Submillimeter-wave Detectors for Extremely Distant Objects of Universe

Fundamental limit of distances accessible for observer Ro~ c·To about 10-20 billion light years. To is the present age of Universe To ~ 1/Ho. Habble constant Ho is experimentally determined by effect of galaxies moving away. Cosmic Microwave Background (CMB) is a relic of time when Universe was 10-5 of its present age. The spectrum of CMB was measured by bolometric instrument FIRAS on board of COBE satellite. NEPbol=10-14 W/Hz1/2.
Probably first bright objects in Universe appeared in time about (0.1-0.5)To. (R/Ro~ 0.1-0.5, redshift z~1-10. Evidently it was a period of formation of the modern complex structure of Universe. Most of sources are bright in submillimeter region and are invisible in optics as was shown by observation with ground-based SCUBA bolometer array. NEPbol=10-16 W/Hz1/2.
The background is remarkably uniform. A measured CMB anisotropy is about 10-5 of its isotropic level. The anisotropy of CMB was measured by bolometric instruments with balloon telescopes BOOMERANG and MAXIMA. NEPbol=2·10-17 W/Hz1/2.
Limits of detectors sensitivity at low background [Gromov,1983] are different for bolometric and coherent receivers. Fundamental advantage of direct detectors against mixer receivers is a possiblility of unrestricted reducing of noise, while for coherent receivers noise temperature can not be less approximatly hν/k.
Spider Web Bolometer - Highest Achievment of the End of Former Millenium (ideal for non-Cooled Telescope and 1 source observation). NEPbol=10-17 W/Hz1/2.
US Bolometer Team: Need in Novel Technologies
Andreev-Bolometer. NEPbol=10-18 W/Hz1/2. Nanometric bolometer at temperature of milli-Kelvins is subject for "Andreev physics". A mesoscopic region, where dominate Andreev reflection, Andreev conductance, Andreev interferometry, Andreev current, Andreev levels, Andreev scattering, Andreev tunneling, Andreev channels, Andreev orbit, Andreev states and Andreev billiard.
Comparative Table More than Order Magnitude Improvement by use of antenna-coupled nano-bolometer instead of semiconductor spider-web or other composite bolometer
Imaging: mapping, sky survey. Spatial Sampling Problems for Feed-Horn Bolometers Arrays. A "jiggle pattern" needs 15 additional steps for full sampling of a map.
Antenna-Coupled Bolometers. Two concepts. 1) Tunnel Junction Sensor (used in chip made in Chalmers and shown on a picture) 2) Transition Edge Sensor (TES) Richards in Berkeley, JPL, Caltech
TES bolometer Advantage: Approved technology for sensor's connections (Andreev mirrors) A drawback: Background Problem. Contradiction between sensitivity and workability in bright region of sky.
Cold Electrons Bolometer (Chalmers) Noise improvement Background change adaptation Internal cooling reduces requirements for external cooling system
SQUID circuit
Practical Realization, CCNHEB, Cr Technology

Gromov V.D. Quantum limit of radiation detectors at nonisothermal background. Space Research Institute, USSR Academy of Sciences, Moscow, 1983.

Noise Equivalent Power, NEP = δP/(Δf)^1/2, where δP is r.m.s. noise in power units.

In radioastronomical temperature units, a "Rayleigh-Jeans" brightness temperature T ^RJ = I_ν·λ²/k has advantage of linear dependance from power values in difference to T_br calculated by Planck formula.

Let detector is an ideal single mode device sensitive to single polarization component and providing diffraction limited angular resolution, input (RF) bandwith Δν, output (LF) bandwith Δf. All signal and noise values are reduced to input of the detector. I_ν is a surface brightness in power units.

A signal is ΔP = ΔI_ν·λ²Δν/2 or ΔT ^RJ = ΔI_ν·λ²/2k, ΔP =Δν·kΔT ^RJ.

For Δν/ν=0.25

A noise limit of power (quadratic) detector is δP = hν·[n(n+1)ΔνΔf]^1/2,

or δT ^RJ = (hν/k)·[(n(n+1)Δf /Δν]^1/2,

where n = I_ν·λ³/(2hc) is defined by background brightness I_ν.

A noise limit of linear receiver is δP = hν·(n+1/2)·[ΔνΔf]^1/2,

or δT ^RJ = (hν/k)(n+1/2)·[Δf /Δν]^1/2.