For heavy ion radiotherapy of tumors, a persistent worldwide challenge is the inability to accurately measure the actual depth of ion beams and to assess the precision of irradiation during treatment. Positron-emitters radionuclides such as [Formula: see text]C, [Formula: see text]C and [Formula: see text]O, generated during the treatment process, are deposited along the beam trajectory, enabling Positron Emission Tomography (PET) imaging and the monitoring of the dose distribution primary beam. Although the distribution of positron-emitters activity can be reconstructed by a PET system, establishing a correlation between this activity and the dose is a prerequisite for employing the system to assess carbon ion beam dose distribution. In this study, a dual flat-panel In-beam PET scanner was developed to investigate the relationship between the spatial activity distribution of positron products and the spatial dose distribution of carbon ions. Experiments revealed that along the Y-axis perpendicular to the beam direction, the positron activity peak shows a itional deviation of less than 0.5[Formula: see text]mm, allowing direct beam positioning. In the beam direction, however, while the two are correlated, they do not directly coincide under the same beam energy; a millimeter-level discrepancy exists between the positron activity peak and the dose peak, and this deviation increases with higher beam energy. Based on these findings, the study proposes that a dose monitoring model using positron activity distribution as input and incorporating machine learning methods can be established, paving a new pathway for in vivo range verification and precise dose control in carbon ion therapy.

This paper presents a heavy -ion in -beam PET, referred to as ibPET with a specifically custom designed data acquisition system, which was constructed and tested at the Heavy Ion Medical Machine (HIMM) beam -line, HICTC in Wuwei. The data acquisition system of ibPET has undergone several upgrades during the years, And its data processing capability now exceeds one million events per second per channel. To achieve optimal performance of the ibPET under existing conditions, we tested coincident events and noise equivalent count (NEC) under different time coincidence windows.The results show that the signal-to-noise ratio of the reconstructed image data reaches its peak when the time window is around 3 ns, indicating that the ibPET performance is optimal at this point. In order to determine the size of the time window, we measured the system's time resolution FWHM to be 1.63 ns, and ultimately chose a time window size of twice the time resolution FWHM, which is 3.25 ns. Meanwhile, we demonstrate the capability of our ibPET to monitor the dose range with various irradiation. The results demonstrate that the system exhibits the expected exponential decay in counting rate after irradiation, and accurately provides penetration depth positions at different energy levels.

A novel low-cost Ti-4.6Cr-3Fe beta-Ti alloy with twining induced plasticity effect was designed, and its tensile properties and deformation mechanisms were sensitive to its microstructural characteristic. The received sample with the microstructure of beta matrix embedded isothermal omega (omega(iso)) precipitations exhibited the largest tensile strength (R-m), but the limited ductility (<3 %). When the solution treatment (ST) temperature increased from below to above alpha ->beta transition temperature, the microstructure changed from beta matrix with alpha(s) precipitations to beta matrix with athermal omega (omega(ath)) precipitations, and the deformation mechanisms correspondingly changed from dislocation slip to the combination of dislocation slip and {332} deformation twins. Among different treatment samples, the ST800 sample obtained a relatively good combination of R-m (1146 MPa) and elongation to failure (EL, 12.5 %). It is surprising that, as the ST temperature increased from 800 degrees C to 900 degrees C, the R-m increased from 1146 MPa to 1230 MPa, but the fracture mode changes from ductile fracture to brittle fracture due to the formation of Laves phase (TiFe2) at grain boundaries. These findings provide a basis for improving the tensile properties of Ti-4.6Cr-3Fe alloy by adjusting the microstructure, and a reference for optimizing the composition of Ti-Cr-Fe system low cost beta-Ti alloys.

甘肃省是全国核工业建设早、规模大的省份之一,在发展核技术应用产业方向有着良好的工业基础和科研优势,在国家核产业二次战略布局中优势突出.从现状来看,甘肃具有政策优势、区域优势、资源优势等发展基础,也存在体制僵硬、市场冲击、人才流失等多种制约因素,这些因素严重阻碍了甘肃省核产业的高质量发展.如何扬长补短、抓住机遇,实现甘肃核技术应用产业高水平、高质量、可持续发展成为亟待解决的问题.本研究在实地调研的基础上,系统梳理甘肃省核技术发展的优势和瓶颈,凝练出甘肃核技术应用产业可持续发展的战略路线,为制定甘肃省核技术及产业可持续发展规划,推动甘肃省从核大省到核强省的转变提供参考依据.

