency of the SCD. The energy resolution of the proton-irradiated SCD is 212 eV@5.9 keV at -60 degrees C, while it before irradiated is 134 eV. Moreover, better performance can be reached by lowering the operating temperature of the SCD in orbit.