Bakelite RPCs for Digital Hadron Calorimeter

This paper presents the test results of Bakelite RPCs using readout pads with an area of 1 cm×1 cm and 1-bit resolution per pad (binary readout). The results include noise rate, detection efficiency and pad multiplicity as well as comparisons of different surface treatments for Bakelite plates. Pad multiplicity’s dependence on surface resistivity at the readout side is also reported. This study shows Bakelite RPCs can be used as the active elements of digital hadron calorimeter.     

真空脱气处理对网眼多孔陶瓷力学性能的改善

采用有机泡沫浸渍工艺制备了碳化硅基网眼多孔陶瓷．研究了真空脱气处理对浆料流变特性和烧结体的力学性能及显微结构的影响．结果表明;脱气处理改善了浆料的流变特性,使浆料在有机泡沫体上的涂覆量增加和结构均匀性得到改善;压汞仪测试数据和ＳＥＭ观察表明脱气处理明显地消除了孔筋内的孔径为１００μｍ左右的大气孔;经脱气处理后,材料的抗弯强度从２．３４ＭＰａ提高到３１８ＭＰａ．脱气处理对网眼陶瓷强度的改善主要来自两方面的贡献：一是相对密度的增加,二是孔筋中大气孔的消除,但后者是最主要的贡献,这个结果与目前建立的开孔陶瓷泡沫的力学模型吻合得很好．     

网眼多孔陶瓷浸渍成型工艺的研究

采用一种具有三维网状结构和连通气孔的氨酯海绵作为骨架来制备网眼多孔陶瓷．采用一种亲水憎水平衡值（ＨＬＢ）＞１２的表面活性剂溶液对海绵体孔筋表面进行改性处理,改善了海绵与水基浆料之间的粘附性,增加了浆料涂覆量．研究了浆料固含量、有机泡沫体网眼大小、对辊间距和挤压次数对浆量涂覆量及结构均匀性的影响．结果表明：浆料固含量和对辊间距是影响涂覆量及结构均匀性的最主要因素．还发现网眼烧结体的相对密度与相对对辊间距具有很好的线性关系,这为预测和优化材料的渗透率及机械强度提供了一定的依据．     

Evaluation of an innovative system for improving readability of passive UHF RFID tags attached to reusable plastic containers

Radio frequency identification (RFID) is a contactless identification technology that has proven to work well in conjunction with reusable plastic containers (RPCs). The impact of this technology on returnable containers has been explored by several past studies. This study evaluates an innovative system for improving readability of passive UHF RFID tags in conjunction with RPCs. The system involves an energy transfer device (ETD), which when attached to the RPCs, passively transfers radio frequency signals to interior regions of a unitized load thereby improving the readability of all RFID tags attached to the RPCs. This study included an evaluation of the improvement in readability of tagged RPCs in a unitized load with forklift truck speed, product type and pallet pattern as the variables and with readability as the main control variable. It was observed that ETDs vastly improve the readability rates by nearly 97%. Results are also included in this paper describing the effects of the product type, pallet patterns and forklift truck speeds on the readability of tagged RPCs in a unitized load. Copyright © 2011 John Wiley & Sons, Ltd.     

碳化硅网眼多孔陶瓷的微波吸收特性

研究了碳化硅网眼陶瓷的微波吸收特性,发现它比实心材料的吸波性能几乎提高了两倍以上,这种吸波性能的改善主要来自网眼结构对电磁波产生的反射、散射及干涉作用引起的衰减.孔径大小、相对密度、试样厚度等因素对碳化硅网眼陶瓷的微波吸收性能的影响进行了讨论.本工作将为低成本、高性能结构型微波吸收材料的设计提供一条新途径.     

The control of slurry rheology in the processing of reticulated porous ceramics

In this work commercial polyurethane sponges with open porosity of approximately 13 pores per inch were chosen as the templates to produce the SiC RPCs. Effects of the rheological behavior of the slurry on the coating quality and the properties of SiC RPCs such as strength, density, microstructure, were investigated in detail. The coating quality was found to depend strongly on the slurry viscosity and this was improved dramatically extremely as the viscosity increased. The SiC RPCs displayed a remarkable increase in the flexural strength as the solids content increased. In addition, the increase of the polymer content had also a little contribution to the improvement of the strength The optimum solids content and polymer content were found to be 80 and 0.20 wt.%. This study shows that the control of slurry rheology is very important for the processing of RPCs.     

