RF test on coated resonant cavity

I.FAST Innovation Fostering in Accelerator Science and Technology Horizon 2020 Research Infrastructures GA n° 101004730 DELIVERABLE REPORT RF test on coated resonant cavity DELIVERABLE: D9.2 Document identifier: IFAST-D9.2 Due date of deliverable: End of Month 51 (July 2025, extended to October 25) Report release date: 31/10/2025 Work package: WP9: Innovative superconducting cavities Lead beneficiary: INFN Document status: Final ABSTRACT The goal of D9.2 is to coat and test a resonant cavity with an alternative material to Niobium with a Q0 > 10E9 at 4.2 K and 1.3 GHz. In Task 9.2, two lines of development were carried out to achieve the goal: the first concerning the copper cavities serving as substrates, and the second focusing on the deposition set-ups. For both, alternative solutions had to be identified compared to what was originally foreseen in the proposal, due both to technological challenges that emerged during the R&D phase of task 9.3 and to the loss of key partners. In this document are reported the advancement in seamless Cu cavities production and polishing, the description of the two Nb3Sn coating system designed and built in INFN and UKRI, the protocol adopted for the first 1.3 GHz Nb3Sn cavity coated by PVD in Europe and finally, the SRF performances of Nb3Sn coatings are reported and discussed. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 2 / 23 I.FAST Consortium, 2025 For more information on IFAST, its partners and contributors please see https://ifast-project.eu/ This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 101004730. IFAST began in May 2021 and will run for 4 years. Delivery Slip Name Partner Date Authored by C. Pira R.Valizadeh, O.Malyshev O. Kugeler T. Proslier INFN UKRI HZB CEA 30/09/2025 Reviewed by M. Vretenar, L. Celona [on behalf of Steering Committee] CERN 31/10/2025 Approved by Steering Committee 31/10/2025 RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 3 / 23 TABLE OF CONTENTS 1 Introduction ........................................................................................................................... 4 2 Cavity manufacturing ........................................................................................................... 5 2.1 Copper cavity manufacturing .......................................................................................... 5 2.1.1 1.3 GHz seamless copper cavity production at Piccoli ........................................... 5 2.1.2 Copper cavity polishing at INFN ............................................................................ 6 2.2 Bulk niobium cavity ........................................................................................................ 7 2.2.1 PIPPS I cavity treatments........................................................................................ 7 3 Thin film deposition facilities and deposition process ....................................................... 8 3.1. Deposition facility at INFN ............................................................................................ 8 2.3 Deposition facility at UKRI/STFC ............................................................................... 10 2.4 Deposition process at UKRI/STFC ............................................................................... 11 4 SRF testing ........................................................................................................................... 16 4.1. Results on QPR ............................................................................................................. 16 4.2. Results on Cavity .......................................................................................................... 18 5 Conclusions .......................................................................................................................... 22 6 References ............................................................................................................................ 