- CMB-Pol
- 7/1: CMB Polarization Conference
-
- David Bowman: Theory Overview
- Joanna Dunkley: Galactic Foregrounds
- Steve Meyer: Summar of Mission Concept Study Reports for CMBPol
- Gary Hinshaw: Polarization Systematics in WMAP
- Colin Bischoff: CAPMAP
- Clement L. Pryke: Systematics in QUaD
- Cynth Chiang: BICEP1 data
- Andrew E. Lange: PLANK hardware and status
- Akito Kusaka: QUIET
- Amber Miller: EBEX
- William Jones: SPIDER
- Al Kogut: PIPER
- Huan T Tran: POLARBEAR
- 7/2
-
- John Kovak: BICEP
- Joseph W. Fowler: ABS
- Nils W. Halverson: SPT-Pol
- Michael D. Niemack: ACT-Pol
- Walter K. Gear: Clover
- Ricardo T. Genova-Santos: QUIJOTE
- Timothy J. Pearson: C-BASS
- Aurelien A. Fraisse: Improving Galactic Foreground Models through Dust Studies
- Pannel Discussion
- Peter Timbie: Bolometric interferometry
- Kendrick Smith: de-lensing
- Chao-Lin Kuo: Prospects for lensing measurements from the ground
- Michael Mortonson: Reionization with future CMB science
- 7/3
CMB-Pol
website: http://cmbpol.uchicago.edu/workshops/path2009/index.php
7/1: CMB Polarization Conference
David Bowman: Theory Overview
Requirements for Inflation
1) accelerated expansion: d2a/dt2 > 0
2) Negative pressure: w < -1/3
3) shrinking comoving horizon
Flat scalar potential:
epsilon = Mp^2/2(V'/V)^2
Quantum fluctuations lead to local time delay in the end of inflation > density fluctuations after reheating.
Scale dependence is parametrized by
\Delta_s^2 = A_s k^{n_s-1}
Obesevations:
Flatness
Scalar Fluctuations
- percent deviations from n_s = 1
- Gaussian, Adiabatic
- Correlations of Superhorizon Fluctuations
Tensor Fluctuations:
Gravitational waves
appears as a massless field during inflation
\Delta_t^2 = 8/mp^2(H/2pi)^2
r \equiv (\Delta_t^2)/(\Delta_s^2)
Prediction for tensors is the same for all models!
Current upper limit: r < 0.22
Superhorizon B-modes?
B-modes as a probe of high energy physics:
E_inf = 10^16 (r/0.01)^1/4 GeV
the Lythe Bound
if r>0.01, means that phi moved over a distance that was larger than a plank distance.
In an effective field theory with Cutoff Lamda < Mp, expect structure over lengths of order plank scale.
Effective Field Theory:
UV completion (string theory)
low-energy EFT
Cutoff scale has to be set below the lightest particle that we are ignoring.
- If we new the complete theory, we could integrate out the heavy fields, leaving an effective potential in terms of only the inflaton.
\Delta V = O(delta)/M^{delta-4}
- If we do NOT know the theory, we add up all corrections consistent with symmetries.
UV sensitivity of inflation is especially strong in any model with observable gravity waves.
- we generically don't expect a smooth potential over a super-Planckian range
Shift symmetry in UV:
phi -> phi + const
This would allow us to get rid of this sum of corrections.
Why should this be valid?
Seeing B-modes would show that the inflaton field respected a shift symmetry up to the Planck scale.
Axions have this property.
Large-field v.s. Small-field
This means, does the phi field move over a large or small distance during inflation.
Small Field
Patch Problem
- at the start of inflation, the field has to be homogeneous over a distance that is a few times the horizon scale at that time.
- This problem is more severe for small-field (low-r) models
Overshoot problem
- field crosses the flat part of the potential too fast.
Fine-Tuned Potentials
- need to go from epsilon << 1 to epsilon ~ 1 very quickly.
- requires a very steep potential cliff after the flat part.
Large Field
Potentials are "Simple"
Attractor Solutions
Improved Initial Conditions
Joanna Dunkley: Galactic Foregrounds
Two components get polarized from Galactic magnetic field:
1) Synchrotron emission: electrons spiral in B-field
The signal is larger than even the EE signal.
