Superconductivity in high energy particle accelerators

Schmüser, Peter

doi:10.1016/s0146-6410(02)00145-x

Cited by 28 publications

(17 citation statements)

References 38 publications

(61 reference statements)

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“…The impact of bulk resistivity and other, surface or intergranular oxide-specific mechanisms such as TLS, on microwave loss is determined by the field penetration into the film and can be described by an effective surface resistance [14]. Seminal studies of radiofrequency cavities with superconducting Nb walls have shown that residual surface resistance limits the cavity quality factor at low temperatures [53][54][55][56][57] . Our finding that RRR correlates ) to a single peak (suboxides) to a negligible peak (metal).…”

Section: Discussionmentioning

confidence: 99%

Microscopic relaxation channels in materials for superconducting qubits

et al. 2021

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Despite mounting evidence that materials imperfections are a major obstacle to practical applications of superconducting qubits, connections between microscopic material properties and qubit coherence are poorly understood. Here, we combine measurements of transmon qubit relaxation times (T1) with spectroscopy and microscopy of the polycrystalline niobium films used in qubit fabrication. By comparing films deposited using three different techniques, we reveal correlations between T1 and intrinsic film properties such as grain size, enhanced oxygen diffusion along grain boundaries, and the concentration of suboxides near the surface. Qubit and resonator measurements show signatures of two-level system defects, which we propose to be hosted in the grain boundaries and surface oxides. We also show that the residual resistance ratio of the polycrystalline niobium films can be used as a figure of merit for qubit lifetime. This comprehensive approach to understanding qubit decoherence charts a pathway for materials-driven improvements of superconducting qubit performance.

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Section: Discussionmentioning

confidence: 99%

Microscopic relaxation channels in materials for superconducting qubits

et al. 2021

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“…This type of cavity accelerates particles with an electric field that switches sign at a radio frequency (RF). The length of each cell is designed to be half of the RF wavelength, the elliptical shape of the cells has been optimized to prevent multipacting, and the number of cells has been optimized to provide efficient particle acceleration while maintaining production and tuning feasibility [4]. Niobium is the current material of choice for SRF cavities because it has both favorable superconducting properties [5] and is highly malleable.…”

Section: Fundamentalsmentioning

confidence: 99%

“…R BCS is a function of a superconductor's material properties, the radio frequency, and temperature. R res results from defects, impurities in the superconductor, and impurities on the surface, and is typically 3 nΩ or larger [4]. The surface resistance is inversely proportional to the cavity's quality factor, Q o .…”

Section: Fundamentalsmentioning

confidence: 99%

Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

Ford

2013

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Insights to the fundamental processes that occur during the manufacturing of niobium superconducting radio-frequency (SRF) cavities are provided via analyses of density functional theory calculations and Raman, infrared, and nuclear magnetic resonance (NMR) spectra. I show that during electropolishing fluorine is bound and released by the reaction of the acid components in the solution: HF + H 2 SO 4 <−> HFSO 3 + H 2 O. This result implies that new recipes can possibly be developed on the principle of controlled release of fluorine by a chemical reaction. I also show that NMR or Raman spectroscopy can be used to monitor the free fluorine when polishing with the standard electropolishing recipe.Density functional theory was applied to calculate the properties of common processing impurities -hydrogen, oxygen, nitrogen, and carbon -in the niobium. These impurities lower the superconducting transition temperature of niobium, and hydride precipitates are at best weakly superconducting. I modeled several of the niobium hydride phases relevant to SRF cavities, and explain the phase changes in the niobium hydrogen system based on the charge transfer between niobium and hydrogen and the strain field inside of the niobium. I also present ACKNOWLEDGEMENTS 5LIST OF ACRONYMS AND SYMBOLS 7 TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES 1. INTRODUCTION 2. BACKGROUND Superconducting Radio-Frequency Cavity Design and Material Fundamentals Impurities in Niobium Superconducting Radio-Frequency Cavity Processing Superconducting Radio-Frequency Cavity Performance Limitations 3. METHODS Calculations Based on Density Functional Theory Experimental Tools 4. ELECTROPOLISHING SOLUTION ANALYSES Abstract Introduction Methods Results Raman Spectra Infrared Spectra Nuclear Magnetic Resonance Spectra Discussion

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“…Fig. 5 shows the critical surface for superconducting cables made of NbTi [18]. The shaded surface indicates the 4.5 K operating point for NbTi superconducting material used in most other accelerator applications which is clearly incompatible with an operating magnet field of 8.3 T (no margin left for a significant current density J in the superconducting cables).…”

Section: Magnet Design Aspectsmentioning

confidence: 99%

The large hadron collider

Brüning

Burkhardt

Myers

2012

Progress in Particle and Nuclear Physics

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The Large Hadron Collider (LHC) is the world's largest and most energetic particle collider. It took many years to plan and build this large complex machine which promises exciting, new physics results for many years to come. We describe and review the machine design and parameters, with emphasis on subjects like luminosity and beam conditions which are relevant for the large community of physicists involved in the experiments at the LHC. First collisions in the LHC were achieved at the end of 2009 and followed by a period of a rapid performance increase. We discuss what has been learned so far and what can be expected for the future. AbstractThe Large Hadron Collider (LHC) is the world's largest and most energetic particle collider. It took many years to plan and build this large complex machine which promises exciting, new physics results for many years to come. We describe and review the machine design and parameters, with emphasis on subjects like luminosity and beam conditions which are relevant for the large community of physicists involved in the experiments at the LHC. First collisions in the LHC were achieved at the end of 2009 and followed by a period of a rapid performance increase. We discuss what has been learned so far and what can be expected for the future.

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Superconductivity in high energy particle accelerators

Cited by 28 publications

References 38 publications

Microscopic relaxation channels in materials for superconducting qubits

Microscopic relaxation channels in materials for superconducting qubits

Insights to Superconducting Radio-Frequency Cavity Processing from First Principles Calculations and Spectroscopic Techniques

The large hadron collider

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