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In the heavy ion radiotherapy, the dose distribution is an important index to ensure the therapeutic effect. But it can not be directly measured during a treatment. Positron-emitting radionuclides (10 C, 11 C, and 15 O et al.) produced in the treatment process are deposited along the path and the end of the beam trajectory, so the positron activity distribution can be used to monitor the dose distribution of carbon ions. In this paper, we present results of measurements of positron activity distributions with a developed scanner system. Then the relationship between the activity distribution of positrons and the dose distribution of carbon ions is studied. The research shows that the activity distribution of positrons is quite similar to that of carbon ions in the direction of penetration depth. The activity peak position of positrons is smaller than the dose peak position of carbon ions, and this difference increases along with the increase of carbon ion beam energy. These experimental results are consistent with the GATE simulation results. It is found that the detector system can distinguish shift of peak position of 3 mm that corresponds change of a particle energy of 4 MeV/u. This indicates that the positron scanner system had been successfully developed for heavy ion therapy equipment.

At present, the proportion of water drive fractured wells is as high as 85.8%, and the proportion of repeated wells is as high as 47.7%. In view of this reality, the potential tapping objects are gradually transferred to isolated sand body, river channel edge and top of thick oil layer. Due to the limited fracture length ratio of conventional fracturing, the potential tapping effect is poor. Therefore, the sand body fracturing method is adopted for this section, that is, increasing the fracturing scale and improving the production degree of oil layer by increasing the fracture length ratio. According to the statistics of the effect of sand control fracturing well, combined with the sand body development characteristics, connectivity characteristics and injection production relationship, the influencing factors of sand control fracturing effect are analyzed, and the applicability of sand control fracturing technology in Lamadian oilfield is clarified.

At present, digital resources have become an important part of the collection resources of modern small and medium-sized libraries. As a new technology, cloud computing technology has been widely used in the field of small and medium-sized libraries, and has just begun to enter the vision of professional researchers. This paper studies the application of cloud computing and virtualization technology in IT management and service of small and medium-sized libraries. In order to better understand the application and help of cloud computing and virtualization technology in IT management and service of small and medium-sized libraries, this paper applies cloud computing and virtualization technology to it management and service in a university library, and then carries out a survey and statistics of the figure The library has developed a questionnaire to investigate the library staff and readers’ feelings about the application. The results show that under the support of cloud computing and virtualization technology, IT management and service for small and medium-sized libraries can significantly improve the management efficiency and service quality of libraries.

In this paper, we report the first experimental observation of internal resonance in a dusty plasma, which shows the intrinsic nonlinearities of dust interactions in plasmas. When driving a system of vertically aligned dust particle pairs in the vertical direction, the horizontal motion is found to be excited during onset of internal resonance when the higher-frequency horizontal sloshing mode is nonlinearly coupled to the vertical breathing mode through the 1:2 commensurable relation. A theoretical model of the nonlinear interaction of dust particles in plasma is also provided and the results of the theoretical model are shown to match experimental observations.

This paper presents the readout electronics for the array detectors in the external target facility of the HIRFL-CSR. The readout system is divided into readout partitions, each of which includes four Front-end Cards (FECs) and one Readout Control Unit (RCU). The FEC measures the energy of the particle hit on the detectors and converts it into current signal. The RCU processes the triggers from the central trigger unit, digitizes the raw signal from the FECs, performs data processing algorithms and transmits the data to the data acquisition system in a specified format. The readout electronics has been characterized in the lab and installed in the detectors. The design, implementation and test of the readout electronics has been discussed.

The coagulation and growth process of dust particles is investigated through laboratory experiment in a plasma system. A large number of dust particles with different sizes and shapes are formed. The growth process is characterized by the scattering laser intensity and fractal dimension. The comparisons of dust particles and scattering laser intensity obtained at different rf powers are presented. The three-dimensional distribution of dust particles is also given. These results provide an experimental basis for dust growth investigation.

