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NASA NTRS1990

Physicists make a difference in space cryogenics

An evaluation is made of space cryogenics technology development challenges in whose treatment the unique abilities of physicists have been notably valuable. In addition to such broad concerns as the quantum properties of superfluid He, the basic laws of thermodynamics and entropy, and quantization of such fields as those of phonons and magnons, productive efforts have been made by physicists in the basic principles of SQUIDs, magnetic shielding due to the Meissner effect in superconductors, adiabatic demagnetization, and dilution cooling of He-3 and He-4. These contributions will be of fundamental importance to the IR Telescope for Space and Advanced X-ray Astronomical Facility, which are currently under development.

Petrac, D.↗

NASA NTRS1990

The origin of the White Beds below the Cretaceous-Tertiary boundary in the Gubbio section, Italy

This paper examines the origin of the 20-50-cm-thick set of whitish limestone beds found immediately underlying the Cretaceous-Tertiary (K-T) boundary in Umbrian sections. On the basis of isothermal remanent magnetization (IRM) acquisitions and thermal demagnetization experiments, it is argued that the white beds were deposited under the same conditions as the underlying pink beds and that the anomalously low IRM intensities found in the white beds resulted from the reduction of hematite in the originally pink beds followed by the removal of the Fe(2+) ions. The whitening of the beds is ascribed to the consequence of downward infiltration of reducing waters resulting from the large quantity of organic matter produced by the extinctions at the K-T boundary. The white interval below the K-T boundary is thus compatible with the hypothesis of impact-triggered mass extinction.

Lowrie, W.↗

NASA NTRS1991

Remanent magnetic properties of unbrecciated eucrites

This study examines the remanent magnetic properties of five unbrecciated eucrites, ranging from the coarse-grained cumulate Moore County to the quenched melt rock ALH 81001 in order to assess the strength of the magnetic field associated with their parent body during their formation. Two of the meteorites are judged as unlikely to have preserved their primary thermal remanence because of large variations in subsample remanence intensity and direction (Ibitira), and lack of NRM resistance to AF and thermal demagnetization (PCA 82502). The lack of a strong (greater than 0.01 mT) magnetizing field during their cooling on the eucrite parent body is inferred from the low normalized NRM intensities for subsamples of ALH 81001 and Yamato 791195.

Cisowski, Stanley M.↗

NASA NTRS1990

Technology development program for the Space Infrared Telescope Facility (SIRTF) science instruments

A coordinated technology program for the Space Infrared Telescope Facility (SIRTF) is described. The program encompasses detector technology, cryogenic mechanisms technology, and an adiabatic demagnetization refrigerator. Discrete detectors, detector arrays, detector readouts, and testing of engineering models under simulated flight environment conditions are considered. Several focal planes will be optimized at a particular wavelength range to make up over 247,000 detector pixels from about 1.8 to 1000 microns.

Ramos, Ruben↗

NASA NTRS1990

A spaceworthy ADR - Recent developments

Recent developments concerning the performance and reliability of a spaceworthy adiabatic demagnetization refrigerator (ADR) for the AXAF X-ray spectrometer are considered. They include a procedure for growing the salt pill around a harness made up of 6080 gold-plated copper wires, a totally modular gas gap heat switch, and a suspension system utilizing Kevlar fibers.

Serlemitsos, Aristides T.↗

NASA NTRS1992

Space Cryogenics Workshop, 10th, Cleveland, OH, June 18-20, 1991, Proceedings

The present workshop on cryogenics discusses the anomalous on-orbit behavior of the Cosmic Background Explorer Dewar, the SHOOT orbital operations, cooling options for Astromag, and space IR telescope facility mission and cryogenic design. Attention is given to the design of a spaceworthy adiabatic demagnetization refrigerator, the evaluation of metal hydride compressors for applications in Joule-Thomson cryocoolers, diaphragm Stirling cryocooler developments, and a computer simulation model for Stirling refrigerators. Topics addressed include low-gravity thermal stratification of liquid helium on SHOOT, a screening program to select a resin for gravity probe-B composites, a simplified generic cryostat thermal model for predicting cryogen mass and lifetime, and the effect of gas mass flux on cryogenic liquid jet breakup. Also discussed are damping criteria for thermal acoustic oscillations in slush and liquid hydrogen systems, an STS-based cryogenic fluid management experiment, and the design and testing of a cryogenic mixer pump.

Source record↗

NASA NTRS1991

A flightworthy ADR for use in the AXAF/XRS

NASA-Goddard has undertaken the development of an adiabatic demagnetization refrigerator (ADR) for cooling the detectors of the Advanced X-ray Astrophysical Facility's X-ray Spectrometer (XRS) to the requisite 0.065 K-operation temperature. The XRS ADR's intricate thermal bus system furnished excellent thermal conductance for both the low parasitic heat leak heat switch during the magnetization cycle, and the detectors during low temperature operation. Attention is given to the ADR's operating principles, construction, and suspension system.

