SUSPB —  Student Poster   (25-Jun-23   14:00—18:00)
Paper Title Page
SUSPB002
Muon Spin Rotation Studies of Bilayer Superconductors and Low Temperature Baked Niobium  
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  • M. Asaduzzaman, R.E. Laxdal, R.M.L. McFadden, E. Thoeng
    TRIUMF, Vancouver, Canada
  • M. Asaduzzaman, T. Junginger, R.M.L. McFadden
    UVIC, Victoria, Canada
  • E. Thoeng
    UBC & TRIUMF, Vancouver, British Columbia, Canada
 
  Funding: Financial support was provided by an Natural Sciences and Engineering Research Council of Canada (NSERC)
Muon spin ro­ta­tion (muSR) re­sults have shown that vor­tex pen­e­tra­tion into Nb can be de­layed up to the su­per­heat­ing field Hsh by a sin­gle layer of a ma­te­r­ial with larger Lon­don pen­e­tra­tion depth. For low tem­per­a­ture baked (LTB) Nb an in­crease in the vor­tex pen­e­tra­tion field Hvp has also been ob­served. While clearly ex­ceed­ing the lower crit­i­cal field Hc1, Hvp was found to re­main sig­nif­i­cantly below Hsh for LTB nio­bium (Su­per­con­duc­tor Sci­ence and Tech­nol­ogy 30 (12), 125012). Fur­ther, mag­ne­tom­e­try ex­per­i­ments sug­gested that there is no in­ter­face bar­rier in LTB Nb and that the ap­par­ent Hvp in­crease as ob­served by muSR was due to sur­face pin­ning (Sci­en­tific Re­ports 12 (1), 5522). By vary­ing the im­plan­ta­tion depth of ~4.1 MeV muons using mod­er­at­ing foils, new muSR mea­sure­ments con­firm that the ap­par­ent Hvp in­crease in LTB Nb is in­deed due to sur­face pin­ning, while for a Nb₃Sn/Nb bi­layer we find an in­ter­face bar­rier for flux pen­e­tra­tion. These re­sults con­firm the po­ten­tial of using su­per­con­duct­ing bi­lay­ers to achieve a flux free Meiss­ner state up to the su­per­heat­ing field of the sub­strate.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB005  
About • Received ※ 17 June 2023 — Revised ※ 21 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 21 July 2023
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SUSPB004
In-Situ Quality Factor Measurements of SRF Cavities at S-DALINAC  
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  • R. Grewe, M. Arnold, A. Brauchpresenter, M. Dutine, L.E. Jürgensen, N. Pietralla, F. Schließmann, D. Schneider
    TU Darmstadt, Darmstadt, Germany
 
  Funding: Work supported by DFG (GRK 2128) and the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006)
The Su­per­con­duct­ing Darm­stadt Lin­ear Ac­cel­er­a­tor (S-DALINAC) is a thrice re­cir­cu­lat­ing elec­tron ac­cel­er­a­tor wich can be op­er­ated in a multi-turn en­ergy re­cov­ery mode*. The de­sign pa­ra­me­ters for ki­netic en­ergy and beam cur­rent are up to 130 MeV and up to 20 uA re­spec­tively. The in­jec­tor con­sists of a six-cell cap­ture cav­ity and two 20-cell srf cav­i­ties. The main linac con­sists of eight 20-cell cav­i­ties. The cav­i­ties are op­er­ated at a tem­per­a­ture of 2 K with a fre­quency of 2.9972(1) GHz. Mon­i­tor­ing of the srf cav­i­ties is im­por­tant for the over­all per­for­mance of the ac­cel­er­a­tor. A key pa­ra­me­ter for the rat­ing of the srf cav­ity per­for­mance is the in­trin­sic qual­ity fac­tor Q. At the S-DALINAC it is mea­sured for se­lected cav­i­ties dur­ing the yearly main­te­nance pro­ce­dures. The unique de­sign of the rf input cou­pler al­lows for a wide tun­ing range for the input cou­pling strength. This makes in-situ qual­ity fac­tor mea­sure­ments using the decay time mea­sure­ment method** pos­si­ble. The con­tri­bu­tion il­lus­trates the prin­ci­pal de­sign of the input cou­plers and the ben­e­fits it yields for Q mea­sure­ments. Re­cent re­sults in­clud­ing the pro­gres­sion of the qual­ity fac­tors over time will be pre­sented.
*Felix Schliessmann et al., Nat. Phys. 19, 597-602 (2023).
**Tom Powers, Proc. of SRF’05, Cornell University, Ithaca, New York, USA, 2005, p.40.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB008  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 04 August 2023
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SUSPB005
Plasma Electrolytic Polishing Technology Progress Development for Nb and Cu Substrates Preparation  
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  • E. Chyhyrynets, O. Azzolini, R. Caforio, D. Fonnesu, D. Ford, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • G. Marconato
    Università degli Studi di Padova, Padova, Italy
 
  Funding: Work supported by the INFN CSNV experiment SAMARA. Fundings from the EU’s Horizon 2020 Research and Innovation programme under Grant Agreement N 101004730. PNRR MUR project PE0000023-NQSTI.
Su­per­con­duct­ing radio fre­quency (SRF) cav­ity per­for­mance is highly de­pen­dent on sur­face prepa­ra­tion. Con­ven­tion­ally, elec­trop­o­l­ish­ing (EP) is used to achieve a clean sur­face and low rough­ness for both Nb and Cu sub­strates, but it re­quires harsh and cor­ro­sive so­lu­tions like con­cen­trated acids. Plasma Elec­trolytic Pol­ish­ing (PEP) is a promis­ing al­ter­na­tive that uses only di­luted salt so­lu­tions and has sev­eral ad­van­tages over EP. PEP can re­place in­ter­me­di­ate steps like me­chan­i­cal or chem­i­cal pol­ish­ing, thanks to its su­pe­rior re­moval rate of up to 2-8 um/min of Nb and 3-30 um/min of Cu. It achieves Ra rough­ness of 100 nm for both sub­strates and has a higher smooth­ing ef­fect than EP. PEP is also suit­able for nor­mal con­duct­ing cav­i­ties and other ac­cel­er­a­tor com­po­nents, in­clud­ing cou­plers. We demon­strate the ef­fec­tive­ness of PEP on SRF sub­strates and analyse sub­strate de­fect eval­u­a­tion. We demon­strate the ap­pli­ca­tion of PEP onto SRF sub­strates and analyse the sub­strate’s de­fect eval­u­a­tion. The on­go­ing work in­cludes Nb bulk and Nb on Cu QPR treat­ments and RF tests in col­lab­o­ra­tion with HZB.
 
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DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB009  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023
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SUSPB006
Analysis of Semiconductor Components as Temperature Sensors for Cryogenic Investigation of SRF Materials  
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  • A. Cierpka, S. Keckert, J. Knobloch, F. Kramer, O. Kugeler
    HZB, Berlin, Germany
 
  Tem­per­a­ture map­ping sys­tems have been used for many years to de­tect local heat­ing in an SRF cav­ity sur­face or ma­te­ri­als sam­ple. They re­quire a large num­ber of tem­per­a­ture sen­sors. Most often, low-cost Allen-Bradley re­sis­tors are used for this pur­pose. Since they have poor sen­si­tiv­ity and re­pro­ducibil­ity above 4 K, sen­sor al­ter­na­tives that com­bine the pre­ci­sion of Cer­nox sen­sors with the low-cost of Allen-Bradley re­sis­tors would be highly de­sir­able. In this work var­i­ous semi­con­duc­tor com­po­nents that ex­hibit a tem­per­a­ture de­pen­dent elec­tri­cal re­sponse, such as diodes and LEDs were an­a­lyzed with re­spect to sen­si­tiv­ity, re­pro­ducibil­ity and re­sponse speed in a tem­per­a­ture range be­tween 6.5 K and 22 K. In this range, many diodes and LEDs were found to be more sen­si­tive than Cer­nox sen­sors. How­ever, in some com­po­nents the re­sponse time was slow - pos­si­bly due to poor ther­mal con­tact.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB010  
About • Received ※ 08 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 17 July 2023
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SUSPB007
Influence of the Coating Parameters on the Tc of Nb₃Sn Thin Films on Copper Deposited via DC Magnetron Sputtering  
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  • D. Fonnesu, O. Azzolini, R. Caforio, E. Chyhyrynets, D. Ford, V.A. Garcia, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • G. Marconato
    Università degli Studi di Padova, Padova, Italy
 
