Niobium Membrane Research Articles

Stresses in flexure pendulums for gravitational wave detectors

We show that in flexures for low loss pendulums, surface stresses and boundary condition can cause unacceptable stress build up. We compare stress distributions in wires and membranes. The absence of violin string resonances and compatibility with high Q-factor sapphire test masses makes the niobium membrane flexure advantageous although the pendulum Q-factor does not exceed that of all fused silica pendulums.

Deuterium permeation through Nb during low energy ion irradiation at controlled surface conditions

Permeation rates of deuterium through a niobium membrane have been investigated as a function of the primary ion energy and the membrane temperature at controlled surface conditions. A mass separated ion beam with the ion energy in the range of 400–1500 eV per deuteron was used. The ion channel supplied a high ratio of the ion beam current to the background molecular flux to the surface. It allowed to measure the fluxes of reflected and reemitted particles along with the permeation flux with in-situ surface analysis by Auger electron spectrometry (AES) and secondary ion mass spectrometry (SIMS). The recombination rate coefficients were obtained experimentally in steady-state conditions for both upstream-side and downstream-side membrane surfaces by evaluating the concentration of dissolved hydrogen by means of thermodesorption technique and taking into account the contribution of the reflected particles to the flux balance. Experimental data of the hydrogen recombination coefficient have been compared with the numerical evaluation by using the Richards—Nagasaki model.

Interactions of low energy hydrogen ions with niobium: effects of non-metallic overlayers on reemission, retention and permeation

The interactions of hydrogen ions in the energy range of tens of eV with a 0.1 mm-thick niobium membrane have been investigated. Effects of non-metallic impurities (oxygen, carbon and sulphur) at the membrane inlet side on hydrogen reemission, retention and permeation were studied. The non-metal films were continuously maintained during the experimental runs through acting on the specimen with chemically active gases (oxygen, acetylene and hydrogen sulphide) in the process of hydrogen ion bombardment. A particular emphasis was placed on reaching and upholding the superpermeability regimes due to the non-metallic overlayers, as well as on the peculiarities of the ion-induced reemission by the low energy hydrogen ions.

Parametric back-action effects in a high-Q cyrogenic sapphire transducer

The construction and operation of a high-quality factor microwave sapphire resonator transducer coupled to a 1 kHz niobium membrane acoustic oscillator are presented in this paper. A four-stage passive vibration isolation system was included in the design to permit the measurement of the transducer’s parametric properties. The isolation system was shown to sufficiently suppress mechanical noise above 100 Hz and an upper limit to the displacement sensitivity of the transducer was measured to be 3.0±0.6×10−16 m/√Hz. The parametric behavior of the transducer with a single pump readout was measured for several transducer configurations, and the results were found to be in good agreement with theory. The measurements presented here display for the first time the complete parametric behavior in a high electrical Q system, where the transducer’s bandwidth is less than the mechanical oscillator’s frequency. The high stability and low losses of our system may allow the transducer to be configured as a back-action evasion or quantum nondemolition device.

Ion-induced effects on ion-driven deuterium permeation through niobium membrane

The permeation behavior of deuterium has been investigated for deuterium implanted into Nb membrane. Increase of the steady state permeation rate was observed at the simultaneous bombardment of the downstream-side membrane surface with argon and of the upstream-side surface with deuterium ions. An in-situ surface analysis was performed to monitor the back surface impurity composition, by means of AES and SIMS. The role of possible processes, such as ion-induced desorption, production of surface imperfection sites, and change of surface chemical composition, in the increase of permeation rate has been discussed.

Membrane pumping technology for helium and hydrogen isotope separation in the fusion reactor

A gas pumping system for ITER, improved by implementation of superpermeable membranes for selective hydrogen isotope exhaust, is considered. A study of the pumping capability of a niobium membrane for a hydrogen-helium mixture has been performed. Monte Carlo simulations of gas behaviour for the experimental facility and fusion reactor have been done. The scheme of the ITER pumping system with the membranes and membrane pumping technology was considered. The conceptual study the membrane pump for the ITER was done. This work gives good prospects for the membrane pumping use in ITER to reduce the total inventory of tritium necessary for reactor operation.