Serlemitsos, Aristides T.↗

NASA NTRS1993

A two-stage magnetic refrigerator for astronomical applications with reservoir temperatures above 4 K

We propose a novel adiabatic demagnetization refrigerator (ADR) to produce temperatures as low as 100 mK starting from a high temperature reservoir between 4 and 8 K. The high temperature reservoir for the ADR can be provided by a mechanical cooler or an unpumped liquid helium bath. This refrigerator can be used to cool bolometric infrared detectors for low background astronomy from mountain tops, balloons or satellites as well as to cool cryogenic x-ray detectors. The two-stage ADR consists of a single magnet with a paramagnetic chromic-cesium-alum (CCA) salt pill to produce the low temperature and paramagnetic gadolinium-gallium-garnet (GGG) as the first stage to intercept heat from the high temperature reservoir. Thermal contact between the paramagnets and the reservoir during magnetization is made with a mechanical heat switch. The ADR is suspended with Kevlar chords under tension for high mechanical stiffness and low parasitic heat leak. In a single cycle, the ADR maintains a temperature of 100 mK for 10 to 100 hours. This time depends strongly on the magnetic field and reservoir temperature but not on the volume of the paramagnetic material as long as the heat leak is dominated by the suspension.

Hagmann, C.↗

NASA NTRS1991

The AXAF/XRS ADR - Engineering model

A spaceworthy Adiabatic Demagnetization Refrigerator is under development at Goddard Space Flight Center as part of the X-Ray Spectrometer (XRS), an instrument on the Advanced X-ray Astrophysics Facility (AXAF). XRS will employ an array of 32 microcalorimeters capable of detecting X-rays in the energy range of 0.3 - 10 keV. In order to achieve a desired resolution of 12 eV, these detectors must be operated at a temperature of 0.065 - 0.100 K. An ADR must be used to cool these detectors in space. A breadboard model was designed and built less than two years ago, and provided excellent results. We are presently at the development stage of the engineering model. Several changes have been made to the original design in order to improve the efficiency of the ADR, to reduce its weight, and to strengthen the salt pill suspension system so that the ADR can survive launch loads and have low sensitivity to microphonic inputs. We shall report on the results of these changes; what worked and what did not.

Serlemitsos, Aristides T.↗

NASA NTRS1991

The X-ray Spectrometer - A cryogenic instrument on the Advanced X-ray Astrophysics Facility

The X-ray Spectrometer (XRS) is an instrument on the Advanced X-ray Astrophysics Facility (AXAF), the third of NASA's Great Observatories scheduled for launch in 1998. The XRS detectors have a resolution of approximately 10 eV over the range 0.3 - 10 keV. To achieve this resolution, the detectors are maintained at or below 0.1 Kelvin using an adiabatic demagnetization refrigerator inside a superfluid helium dewar. In addition, split-Stirling-cycle mechanical coolers are used to extend the anticipated on-orbit helium lifetime to a minimum of 4 years. This paper describes the challenges of developing this hybrid cryogenic system and presents an overview of the current design of the system.

Breon, Susan R.↗

NASA NTRS1991

The AXAF/XRS test dewar - A versatile design

The X-Ray Spectrometer (XRS) to be flown on the Advanced X-ray Astrophysics Facility (AXAF) consists of an array of microcalorimeters and an Adiabatic Demagnetization Refrigerator (ADR). The ADR provides an operating temperature of 0.065 to 0.100 K. To support extensive development testing of the ADR and the detector array, a test dewar has been designed and built that surpasses specification requirements. Pumping on the liquid helium bath with a 47 l/s pump, we have achieved temperatures lower than 1.5 K with a hold time in excess of 72 hrs. The dewar can be operated without liquid nitrogen with a hold time of 36 hrs. This feature was incorporated in the design because boiling nitrogen may introduce microphonic noise to the detectors. To further reduce the susceptibility to microphonic vibration a unique suspension system utilizing Kevlar fibers was devised which provides both translational and rotational rigidity to the detector mount. Finally, the dewar is very manageable and may be rotated by only one person.

