AAS 207th Meeting, 8-12 January 2006
Session 88 Advanced Radio, Millimeter and Sub-mm Instruments
Oral, Tuesday, 10:00-11:30am, January 10, 2006, Salon 1

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[88.02] A 90 GHz Array for the Green Bank Telescope

S.R. Dicker, M.J. Devlin (University of Pennsylvania), D.J Benford (Goddard Space Flight Center), K.D. Irwin (NIST), B.S. Mason, P.M. Korngut (NRAO, Green Bank), C. Tucker (Cardiff University, UK)

We report on the design and construction of the Penn Array Receiver, a 64 element array which will be a 90 GHz facility instrument for the 100 m Green Bank Telescope. Each array element is a transition edge sensor bolometer. Detector noise will be background limited by the random arrival of photons and in one hour we expect to be able to map a 5 arcminute square of sky to 80 \muJy at a resolution of 8 arcseconds.

No feed horns are used, instead cooled high-density polyethylene lenses and a cold (3 K) Lyot stop control the illumination of the telescope. Capacitive mesh filters act as IR blockers and define a bandpass of 86—94 GHz. The array elements are spaced by 0.5 f \lambda so that the sky is fully sampled in a single pointing of the GBT. This significantly simplifies the scanning patterns needed for sparser arrays.

The detectors are cooled to 0.25 K using a pulse tube cooler and helium sorption refrigerators. The cryogenics along with all the electronics and the computer system have been successfully operated on the GBT. By February, detailed tests on the response of the detectors will allow us to further develop the data processing techniques needed to remove atmospheric noise from the data and beam measurements of the cryostat will confirm that the optical design is correct. We are also developing better control software to automatically bias the SQUID multiplexed readout.

This work is funded by grants from the National Radio Astronomy Observatory and NASA.

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