Hydrogen permeation through niobium membrane contacting with liquid lithium

Hydrogen permeation through niobium membrane contacting with liquid lithium was experimented using natural convection type loop containing about one kilogram of lithium. Disk type niobium membrane (0.02 cm thick and 5.8 cm 2 in area) which was welded to a tube was inserted into liquid lithium and permeation constant was obtained from the hydrogen pressure change in the tube after it was disconnected from a vacuum line. Hydrogen permeation constant was smaller by about two orders of magnitude than in the ideal case when diffusion in metal is rate-determining. This is considered to be caused by the layer of niobium nitride (Nb 2N) which formed on the lithium side surface of the niobium membrane. Changes of hydrogen permeation constants with hydrogen concentration in lithium were studied and hydrogen permeation rate was considered to have a linear relationship with hydrogen pressure. In the next step of our experiments, nitrogen in lithium was gettered by titanium in which case the hydrogen permeation constant became several times larger than in not gettered lithium. Nitrogen transport from niobium surface was however a slow reaction and there would be a limitation of the reaction as well as permeation resistance of oxide film at the gas side.

Behaviors of Impurities in Liquid Sodium, (II)

The behavior of hydrogen in liquid sodium containing relatively large amounts of oxygen were investigated with the aid of the hydrogen sensor of niobium membrane. The partial pressure of the hydrogen in liquid sodium at hot zone of a cold-trapped natural circulation sodium loop was measured as functions of temperatures of the cold trap and the hot zone of the loop. It was observed that at constant cold trap temperature the partial pressure of hydrogen in sodium increases with increasing the hot zone temperature. This study also showed that, keeping the temperature of hot zone constant, a logarithmic plot of hydrogen concentration calculated from the equilibrium hydrogen partial pressure vs. the reciprocal temperature of cold trap yields a straight line whose slope is nearly equal to that on the solubility of sodium hydroxide in sodium. Finally, it was observed that the permeation of hydrogen in sodium through a niobium membrane is a process controlled by diffusion. But the permeability for hydrogen in nio...

Behaviors of impurities in liquid sodium. II. Effect of oxygen on behavior of hydrogen in liquid sodium.

The behavior of hydrogen in liquid sodium containing relatively large amounts of oxygen were investigated with the aid of the hydrogen sensor of niobium membrane. The partial pressure of the hydrogen in liquid sodium at hot zone of a cold-trapped natural circulation sodium loop was measured as functions of temperatures of the cold trap and the hot zone of the loop. It was observed that at constant cold trap temperature the partial pressure of hydrogen in sodium increases with increasing the hot zone temperature. This study also showed that, keeping the temperature of hot zone constant, a logarithmic plot of hydrogen concentration calculated from the equilibrium hydrogen partial pressure vs. the reciprocal temperature of cold trap yields a straight line whose slope is nearly equal to that on the solubility of sodium hydroxide in sodium. Finally, it was observed that the permeation of hydrogen in sodium through a niobium membrane is a process controlled by diffusion. But the permeability for hydrogen in niobium is a few-hundredths smaller than that in literature, owing to the oxide film on the membrane surface.

Behaviors of Impurities in Liquid Sodium, (III)

The behavior of hydrogen in liquid sodium containing relatively large amounts of oxygen were investigated with the aid of the hydrogen sensor of niobium membrane. The partial pressure of the hydrogen in liquid sodium at hot zone of a cold-trapped natural circulation sodium loop was measured as functions of temperatures of the cold trap and the hot zone of the loop. It was observed that at constant cold trap temperature the partial pressure of hydrogen in sodium increases with increasing the hot zone temperature. This study also showed that, keeping the temperature of hot zone constant, a logarithmic plot of hydrogen concentration calculated from the equilibrium hydrogen partial pressure vs. the reciprocal temperature of cold trap yields a straight line whose slope is nearly equal to that on the solubility of sodium hydroxide in sodium. Finally, it was observed that the permeation of hydrogen in sodium through a niobium membrane is a process controlled by diffusion. But the permeability for hydrogen in nio...