Synchrotron index: beta ~ -3
Should expect some variation of syncotron index with frquency and space
Synchotron emission seems vairly pervasive, even above galactic plane
2) Thermal dust emission
A non-spherical grain of dust will emit thermal radiation non-isotropically
Observations:
- FDS dust intensity (94 GHz) -> dust is low off Galactic plane
- expect dust to be polarized at ~1-10%
Removing Foregrounds:
1) Template Cleaning (WMAP)
- Construct a synchrotron and dust template, and subtract them
2) Parametric cleaning
- Try to parametrize contaminates in each pixel, and remove them
- Uses astrophysical inputs to give values to these parameters.
3) Blind Cleaning
- Does not use astrophysical inputs.
Frequency Allocation
- Want to include the foreground min
- Want at least 5 channels: 3 per foreground, 1 for CMB
- Choose frequency to minimize marginalized errors with respect to parametric fit
Galactic Science Goals:
- Magnetic field: origin of field, turbulence
- Dust: alignment efficiency with density and temp, dust composition
- Cosmic Rays: CMB haze, DM annihilation?
Steve Meyer: Summar of Mission Concept Study Reports for CMBPol
2003: Beyond Einstein
2005: Weiss Report: yes, we can in principle reach B-mode detection
2007: PPPDT: NASA committee, defining what will happen in the next decade
2008: CMBpol AMCS: CMBpol mission study,
2010: Decadal Survey
Gary Hinshaw: Polarization Systematics in WMAP
WMAP optics
Back-to-back Gregorian telescope
Radiometers. The two orientations of polarization go through different, parallel paths of electronics.
radiometers measure:
d1 = Delta T + Delta P
d2 = Delta T - Delta P
WMAP baseline processing:
- baseline due to fixed instrument asymmetries and 1/f noise
- long time scales, baseline parameters are fitted and removed
baseline covariance effects polarization at low l
Colin Bischoff: CAPMAP
40/90 GHz
Ring Scan pattern
Use a 5 parameter fit:
M(theta) = A0 + A1 sin(theta) + A2 cos(theta) + A3 sin^2(theta) + A4 cos^2(theta)
Used full-season simulations to estimate systematics
Clement L. Pryke: Systematics in QUaD
100/150 GHz
Sky coverage: 60 deg
Systematics:
Sidelobes
- Ground pickup
- moon pickup
Beam mismatch
Ground Pickup
Used a 12-piece ground shield
snow collected in pannel junctions, caused contamination signal
How do you get rid of this?
- field differencing
- ground template removal
- throws away large-scale structure, below l ~ 200
Moon causes scattering through the foam cone.
- throw out days when the moon was up
Detector Timeconstant devolution
use elnod to measure relative gain calibration
By using an unpolarized source to calibrate, instrumental polarization is not relevant.
Cynth Chiang: BICEP1 data
100/150/(220) GHz
25/ 22 / 2 pixels
Observation: fixed el, boresight; Az scans
Instrument Characterization:
bolometer transfer functions
- use microwave source
- square wave bias
Relative gains
- elnods, 1.5 deg in motion
- removes common mode atmosphere
Absolute gains and detector pointing
- cross-correlate BICEP with WMAP
- cross-correlate temperature maps of BICEP data to get detector pointing
Cross-polar leakage and plzn orientation angle
- rotating polarized sources: dielectric sheet, wire grid
Beam shapes
- map far-field sources
Systematics
two potential problems:
- realitve gain uncertainty
- differential pointing.
Constraints on r from BB
assume fixed LCDM parameters
calculate upper limit on r: integrate Maximum Likelyhood curve up to 95%
Andrew E. Lange: PLANK hardware and status
Has all-sky coverage
= > good understanding of polarized foregrounds
Science
- better TT power spectrum than WMAP
- test n_s
- accell at high l
- neutrino species
- very good EE spectrum for l ~ 40 -> 1200
- first all-sky survey at these frequencies since IRAS
- non gaussianity
Scan strategy is not optimal for polarimitry.
Planck will NOT detect cosmological B-modes
Planck will:
- measure a high-precision measurement of n_x
- high sensitivity to non-gaussianity
Akito Kusaka: QUIET
"Detector on a chip"
Has been observing since 11/08
Just finished Q-band
Now about to start W-band
scan at 2 deg /sec on the sky
W-band
90 pixels, 84 polarization pixels
Array sensitivity: 60 uk/sqrt(s)
Calibration
Gain stability
- Noise source, every 1.5 hours
- tau A, once per 2 days
- Moon observation (Rel. gain, angles)
- elnod (gain, stability)
- Jupiter, once every 7 days.
