A5016167002- Superconducting Materials and Applications
- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Physics of Superconductivity and Magnetism
- High-pressure geophysics and materials
- Solid-state spectroscopy and crystallography
- Acoustic Wave Resonator Technologies
- Radiation Therapy and Dosimetry
- Fusion materials and technologies
- Optical and Acousto-Optic Technologies
- Nanowire Synthesis and Applications
- Advanced MEMS and NEMS Technologies
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Antenna and Metasurface Technologies
- Magnetic confinement fusion research
- Radiation Effects in Electronics
- Hydrogen Storage and Materials
- Magnetic Properties of Alloys
- Nuclear Physics and Applications
- Antenna Design and Analysis
- Spacecraft and Cryogenic Technologies
- Ferroelectric and Piezoelectric Materials
- Inertial Sensor and Navigation
European Organization for Nuclear Research
2022-2025
Pennsylvania State University
2014-2017
Centre National de la Recherche Scientifique
2010-2014
University of Alberta
2014
École Normale Supérieure - PSL
2014
Laboratoire de Physique de l'ENS
2013
Université Paris Cité
2010-2013
Sorbonne Université
2010-2012
Délégation Paris 7
2012
Université Grenoble Alpes
2009
GaToroid is a novel idea of steady-state, toroidal magnet that directs multiple charged particle beams for hadron or electron therapy without rotating parts ramping. has the potential conformal radiotherapy with configuration can be simpler and lighter than conventional gantries, also offering FLASH capability well beyond what presently possible. A crucial feature field profile, which optimized to maximize acceptance (large area) beam transmission (good homogeneity). We have built tested 1:3...
When submitted to large stresses at high temperature, usual crystals may irreversibly deform. This phenomenon is known as plasticity and it due the motion of crystal defects such dislocations. We have discovered that, in absence impurities zero temperature limit, helium 4 present a giant that anisotropic reversible. Direct measurements on oriented single show their resistance shear nearly vanishes one particular direction because dislocations glide freely parallel basal planes hexagonal...
We have measured the elasticity of high quality ultrapure ⁴He single crystals in low temperature region where supersolidity is supposed to occur. At 20 mK, our results are consistent with elastic coefficients previously at 1.2 K. As increases from 100 a large softening occurs because dislocations unpin ³He impurities. In absence impurities, free move down mK; soft. The magnitude this anomalous shows that form mobile mosaic structure. It illustrates remarkable quantum plasticity crystals.
A number of recent experiments have used torsional oscillators to study the behavior solid helium. The oscillator frequencies increased at temperatures below 200 mK, an effect attributed decoupling a fraction helium mass---the signature ``supersolid'' phase. However, helium's shear modulus also increases mK and frequency depends on its elastic properties, as well inertia. In many is introduced via hole in torsion rod, where contributes stiffness rod. with relatively large rod holes, changes...
Due to its flexibility in generating advanced field harmonic corrections and potential for low cost compared traditional designs, the Canted Cosine Theta (CCT) configuration is particularly interesting compact particle accelerators gantries medical applications. This paper presents design of a curved demonstrator named Fusillo, Nb-Ti dipole magnet that being developed at CERN, featuring large aperture 236 mm, small bending radius 1 m, angle 90 <inline-formula...
The mechanical behavior of crystals is dominated by dislocation networks, their structure, and interactions with impurities or thermal phonons. However, in classical crystals, networks are usually random often forming nonequilibrium clusters when motion freezes at low temperature. Helium provides unique advantages for the study dislocations: Crystals free all but isotopic impurities, concentration these can be reduced to parts per ${10}^{9}$ (ppb) level, mobile temperatures therefore remain...
Measurements on solid ${}^{4}$He show large softening of the shear modulus due to dislocations, behavior which has been described as giant plasticity. Dislocation networks may also be responsible for unusual seen in torsional oscillator and flow experiments. However, previous estimates dislocation densities vary by many orders magnitude, even single crystals grown under similar conditions. By measuring temperature frequency dependencies elastic dissipation, we have determined network lengths...
