An 8.4-GHz cryogenically cooled HEMT amplifier for DSS 13

A prototype 8.4 GHz (X-band) high electron mobility transistor (HEMT) amplifier/closed cycle refrigerator system was installed in the Deep Space Station 13 feedcone in August 1987. The amplifier is cryogenically cooled to a physical temperature of 12 K and provides 31 K antenna noise temperature (zenith) and 35 dB of gain at a frequency of 8.2 to 8.6 GHz. Antenna system noise temperature is less than 50 K from 7.2 to 9.4 MHz. The low noise HEMT amplifier system is intended for use as a radio astronomy or space communications receiver front end

A 2.3-GHz cryogenically cooled HEMT amplifier for DSS 13

A prototype 2.3 GHz (S band) high electron mobility transistor (HEMT) amplifier/closed cycle refrigerator (CCR) system was installed in the DDS-13 feedcone, replacing the 2.3 GHz maser. The amplifier is cryogenically cooled to a physical temperature of 12 K and provides 31.5 K antenna system noise temperature and 29 dB of gain. The HEMT device used in the amplifier is a prototype

Incommensurate-Commensurate Magnetic Phase Transition in SmRu2_{2}Al10_{10}

Magnetic properties of single crystalline SmRu$_{2}$Al$_{10}$ have been investigated by electrical resistivity, magnetic susceptibility, and specific heat. We have confirmed the successive magnetic phase transitions at $T_{\text{N}}=12.3$ K and $T_{\text{M}}=5.6$ K. Resonant x-ray diffraction has also been performed to study the magnetic structures. Below $T_{\text{N}}$, the Sm$^{3+}$ moments order in an incommensurate structure with $q_1=(0, 0.759, 0)$. The magnetic moments are oriented along the orthorhombic $b$ axis, which coincides with the magnetization easy axis in the paramagnetic phase. A very weak third harmonic peak is also observed at $q_3=(0, 0.278, 0)$. The transition at $T_{\text{M}}$ is a lock-in transition to the commensurate structure described by $q_1=(0, 0.75, 0)$. A well developed third harmonic peak is observed at $q_3=(0, 0.25, 0)$. From the discussion of the magnetic structure, we propose that the long-range RKKY interaction plays an important role, in addition to the strong nearest neighbor antiferromagnetic interaction.Comment: 11 pages, 12 figures, accepted in PR

Brown-Henneaux's Canonical Approach to Topologically Massive Gravity

We analyze the symmetry realized asymptotically on the two dimensional boundary of AdS_3 geometry in topologically massive gravity, which consists of the gravitational Chern-Simons term as well as the usual Einstein-Hilbert and negative cosmological constant terms. Our analysis is based on the conventional canonical method and proceeds along the line completely parallel to the original Brown and Henneaux's. In spite of the presence of the gravitational Chern-Simons term, it is confirmed by the canonical method that the boundary theory actually has the conformal symmetry satisfying the left and right moving Virasoro algebras. The central charges of the Virasoro algebras are computed explicitly and are shown to be left-right asymmetric due to the gravitational Chern-Simons term. It is also argued that the Cardy's formula for the BTZ black hole entropy capturing all higher derivative corrections agrees with the extended version of the Wald's entropy formula. The M5-brane system is illustrated as an application of the present calculation.Comment: 29 pages, no figure, references adde

Towards more exoticness—X-ray spectroscopy of Ξ− atoms at J-PARC

Atoms with a doubly-strange hadron, namely Ξ−, are really exotic and interesting objects. We are planning to measure X rays from Ξ− atoms for the first time at J-PARC, where a high intensity and high quality kaon beam is available. Our purpose is to obtain the strength of the optical potential, and hence to provide information on the Ξ-N interaction which is currently very poorly known. We can accumulate several thousand counts of X rays and determine the level energy shift down to ~0.05 keV. This is sensitive enough to observe the expected level shift (~1 keV) with reasonable accuracy, while the sensitivities for the level width is somewhat weaker (measurable down to ~1 keV)

Optical-logic-array processor using shadowgrams. III. Parallel neighborhood operations and an architecture of an optical digital-computing system

This paper was published in Journal of the Optical Society of America A and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/JOSAA.2.001245 Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law

Compact compound-eye projector using superresolved projection

This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the owing URL on the OSA website: http://dx.doi.org/10.1364/OL.36.000121 Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is rohibited and is subject to penalties under law

OPALS : optical parallel array logic system

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/AO.25.001565 Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law

Modular components for an optical array logic system

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/AO.26.003954 Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law