Systematic Errors:
Fake signal sources
- instrumental I->Q/U: due to imperfection of OMT
- Gain fluctuations
- Noise misestimate
E-B mixing
Use full simulations for parameter estimation.
Amber Miller: EBEX
Balloon experiment
150/250/410 GHz
80, 50, 80 detectors
TES detectors built at Berkeley
rotates on a superconducting magnetic bearing
Read out using squid arrays (NIST)
Digital Frequency Domain Multiplexing (McGill)
Scan: constant Elevation
Calibration:
Absolute Calibration -> WMAP temperature maps
Main Beam adn near sidelobes: Jupiter scan.
Polarization Modulation Efficiency: blackbody source with wire-grid polarizer
Systematic Errors:
- Independent measurements of Q, U, T with each detector on each pixel (no differencing between diff detectors)
- Instrumental polarization from elements on teh detector side of the HWP are not modulated = > don't affect sky signals
First flight in New Mexico
William Jones: SPIDER
96 / 145 / 220 GHz
Systematics:
- receiver 1/f knee
- pointing jitter
- absolute pol angle offset
- relative pol angle offset
- knowledge of beam centroids
- optical Ghosting: stray refracting between optical elements
- calibration drift in phase: e.g. from altitude variation
- calibration drift out of phase: different between detectors
Science goals:
Test Flight
- E-mode complementary to Planck
- r < 0.15
- Galactic dust polarization
Long flight
- r < 0.05
- T/S limit extremely complementary to Planck
Tau -> optical depth to reionization
Limits on B-modes similar for McMurdo and Alice Springs flight
Al Kogut: PIPER
Looking for reionization bump: low l
5120 detectors
200, 270, 350, 600 GHz
4 flights in 2013 and 2014
Detector Array:
TES bolometer at 0.100 K
Waveplate technology
Uses the fact that V is zero on the sky. What is V?
The entire experiment lives in a 5000 L liquid He dour
- simplifies beam-spillover effects
Foregrounds: only worry about dust.
Scan Pattern: slow spin gondola
Detects intensity, circular polarization
Huan T Tran: POLARBEAR
Monochromatic - switch focal planes for different frequencies
90/150/220 GHz
Monolithic central primary mirror
7 wafers, 6xx detectors
Both continuous and stepped rotation
Use a large Ground-shield
Systematics: focus on Beam Distortions
Scan Regions match QUIET
7/2
John Kovak: BICEP
Could have used a Temperature template map. What is this?
measured r < 0.7
Results are a factor of 4 higher than projected. Why?
What is OK:
- Time on target > 3000 hrs
- foreground removal
- 1/f noise
- E/B separation
- Chance fluctuation
Small factors:
- (numerous)
BICEP2 and KECK
~2500 detectors
Joseph W. Fowler: ABS
Small feed horns - hand made in the Princeton machine shop
Array is not close packed - requires scan strategy to get rid of effects
Spinning HWP?
only at 1 frequency.
Nils W. Halverson: SPT-Pol
10m off-axis gregorian
1 arc-minute resolution
600 sq degrees of observation
GroundShield: not sure if it is going to work yet.