  Funding: The I.FAST project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
The I.​FAST col­lab­o­ra­tion aims at push­ing the per­for­mance of par­ti­cle ac­cel­er­a­tors by de­vel­op­ing sus­tain­able in­no­v­a­tive tech­nolo­gies. Among its goals, the de­vel­op­ment of thin film-coated cop­per el­lip­ti­cal ac­cel­er­at­ing cav­i­ties cov­ers both the op­ti­miza­tion of the man­u­fac­tur­ing of seam­less sub­strates and the de­vel­op­ment of func­tional coat­ings able to con­form to the 3D cav­ity geom­e­try while de­liv­er­ing the needed per­for­mance. For the lat­ter, the op­ti­miza­tion of the de­po­si­tion recipe is cen­tral to a suc­cess­ful out­come. The work pre­sented here fo­cuses on the de­po­si­tion of Nb₃Sn films on flat, small cop­per sam­ples. The films are de­posited via DCMS from a pla­nar sto­i­chio­met­ric Nb₃Sn com­mer­cial tar­get. The re­sults of the film char­ac­ter­i­za­tion are pre­sented here. The ob­served de­pen­den­cies be­tween the film prop­er­ties and, in par­tic­u­lar, Tc(90%-10%) = (17.9±0.1)K is re­ported for Nb₃Sn on sap­phire and Tc(90%-10%) = (16.9±0.2)K for Nb₃Sn on cop­per with a 30 mi­cron thick nio­bium buffer layer.
 
poster icon Poster MOPMB013 [1.749 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB013  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 02 July 2023
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SUSPB008
NbTi Thin Film SRF Cavities for Dark Matter Search  
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  • G. Marconato
    Università degli Studi di Padova, Padova, Italy
  • D. Alesini, A. D’Elia, D. Di Gioacchino, C. Gatti, C. Ligi, G. Maccarrone, A. Rettaroli, S. Tocci
    LNF-INFN, Frascati, Italy
  • O. Azzolini, R. Caforio, E. Chyhyrynets, D. Fonnesupresenter, D. Ford, V.A. Garcia, G. Keppel, C. Pira, A. Salmaso, F. Stivanello
    INFN/LNL, Legnaro (PD), Italy
  • C. Braggio
    Univ. degli Studi di Padova, Padova, Italy
  • D. D’Agostino, U. Gambardella
    INFN-Salerno, Baronissi, Salerno, Italy
  • S. Posen
    Fermilab, Batavia, Illinois, USA
 
  Funding: Resources from U.S. DOE, Ofce of Science, NQISRC, SQMS contract No DE-AC02-07CH11359. Also from EU’s Horizon 2020 Research and Innovation programme, Grant Agreement No 101004730; INFN CSNV exp. SAMARA
The search for dark mat­ter is now look­ing at ALPs (ax­ion-like par­ti­cles) as a very promis­ing can­di­date to un­der­stand our uni­verse. Within this frame­work, we ex­plore the pos­si­bil­ity to use NbTi thin film coat­ings on Cu res­onat­ing cav­i­ties to in­ves­ti­gate the pres­ence of ax­ions in the range of 35-45 µeV mass by cou­pling the axion to a very strong mag­netic field in­side the cav­ity, caus­ing its con­ver­sion to a pho­ton which is sub­se­quently de­tected. In this work the chem­i­cal treat­ments and DC mag­netron sput­ter­ing de­tails of the prepa­ra­tion of 9 GHz, 7 GHz, and 3.9 GHz res­o­nant cav­i­ties and their qual­ity fac­tor mea­sure­ments at dif­fer­ent ap­plied mag­netic fields are pre­sented.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB014  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023
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SUSPB009
Development of a Plasma-Enhanced Chemical Vapor Deposition System for High-Performance SRF Cavities  
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  • G. Gaitan, A.T. Holic, W.I. Howes, G. Kulina, P. Quigley, J. Sears, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • M. Liepe
    Cornell University, Ithaca, New York, USA
  • B.W. Wendland
    University of Minnesota, Minnesota, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams
Next-gen­er­a­tion, thin-film sur­faces em­ploy­ing Nb₃Sn, NbN, NbTiN, or other com­pound su­per­con­duc­tors are es­sen­tial for reach­ing en­hanced RF per­for­mance lev­els in SRF cav­i­ties. How­ever, op­ti­mized, ad­vanced de­po­si­tion processes are re­quired to en­able high-qual­ity films of such ma­te­ri­als on large and com­plex-shaped cav­i­ties. For this pur­pose, Cor­nell Uni­ver­sity is de­vel­op­ing a plasma-en­hanced chem­i­cal vapor de­po­si­tion (CVD) sys­tem that fa­cil­i­tates coat­ing on com­pli­cated geome­tries with a high de­po­si­tion rate. This sys­tem is based on a high-tem­per­a­ture tube fur­nace with a high-vac­uum, gas, and pre­cur­sor de­liv­ery sys­tem, and uses plasma to sig­nif­i­cantly re­duce the re­quired pro­cess­ing tem­per­a­ture and pro­mote pre­cur­sor de­com­po­si­tion. Here we pre­sent an up­date on the de­vel­op­ment of this sys­tem, in­clud­ing final sys­tem de­sign, safety con­sid­er­a­tions, as­sem­bly, and com­mis­sion­ing.
 
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DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB015  
About • Received ※ 29 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 01 July 2023 — Issue date ※ 16 July 2023
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SUSPB010
Correlating Lambda Shift Measurements with RF Performance in Mid-T Heat Treated Cavities  
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  • R. Ghanbari, G.K. Deyu, W. Hillert, R. Monroy-Villa, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • C. Bate, D. Reschke, L. Steder, J.C. Wolff
    DESY, Hamburg, Germany
 
  Funding: This work was supported by the BMBF under the research grants 05K19GUB and 05H2021.
Heat treat­ment pro­ce­dures have been iden­ti­fied as cru-cial for the per­for­mance of nio­bium SRF cav­i­ties, which are the key tech­nol­ogy of mod­ern ac­cel­er­a­tors. The so called "mid-T heat treat­ments", in­vert the de­pen­dence of losses on the ap­plied ac­cel­er­at­ing field (anti-Q slope) and sig­nif­i­cantly re­duce the ab­solute value of losses. The mech­a­nism be­hind these im­prove­ments is still under in­ves­ti­ga­tion, and fur­ther re­search is needed to fully un­der­stand the prin­ci­ple processes in­volved. Anom­alies in the fre­quency shift near the tran­si­tion tem­per­a­ture (Tc), known as "dip" can pro­vide in­sight into fun­da­men­tal ma­te­r­ial prop­er­ties and allow us to study the re­la­tion-ship of fre­quency re­sponse with sur­face treat­ments. There­fore, we have mea­sured the fre­quency ver­sus tem­per­a­ture of mul­ti­ple mid-T heat treated cav­i­ties with dif­fer­ent recipes and stud­ied the cor­re­la­tion of SRF prop­er­ties with fre­quency shift fea­tures. The max­i­mum qual­ity fac­tor cor­re­lates with two such shift fea­tures, namely the dip mag­ni­tude per tem­per­a­ture width and the total fre­quency shift.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB021  
About • Received ※ 20 June 2023 — Revised ※ 25 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 15 August 2023
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SUSPB011
Magnetic Flux Expulsion in TRIUMF’s Multi-Mode Coaxial Cavities  
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  • R.R. Gregory, T. Junginger, M.W. McMullin
    UVIC, Victoria, Canada
  • T. Junginger, P. Kolb, R.E. Laxdal, M.W. McMullin, Z.Y. Yao
    TRIUMF, Vancouver, Canada
 
