A correlation between ionization energies and critical temperatures in superconducting A3C60 fullerides

AbstractBuckminster A3C60 fullerides (A=alkali metal) are usually superconductors with critical temperatures Tc in the range 2.5–40K. Although they are very similar in size, structure and many other aspects, the effect of the alkali atoms on Tc has generally been understood in terms of the variation of the lattice constant. Here we show that there seems to be a direct correlation between the sum of the ionization energies of the three alkali atoms in the superconducting A3C60 compounds and the corresponding critical temperatures. A linear fit of the correlation implies a certain limit for the sum, below which superconductivity should not occur. Ionization energies have so far not been connected to superconductivity

Submillimeter and Far-InfraRed Experiment (SAFIRE): A PI class instrument for SOFIA

SAFIRE is a versatile imaging Fabry-Perot spectrograph covering 145 to 655 microns, with spectral resolving powers ranging over 5-10,000. Selected as a "PI" instrument for the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA), SAFIRE will apply two-dimensional pop-up bolometer arrays to provide background-limited imaging spectrometry. Superconducting transition edge bolometers and SQUID multiplexers are being developed for these detectors. SAFIRE is expected to be a "First Light" instrument, useable during the initial SOFIA operations. Although a PI instrument rather than a "Facility Class" science instrument, it will be highly integrated with the standard SOFIA planning, observation, and data analysis tools.Comment: 11 page

Training of Instrumentalists and Development of New Technologies on SOFIA

This white paper is submitted to the Astronomy and Astrophysics 2010 Decadal Survey (Astro2010)1 Committee on the State of the Profession to emphasize the potential of the Stratospheric Observatory for Infrared Astronomy (SOFIA) to contribute to the training of instrumentalists and observers, and to related technology developments. This potential goes beyond the primary mission of SOFIA, which is to carry out unique, high priority astronomical research. SOFIA is a Boeing 747SP aircraft with a 2.5 meter telescope. It will enable astronomical observations anywhere, any time, and at most wavelengths between 0.3 microns and 1.6 mm not accessible from ground-based observatories. These attributes, accruing from the mobility and flight altitude of SOFIA, guarantee a wealth of scientific return. Its instrument teams (nine in the first generation) and guest investigators will do suborbital astronomy in a shirt-sleeve environment. The project will invest $10M per year in science instrument development over a lifetime of 20 years. This, frequent flight opportunities, and operation that enables rapid changes of science instruments and hands-on in-flight access to the instruments, assure a unique and extensive potential - both for training young instrumentalists and for encouraging and deploying nascent technologies. Novel instruments covering optical, infrared, and submillimeter bands can be developed for and tested on SOFIA by their developers (including apprentices) for their own observations and for those of guest observers, to validate technologies and maximize observational effectiveness.Comment: 10 pages, no figures, White Paper for Astro 2010 Survey Committee on State of the Professio

Sofia Observatory Performance and Characterization

The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities have been viewed as a first comprehensive assessment of the Observatory's performance and will be used to address the development activity that is planned for 2012, as well as to identify additional Observatory upgrades. A series of 8 SOFIA Characterization And Integration (SCAI) flights have been conducted from June to December 2011. The HIPO science instrument in conjunction with the DSI Super Fast Diagnostic Camera (SFDC) have been used to evaluate pointing stability, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an Active Mass Damper system installed on Telescope Assembly. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have been performed using the HIPO+FLITECAM Science Instrument configuration (FLIPO). A number of additional tests and measurements have targeted basic Observatory capabilities and requirements including, but not limited to, pointing accuracy, chopper evaluation and imager sensitivity. SCAI activities included in-flight partial Science Instrument commissioning prior to the use of the instruments as measuring engines. This paper reports on the data collected during the SCAI flights and presents current SOFIA Observatory performance and characterization

Simulation-Based Testing of Embedded Attitude Control Algorithms of an FPGA based Micro Satellite

This paper focuses on the issues regarding the software based testing approach which mainly utilizes the software models for the satellite environment and the satellite itself. This approach facilitates the use of real on-board software in a virtual satellite environment and hence gives an excellent means of system design qualification and performance verification. Use of FPGA as an on-board computer leads to the requirement of implementing the attitude control algorithms in the hardware which emphasizes the need of its testing in the loop with the simulator. Two different type of simulation environments are used to increase the credibility of the results

Origin of the northern Indus Fan and Murray Ridge, Northern Arabian Sea: Interpretation from seismic and magnetic imaging

The nature and origin of the sediments and crust of the Murray Ridge System and northern Indus Fan are discussed. The uppermost unit consists of Middle Miocene to recent channel-levee complexes typical of submarine fans. This unit is underlain by a second unit composed of hemipelagic to pelagic sediments deposited during the drift phase after the break-up of India-Seychelles-Africa. A predrift sequence of assumed Mesozoic age occuring only as observed above basement ridges is composed of highly consolidated rocks. Different types of the acoustic basement were detected, which reflection seismic pattern, magnetic anomalies and gravity field modeling indicate to be of continental character. The continental crust is extremely thinned in the northern Indus Fan, lacking a typical block-faulted structure. The Indian continent-ocean transition is marked on single MCS profiles by sequences of seaward-dipping reflectors (SDR). In the northwestern Arabian Sea, the Indian plate margin is characterized by several phases of volcanism and deformation revealed from interpretation of multichannel seismic profiles and magnetic anomalies. From this study, thinned continental crust spreads between the northern Murray Ridge System and India underneath the northern Indus Fan. © 2002 Elsevier Science B.V. All rights reserved

Correlation between Crystal Structure and Resistivity of High Temperature Superconductors

The paper is an attempt to find a relation between the crystal structure of optimum doped HTSC materials and the experimental resistivity value at about the temperature T(c) where the resistance of a superconducting material vanishes

Electron transport in nanostructures: a key to high temperature superconductivity

Nanostructured GaAs Schottky barrier diodes are used as low noise THz heterodyne detectors. Different diodes show that the electron transport is ballistic and given by an optimized depletion thickness Depl which is shorter than the mean free path length. The best THz mixer noise temperature is achieved when the depletion thickness is twice the doping distance in GaAs with Depl=2x. There also is a linear relation between the depletion thickness and the carrier mobility μ by (2x)**2≈h/(2e)μ. Since the mobility is proportional to 1/energy and because of many similarities when comparing with properties of high temperature superconductors (HTSC) it has been investigated if the doping distance x in HTSCs is connected with 1/(kTc). It turns out that there is also a strong correlation between x and the critical transition temperature Tc given by (2x)**2 similar1/Tc. A detailed analysis and comparison suggest that the correlation equation for HTSCs is linked to the transition temperature Tc, the density of states in a 1D quantum wire, the lowest energy E1 in a 1D quantum well, and to the Fermi energy