TDP Development Feed Improvements Jack Welch, Matt Fleming

GOAL Lower Tsys by further cooling of the feed

ATA Feed

Current feed through design for ATA 1 – tip circuit board, 2 –.0085 inch wire, inch hollow needle, 4&5 – Teflon matching lens, 6 – feed through into dewar.

Heat Loads (in Watts) IR within the dewar0.23 W Heat flow along the pyramid1.70 W Heat flow along the feed arms1.00 W IR load on feed arms and Pyramid0.11 W LNA dissipation0.12 W Output cables0.048 W 3.20 W

Feed test facility at Minex Engineering

Y Factor T receiver in K

T sys Improvements Measured receiver/feed Trcv ~ 64 K for 5-10 GHz T LNA ~ 10 K, leaving 54 K as resistive contribution Temperature scaling: 70/280 = 0.25 [conductivity scaling] 1/2 = 0.3 Total scaling = x 0.08 = 4 K LNA10 K Background10 K Resistive losses 4 K Anticipated total Tsys24 K 

Left panel: results of calculations on plane wave incident onto flat glass pane. The reflection coefficient is in blue and the return loss is in red. Right panel: the results of calculation assuming two layers of anti-reflection coating with thicknesses and spacings as indicated in the inset.