Search

Beam monitoring and evaluation are very important to boron neutron capture therapy (BNCT), and a variety of detectors have been developed for these applications. However, most of the detectors used in BNCT only have a small detection area, leading to the inconvenience of the full-scale 2-D measurement of the beam. Based on micromegas technology, we designed a neutron detector with large detection area and high counting rate. This detector has a detection area of 288 mm multiples 288 mm and can measure thermal, epithermal, and fast neutrons with different detector settings. The BNCT experiments demonstrated that this detector has a very good 2-D imaging performance for the thermal, epithermal, fast neutron and gamma components, a highest counting rate of 94 kHz/channel, and a good linearity response to the beam power. Additionally, the flux fraction of each component can be calculated based on the measurement results. The Am-Be neutron source experiment indicates that this detector has a spatial resolution of approximately 1.4 mm, meeting the requirements of applications in BNCT. It is evident that this micromegas-based neutron detector with a large area and high counting rate capability has great development prospects in BNCT beam monitoring and evaluation applications.

Back-streaming neutrons from the spallation target of the China Spallation Neutron Source (CSNS) that emit through the incoming proton channel were exploited to build a white neutron beam facility (the so-called Back-n white neutron source), which was completed in March 2018. The Back-n neutron beam is very intense, at approximately 2*10^7 n/cm^2/s at 55 m from the target, and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices. In addition, the excellent energy spectrum spanning from 0.5 eV to 200 MeV, and a good time resolution related to the time-of-flight measurements make it a typical white neutron source for nuclear data measurements; its overall performance is among that of the best white neutron sources in the world. Equipped with advanced spectrometers, detectors, and application utilities, the Back-n facility can serve wide applications, with a focus on neutron-induced cross-section measurements. This article presents an overview of the neutron beam characteristics, the experimental setups, and the ongoing applications at Back-n., Comment: 11 pages, 9 figures

Differential and angle-integrated cross sections for the $^{10}$B($n, {\alpha}$)$^{7}$Li, $^{10}$B($n, {\alpha}$$_{0}$)$^{7}$Li and $^{10}$B($n, {\alpha}$$_{1}$)$^{7}$Li$^{*}$ reactions have been measured at CSNS Back-n white neutron source. Two enriched (90%) $^{10}$B samples 5.0 cm in diameter and ~85.0 ${\mu}$g/cm$^{2}$ in thickness each with an aluminum backing were prepared, and back-to-back mounted at the sample holder. The charged particles were detected using the silicon-detector array of the Light-charged Particle Detector Array (LPDA) system. The neutron energy E$_{n}$ was determined by TOF (time-of-flight) method, and the valid ${\alpha}$ events were extracted from the E$_{n}$-Amplitude two-dimensional spectrum. With 15 silicon detectors, the differential cross sections of ${\alpha}$-particles were measured from 19.2{\deg} to 160.8{\deg}. Fitted with the Legendre polynomial series, the ($n, {\alpha}$) cross sections were obtained through integration. The absolute cross sections were normalized using the standard cross sections of the $^{10}$B($n, {\alpha}$)$^{7}$Li reaction in the 0.3 - 0.5 MeV neutron energy region. The measurement neutron energy range for the $^{10}$B($n, {\alpha}$)$^{7}$Li reaction is 1.0 eV $\le$ En < 2.5 MeV (67 energy points), and for the $^{10}$B($n, {\alpha}$$_{0}$)$^{7}$Li and $^{10}$B($n, {\alpha}$$_{1}$)$^{7}$Li$^{*}$ reactions is 1.0 eV $\le$ En < 1.0 MeV (59 energy points). The present results have been analyzed by the resonance reaction mechanism and the level structure of the $^{11}$B compound system, and compared with existing measurements and evaluations., Comment: 19 pages, 34 figures, to be published in Chinese Physics C

The Back-n white neutron beam line, which uses back-streaming white neutrons from the spallation target of the China Spallation Neutron Source, is used for nuclear data measurements. A Micromegas-based neutron detector with two variants was specially developed to measure the beam spot distribution for this beam line. In this article, the design, fabrication, and characterization of the detector are described. The results of the detector performance tests are presented, which include the relative electron transparency, the gain and the gain uniformity, and the neutron beam profile reconstruction capability. The result of the first measurement of the Back-n neutron beam spot distribution is also presented., Comment: 31 pages, 18 figures

The time-of-flight (TOF) system in the Compressed Baryonic Matter (CBM) experiment is composed of super modules based on multi-gap Resistive Plate Chambers (MRPC) for high-denseness, high-resolution time measurement. In order to evaluate the quality of detectors during the mass production, a distributed data readout system is developed to meet with the high data rate of 6.4Gbps, and a related data acquisition (DAQ) software is implemented under Linux operating system to test and verify the feasibility of the distributed data readout method. In this paper, the DAQ software is focused on data collection, event building, status monitoring and system controlling. Laboratory tests confirmed the function of the DAQ software and show that the overall data transfer rate of a single data transmission path can reach up to about 550Mbps which already meet the demand., Comment: Real Time 2018

