LiteBIRD LNPC17, April 19-21 @ PACIFICO Yokohama Satoru Uozumi (Okayama Univ.) for the LiteBIRD Phase-A1 team １ LiteBIRD Lite (Light) Satellite for the studies of B-mode polarization and Inflation from cosmic background Radiation Detection (http://litebird.jp/) LiteBIRD is a next generation scientific satellite aiming to measure polarization of Comic Microwave Background (CMB) at unprecedented sensitivity. Mission Requirements: • Measurement of B-mode polarization spectrum of large angular scale ( by three-year observation of all sky. • Measurement of the tensor-to-scaler ratio r, that represents primordial gravitational waves, at precision σr < 0.001 （w/o subtracting the gravitational lensing effect.） 2 →IPMU Mission Goal : Verificaon of inflaon by detecRng B-mode CMB Foregrounds Primordial GW CMB Dawn of the universe Inflation B moderecombination Big Bang The current universe Age 10-38sec? 380 kyr 13.8 Byr 4 American InsRtute of Phisycs. D. Baumman et Al. Kamionkowski If the inflaon happened, it should make gravitaonal ripples in space. 5 CMB polarizaon @ recombinaon When space became transparent to radiaon, Hot Thomson scaering gives polarizaon to freely travelling photons according to how surroundings are HOT and COLD. Cold Simple Thomson Surrounded by If temperature scaering of electron same temperature is biased… 6 Tilted for 45 degrees W h+ hx Polarizaon a v Polarizaon e y y x x z z z Wave 7 direcon E-mode B-mode 7 Then what makes temperature bias? 2. B-mode 1. E-mode generated only by generated by both temperature Tensor-scalar rao primordial gravitaonal fluctuaon (scalar mode) scalar mode / tensor mode wave (tensor mode) and primordial gravitaonal wave is expected to be very Rny • Proof of the inflaon theory • Dominant, well-measured 0.01~0.001! • Our target !! Should look like this? Measured both by WMAP, Planck (WMAP Komatsu et al.) 8 LiteBIRD Measurement Precision (at r=0.01） B-mode spectrum due to gravitational lensing @95%C.L. ～5µK・arcmin PRL 116, 031302 (2016) LiteBIRD Angular size scale 9 Mission specificaon • Operaon at Lagrange-point 2 • Full-sky scan • OpRmized for large-angle polarizaon structure from primordial B-mode signal • High detector sensiRvity: 3 μK arcmin with margin • Wide frequency band coverage (40-400 GHz, 15 bands) • Launch around 2025-2027 • 3 years operaon １0 Satellite Overview 0.1 rpm Spin Continuously- 30 deg. rotating Half Wave Plates Mission (HWPs) module Mirrors in 4K shell HFT Bus module data transfer to the ground • Satellite consists of two modules : low-temp. mission part and normal-temp bus part. • Rotang HWP modulates incoming signal. • Two complementaly opRcs : LFT and HFT to cover wide freq. bands. • OpRcs are kept under 4K by JT/ST and ADR cryogenics. • SuperconducRng detectors (TES) are arranged on focal planes. １1 Rotang Half Wave Plate HWP • HWP changes direcRon of polarizaon with respect to a fixed axis. • Modulaon of CMB signal by rotang HWP reduces 1/f noise. • Other instrumental systemacs can be greatly reduced by rotang HWP. Sky CMB signal JPS_Sep2016_23aSR-9, Sakurai et al. Rotang HWP • Stacking several layers of rotang HWP makes Modulated CMB signal freq. bandwidth wider. + instrumental noise Expected performance of the polarizaon modulaon efficiency Detector & readout system Data transfer to ground Demodulaon Reconstructed CMB signal １2 HWP Small diameter prototype rotaonal mechanism The sha is coupled to Aperture (a half-wave plate diameter) a motor mounted MagneRcally outside of the cryostat Φ50mm Incident coupled drive and via linear/rotaonal Operaon temperature <10 K light rotor gears Rotaonal frequency about 1 Hz feed-through. OpRcal encoder and chopper Cryogenic 50mm actuators to hold a rotor Broadband AR coang Base material (ns) １3 OpRcal System • Beam size：< 1 deg. at all the • Aperture Size: 40cm observing band • Covered by 4K shell • FOV: 10 x 20 degs. • Cold Baffle and Mirrors Low-Frequency Telescope (LFT) Crossed-dragone compact structure High-Frequency Telescope (HFT) refracRve telescope Sugai et al. (2016) １4 Focal Plane Detectors Lenslets TES behavior hp://web.mit.edu/figueroagroup/ucal/ucal_tes/ • Focal planes consist of arrays of detectors • Each detector array covers certain freq. band Sinus antenna • Behind lenslet antenna and bolometers are arranged • Bolometers (TransiRon Edge Sensors) are cooled to Bolometers ~100mK to detect signals (TES) • Signal readout from Bolometer by SQUID １5 Cryogenic system (Opcs inside) • Cryogenic system consists of JT/ST and ADR coolers. • Covering opcs in 4K shell is important to reduce JT and ST coolers ADR cryocooler thermal noise. １6 All Sky Scan Strategy One precession One-year hitmap • Precession + spin angle < 95 deg. for full anR-sun direcRon scan • Satellite scans all sky at L2 combining “precession” and “spin” moRon １7 Foreground removal Synchrotron emission Dust emission • Polarized signals generated by - Synchrotron radiaon of electron in B field (appears Low Frequency) - Thermal dust radiaon (appears in high frequency) • MulR-band measurement allows to remove those foregrounds from the CMB signal １8 Foreground removal (cont’d) CMB target channel • Measure foreground spectra in many frequency bands to make “FG template” in CMB channel to remove them • LiteBIRD has ~20 bands measurement capability to precisely determine foreground shape in the target CMB channel • Very important to keep required sensiRvity of σr 19 Systemac uncertainRes • SystemsRcs is a major driver to achieve σr <0.001. • It’s complicated ! – 1/f noise – Polarizaon effect by opRcal instruments – Beam effect – And more… 20 Systemac uncertainRes (Some major sources) • 1/f noise It can be reduced by HWP, • DifferenRal beam effect However sRll gives non-trivial effect Assume a pair of pol. detector X, Y PoinRng Low-frequency Y 1/f noise X width elipRcity A&A 510, A57 (2010) • Those make leakage to T, E mode → B mode, causing systemacs • EsRmaon and reducRon of systemacs are 21 22 Project in Rme domain aer launch 23 Summary & Plan • DetecRng B-mode CMB is a challenging mission • Observaon from space by LiteBIRD satellite provides ulRmate environment for the CMB polarizaon measurement • Many challenging technologies – Half-wave plates, superconducRng detectors, etc… • Very excing physics – top-down energy scale search from extremely high energy proving inflaon theory ! 24 .