EBEX: a balloon-borne CMB polarization experiment

Abstract

EBEX is a NASA-funded balloon-borne experiment designed to measure the polarization of the cosmic microwave background (CMB). Observations will be made using 1432 transition edge sensor (TES) bolometric detectors read out with frequency multiplexed SQuIDs. EBEX will observe in three frequency bands centered at 150, 250, and 410 GHz, with 768, 384, and 280 detectors in each band, respectively. This broad frequency coverage is designed to provide valuable information about polarized foreground signals from dust. The polarized sky signals will be modulated with an achromatic half wave plate (AHWP) rotating on a superconducting magnetic bearing (SMB) and analyzed with a fixed wire grid polarizer. EBEX will observe a patch covering ∼1% of the sky with 8' resolution, allowing for observation of the angular power spectrum from = 20 to 1000. This will allow EBEX to search for both the primordial B-mode signal predicted by inflation and the anticipated lensing B-mode signal. Calculations to predict EBEX constraints on r using expected noise levels show that, for a likelihood centered around zero and with negligible foregrounds, 99% of the area falls below r = 0.035. This value increases by a factor of 1.6 after a process of foreground subtraction. This estimate does not include systematic uncertainties. An engineering flight was launched in June, 2009, from Ft. Sumner, NM, and the long duration science flight in Antarctica is planned for 2011. These proceedings describe the EBEX instrument and the North American engineering flight.

Inflation and String Theory

“…Let us be very precise about the notion of probability that is relevant here. The intent is to begin with a compactification of fixed topology -for example, a Calabi-Yau with specified Hodge numbers -and consider all consistent choices of quantized flux F. For each choice F , one imagines finding all the critical points {p (F ) i } of V F in the moduli space M (rather than in its compactification M), and assembling the ensemble C of all critical points, 140) for any choice of flux. Equation counting suggests that for a generic choice of flux, there will be at least one critical point, so we expect 41…”

“…There are many experiments looking for B-modes on degree scales, including KeckArray [139], EBEX [140], SPIDER [141], ABS [142], and CLASS [143]); and on arcminute scales, including POLARBEAR [144], SPTpol [145], and ACTpol [146]). Finally, given the size of the signal seen by the BICEP2 collaboration, the Planck satellite has a chance to see the reionization peak in the B-mode spectrum at low .…”

Features and new physical scales in primordial observables: Theory and observation

“…An all-sky cosmic variance-limited measurement to much smaller scales is feasible with current technology and several experimental designs have been proposed [330,332,333]. Although none of the former have been selected for funding to date, ground based and sub-orbital CMB polarisation measurements (which either by themselves [334] or taken in combination [335][336][337][338][339][340][341][342][343][344][345][346][347][348], promise almost full sky coverage) remain one of the most promising future avenues for the detection of features, especially on the largest scales.…”

BFORE: The B-mode Foreground Experiment

“…1). No other large-area higher-sensitivity observations are underway or planned in this wavelength range, with this resolution, and with a survey optimized to complement ground-based CMB observatories [9,10,11]. Ground-based observations are underway or planned at 220 GHz, where the dust is several times brighter than at 150 GHz and can be used as a foreground monitor, including by the Keck Array [12], Advanced ACTPol [13], Simons Array [14], and SPT-3G [15] projects (Fig.…”