TRansformation Induced Plasticity (TRIP) and TWinning Induced Plasticity (TWIP) have been successfully proposed to overcome the trade-off between strength and ductility of metastable β Ti alloys under static tensile deformation. However, whether they can be directly extended to impact deformation is still controversial due to the high strain rate and the existence of notch. In this work, Ti-4.7Al-6.26Mo-2.85Cr (TRIP Ti alloy) and Ti-8.5Cr-1.5Sn alloy (TWIP Ti alloy) were selected to compare the Charpy impact deformation behaviors and the corresponding deformation mechanisms. It was found that, under Charpy impact deformation, the primary deformation mechanism of TRIP Ti alloy was dislocation slip due to the massive stress-induced martensite (SIM) were inhibited at high strain rate; whereas, in the case of TWIP Ti alloy, the activity of stress-induced deformation twins (SIDTs) was promoted at high strain rate, which resulted in the intersection of different DTs and the formation of secondary DTs. The formation of the hierarchical DTs structures in TWIP Ti alloy not only effectively released the stress concentration to delay the crack initiation, but also remarkably increased the crack propagation path to enhance crack propagation resistance. Specifically, compared with TRIP effect, it seems as though TWIP effect was more efficient at accommodating the imposed high strain rate deformation. These findings enrich the understanding of TRIP and TWIP under impact deformation, and provide references for the design of metastable β titanium alloy with high impact toughness.

Impact toughness is a critical indicator to prevent catastrophic failure, especially at low service temperature. At present, most strategies to strengthen and toughen Ti alloys are proposed under the quasi-static tensile deformation condition. In fact, whether these strategies can be directly extended to improve impact toughness is still controversial due to the high loading rate and the existing of pre-notch during Charpy impact deformation condition. In this work, we found that, even though the yield strength and elongation of Ti–5Al–1V–1Sn–1Zr-0.8Mo alloy increase simultaneously with the decrease of test temperature under tensile deformation condition, the impact toughness still decreases gradually with the decreasing of deformation temperature under Charpy impact deformation condition. This phenomenon indicates that the successful strengthening and toughening strategies under quasi-static tensile deformation may fail under impact deformation. Finally, the reasons behind this phenomenon are explained based on the comparison of surface deformation morphologies under different deformation conditions, and the corresponding deformation mechanisms are established.

The in-beam positron emission tomography (ibPET) is dedicated to radiotherapy imaging of the heavy-ion medical machine (HIMM), which requires precise online measurement, as well as real-time signal processing capability of the electronics. In this paper, we present the implementation of real-time digital signal processing in the data acquisition unit (DAQU) for an ibPET system based on the photomultiplier tube (PMT) readout of lutetium-yttrium oxyorthosilicate (LYSO) scintillator crystals. We have designed 10-channel customized signal processing circuit on a high-performance FPGA, which supports 3 working modes (single event processing mode, self-calibration mode and raw ADC data mode), position calculation, crystal locating, event sorting, and etc. Moreover, the implementation of real-time corrections is capable of dealing with photon peak correction to 511 keV and crystal ID-based time correction. The implemented real-time ibPET system can achieve 46% data compression and beyond 1,000,000 events/sec/channel signal processing capabilities. A series of initial tests is conducted, and the results indicate that this design meets the application requirement on online processing.

A novel transformation induced plasticity (TRIP) Ti alloy with the composition of Ti-4.7Al-6.26Mo-2.85Cr was designed. The tensile and Charpy impact behaviors of the alloy with single beta and alpha + beta dual phase were comparably investigated. Compared to the single beta microstructure, the alpha + beta dual microstructure exhibited the higher yield strength (YS) and impact absorbed energy. This suggests the YS of the metastable beta Ti alloys has a significant influence on the impact toughness, i.e., the disadvantage of the low YS in single beta microstructure become more prominent in the impact deformation. Because the beta matrix in the alpha + beta dual microstructure was more stable than that in the single beta microstructure due to the elemental partitioning effect, the primary impact deformation mechanism changed from the stress induced martensite in the single beta microstructure to dislocation slip in the alpha + beta dual microstructure. Correspondingly, the cracking mechanism changed from beta/alpha" interface cracking to beta(retained)/alpha(lath) interface cracking. These findings provide guidance for the simultaneous improvement of YS and Charpy impact absorbed energy of TRIP Ti alloys by microstructural regulation.