An Innovative Approach fro Improving the Reliability of Reticulated Porous Cermaics

An innovative approach has been developed to fabricate reticulated porous ceramics(RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates.In this approach,the coating process comprises of two stages.In the first stage,the thicker slurry was used to coat uniformly the sponge substrate.The green body was preheated to produce a reticulated perform with enough handling strength after the sponge was burned out.In the second stage,the thinner slurry was used to coat uniformly the perform .The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process.A few filled cells and cell faces occur in the fabrication and the struts were thickened.A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively.The result shows that the mechanical reliability of RPCs is improved by the innovative approach.This innovative approach is very simple and controlled easily,and will open up new technological applications for RPCs.     

Production of gas gaps for the Forward RPCs of the CMS experiment

The production of gas gaps, the core components of the Forward RPCs in the CMS experiment, has reached a mature stage of the production stream. A total of 360 gas gaps, equivalent to 120 RPCs, has been manufactured, tested for quality control, and delivered to CERN in Switzerland and to Pakistan, where the complete Forward RPCs are being assembled. In this paper, the layout of the gas gaps, the production procedures, facilities, and the selection process of the qualified gas gaps are presented.     

An Innovative Approach for Improving the Reliability of Reticulated Porous Ceramics

An innovative approach has been developed to fabricate reticulated porous ceramics (RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates. In this approach, the coating process comprises of two stages. In the first stage, the thicker slurry was used to coat: uniformly the sponge substrate. The green body was preheated to produce a reticulated preform with enough handling strength after the sponge was burned out. In the second stage, the thinner slurry was used to coat uniformly the preform. The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process. A few filled cells and cell faces occur in the fabrication and the struts were thickened. A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively. The result shows that the mechanical reliability of RPCs is improved by the innovative approach     

Low-temperature sintering of SiC reticulated porous ceramics with MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> additives as sintering aids

SiC reticulated porous ceramics (SiC RPCs) was fabricated with polymer replicas method by using MgO–Al₂O₃–SiO₂ additives as sintering aids at 1,000∼1,450 °C. The MgO–Al₂O₃–SiO₂ additives were from alumina, kaolin and Talc powders. By employing various experimental techniques, zeta potential, viscosity and rheological measurements, the dispersion of mixed powders (SiC, Al₂O₃, talc and kaolin) in aqueous media using silica sol as a binder was studied. The pH value of the optimum dispersion was found to be around pH 10 for the mixtures. The optimum condition of the slurry suitable for impregnating the polymeric sponge was obtained. At the same time, the influence of the sintering temperature and holding time on the properties of SiC RPCs was investigated. According to the properties of SiC RPCs, the optimal sintering temperature was chosen at 1,300 °C, which was lower than that with Al₂O₃–SiO₂ additives as sintering aids.     

一种能产生精确定时脉冲信号的PCI卡的设计

介绍了一种能够产生精确定时脉冲信号的PCI卡的设计。该卡产生的脉冲信号相对基准信号的定时精度可以达到500ps。该卡为PCI总线卡形式,采用了FPGA＋模拟延时芯片方式实现控制逻辑和定时。在FPGA内部设计的计时比较器为粗定时,模拟延时芯片为精密定时,最终在规定的精确时刻产生脉冲信号。     

An evaluation of the ability of RFID tags to withstand distribution of fresh produce in the RPC pooling system

This study focused on the ability of radio frequency identification (RFID) tags applied on reusable plastic containers (RPCs) to withstand repeated abuse due to physical distribution and storage environment related hazards. It also studied the effect of the chemical cleaning environments that RPCs are commonly exposed to in the pooling/rental systems commonly used to distribute fresh produce. RPCs are being successfully deployed in the US, Europe and Asia to ship fresh produce from growers to retailers. The increasing demand for traceability and tracking of fresh produce from ‘farm to fork’ requires these containers to be monitored and identified in the food supply chain, and RFID technology provides one of the solutions. This study compared eight commercially available RFID tags mounted on RPCs for use in fresh produce distribution and subjected them to repeated physical and climatic cycles representing the distribution and cleaning environments, and their effective ‘read’ capabilities were tested. Copyright © 2010 John Wiley & Sons, Ltd.     