A prototype of time-of-flight positron emission computed tomography (TOF-PET) has been developed for acquiring the coincident detection of 511 keV γ-rays produced from positron annihilation. It consists of two 80.5 mm×80.5 mm LYSO scintillator arrays (composed of 35 ×35 pixel finger crystals) with the position sensitive photomultiplier tubes R2487 as the readout. Each array is composed of 2 mm ×2 mm×15 mm finger crystals and the average pixel pitch is 2.30 mm. The measured results indicate that the TOF information has the potential to significantly enhance the image quality by improving the noise variance in the image reconstruction. The best spatial resolution (FWHM) of the prototype for the pairs of 511 keV γ-rays is 1.98 mm and 2.16 mm in the x and y directions, respectively, which are smaller than the average pixel pitch of 2.30 mm.

Single-walled carbon nanotubes (SWNTs) were synthesized by pyrolyzing methane (CH4) at a temperature of 900 degrees C on SiO2 substrates pre-coated with iron nano-particles. Electrical contacts were fabricated onto one of the SWNTs by using an electron beam lithography process. Coulomb blockade and single-electron tunnelling characters were found at low temperatures, indicating that the SWNT in-between the electrodes forms a quantum dot. It is found that the Coulomb gap of the quantum dot is about 8.57 meV, and the factor a, which converts the gate voltage to the true electrostatic potential shift, is around 200 for this device.

A new Digital Pulse Processing (DPP) module has been developed, based on a domino ring sampler version 4 chip (DRS4), with good time resolution for LaBr3 detectors, and different digital timing analysis methods for processing the raw detector signals are reported. The module, composed of an eight channel DRS4 chip, was used as the readout electronic and acquisition system to process the output signals from XP20D0 Photomultiplier Tubes (PMTs). Two PMTs were coupled with LaBr3 scintillator and placed face to face on both sides of a radioactive positron 22Na source for 511 keV gama ray tests. By analyzing the raw data acquired by the module, the best coincidence timing resolution is about 194.7 ps (FWHM), obtained by the digital constant fraction discrimination (dCFD) method, which is better than other digital methods and analysis methods based on conventional analog systems which have been tested. The results indicate that it is a promising approach to better localize the positron annihilation in positron emission tomography (PET) with time of flight (TOF), as well as for scintillation timing measurement, such as in TOF-DeltaE and TOF-E systems for particle identification, with picosecond accuracy timing measurement. Furthermore, this module is more simple and convenient than other systems.

In order to solve the problem of influence on measured spectrum caused by the ion current with unstable current intensity, we developed a set of device which can acquire and save the data of ion current intensities in real time during experiment. By means of off-line normalizing th saved data by PC, the influence will be eliminated efficiently.

The Gamma Ray Array Detector (GRAD) is one subsystem of HIRFL-ETF (the External Target Facility (ETF) of the Heavy Ion Research Facility in Lanzhou (HIRFL)). It is capable of measuring the energy of gamma-rays with 1024 CsI scintillators in in-beam nuclear experiments. The GRAD trigger should select the valid events and reject the data from the scintillators which are not hit by the gamma-ray. The GRAD trigger has been developed based on the Field Programmable Gate Array (FPGAs) and PXI interface. It makes prompt trigger decisions to select valid events by processing the hit signals from the 1024 CsI scintillators. According to the physical requirements, the GRAD trigger module supplies 12-bit trigger information for the global trigger system of ETF and supplies a trigger signal for data acquisition (DAQ) system of GRAD. In addition, the GRAD trigger generates trigger data that are packed and transmitted to the host computer via PXI bus to be saved for off-line analysis. The trigger processing is implemented in the front-end electronics of GRAD and one FPGA of the GRAD trigger module. The logic of PXI transmission and reconfiguration is implemented in another FPGA of the GRAD trigger module. During the gamma-ray experiments, the GRAD trigger performs reliably and efficiently. The function of GRAD trigger is capable of satisfying the physical requirements.