In-beam PET is one of the imaging-based methods for monitoring carbon therapy by reconstruction of positron-emitters produced by incident particles. The accurate Monte Carlo simulation is necessary for range verification and therapeutic dose monitoring by means of the in-beam PET. GATE is capable of performing in-beam PET imaging but very few studies assess the accuracy of activity range measured from PET imaging with GATE simulated results. In this work, we present both experimental and GATE simulation studies of in-beam PET imaging of a phantom, which is irradiated by carbon ion beam, for range verification. The experiment data is acquired at Wuwei Heavy Ion Cancer Treatment Center in Gansu, China, with a dual-head plate PET prototype. The PET prototype consists of 2 panels, each arranged in 2 × 2 matrix. Each detector block is composed of 20 × 20 LYSO crystal array coupled with the position-sensitive photomultiplier tube (HAMAMATSU H8500). A homogeneous plastic phantom is irradiated with monoenergetic 131.05 MeV and 190.19 MeV 12 C ion pencil beams. The irradiation and full response of PET prototype are simulated with GATE macros. A novel mathematical model is established, which is capable of calculating and revealing the variation of the positron activity. Our focus is on the reconstructed activity ranges obtained by the experimental measurement and GATE MC prediction combined with the positron activity distribution calculation mathematical model. Results show that the reconstructed activity distribution of experimental data and GATE MC prediction are in good agreement. The measured and simulated 1D activity peak and falling edge positions are within 1.0 mm in all cases. The 20%, 50% and 80% PET peak positions predicted by GATE are close to measurements. These results indicated that it is feasible to assess the accuracy of activity range measured from the dual-head plate PET system with the modeled GATE hadron-PET simulation.

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.

A real-time digital time-stamp sorting algorithm used in the In-Beam positron emission tomography (In-Beam PET) is presented. The algorithm is operated in the field programmable gate array (FPGA) and a small amount of registers, MUX and memory cells are used. It is developed for sorting the data of annihilation event from front-end circuits, so as to identify the coincidence events efficiently in a large amount of data. In the In-Beam PET, each annihilation event is detected by the detector array and digitized by the analog to digital converter (ADC) in Data Acquisition Unit (DAQU), with a resolution of 14 bits and sampling rate of 50 MS/s. Test and preliminary operation have been implemented, it can perform a sorting operation under the event count rate up to 1 MHz per channel, and support four channels in total, count rate up to 4 MHz. The performance of this algorithm has been verified by pulse generator and 22Na radiation source, which can sort the events with chaotic order into chronological order completely. The application of this algorithm provides not only an efficient solution for selection of coincidence events, but also a design of electronic circuit with a small-scale structure.

为实现重离子治癌装置中γ-γ符合时间的高精度和高分辨率测量,设计实现了符合时间的测量系统,该系统主要由高速比较器构成的定时甄别电路和基于现场可编程逻辑阵列(FPGA)的时间-数字转换(TDC)电路构成.FPGA-TDC通过"粗"时间和"细"时间结合的方法实现精确的时间测量:"粗"时间测量采用二进制计数器实现,"细"时间测量基于片内缓冲器和寄存器阵列构成的级联延迟链实现.实测结果表明,该符合时间测量系统的本征时间间隔测量分辨好于276 ps(FWHM).构建了H8500耦合LYSO晶体阵列组成的测量系统,并对22Na 511 keVγ射线进行测试,结果表明时间测量精度优于1.12 ns(FWHM),且通过统计分析有效符合时间得到的晶体阵列位置映射散点图清晰.

To monitor the irradiation dose and position accurately delivered to patient during particle therapy in HeavyIon Cancer Therapy Device (HICTD) in Lanzhou, China, an In-Beam Positron Emission Tomography (PET) has been designed as a detection device to obtain time, energy and position information of gamma ray generated from the annihilation event, which is equipped at the beam line of HICTD. Sixteen detection blocks are adopted to construct a Dual-Head Planar-Type detector array in the In-Beam PET, and each detection block is composed of pixel detection elements. Data Acquisition Unit (DAQU) is employed as the processing module to process and digitize signals from detection blocks. Each DAQU faces a pair of detection blocks, there are eight DAQUs in total in this PET at present. A Central Processor Module (CPM) developed for the detector array is presented in this paper. CPM has two crucial functions: first it is as a hub to connect with all DAQUs through the optical links for data transfer and state control, second it is as a data process engine which collects data from different DAQUs and sorts the events into the chronological order for coincidence event discrimination, and then interfaces both control signals and event data to a host server through PCIe interface for image reconstruction. A novel parallel sorting algorithm has been explored and adopted in CPM, which can effectively sort the valid events detected by detection blocks. The key performance of the CPM has been evaluated in experiments. It can handle the events up to 16 million per second at least, which is capable of sorting and discriminating coincidence events efficiently.

研制了一种新型前端读出电路,用于重离子治癌装置中符合测量原型系统的研究和测试.电路主要包括能量链、时间链和数据处理单元.能量链由截止频率7 M Hz的抗混叠滤波器和模数转换器(ADC)组成,形成波形采样电路;时间链由高速比较器构成的定时甄别电路和时间数字转换器(TDC)组成;数据处理单元基于现场可编程门阵列(FPGA)设计实现.电路的线性度优于0.8％,噪声小于0.8 mV(RMS).配合LaBr3单晶体条测试,能量分辨为4.5％(FWHM),在与LYSO晶体阵列配合测试时,位置映射散点图清晰.该前端读出电路性能优于CAM AC系统,具有较好的实际应用前景.

