A5047356504- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Physics of Superconductivity and Magnetism
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Muon and positron interactions and applications
- Magnetic confinement fusion research
- Nuclear Physics and Applications
- Superconductivity in MgB2 and Alloys
- Plasma Diagnostics and Applications
- Quantum, superfluid, helium dynamics
- Spacecraft and Cryogenic Technologies
- Metal and Thin Film Mechanics
- Magnesium Alloys: Properties and Applications
- Atomic and Subatomic Physics Research
- Semiconductor materials and devices
- Particle Detector Development and Performance
- Hydrogen Storage and Materials
- Graphite, nuclear technology, radiation studies
- Acoustic Wave Resonator Technologies
- Copper Interconnects and Reliability
- Advanced Thermodynamic Systems and Engines
- Astronomical Observations and Instrumentation
- Atomic and Molecular Physics
- Advanced Radiotherapy Techniques
University of Victoria
2019-2024
TRIUMF
2016-2024
University of British Columbia
2023
Simon Fraser University
2023
Cockcroft Institute
2017-2020
Lancaster University
2017-2020
Daresbury Laboratory
2020
Helmholtz-Zentrum Berlin für Materialien und Energie
2016-2019
European Organization for Nuclear Research
2010-2015
Max Planck Institute for Nuclear Physics
2009-2012
In a recent Letter by Romanenko et al., 1 the authors used lowenergy muon spin rotation (LE-lSR) 2,3 to measure Meissner screening profile in cutouts from Nb superconducting radio frequency (SRF) cavities, systematically comparing how different surface treatments affect properties of elemental type-II superconductor.They reported "strong" modification character upon mild baking at 120 C for 48 h, 4 which was interpreted as depth-dependent carrier mean-free-path resulting "gradient vacancy...
We report depth-resolved measurements of the Meissner screening profile in several surface-treated Nb samples using low-energy muon spin rotation (LE-$\mu$SR). In these experiments, implanted positive muons, whose stopping depths below Nb's surface were adjusted between ~10 nm to ~150 nm, reveal field distribution inside superconducting element via their spin-precession (communicated through radioactive decay products). compare how is modified by different treatments commonly employed...
A new high field spectrometer has been built to extend the capabilities of $\beta$-detected nuclear magnetic resonance ($\beta$-NMR) facility at TRIUMF. This beamline extension allows $\beta$-NMR spectroscopy be performed with fields up 200 mT parallel a sample's surface (perpendicular ion beam), allowing depth-resolved studies local electromagnetic spin polarized probes much higher applied than previously available in this configuration. The primary motivation and application is allow...
Muon spins precess in transverse magnetic fields and emit a positron preferentially the spin direction at instant of decay, enabling muon rotation ( μ SR) as precise probe local matter. SR has been used to characterize superconducting radio-frequency (SRF) materials since 2010. At TRIUMF, beam 4.2 MeV + is implanted material-dependent depth approximately 150 m. A dedicated spectrometer was developed measure field first vortex penetration pinning strength SRF parallel up 300 mT. low-energy...
The performance of superconducting radiofrequency (SRF) cavities used for particle accelerators depends on two characteristic material parameters: field first flux entry ${H}_{\text{entry}}$ and pinning strength. former sets the limit maximum achievable accelerating gradient, while latter determines how efficiently can be expelled related to quality factor. In this paper, a method based muon spin rotation ($\ensuremath{\mu}\mathrm{SR}$) is developed probe these parameters samples. It...
Nb$_3$Sn is currently the most promising material other than niobium for future superconducting radiofrequency cavities. Critical fields above 120 mT in pulsed operation and about 80 CW have been achieved cavity tests. This large compared to lower critical field as derived from London penetration depth, extracted low surface impedance measurements. In this paper direct measurements of depth which superheating are presented. The first vortex measured under DC RF fields. combined results...
Abstract We report measurements of the first-flux-penetration field in surface-treated and coated Nb samples using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi>μ</mml:mi> <mml:mtext>SR</mml:mtext> stretchy="false">)</mml:mo> </mml:mrow> </mml:math> . Using thin Ag foils as energy moderators for implanted muon spin-probes, we ‘profile’ vortex penetration <mml:msub> <mml:mn>0</mml:mn> </mml:msub>...
Abstract Superconducting radio frequency (SRF) cavities, which are critical components in many particle accelerators, need to be operated the Meissner state avoid strong dissipation from magnetic vortices. For a defect-free superconductor, maximum attainable field for operation is set by superheating field, <?CDATA $B_{\mathrm{sh}}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>B</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi>...
Superconducting RF is a key technology for future particle accelerators, now relying on advanced surfaces beyond bulk Nb leap in performance and efficiency. The SRF thin film strategy aims at transforming the current by using highly functional materials, addressing all necessary functions. community deploying efforts three research thrusts to develop next-generation thin-film based cavities. Cu cavities are developed perform as good or better than reduced cost with thermal stability. Recent...
Using muon spin rotation it is shown that the field of first flux penetration H_entry in Nb enhanced by about 30% if coated with an overlayer Nb_3Sn or MgB_2. This consistent increase from lower critical magnetic H_c1 up to superheating H_sh substrate. In experiments presented here coatings and MgB_2 a thickness between 50 2000nm have been tested. does not depend on material thickness. suggests energy barrier at boundary two materials prevents entry A mechanism these findings proximity...
While several experiments claim that two-level system (TLS) defects in amorphous surfaces/interfaces are responsible for energy relaxation superconducting resonators and qubits, none can provide quantitative explanation of their data terms the conventional noninteracting TLS model. Here a model interpolates between interacting loss tangent is proposed to perform numerical analysis experimental extract information about parameters distribution. As proof principle, applied TESLA cavities...
