1. Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array Phased Array Feed Development FAST Visitors, July 23, 2010 – Charlottesville, Va Rick Fisher

2. Phased Array Feed Project Collaboration with Brigham Young University First PAF demo 1997 on 43-m telescope Objective: Maximize A 2 eff Ω/T 2 sys Key technical challenges – Compensation for mutual coupling between array elements – Noise reduction with cryogenics 2

3. Beamforming 3 LNAs FPA Receiver Chains Reflector Digital Beamforming

4. Formed Beam Patterns 4 Source: Cas A, 1612 MHz 0.1 degree pointing grid

5. Cygnus X Region Mosaic 5 Canadian Galactic Plane Survey Convolved to 20-m Beam

6. Noise Budget (Uncooled Array) 6 Measured Model LNA T min 33 K 33 K Noise coupling20 K 23 K Spillover 5 K 5 K Sky 3 K 3 K Loss 4 K -- T sys :65 K 64 K ----------

7. Next Steps 7

8. Dewar Close-up 8 1020 Refrigerator LNA – Antenna Element Interface

9. Cryogenic Amplifier Interface 9 Interface to Antenna Element (@300K, at least initially) Dual Channel LNA (@15K)

10. Development System Evolution 10

11. Final Configuration 11

12. First Science PAF Instrument 7-Beam, 19-Element Array on GBT Tsys 0.7 450-MHz R.F. Bandwidth 300 MHz Beamformer with Pulsar Search Capability 12 http://science.nrao.edu/paf