Heavy-Ion Cancer Therapy Device (HICTD) developed by the Institute of Modern Physics of the Chinese Academy of Sciences is an advanced tumor radiotherapy device for nuclear medicine. The time of flight (TOF) positron emission tomography (PET) located on the beam line, called In-Beam TOF-PET, is a key detector in HICTD, which is employed for obtaining time, energy and position information of gamma ray to implement real-time image reconstruction during the treatment. A high performance readout electronics system has been designed for In-Beam TOF-PET. The Data Acquisition Unit (DAQU), a key device of it has been implemented. The signals from the In-Beam TOF-PET are acquired and processed by the DAQU, including 8 energy chains and 2 time chains. A field programmable gate array (FPGA) is adopted as a processor on board for implementing pulse area information extracting algorithm, FPGA-based TDC, and etc. The precision pulsar test indicates that the DAQU system has intrinsic influences on the energy resolution better than 5.5 parts per thousand (full width at the half-maximum, FWHM) and time resolution of 255 ps (FWHM). The Na-22 source test indicates that the overall system of the in-beam TOF-PET has an energy resolution of 14% FWHM at 511 keV and coincidence timing resolution better than 1.12 ns. The good position identification ability is indicated by the flood map, all the 484 crystals in one of LYSO crystal block detectors can be clearly distinguished.

In order to solve the contradiction between requirements of high sampling rate for acquiring accurate energy information of pulses and large amount of data to be processed timely, the method with an algorithm to correct errors caused by reducing the sampling rate is normally used in front-end read-out system, which is conductive to extract accurate energy information from digitized waveform of pulse. The functions and effects of algorithms, which mainly include polynomial fitting with different fitting times, double exponential function fitting under different sampling modes, and integral area algorithm, are analyzed and evaluated, and some meaningful results is presented in this paper. The algorithm described in the paper has been used preliminarily in a prototype system of Positron Emission Tomography (PET) for heavy-ion cancer therapy facility.

A position-sensitive CsI(Tl) crystal array coupled with the multi-anode position sensitive photomultiplier tube (PS-PMT), Hamamatsu H8500C, has been developed at the Institute of Modern Physics. An effective, fast, and economical readout circuit based on discretized positioning circuit (DPC) bridge was designed for the 64-channel multi-anode flat panel PSPMT. The horizontal and vertical position resolutions are 0.58 mm and 0.63 mm respectively for the 1.0 x 1.0 x 5.0 mm(3) CsI(Tl) array, and the horizontal and vertical position resolutions are 0.86 mm and 0.80 mm respectively for the 2.0 x 2.0 x 10.0 mm(3) CsI(Tl) array. These results show that the CsI(Tl) crystal array with low cost could be applied in the fields of medical imaging and high-resolution gamma camera. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC.

A multinucleon transfer and cluster-decay experiment, namely 9Be(13C,18O∗→14C+α)α, was performed at a beam energy of 65 MeV. Resonant states in 18O from 7 to 19 MeV, including some newly observed ones, are reconstructed with high resolution, based on the coincident detection of various combinations of the final fragments. The α-decay branching ratios for 14 states are extracted from both the invariant-mass and the missing-mass measurements. Angular correlation analysis was conducted for the 10.3-MeV (4+) state. The present work supports the existence of the positive-parity rotational band associated with the 14C+α molecular structure in 18O, but the negative-parity band members were not identified.1 MoreReceived 24 February 2019Revised 3 May 2019DOI:https://doi.org/10.1103/PhysRevC.99.064315©2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayCluster modelsNuclear structure & decaysTransfer reactionsProperties6 ≤ A ≤ 19Nuclear Physics

In the study of nuclear structure, the fast timing technique can be used to measure the lifetime of excited states. In the paper, we have developed a new fast timing system, which is made up of two LaBr3:Ce detectors and a set of waveform sampling system. The sampling system based on domino ring sampler version 4 chip (DRS4) can digitize and store the waveform information of detector signal, with a smaller volume and higher timing accuracy, and the waveform data are performed by means of digital waveform analysis methods. The coincidence time resolution of the fast timing system for two annihilation 511 keV y photon is 200ps (FWHM), the energy resolution is 3.5%@511 keV, and the energy linear response in the large dynamic range is perfect. Meanwhile, to verify the fast timing performance of the system, the Gd-152-2(1)(+)state form beta(+) decay of Eu-152 source is measured. The measured lifetime is 45.3(+/- 5.0)ps, very close to the value of the National Nuclear Data Center (NNDC: 46.2((+/- 3.9)ps). The experimental results indicate that the fast timing system is capable of measuring the lifetime of dozens of ps. Therefore, the system can be widely used in the research of the fast timing technology. (C) 2018 Korean Nuclear Society, Published by Elsevier Korea LLC.