Noise temperature distribution of superconducting hot electron bolometer mixers

We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.

Temperature-dependent structural,morphological and optical properties of chemical bath-deposited CdS films

Cadmium sulfide(CdS) films were grown on top of the fluorine-doped tin oxide(FTO) coated glass substrates at four different bath temperatures by chemical bath deposition(CBD) technique.X-ray diffraction(XRD),ultraviolet-visible(UV-Vis) spectrometry,energy-dispersive X-ray spectroscopy(EDX),field emission scanning electron microscope(FESEM),photoluminescence(PL)and Fourier-transform infrared(FTIR) analyses were employed to examine the morphological and optical properties of deposited films.XRD studies confirmed the cubic crystalline nature of the deposited films which improved with increase in deposition temperature,and EDX along with FESEM study showed that the films were smooth and uniform with appropriate chemical composition.Band-gap values of the CBD CdS films calculated by UV-Vis spectrometry were found to be in the range of2.32-2.39 eV.A strong blue band and a weak green band were observed in PL emission spectra.C-S,Cd-S and SC-N vibrations were found by FTIR spectral analysis.

Determination of 16 Species of OCPs in Water by Liquid-liquid Extraction-GC

[Objective] The research aimed to study the determination of 16 kinds of OCPs in water by liquid-liquid extraction -GC. [Method] The new method for determining 16 kinds of OCPs in water by liquid-liquid extraction -GC was established, and the influencing factors such as nitrogen pressure and water bath temperature were discussed. [ Result] Detection limit of the method was from 3.2 to 14.1 ng/L, the relative standard deviation was between 4.0% and 9.6%, and the average recovery ranged from 80.8% to 106.0%. By optimizing nitrogen pressure and water bath temperature in the sample pretreatment process, when nitrogen pressure was ＋0.087 kPa, and water bath temperature was ±36 ℃, recovery effect of this method was better. [ Conclusion] The determination method had accurate qualitative and quantitative results, and met detection requirement of 16 kinds of OCPs in water.