Huan T. Tran UC Berkeley POLARBEAR : Polarization of Background Radiation Huan T. Tran 1

University of California at Berkeley Kam Arnold Daniel Flannigan Wlliam Holzapfel Jacob Howard Zigmund Kermish Adrian Lee P.I. Marius Lungu Mike Myers Roger O'Brient Erin Quealy Christian Reichardt Paul Richards Chase Shimmin Bryan Steinbach Huan Tran P.M. Oliver Zahn Lawrence Berkeley National Lab Julian Borrill Christopher Cantalupo Theodore Kisner Eric Linder Helmuth Spieler University of Colorado at Boulder Aubra Anthony Nils Halverson University of California at San Diego David Boettger Brian Keating George Fuller Nathan Miller Hans Paar Ian Schanning Meir Shimon Imperial College Andrew Jaffe Daniel O’Dea Laboratoire Astroparticule & Cosmologie Josquin Errard Joseph Martino Radek Stompor KEK Masashi Hasumi Haruki Nishino Takayuki Tomaru McGill University Peter Hyland Matt Dobbs Cardiff University Peter Ade Carole Tucker POLARBEAR Collaboration 2

Large Format Antenna-coupled TES bolometer arrays Frequency-Multiplexed Readout Monochromatic – switch focal planes for different frequencies Polarbear concept POLARBEAR Concept HWP Modulator stepped/continuous Low Spurious Polarization Optics Stringent Ground Shielding/monolithic primary Located in Chile for Sky Rotation Key designs for Systematic Control Test phase in California- Cedar Flat Key Technologies for Sensitivity 3 Eric Chauvin-General Dynamics (Vertex)

POLARBEAR Telescope 4’ at 150 GHz: Constrain Lensing Large FOV: 2.4 deg Relatively compact Monolithic central primary Flat-telecentric focal plane Cold Lyot Stop 3.5m Clear aperture (2.5m active) Dragone-Gregorian Cold Reimaging Optics 4

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POLARBEAR mirrors Primary: RMS 53 micron Secondary: RMS 37 micron 6

POLARBEAR Receiver Three UHMWPE lenses Cold Lyot Stop Telcentric Focal Plane Cold Reimaging Optics Cryomech Pulse-tube cooler Simon-Chase ‘He10’ refrigerator now demonstrated with APEX/SPT Cryogenics 2m Rotating HWP Skyward of lenses Field Stop 7

POLARBEAR Array 7 Hexagonal wafers in Chile 2 Wafers at Cedar Flat 637 Pixels/ GHz Si Lenslet Si Wafer Pixel pair Antenna Filter Bolometer 8

9 Polarization Purity Receiver Spectrum POLARBEAR Detector performance Beam map E-Plane

10 POLARBEAR DfMUX Readout capacitors inductors Bolometer wafer FPGA-based Oscillator-Demodulators NIST squids

POLARBEAR HWP rotation mechanism 28cm Drive Idler Pawl Designed for both continuous and stepped rotation Ball bearing Belt driven / stepper motor Optical encoder readout ~Arcsec repeatability (stepped) Single plate Sapphire (not shown) AR coated with TMM ~70K Tooth 11

POLARBEAR Groundshielding Goal: Ground must be suppressed by ~10 9 Cylindrically symmetric Curved panels Extra tall to shield mountains 12

Systematic errors Atmosphere Ground/sidelobes Polarization Calibration Beam Distortions Foregrounds Band mismatch Telescope flexure Ghost reflections Beam Measurement Scan Strategy Small beam size HWP HWPSS 13 Array Temp stability

Scan Strategy Scan in AZ, fixed EL ~ 1 hour Re-center scan each hour Choose centers for uniformity Choose HWP stepping scheme Maps ground pickup template each hour 14

Scan Strategy: optimizing polarization uniformity Sky rotation gives some uniformity Continuous HWP is ideal-> null many effects Can choose steps wisely f 1 : Measure of quad-pole non- uniformity polarization coverage f 2 : dipole and oct-pole non-uniformity Step HWP 3 times, once per day 15

DiffGain DiffFWHM DiffPointing DiffEllipticity DiffRotation POLARBEAR Parameter Tolerances Instrumental leakage Suppression due to modulation

Beam effect Suppression Differential gain Diff Rotation Suppression w/ stepped HWP Suppression With sky rot Diff Beam Width Diff Ellipticity small beams => Peak in leakage at high-l Diff Pointing lensing 17 Beam constrained 10 -3

Foregrounds and Scan Regions Scan is targeted at low dust contrast regions as low as ~2uK intensity 150,220 GHz bands Patches chosen to match QUIET 18

POLARBEAR Performance Red error bars: Includes noise increase from subtracting 220 GHz to remove mid lat dust 19

Experiment Summary Frequencies150/220GHz Angular resolutions7’ :90GHz 4’ :150GHz 2.7’:220 Ghz arcmin at each freq Field centers and sizesCoord w/ QUIET 1000 sq-Deg total Ra/Dec/Sq-Deg Telescope typeGregorian/lenses Refractor, Gregorian, Compact- range etc Polarization ModulationsHWP, sky rot Waveplate, boresight rot., sky rot., scan etc. – list all that apply Detector typeBolometer/TES LocationAtacama Instrument NEQ/U360/sqrt(1288/4) =20  K s 1/2 for both Q and U Observation start date2010 Planned observing time1000/250Elapsed/effective days Projected limit on r % c.l.<10X foreground removal 20

Polarbear concept POLARBEAR Deployment  Testing phase at Cedar Flat  Telescope assembly underway  First light in months  Test stepped vs continuous HWP  Test for atmospheric removal 21