23 RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 4 / 23 Executive summary This document reports on the RF measurements and developments achieved during the four years of the I.FAST project for the production of the first prototype of a 1.3 GHz Nb3Sn cavity via PVD with deposition parameters compatible with Cu substrates. D9.2 brings together all the results and optimizations for the production of SC thin films developed within the different tasks of WP9. During this work, thanks to the results obtained in previous WP9 deliberations, it was possible to achieve remarkable results that led to advances in all stages of the thin-film SRF cavity production chain. These results place the European laboratories of the I.FAST collaboration in a leadership role within the thin-film SRF community for the development of cavities operating at 4 K. In particular: the production of seamless cavities via spinning has been automated, a new copper polishing technology has been developed and successfully tested, a protocol for the deposition of Nb3Sn coatings via PVD has been developed and tested (current state of the art in the SRF community), two systems for Nb3Sn coating in 1.3 GHz cavities with innovative solutions have been designed and built, the first Nb3Sn cavity has been deposited via PVD. 1 Introduction The objective of Deliverable 9.2, and more generally of WP9, is to produce a resonant cavity coated and tested with an alternative material to Niobium with a Q0 > 10E9 at 4.2 K and 1.3 GHz. At the conclusion of ARIES, Nb₃Sn was identified as the most promising superconducting material to replace Nb and to enable operation at 4.2–4.5 K instead of 2 K. Consequently, Task 9.3 of I.FAST focused on developing a deposition recipe for Nb3Sn on Cu, starting from planar samples and tested on QPR. The results, presented in Deliverables 9.3 [1], 9.6 [2] and [9-14], demonstrate that the recipes developed by INFN and UKRI, measured at HZB, exhibit surface resistance values on the order of tens of nΩ at 400 MHz, which represents the current state of the art at 4.5 K. In Task 9.2, two lines of development were carried out: the first concerning the copper cavities serving as substrates, and the second focusing on the deposition set-ups. For both, alternative solutions had to be identified compared to what was originally foreseen in the proposal, due both to technological challenges that emerged during the R&D phase of task 9.3 and to the loss of key partners. In particular, the impossibility of continuing the collaboration with PTI prevented access to electron-beam welding, which is necessary for welding the flanges to the seamless copper cavities. The developments in Task 9.3 subsequently highlighted that a thick buffer layer of Nb is required to grow Nb₃Sn with a Tc > 17 K. Task 9.3 also revealed major difficulties in cylindrical Nb₃Sn targets production. However, some solutions were adopted to still achieve Deliverable 9.2 by the end of the project. The first solution adopted was to use the Piccoli seamless copper cavities without flanges for prior R&D testing and then a bulk Nb cavity as a substrate to replace the copper one for the final prototype. The second was to develop alternative coating configurations to the traditional cylindrical configuration, thus allowing the use of commercially available planar Nb₃Sn targets. Two different set-ups were explored at INFN and UKRI. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 5 / 23 2 Cavity manufacturing In Task 9.2, two industrial partners were originally involved in copper cavities production: Piccoli Srl (Italy) and PTI (Belarus). Piccoli should be providing seamless copper cavities, while PTI was going to manufacturing copper and niobium cavities by hydroforming as well as to provide an expertise in EB welding for both the cavity produced by PTI and for the flange welding of cavities produced by Piccoli. In 2022 the PTI was excluded from IFAST, and such key expertise was missing for the WP9. The solution adopted was to use the Piccoli seamless copper cavities without flanges for prior R&D testing and then a bulk Nb cavity as a substrate to replace the copper one for the final prototype. 2.1 COPPER CAVITY MANUFACTURING INFN, in collaboration with Piccoli Srl, aims to improve the quality of seamless Cu cavity production, in particular the reproducibility, by using numerically controlled machines instead of traditional semi-automatic lathes used up to now. Efforts are also being made to reduce surface defects by studying the effect of annealing temperature and evaluate new strategies for reducing cold work stress. Full details on the definition of the process parameters are reported in I.FAST M38 Report [3]. A total of 10 optimized Cu seamless cavities have been produced by Piccoli in the entire project. 5 cavities have been polished by INFN and used for coating tests in task 9.2 and task 9.5 [4]. 