A super module assembled with MRPC detectors is a component of TOF (Time of Flight) system for the Compressed Baryonic Matter (CBM) experiment. Before the super modules are applied to CBM-TOF, their quality needs to be evaluated. The readout electronics is confronted with a tremendous challenge of transmitting data at the maximal speed of 6 Gbps. In this paper, the readout method for CBM-TOF super module quality evaluation is presented. A parallel architecture based on the Gigabit Ethernet is designed to meet the requirement for data transmission rate. First, the data is sent from the front-end electronics to four readout module groups via optical fibers at the maximal rate of 1.5 Gbps per fiber. Next, the data are further distributed to sixteen parallel daughter readout models so that the maximal data throughput of each daughter readout module is 375 Mbps, within its capacity of 550 Mbps. Finally, the readout daughter modules send data to the data acquisition (DAQ) software through standard Gigabit Ethernet. The proposed readout method has the advantage of good scalability, so it can meet different requirements for variable data rate. The preliminary test result shows that each of four parallel readout groups can transmit data at the speed of 1.6 Gbps, which indicates that the overall readout system can meet the requirement for the maximal data-transmission speed of 6 Gbps.

The Compressed Baryonic Matter (CBM) experiment will investigate the quantum chromodynamics (QCD) phase diagram at high net baryon densities and moderate temperatures. CBM Time of Flight (TOF) system is composed of super modules containing high performance Multi-gap Resistive Plate Chambers (MRPCs). During the mass production, each super module assembled with MRPCs needs quality evaluation, which includes time measurement and data readout. Read out electronics encounter the challenge of reading data from a super module at a speed of about 6 Gbps. In this paper, a read out method based on Peripheral Component Interconnect Express (PCIe) over optical fiber is proposed for CBM-TOF super module quality evaluation. The digitized data from super module will be concentrated at the front-end electronics, and then be transmitted to a PCIe switch module (PSM) over optical fiber using PCIe protocol. The PSM is directly plugged into the motherboard via gold fingers at the backend data acquisition server. With this readout method, a high-speed transmission rate can be reached. Furthermore, a PSM can receives data from several super modules simultaneously, which is important to improve the evaluation efficiency. This readout method simplifies the architecture of readout electronics and supports long distance transmission between frontend and backend.

In this paper, we consider joint drift rate control and impulse control for a stochastic inventory system under long-run average cost criterion. Assuming the inventory level must be nonnegative, we prove that a $\{(0,q^{\star},Q^{\star},S^{\star}),\{\mu^{\star}(x): x\in[0, S^{\star}]\}\}$ policy is an optimal joint control policy, where the impulse control follows the control band policy $(0,q^{\star},Q^{\star},S^{\star})$, that brings the inventory level up to $q^{\star}$ once it drops to $0$ and brings it down to $Q^{\star}$ once it rises to $S^{\star}$, and the drift rate only depends on the current inventory level and is given by function $\mu^{\star}(x)$ for the inventory level $x\in[0,S^{\star}]$. The optimality of the $\{(0,q^{\star},Q^{\star},S^{\star}),\{\mu^{\star}(x): x\in[0,S^{\star}]\}\}$ policy is proven by using a lower bound approach, in which a critical step is to prove the existence and uniqueness of optimal policy parameters. To prove the existence and uniqueness, we develop a novel analytical method to solve a free boundary problem consisting of an ordinary differential equation (ODE) and several free boundary conditions. Furthermore, we find that the optimal drift rate $\mu^{\star}(x)$ is firstly increasing and then decreasing as $x$ increases from $0$ to $S^{\star}$ with a turnover point between $Q^{\star}$ and $S^{\star}$., Comment: 30 pages, 1 figure

BaF2 (Barium fluoride) detector is one of the experiment facilities at the under construction CSNS-WNS (White Neutron Source at China Spallation Neutron Source). It is designed for precisely measuring (n,gamma) cross section with total 92 crystal elements and completely 4 pi steradian coverage. In this proposal for readout electronics, waveform digitizing technique with 1GSps sampling rate and 12-bit resolution is adopted to precisely capture the detector signal. To solve the problem of massive data readout and processing, the readout electronics system is designed into a distributed architecture with 4 PXIe crates. The digitized detector's signal is concentrated to PXIe crate controller through PCIe bus on backplane and transmitted to data acquisition system over Gigabit Ethernet in parallel. Besides, clock and trigger can be fanned out synchronously to each electronic channel over a high-precision distributing network. Test results showed that the prototype of the readout electronics system achieved good performance and cooperated well., Comment: 7 pages, 12 figures, 1 table

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter., Comment: 15 pages, 11 figures. Published in European Physical Journal A