  The ex­ter­nal mag­netic flux sen­si­tiv­ity of SRF cav­i­ties is an im­por­tant char­ac­ter­is­tic of SRF ac­cel­er­a­tor de­sign. Pre­vi­ous stud­ies have shown that n-doped el­lip­ti­cal cav­i­ties are very sen­si­tive to ex­ter­nal fields, re­sult­ing in strin­gent re­quire­ments for resid­ual field and cav­ity cool-down speed. Few such stud­ies have been done on HWRs and QWRs. The im­pact of ap­plied field di­rec­tion and cool-down speed of flux ex­pul­sion for these cav­i­ties is poorly un­der­stood. This study ex­plores the ef­fect of these cool-down char­ac­ter­is­tics on TRI­UMF¿s QWR using COM­SOL ® sim­u­la­tions and ex­per­i­men­tal re­sults. This study seeks to max­i­mize the flux ex­pul­sion that oc­curs when a cav­ity is cooled down through its su­per­con­duct­ing tem­per­a­ture. Flux ex­pul­sion is af­fected by the cool-down speed, tem­per­a­ture gra­di­ent, and ori­en­ta­tion of the cav­ity rel­a­tive to an ap­plied mag­netic field. It was found that for a ver­ti­cally ap­plied mag­netic field the cool-down speed and tem­per­a­ture gra­di­ent did not have a sig­nif­i­cant ef­fect on flux ex­pul­sion. Con­trar­ily, a hor­i­zon­tal mag­netic field can be nearly com­pletely ex­pelled by a fast, high tem­per­a­ture gra­di­ent cool-down.  
poster icon Poster MOPMB023 [2.191 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB023  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 30 July 2023
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SUSPB012
The Collaborative Effects of Intrinsic and Extrinsic Impurities in Low RRR SRF Cavities  
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  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The SRF com­mu­nity has shown that in­tro­duc­ing cer­tain im­pu­ri­ties into high-pu­rity nio­bium can im­prove qual­ity fac­tors and ac­cel­er­at­ing gra­di­ents. We ques­tion why some im­pu­ri­ties im­prove RF per­for­mance while oth­ers hin­der it. The pur­pose of this study is to char­ac­ter­ize the im­pu­rity pro­file of nio­bium coupons with a low resid­ual re­sis­tance ratio (RRR) and cor­re­late these im­pu­ri­ties with the RF per­for­mance of low RRR cav­i­ties so that the mech­a­nism of im­pu­rity-based im­prove­ments can be bet­ter un­der­stood and im­proved upon. The com­bi­na­tion of RF test­ing and ma­te­r­ial analy­sis re­veals a mi­cro­scopic pic­ture of why low RRR cav­i­ties ex­pe­ri­ence low BCS re­sis­tance be­hav­ior more promi­nently than their high RRR coun­ter­parts. We per­formed sur­face treat­ments, low tem­per­a­ture bak­ing and ni­tro­gen-dop­ing, on low RRR cav­i­ties to eval­u­ate how the in­ten­tional ad­di­tion of oxy­gen and ni­tro­gen to the RF layer fur­ther im­proves per­for­mance through changes in the mean free path and im­pu­rity pro­file. The re­sults of this study have the po­ten­tial to un­lock a new un­der­stand­ing on SRF ma­te­ri­als and en­able the next gen­er­a­tion of high Q/high gra­di­ent sur­face treat­ments.
 
poster icon Poster MOPMB032 [1.444 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB032  
About • Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 23 July 2023
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SUSPB013
Exploration of Parameters that Affect High Field Q-Slope  
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  • K. Howard, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia, A. Grassellino
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The onset of high field Q-slope (HFQS) around 25 MV/m pre­vents cav­i­ties in elec­trop­o­l­ished (EP) con­di­tion from reach­ing high qual­ity fac­tors at high gra­di­ents due to the pre­cip­i­ta­tion of nio­bium hy­drides dur­ing cooldown. These hy­drides are non-su­per­con­duct­ing at 2 K, and con­tribute to losses such as Q dis­ease and HFQS. We are in­ter­ested in ex­plor­ing the pa­ra­me­ters that af­fect the be­hav­ior of HFQS. We study a high RRR cav­ity that re­ceived an 800 C by 3 hour bake and EP treat­ment to ob­serve HFQS. First, we ex­plore the ef­fect of trapped mag­netic flux. The cav­ity is tested after cool­ing slowly through Tc while ap­ply­ing var­i­ous lev­els of am­bi­ent field. We ob­serve the onset of the HFQS and cor­re­late this be­hav­ior with the amount of trapped flux. Next, we in­ves­ti­gate the ef­fect of the size/con­cen­tra­tion of hy­drides. The cav­ity is tested after hold­ing the tem­per­a­ture at 100 K for 12 hours dur­ing the cooldown to pro­mote the growth of hy­drides. We can cor­re­late the be­hav­ior of the HFQS with the in­creased hy­dride con­cen­tra­tion. Our re­sults will help fur­ther the un­der­stand­ing of the mech­a­nism of HFQS.
 
poster icon Poster MOPMB037 [1.648 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB037  
About • Received ※ 22 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 19 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB014
Comparing the Effectiveness of Low Temperature Bake in EP and BCP Cavities  
MOPMB040   use link to access more material from this paper's primary paper code  
 
  • H. Hu, Y.K. Kim
    University of Chicago, Chicago, Illinois, USA
  • D. Bafia
    Fermilab, Batavia, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Elec­trop­o­l­ish­ing (EP) and buffered chem­i­cal pol­ish­ing (BCP) are con­ven­tional sur­face prepa­ra­tion tech­niques for su­per­con­duct­ing ra­diofre­quency (SRF) cav­i­ties. Both EP and BCP treated SRF cav­i­ties dis­play high field Q-slope (HFQS) which de­grades per­for­mance at high gra­di­ents. While high gra­di­ent per­for­mance in EP cav­i­ties can be im­proved by in­tro­duc­ing oxy­gen via a low tem­per­a­ture bake (LTB) of 120°C by 48 hours, LTB does not con­sis­tently re­move HFQS in BCP cav­i­ties. There is no con­sen­sus as to why LTB is not ef­fec­tive on BCP pre­pared cav­i­ties. We ex­am­ine quench in EP, BCP, EP+LTB, and BCP+LTB treated 1.3 GHz sin­gle-cell Nb cav­i­ties by study­ing the heat­ing be­hav­ior with field using a tem­per­a­ture map­ping sys­tem. Cav­ity per­for­mance is cor­re­lated to char­ac­ter­i­za­tions of sur­face im­pu­rity pro­file ob­tained via time of flight sec­ondary ion mass spec­trom­e­try stud­ies. We ob­serve a dif­fer­ence in near sur­face hy­dro­gen con­cen­tra­tion fol­low­ing BCP com­pared to EP that may sug­gest that the causes of quench in EP and BCP cav­i­ties are dif­fer­ent.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB040  
About • Received ※ 28 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB015
Evaluation of Flux Expulsion and Flux Trapping Sensitivity of SRF Cavities Fabricated from Cold Work Nb Sheet with Successive Heat Treatment  
MOPMB042   use link to access more material from this paper's primary paper code  
 
  • B.D. Khanal
    ODU, Norfolk, Virginia, USA
  • P. Dhakal
    JLab, Newport News, Virginia, USA
 
  Funding: The work is partially supported by DOE HEP under Awards No. DE-SC 0009960. This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
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 treat­ment 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.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB042  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 04 July 2023
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SUSPB016
Quench Detection in a Superconducting Radio Frequency Cavity with Combined Temperature and Magnetic Field Mapping  
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  • B.D. Khanal, G. Ciovati
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, P. Dhakal
    JLab, Newport News, Virginia, USA
 
  Funding: This is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Local dis­si­pa­tion of rf power in SRF cav­i­ties cre­ate so called ’hot-spots’, pri­mary pre­cur­sors of cav­ity quench dri­ven by ei­ther ther­mal or mag­netic in­sta­bil­ity. These hot spots are may be 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 mag­neto-re­sis­tance sen­sors and car­bon re­sisters to lo­cate the hot spots and areas with high trapped flux on a 3 GHz sin­gle-cell Nb cav­ity dur­ing the rf tests at 2 K. The ef­fect of global and lo­cal­ized flux trap­ping on the rf per­for­mance will be pre­sented.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB045  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 12 August 2023
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SUSPB017
Modelling Trapped Flux in Niobium  
TUPTB002   use link to access more material from this paper's primary paper code  
 
  • F. Kramer, S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • J. Knobloch
    University of Siegen, Siegen, Germany
  • T. Kubo
    KEK, Ibaraki, Japan
 
