1. 1 CMB Polarimetry with BICEP: Probing Inflationary Gravitational Waves IAS - Polarization 2005 Denis Barkats

2. 2 Background Imager of Cosmic Extragalactic Polarization Caltech / JPL Andrew Lange Denis Barkats John Battle James Bock Cynthia Chiang Darren Dowell Greg Griffin Viktor Hristov Eric Hivon John Kovac Chao-Lin Kuo Pete Mason Hien Nguyen Ian Sullivan Ki Won Yoon UC Berkeley Bill Holzapfel Yuki Takahashi UC San Diego Brian Keating Evan Biermann Tom Renbarger CEA Grenoble Lionel Duband Cardiff Peter Ade

3. 3 State of the CMB polarization field in August 2005 EE and TE polarization BB polarization Upper limits ~ 2  K 2 (from DASI, CBI, B03) T/S < 0.36 from CMB+LSS WMAP BOOMERANG 03 CBI DASI CAPMAP What do we need? Significant advance system sensitivity Control systematic errors at < 0.1  K levels Distinguish CMB from Galactic Foregrounds Distinguish Gravity-wave Signal from Lensing BICEP

4. 4 Overview of the BICEP instrument 10 cm thick Zotefoam window IR-blocking filters Cold polyethylene lenses Feed horn array Helium sorption refrigerator Cryostat PSBs Faraday rotators Minimize polarization systematics Simple refractor, no mirrors Azimuthal symmetry Alt-az telescope, with continuous boresight rotation Wide-band polarization modulation with FRMs Optimize to 10 < < 400 Beam sizes ~ 1 deg, 0.6 deg Field of view ~ 17 deg Observed sky fraction ~ 5% Separate CMB / foregrounds Two frequency bands at 100 and 150 GHz Signal-to-noise considerations 49 light PSB pairs at 250 mK (98 bolos) Multiple levels of modulation South Pole location: long integration over contiguous patch of sky, reduced atmospheric loading

5. 5 Photon Parallel metal lines, Polarization in x-axis Polarization in y-axis New Technology: Polarization Sensitive Bolometers Courtesy of Jamie Bock, NASA JPL

6. 6 Cryostat and mount Az-El mount + boresite rotation Upward-looking cryostat with toroidal LN2 / LHe tanks Long hold time (4-5 days) Helium sorption fridge to cool focal plane to 250 mK Rotation essential for map cross-linking 4He, 1.5 K 3He, 350 mK 3He, 250 mK Hold time ~ 2 days, cycle ~ 5 hours

7. 7 Zotefoam windowTeflon IR-blocking filters 25 cm 180 cm Polyethylene lenses Front-end optics Telecentric design for flat focal plane AR-coated filters and lenses Cross-polarization < 0.01%, instrumental polarization < 1% from physical optics simulations

8. 8 The BICEP insert All RF-sensitive components enclosed in large faraday cage Drop-in focal plane Trussed structure to isolate 250 mK plate from 4 K Cold JFETs for signal buffering, refrigerator, thermal connections to focal plane Lens tube mounted on top of insert

9. 9 100 GHz 150 GHz Image: J. Kovac Full focal plane map 49 spatial pixels = 98 polarization- sensitive bolometers Divided into 6 similar hextants Each hextant has 4 pixels at each band Adjacent hextants measure Q and U.

10. 10 A closer look at the focal plane A photon's view of the focal plane Primary beam-defining feed horn (4 K) Re-expanding horn (4 K) Band-defining metal mesh filters, baffles Refocusing horn (250 mK) Polarization- sensitive bolometers Faraday rotator module Image: K. Yoon

11. 11 Home, sweet (frozen) home: South Pole station, Antarctica “100 GHz band” Bandwidth: 24 GHz Optical efficiency:27.5% “150 GHz band” Bandwidth: 41 GHz Optical efficiency:25%

12. 12 What can BICEP do for you? - Measure EE polarization at intermediate, complementary to current detections BB polarization: if anyone's gonna do it (in the next N years), we will! - Return information on polarized foreground emission 1 year of Planck ~ 6 x sensitivity of 8 years of WMAP BICEP has similar instantaneous sensitivity to polarization as Planck, and is more sensitive to peak BB signal due to concentration on a small patch of sky Detect BB polarization if T/S > 0.05 (assuming “reasonable” integration time), otherwise set a bomber upper limit N ~ number of years before SPIDER, EBEX, CMBpol, Planck etc. - Winter 2005 / 2006: deployment to south pole http://www.astro.caltech.edu/~lgg/bicep_front.htm

13. 13 Expected BICEP performance System NET ~ 35 uK√s (350 uK√s per PSB, 98 detectors) Total integration time: somewhere between 100 days and 200 days Observed sky fraction ~ 5% Beam width ~ 1 degree EE BB T/S = 0.05 and  = 0.17