Nitrogen doping with dual-vacuum furnace at IHEP

Liu, Baiqi; Sha, Peng; Dong, Cao; He, Feisi; Pan, Weimin; Mi, Zhenghui; Zhai, Jiyuan; Jin, Song; Dai, Jin; Li, Zhongquan; Du, Lei; Wang, Fei; Sun, Liangrui; Ge, Rui

doi:10.1016/j.nima.2021.165080

Cited by 10 publications

(7 citation statements)

References 5 publications

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“…This indicates that the slight-doping of Y can slightly increase the T c of Nb, which is consistent with previous results [52], and the operation temperature of SRF applications using the new alloy is guaranteed. The very steep magnetization transitions in figure 1 S4) [18]. This may be attributed to the slight doping of Y and the increase in impurity scattering.…”

Section: Resultsmentioning

confidence: 92%

“…Up to now, Nb is still regarded as the most promising material for manufacturing the SRF cavities due to its relatively high critical temperature [2,17], rather high lower-critical field B c1 [2,9], large superfluid density among all the element or alloy superconductors, and the high residual resistivity ratio (RRR) [2,18]. Meanwhile, its high ductility allows for easy manufacturing.…”

Section: Introductionmentioning

confidence: 99%

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Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity

Xie

Wang

Fan

et al. 2023

Supercond. Sci. Technol.

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The research of high energy and nuclear physics needs high power accelerators, and the superconducting radio-frequency (SRF) cavity is regarded as the engine of them. Up to now, the widely used practical and effective material for making the SRF cavity is pure Nb. The key parameter that governs the efficiency and the accelerating field (Eacc) of a SRF cavity is the lower critical field Hc1. Here we report a significant improvement of Hc1 of a new type of alloy, Nb1-xYx fabricated by arc melting technique. Experimental investigations with multiple tools including x-ray diffraction, scanning electron microscopy, resistivity and magnetization are carried out, showing that the samples have good quality and a 30-60% enhancement of Hc1. First principle calculations indicate that this improvement is induced by the delicate tuning of a Lifshitz transition of a Nb derivative band near the Fermi energy, which increases the Ginzburg-Landau parameter and Hc1. Our results may trigger a replacement of the basic material and thus a potential revolution for manufacturing the SRF cavity.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity

Xie

Wang

Fan

et al. 2023

Supercond. Sci. Technol.

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“…The nitrogen doping treatment of niobium samples was carried out in a dual-vacuum furnace [22] with a background pressure of 3.0×10 −7 Pa. Before nitridation, the samples were outgassed for 3 h at 950 ℃ in a vacuum of 10 −4 Pa. After degassing, the temperature in the furnace dropped rapidly to 800 ℃ and the samples were kept at this temperature for 3 min in nitrogen atmosphere of about 3.5 Pa (∼26 mTorr) with a total ventilatory capacity of 4.26 ml. After 3 min nitrogen injection, the samples were annealed for another 1 h at 800 ℃ with a pressure of 10 −5 Pa.…”

Section: Sample Preparationmentioning

confidence: 99%

Investigation into surface composition of nitrogen-doped niobium for superconducting RF cavities

Yang¹,

Liu²,

Ye³

et al. 2021

Nanotechnology

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Systematic analysis of the surface morphology, crystalline phase, chemical composition and elemental distribution along depth for nitrogen-doped niobium was carried out using different methods of characterization, including Scanning Electron Microscopy (SEM), Atomic-Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS) and layer-by-layer X-ray Photoelectron Spectroscopy (XPS) analysis. The results showed that, after nitrogen doping, the surface was covered by densely distributed trigonal precipitates with an average crystallite size of 32 ± 8 nm, in line with the calculation result (29.9 nm) of nitrogen-enriched β-Nb2N from GIXRD, demonstrating the phase composition of trigonal precipitates. The depth analysis through RBS and XPS indicated that β-Nb2N was dominant in the topmost 9.7 nm and extended to a depth of 575 nm, with gradually decreased content. In addition, the successive change along depth in the naturally oxidized states of niobium after nitrogen doping, was revealed. It was interesting to find that the oxygen diffusion depth could be moderately enhanced by the nitridation process. These results established the near-surface phase composition of nitrided niobium, which is of great significance in evaluating the effect of nitrogen doping and further understanding the Q improvement of the superconducting radio frequency cavities.

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“…Recently, the technology of medium-temperature (mid-T, 250-400 • C) baking is used to increase Q 0 of 1.3 GHz cavities successfully, which dissolves the oxides in the surfaces of niobium [1][2][3]. It is more convenient and easier than nitrogen doping/infusion [4][5][6]. At the Fermi National Accelerator Laboratory (FNAL), the 1.3 GHz single-cell cavity was evacuated with pump and received mid-T baking at 300 • C in an oven.…”

Section: Introductionmentioning

confidence: 99%

Quality Factor Enhancement of 650 MHz Superconducting Radio-Frequency Cavity for CEPC

et al. 2022

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Medium-temperature (mid-T) furnace baking was conducted at 650 MHz superconducting radio-frequency (SRF) cavity for circular electron positron collider (CEPC), which enhanced the cavity unloaded quality factor (Q0) significantly. In the vertical test (2.0 K), Q0 of 650 MHz cavity reached 6.4 × 1010 at 30 MV/m, which is remarkably high at this unexplored frequency. Additionally, the cavity quenched at 31.2 MV/m finally. There was no anti-Q-slope behavior after mid-T furnace baking, which is characteristic of 1.3 GHz cavities. The microwave surface resistance (RS) was also studied, which indicated both very low Bardeen–Cooper–Schrieffer (BCS) and residual resistance. The recipe of cavity process in this paper is simplified and easy to duplicate, which may benefit the SRF community.

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Nitrogen doping with dual-vacuum furnace at IHEP

Cited by 10 publications

References 5 publications

Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity

Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity

Investigation into surface composition of nitrogen-doped niobium for superconducting RF cavities

Quality Factor Enhancement of 650 MHz Superconducting Radio-Frequency Cavity for CEPC

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