1. B Polarization Measurement of the CMB
19 mai 2006
B Polarization Measurement
of the CMB
at the Concordia Station (Dôme C)
Yannick Giraud-Héraud
(APC - Paris)
August 31, 2006
2nd Sino-French workshop

2. 2nd Sino-French workshop
OUTLINE
reminder of CMB polarization parameters
challenges for CMB polarization measurements
observationnal status and forthcoming observations
BRAIN: an interferometer at Dôme C (Antartica) for
measuring B mode polarization of the CMB
August 31, 2006
2nd Sino-French workshop

3. Stokes Parameters  I = <|Ex|2> + <|Ey|2>
WMAP3 23 GHz
Ex(t)
Ey(t) x’ y’ 
Total intensity:
Linear polarization:
I = <|Ex|2> + <|Ey|2>
Q = <|Ex|2> - <|Ey|2>
U = <|Ex’ |2> - <|Ey’ |2>
August 31, 2006
2nd Sino-French workshop

4. 2nd Sino-French workshop
The E/B Decomposition
Can decompose Q & U into:
E-modes (even-parity):
(or grad)
B-modes (odd-parity):
(or curl)
E-modes produced by all quadrupole sources (velocity gradients and gravitational waves)
B-modes produced by gravitational waves and lensing of E-modes
Wayne Hu
Pure E
Pure B
August 31, 2006
2nd Sino-French workshop

5. 2nd Sino-French workshop
Uses of CMB Polarization
Tighter constraints on cosmological parameters
Gravity waves from inflation
nature of gravity
test of inflation
energy scale
Planck-era physics?
Lensing reconstruction
constraints on Dark Energy
neutrino mass measurement
August 31, 2006
2nd Sino-French workshop

6. CMB observables as probe for inflation
- r : ratio between the amplitude of tensor/scalar power spectrum
WMAP3 alone: r<0.55 (95% C.L.)
(WGW< )
(based on temperature power spectrum)
- nS, nT spectral indices of scalar and tensor power spectrum
WMAP3 alone: ns= (no running contribution)
power spectrum of type B polarized anisotropies
access to primordial gravitational waves
August 31, 2006
2nd Sino-French workshop

7. CMB polarization measurements?
What can we get from
CMB polarization measurements?
C. Rosset
August 31, 2006
2nd Sino-French workshop

8. CMB polarization measurements?
What can we get from
CMB polarization measurements?
Weak lensing
E mode  B mode
énergie noire
C. Rosset
August 31, 2006
2nd Sino-French workshop

9. Polarization has been measured
DASI, CBI, BOOMERanG and CAPMAP
have all published polarization detections.
WMAP
DASI
Lens
IGW
August 31, 2006
2nd Sino-French workshop

10. Planck, for a 14 months survey:
Full sky survey
CMB anisotropies
Temperature and polarization
Resolution: 5’
Sensitivity: ∆T/T =
Foregrounds
15 times more sensitive than WMAP
Planck will be the ultimate experiment
for T up to l  2000,
for E up to l  1000 …
… but will be able to detect B mode only if r is closed to its actual upper limit.
Planck, for a 14 months survey:
~100µK RMS
Mode E
~4µK RMS
Mode B
~300nK RMS
(Hu et al. 2002)
r=0.7
August 31, 2006
2nd Sino-French workshop

11. 2nd Sino-French workshop
Planck Polarization
(Planck Blue Book)
E spectra
B spectra
August 31, 2006
2nd Sino-French workshop

12. Which objectives for the CMB physics after Planck
high-angular resolution  Sunyaev-Zel’dovich effect
increase the number of detectors to measure the
polarized anisotropies polarisées with an optimization of the
optical scheme to fight the systematic effects
Probe of the inflation epoch and of the Large Scale Structures
August 31, 2006
2nd Sino-French workshop

13. 2nd Sino-French workshop
Sensitivity of forthcoming observations E1 E3 E2
E1 : 1000 detectors ; 1 year ; 6’ ; 4 % of the sky
E2 : 1000 detectors ; 1 year ; 1’ ; 0,4 % of the sky
E3 : 1000 detectors ; 1 year ; 30’ ; 100 % of the sky
August 31, 2006
2nd Sino-French workshop
(Task Force on Cosmic Microwave Background Research - July 2005)

14. 2nd Sino-French workshop
Long term effort
QUaD, BICEP ( )
~2005
BICEP
QUaD
CLOVER, EBEX, POLARBEAR, BRAIN ( ) ~
ClOVER
EBEX
PolarBear
QUIET
SAMPAN, CMBPOL
(> 2018)
Gravitational waves
>2015
CMBpol (NASA
& ESA)
SAMPAN (CNES)
(Ken Ganga 2004)
(Kaplinghat et al. 2003)
August 31, 2006
2nd Sino-French workshop

