The Properties of Liquid and Solid Helium and Helium-3 and Helium-4

Wilks, J.; Keller, W.E.; Donnelly, Russell J.

doi:10.1119/1.1986153

Cited by 24 publications

(69 citation statements)

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“…The sudden loss of the coil superconductivity is called a quench, during which the rise of the coil's temperature induces the fast evaporation of the liquid helium and results in the fast decay of B 0 . The expansion ratio of helium is such that 1 l of liquid helium is transformed in 757 l of helium gas (Wilks 1967). Therefore, since standard clinical scanners can store between 1500 and 2000 liters of liquid helium, MRI systems are designed with a quench pipe system that can safely release the high-pressure low temperature cryogenics outside the building (Medicines and Healthcare Products Regulatory Agency 2015, Department of Veterans Affairs 2008).…”

Section: Introductionmentioning

confidence: 99%

Characterization of time-varying magnetic fields and temperature of helium gas exit during a quench of a human magnetic resonance system

Pace

Ricci

Scotoni

et al. 2019

Biomed. Phys. Eng. Express

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The quench of a human magnetic resonance imaging system is a critical event that may occur spontaneously, as an accident or purposely in response to an emergency. Although a magnet’s quench presents its own risks, little experimental data is available in this respect. In this study, the programmed quench of a human MRI scanner was used to measure the induced time varying magnetic fields ( d B / d t ) inside the bore in order to evaluate cardiac stimulation risks during a quench. Additionally, we measured the exit temperature of the helium gas, to evaluate potential implications in quench pipe design. The maximum d B / d t was 360 mT s−1 at the center of the magnet, far below the cardiac stimulation threshold (20 T s−1). The helium exit temperature reached 35 K, perhaps implying further considerations about quench pipe designs. Replication of similar experiments on programmed quenches, specially in high-field MRI systems, will be useful to further characterize quench risks.

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Section: Introductionmentioning

confidence: 99%

Characterization of time-varying magnetic fields and temperature of helium gas exit during a quench of a human magnetic resonance system

Pace

Ricci

Scotoni

et al. 2019

Biomed. Phys. Eng. Express

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“…Below a critical velocity the superfluid component has effectively zero viscosity. In a confined geometry such as a porous plug, there exists a thermomechanical pressure given by (Wilks 1967):…”

Section: Introductionmentioning

confidence: 99%

Porous plug for Gravity Probe B

Wang

Everitt

Frank

et al. 2015

Class. Quantum Grav.

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The confinement of superfluid helium for a Dewar in space poses a unique challenge due to its propensity to minimize thermal gradients by essentially viscous-free counterflow. This poses the risk of losing liquid through a vent pipe, reducing the efficiency of the cooling process. To confine the liquid helium in the Gravity Probe B (GP-B) flight Dewar, a porous plug technique was invented at Stanford University. Here, we review the history of the porous plug and its development, and describe the physics underlying its operation. We summarize a few missions that employed porous plugs, some of which preceded the launch of GP-B. The design, manufacture and flight performance of the GP-B plug are described, and its use resulted in the successful operation of the 2441 l flight Dewar on-orbit for 17.3 months.

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“…Thus, even though a scalar field cannot account for all possible gravitational phenomena, one could, nevertheless, start with this model, such as when describing the longitudinal density fluctuations of a medium. If, as happens with many physical systems (elastic media [7], turbulent fluids [8,9], superfluids [10], . .…”

Section: Introductionmentioning

confidence: 99%

Ultraweak excitations of the quantum vacuum as physical models of gravity

Consoli¹

2009

Class. Quantum Grav.

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It has been argued by several authors that the space-time curvature observed in gravitational fields, and the same idea of forms of physical equivalence different from the Lorentz group, might emerge from the dynamical properties of the physical flat-space vacuum in a suitable hydrodynamic limit. To explore this idea, one could start by representing the physical vacuum as a Bose condensate of elementary quanta and look for vacuum excitations that, on a coarse grained scale, resemble the Newtonian potential. In this way, it is relatively easy to match the weak-field limit of classical General Relativity or of some of its possible variants.The idea that Bose condensates can provide various forms of gravitational dynamics is not new. Here, I want to emphasize some genuine quantum field theoretical aspects that can help to understand i) why infinitesimally weak, 1/r interactions can indeed arise from the same physical vacuum of electroweak and strong interactions and ii) why, on a coarse-grained scale, their dynamical effects can be re-absorbed into an effective curved metric structure.

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The Properties of Liquid and Solid Helium and Helium-3 and Helium-4

Cited by 24 publications

References 0 publications

Characterization of time-varying magnetic fields and temperature of helium gas exit during a quench of a human magnetic resonance system

Characterization of time-varying magnetic fields and temperature of helium gas exit during a quench of a human magnetic resonance system

Porous plug for Gravity Probe B

Ultraweak excitations of the quantum vacuum as physical models of gravity

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