We report measurements of the first-flux-penetration field in surface-treated and coated Nb samples using muon spin rotation ($\mu$SR). Using thin Ag foils as energy moderators for implanted spin-probes, we "profile" vortex penetration $\mu_{0} H_{\mathrm{vp}}$ at sub-surface depths on order $\sim 10$ $\mathrm{\mu}$m to 100$ $\mathrm{\mu}$m. In a sample [Nb$_3$Sn(2 $\mathrm{\mu}$m)/Nb], find that is depth-independent with value 234.5(35) mT, consistent Nb's metastable superheating suggestive...
In particle accelerators superconducting RF cavities are widely used to achieve high accelerating gradients and low losses. Power consumption is proportional the surface resistance RS which depends on a number of external parameters, including frequency, temperature, magnetic electric field. Presently, there no accepted model describing increase Rs with applied frame this project 400 MHz Quadrupole Resonator has been extended 800 1200 study intrinsic critical field samples over wide...
The quadrupole resonator, designed to measure the surface resistance of superconducting samples at 400 MHz has been refurbished. accuracy its RF-dc compensation measurement technique is tested by an independent method. It shown that device enables also measurements 800 and 1200 capable probe critical RF magnetic field. electric field configuration resonator are dependent on excited mode. how this can be used distinguish between losses.
Abstract Measuring neutron capture cross sections of radioactive nuclei is a crucial step towards better understanding the origin elements heavier than iron. For decades, precise measurement direct in “stellar” energy range (eV up to few MeV) was limited stable and longer-lived that could be provided as physical samples then irradiated with neutrons. New experimental methods are now being developed extend these measurements shorter-lived ( $$t_{1/2}<$$ <mml:math...
Mid-T heat treatments in the range from 250°C to 400°C on superconducting radio-frequency (SRF) cavities have been shown provide high quality factors that rise with applied rf field strength frequency, electro-polished (EP), elliptical operating at 2 K, similar nitrogen doped cavities. The factor is attributed a decrease temperature dependent part of surface resistance R BCS . Until now, no results reported for these new quarter-wave resonators (QWR) and half-wave (HWR). TRIUMF multi-mode...
We report measurements of the Meissner screening profile in a Nb(300 nm)/Al2O3 thin film using 8Liβ-detected nuclear magnetic resonance (β-NMR). The NMR probe 8Li was ion-implanted into Nb at energies ≤ 20 keV, corresponding to mean stopping depths comparable Nb’s penetration depth λ. 8Li’s strong dipole–dipole coupling with host 93Nb nuclei provided “cross-relaxation” channel that dominated low fields, which conferred indirect sensitivity local field via spin-lattice relaxation (SLR) rate...
The performance of Nb superconducting radio-frequency (SRF) cavities in particle accelerators is often limited by breakdown events below the intrinsic limiting surface fields Nb. Though excellent rf properties have been achieved, a detailed understanding causal links between treatment, defects, and ultimate lacking. This study uses magnetic writer probe from conventional hard-disk drive as near-field microwave microscope, to localized response SRF-grade samples. reveals nonlinear due...
Superconducting Radio-Frequency cavities are currently made out of niobium. Niobium limited by the magnetic field on cavity walls due to entry vortices at first vortex penetration, H[Formula: see text]. Low temperature baking in vacuum or low pressure gas atmosphere removes strong decrease quality factor with accelerating gradient (high Q-slope). Some reach surface above lower critical One hypothesis for this performance increase is that outer layer affected treatments acts as a barrier...
Point contact tunneling (PCT) and low energy muon spin rotation (LE-muSR) are used to probe, on the same samples, surface superconducting properties of micrometer thick niobium films deposited onto copper substrates using different sputtereing techniques: diode, dc magnetron (dcMS) HIPIMS. The combined results compared radio-frequency tests performances RF cavities made with processes. Degraded found yield lower quality factors stronger Q slope. In addition, both techniques find evidence for...
The potential for a superconducting proton linac (SPL) at CERN started to be seriously considered the end of 1990s. In first conceptual design report (CDR), published in 2000 [1], most 352 MHz RF equipment from LEP was re-used an 800 m long linac, and beam energy limited 2.2 GeV. During following years, revisited optimized better match needs high-power driver neutrino physics. result more compact (470 long) accelerator capable delivering 5 MW power 3.5 GeV, using state-of-the-art cavities...
The surface resistance Rs of superconducting materials can be obtained by measuring the quality factor an elliptical cavity excited in a transverse magnetic mode (TM010). value has however to taken as averaged over whole surface. A more convenient way obtain Rs, especially which are not yet technologically ready for production, is measure small samples instead. These easily manufactured at low cost, duplicated and placed film deposition analytical tools. commonly used design device consists...
The surface resistance ${R}_{\mathrm{S}}$ of superconducting cavities prepared by sputter coating a niobium film on copper substrate increases significantly stronger with the applied rf field compared to bulk material. A possible cause is that thermal boundary between and induces heating inner cavity wall, resulting in higher ${R}_{\mathrm{S}}$. Introducing helium gas cavity, measuring its pressure as function allowed conclude heated up less than 120 mK when ${E}_{\mathrm{acc}}$ $100\text{...
Abstract The maximum accelerating gradient of superconducting radio frequency cavities are currently reaching their theoretical limits, due to the magnetic field entering superconductor in form vortices. To overcome these thin film coated materials required, however need be tested optimise properties. A system has been designed, built, and commissioned at Daresbury Laboratory that applies a local DC parallel surface, from one side sample, similar cavity operation. flux density (up 600 mT) is...