  De­tailed mea­sure­ments of mag­netic flux dy­nam­ics and trapped mag­netic flux in nio­bium sam­ples were con­ducted with a new ex­per­i­men­tal setup that per­mits pre­cise con­trol of the cooldown pa­ra­me­ters. With this setup the de­pen­dency of trapped flux on the tem­per­a­ture gra­di­ent, ex­ter­nal mag­netic field, and cooldown rate can be mapped out in more de­tail com­pared to cav­ity mea­sure­ments. We have ob­tained un­ex­pected re­sults, and an ex­ist­ing model de­scrib­ing trapped flux in de­pen­dence of tem­per­a­ture gra­di­ent does not agree with the mea­sured data. There­fore, a new model is de­vel­oped which de­scribes the mag­ni­tude of trapped flux in de­pen­dence of the tem­per­a­ture gra­di­ent across the sam­ple dur­ing cooldown. The model de­scribes the amount of trapped flux lines with help of a den­sity dis­tri­b­u­tion func­tion of the pin­ning forces of pin­ning cen­ters and the ther­mal force which can de-pin flux lines from pin­ning cen­ters. The model shows good agree­ment with the mea­sured data and cor­rectly pre­dicts trapped flux at dif­fer­ent ex­ter­nal flux den­si­ties.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB002  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 13 July 2023
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SUSPB018
Commissioning of Dedicated Furnace for Nb₃Sn Coatings of 2.6 GHz Single Cell Cavities  
MOPMB047   use link to access more material from this paper's primary paper code  
 
  • P.A. Kulyavtsev, G.V. Eremeev, S. Posen, B. Tennis
    Fermilab, Batavia, Illinois, USA
  • J. Zasadzinski
    IIT, Chicago, Illinois, USA
 
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
We pre­sent the re­sults of com­mis­sion­ing a ded­i­cated fur­nace for Nb₃Sn coat­ings of 2.6GHz sin­gle cell cav­i­ties. Nb₃Sn is a de­sired coat­ing due to its high crit­i­cal tem­per­a­ture and smaller sur­face re­sis­tance com­pared to bulk Nb. Usage of Nb₃Sn coated cav­i­ties will greatly re­duce op­er­at­ing costs due to its higher op­er­at­ing tem­per­a­ture pro­vid­ing de­creased cool­ing costs. Tin is de­posited in the bulk Nb cav­ity by use of a tin chlo­ride nu­cle­ation agent and tin vapor dif­fu­sion. Analy­sis of the re­sul­tant coat­ing was per­formed using SEM/EDS to ver­ify suc­cess­ful for­ma­tion of de­sired Nb:Sn phase. Wit­ness sam­ples lo­cated in line of sight of the source were an­a­lyzed in order to un­der­stand the coat­ing ef­fi­cacy. The cav­ity’s per­for­mance was as­sessed in the Ver­ti­cal Test Stand (VTS) at Fer­mi­lab.
 
poster icon Poster MOPMB047 [4.858 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB047  
About • Received ※ 26 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 08 July 2023
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SUSPB019
Plasma Processing: Ignition Testing and Simulation Models for a 172 MHz HWR Cavity  
MOPMB049   use link to access more material from this paper's primary paper code  
 
  • M.E. McIntyre, B.R. Blomberg, M.P. Kelly, J.T. McLain, K.M. Villafania, G.P. Zinkann
    ANL, Lemont, Illinois, USA
  • Z. Wei
    GIT, Atlanta, Georgia, USA
 
  Main­te­nance and clean­ing of su­per­con­duct­ing RF cav­i­ties is labor in­ten­sive task that in­volves dis­as­sem­bling the cryo­stat hold­ing the res­onators and re­mov­ing them to be cleaned. At the Ar­gonne Tan­dem Linac Ac­cel­er­at­ing Sys­tem (ATLAS) at Ar­gonne Na­tional Lab­o­ra­tory, a pro­ject is un­der­way to re­search clean­ing the cav­i­ties in-situ by plasma pro­cess­ing. Pre­vi­ous plasma pro­cess­ing re­search by SNS, MSU, FNAL, and IJ­CLab has been suc­cess­ful in im­prov­ing field emis­sions post pro­cess­ing. It is ad­van­ta­geous to pur­sue re­search in this method, al­low­ing for pos­si­ble use on mod­ern ATLAS cry­omod­ules, A-tank and G-tank quar­ter-wave res­onators. The re­sults pre­sented show ini­tial plasma ig­ni­tion test­ing and plasma sim­u­la­tions for the cou­pled E and B fields, both done on a 172 MHz HWR cav­ity pre­vi­ously de­signed as early R&D for FRIB. Fu­ture plans are also in­cluded, lay­ing out next steps to test plasma pro­cess­ing on the same HWR cav­ity and even­tu­ally a QWR.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB049  
About • Received ※ 05 July 2023 — Revised ※ 25 July 2023 — Accepted ※ 24 September 2023 — Issue date ※ 24 September 2023
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SUSPB020
Thermal Feedback in Coaxial SRF Cavities  
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  • M.W. McMullin, P. Kolb, R.E. Laxdal, Z.Y. Yao
    TRIUMF, Vancouver, Canada
  • T. Junginger
    UVIC, Victoria, Canada
 
  Funding: Natural Sciences and Engineering Research Council of Canada
The phe­nom­e­non of Q-slope in SRF cav­i­ties is caused by a com­bi­na­tion of ther­mal feed­back and field-de­pen­dent sur­face re­sis­tance. There is cur­rently no com­monly ac­cepted model of field-de­pen­dent sur­face re­sis­tance, and stud­ies of Q-slope gen­er­ally treat ther­mal feed­back as a cor­rec­tion to whichever sur­face re­sis­tance model is being used. In the pre­sent study, we treat ther­mal feed­back as a dis­tinct phys­i­cal ef­fect whose ef­fect on Q-slope is cal­cu­lated using a novel fi­nite-el­e­ment code. We per­formed di­rect mea­sure­ments of liq­uid he­lium pool boil­ing from nio­bium sur­faces to ob­tain input pa­ra­me­ters for the fi­nite-el­e­ment code. This code was used to an­a­lyze data from TRI­UMF’s coax­ial test cav­ity pro­gram, which has pro­vided a rich dataset of Q-curves at tem­per­a­tures be­tween 1.7 K and 4.4 K at five dif­fer­ent fre­quen­cies. Pre­lim­i­nary re­sults show that ther­mal feed­back makes only a small con­tri­bu­tion to Q-slope at tem­per­a­tures near 4.2 K, but has stronger ef­fects as the bath tem­per­a­ture is low­ered.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB050  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 August 2023
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SUSPB021
Theoretical Study of Thin Noble-Metal Films on the Niobium Surface  
MOPMB053   use link to access more material from this paper's primary paper code  
 
  • C.A. Méndez, T. Arias, M. Liepe, N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  Funding: The Center for Bright Beams, Supported by National Science Foundation award No. PHY-1549132
Re­cent ex­per­i­ments sug­gest that no­ble-metal de­po­si­tion on nio­bium metal sur­faces can re­move the sur­face oxide and ul­ti­mately im­prove su­per­con­duct­ing ra­dio-fre­quency (SRF) cav­i­ties per­for­mance. In this pre­lim­i­nary study, we use den­sity-func­tional the­ory to in­ves­ti­gate the po­ten­tial for no­ble-metal pas­si­va­tion of re­al­is­tic, poly­crys­talline nio­bium sur­faces for SRF. Specif­i­cally, we in­ves­ti­gate the sta­bil­ity of gold and pal­la­dium mono­lay­ers on nio­bium sur­faces with dif­fer­ent crys­tal ori­en­ta­tions and eval­u­ate the im­pact of these im­pu­ri­ties on su­per­con­duct­ing prop­er­ties. In par­tic­u­lar, our re­sults sug­gest that gold can grow in thin lay­ers on the nio­bium sur­face, whereas pal­la­dium rather tends to dis­solve into the nio­bium cav­ity. These re­sults will help in­form on­go­ing ex­per­i­men­tal ef­forts to pas­si­vate nio­bium sur­faces of SRF cav­i­ties.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB053  
About • Received ※ 22 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
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SUSPB023
Optimisation of Niobium Thin Film Deposition Parameters for SRF Cavities  
MOPMB062   use link to access more material from this paper's primary paper code  
 
  • D.J. Seal, O.B. Malyshev, R. Valizadeh
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • G. Burt
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  • J.A. Conlon, O.B. Malyshev, K.T. Morrow, R. Valizadeh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
 