Our experiments show that in ${}^{4}$He crystals, the binding of ${}^{3}$He impurities to dislocations does not necessarily imply their pinning. Indeed, these there are two different regimes motion when bind them. At low driving strain $\ensuremath{\epsilon}$ and frequency $\ensuremath{\omega}$, where dislocation speed is less than a critical value (45 $\ensuremath{\mu}$m/s), apparently move together. Impurities really pin only at higher values $\ensuremath{\epsilon}\ensuremath{\omega}$. The...
We report the observation of superfluidlike mass flow through coin-shaped $8\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ thick solid $^{4}\mathrm{He}$ samples sandwiched between superfluid leads. Mass is found from melting pressure to at least 30 bar with a concomitant decrease in onset temperature 1 0.25 K. The mass-flow rate be sample dependent and can enhanced by thermal annealing. decreases decays nearly exponentially samples. dissipation associated becomes near 0.1 In contrast earlier...
We have studied natural purity $^{4}$He single crystals and polycrystals between 10 600 mK using a torsional oscillator with 2 cm$^{3}$ rigid cell made of sapphire smooth geometry. As the temperature was lowered, we observed sample dependent but reproducible resonant frequency shifts that could be attributed to supersolid fraction order 0.1%. However, these were crystals, not polycrystals. Our results indicate that, in our case, rotational anomaly solid helium is more likely due change...
The giant plasticity of [Formula: see text]He crystals has been explained as a consequence the large mobility their dislocations. Thus, mechanical properties dislocation free should be quite different from those usual ones. In 1996-1998, Ruutu et al. published crystal growth studies showing that, in helium 4 crystals, density screw dislocations along c-axis was less than 100 per cm[Formula: text], sometimes zero. We have grown using similar speeds and temperatures, extracted properties....
Solid helium is paradoxical: it both a model and an exception. It for crystal properties mainly because of its extreme purity which makes universal phenomena simpler easier to identify. also exceptional the large quantum fluctuations atoms around nodes in their lattice allow these occur at very low temperature with amplitude. As noticed by Jacques Friedel 2013, 4 crystals illustrate how motion dislocations may reduce shear elastic modulus, as does all hexagonal close packed (hcp) including...
The Fusillo project at CERN aims to design and build a demonstrator magnet with multi-harmonic corrected fields in 90° curved CCT magnet. In the first stage, subscale is built 30° bending, about 1/30 of conductor length, increased current reach coil stresses equivalent demonstrator. enables qualification technology developments, fabrication methods, winding assembly procedures, magnetic quench protection measurement setups. comprises two tilted solenoids an opposite inclination on aluminium...
Piezoelectric transducers are used to detect stress and generate nanometer scale displacements but their piezoelectric coefficients decrease with temperature, limiting performance in cryogenic applications. We have developed a capacitive technique directly measured the temperature dependence of shear coefficient d15 for ceramic lead zirconium titanate (PZT), 41° X-cut lithium niobate (LiNbO3) single crystal magnesium niobium-lead (PMN-PT). In PZT, decreases nearly linearly dropping by factor...
We have studied acoustic resonances in 4He single crystals the temperature region 20 < T 300 mK where a large softening occurs due to unbinding of dislocations from 3He impurities. Here we present an analysis dependence resonance frequencies on sound amplitude, that is stress crystal. Above threshold order 10−6 bar, this able unbind Our results indicate impurities diffuse along at 60 but not 23 mK.
GaToroid is a novel configuration of beam delivery system for charged particles therapy based on steady-state, axis-symmetric field configuration. The basic idea to use fixed toroidal magnets, producing an (or periodical axis-symmetric) that can bend beams from several directions onto the patient location. In principle, neither magnets nor need be moved. addition, this gantry static. Such perfectly adapted FLASH therapy, method dose has shown benefits electrons and potential hadrons. paper...