2.1.1 1.3 GHz seamless copper cavity production at Piccoli The Cu cavities were produced from 3 mm thick OFE Cu sheets. The process consists of 4 stages and the annealing temperature of 400 °C was defined during the development phase described in I.FAST M38 Report [3]. The cavities produced do not have flanges for vacuum sealing, as they are used for coating tests. However, some cavities have a lip that can be used with an adapter and indium gasket. A test was also performed on the mechanical strength of the cavity after annealing at temperatures between 600 and 650 °C, which are defined as optimal for the Nb3Sn coating process (see I.FAST D9.3). The test highlighted the possibility of cavity collapse during the pumping phase, which can be avoided with appropriate supports, as shown in Figure 1. This problem is not a limitation to the production of the first prototypes to demonstrate the performance of Nb3Sn coatings, but it must certainly be taken into account in the next stages of development to ensure the correct tunability of the cavities. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 6 / 23 Figure 1: From left to right: cavity collapsed after heat treatment at 650°C, cavity mechanical supported that passed the anneling test, cavity lip. 2.1.2 Copper cavity polishing at INFN PROJECT SUBSTRATES The copper cavities used in this project were all polished at LNL using the SUBU chemical polishing technique, tested in ARIES [5]. The protocol used is as follows: • Degreasing: in NGL 1740 bath • Activation in sulfamic acid (H3NO3S, 5 g/l) • Chemical polishing in "SUBU5" solution • Pre-rinsing with acid: samples immersed in sulfamic acid (H3NO3S, 5 g/l) • Rinsing with water: samples immersed in demineralized water • Spraying with alcohol to enhance drying • Drying with Nitrogen PLASMA ELECTROLYTIC POLISHING RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 7 / 23 Figure 2: First cavity polished by PEP. On the 3 pictures on the left the cavity during the insertion in the chemical bath, the surface after the polishing process. The black cover is used to force the polishing only in the internal surface, preventing the polishing of the external surface. On the right the removal rate in function of the cavity position. In parallel, in synergy with the INFN ESPP project “SRF R&D for FCC-ee,” the applicability of the PEP process to 1.3 GHz copper cavities was studied. Compared to traditional treatments, it offers removal speeds that are 10 times faster and has a lower environmental impact. For the first time, a 1.3 GHz cavity was entirely polished using PEP technology with a good uniformity if we exclude the initial cut-off part (Figure 2). The results obtained are extremely promising, and the study will continue by evaluating the implementation of this technique in the FCC-ee cavity production protocol. More information in [8]. 2.2 BULK NIOBIUM CAVITY Three bulk niobium cavities have been received from UKRI, along with one pair of flanges with mounted coupler and pick-up antennas. The two remaining pairs are expected to be shipped before the end of 2025. The Nb cavity I has been treated with HPR + flanges mounting and leak testing at CEA. Nb cavity II and Nb cavity III will be electropolished, annealed in high vacuum, HPR and leak tested prior to sending them back to UKRI. 2.2.1 PIPPS I cavity treatments The Nb cavity I has received the following treatments in the class 4 clean room: - HPR for 1 hrs (2 cycles), drying overnight. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 8 / 23 - Leak tested with flanges and gaskets provided by UKRI: a leak was detected during the test. - HPR again for 1 hrs (2 cycles), drying overnight. - Leak tested again with flanges from UKRI and new gaskets and nuts from CEA: no leak detected. - Shipment back to UKRI with cavity under vacuum. Treatment of the remaining two cavities is scheduled for November 2025. 3 Thin film deposition facilities and deposition process The results of D9.3 provided the requirements for the PVD system to be designed and built for the deposition of Nb3Sn coatings on Cu. In particular, the system must operate in UHV at temperatures of 700°C. Another requirement from task 9.3 is that it is currently impossible to use cylindrical Nb3Sn targets due to difficulties encountered in their development. Therefore, a source capable of using planar targets, which can be obtained by sintering and are therefore available on the market, must be designed. Two deposition facilities were designed, one at INFN and one at UKRI. The two setups differ radically. INFN opted for a rectangular magnetron covering the entire length of the cavity, designed specifically for this system. The coating is made uniform by rotating the cavity. UKRI, on the other hand, has created a configuration with two standard circular planar magnetrons that move along the axial axis of the cavity to uniform the deposition thickness. The INFN configuration has the advantage of ensuring, in principle, better control of thickness uniformity, but the rectangular magnetron required a long design and testing time. The UKRI configuration, however, using standard planar magnetrons, has the advantage of being a set-up that is more versatile and quicker to build, ensuring the first deposition of 1.3 GHz cavities within the project timeline. 