G. Ciovati, G. Cheng, E. Daly, G. Davi, M. Drury, J. Fischer, D. Forehand, K. Macha, F. Marhauser, E. McEwen, A. Mitchell, A. Reilly, R. Rimmer, S. Wang
The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refur-bished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into “cavity pairs” and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8×10 9 . The performance limitations were field emission and multipacting.
{"title":"Cavity Production and Testing of the First C75 Cryomodule for CEBAF","authors":"G. Ciovati, G. Cheng, E. Daly, G. Davi, M. Drury, J. Fischer, D. Forehand, K. Macha, F. Marhauser, E. McEwen, A. Mitchell, A. Reilly, R. Rimmer, S. Wang","doi":"10.2172/1905295","DOIUrl":"https://doi.org/10.2172/1905295","url":null,"abstract":"The CEBAF cryomodule rework program was updated over the last few years to increase the energy gain of refur-bished cryomodules to 75 MeV. The concept recycles the waveguide end-groups from original CEBAF cavities fabricated in the 1990s and replaces the five elliptical cells in each with a new optimized cell shape fabricated from large-grain, ingot Nb material. Eight cavities were fabricated at Research Instruments, Germany, and two cavities were built at Jefferson Lab. Each cavity was processed by electropolishing and tested at 2.07 K. The best eight cavities were assembled into “cavity pairs” and re-tested at 2.07 K, before assembly into the cryomodule. All but one cavity in the cryomodule were within 10% of the target accelerating gradient of 19 MV/m with a quality factor of 8×10 9 . The performance limitations were field emission and multipacting.","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127675940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Lechner, M. Kelley, A. Palczewski, C. Reece, J. Angle, F. Stevie
Impurity-alloying SRF cavities via thermal diffusion has yielded highly efficient Nb resonators. Recently, SRF cavities vacuum heat treated at 300 – 400 ° C for a few hours have exhibited high quality factors and behavior typical of alloyed cavities. Using secondary ion mass spectrometry, we investigated the interstitial concentration of carbon, nitrogen, and oxygen in niobium prepared by this method. Our investigation shows that oxygen is likely the primary diffusant in such recipes and is well-described by Ciovati’s model for native niobium oxide dissolution and oxygen diffusion.
{"title":"SIMS Investigation of Furnace-Baked Nb","authors":"E. Lechner, M. Kelley, A. Palczewski, C. Reece, J. Angle, F. Stevie","doi":"10.2172/1905495","DOIUrl":"https://doi.org/10.2172/1905495","url":null,"abstract":"Impurity-alloying SRF cavities via thermal diffusion has yielded highly efficient Nb resonators. Recently, SRF cavities vacuum heat treated at 300 – 400 ° C for a few hours have exhibited high quality factors and behavior typical of alloyed cavities. Using secondary ion mass spectrometry, we investigated the interstitial concentration of carbon, nitrogen, and oxygen in niobium prepared by this method. Our investigation shows that oxygen is likely the primary diffusant in such recipes and is well-described by Ciovati’s model for native niobium oxide dissolution and oxygen diffusion.","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114610479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Thermal Conductivity of Electroplated Copper Onto Bulk Niobium at Cryogenic Temperatures","authors":"P. Dhakal, G. Ciovati, I. Parajuli, T. Saeki","doi":"10.2172/1905553","DOIUrl":"https://doi.org/10.2172/1905553","url":null,"abstract":"","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132604300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Shape Evolution of C75 Large-Grain Niobium Half-Cells During Cavity Fabrication","authors":"G. Ciovati","doi":"10.2172/1905482","DOIUrl":"https://doi.org/10.2172/1905482","url":null,"abstract":"","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114969500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nb 3 Sn promises better RF performance ( Q and E acc ) than niobium at any given temperature because of superior superconducting properties. Nb 3 Sn-coated SRF cavities are now produced routinely by growing a few microns thick Nb 3 Sn films inside Nb cavities via the tin vapor diffusion technique. Sn evaporation and consumption during the growth process notably affect the quality of the coating. Aiming at favorable surface characteristics that could en-hance the RF performance, many coatings were produced by varying Sn sources and temperature profiles. Coupon samples were examined using different material character-ization techniques, and a selected few sets of coating parameters were used to coat 1.3 GHz single-cell cavities for RF testing. The Sn supply's careful tuning is essential to manage the microstructure, roughness, and overall surface characteristics of the coating. We summarize the material analysis of witness samples and discuss the performance of several Nb 3 Sn-coated single-cell cavities linked to Sn-source characteristics and observed Sn consumption during the film growth process.