Properties of a fast timing detector using an electron multiplier

A new timing detector for the time-of-flight method has been invented and successfully tested with heavy-ion beams. The detector consists of a thin foil and an electron multiplier. The best time resolution of 260 ps is obtained for ⁸¹Br. The time resolution is also studied in relation to the number of secondary electrons emitted from the foil.     

Millisecond pulsar observation system using acousto-opticspectrometer

We have developed a unique system using an acoustooptic spectrometer for precise timing of millisecond pulsars. This system can handle a signal of 50 MHz bandwidth with a frequency resolution of 200 kHz and a time resolution of 13 μs, and it can average 2²⁴ (7 h) pulses without any dead time     

A Picosecond Timing System

Subnanosecond resolution is possible in time interval measurement using the vernier principle. Such a timing system is described which is capable of resolving events occurring within a 12 ns interval to an accuracy better than 50 ps. Factors limiting resolution have been identified and their effect quantified.     

Autofocusing in medical ultrasound: the scaled covariance matrix algorithm

This work develops a class of ultrasound phase aberration correction/autofocusing algorithms that are based upon the properties of the covariance matrix of the channel signals for time-delay focused resolution/speckle cells. The scaled covariance matrix SCM algorithms are designed to blindly estimate and correct focusing timing errors due to thin layers of unanticipated fatty tissue located in the near field of the transducer array. An important aspect of the algorithm is that the scaling of the covariance matrix elements fundamentally establishes a channel independent phase reference relative to which the aberrant channel phases are estimated. The model development involved the combination of a rigorous mathematical analysis of the scattering of ultrasound in random scattering media and extensive statistical simulation studies with phase aberrations imposed upon both the transmit and received channel signals. Under the assumption of a near field aberration model, the statistical simulation analyses showed that the SCM algorithms in simulation are capable of accurately estimating relative time delay channel errors with RMS timing errors up to /spl sim/62 ns, with interchannel correlation lengths as short as 1.4 mm.     

The mass production and quality control of RPCs for the Daya Bay experiment

Resistive plate chambers will be used in the Daya Bay reactor neutrino experiment to help veto backgrounds created by cosmic-ray muons. The mass production of RPCs began in 2008 and by the end of 2009, 1600 RPCs (3500 m²) had been produced and tested. This paper describes the production and quality control procedures, and quality assurance using cosmic-ray testing.     

Systematic studies of scintillation detector with timing resolution of 10 ps for heavy ion beam

We have tested Time-Of-Flight detectors consisting of several combinations of scintillators and photomultiplier tubes for the identification of produced heavy ion beam. Timing resolution of 6.8 ps (RMS) is achieved with energy deposited of 150–160 MeV in the plastic scintillator, where ⁴⁰Ar beam is used as a primary beam at the total energies of 3.8 GeV. Our systematic studies suggest the importance of maximizing the number of photoelectrons, where the timing resolution seems to be scaled by the pulse height according to the characteristic function of the photomultiplier tube. In addition, scintillator with faster timing property seems to be also essential for better timing resolution.     

Large barium fluoride detectors

Big BaF₂ crystals of 1–2 1 volume and up to 15 cm thickness were investigated with respect to their application as gamma-ray detectors. In particular, we were interested in the light transmission in the UV region, and the energy and time resolution. We found that an energy resolution of ～ 12% (662 keV) and a time resolution of ～ 0.4 ns (⁶⁰Co, 300 keV threshold) can be obtained simultaneously. For these features, BaF₂ is superior to NaI or BGO in cases where good timing is essential. Gamma-rays and alpha particles can be clearly discriminated; as for the latter the fast component does not show up in the scintillation light.