arXiv subjects

T. A. Marriage

Publications and source records attributed to T. A. Marriage.

21 records · Page 2Linked to original sources

arXiv2007

A millimeter-wave antireflection coating for cryogenic silicon lenses

We have developed and tested an antireflection (AR) coating method for silicon lenses at cryogenic temperatures and millimeter wavelengths. Our particular application is a measurement of the cosmic microwave background. The coating consists of machined pieces of Cirlex glued to the silicon. The measured reflection from an AR coated flat piece is less than 1.5% at the design wavelength. The coating has been applied to flats and lenses and has survived multiple thermal cycles from 300 to 4 K. We present the manufacturing method, the material properties, the tests performed, and estimates of the loss that can be achieved in practical lenses.

astro-ph↗

arXiv2005

CMB Observations with a Compact Heterogeneous 150 GHz Interferometer in Chile

We report on the design, first observing season, and analysis of data from a new prototype millimeter-wave interferometer, MINT. MINT consists of four 145 GHz SIS mixers operating in double-sideband mode in a compact heterogeneous configuration. The signal band is subdivided by a monolithic channelizer, after which the correlations between antennas are performed digitally. The typical receiver sensitivity in a 2 GHz band is 1.4 mK sqrt(s). MINT observed the cosmic microwave background (CMB) from the Chilean Altiplano. The site has a median nighttime atmospheric temperature of 9 K at zenith (exclusive of the CMB). Observations of Mars, Jupiter, and a telescope-mounted calibration source establish the system's phase and magnitude stability. MINT is the first CMB-dedicated interferometer to operate above 50 GHz. The same type of system can be used to probe the Sunyaev-Zel'dovich effect in galaxy clusters near the SZ null at 217 GHz. We present an analysis of sideband-separated, digitally sampled data recorded by the array. Based on 215 hours of data taken in late 2001, we set an upper limit on the CMB anisotropy in a band of width Delta ell=700 around ell=1540 of delta T < 105 microK (95% conf). Increased sensitivity can be achieved with more integration time, greater bandwidth, and more elements.

astro-ph↗

arXiv2002

A perspective on the CMB acoustic peak

CMB angular spectrum measurements suggest a flat universe. This paper clarifies the relation between geometry and the spherical harmonic index of the first acoustic peak ($\ell_{peak}$). Numerical and analytic calculations show that $\ell_{peak}$ is approximately a function of $Ω_K/Ω_M$ where $Ω_K$ and $Ω_M$ are the curvature ($Ω_K > 0$ implies an open geometry) and mass density today in units of critical density. Assuming $Ω_K/Ω_M \ll 1$, one obtains a simple formula for $\ell_{peak}$, the derivation of which gives another perspective on the widely-recognized $Ω_M$-$Ω_Λ$ degeneracy in flat models. This formula for near-flat cosmogonies together with current angular spectrum data yields familiar parameter constraints.

astro-ph↗