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Aims: In this work, we evaluated the performance of three pitches positron emission tomography (PET) detectors for building a high-resolution small-animal PET imaging experimental platform. Methods: The evaluation of PET detectors includes twodimensional crystal identification, energy resolution, and crystal look-up table. The nuclear instrumentation module and PXI data acquisition (DAQ) system were both used to obtain flood images. The energy spectrum of the Na-22 source was measured. PET detectors of 2.0 and 1.6 mm pitches used in our present experiment were composed of lutetium yttrium oxyorthosilicate (LYSO) crystals directly coupled to position-sensitive photomultiplier tubes (PSPMTs). The 1.3-mm pitch detector comprises a LYSO crystal, a tapered light-guide, and a PSPMT. The crystal sizes of the detectors were a 10 × 10 array of 2.0 × 2.0 × 10 mm 3 crystals, a 10 × 10 array of 1.6 × 1.6 × 10 mm 3 crystals, and an 18×18 array of 1.3×1.3×10 mm 3 crystals, respectively. Due to the lower sampling frequency of the DAQ system, a spline interpolation algorithm was introduced in the signal waveform to reconstruct the peak values. Results: The experimental results indicated that all three PET detector crystals could be clearly identified. A detailed analysis demonstrated that the key characteristic full width at half maximum (FWHM) values of the crystals profile could reach 0.46 ± 0.03, 0.32 ± 0.03, and 0.21 ± 0.02 mm, while the crystal average energy resolutions were 16.8% ± 1.76%, 20.1% ± 2.24%, and 31.5% ± 3.76%, which correspond to B YongZhi Yin yinyzh@lzu.edu.cn 1 School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China pitches of 2.0-, 1.6-, and 1.3-mm, respectively. Conclusions: The PET detector modules of LYSO crystal arrays could be potentially used in the small-animal PET imaging applications and are promising to achieve submillimeter PET images.

Due to the beam related background, the inner chamber of BESIII MDC has aging effect after 5 years running. The gains of the inner chamber cells decrease obviously, and the max gain decrease is about 26% for the first layer cells. A new inner drift chamber with eight stereo sense wire layers as a backup for MDC is under construction, which is almost the same as the current one but using stepped endplates to shorten the wire length beyond the effective solid angle. This new structure will be of benefit to reducing the counting rate of single cell. The manufacture of each component is going smoothly, and the new inner drift chamber will be finished by the end of April 2014.Comment: 4 pages, 4 figures, proceedings for the XXXIII international symposium on Physics in Collision (PIC2013