  In order to ac­cel­er­ate the pro­gres­sion of thin film (TF) de­vel­op­ment for fu­ture SRF cav­i­ties, it is de­sir­able to op­ti­mise ma­te­r­ial prop­er­ties on small flat sam­ples. Most im­por­tantly, this re­quires the abil­ity to mea­sure their su­per­con­duct­ing prop­er­ties. At Dares­bury Lab­o­ra­tory, it has been pos­si­ble for many years to char­ac­terise these films under DC con­di­tions; how­ever, it is not yet fully un­der­stood whether this cor­re­lates with RF mea­sure­ments. Re­cently, a high-through­put RF fa­cil­ity was com­mis­sioned that uses a novel 7.8 GHz choke cav­ity. The fa­cil­ity is able to eval­u­ate the RF per­for­mance of pla­nar-coated TF sam­ples at low peak mag­netic fields with a high through­put rate of 2-3 sam­ples per week. Using this fa­cil­ity, an op­ti­mi­sa­tion study of the de­po­si­tion pa­ra­me­ters of TF Nb sam­ples de­posited by HiP­IMS has begun. The ul­ti­mate aim is to op­ti­mise TF Nb as a base layer for mul­ti­layer stud­ies and repli­cate pla­nar mag­netron de­po­si­tions on split 6 GHz cav­i­ties. The ini­tial focus of this study was to in­ves­ti­gate the ef­fect of sub­strate tem­per­a­ture dur­ing de­po­si­tion. A re­view of the RF fa­cil­ity used and re­sults of this study will be pre­sented.  
poster icon Poster MOPMB062 [2.395 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB062  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 24 July 2023
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SUSPB024
Surface Characterization Studies of Gold-Plated Niobium  
MOPMB076   use link to access more material from this paper's primary paper code  
 
  • S.G. Seddon-Stettler, M. Liepe, T.E. Oseroff, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  Funding: The National Science Foundation, Grant No. PHY-1549132
The na­tive nio­bium oxide layer pre­sent on nio­bium has been shown to af­fect the per­for­mace of su­per­con­duct­ing RF cav­i­ties. Ex­tremely thin lay­ers of gold on the sur­face of nio­bium have the po­ten­tial to sup­press sur­face ox­i­da­tion and im­prove cav­ity per­for­mance. How­ever, de­posit­ing uni­form lay­ers of gold at the de­sired thick­ness (sub-nm) is dif­fi­cult, and dif­fer­ent de­po­si­tion meth­ods may have dif­fer­ent ef­fects on the gold sur­face, on the nio­bium sur­face, and on the in­ter­face be­tween the two. In par­tic­u­lar, the ques­tion of whether gold de­po­si­tion ac­tu­ally pas­si­vates the nio­bium oxide is ex­tremely rel­e­vant for as­sess­ing the po­ten­tial of gold de­po­si­tion to im­prove RF per­for­mance. This work builds on pre­vi­ous re­search study­ing the RF per­for­mance of gold/nio­bium bi­lay­ers with dif­fer­ent gold layer thick­nesses. We here con­sider al­ter­na­tive meth­ods to char­ac­ter­ize the com­po­si­tion and chem­i­cal prop­er­ties of gold/nio­bium bi­lay­ers to sup­ple­ment the pre­vi­ous RF study.
 
poster icon Poster MOPMB076 [1.536 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB076  
About • Received ※ 25 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 03 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB025
Investigation of the Multilayer Shielding Effect through NbTiN-AlN Coated Bulk Niobium  
MOPMB083   use link to access more material from this paper's primary paper code  
 
  • I.H. Senevirathne, J.R. Delayen, A.V. Gurevich
    ODU, Norfolk, Virginia, USA
  • D.R. Beverstock, J.R. Delayen, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • D.R. Beverstock
    The College of William and Mary, Williamsburg, Virginia, USA
 
  We re­port mea­sure­ments of the dc field onset Bp of mag­netic flux pen­e­tra­tion through NbTiN-AlN coat­ing on bulk nio­bium using the Hall probe ex­per­i­men­tal setup. The mea­sure­ments of Bp re­veal the mul­ti­layer shield­ing ef­fect on bulk nio­bium under high mag­netic fields at cryo­genic tem­per­a­tures. We ob­served a sig­nif­i­cant en­hance­ment in Bp for the NbTiN-AlN coated Nb sam­ples as com­pared to bare Nb sam­ples. The ob­served de­pen­dence of Bp on the coat­ing thick­ness is con­sis­tent with the­o­ret­i­cal pre­dic­tions.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB083  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 12 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB026
Optimizing Growth of Niobium-3 Tin Through Pre-nucleation Chemical Treatments  
MOPMB093   use link to access more material from this paper's primary paper code  
 
  • S.G. Arnold, G. Gaitan, M. Liepe, L. Shpanipresenter, Z. Sun
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Arias, N. Sitaraman
    Cornell University, Ithaca, New York, USA
 
  Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
Nb₃Sn is a promis­ing al­ter­na­tive ma­te­r­ial for SRF cav­i­ties that is close to reach­ing prac­ti­cal ap­pli­ca­tions. To date, one of the most ef­fec­tive growth meth­ods for this ma­te­r­ial is vapor dif­fu­sion, yet fur­ther im­prove­ment is needed for Nb₃Sn to reach its full po­ten­tial. The major is­sues faced by vapor dif­fu­sion are tin de­pleted re­gions and sur­face rough­ness, both of which lead to im­paired per­for­mance. Lit­er­a­ture has shown that the nio­bium sur­face oxide plays an im­por­tant role in the bind­ing of tin to nio­bium. In this study, we per­formed var­i­ous chem­i­cal treat­ments on nio­bium sam­ples pre-nu­cle­ation to en­hance tin nu­cle­ation. We quan­tify the ef­fect that these var­i­ous treat­ments had through scan­ning elec­tron mi­croscopy (SEM) and en­ergy dis­per­sive spec­troscopy (EDS). These meth­ods re­veal in­for­ma­tion on tin nu­cle­ation den­sity and uni­for­mity, and a thin tin film pre­sent on most sam­ples, even in the ab­sence of nu­cle­ation sites. We pre­sent our find­ings from these sur­face char­ac­ter­i­za­tion meth­ods and in­tro­duce a frame­work for quan­ti­ta­tively com­par­ing the sam­ples. We plan to apply the most ef­fec­tive treat­ment to a cav­ity and con­duct an RF test soon.
 
poster icon Poster MOPMB093 [1.118 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB093  
About • Received ※ 21 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB027
Design of a 1.3 GHz High-Power RF Coupler for Conduction-Cooled Systems  
MOPMB094   use link to access more material from this paper's primary paper code  
 
  • N.A. Stilin, A.T. Holic, M. Liepe, T.I. O’Connell, P. Quigley, J. Sears, V.D. Shemelin, J. Turco
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cor­nell is de­sign­ing a new stand­alone, com­pact SRF cry­omod­ule which uses cry­ocool­ers in place of liq­uid he­lium for cool­ing. One of the biggest chal­lenges in im­ple­ment­ing such a sys­tem is de­sign­ing a high-power input cou­pler which is able to be cooled by the cry­ocool­ers with­out any ad­di­tional liq­uid cryo­gen­ics. Due to the lim­ited heat load ca­pac­ity of the cry­ocool­ers at 4.2 K, this re­quires very care­ful ther­mal iso­la­tion of the 4.2 K por­tion of the cou­pler and thor­ough op­ti­miza­tion of the RF be­hav­ior to min­i­mize losses. This paper will pre­sent the var­i­ous de­sign con­sid­er­a­tions which en­abled the cre­at­ing of a con­duc­tion-cooled 1.3 GHz input cou­pler ca­pa­ble of de­liv­er­ing up to 100 kW CW RF power.  
poster icon Poster MOPMB094 [0.964 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB094  
About • Received ※ 16 June 2023 — Revised ※ 26 June 2023 — Accepted ※ 27 June 2023 — Issue date ※ 23 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB029
Update on Cornell High Pulsed Power Sample Host Cavity  
WEPWB108   use link to access more material from this paper's primary paper code  
 
  • N.M. Verboncoeur, A.T. Holic, M. Liepe, T.E. Oseroff, R.D. Porter, J. Sears, L. Shpani
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • R.D. Porter
    SLAC, Menlo Park, California, USA
 