3.1. DEPOSITION FACILITY AT INFN The setup (Figure 3) consists of a single vertical chamber, designed such that both the process gas injection and the diagnostic measurements occur at the bottom. The chamber is housed within an ITEM rack structure. Vacuum is achieved through a combination of a primary scroll pump and a turbomolecular pump. The baking system employs DC-powered heating bands wrapped around the chamber. Before processing after the baking phase, the pressure inside the chamber reaches values in the range of 10E-9 mbar. The 1.3 GHz cavity is mounted on a dedicated support structure designed to ensure mechanical stability at the high temperatures required for Nb3Sn sputtering. To ensure proper alignment of the support axis—and consequently of the cavity itself—four stainless steel rods are inserted into the chamber, serving as centering guides for the support. The sputtering source consists of a rectangular, balanced magnetron (Figure 4) inserted into the cavity from the bottom of the chamber. This design allows for easy handling, particularly during installation and replacement. The baseplate supporting the target features an internal housing with RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 9 / 23 a dual function: continuous water flow for cooling, and accommodation of magnets, which can be configured in three different arrangements with different magnetic field intensity. Magnetic confinement can be adjusted by physically replacing the magnets, allowing for flexible composition and field control. The target has a total surface area of 120 cm2 and thickness can be 3 or 5 mm. Two main technical challenges were successfully addressed in system design. First, the magnetron must be inserted into the cavity through the cut-offs, requiring it to fit within a diameter of 76 mm. Second, precise alignment between the cavity’s rotational axis and the magnetron’s symmetry axis is essential. This alignment is ensured by a 50 μm ferromagnetic UHV bearing, which enables cavity rotation, and a standard DN100CF flange, which secures the magnetron in a fixed position. Two materials are under testing for the baseplate: copper and aluminum to keep the weight reasonably low. Figure 3: From left to right: scheme of deposition system, picture of the deposition system at INFN, Al and Cu Rectangular Magnetron mounted. The magnetron has been tested and characterized by I-V curve with the medium magnetic pack configuration. An image in Figure 4 is demonstrating the plasma produced by the magnetron source in the classical rectangular planar configuration and the I-V experimental curve that present a quadratic behaviour as described by Westwood [5]. The first tests on samples in this innovative configuration have begun, and the deposition of the first 1.3 GHz cavity at INFN is expected in the first half of 2026. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 16 / 23 flanges and filled with dry nitrogen to 3 bar. A complete description of the coating system and cavity coating protocol is available in [15]. One of the two targets used shows areas of excessive erosion along the race-track at the end of the process (Figure 14), which have partially exposed the copper baseplate with possible contamination of the Nb3Sn coating (to be analyzed). Figure 14: Nb3Sn target after the cavity coating. Along the race-track, areas where erosion has completely consumed the target are visible. 4 SRF testing 4.1. RESULTS ON QPR The recipes for sputtering Nb3Sn onto Cu via PVD developed in task 9.3 by INFN and UKRI were tested on planar quadrupoles (QPR) at a frequency of 400 MHz before being applied to the 1.3 GHz elliptical cavities. The QPR substrate is Nb, so as to evaluate only the effect of the Nb3Sn coating, leaving aside for the moment the contribution of the Cu substrate. The results are reported in D9.6. For convenience, we also report them here in Error! Reference source not found.. It can be seen that both samples at operating temperatures of 4.0 and 4.5 K have surface resistance (Rs) values below 100 nΩ up to fields of 30 mT RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 17 / 23 Figure 15: QPR sample surface resistance vs peak field on sample at different cooldown velocities. Left: INFN sample. Right: UKRI sample. In particular, the INFN sample has a surface resistance is lower than that of the state-of-the-art Vapor Tin