Weintz, Karl F.↗

NASA NTRS1991

5-year lifetime hybrid superfluid helium dewar for the AXAF X-Ray Spectrometer (XRS)

The focal plane of the AXAF X-Ray Spectrometer requires an operating temperature of 0.1 K with a mission lifetime of 5 yrs. This demanding task is accomplished with a hybrid cryogenic subsystem consisting of mechanical coolers, a superfluid helium dewar and an adiabatic demagnetization refrigerator. By using mechanical coolers to remove heat from the dewar outer vapor-cooled shield, a 5-yr lifetime is achievable with only a 483-liter tank. This approach takes advantage of flight-proven, high-performance dewar technology and recent success in the development of split, Stirling-cycle mechanical coolers. Although the dewar design principles are similar to those used previously, parasitic heat flow is reduced to a new level by an optimized tension strap support system and careful attention to insulation system details. The benefit of the mechanical coolers is maximized by dewar interface design features that minimize parasitic heating and thermal impedance of the coupling. The dewar design and thermal performance analysis are discussed. Helium lifetime sensitivities and the effects of mechanical cooler failures are predicted.

Nieczkoski, Stephen J.↗

NASA NTRS1993

Two-polarity magnetization in the Manson impact breccia

A preliminary paleomagnetic study of the impact breccia matrix and clasts has produced surprising results--nearly antipodal normal and reversed polarity magnetic vectors are observed in different portions of the core. Near-antipodal magnetizations within a segment of matrix and within individual samples rule out core inversion as the explanation of the dual polarity. In both the dense and the sandy matrix breccias, the magnetizations of clasts and matrix within the same core segment are identical; this negative 'conglomerate test' indicates that magnetization originated after impact. Paleomagnetic study of the Manson Impact Structure is an attempt to refine the Ar-40/Ar-39 age (65.7 +/- 1 m.y.) that suggests Manson to be a Cretaceous-Tertiary boundary impact. Refinement is possible because the boundary occurs within a reversed polarity interval (29R) of only 0.5 m.y. duration. The two breccia types in the Manson structure were both examined: one of a very dense matrix and apparently partially melted, and the breccia stratigraphically below it of granular or 'sandy' chloritic matrix. Samples were taken from the matrixes and a wide variety of clast compositions, including granite, diabase, gneiss, amphibolite, and melted granite. Currently, measurements have been made on 22 samples, using 30-35 steps of either alternating field (AF) or thermal demagnetization.

Steiner, M. B.↗

NASA NTRS1994

The Teton fault, Wyoming: Topographic signature, neotectonics, and mechanisms of deformation

We integrated geophysical and geological methods to evalute the structural evolution of the active Teton normal fault, Wyoming, and its role in the development of the dramatic topography of Teton Range and Jackson Hole. Comparison of variations in surface offsets with the topographic expression of the Teton range crest and drainage divide, and the overall structure of the range, suggests that the effects ofpostglacial faulting cannot be discriminated from the influence of pre-extensional structures and differential; erosion on the footwall topography. In contrast, the effects of multiple scarp-forming normal faulting earthquakes are expressed by the anomalous drainage pattern and westward tilt of the hanging wall, Jackson Hole, toward the Teton fault. Kinematic boundary element fault models suggest that the westward tilt of the valley floor is the product of 110-125 m of displacement on a 45 deg-75 deg E dipping Teton fault in the past 25,000-75,000 years. Comparisons with historic normal faulting earthquake displacements imply that this range of displacement corresponds to 10-50, M greater than 7 scarp-forming earthquakes. A total throw of 2.5 to 3.5 km across the Teton fault is suggested by inverse ray-tracing and forward gravity models. These models also suggest that Laramide age structures have been offset across the Teton fault and obscure its geophysical signature but also continue to influence the structural and topographic expression of the footwall and hanging wall blocks. Paleomagnetic analyses of the approximately 2.0 Ma Huckelberry Ridge Tuff suggest that the overall westward tilt of the Teton Range is a result ofabout 10 deg of west side down tilt across the Teton fault since tuff emplacement. This suggests that much if not all of the throw across the Teton fault has accumulated in the past 2 m.y. Complex demagnetization and rock magnetic behavior and local emplacement of the Huckleberry Ridge Tuff on preexisting topogrpahy preclude determination of the amount or variations in throw along strike of the Teton fault from the paleomagnetic data.