  The Cor­nell High Pulsed Power Sam­ple Host Cav­ity (CH­PP­SHC) is de­signed to mea­sure the tem­per­a­ture-de­pen­dent su­per­heat­ing fields of fu­ture SRF ma­te­ri­als and thereby gain in­sights into the ul­ti­mate lim­its of their per­for­mance. The­o­ret­i­cal es­ti­ma­tion of the su­per­heat­ing fields of SRF ma­te­ri­als is chal­leng­ing and mostly has been done for tem­per­a­tures near the crit­i­cal tem­per­a­ture or in the in­fi­nite kappa limit. Ex­per­i­men­tal data cur­rently avail­able is in­com­plete, and often im­pacted by ma­te­r­ial de­fects and their re­sult­ing ther­mal heat­ing, pre­vent­ing find­ing the fun­da­men­tal lim­its of the­ses ma­te­ri­als. The CH­PP­SHC sys­tem al­lows reach­ing RF fields in ex­cess of half a Tesla within mi­crosec­onds on ma­te­r­ial sam­ples by uti­liz­ing high pulsed power, thereby out­run­ning ther­mal ef­fects. We are prin­ci­pally in­ter­ested in the su­per­heat­ing field of Nb₃Sn, a ma­te­r­ial of in­ter­est for the SRF com­mu­nity, and pre­sent here the cur­rent fab­ri­ca­tion and as­sem­bly sta­tus of the CH­PP­SHC as well as early re­sults.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB108  
About • Received ※ 27 June 2023 — Revised ※ 20 July 2023 — Accepted ※ 20 August 2023 — Issue date ※ 22 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB032
Evaluation of Photo-Cathode Port Multipacting in the SRF Photo-Injector Cryomodule for the LCLS-II High-Energy Upgrade  
WEPWB113   use link to access more material from this paper's primary paper code  
 
  • Z.Y. Yin, W. Hartung, S.H. Kim, T. Konomi, T. Xu
    FRIB, East Lansing, Michigan, USA
 
  The high-en­ergy up­grade of the Linac Co­her­ent Light Source (LCLS-II-HE) will in­crease the pho­ton en­ergy and bright­ness. A low-emit­tance in­jec­tor (LEI) was pro­posed to in­crease the pho­ton flux for high X-ray en­er­gies. FRIB, HZDR, Ar­gonne, and SLAC are de­vel­op­ing a 185.7 MHz su­per­con­duct­ing ra­dio-fre­quency photo-in­jec­tor (SRF-PI) cry­omod­ule for the LEI. The photo-cath­ode sys­tem re­quire­ments are chal­leng­ing, as cath­odes must be main­tained at the de­sired tem­per­a­ture, pre­cisely aligned, and op­er­ated with­out mul­ti­pact­ing (MP); to avoid field emis­sion, cath­ode ex­change must be par­tic­u­late-free. A sup­port stalk has been de­signed to hold the cath­ode in po­si­tion under these re­quire­ments. A DC bias is used to in­hibit MP. We sim­u­lated MP for var­i­ous sur­face con­di­tions and bias lev­els. An RF/DC test was de­vel­oped to eval­u­ate the cath­ode stalk per­for­mance as a sub­sys­tem and to iden­tify and cor­rect is­sues be­fore as­sem­bly into the full cry­omod­ule. The RF/DC test makes use of a res­o­nant coax­ial line to gen­er­ate an RF mag­netic field sim­i­lar to that of the cath­ode-in-SRF-PI-cav­ity case. High-power test re­sults will be pre­sented and com­pared to the MP sim­u­la­tions.
* Work supported by the Department of Energy Contract DE-AC02-76SF00515
 
poster icon Poster WEPWB113 [1.410 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB113  
About • Received ※ 20 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 26 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB033
Study and Improvements of Liquid Tin Diffusion Process to Synthesize Nb₃Sn Cylindrical Targets  
WEPWB118   use link to access more material from this paper's primary paper code  
 
  • D. Ford, E. Chyhyrynets, D. Fonnesu, G. Keppel, G. Marconato, C. Pira, A. Salmaso
    INFN/LNL, Legnaro (PD), Italy
 
  Funding: This project has received funding from the European Union¿s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
Nb₃Sn thin films on bulk Nb cav­i­ties ex­hibit com­pa­ra­ble per­for­mance to bulk Nb at lower tem­per­a­tures, and using Cu as a sub­strate ma­te­r­ial can fur­ther im­prove per­for­mance and re­duce costs. How­ever, coat­ing sub­strates with curved geome­tries like el­lip­ti­cal cav­i­ties can be chal­leng­ing due to the brit­tle­ness of Nb₃Sn tar­gets pro­duced by a clas­si­cal sin­ter­ing tech­nique. This work ex­plores the use of the Liq­uid Tin Dif­fu­sion (LTD) tech­nique to pro­duce sput­ter­ing tar­gets for 6 GHz el­lip­ti­cal cav­i­ties, which al­lows for the de­po­si­tion of thick and uni­form coat­ings on Nb sub­strate, even for com­plex geome­tries. The study in­cludes im­prove­ments in the LTD process and the pro­duc­tion of a sin­gle-use LTD tar­get, as well as the char­ac­ter­i­za­tion of Nb₃Sn films coated by DC mag­netron sput­ter­ing using these in­no­v­a­tive tar­gets.
 
poster icon Poster WEPWB118 [5.462 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB118  
About • Received ※ 17 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 01 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB034
Additive Manufacturing of Pure Niobium and Copper Using Laser Powder Bed Fusion for Particle Accelerator Applications  
WEPWB119   use link to access more material from this paper's primary paper code  
 
  • D. Ford, R. Caforio, E. Chyhyrynets, G. Keppel, C. Pira
    INFN/LNL, Legnaro (PD), Italy
  • M. Bonesso, S. Candela, V. Candela, R. Dima, G. Favero, A. Pepato, P. Rebesan, M. Romanato
    INFN- Sez. di Padova, Padova, Italy
  • M. Pozzi
    Rösler Italiana s.r.l., Concorezzo, Italy
 
  Funding: This project has received funding from the European Union¿s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. Work supported by the INFN CSNV experiment SAMARA.
In this study, Metal Ad­di­tive Man­u­fac­tur­ing (MAM) was eval­u­ated as a vi­able method for pro­duc­ing seam­less 6 GHz pure cop­per and nio­bium pro­to­types with­out the use of in­ter­nal sup­ports. Pre­lim­i­nary tests were per­formed to eval­u­ate print­abil­ity, lead­ing to fur­ther in­ves­ti­ga­tions into sur­face treat­ments to re­duce sur­face rough­ness from 35 µm to less than 1 µm. Ad­di­tional pro­to­types were printed using dif­fer­ent pow­ders and ma­chines, ex­plor­ing var­i­ous print­ing pa­ra­me­ters and in­no­v­a­tive con­tact­less sup­port­ing struc­tures to im­prove the qual­ity of down­ward-fac­ing sur­faces with small in­cli­na­tion an­gles. These struc­tures en­abled the fab­ri­ca­tion of seam­less SRF cav­i­ties with a rel­a­tive den­sity greater than 99.8%. Qual­ity test­ing was con­ducted using tech­niques such as to­mog­ra­phy, leak test­ing, res­o­nant fre­quency as­sess­ment, and in­ter­nal in­spec­tion. The re­sults of this study are pre­sented herein.
 
poster icon Poster WEPWB119 [9.235 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB119  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 18 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB035
Investigation of Coupler Breakdown Thresholds for Plasma Processing of FRIB Quarter-Wave Resonators with Fundamental and Higher-Order Modes  
WEPWB127   use link to access more material from this paper's primary paper code  
 
  • P.R. Tutt, W. Hartung, S.H. Kim, T. Xu
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB) under Award Number DE-SC0000661.
FRIB is de­vel­op­ing plasma pro­cess­ing tech­niques for in-situ re­cov­ery of cav­ity per­for­mance in linac cry­omod­ules dur­ing long-term user op­er­a­tion. While plasma pro­cess­ing has been shown to be ef­fec­tive for high-fre­quency (0.8 - 1.5 GHz) el­lip­ti­cal cav­i­ties, one of the chal­lenges for FRIB is to avoid plasma break­down in the fun­da­men­tal input cou­pler (FPC), which has rel­a­tively weak cou­pling strength (Qext rang­ing from 2E6 to 1E7). FRIB cav­i­ties are not equipped with higher-or­der-mode (HOM) cou­plers; how­ever, in pre­lim­i­nary tests, we found that HOMs are suit­able for plasma pro­cess­ing of FRIB Quar­ter-Wave Res­onators (QWRs) dri­ven via the FPC. In this study, we in­ves­ti­gated plasma break­down thresh­olds in the fun­da­men­tal and the first 2 HOMs for the FRIB β = 0.085 QWRs. Elec­tric field dis­tri­b­u­tions in the FPC re­gion and cav­ity re­gion were cal­cu­lated for the room-tem­per­a­ture case using CST Mi­crowave Stu­dio’s fre­quency do­main solver (FDS). Sim­u­la­tion re­sults will be pre­sented, with com­par­i­son of break­down thresh­olds in­ferred from the RF mod­el­ing to the ex­per­i­men­tal re­sults.
 
