150 research outputs found
Multi-metallic conduction cooled superconducting radio-frequency cavity with high thermal stability
Superconducting radio-frequency cavities are commonly used in modern particle
accelerators for applied and fundamental research. Such cavities are typically
made of high-purity, bulk Nb and are cooled by a liquid helium bath at a
temperature of ~2 K. The size, cost and complexity of operating a particle
accelerator with a liquid helium refrigerator makes the current cavity
technology not favorable for use in industrial-type accelerators. We developed
a multi-metallic 1.495~GHz elliptical cavity conductively cooled by a
cryocooler. The cavity has a ~2 m thick layer of NbSn on the inner
surface, exposed to the rf field, deposited on a ~3 mm thick bulk Nb shell and
a bulk Cu shell, of thickness mm deposited on the outer surface
by electroplating. A bolt-on Cu plate 1.27 cm thick was used to thermally
connect the cavity equator to the second stage of a Gifford-McMahon cryocooler
with a nominal capacity of 2 W at 4.2 K. The cavity was tested initially in
liquid helium at 4.3 K and reached a peak surface magnetic field of ~36 mT with
a quality factor of . The cavity cooled by the crycooler achieved
a peak surface magnetic field of ~29 mT, equivalent to an accelerating gradient
of 6.5 MV/m, and it was able to operate in continuous-wave with as high as 5 W
dissipation in the cavity for 1 h without any thermal breakdown. This result
represents a paradigm shift in the technology of superconducting accelerator
cavities
Let us conserve and exchange seeds: celebrating traditional crop diversity of the Nepali lowlands
A seed fair is an activity to create awareness about and appreciate local crop diversity, exchange seed and related knowledge, and celebrate farmersā efforts to conserve agrobiodiversity. It takes considerable time and effort to organize a seed fair. This brief describes the seed fair organized at the Agyauli Community Seedbank, Nawalparasi in the southern region of Nepal.
About 30 members of 10 community seedbanks from the terai (the southern lowland) region of Nepal came together for this. Apart from exchanging seeds of traditional crop varieties, they also shared stories about the socio-cultural, religious, spiritual, nutritional and medicinal values of their varieties. The recent formal registration of the Community Seed Banks Association of Nepal (CSBAN) was also celebrated
Preservation of the High Quality Factor and Accelerating Gradient of Nb3Sn-coated Cavity During Pair Assembly
Two CEBAF 5-cell accelerator cavities have been coated with Nb3Sn film using
the vapor diffusion technique. One cavity was coated in the Jefferson Lab Nb3Sn
cavity coating system, and the other in the Fermilab Nb3Sn coating system. Both
cavities were measured at 4 K and 2 K in the vertical dewar test in each lab
and then assembled into a cavity pair at Jefferson Lab. Previous attempts to
assemble Nb3Sn cavities into a cavity pair degraded the superconducting
properties of Nb3Sn-coated cavities. This contribution discusses the efforts to
identify and mitigate the pair assembly challenges and will present the results
of the vertical tests before and after pair assembly. Notably, one of the
cavities reached the highest gradient above 80 mT in the vertical test after
the pair assembly.Comment: 21st Intl Conf Radio Frequency Superconductivity (SRF 2023
An Open Data and Citizen Science Approach to Building Resilience to Natural Hazards in a Data-Scarce Remote Mountainous Part of Nepal
The citizen science approach has gained momentum in recent years. It can enable both experts and citizen scientists to co-create new knowledge. Better understanding of local environmental, social, and geographical contexts can help in designing appropriate plans for sustainable development. However, a lack of geospatial data, especially in the context of developing countries, often precludes context-specific development planning. This study therefore tests an innovative approach of volunteer citizen science and an open mapping platform to build resilience to natural hazards in the remote mountainous parts of western Nepal. In this study, citizen scientists and mapping experts jointly mapped two districts of Nepal (Bajhang and Bajura) using the OpenStreetMap (OSM) platform. Remote mapping based on satellite imagery, capacity building, and mobilization of citizen scientists was performed to collect the data. These data were then uploaded to OSM and later retrieved in ArcGIS to produce a usable map that could be exploited as a reference resource for evidence-based decision-making. The collected data are freely accessible to community members as well as government and humanitarian actors, and can be used for development planning and risk reduction. By piloting in two communities of western Nepal, we found that using open data platforms for collecting and analyzing location-based data has a mutual benefit for researchers and communities. Such data could be vital in understanding the local landscape, environmental risk, and distribution of resources. Furthermore, they enable both researchers and local people to transfer technical knowledge, collect location-specific data, and use them for better decision-making
Surface Properties and RF Performance of Vapor Diffused NbāSn On NB After Sequential Anneals Below 1000 Ā°C