15. Concordia Station at Dôme C
French-Italian
Concordia Station at Dôme C
August 31, 2006
2nd Sino-French workshop

16. Concordia Station at Dôme C
3 traverses (12-15 days) from Dumont d’Urville to
Dôme C (1100 km) every Summer (3x150 tonnes)
4 hours flight from Terra Nova Bay with Twin Otter
first Winter season from February 2006 to
September 2006 with 13 overwinterers
Excellent atmospheric transmission all over the year
winter average
pwv = 250 m
Dome A
Data South Pole
Zhongshang
No measurement during the Winter Season in mm wavelenghts: site testing needed
August 31, 2006
2nd Sino-French workshop
Dumont d’Urville

17. 2nd Sino-French workshop
Optical Depth for
3 sites :
Chajnantor (ALMA)
Pôle Sud
Mauna Kea
Transmission = e-t
(e-1/e-3 = 7,4)
1 year Dôme C =
2 years South Pole =
5 years Atacama Plateau
Peterson et al
August 31, 2006
2nd Sino-French workshop

18. Polarization of the atmosphere
Zeeman Effect on the oxygene lines
Circular Polarization
Estimation: 100µK CMB
(Modes B: <300nK RMS)
August 31, 2006
2nd Sino-French workshop

19. 2nd Sino-French workshop
Sky Coverage
Projection of the foregrounds at
150 GHz (centered on the South Pole)
The 2 circles are at declinations -40° et -80° (Dôme C at -74°30’)
The upper region between the 2 circles is a potential zone for observation
Ability to observe always the same part of
the sky
Scanning direction changes with time
August 31, 2006
2nd Sino-French workshop

20. BRAIN The instrument at Concordia (January 2006)
Collaboration France-Italy-UK
(Rome, Milan, Cardiff, APC, CSNSM,
CESR, IAS, LISIF)
August 31, 2006
2nd Sino-French workshop

21. BRAIN: a prototype of bolometric interferometer
Why an interferometer ?
sensitivity similar to a photometer
direct measurement of the Stokes parameters (e.g. Cl)
differential measurement
 reduction of atmospheric noise
simplified optical set-up (no mirror)
 reduction of systematic effects (atmosphere, far side lobes, …)
Horns
Ortho-Mode Transducers
Phase shifters
Beam combiners
Bolometers
August 31, 2006
2nd Sino-French workshop

22. 2nd Sino-French workshop
BRAIN : 2 STEPS
1) Pathfinder
Objectives:
automatic monitoring of the cryogenic system (300 mK) during the Winter season
achieve the control of the experiment from Europe which implies satellite telemetry (INMARSAT, IRIDIUM, …)
measurement of the atmospheric noise during the Winter at 150 GHz (intensity and polarization)
2) Validation of the interferometry approach in the millimetric domain using bolometers
at room temperature in the laboratory
at Dôme C with 6 baselines
August 31, 2006
2nd Sino-French workshop

23. 2nd Sino-French workshop
August 31, 2006
2nd Sino-French workshop
(January 2006)

24. BRAIN 2: looking for primordial B modes
Dôme C (Antartica)
3 telescopes at 90, 150 and 220 GHz
3 interferometers of 16x16 horns with bolometric read-out
50 < l < 150
Starting in 2009?
R=0.1
R=0.01
R=0.001
(Clément Cressiot, 2006)
August 31, 2006
2nd Sino-French workshop

25. 2nd Sino-French workshop
August 31, 2006
2nd Sino-French workshop

26. BOOMERanG and CBI Measurements
Neither BOOMERanG nor CBI
have detected any BB at the level
of the EE polarization signals.
This limits the foregrounds in their
regions.
Montroy, et al.
August 31, 2006
2nd Sino-French workshop

27. Optique froide (Cardiff)
Cornets Archeops:
Prototype:
August 31, 2006
2nd Sino-French workshop

28. Optique froide (Cardiff)
Cornets Archeops:
Prototype:
August 31, 2006
2nd Sino-French workshop

29. 2nd Sino-French workshop
Déphaseur à 4K
Responsabilité APC-LISIF
Déphaseur diélectrique
Actionneur piézoélectrique
Statut:
Simulations réalisées
Design figée
En réalisation au BE
Tests en septembre 2005
August 31, 2006
2nd Sino-French workshop

30. 2nd Sino-French workshop
Sensitivity comparison between total power array of bolometers and bolometric interferometer
Total # of photons:
A: area main dish
: solid angle of single pixel
Total # of photons:
A’: area input horn
’: solid angle of input horn
sensitivity is equal when
August 31, 2006
2nd Sino-French workshop