adding interferometry for cmbpolcmbpol.uchicago.edu/workshops/technology2008/depot/... · 2008. 9....

27 August 200827 August 2008 CMBPol Technology WorkshopCMBPol Technology Workshop 11

Adding Interferometryfor CMBPol

Peter Timbie University of Wisconsin - Madison

QuickTime™ and aTIFF (Uncompressed) decompressor

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27 August 2008 CMBPol Technology Workshop 2

Imaging and Interferometry

FT

Visibilites V(u,v)

FTCl

l

correlator

Cl

l


OutlineWhy interferometry?ChallengesBeam combination: pairwise vs ‘all-on-one’, multiplying vs addingGuided-wave beam combinerQuasi-optical beam combiner

MBIEPIC Interferometer

Required technologies (bolometric interferometer)horn antenna arraysOMTsphase modulatorsbeam combiner/correlatorfiltersbolometers/readout100 mK cooler

Discussion


CMB Interferometers

HEMT810’, 3’30, 90SZA

ν (GHz) FOV # ant’s receivers

DASI 30 5o 13 HEMTCBI 30 44’ 13 HEMTMINT 150 30’ 4 SIS

VSA 30 7o 14 HEMTBIMA 30 6’ 6 HEMTOVRO 30 4’ 9 HEMTT-W 45 5o 2 SISBAM 90-270 42’ 2 BoloVLA 5, 8, 16 7’ 27 HEMT

Interferometers for the CMB


Why CMB Interferometry? Systematics!• simple optics

- forms beams with corrugated horn arrays

- symmetric beam patterns, low sidelobes, no mirrors

• no off-axis aberrations

• Stokes U measured by correlation of Ex and Ey on a single detector(no differencing of detectors)

• differences sky signals without scanning

• measures power spectrum directly

• measures both Temp and Polarization anisotropy

• coherent (HEMTs) or incoherent (bolometers) systems possible

• angular resolution ~ 2X better than imager of equivalent diameter

• CMB polarization first detected with interferometer (DASI)

• simple scan strategy - rotate about optical axis, move on to new pixel


Interferometer beam systematics: example

j

n1 n2

uij

VijU = dn1∫ dn2Gix (n1 )G jy (n2 ) Eix (n1 )E jy (n2 )

i

= dn∫ Gix (n)G jy (n)U(n)ei2πuij ⋅n

U(n1 )e2πiuij ⋅n1 δ(n1 − n2 )

So - beam mismatch, distortion, etc. do not couple T intoStokes U visibility measurement.

y

x

X


Challenges for Interferometry

• beam combiner - scalable, low loss

• “fringe smearing” from wide bandwidths

• simulations


Beam Combination1. Pairwise (Michelson): signals are split and combined pairwise

• N(N-1)/2 pairs (78 for N = 13, 4950 for N =100)

• multiplying correlator (coherent receivers only)a. analog (DASI/CBI)b. digital (most radio interferometers)

see Coherent Detectors, C. Lawrence et al.- power?- bandwidth?

• adding correlator with bolometers: M. Hattori, Tohoku University

2. Fizeau (Butler): signals from all antennas appear at all detectors

• Fizeau approach has lower noise in background-limited case, in low n limit(Zmuidzinas 2003)

• Hamilton et al. (astro-ph/0807.0438) compares to imaging

• Guided-wave adding interferometer (Butler combiner, Rotman lens)

• Quasioptical adding interferometer using a telescope (MBI)


Ryle’s Adding Interferometer (1952)

“visibility”

10

Adding interferometer for N > 2

OMTs

1||1 EE +⊥ 2||2 EE +⊥

N

EEEE

N

EEEE NNNN∗

⊥⊥⊥⊥ +++×

+++ )...()...( ||1||1||1||1

=(E⊥1

2 + ...E⊥N2 ) + (E⊥1E||1 + ...E⊥N E||N ) + (E⊥1E||2 + ...E⊥1E||N ) + (E⊥1E⊥2 + ...E||E||N )

N

total power single-hornauto-correlation

Stokes Uvisibilities

N horns

2N phase modulators

beam combiner

detectors

E⊥N + E||N

Stokes Ivisibilities

⊥// ⊥// ⊥//….

….


