TUOXSP —  Contributed Orals: Accelerator Technology   (14-Jun-22   09:30—10:30)
Chair: T. Pulampong, SLRI, Nakhon Ratchasima, Thailand

Paper	Title	Page
TUOXSP1	Origin and Mitigation of the Beam-Induced Surface Modifications of the LHC Beam Screens	780
	V. Petit, P. Chiggiato, M. Himmerlich, S. Marinoni, H. Neupert, M. Taborelli, L.J. Tavian CERN, Meyrin, Switzerland
	All over Run 2, the LHC beam-in­duced heat load on the cryo­genic sys­tem ex­hib­ited a wide scat­ter­ing along the ring. Stud­ies as­cribed the heat source to elec­tron cloud build-up, in­di­cat­ing an un­ex­pected high Sec­ondary Elec­tron Yield (SEY) of the beam screen sur­face in some LHC re­gions. The inner cop­per sur­face of high and low heat load beam screens, ex­tracted dur­ing the Long Shut­down 2, was analysed. On the low heat load ones, the sur­face was cov­ered with the na­tive Cu2O oxide, while on the high heat load ones CuO dom­i­nated at sur­face, and it ex­hib­ited a very low car­bon cov­er­age. Such chem­i­cal mod­i­fi­ca­tions in­crease the SEY and in­hibit a proper con­di­tion­ing of the af­fected sur­faces. Fol­low­ing this char­ac­ter­i­sa­tion, the mech­a­nisms for CuO build-up in the LHC beam pipe were in­ves­ti­gated on a newly com­mis­sioned cryo­genic sys­tem al­low­ing elec­tron ir­ra­di­a­tion, sur­face chem­i­cal char­ac­ter­i­sa­tion by X-ray Pho­to­elec­tron Spec­troscopy and SEY mea­sure­ments on sam­ples held below 15 K. In par­al­lel, cu­ra­tive so­lu­tions against the pres­ence of CuO in the LHC beam screens were ex­plored, which could be im­ple­mented in-situ to re­cover a proper con­di­tion­ing and lower the beam-in­duced heat load.
	Slides TUOXSP1 [2.669 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP1
About •	Received ※ 17 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)
TUOXSP2	Analysis of Low RRR SRF Cavities	783
SUSPMF110	use link to see paper's listing under its alternate paper code
	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. This work was supported by the University of Chicago. Re­cent find­ings in the su­per­con­duct­ing ra­dio-fre­quency (SRF) com­mu­nity have shown that in­tro­duc­ing cer­tain im­pu­ri­ties into high-pu­rity nio­bium can im­prove qual­ity fac­tors and ac­cel­er­at­ing gra­di­ents. Suc­cess has been found in ni­tro­gen-dop­ing, dif­fu­sion of the na­tive oxide into the nio­bium sur­face, and thin films of al­ter­nate su­per­con­duc­tors atop a nio­bium bulk cav­ity. 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 with a low resid­ual re­sis­tance ratio (RRR) and cor­re­late these im­pu­ri­ties with the RF per­for­mance of low RRR cav­i­ties so that the mech­a­nism of re­cent im­pu­rity-based im­prove­ments can be bet­ter un­der­stood and im­proved upon. Ad­di­tion­ally, we per­form a low tem­per­a­ture bake on the low RRR cav­ity to eval­u­ate how the in­ten­tional ad­di­tion of oxy­gen to the RF layer af­fects per­for­mance. We have found that low RRR cav­i­ties ex­pe­ri­ence low tem­per­a­ture-de­pen­dent BCS re­sis­tance be­hav­ior more promi­nently than their high RRR coun­ter­parts. The re­sults of this study have the po­ten­tial to un­lock a new un­der­stand­ing on SRF ma­te­ri­als.
	Slides TUOXSP2 [1.495 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP2
About •	Received ※ 08 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 25 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)
TUOXSP3	Evaluation of Geometrical Precision and Surface Roughness Quality for the Additively Manufactured Radio Frequency Quadrupole Prototype	787
	T. Torims, D. Krogere, G. Pikurs, A. Ratkus Riga Technical University, Riga, Latvia A. Cherif, M. Vretenar CERN, Meyrin, Switzerland N. Delerue Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France M. Foppa Pedretti, M. Pozzi Rösler Italiana s.r.l., Concorezzo, Italy S. Gruber, E. Lopez Fraunhofer IWS, Dresden, Germany T. Otto TalTech, Tallinn, Estonia M. Thielmann, P. Wagenblast TRUMPF, Ditzingen, Germany M. Vedani POLIMI, Milano, Italy
	A mul­ti­dis­ci­pli­nary col­lab­o­ra­tion within the I.​FAST pro­ject teamed-up to de­velop ad­di­tive man­u­fac­tur­ing (AM) tech­nol­ogy so­lu­tions for ac­cel­er­a­tors. The first pro­to­type of an AM pure-cop­per radio fre­quency quadru­pole (RFQ) has been pro­duced, cor­re­spond­ing to 1/4 of a 4-vane RFQ*. It was op­ti­mised for pro­duc­tion with state-of-the-art laser pow­der bed fu­sion tech­nol­ogy. Geo­met­ri­cal pre­ci­sion and rough­ness of the crit­i­cal sur­faces were mea­sured. Alt-hough the ob­tained val­ues were be­yond stan­dard RFQ spec­i­fi­ca­tions, these first re­sults are promis­ing and con-firmed the fea­si­bil­ity of AM man­u­fac­tured com­plex cop-per ac­cel­er­a­tor cav­i­ties. There­fore, fur­ther post-pro­cess­ing tri­als have been con­ducted with the sam­ple RFQ to im-prove sur­face rough­ness. Al­go­rithms for the AM techno-log­i­cal processes have also been im­proved, al­low­ing for higher geo­met­ri­cal pre­ci­sion. This re­sulted in the de­sign of a full 4-vane RFQ pro­to­type. At the time of the paper sub­mis­sion the full-size RFQ is being man­u­fac­tured and will un­dergo through the strin­gent sur­face qual­ity meas-ure­ments. This paper is dis­cussing novel tech­no­log­i­cal de­vel­op­ments, is pro­vid­ing an eval­u­a­tion of the ob­tained sur­face rough­ness and geo­met­ri­cal pre­ci­sion as well as out­lin­ing the po­ten­tial post-pro­cess­ing sce­nar­ios along with fu­ture tests plans. * Torims T, et al. First Proof-of-Concept Prototype of an Additive Manufactured Radio Frequency Quadrupole. Instruments. 2021; 5(4):35. https://doi.org/10.3390/instruments5040035
	Slides TUOXSP3 [10.031 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUOXSP3
About •	Received ※ 20 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 10 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)