Nb - 3sn在任何给定温度下都比铌具有更好的射频性能(Q和E - acc)，因为它具有优越的超导特性。目前，通过锡气扩散技术在Nb腔内生长几微米厚的Nb - 3sn膜，常规制备了Nb - 3sn包覆SRF腔。生长过程中锡的蒸发和消耗对镀层质量影响较大。为了获得能够提高射频性能的良好表面特性，采用不同的锡源和温度分布制备了许多涂层。使用不同的材料表征技术对优惠券样品进行了检测，并选择了几组涂层参数用于涂覆1.3 GHz单细胞腔进行射频测试。锡供应的精心调整对于管理涂层的微观结构，粗糙度和整体表面特性至关重要。我们总结了见证样品的材料分析，讨论了几种nb3sn涂层单电池腔的性能与Sn源特性的关系，并观察了薄膜生长过程中Sn的消耗。
{"title":"Managing Sn-supply to tune surface characteristics of vapor-diffusion coating of Nb3Sn","authors":"U. Pudasaini, C. Reece, J. Tiskumara","doi":"10.2172/1905472","DOIUrl":"https://doi.org/10.2172/1905472","url":null,"abstract":"Nb 3 Sn promises better RF performance ( Q and E acc ) than niobium at any given temperature because of superior superconducting properties. Nb 3 Sn-coated SRF cavities are now produced routinely by growing a few microns thick Nb 3 Sn films inside Nb cavities via the tin vapor diffusion technique. Sn evaporation and consumption during the growth process notably affect the quality of the coating. Aiming at favorable surface characteristics that could en-hance the RF performance, many coatings were produced by varying Sn sources and temperature profiles. Coupon samples were examined using different material character-ization techniques, and a selected few sets of coating parameters were used to coat 1.3 GHz single-cell cavities for RF testing. The Sn supply's careful tuning is essential to manage the microstructure, roughness, and overall surface characteristics of the coating. We summarize the material analysis of witness samples and discuss the performance of several Nb 3 Sn-coated single-cell cavities linked to Sn-source characteristics and observed Sn consumption during the film growth process.","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129278707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Pokhrel, G. Ciovati, P. Dhakal, J. Spradlin, C. Jing, A. Kanareykin
The development of high thermal conductivity coatings with pure copper or copper-tungsten alloy could be beneficial to improve the heat transfer of bulk Nb cavities for conduction cooling applications and to increase the stiffness of bulk Nb cavities cooled by liquid helium. Cold spray is an additive manufacturing technique suitable to grow thick coatings of either Cu or CuW on a Nb cavity. Bulk (~5 mm thick) coatings of Cu and CuW were deposited on standard 3 mm thick, high-purity Nb samples and smaller samples with 2 mm × 2 mm cross section were cut for measuring the thermal conductivity and the residual resistivity ratio. The samples were subjected to annealing at different temperatures and a maximum RRR of ~130 and ~40 were measured for the Cu samples and CuW samples, respectively.
{"title":"Electrical and Thermal Properties of Cold-Sprayed Bulk Copper and Copper-Tungsten Samples at Cryogenic Temperatures","authors":"H. Pokhrel, G. Ciovati, P. Dhakal, J. Spradlin, C. Jing, A. Kanareykin","doi":"10.2172/1905728","DOIUrl":"https://doi.org/10.2172/1905728","url":null,"abstract":"The development of high thermal conductivity coatings with pure copper or copper-tungsten alloy could be beneficial to improve the heat transfer of bulk Nb cavities for conduction cooling applications and to increase the stiffness of bulk Nb cavities cooled by liquid helium. Cold spray is an additive manufacturing technique suitable to grow thick coatings of either Cu or CuW on a Nb cavity. Bulk (~5 mm thick) coatings of Cu and CuW were deposited on standard 3 mm thick, high-purity Nb samples and smaller samples with 2 mm × 2 mm cross section were cut for measuring the thermal conductivity and the residual resistivity ratio. The samples were subjected to annealing at different temperatures and a maximum RRR of ~130 and ~40 were measured for the Cu samples and CuW samples, respectively.","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"156 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116836943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Dhakal, E. Daly, G. Davis, J. Fischer, D. Forehand, N. Huque, A. Mitchell, P. Owen, M. Howell, S. Kim, J. Mammosser
The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (β= 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date.
{"title":"Status of SNS Proton Power Upgrade SRF Cavities Production Qualification","authors":"P. Dhakal, E. Daly, G. Davis, J. Fischer, D. Forehand, N. Huque, A. Mitchell, P. Owen, M. Howell, S. Kim, J. Mammosser","doi":"10.2172/1905540","DOIUrl":"https://doi.org/10.2172/1905540","url":null,"abstract":"The Proton Power Upgrade project at Oak Ridge National Lab’s Spallation Neutron Source (SNS PPU) currently being constructed will double the proton beam power from 1.4 to 2.8 MW by adding 7 additional cryomodules, each contains four six-cell high beta (β= 0.81) superconducting radio frequency cavities. The cavities were built by Research Instruments, Germany, with all the cavity processing done at the vendor site, including electropolishing as the final active chemistry step. All 28 cavities needed for 7 cryomodules were delivered to Jefferson Lab, ready to be tested. The cryogenic RF qualifications and helium vessel welding were done at Jefferson Lab. The performance largely exceed the requirements, and greatly exceeded the performance of the original SNS cavity production series. Here, we present the summary of RF test on production cavities to this date.","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129395125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Overview on Recent Development of Conduction Cooling Cavities","authors":"G. Ciovati","doi":"10.2172/1905475","DOIUrl":"https://doi.org/10.2172/1905475","url":null,"abstract":"","PeriodicalId":293889,"journal":{"name":"International Conference on RF Superconductivity (20th), East Lansing, MI, USA, 28 June-02 July 2021","volume":"26 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120931302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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