NbāSn is a next-generation superconducting material that can be used for future superconducting radiofrequency (SRF) accelerator cavities, promising better performance, cost reduction, and higher operating temperature than Nb. The Sn vapor diffusion method is currently the most preferred and successful technique to coat niobium cavities with NbāSn. Among post-coating treatments to optimize the coating quality, higher temperature annealing without Sn is known to degrade NbāSn because of Sn loss. We have investigated NbāSn/Nb samples briefly annealed at 800-1000 Ā°C, for 10 and 20 minutes to potentially improve the surface to enhance the performance of NbāSn-coated cavities. Following the sample studies, a coated single-cell cavity was sequentially annealed at 900 Ā°C and tested its performance each time, improving the cavityās quality factor relatively. This paper summarizes the sample studies and discusses the RF test results from sequentially annealed SRF NbāSn/Nb cavity
Lower Temperature Annealing of Vapor Diffused Nb\u3csub\u3e3\u3c/sub\u3eSn for Accelerator Cavities
Nb3Sn is a next-generation superconducting material for the accelerator cavities with higher critical temperature and superheating field, both twice compared to Nb. It promises superior performance and higher operating temperature than Nb, resulting in significant cost reduction. So far, the Sn vapor diffusion method is the most preferred and successful technique to coat niobium cavities with Nb3Sn. Although several post-coating techniques (chemical, electrochemical, mechanical) have been explored to improve the surface quality of the coated surface, an effective process has yet to be found. Since there are only a few studies on the post-coating heat treatment at lower temperatures, we annealed Nb3Sn-coated samples at 800 C - 1000 C to study the effect of heat treatments on surface properties, primarily aimed at removing surface Sn residues. This paper discusses the systematic surface analysis of coated samples after annealing at temperatures between 850 C and 950 C
A Multi-Layered SRF Cavity for Conduction Cooling Applications
Industrial application of SRF technology would favor the use of cryocoolers to conductively cool SRF cavities for particle accelerators, operating at or above 4.3 K. In order to achieve a lower surface resistance than Nb at 4.3 K, a superconductor with higher critical temperature should be used, whereas a metal with higher thermal conductivity than Nb should be used to conduct the heat to the cryocoolers. A standard 1.5 GHz bulk Nb single-cell cavity has been coated with a ~2 Āµm thick layer of NbāSn on the inner surface and with a 5 mm thick Cu layer on the outer surface for conduction cooled applications. The cavity performance has been measured at 4.3 K and 2.0 K in liquid He. The cavity reached a peak surface magnetic field of ~40 mT with a quality factor of 6Ć10ā¹ and 3.5Ć10ā¹ at 4.3 K, before and after applying the thick Cu layer, respectively
A novel approach for implementing community seed banks in the mountain area of Nepal
Community seed bank (CSB) is one of the approaches successfully applied in Nepal and globally for conservation and use of local crop diversity for food and agriculture. However, there are only a few success examples of CSBs in high mountain areas of Nepal, particularly focusing on traditional underutilized crops. This chapter aims to present the modality and experiences of implementing community seed banks in mountain districts, namely, Humla, Jumla, Lamjung and Dolakha, by the UNEP GEF Local Crop Project (LCP) jointly implemented by Bioversity International, NAGRC, DoA and LI-BIRD. The project was implemented in 2014 in Nepal for providing diversity rich solutions and mainstreaming
the conservation and use of local agricultural biodiversity in the mountain agricultural production landscapes. The LCP adopted Diversity Field School (DFS) approach to sensitize and mobilize communities about the importance of local crop genetic resources, paving way in realizing the need of CSB and its institutionalization. DFS approach has been found effective to identify and mobilize custodians of agrobiodiversity, promote good practices such as participatory variety selection, grass-roots breeding, food fairs and promote farmer- to-farmer learning and sharing as a part of local capacity building processes. DFS approach has empowered women farmers to take leadership roles in managing community seed banks. The project engaged local governments (Palikas) from the beginning to make them realize the vital need of CSBs, strengthen local seed systems as a mechanism to increase access to quality seeds of traditional and underutilized crop species. It has resulted a positive outcome to develop ownership on institutionalizing CSB in local agriculture development plans and providing significant amount of financial resources and material support to establish and sustain CSBs in LCP sites. In remote high mountain areas, where seed business opportunity is limited; engagement of and ownership of local government is crucial to sustain CSBs
Nb\u3csub\u3e3\u3c/sub\u3eSn Coating of Twin Axis Cavity for SRF Applications
The twin axis cavity with two identical accelerating beams has been proposed for energy recovery linac (ERL) applications. Nb3Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities were fabricated at JLab and were proposed to be coated with Nb3Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavi-ties needs to be improved to coat these cavities. This development advances the current coating system at JLab for coating complex cavities. Two twin axis cavities were coated recently for the first time. This contribution dis-cusses initial results from coating of twin axis cavities, RF testing and witness sample analysis with an overview of the current challenges towards high performance Nb3Sn coated twin axis cavities
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