I. Guided-wave beam combiner

• Waveguides or planar transmission line• Butler combiners (N inputs and N outputs)• Rotman lens (N inputs, > N outputs)• Losses may restrict to coherent receivers (with gain)


φ

φ

φ

φ

T Q U

Geometricdelays

φ

φ

φ

φ

φφRotman Lens stack

Phaseswitches

Dio

de D

etec

tor a

rray

Anti-reflection resistive layer

2D horn array

Orthogonal cross stack

OMTs

Idealised Rotman interferometer scheme showing the input TQU maps and the paths through to the detectors. The signal from each sky element reaches each horn with different geometric delays. OMTs split the signals into different hands of polarization which are then phase switched independently before being input to the first Rotman stack. The column followed by the row stack performs a Fourier transform and the Fourier transform of these detected outputs gives the visibility information.

Rotman Lens interferometer scheme(see poster by R.A. Watson & L. Piccirillo)

Dio

de d

etec

tor a

rray

(HEMTs)


A B C D

Antenna ports

Beam ports

Dummy ports

Dum

my p

orts

Dummy ports

Dummy ports

-7 /8π

-7 /8π

-7 /16π-7 /16π

-5 /16π-5 /16π-3 /16π

-3 /16π- /16π- /16ππ/16

π/163 /16π

3 /16π

5 /16π5 /16π

7 /16π7 /16π -5 /8π

-5 /8π-3 /8π

-3 /8π

- /8π

- /8π

π/8

π/8

3π/8

3π/8

5π/8

5π/8

7 /8π

7 /8π

The Rotman Lens: Alternative to Butler combiner(Watson & Piccirillo)

HFSS simulation of a Rotman Lens. The relative phase on the outputs is given in different colours for each antenna port.

Rotman lens (Rotman and Turner 1963) is a planar transmission line implementation of the quasi-optical combiner.

It consists of a set of beam and antenna ports either side of a specially shaped parallel plate cavity through which the waves propagate.

The design is simple and many inputs and outputs can be easily incorporated, unlike a Butler combiner

It can be implemented cheaply in microstrip and using high dielectric constant substrate (εr>10) can reduce size sqrt(εr) (>3).


II. Adding interferometer with a quasi-optical beam combiner

• Millimeter-wave Bolometric Interferometer (MBI)• EPIC Interferometer


Bolometer Array

Parabolic mirror

Phase Shifters

Feed horn antennasCryostat

45° CW twist rectangular wave guide

45º CCW twist rectangular wave guide

Quasioptical Beam Combiner


The Millimeter-Wave Bolometric Interferometer (MBI)

• Fizeau (optical) beam combiner

• 4 feedhorns (6 baselines)

• 90 GHz (3 mm)

• ~1o angular resolution

• 7o FOV

Antennas

Liquid nitrogen tank

Liquid helium tank

Secondary mirror

3He refrigerator

Primary mirror

Bolometer unit

Phase modulators


Effect of Phase Shifting

Single Baseline

(Two feeds)

Six baselines

(Four feeds)


MBI Assembly

19 spider-web bolos (JPL)

15 cm


MBI Team

Lucio PiccirilloUniversity of Manchester

Evan Bierman, Brian KeatingUC San Diego

Peter Timbie, Amanda Gault Peter Hyland, Siddharth Malu

University of Wisconsin - Madison

Ben WandeltUniversity of Illinois

Creidhe O’Sullivan, Gareth CurranNational University of Ireland - Maynooth

Peter Ade, Carolina CalderonCardiff University

Ted BunnUniversity of Richmond

Greg Tucker, Andrei Korotkov Jaiseung Kim

Brown University


First lightat

Pine Bluff ObservatoryMadison, WIMarch 2008


MBI interference fringes

Tucker et al. SPIE 2008

22

Einstein Polarization Interferometer for Cosmology (EPIC) Mission Concept

Backshort Under Grid (BUG)TES array (NASA/GSFC)

64-element module(1 of 16)

25 cm at λ = 0.3 cm

Interference fringes measured infocal plane by bolometer array

RF phase modulators

Corrugated horns

Fizeau beam combiner

OMTs

23

EPIC LEO Mission Concept

1.75 m dia

90 GHz module(1 of 8) 0.25 m dia

60 GHz

30 GHz

150 GHz

250 GHz

0.9 m


• Measure CMB E and B mode polarization over full sky toforeground limit (T/S ~ 0.01)

Scaled close-packed corrugated horn arrays: 30-300 GHz

~15o FOV, ~ 1o synthesized beams

Total # horns N ~ 1024 (= # modes) x 2 pol’ns

Interferometer: signals cross-correlated

- between horns: N(N-1)/2 visibilities for small scales

- between 2 polarizations for each horn: “correlation polarimetry” for large scales

Lifetime > 1yr from 900 km Earth orbit (COBE)

EPIC LEO Mission Concept

LHe Dewar

Spacecraft Bus

Arrays


EPIC sensitivity calculation

• each array module has N = 64 antennas, 2 polarizations• signal from each antenna spread out over focal plane of