Digital frequency multiplexed readout: same as IBEX
Use corrigated horn feeds
150GHz -> 637 pixels, NIST
90 GHz -> 198 pixels, Argonne
OMT - Ortho Mode Transducer
Calibration
- Absolute gains: WMAP & Planck
- gain stability: chopped IR source
- absolute relative gains: elnods
- unpolarized beam response: planet observations
- Polarization orientation angle
- Polarized beam response: mirror on a pole
Michael D. Niemack: ACT-Pol
145, 220, 280 GHz
In Chile
Start 2012
Science Goals:
- High l power spectra
- Lensing signal
3 independent optics paths
1 deg Field of View per array
640 polarimeters
Detectors same as SPT and ABS
Detectors are small; 5mm across
Why is sapphire used? here, sapphire thermal isolation
First light; 2012
Walter K. Gear: Clover
target r ~ 0.03
Design:
- 97 / 150 / 225 GHz
- No lenses
- Pulse tube cooler
- large mirrors on small central bearing
Clover is officially cancelled
Ricardo T. Genova-Santos: QUIJOTE
Low frequencies (11-40 GHz)
Algular resolution: 1 deg
Operates in the Canary islands
Science:
- Constrain B-modes
- measure foregrounds: synchrotron signal dominates at low freq
Scanning strategy
- spins at a fixed elevation with constant velocity in azimuth. Earth rotation provides daily sky coverage
- need to subtract radio sources
Timothy J. Pearson: C-BASS
C-band All Sky Survey
5 GHz
Two telescopes, one in CA and one in South Africa
Completion in 2011
Science:
- survey difuse Galactic emission; dominated by synchrotron radiation but high enough to be uncorrupted by Faraday rotation
- Enable accurate subtraction of foregroud contaminating signals from high freq CMB
- Major source of foregrounds for studying inter-stellar radiation
Goal: Polarized synchroton template
will need to subtract off point sources individually.
Systematics:
- 1/f -> rapid scanning in AZ
- highly redundant coverage
- sidelobes: optical layout and feed-horn design
- Radio Frequency Interference
Scanning Strategy:
- 6 deg per sec
Comissioning NOW
Data release in 2011, 2012
Aurelien A. Fraisse: Improving Galactic Foreground Models through Dust Studies
Building Dust Models
- Composition of dust grains: mixture of carbonaceous and silicate grains
- should reproduce: MW extinction, starlight plzn, most extreme polarizations
Pannel Discussion
"What i practice will be the biggest issues for the upcoming round of ground/alloon based experiments?"
Andrew Lang
The issue is not technical; it is sociological and financial.
This is hard; no longer a low hanging fruit.
We need to put money and time into data analysis, not just hardware.
Gary Hinshaw
Nothing has been limited by systematics yet.
Challenge: sensitivity.
Large scales: foregrounds are the largest problem
Small Scales:
We should start seeing systematics and foregrounds.
John Roul
Need to organize group to focus on analysis.
Scaling to more complicated experiments and more data
Bruce Winstein
1) Null Tests (Jacknife tests).
2) South Pole; Huge ifrastructure, good cooperation. Bicep2/Keck, and SPT
3) Atacama; No cooperation.
4) Need more financial resources.
5) Use multiple detector technologies
??
We have multiple good types of detector technologies
Characterization and Calibration need resources
Financial challenge: how to have the capability to maintain the current program, and improve it.
Atacoma Cooperation
NSF is interested.
Sensitivity
We need high sensitivity because we are going to have to throw out a bunch of data that we can't trim down, regardless.
Were we are stuck right now is making arrays: stable, characterized, calibrated
The existing round is using technologies that have been developing over 10 years. The next round is using new technology that is not necessarily well understood.
Roul: We are using both new detector technology, and new focal plane technology (wave plate)
Analysis
Lang: We need to spend more money on analysis
Pryke: Collaboration on data analysis?
??: Need more coordination between data analysis and calibration/characterization.
Career prospects for "Data Analysists"
Peter Timbie: Bolometric interferometry
Beam Combination for Large N
1) Pairwise: signals are split and combined pairwise
- N(N-1)/2 pairs
- multiplying correlator
- doesn't work (not sure why)
2) Fizeau: signals from all antennas appear at all detectors
- Signal enters feed horns
- OMT's
- phase modulators
- beam combiner
- detectors
Kendrick Smith: de-lensing
E-mode:
B-mode:
d_a(n): distance between where a light source is and where it appears to be
CMB lense reconstruction
Lense breaks translation invariance
Two-point correlation function is non-zero for different fourier modes
Sum over all modes in the CMB whos fourier modes are different
From T(n), can calculate the power spectrum, and a 4-point estimator for the CMB
First detection from WMAP
1. Lens reconstruction estimators
Quadratic estimator is also useful for
- Reionization bubbles generate B-modes, via scattering (large scales) and screening (small scales)
2.
WMAP six-parameter space: {Omega_b h^2, Omega_m h^2, A_s, tau, n_s, Omega_Lamgea}
First 5 are constrained through tthe shape of the power spectrum
"Angular diameter distance degeneracy"
Lensing breaks this degeneracy.
Neutrino Mass:
Lensing potential is sensitive to the sum of the masses.