Byrd, John O. D.↗

NASA NTRS1994

Reverse Polarity Magnetized Melt Rocks from the Cretaceous/Tertiary Chicxulub Structure, Yucatan Peninsula, Mexico

We report paleomagnetic results for core samples of the breccia and andesitic rocks recovered from the Yucatan-6 Petrolcos Mexicanos exploratory well within the Chicxulub structure (about 60 km SSW from its center), northern Yucatan, Mexico. A previous study has shown that the rocks studied contain high iridium levels and shocked breccia clasts and an Ar/Ar date of 65.2 +/- 0.4 Ma. Andesitic rocks are characterized by stable single-component magnetizations with a mean inclination of -42.6 deg +/- 2.4 deg. Breccias present a complex paleomagnetic record characterized by multivectorial magnetizations with widely different initial NRM inclinations. However, after alternating field demagnetization, well defined characteristic components with upward inclinations are defined. IRM acquisition experiments, comparison of IRM and NRM coercivity spectra and the single component magnetization of the andesitic rocks indicate the occurrence of iron-rich titanomagnetites of single or pseudo-single domain states as the dominant magnetic carriers. Mean inclinations from the andesitic rocks and most of the breccia samples give a mean inclination of about -40 deg to -45 deg, indicating a reverse polarity for the characteristic magnetization that is consistent with geomagnetic chron 29R, which spans the Cretaceous/Tertiary (K/T) boundary. The inclination is also consistent with the expected value (and corresponding paleolatitude) for the site estimated from the reference polar wander curve for North America. We suggest that the characteristic magnetizations for the andesitic and breccia rocks are the result of shock heating at the time of formation of the impact structure and that the age, polarity and pateolatitude are consistent with a time at the K/T boundary.

Urrutia-Fucugauchi, J.↗

NASA NTRS1996

The South Pole Imaging Fabry Perot Interferometer (SPIFI)

The design and construction of the South Pole imaging Fabry-Perot interferometer (SPIFI) is reported. The SPIFI is a direct detection imaging spectrometer for use in the far infrared and submillimeter bands accessible to the 1.7 m telescope at the South Pole, and in the submillimeter bands accessible to the 15 m James Clerk Maxwell Telescope (JCMT), HI. It employs a 5 x 5 silicon bolometer array and three cryogenic Fabry Perot interferometers in series in order to achieve velocity resolutions of between 300 km/s and 30 km/s over the entire field of view with a resolution of up to 1 km/s at the center pixel. The scientific justification for the instrument is discussed, considering the spectral lines available to SPIFI. The optical path, the cryogenic Fabry-Perot, the adiabatic demagnetization refrigerator and the detector array are described. The instrument's sensitivity is presented and compared with coherent systems.

Stacey, G. J.↗

NASA NTRS1993

Paleomagnetism and Tectonic Interpretations of the Taos Plateau Volcanic Field, Rio Grande Rift, New Mexico

The tectonic response of the Taos Plateau volcanic field in the southern San Luis basin to the late stage extensional environment of the Rio Grande rift was investigated using paleomagnetic techniques. Sixty-two sites (533 samples) of Pliocene volcanic units were collected covering four major rock types with ages of 4.7 to 1.8 Ma. Twenty-two of these sites were from stratigraphic sections of the lower, middle and upper Servilleta Basalt collected in the Rio Grande gorge at two locations 19 km apart. Flows from the lower and middle members in the southern gorge record reversed polarities, while those in Garapata Canyon are normal with an excursion event in the middle of the sequence. The uppermost flows of the upper member at both sites display normal directions. Although these sections correlate chemically, they seem to represent different magnetic time periods during the Gilbert Reversed-Polarity Chiron. Alternating field demagnetization, aided by principal component analysis, yields 55 sites with stable directions representing both normal and reversed polarities, and five sites indicating transitional fields. Mean direction of the normal and inverted reversed sites is I=49.3 deg. and D=356.7 deg. (alpha(sub 95)=3.6 deg). Angular dispersion of the virtual geomagnetic poles is 16.3 deg, which is consistent with paleosecular variation model G, fit to data from the past 5 m.y. Comparison with the expected direction indicates no azimuthal rotation of the Taos Plateau volcanic field; inclination flattening for the southern part of the plateau is 8.3 deg +/- 5.3 deg. Previous paleomagnelic data indicate 10 deg- 15 deg counterclockwise rotation of die Espanola block to the south over the past 5 m.y. The data suggest the Taos Plateau volcanic field, showing no rotation and some flattening in the south and east, has acted as a stable buttress and has been downwarped by overriding of the southeastern end of the plateau by the Picuris Mountains, which make up the northern corner of the counterclockwise rotating Espanola block.

Brown, Laurie L.↗

NASA NTRS1998

The Third Flight Magnet

A self-shielded superconducting magnet was designed for the NASA Goddard Space Flight Center Adiabatic Demagnetization Refrigerator Program. This is the third magnet built from this design. The magnets utilize Cryomagnetics' patented ultra-low current technology. The magnetic system is capable of reaching a central field of two tesla at slightly under two amperes and has a total inductance of 1068 henries. This final report details the requirements of the magnet, the specifications of the resulting magnet, the test procedures and test result data for the third magnet (Serial # C-654-M), and recommended precautions for use of the magnet.

McGhee, R. Wayne↗