In this paper, a non-gated carbon nanotube (CNT) field emission arrays with minimized screening effect was designed. A technique called aperture reduction was developed to overcome bottleneck effect ...in a non-gated CNT field emission arrays. In this technique, a sacrificial layer was deposited with a few steps and increased glancing angles.
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.
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.
In this paper, we introduce a new type of coverage for wireless sensor networks, called Directed Coverage (D-coverage). Basically, D-coverage is the coverage provided by a sensor network monitoring ...an area between two boundaries, through which the intruder attempts to penetrates the area. We also study how to measure the quality of D-coverage. Our first evaluation approach is a projection-based simple approach, while our second approach is a more comprehensive Markov chain based approach. Our evaluation approaches can accurately evaluate the quality and provide good guidelines for sensor network deployment and run-time repair.
The cross section of the process e+e-→π+D0D*- for center-of-mass energies from 4.05 to 4.60 GeV is measured precisely using data samples collected with the BESIII detector operating at the BEPCII ...storage ring. Two enhancements are clearly visible in the cross section around 4.23 and 4.40 GeV. Using several models to describe the dressed cross section yields stable parameters for the first enhancement, which has a mass of 4228.6±4.1±6.3 MeV/c2 and a width of 77.0±6.8±6.3 MeV, where the first uncertainties are statistical and the second ones are systematic. Our resonant mass is consistent with previous observations of the Y(4220) state and the theoretical prediction of a DD¯1(2420) molecule. This result is the first observation of Y(4220) associated with an open-charm final state. Fits with three resonance functions with additional Y(4260), Y(4320), Y(4360), ψ(4415), or a new resonance do not show significant contributions from either of these resonances. The second enhancement is not from a single known resonance. It could contain contributions from ψ(4415) and other resonances, and a detailed amplitude analysis is required to better understand this enhancement.
This paper presents micro-patterned carbon nanotube field emission arrays cathodes with an emitting unit area only 1mum in diameter. The fabrication process began with the deposition of a buffer ...layer of titanium-nitride on the silicon n type(100) substrate. Then a photo-resist overlay was patterned by conventional lithography technique to form 1mum circular aperture arrays, followed by depositing iron catalyst by electron beam deposition. Finally, the resist was removed, and carbon nanotubes grown by direct current plasma enhanced chemical vapor deposition (DC- PECVD). The field emission measurements showed a turn-on field as low as IV/mum, a current density of 90mA/cm 2 at a field of 17V/mum, and with a fluctuation less than 5.6 percent over a period of 3.5 hours at an average current of 550 muA..
Using our approach previously reported, we have fabricated relatively large area micro-gated-field emission arrays with carbon nanotube (CNT) grown on Mo tips. By redesigning the device and ...fabrication processes, the percentage of single CNTs increased to about 50-70% with a substantial improvement in leakage current between gate and cathode and gate interceptive current. The I-V measurement of a 11000 cell array at a gate-to cathode voltage of 92 V showed an anode current of 1.2 mA, corresponding a current density of 0.57 A/cm 2 , with a gate current only 3.3% of the anode current.
Carbon nanotube (CNT) field emission cathodes suffer from electric field screening effect arising from densely packed CNTS, resulting in a lower current density. To solve this problem, CNTS have to ...be separated in a proper manner. One way is to use electron beam lithographic method to produce single CNT arrays. Previously, we have fabricated gated field emission arrays with single CNT emitters by using conventional optical lithography. In this study, we extend our work to the fabrication of non-gated CNT arrays aiming at single CNT emitters.
In this work, we focus our attention on fabrications and characterizations of micro-gated-field emission arrays with CNTs grown on Mo tips (CNT FEAs). By further optimizing processing parameters, ...such as thickness of the sacrificial layer and height of Mo tips, the percentage of single CNTs increased to more than 50%. The I-V measurement of an array with 11000 cells at a gate voltage of 92 V showed an anode current of 1.2 mA, corresponding a current density of 0.57 A/cm 2 , with a gate current 3.3% of the anode current
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