The upgrade of the current BESIII Endcap TOF (ETOF) is carried out with the Multi-gap Resistive Plate Chamber (MRPC) technology. The installation of the new ETOF has been finished in October 2015. The first results of the MRPCs commissioning at BESIII are reported in this paper., Comment: 7 pages,8 figures,conference

The Beijing Spectrometer III (BESIII) endcap Time-Of-Filght (ETOF) was proposed to upgrade with Multigap Resistive Plate Chamber (MRPC) technology to substitute the current ETOF of scintillator+PMT for extending time resolutin better than 80 ps and enhance the particle identification capability to satisfy the higher precision requirement of physics. The ETOF system including MRPC modules, front end electronics (FEE), CLOCK module, fast control boards and time to digital modules (TDIG), has been designed, constructed and done some experimental tests seperately. Aiming at examining the quality of entire ETOF system and training the operation of all participated parts, a cosmic ray test system was built at the laboratory and underwent about three months to guarantee performance. In this paper the results will be presented indicating that the entire ETOF system works well and satisfies the requirements of the upgrade., Comment: 7 pages,8 figures, conference

A new fanning topology is proposed to precisely fan out fast control signals in the Beijing Spectrometer (BES III) end-cap time-of-flight (ETOF) electronics. However, uncertainty in transfer latency is introduced by the new fanning channel, which will degrade the precision of fast control. In this paper, latency uncertainty elimination for the BESIII ETOF upgrade is introduced. The latency uncertainty is determined by a Time-Digital-Converter (TDC) embedded in a Field-Programmable Gate Array (FPGA) and is eliminated by re-capturing at synchronous and determinate time. Compared with the existing method of Barrel-cap TOF (BTOF), it has advantages of flexible structure, easy calibration and good adaptability. Field tests on the BES III ETOF system show that this method effectively eliminates transfer latency uncertainty., Comment: 6pages, 12 figures, This paper is to be published in Chinese Physics C

aF2 (Barium Fluoride) detector array is designed for the measurement of (n,{\gamma}) cross section precisely at CSNS-WNS (white neutron source at China Spallation Neutron Source). It is a 4{\pi}solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from BaF2 detector, pulse shape discrimination methodology is used, which is supported by waveform digitization technique. There are total 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, the clock prototype for BaF2 readout electronics at CSNS-WNS is introduced. It is based on PXIe platform and has a twin-stage tree topology. In the first stage, clock is distributed from the tree root to each PXIe crate synchronously through coaxial cable over long distance, while in the second stage, clock is further distributed to each electronic module through PXIe dedicated differential star bus. With the help of this topology, each tree node can fan out up to 20 clocks with 3U size. Test result shows the clock jitter is less than 20ps, which can meet the requirement of BaF2 readout electronics. Besides, this clock system has advantages of high density, simplicity, scalability and cost saving, which makes it can be used in other applications of clock distributing preciously., Comment: 5 pages, 6 figures

In order to improve the particle identification capability of the Beijing Spectrometer III (BESIII),t is proposed to upgrade the current endcap time-of-flight (ETOF) detector with multi-gap resistive plate chamber (MRPC) technology. Aiming at extending ETOF overall time resolution better than 100ps, the whole system including MRPC detectors, new-designed Front End Electronics (FEE), CLOCK module, fast control boards and time to digital modules (TDIG), was built up and operated online 3 months under the cosmic ray. The main purposes of cosmic ray test are checking the detectors' construction quality, testing the joint operation of all instruments and guaranteeing the performance of the system. The results imply MRPC time resolution better than 100$ps$, efficiency is about 98$\%$ and the noise rate of strip is lower than 1$Hz/$($scm^{2}$) at normal threshold range, the details are discussed and analyzed specifically in this paper. The test indicates that the whole ETOF system would work well and satisfy the requirements of upgrade.

Time measurement plays a crucial rule for the purpose of particle identification in high energy physical experiments. With the upgrading of physical goal and the developing of electronics, modern time measurement system meets the requirement of excellent resolution specification as well as high integrity. Due to Field Programmable Gate Array (FPGA), FPGA time-to-digital converter (TDC) becomes one of mature and prominent time measurement methods in recent years. For correcting time-walk effect caused by leading timing, time-over-threshold (TOT) measurement should be added in the FPGA TDC. TOT can be obtained by measuring the interval time of signal leading and trailing edge. Unfortunately, a traditional TDC can recognize only one kind of signal edge, the leading or the trailing. Generally, to measure the interval, two TDC channels can be used at the same time, one for leading, the other for trailing. However, this method will increase the amount of used FPGA resource and reduce the TDC's integrity unavoidably. This paper presents one method of TOT measurement implemented in a Xilinx Virtex-5 FPGA. In this method, TOT measure can be achieved in only one TDC input channel. The consumed resources and time resolution can both be guaranteed. Test shows that this TDC can achieve resolution better than 15 ps for leading edge measurement and 37 ps for TOT measurement. Furthermore, the TDC measuring dead time is about 2 clock cycles, which makes it be good for applications of higher physical event rate, Comment: 5 pages,9 figures