Sun Zhijia

Time calibration for the end cap TOF system of BESIII

The time calibration for end cap TOF system of BESIII is studied in this paper. It has achieved about 110 ps time resolution for muons in dimu events. The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced. This paper also describes the study of using electrons and muons as calibration samples.

Neutron beam monitor based on a boron-coated GEM

A new thermal neutron beam monitor with a Gas Electron Multiplier (GEM) is developed to meet the needs of the next generation of neutron facilities. A prototype chamber has been constructed with two 100 mm×100 mm GEM foils. Enriched boron-10 is coated on one surface of the aluminum cathode plate as the neutron convertor. 96 channel pads with an area of 8 mm×8 mm each are used for fast signal readout. In order to study the basic characteristics of a boron-coated GEM, several irradiation tests were carried out with α source 239Pu and neutron source 241Am(Be). The signal induced by the neutron source has a high signal-to-noise ratio. A clear image obtained from α source 239Pu is presented, which shows that the neutron beam monitor based on a boron-coated GEM has a good two-dimensional imaging ability.

Synthesis, structure and luminescent properties of a new Vernier phase Lu7O6F9 doped by Eu3+ as potential scintillator with unique lath tube architectur

To explore novel nano-scintillator with a controllable architecture, pure and Eu3+ doped lutetium oxyfluoride (Lu7O6F9) powder were synthesized by combining mild hydrothermal method and solid state calcination approach. The products were all pure orthorhombic Vernier phase demonstrated by X-ray powder diffraction (XRD). The detailed crystal structure was also studied by Reitveld refinement. Lath-like microcrystals composed of nanoparticles with unique hollow tube of the products were supported by the images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Excited by X-ray with W as the target, the pure product showed intense broad emission with the peak at about 400 nm suitable for modern photoelectric multiplier tube (PMT), while the Eu3+ doped sample transferred the incident energy to Eu3+ ions and gave strong D-5(0)-> F-7(j) (j=0, 1, 2 and 4) emission, which fitted for imaging and labeling measurements. From the luminescent properties, both pure and Eu3+-doped products are potential excellent scintillator for X-ray imaging and other high energy detectors, and the pure product is also a good host candidate for rare earth doping.

Developments of a 2D position sensitive neutron detector

China Spallation Neutron Source (CSNS), one project of the 12th Five-Year-Plan scheme of China, is under construction in Guangdong province. Three neutron spectrometers will be installed during the first phase of the project, and two-dimensional position sensitive thermal neutron detectors are required. Before the construction of the neutron detectors, a prototype of a two-dimensional 200 mm×200 mm Multi-wire Proportional Chamber (MWPC) with Ar/CO2 (90/10) flowing gas has been constructed. In 2009, the prototype was tested with the 55Fe X-ray using part of the electronics, and performed well. Following the test in 2009, the neutron detector was constructed with the complete electronics and filled with the 6 atm. 3He+2.5 atm. C3H8 gas mixture in 2010. The neutron detector has been primarily tested with an Am-Be source. In this paper, new developments of the neutron detector including the design of the high pressure chamber, the optimization of the gas purifying system and the gas filling process will be reported. The results and discussion are also presented in this paper.

Study on the imaging ability of the 2D neutron detector based on MWPC

A 2D neutron detector based on 3He convertor and MWPC with an active area of 200 mm×200 mm has been successfully designed and fabricated. The detector has been tested with Am/Be neutron source and with collimated neutron beam with the wavelength of λ=1.37 Å. The best spatial resolution of 1.18 mm (FWHM) and good linearity were obtained. This is in good agreement with theoretical calculations.

The design of the readout system of two-dimensional position-sensitive GEM detector

In the Spallation Neutron Source, the performance of neutron detector and its readout system was related to whether the high neutron flux is fully utilized. So it have a very important significance in the large area position sensitive neutron detector. This paper introduced a neutron detection readout system based on GEM detector. GEM gas detector is always used in neutron detection, The detector used to achieve conversion of the Neutron signal which used GEM detectors, and the CIPIX chip is used as a preliminary amplifier, sharper, and discriminator. Then a FPGA based system is used to readout the electrical signal and process the data that acquire by CIPIX chip. Gigabit Ethernet is used as control interface and readout interface. The control command is received and the position information of the Neutron is send out through TCP/IP protocol. Event selection, data compress is implemented on FPGA. The host computer received the position information of The Neutron and then plotted the location map of the Neutron signal. At the same time it also can control the neutron detector system such as the mode of Event filer, the compress mode of the data. In our experimental environment, successfully detected the position of the neutron signal and analyzed the location map. The maxim event Rate is more than 4M with 32×32 resolution.

BESIII barrel time-of-flight （TOF） calibration using cosmic ray data

The principle of the method for the BESⅢ TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could reach about 150 ps, and the time resolution for one layer is achieved to be about 110 p...