Ice-nucleating particles impact the severity of precipitations in West Texas

Ice-nucleating particles (INPs) influence the formation of ice crystals in clouds and many types of precipitation. However, our knowledge of the relationship between INPs and precipitation is still insufficient. This study was conducted to fill this gap by assessing precipitation properties and INP concentrations (nINP) from a total of 42 precipitation events observed in the Texas Panhandle region from June 2018 to July 2019. We used a cold-stage instrument called the West Texas Cryogenic Refrigerator Applied to Freezing Test system to estimate nINP through immersion freezing in our precipitation samples. A disdrometer was used to measure the precipitation intensity and size of precipitating particles during each precipitation event. The analysis of yearlong precipitation properties as well as INPs for the samples shed a light on the seasonal variation of the nINP values in West Texas. Furthermore, we characterized the bacteria speciation of the storm and ambient dust samples collected at a commercial feedlot in West Texas to identify potential biological sources of INPs in our precipitation samples. Overall, our results showed a positive correlation between nINP and intensity of precipitation with notably large hydrometeor sizes in storm precipitations. Amongst all observed precipitation types, the highest INPs were found in the snow samples, and hail/thunderstorm samples have the highest INPs at high temperature −5°C.

Mechanical feedback cooling assisted by optical cavity cooling of the thermal vibration of a microcantilever

This study describes a new two-step process to cool the thermal vibration of microcantilevers. The process combines active mechanical feedback cooling and optical cavity cooling. A micro-Fabry–Perot interferometer, built in-house, is set atop a microcantilever to measure the vibration amplitude, the high optical power density of which induces cavity cooling in the optical cavity. Using a two-step cooling procedure, the equivalent temperature of the thermal vibration of a microcantilever is lowered from room temperature to the theoretical cooling limit of 0.063 K, a much lower temperature than that achieved via simple cavity cooling (18 K), and then by mechanical feedback cooling (0.135 K) obtained for the same type of microcantilevers in previous studies. This experimental demonstration showcases a new type of cooling process of the amplitude of thermal vibration for micro-mechanical resonators to a lower temperature and does not need additional cooling using a conventional cryogenic refrigerator.

Cryogenic setup for MJ class laser targets

The cryogenic system for maintaining a target at a constant temperature in the range 5–25 K after shutting off the pulse tube (PT) cryogenic refrigerator is developed and tested. The temperature stability at the sample is ±2 mK for at least 20 hours. The cryogenic setup consists of cryostat, PT cryocooler, liquid helium vessel, helium gas supply, thermo-radiation shield, thermal resistance. The system provides 0.25 W of cooling power at the target. The appropriate thermal resistance should be used for different temperatures. The designed operation mode is 3 minutes off and 15 minutes on. The deactivation of PT cryocooler allows to achieve the target position stability of 1 micrometer or less during the X-ray characterization. The effect of neutron-shield was estimated using Monte-Carlo simulation.

Simulation and Evaluation on The Dynamic Performance of a Cryogenic Turbo-Based Reverse Brayton Refrigerator

In this study, a cryogenic turbo-based refrigerator, with high-speed foil gas bearing turboexpander and plate-fin heat exchanger, was presented. For the cooling process of a cryogenic refrigerator is long and complex, the efficient simulation of the dynamic performance is vital for its evaluation and operation. It is difficult to achieve this purpose. Because the cryogenic refrigerator will go through great temperature changes, resulting in dynamic performances of components going to complexity. In this article, the turboexpander was simulated using CFX, and the matching models with expansion works of consumption and utilization were unified and modified. With numerical calculation of heat exchanger, the dynamic simulation model of the refrigerator was improved via MATLAB code. The calculation method of the required input energy of the refrigerator in cooling processes was proposed based on the simulation and integration. The energy efficiency and economy cost of the refrigerator were evaluated under different operation modes. The refrigerator with a motor was more stable than the one with a blower. The refrigerator was tested under different conditions, the results of which agreed well with simulation data. The simulation method is efficient to serve practical applications, improve energy efficiency and reduce costs.