1. Thoughts on Ground-based lensing measurements Chao-Lin Kuo Stanford/SLAC KIPAC

2. The primordial, Gaussian E-polarization

3. Large Scale Structure

4. B-polarization J Tolan

5. Lensing B-polarization is a LSS experiment Deep polarization measurements (4  K rms) on 1.5% of the sky can significantly improve Planck+SNAP constraints on {w 0, w a,  k, ∑m }, p  =w   w=w 0 +w a (1-a) There is a strong theoretical preference: w 0 = -1, w a =0,  k <10 -4 → lensing B provides a constraint on ∑m Hu, Huterer and Smith, 2006

6. The Status of B-Polarization Measurements (07/2009) QUaD/BICEP (50~100 detectors) still miss the (lensing) B-polarization by ~ 2 orders of magnitude. The current round of experiments (~1000 detectors) can only hope for a statistical detection. To perform high S/N imaging of lensing B-polarization, one must increase the survey speed by 10 2. The ground based platforms (DASI “drum”, SPT) will be maxed out already in the current round of exp. Chiang et al. Lensing B-mode Gravity wave r=0.1

7. The simple strategy to get ~10,000 detectors on the sky… Use an optical design that has the largest possible focal plane area Choose an aperture size that optimizes throughput/dollar

8. Optics Comparison H. Tran et al., CMBPOL Technology Workshop, 2008 Crossed Dragone Gregorian Strehl Ratio The advantage of a crossed-Dragone system (1). > 4X more FOV area than a Gregorian (2). Flat/telecentric focal plane, no re-imaging Optics -Good polarization properties verified in numerous studies The required primary aperture for lensing B-mode is ~2 meters – for 10m class telescopes the measurements will be sensitivity (throughput) limited, not resolution limited.

9. The simple strategy to get ~10,000 detectors on the sky… Use an optical design that has the largest possible focal plane area Choose an aperture size that optimizes throughput/dollar The Proposed Experiment:The Proposed Experiment: An array of 5-10 crossed-Dragone multifrequency telescopes, each with ~2-meter primary aperture and ~2,000+ detectors An array of 5-10 crossed-Dragone multifrequency telescopes, each with ~2-meter primary aperture and ~2,000+ detectors

10. A Pilot Project: one 1.5-2m telescope Serving as the prototype for two experiments –Pol-Len: Polarimeter array for Lensing –EPIC-IM (in collaboration w/ JPL) The telescope will be integrated with –Room temperature sources/detectors –A BICEP-2 style 512-detector bolometric receiver –A larger format camera – see the next page Many issues can be characterized in full details with this pilot projet: –Near and far sidelobe responses, baffling –Infrared filtering –Magnetic field shielding –Detector loading –Mitigation of polarization systematics

12. The expansion prospects 1 Telescope + 512 * bolometers 1 Telescope + 2,000 bolometers 5 Telescopes, each w/ 2,000 bolometers LDRD funds 1 Telescope Deployment for field observations (minor technology dev. required) 1 Telescope + 8,000 bolometers 5-10 Telcps., each w/8,000 detectors (major technology dev. required) EPIC-IM mission * # of detectors projected for 150 GHz data/design feedback

13. warm baffle receiver cryostat Vacuum window The “major” technology development By reducing the size of the feeds we can pack more detectors (~4x) onto the focal plane (~1.5 f ) The price to pay is increased spillover – which must be intercepted at 4K 8,000 detectors to read per dewar Zotefoam Teflon (50 k) HR-10 OFHC (4K) IR filter cold stop

14. Also a great gravity wave B-mode experiment (for r<0.1) Smaller maps → lower noiseSmaller maps → lower noise Smaller maps → potentially less foregroundSmaller maps → potentially less foreground Small beams → de-lensing possibleSmall beams → de-lensing possible Small beams → less Beam systematicsSmall beams → less Beam systematics Compared to degree beam experiments (BICEP/Keck, ABS), a 2 m class telescope offers: 3.6 deg 7.2 deg 14.4 deg 28.8 deg (Polarized Dust, 5%)

15. The Trade-offs No Half-Wave-Plate modulators. No full - rotation. Modulation relies on scanning – QUaD/BICEP style. For the same, 2 possible angles can serve as a systematic check.

16. Funding/fielding prospects SLAC “LDRD” under review (1 telescope, warm tests) An NSF proposal will go in this August (“Pol-Len1”, one telescope +mount+ receiver development) BICEP/Keck collaboration supportive of the deployment of the telescope to the South Pole DSL site in 2011. Pending approval from NSF-OPP (office of polar programs). We have not thought about how to fund the full array…Let me know if you have $ or are interested.

17. The End. Question?