Diffusion measured under the same conditions up to 30 mT. Two new QPRs have been deposited in INFN: one on a copper substrate to test the effect of the substrate on surface resistance (awaiting RF testing at HZB) and one deposited on an Nb bulk substrate to evaluate the reproducibility of the coating's performance. The second QPR presents performance even better than the previous one: Rs<9 nΩ at 20 mT and 4 K. If we convert Rs into quality factor and magnetic field into accelerating field (Figure 16), we can compare these results with the performance of the Nb on Cu cavities of LHC. We can see how the Nb3Sn coating allows Quality Factors a order of magnitude higher than those of Nb to be achieved and performance that potentially overcome the requirements of FCC-ee. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 18 / 23 Figure 16: INFN QPR sample data converted in Q VS Eacc curve and compared with LHC cavities and FCC-ee 2 cell performance target [13]. 4.2. RESULTS ON CAVITY The first vertical cavity RF test was performed at HZB on a TESLA type Nb cavity from CEA sputtered with Nb3Sn at STFC, as described in the previous chapter. For the initial characterization this cavity had been equipped with a fixed antenna aiming at an external Q value of 10E10 optimistically assuming Q values of more than 10E10 which have been demonstrated in cavities coated by liquid tin diffusion. The pickup antenna had a one order of magnitude larger Q value. Upon reception the cavity was continuously handled under clean room conditions and pumped and vented with particle-free pump stands. For extended diagnostics during cryogenic testing, the cavity was equipped with five temperature sensors arranged along the cavity axis: two at the upper beam tube, two at the lower beam tube and one at the equator. Two fluxgate sensors were mounted near the cavity equator, one pointing in axial direction (sensitive to expulsion of the dominant remnant field), and one in azimuthal direction (sensitive to fields generated by thermal currents). The top and bottom flange of the cavity were equipped with cartridge heaters in order to enable manipulation of the temperature differences along the cavity axis during the superconducting transition, see Figure 17Error! Reference source not found.. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 19 / 23 Figure 17: Labelled photo of the cavity in the insert before mounting in the cryostat During cooldown great care was taken to keep the temperature gradient along the cavity axis small. This was done by manually adjusting the valve settings of the cryostat and was reasonably successful and no thermocurrents were recorded with the azimuthally placed sensors, see Figure 18 and Figure 19. The cavity made a first superconducting transition at 17 K. This could be clearly seen as a drop in bandwidth in S21 measurements of the antennae that were performed parallel to the cooling procedure. At the same time, since no magnetic field change was observed at the vertical sensor at 17 K either, it is reasonable to assume that 100% flux pinning of the remnant external magnetic field has occurred. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 20 / 23 Figure 18: Temperature progression over cavity near Tc Figure 19: Magnetic field monitored at the cavity equator during initial cooldown Once at 1.8K, it was possible to apply a field inside the cavity, but unfortunately, the stored energy was not high enough that a sufficient signal-to-noise ratio of the outgoing power signal for a successful tau or much less beta extraction could be obtained. A network analyzer based beta measurement yielded small dots in the polar plot of S11 and S22 measurements, confirming the assumption of strong undercoupling (which cannot be quantified). It can be concluded that the loaded quality factor is dominated by Q0, hence, no Q vs E curve was obtained. Figure 20 shows results from monitoring the S21 of the cavity during warmup. From these measurements the progression of resonant frequency and the bandwidth (3dB point) over time (where the passed time corresponds to the temperature increase) are extracted. While the Tc of the film was unusually high at 18.1 K this did not help with the RF surface resistance since the superconducting bandwidth is only two orders of magnitude higher than the normal conducting one. The reason for this poor performance despite the high Tc could be copper contamination of the film during the final preparation step. To verify this, it is intended to repeat the measurement after a cleaning step with a mixture of nitric acid and phosphoric acid which has been successfully used for bronze route samples. In parallel, we will perform an HPR on the cavity and equip it with an adjustable input coupler allowing for smaller Q values. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 21 / 23 Figure 20: Left plot: Progression of frequency and cavity temperature over time during final warmup. Frequency values were obtained from a S21 measurement taken with a network analyser. Right plot: Frequency and loaded quality factor vs temperature. QL was extracted using a Lorentzian fit. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 22 / 23 5 Conclusions The work carried out to achieve deliverable 9.2 has resulted in six remarkable outcomes: 1. Piccoli Srl, in collaboration with INFN, has developed a new semi-automated protocol for the manufacture of seamless Cu cavities via CNC. 2. A new surface treatment based on Plasma Electrolytic Polishing has been developed. Compared to traditional treatments, it offers removal speeds that are 10 times faster and has a lower environmental impact. 3. Two new facilities optimized for Nb3Sn coating via PVD have been designed and built at INFN and UKRI. 4. Innovative magnetron source is under testing at INFN. 5. UKRI define a deposition protocol for 1.3 GHz cavity and coat successfully the first cavity with Nb3Sn. The measured value of Tc ~18 K is an index of the optimal composition and phase of the Nb3Sn coating. The cause of unexpectedly low Q is under further investigation beyond IFAST project. 6. The results obtained from QPR RF test at 400 MHz are currently state-of-the-art for Nb3Sn films produced via PVD. These results position the I.FAST collaboration as an international reference for the development of Nb3Sn films on Cu and, more generally, for the development of accelerator cavities operating at 4 K. RF TEST ON COATED RESONANT CAVITY Deliverable: D9.2 Date: 31/10/2025 Grant Agreement 101004730 PUBLIC 23 / 23 6 References [1] I.FAST WP9 members. (2025). First 6 GHz cavity coated and characterised. I.FAST D9.3 Deliverable Report. Zenodo. https://doi.org/10.5281/zenodo.16677760 [2] I.FAST WP9 members. (2025). Test of thin-film samples. I.FAST D9.6 Deliverable Report. Zenodo. https://doi.org/10.5281/zenodo.14905673 [3] I.FAST WP9.2 members. (2022). First seamless copper 1.3GHz cavity produced as substrate for the coating of the SC film. I.FAST MS38 Milestone Report. Zenodo. https://doi.org/10.5281/zenodo.6979934 [4] I.FAST WP9 members. (2025). 1.3 GHz Nb-coated cavity irradiated by laser in argon atmosphere and RF tested. I.FAST D9.5 Deliverable Report. Zenodo. https://doi.org/10.5281/zenodo.16419102 [5] ARIES WP15 members. (2018). Evaluation of cleaning process . ARIES D15.1 Deliverable Report. https://edms.cern.ch/document/1820617/1.0 [6] W. D. Westwood, et al.; The current‐voltage characteristic of magnetron sputtering systems. J. Appl. Phys. 1 December 1983; 54 (12): 6841-6846. https://doi.org/10.1063/1.332006 List of Task 9.2 publications [7] D. Dorothea et al., “Recipe Optimization and SRF Test of Cu-compatible Nb3Sn Films by DC Magnetron Sputtering from a Stoichiometric Target”. Preprint DOI: https://doi.org/10.21203/rs.3.rs-7516819/v1 [8] E. Chyhyrynets et al., “Plasma electrolytic polishing of 1.3 GHz cavities”, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [9] D. Fonnesu et al., “Influence of the Coating Parameters on the Tc of Nb₃Sn Thin Films on Copper Deposited via DC Magnetron Sputtering”, in Proc. 21th Int. Conf. RF Supercond. (SRF'23), Grand Rapids, MI, USA, Jun. 2023, pp. 92-95. doi:10.18429/JACoW-SRF2023MOPMB013 [10] C. Pira et al., “Progress in European Thin Film Activities”, in Proc. 21th Int. Conf. RF Supercond. (SRF'23), Grand Rapids, MI, USA, Jun. 2023, pp. 607-614. doi:10.18429/JACoWSRF2023-WECAA01 [11] N. Leicester et al., “Development of a 1.3 GHz RF research cavity for use in testing of superconducting thin films”, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [12] M. Lazzari et al., “Development of a new system for Nb₃Sn thin film deposition on 1.3 GHz cavities”, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [13] D. Fonnesu et al., “Development of Nb3Sn coatings on copper at INFN-LNL”, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [14] C. Benjamin et al., “Optimisation of Nb3Sn Thin Films for SRF Applications at Daresbury Laboratory”, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [15] R. Valizadeh et al., “Results of 1.3 GHz Nb cavity coated with Nb3Sn thin film deposition by PVD magnetron sputtering, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025. [16] O.Malyshev, C. Antoine, et al., Thin-Film SRF Roadmap Report, in Proc. 22th Int. Conf. RF Supercond. (SRF'25), Tokyo, Japan, 2025.