1. A New Polarimeter for the 40m Telescope

2. Our Team Tony Readhead Timothy Pearson Kieran Cleary Oliver King
Vasiliki Pavlidou
Rodrigo Reeves
Martin Shepherd
Walter Max-Moerbeck
Joseph Richards
Matthew Stevenson
Kirit Karkare

3. FPGAs at OVRO

4. 40m Telescope

5. Blazars
Active galactic nuclei are driven by accreting supermassive blackholes at the centres of galaxies.
Symmetrical jets are accelerated and fueled by the inflow.
Orientation of the system relative to line-of-site determines appearance.
Blazars are observed when line-of-site is aligned with the jets.

6. Blazars Details of jet physics remain mysterious.
Include: acceleration, collimation, emission, and composition.
Correlated emission is a means to understand these systems.

7. Fermi Fermi Gamma-ray Space Telescope launched June 11, 2008.
LAT surveys the entire sky every three hours.
Observing several hundred blazars.
Complementary observations are underway across the EM spectrum.

8. 40m Telescope
Dedicated Ku-band monitoring campaign began in summer of 2007.
Observing more than 1100 blazars twice per week.
Reach 10 mJy in 64s integration.

9. CGRaBS
(Healey et al, 2008)

10. Light Curves

11. Current Receiver
Dicke-switch design.
3GHz bandwidth
Tsys = 30K

12. Current Receiver Dicke switch radiometer. 3GHz bandwidth.
30K system temperature.
But…
Nobody makes Dicke switches anymore.
Beams under-illuminate the dish.
There’s always room for improvement.

13. Plans for New Receiver

14. Planned Receiver Analog front-end: Digital back-end:
Heterodyne, correlation polarimeter.
Stokes I, Q, and U.
6GHz bandwidth.
20K system temperature.
Digital back-end:
Covers twelve 500-MHz bands using 12 ROACH boards, 24 iADCs.
Moderate spectral resolution.
Programming for each is identical.

15. Design Flexibility
Receiver has the flexibility for new experiments, only requiring re-programming of FPGAs.
Higher resolution spectroscopy, raw voltage storage, RFI excision, etc.

16. Modular Design Full bandwidth is split over 12 sub-bands.
Each sub-band is semi-independent, allowing for a subset to be built at first.
We can then increase bandwidth by simply adding more sub-bands.

17. Current Status Preparing with assembly of first sub-bands.
Gateware development is underway.
Detailed design of horns, cryostat, and mixer boards to follow in early 2010.
Commissioning by end of next year.