TDP DevelopmentTDP Development

Feed Improvements

Jack Welch, Matt Fleming

GOALGOAL

• Lower Tsys by further cooling of the feed

ATA Feed

Current feed through design for ATA 1 – tip circuit board , 2 – .0085 inch wire, 3 - .014 inch hollow needle, 4&5 – Teflon matching lens, 6 – feed through into dewar.

Heat Loads Heat Loads (in Watts)(in Watts)

IR within the dewar 0.23 W

Heat flow along the pyramid 1.70 W

Heat flow along the feed arms 1.00 W

IR load on feed arms and

Pyramid 0.11 W

LNA dissipation 0.12 W

Output cables 0.048 W

3.20 W

Feed test facility atMinex Engineering

Y F

acto

r

Tre

ceiv

er in

K

64

137

40

95

168

TTsyssys Improvements Improvements• Measured receiver/feed Trcv ~ 64 K for 5-10 GHz• TLNA ~ 10 K, leaving 54 K as resistive contribution• Temperature scaling: 70/280 = 0.25• [conductivity scaling]1/2 = 0.3 • Total scaling = 0.08• 54 x 0.08 = 4 K

LNA 10 K Background 10 K Resistive losses 4 K

Anticipated total Tsys 24 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.