Dark Energy:
Lensing would add to the constraint of Omega_Lambda in combination with SNAP
3. Prospects for delensing
Lensing ooks like white nose with amplitude 5.5 uk-arcmin
Forecasts for "r"
This will be very sensitive to what assumptions you make about foregrounds.
Improvement ratio:
"No go" result: cannot de-lens polarization using small-scale temperature.
"No go" result: cannot delense polarization using large-scale structure.
Chao-Lin Kuo: Prospects for lensing measurements from the ground
By simple scaling, want 10,000 detectors to make a statistical measurement of the lensing B-modes with current detector technology.
Proposed experiment: array of crossed Dragone telescopes
Pol-Len
~ 2000 detectors, 5 telescopes
Another possibility: 8,000 detectors on a single telescope
Then we make 10 telescopes with 80,000 detectors.
Trade-offs:
- NO HWP modulators
- No full psi-rotation
- Modulation relies on scanning - QUaD / BICEP style
- For the same (theta, phi), two possible psi angles can serve as a systematic check.
Michael Mortonson: Reionization with future CMB science
Origin of the Reionization bump
- Free electrons from reionizaation rescatter CMB photons
- Local quadrupole generates polarization
- Scattering at low redshifts projects onto large angular scales
WMAP > optical depth tau 0.09
Physical Parameters
1. Optical Depth
2.
3.
Physical models
- Simple model: assume that DM halos of mass M host radiation sources that ionize regions of mass
- Degeneracy between M_min and Cxi
- We will need some other input from theory or observation to break this degeneracy.
We can have confusion between inflationary signals and reionization.
Summary:
- Future data will improve reonization parameters
- can measure 5 params
- need additional information beyond large-scale CMB
- potential confusion between effects of reionization and othe rlarge-scale polarization parameters.
7/3
Jamie Bock: EPIC mission overview
Science Goals:
- Inflationary B-modes
- B-mode cosmic shear spectrum
- E-mode spectrum to cosmic variance to damping tail
- Map galacitc magnetic fields via dust polarization
Scan strategy gives very uniform coverage.
30 / 45 / 70 / 100 / 150 / 220 / 340 / 500 / 850
Detector sensitivity is similar to Plank, but there are a lot more of them!
Space mission gains:
- all sky coverage
- systematic erro rcontrol
- multi-band coverage
- sensitivity
Adrian Lee: EPIC
1. Cold telescope in space -> Extremely high sensitivity focal plane
2. Focal plane technologies being tested now.
Possible Focal plane technologies:
- Scalar horn coupling
ACT-pol, SPT-pol, ABS
Low horn sidelobes
low mass design required -> horns at higher T
- Phased-array antenna coupling
BICEP2, KECK
low mass, mechanically simple
- Antenna Contacting lense coupling
POLAR-BEAR
multichroic
reduce focal plane area by 3x
Multiplexed readout technologies:
- Multiplexed kinetic inductance detectors
- time domain multiplexed TES
- Frequency domain multiplexed TES
Huan T Tran: Optical Design
Warren Holmes: Focal plane cooling
Adiabatic Demagenitization Refrigerator (ADR)
- cooling through magnetization / de-magnetization
Brian Keating: Systematic Errors
Beam effects
- differential FWHM (monopole effect)
- differential beam offset (dipole IP effect)
- differential ellipticity (quadrupole effect)
- differential gain (monopole effect)
Systematics both degrade and bias measurement of parameters
Pannel Discussion: What is the path beyond the current round?
Chao-Lin Kuo
How do you simplify a system, and how do you scale up the number
Al Krugut
What happens if we don't get a bunch of new money?
What is the unused capacity in the system?
Ballooning: American flights
Clem Pryke
There are a lot of experiments right now (8 or so). This is ok for now, as we investigate new technology.
We need fewer, larger collaborations.
As a community we are too modest; we need to advocate for more ambitious experiments.
Jamie Bock
Good momentum right now. Our future challengs are not technical.
Systematic errors, foreground problem.
Medium Term: ready for mid-decadal review
Shaul Heniny
There is certainly space for another round of experiments that will actually push up to 0.01
Need to put up a lot of detectors.
EPIC-IM on the ground.
Fewer, more expensive experiments
Currently, we get ~ $1 million per year.
Proposal: We need to do something about the data that we need to make public anyhow.