Evaluation of flux expulsion and flux trapping sensitivity of srf cavities fabricated from cold work Nb sheet with successive heat treatment

The main source of RF losses leading to lower quality factor of superconducting radio-frequency cavities is due to the residual magnetic flux trapped during cool-down. The loss due to flux trapping is more pronounced for cavities subjected to impurities doping. The flux trapping and its sensitivity to rf losses are related to several intrinsic and extrinsic phenomena. To elucidate the effect of re-crystallization by high temperature heat treatment on the flux trapping sensitivity, we have fabricated two 1.3 GHz single cell cavities from cold-worked Nb sheets and compared with cavities made from standard fine-grain Nb. Flux expulsion ratio and flux trapping sensitivity were measured after successive high temperature heat treatments. The cavity made from cold worked Nb showed better flux expulsion after 800 C/3h heat treatments and similar behavior when heat treated with additional 900 C/3h and 1000 C/3h. In this contribution, we present the summary of flux expulsion, trapping sensitivity, and RF results.Comment: 21st International Conference on Radio-Frequency Superconductivity (SRF 2023

Influence of fluid temperature gradient on the flow within the shaft gap of a PLR pump

In nuclear power plants the primary-loop recirculation (PLR) pump circulates the high temperature/high-pressure coolant in order to remove the thermal energy generated within the reactor. The pump is sealed using the cold purge flow in the shaft seal gap between the rotating shaft and stationary casing, where different forms of Taylor–Couette flow instabilities develop. Due to the temperature difference between the hot recirculating water and the cold purge water (of order of 200 °C), the flow instabilities in the gap cause temperature fluctuations, which can lead to shaft or casing thermal fatigue cracks. The present work numerically investigated the influence of temperature difference and rotating speed on the structure and dynamics of the Taylor–Couette flow instabilities. The CFD solver used in this study was extensively validated against the experimental data published in the open literature. Influence of temperature difference on the fluid dynamics of Taylor vortices was investigated in this study. With large temperature difference, the structure of the Taylor vortices is greatly stretched at the interface region between the annulus gap and the lower recirculating cavity. Higher temperature difference and rotating speed induce lower fluctuating frequency and smaller circumferential wave number of Taylor vortices. However, the azimuthal wave speed remains unchanged with all the cases tested. The predicted axial location of the maximum temperature fluctuation on the shaft is in a good agreement with the experimental data, identifying the region potentially affected by the thermal fatigue. The physical understandings of such flow instabilities presented in this paper would be useful for future PLR pump design optimization

Quench Detection in a Superconducting Radio Frequency Cavity with Combine Temperature and Magnetic Field Mapping

Local dissipation of RF power in superconducting radio frequency cavities create so called hot spots, primary precursors of cavity quench driven by either thermal or magnetic instability. These hot spots are detected by a temperature mapping system, and a large increase in temperature on the outer surface is detected during cavity quench events. Here, we have used combined magnetic and temperature mapping systems using anisotropic magnetoresistance (AMR) sensors and carbon resisters to locate the hot spots and areas with high trapped flux on a 3.0 GHz single-cell Nb cavity during the RF tests at 2.0 K. The quench location and hot spots were detected near the equator when the residual magnetic field in the Dewar is kept < 1 mG. The hot spots and quench locations moved when the magnetic field is trapped locally, as detected by T-mapping system. No significant dynamics of trapped flux is detected by AMR sensors, however, change in magnetic flux during cavity quench is detected by a flux gate magnetometer, close to the quench location. The result provides the direct evidence of hot spots and quench events due to localized trapped vortices.Comment: 21st International Conference on Radio-Frequency Superconductivity (SRF 2023

Effect of biochar and plastic mulch on growth, yield, and yield attributing characteristics of spring maize (Zea mays L.)