poster icon Poster WEPWB127 [5.068 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB127  
About • Received ※ 19 June 2023 — Revised ※ 27 June 2023 — Accepted ※ 28 June 2023 — Issue date ※ 11 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB036
Experimental Study of Mechanical Dampers for the FRIB β=0.041 Quarter-Wave Resonators  
WEPWB128   use link to access more material from this paper's primary paper code  
 
  • J. Brown, W. Chang, W. Hartung, S.H. Kim, T. Xu
    FRIB, East Lansing, Michigan, USA
 
  Funding: Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award numbers DE-SC0018362 and DE-SC0000661 and Michigan State University.
The ’pen­du­lum’ me­chan­i­cal mode of quar­ter-wave res­onators (QWR) often causes an issue with mi­cro­phon­ics and/or pon­dero­mo­tive in­sta­bil­ity un­less oth­er­wise the inner con­duc­tors are prop­erly stiff­ened and/or damped. FRIB QWRs are equipped with a Leg­naro-style fric­tional damper in­stalled in­side of the inner con­duc­tor such that it coun­ter­acts the os­cil­la­tions of the inner con­duc­tor. In cry­omod­ule tests and linac op­er­a­tion, we ob­served that the damp­ing ef­fi­ciency is dif­fer­ent for a few β=0.041 QWRs. This study aimed to ex­per­i­men­tally char­ac­ter­ize the damp­ing ef­fi­cacy as a func­tion of damper mass and sur­face rough­ness. We pre­sent damp­ing mea­sure­ments at room tem­per­a­ture and at two dif­fer­ent masses and sur­face rough­ness as well as dis­cuss fu­ture stud­ies for damper re-op­ti­miza­tion based on this fol­low-on study.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB128  
About • Received ※ 20 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 04 August 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB038
Nb₃Sn Vapor Diffusion Coating System at SARI: Design, Construction, and Commissioning  
WEPWB043   use link to access more material from this paper's primary paper code  
 
  • Q.X. Chen, Y. Zongpresenter
    SINAP, Shanghai, People’s Republic of China
  • J.F. Chen, S. Xing
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • J. Rong
    SSRF, Shanghai, People’s Republic of China
 
  This paper de­scribes the de­sign of a coat­ing sys­tem for the prepa­ra­tion of a su­per­con­duct­ing ra­dio-fre­quency cav­ity with Nb3Sn thin films. The de­vice con­sists of a coat­ing cham­ber made of pure nio­bium, a vac­uum fur­nace for heat­ing the coat­ing cham­ber, a su­per­con­duct­ing cav­ity bracket and two cru­cible heaters. The cham­ber is vac­uum iso­lated from the fur­nace body to pro­tect the su­per­con­duct­ing cav­ity from con­t­a­m­i­na­tion dur­ing the coat­ing process. The de­vice has been built and com­mis­sioned, which could be used for Nb₃Sn coat­ing of a 1.3 GHz sin­gle-cell su­per­con­duct­ing cav­ity in fu­ture.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB043  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 08 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB039
Realization of Accelerating Gradient Larger than 25 MV/m on High-Q 1.3 GHz 9-Cell Cavities for SHINE  
WEPWB044   use link to access more material from this paper's primary paper code  
 
  • Y. Zong, Q.X. Chen, X. Huang, Z. Wang
    SINAP, Shanghai, People’s Republic of China
  • J.F. Chen, P.C. Dong, H.T. Hou, X.Y. Pu, J. Shi, S. Sun, D. Wang, J.N. Wu, S. Xing, S.J. Zhao, Y.L. Zhao
    SARI-CAS, Pudong, Shanghai, People’s Republic of China
  • Y.W. Huang
    ShanghaiTech University, Shanghai, People’s Republic of China
  • X.W. Wu
    Zhangjiang Lab, Shanghai, People’s Republic of China
 
  Funding: This work was supported by Shanghai Municipal Science and Technology Major Project (No. 2017SHZDZX02).
We pre­sent our stud­ies on the op­ti­mized ni­tro­gen-dop­ing and medium-tem­per­a­ture bak­ing recipes ap­plied on 1.3GHz SRF cav­i­ties, aim­ing at meet­ing the re­quire­ments of the SHINE pro­ject. The op­ti­mized ni­tro­gen-dop­ing process re­sulted in achiev­ing a Q₀ of over 4.0×1010 at medium field and a max­i­mum ac­cel­er­at­ing gra­di­ent ex­ceed­ing 35 MV/m on sin­gle cell cav­i­ties, and a Q₀ of over 2.8×1010 at medium field and a max­i­mum ac­cel­er­at­ing gra­di­ent ex­ceed­ing 26 MV/m in 9-cell cav­i­ties. For 1.3 GHz 9-cell cav­i­ties sub­jected to medium-tem­per­a­ture bak­ing, Q₀ val­ues ex­ceed­ing 3.5×1010 at 16 MV/m and max­i­mum ac­cel­er­at­ing gra­di­ents sur­pass­ing 25 MV/m were achieved. These stud­ies pro­vide two op­tions of high-Q recipes for SHINE cav­i­ties. The treat­ment processes of cav­i­ties and their ver­ti­cal test re­sults are de­scribed in this paper.
*chenjinfang@sari.ac.cn
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB044  
About • Received ※ 19 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 26 June 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB040
The Oxidizing Responses of Baked Niobium Exposed to Various Gases via In-situ NAXPS  
WEPWB045   use link to access more material from this paper's primary paper code  
 
  • Z.T. Yang, J.K. Hao, K.X. Liu, S.W. Quan
    PKU, Beijing, People’s Republic of China
 
  We car­ried out in-situ NAXPS (Near-at­mos­pheric X-ray Pho­to­elec­tron Spec­troscopy) on SRF-cav­ity class nio­bium to ob­serve its ox­i­diz­ing re­sponses when ex­posed to var­i­ous gases. The nio­bium sam­ples were baked at 800°C until the peaks of nio­bium ox­ides dis­ap­peared in the spec­trum. Then the re­vealed pure nio­bium sam­ples were ex­posed to the air-pro­por­tion mix­ture of ni­tro­gen and oxy­gen, pure oxy­gen, and pure water vapor re­spec­tively. And for the pure oxy­gen and water vapor group, we also car­ried out TOF-SIMS (Time-of-Flight Sec­ondary Ion Mass Spec­troscopy) mea­sure­ments be­fore and after the bak­ing and ox­i­da­tion ex­per­i­ments. We found that pure oxy­gen and water vapor could ox­i­dize nio­bium at sim­i­lar rate which was faster than the N2/O2 mix­ture. After re-ox­i­dized by pure oxy­gen and water vapor, the nio­bium sam­ple pre­sented a sig­nif­i­cant in­crease of in­ter­sti­tial car­bon and a mod­er­ate in­crease of in­ter­sti­tial oxy­gen in the mag­netic pen­e­tra­tion depth, while it showed a mild de­crease of in­ter­sti­tial hy­dro­gen.  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB045  
About • Received ※ 15 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 25 June 2023 — Issue date ※ 31 July 2023
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
SUSPB042
Refurbishment of an Elbe-Type Cryomodule for Coated HOM-Antenna Tests for MESA  
WEPWB057   use link to access more material from this paper's primary paper code  
 
