A total of 25,6003-inch PMTs will be installed in Jiangmen Underground Neutrino Observatory(JUNO)to achieve more precise energy calibration and to extend the physics detection potential.Performances of all bare PMTs h...A total of 25,6003-inch PMTs will be installed in Jiangmen Underground Neutrino Observatory(JUNO)to achieve more precise energy calibration and to extend the physics detection potential.Performances of all bare PMTs have been characterized and these PMTs are being instrumented with the high voltage divider,underwater front-end cable,and connector.In this paper,we present a dedicated study on signal quality at different stages of the instrumentation.An optimized high voltage ratio was confirmed andfinalized which improved the PMT transit time spread by 25%.The signal charge was attenuated by 22.5%(13.0%)in the 10 m(5 m)cable and it required the addition of 45 V(23 V)to compensate for the loss of PMT gain.There was a 1%overshoot following the PMT signal and no sign of reflection in the connector.A group of 163-inch PMTs with the full instrumentation was installed in the JUNO prototype detector together with a few 8-inch and 20-inch PMTs,which showed good stability and demonstrated a photon detection system with multiple types of PMTs.展开更多
Graphene with different surface morphologies were fabricated on 8°-off-axis and on-axis 4H-SiC（0001） substrates by high-temperature thermal decompositions. Graphene grown on Si-terminated 8°-off-axis 4H-Si...Graphene with different surface morphologies were fabricated on 8°-off-axis and on-axis 4H-SiC（0001） substrates by high-temperature thermal decompositions. Graphene grown on Si-terminated 8°-off-axis 4H-SiC（0001） shows lower Hall mobility than the counterpart of on-axis SiC substrates. The terrace width is not responsible for the different electron mobility of graphene grown on different substrates, as the terrace width is much larger than the mean free path of the electrons. The electron mobility of graphene remains unchanged with an increasing terrace width on Si- terminated on-axis SiC. Interface scattering and short-range scattering are the main factors affecting the mobility of epitaxial graphene. After the optimization of the growth process, the Hall mobility of the graphene reaches 1770 cm^2/V.s at a carrier density of 9.8.×10^12 cm^-2. Wafer-size graphene was successfully achieved with an excellent double-layer thickness uniformity of 89.7% on a 3-inch SiC substrate.展开更多
文摘A total of 25,6003-inch PMTs will be installed in Jiangmen Underground Neutrino Observatory(JUNO)to achieve more precise energy calibration and to extend the physics detection potential.Performances of all bare PMTs have been characterized and these PMTs are being instrumented with the high voltage divider,underwater front-end cable,and connector.In this paper,we present a dedicated study on signal quality at different stages of the instrumentation.An optimized high voltage ratio was confirmed andfinalized which improved the PMT transit time spread by 25%.The signal charge was attenuated by 22.5%(13.0%)in the 10 m(5 m)cable and it required the addition of 45 V(23 V)to compensate for the loss of PMT gain.There was a 1%overshoot following the PMT signal and no sign of reflection in the connector.A group of 163-inch PMTs with the full instrumentation was installed in the JUNO prototype detector together with a few 8-inch and 20-inch PMTs,which showed good stability and demonstrated a photon detection system with multiple types of PMTs.
文摘Graphene with different surface morphologies were fabricated on 8°-off-axis and on-axis 4H-SiC（0001） substrates by high-temperature thermal decompositions. Graphene grown on Si-terminated 8°-off-axis 4H-SiC（0001） shows lower Hall mobility than the counterpart of on-axis SiC substrates. The terrace width is not responsible for the different electron mobility of graphene grown on different substrates, as the terrace width is much larger than the mean free path of the electrons. The electron mobility of graphene remains unchanged with an increasing terrace width on Si- terminated on-axis SiC. Interface scattering and short-range scattering are the main factors affecting the mobility of epitaxial graphene. After the optimization of the growth process, the Hall mobility of the graphene reaches 1770 cm^2/V.s at a carrier density of 9.8.×10^12 cm^-2. Wafer-size graphene was successfully achieved with an excellent double-layer thickness uniformity of 89.7% on a 3-inch SiC substrate.
