CMB Polarimetry with BICEP Probing Inflationary Gravitational Waves

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

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

State of the CMB polarization field in August 2005 EE and TE polarization WMAP BOOMERANG 03 CBI DASI CAPMAP BICEP What do we need? • Significant advance system sensitivity BB polarization • Control systematic Upper limits ~ 2 m. K 2 errors at < 0. 1 m. K levels • Distinguish from Galactic Foregrounds (from DASI, CMB CBI, B 03) T/S < 0. 36 from CMB+LSS Signal from Lensing • Distinguish Gravity-wave

Overview of the BICEP instrument 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% 10 cm thick Zotefoam window IR-blocking filters Cold polyethylene lenses Feed horn array Faraday rotators PSBs Separate CMB / foregrounds • Two frequency bands at 100 and 150 GHz Signal-to-noise considerations • 49 light PSB pairs at 250 m. K (98 bolos) • Multiple levels of modulation • South Pole location: long integration over contiguous patch of sky, reduced atmospheric loading Helium sorption refrigerator Cryostat

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

Upward-looking cryostat with toroidal LN 2 / LHe tanks Cryostat and mount Long hold time (4 -5 days) Helium sorption fridge to cool focal plane to 250 m. K Az-El mount + boresite rotation Rotation essential for map cross-linking 4 He, 1. 5 K 3 He, 350 m. K 3 He, 250 m. K Hold time ~ 2 days, cycle ~ 5 hours

25 cm Front-end optics 180 cm • Telecentric design for flat focal plane • AR-coated filters and lenses • Cross-polarization < 0. 01%, instrumental polarization < 1% from physical optics simulations Teflon Zotefoam IR-blocking window filters Polyethylene lenses

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

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

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

Home, sweet (frozen) home: South Pole station, Antarctica “ 150 GHz band” “ 100 GHz band” Bandwidth: 24 GHz Bandwidth: 41 GHz Optical efficiency: 27. 5%Optical efficiency: 25%

What can BICEP do for you? - Winter 2005 / 2006: deployment to south pole - Return information on polarized foreground emission - Measure EE polarization at intermediate , complementary to current detections BB polarization: if anyone's gonna do it (in the next N years), we will! N ~ number of years before SPIDER, EBEX, CMBpol, Planck etc. 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 http: //www. astro. caltech. edu/~lgg/bicep_front. htm

Expected BICEP performance System NET ~ 35 u. K√s (350 u. K√s per PSB, 98 detectors) EE BB Total integration time: somewhere between 100 days and 200 days Observed sky fraction ~ 5% Beam width ~ 1 degree T/S = 0. 05 and t = 0. 17

A day in the life of a BICEPer

BICEP ELECTRONICS BACKPACK ELECTRONICS BOX “DIRTY” DIGITAL COMPARTMENT RF FILTER “CLEAN” ANALOG COMPARTMENT ROTARY JOINT POWER REGULATORS

Band "100 GHz" "150 GHz" Band Center 95. 4 GHz 151. 5 GHz Effective Bandwidth 23. 8 GHz (24. 9%) 41. 2 GHz (27. 2%) 27. 5% 25. 0% Band-averaged optical efficiency

TYPICAL BOLOMETER CHARACTERISTICS Upper limit on scanning speed set by the time constant: ~ 0. 25 (FWHM) / opt = 10. 5 deg/s … is not a limiting factor.

Band "100 GHz" "150 GHz" Band Center 95. 4 GHz 151. 5 GHz Effective Bandwidth 23. 8 GHz (24. 9%) 41. 2 GHz (27. 2%) 27. 5% 25. 0% Band-averaged optical efficiency “ 100 GHz band” Bandwidth: 24 GHz Optical efficiency: 27. 5% “ 150 GHz band” Bandwidth: 41 GHz Optical efficiency: 25%

QUAD Electronics in Operation VME DAS Thermometry readout PID Controller 128 ch ADC DIO Cards Real time computer Interface boxes RF-filtering Digital B. O. B. Electronics boxes 4 x lockin Power supplies 1 x bias 1 x F. P. T. C. 1 x GRT amp 19

QUAD Electronics Overview • 96 channels of readout – 62 light bolometers – 4 darks – 3 thermistors – Ample spares • Cold JFET amplifiers • AC biased / lockin demodulation • Focal plane temp. control • Fully computer controlled QUAD Amplifier Box (1 of 4) 20

QUAD Readout Electronics summary Bias Generator • AC / DC • Freq: 40 – 200 Hz • Amp: 0. 36 m. V steps cryostat • Fully computer controlled Lockin Cards • DC-offset removal Gain: 100, 000 (nominal) Proven Design 97, 000 (at DC) • Bolocam 91, 500 (at 90 Hz) • Su. ZIE • BOOMERANG • Phase adjustment 45° range at 90 Hz, 7 -bit resolution • Fully computer controlled 21

BICEP BOLOMETER READOUT ELECTRONICS RF-TIGHT FARADAY CAGE PREAMPS & SIGNAL CONDITIONERS RB RL LPF DIGITAL LOCKINS (DLIAS) RF FILTER COLD JFETS AC / DC Bias. Gen. RF FILTER RL ADC MSP CPLD RF FILTER SYNCH, HSCK, CMD AC / DC SYNCH, HSCK SPI CONTROLLERS SPI ETHERNET CARDS OPTICAL FIBER ETHERNET HUB DAQ PC

BICEP NOISE MEASUREMENTS

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10 cm-thick Zotefoam window OPTICAL CHAIN AND FILTERING 270 K 77 K Teflon blockers 20 K 4 K Band 100 GHz Edge filter B 829 B 647 (3. 65 cm-1) (5. 9 cm-1) 2 nd blocker B 822 (4. 0 cm-1) B 807 (5. 77 cm-1) Polyethylene lenses 3 rd blocker B 657 (6. 6 cm-1) B 712 (8. 5 cm-1) FRM Waveguide cut-on 150 GHz 83 GHz 130 GHz (2. 77 cm-1) (4. 33 cm-1) 250 m. K