  • P.S. Plattner, F. Hug, T. Stengler
    KPH, Mainz, Germany
 
  Funding: The work received funding by BMBF through 05H21UMRB1.
The Mainz En­ergy-Re­cov­er­ing Su­per­con­duct­ing Ac­cel­er­a­tor (MESA), an en­ergy-re­cov­er­ing (ER) LINAC, is cur­rently under con­struc­tion at the uni­ver­sity Mainz. In the ER mode a con­tin­ues wave (CW) beam is ac­cel­er­ated from 5 MeV up to 105 MeV with a beam cur­rent of up to 1 mA. This cur­rent is ac­cel­er­ated and de­cel­er­ated twice within a cav­ity. For fu­ture ex­per­i­ments, the beam cur­rent limit has to be pushed up to 10 mA. An analy­sis of the MESA cav­i­ties has shown that the HOM an­ten­nas quench at such high beam cur­rents due to the ex­ten­sive power de­po­si­tion and the re­sult­ing heat­ing of the HOM cou­pler. To avoid quench­ing it is nec­es­sary to use su­per­con­duct­ing ma­te­ri­als with higher crit­i­cal tem­per­a­ture. For this pur­pose, the HOM an­ten­nas will be coated with NbTiN and Nb3SN and their prop­er­ties will be in­ves­ti­gated. For use in the ac­cel­er­a­tor, the HOM an­ten­nas will be in­stalled in the cav­i­ties of a for­mer ALICE cry­omod­ule, kindly pro­vided by STFC Dares­burry. This paper will show both the sta­tus of the re­fur­bish­ment of the ALICE mod­ule to suit MESA, and the coat­ing of the HOM an­ten­nas.
The authors would like to express their sincere gratitude to STFC Daresbury for the donation of the ALICE module, which strongly supports SRF research in Mainz.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB057  
About • Received ※ 18 June 2023 — Revised ※ 22 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 09 July 2023
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SUSPB043
Impact of Medium Temperature Heat Treatments on the Magnetic Flux Expulsion Behavior of SRF Cavities  
WEPWB065   use link to access more material from this paper's primary paper code  
 
  • J.C. Wolff, J. Eschke, A. Gössel, K. Kasprzak, D. Reschke, L. Steder, L. Trelle, M. Wiencek
    DESY, Hamburg, Germany
  • W. Hillert
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
 
  Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Medium tem­per­a­ture (mid-T) heat treat­ments at 300 °C are used to en­hance the in­trin­sic qual­ity fac­tor of su­per­con­duct­ing radio fre­quency (SRF) cav­i­ties. Un­for­tu­nately, such treat­ments po­ten­tially in­crease the sen­si­tiv­ity to trapped mag­netic flux and con­se­quently the sur­face re­sis­tance of the cav­ity. For this rea­son, it is cru­cial to max­i­mize the ex­pul­sion of mag­netic flux dur­ing the cool down. The flux ex­pul­sion be­hav­ior is next to the heat treat­ment mainly de­ter­mined by the geom­e­try, the nio­bium grain size and the grain ori­en­ta­tion. How­ever, it is also af­fected by pa­ra­me­ters of the cav­ity per­for­mance tests like the cool down ve­loc­ity, the spa­tial tem­per­a­ture gra­di­ent along the cav­ity sur­face and the mag­netic flux den­sity dur­ing the tran­si­tion of the crit­i­cal tem­per­a­ture. To im­prove the flux ex­pul­sion be­hav­ior and hence the ef­fi­ciency of fu­ture ac­cel­er­a­tor fa­cil­i­ties, the im­pact of these ad­justable pa­ra­me­ters as well as the mid-T heat treat­ment on 1.3 GHz TESLA-Type sin­gle-cell cav­i­ties is in­ves­ti­gated by a new ap­proach of a mag­ne­to­met­ric map­ping sys­tem. In this con­tri­bu­tion first per­for­mance test re­sults of cav­i­ties be­fore- and after mid-T heat treat­ment are pre­sented.
 
poster icon Poster WEPWB065 [3.077 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-WEPWB065  
About • Received ※ 28 June 2023 — Revised ※ 28 June 2023 — Accepted ※ 29 June 2023 — Issue date ※ 13 July 2023
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SUSPB045
Commissioning of the UHH Quadrupole Resonator at DESY  
THCAA02   use link to access more material from this paper's primary paper code  
WEPWB074   use link to access more material from this paper's primary paper code  
 
  • R. Monroy-Villa, W. Hillert, M. Wenskat
    University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
  • A. Gössel, D. Reschke, M. Röhling, M. Schmökel, J.H. Thie, M. Wiencek
    DESY, Hamburg, Germany
  • C. Martens
    University of Hamburg, Hamburg, Germany
 
  Funding: This work was supported by the BMBF under the research grants 05H18GURB1, 05K19GUB and 05H2021.
Push­ing the lim­its of the ac­cel­er­at­ing field or qual­ity fac­tor of SRF cav­i­ties be­yond pure Nb re­quires the im­ple­men­ta­tion of spe­cific inner sur­face treat­ments, which are yet to be stud­ied and op­ti­mized. One of the fun­da­men­tal chal­lenges in ex­plor­ing al­ter­na­tive ma­te­ri­als is that only sam­ples or cav­ity cuts can be fully char­ac­ter­ized from a ma­te­r­ial point of view. On the other hand, com­plete cav­i­ties allow for the SRF char­ac­ter­i­za­tion of the inner sur­face, while sam­ples can usu­ally only be an­a­lyzed using DC meth­ods. To ad­dress this prob­lem, a test res­onator for sam­ples, called "Quadru­pole Res­onator", was de­signed and op­er­ated at CERN and later at HZB. It al­lows for a full RF char­ac­ter­i­za­tion of sam­ples at fre­quen­cies of 0.42 GHz, 0.86 GHz, and 1.3 GHz, within a tem­per­a­ture range of 2-20 K and at mag­netic fields up to 120 mT. This work pre­sents the de­sign process, which in­cor­po­rated im­prove­ments mo­ti­vated by me­chan­i­cal and RF stud­ies and ex­pe­ri­ence, and the re­sults from both warm and cold com­mis­sion­ing are dis­cussed. More im­por­tant, the re­sults for the RF tests of a Nb sam­ple after un­der­go­ing a se­ries of heat treat­ments and an out­look of the fur­ther usage of the QPR is pre­sented.
 
slides icon Slides THCAA02 [6.677 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-THCAA02  
About • Received ※ 25 June 2023 — Revised ※ 29 June 2023 — Accepted ※ 19 August 2023 — Issue date ※ 19 August 2023
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SUSPB047
First Results from Nb₃Sn Coatings of 2.6 GHz Nb SRF Cavities Using DC Cylindrical Magnetron Sputtering System  
TUPTB019   use link to access more material from this paper's primary paper code  
 
  • M.S. Shakel, H. Elsayed-Ali
    ODU, Norfolk, Virginia, USA
  • G.V. Eremeev
    Fermilab, Batavia, Illinois, USA
  • U. Pudasaini, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
 
  Funding: Supported by DOE, Office of Accelerator R&D and Production, Contact No. DE-SC0022284, with partial support by DOE, Office of Nuclear Physics DE-AC05-06OR23177, Early Career Award to G. Eremeev.
A DC cylin­dri­cal mag­netron sput­ter­ing sys­tem has been com­mis­sioned and op­er­ated to de­posit Nb₃Sn onto 2.6 GHz Nb SRF cav­i­ties. After op­ti­miz­ing the de­po­si­tion con­di­tions in a mock-up cav­ity, Nb-Sn films are de­posited first on flat sam­ples by mul­ti­layer se­quen­tial sput­ter­ing of Nb and Sn, and later an­nealed at 950 °C for 3 hours. X-ray dif­frac­tion of the films showed mul­ti­ple peaks for the Nb₃Sn phase and Nb (sub­strate). No peaks from any Nb-Sn com­pound other than Nb₃Sn were de­tected. Later three 2.6 GHz Nb SRF cav­i­ties are coated with ~1 µm thick Nb₃Sn. The first Nb₃Sn coated cav­ity reached close to Eacc = 8 MV/m, demon­strat­ing a qual­ity fac­tor Q₀ of 3.2 × 108 at Tbath = 4.4 K and Eacc = 5 MV/m, about a fac­tor of three higher than that of Nb at this tem­per­a­ture. Q₀ was close to 1.1 × 109, dom­i­nated by the resid­ual re­sis­tance, at 2 K and Eacc = 5 MV/m. The Nb₃Sn coated cav­i­ties demon­strated Tc in the range of 17.9 ¿ 18 K. Here we pre­sent the com­mis­sion­ing ex­pe­ri­ence, sys­tem op­ti­miza­tion, and the first re­sults from the Nb₃Sn fab­ri­ca­tion on flat sam­ples and SRF cav­i­ties.
 
poster icon Poster TUPTB019 [1.216 MB]  
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-TUPTB019  
About • Received ※ 16 June 2023 — Revised ※ 24 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 10 July 2023
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