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Fritsch, K.

Publications and source records attributed to Fritsch, K..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Quenched crystal-field disorder and magnetic liquid ground states in Tb 2 Sn 2 - x Ti x O 7 [Crystal field disorder in the quantum spin ice ground state of Tb2Sn2-xTixO7]

Solid-solutions of the "soft" quantum spin ice pyrochlore magnets Tb 2 B 2 O 7 with B=Ti and Sn display a novel magnetic ground state in the presence of strong B-site disorder, characterized by a low susceptibility and strong spin fluctuations to temperatures below 0.1 K. These materials have been studied using ac-susceptibility and muSR techniques to very low temperatures, and time-of-flight inelastic neutron scattering techniques to 1.5 K. Remarkably, neutron spectroscopy of the Tb 3+ crystal field levels appropriate to at high B-site mixing (0.5 < x < 1.5 in Tb 2 Sn 2-x Ti x O 7 ) reveal that the doublet ground and first excited states present as continua in energy, while transitions to singlet excited states at higher energies simply interpolate between those of the end members of the solid solution. The resulting ground state suggests an extreme version of a random-anisotropy magnet, with many local moments and anisotropies, depending on the precise local configuration of the six B sites neighboring each magnetic Tb 3+ ion.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Fiber-linked interferometric pressure sensor

A fiber-optic pressure sensor is described which uses a diaphragm to modulate the mirror separation of a Fabry-Perot cavity (the sensing cavity). A multimode optical fiber delivers broadband light to the sensing cavity and returns the spectrally modulated light which the cavity reflects. The sensor's output spectrum is analyzed using a tunable Fabry-Perot cavity (the reference cavity) to determine the mismatch in the mirror separations of the two cavities. An electronic servo control uses this result to cause the mirror separation of the reference cavity to equal that of the sensing cavity. The displacement of the pressure-sensing diaphragm is then obtained by measuring the capacitance of the reference cavity's metal-coated mirrors. Relative to other fiber-optic sensors, an important advantage of this instrument is its high immunity to the effects of variations in both the transmissivity of the fiber link and the wavelength of the optical source.

Beheim, G.↗
NASA NTRS1986

Range finding using frequency-modulated laser diode

A coherent-optical time-of-flight range-finding technique is proposed which uses a simple inexpensive device. Target range is determined by modulating a laser diode's optical frequency and measuring the change in the phase of the light reflected back into the laser. Target velocity as well as range can be measured using this approach. The device is described, and experimental evidence is presented to show the feasibility of measuring distance with subcentimeter resolution over a 1.5-m range.

Beheim, G.↗
NASA NTRS1986

Wavelength-division multiplexed digital optical position transducer

A novel concept for a digital optical position tranducer is presented. This compact and rugged device is electrically passive and requires only a dual-fiber optical link. Wavelength division of a broad-spectrum semiconductor light source is employed to multiplex the channels of a 10-bit digital position encoder. A preliminary design was evaluated and found to have a 10-dB on-off contrast ratio and a 12-dB insertion loss.

Fritsch, K.↗
NASA NTRS1985

Remote displacement measurements using a laser diode

A technique for measuring displacements remotely to minimum distances of 8 mm with a resolution of 2 microns is described. A dynamic interferometer method is employed using a frequency-ramped laser diode. A direct measurement of the period of the resulting beat signal is used to determine the displacement.

Beheim, G.↗