Spring maize is an important crop to meet the growing demand for maize. Moisture stress is an important yield limiting factor during the dry spring period. Biochar and plastic mulch help in soil moisture conservation and might contribute to the growth and yield of maize. A field experiment was conducted to evaluate the effects of biochar application and plastic mulch on growth, yield, and yield attributing characteristics of spring maize (Zea mays L.) in a sandy loam soil at Rampur, Chitwan, Nepal in 2018. The experiment was laid out in a split-plot design (SPD) with three replications. The Main plots were allocated to the mulching (mulching, and no mulching) while the Subplot was to the biochar rates of 0 t/ha, 5 t/ha, 15 t/ha, and 25 t/ha. There were twenty-four plots of each plot size 4.8 × 1.5 m2. The grounded biochar passed through a 1 mm sieve and was applied in the well-prepared plots two weeks before seed sowing. The maize seeds were sown at 60 cm row to row and 25 cm plant to plant distance. There were no significant effects due to both factors on maize seed emergence, plant height, number of leaves per plant, leaf area index, root length, dry matter content, stover yield, and yield attributes. But the yield was significantly influenced by their interactions. Significantly highest grain yield (2.58 t/ha) was obtained from 25 t/ha with plastic mulch followed by plastic mulch with 15 t/ha biochar (2.06 t/ha) and the least was recorded from control plots (1.19 t/ha). From the result, it can be concluded that the application of a higher biochar rate of 25 t/ha with plastic mulch contributes to a higher yield of spring maize

Productivity and Profitability Assessment of Drought Tolerant Rice Cultivars under Different Crop Management Practices in Central Terai of Nepal

Reduction in productivity has led to lower profitability of rice production in Nepal. Proper selections of resource conservation technologies and drought tolerant cultivars are being potential strategies determining productivity of rice in drought prone areas. Thus, a field experiment was accomplished in central-terai of Nepal during 2014 to assess the productivity and profitability of drought tolerant rice cultivars under different crop management practices. The experiment was carried out in strip-plot design with three replications consisting four drought tolerant rice cultivars and three crop management practices. The analyzed data revealed that SRI (System of Rice Intensification) produced significantly higher grain yield (5.28 t ha-1) than other management practices. The straw yield of SRI (5.12 t ha-1) was also significantly higher than other management practices. The cultivars had no influence on grain yield, but the straw yield was significantly influenced by cultivars, with the highest straw yield in Sukkha-3 (5.21 t ha-1). Similarly, SRI management practice also had significantly higher gross returns (NRs. 144652 ha-1), net return (NRs. 56647 ha-1) and B:C ratio (1.64:1). Thus, SRI management practice can be adopted as adaptation approach for obtaining higher productivity and profitability in central terai and similar agro-climatic regions of Nepal

CFD investigation of a core-mounted-target-type thrust reverser, Part 2: reverser deployed configuration

CMTTTR design was proposed by NASA in the second half of the 90's. NASA carried out several experiments at static conditions, and their acquired results suggested that the performance characteristics of the CMTTTR design falls short to comply with the mandatory TR performance criteria, and were therefore regarded as an infeasible design. However, the authors of this paper believe that the results presented by NASA for CMTTTR design require further exploration to facilitate the complete understanding of its true performance potential. This Part2 paper is a continuation from Part1and presents a comprehensive three-dimensional (CFD) analyses of the CMTTTR in deployed configuration; the analyses at forward flight conditions will be covered in Part 3. The key objectives of this paper are: first, to validate the acquired CFD results with the experimental data provided by NASA: this is achieved by measuring the static pressure values on various surfaces of the deployed CMTTTR model. The second objective is to estimate the performance characteristics of the CMTTTR design and corroborate the results with experimental data. The third objective is to estimate the Pressure Thrust (i.e. axial thrust generated due to the pressure difference across various reverser surfaces) and discuss its significance for formulating the performance of any thrust reverser design. The fourth objective is to investigate the influence of kicker plate installation on overall TR performance. The fifth and final objective is to examine and discuss the overall flow physics associated with the thrust reverser under deployed configuration