4N = 256 detectors• phase-modulated fringe signal meas’d independently

by each detector• background-limited detectors in focal plane of beam combiner• η = 0.5, 20 % BW• 4N demodulated signals are then added in quadrature

to compute visibility• repeat for each of the 2N(2N-2)/2 visibilities (all baselines)• add in quadrature signals from other arrays at 90 GHz• 1 - year integration over full sky (“Knox” formula)• see J. C. Hamilton et al. (astro-ph/0807.0438)• - comparison with imager, coherent interferometer

- simulation


EPIC Sensitivity


Interferometer “Fringe Smearing”

• 1-D simulation

• diffuse source(CMB) with flatpower spectrum

• horn apertureD ~ 17λ

~7° FWHM beam

QuickTime™ and a decompressor

are needed to see this picture.horn

spacing

D2D4D6D8D 12D 16D


Horn Antenna Arrays

• need close-packed arrays of ~ 8 x 8 antennasfrom 30 GHz to 300 GHz

• total of 1024 horns for EPIC Interferometer

• platelet arrays (see Gundersen and Wollack)

• smooth-walled horns (Yassin et al.)

29

G. Yassin

Easy machining!


Ortho-mode transducers

• separate X/Y linear or R/L circular polarization modes

• input: interface to circular horn output

• output: interface to phase modulator (waveguide or transmission line)

• low-loss (< 0.5 dB)

• low cross-coupling (< - 40 dB?)

• bandwidth ~ 30%

• mass production? 1024 required, bands from 30 GHz - 300 GHz

• see ClOVER design, Giampaolo Pisano et al.


CIOVER OMT

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• G. Pisano et al.IEEE Micr. and Wireless Comp. Lett.17(4) 2007

• electroformed copper

• WR10 waveguide band (75-110 GHz)

• ms’d return loss -22 dB avg. across band

• ms’d isolation -45 dB avg. across band

• 100’s req’d for ClOVER


Phase Modulators• require 2 for each antenna (one per polarization)• input interfaces to OMT output (w’guide or transmission line)• ~ 30% bandwidth• low insertion loss (< 0.5 dB)• low amplitude modulation• step through a phase sequence similar to Walsh function

- co-add signals from redundant baselines (Charlassier et al. ‘08)- # steps minimized by having multiple phase angles

(Hyland, Follin, & Bunn arXiv:0808.2403v1)• for 8 x 8 array

- steps of 360/15 = 24° is optimal- sequence length is 675 steps

• switching speed > 100 Hz• waveguide Ferrite Rotation Modulator (FRM) see B. Keating• planar modulators (MEMs and SIS) see A. Kogut


Ferrite phase shifter performance

Gault, Malu, Bierman, Keating, et al.


Bolometers

• filled arrays required to capture all radiation in focal plane• # pixels ~ 4 X Nhorns for each interferometer module• near photon noise limit for

-optical efficiency of ~ 12% ( ~ 50% / 4)-bandwidth 30%-CMB background loading

• Backshort Under Grid (BUG) arrays for GISMO (λ = 2 mm)- increase 64 pixels → 256 pixels- reduce G- extend to λ = 1 cm- $400K/yr for 3 years

• other candidates?


Adding Interferometer Systems

Complete systems are required to test the conceptMBI-4 ….MBI/BRAIN

Simulations have just become available this year:R.A. Watson & L. Piccirillo (poster)J.-C. Hamilton et al. (2008) ArXiv 0807.0438

37

PSD1 VL-HR PSD2 VL-VRPSD3 HL-VL PSD4 HL-VRPSD5 HL-HRPSD6 HR-VR

Initial simple simulations of Rotman interferometer (Watson & Piccirillo)

The simulation was carried on a 4x4 array shown in figure 4 with a 5o FWHM with a spacing of 20 wavelengths between elements using a HEALpix TQU map generated by synfast using a concordance model.

The signal from each HEALpix pixel is traced through all horns through the Rotman stacks to the detectors where the complex sum is made and its contribution detector power determined

The lower panels show the real and imaginary parts of visibilies recovered by the FFT on the different phase switched detector stacks.

The stronger unpolarized signals (CMB fluctuations) can be seen on PSD channels 2, 5 and 7 with weaker polarized U visibilities at 10% on PSDs 1,3,4 and 6

TQU HEALpix map

Geometry of dual polarization elements

Correlation pairs for each PSD lock-in

38

BRAIN/MBI

First module fordeployment at Dome C,Antarctica

Workshop at APC, Paris, June ‘08 “Bolometric Interferometry for the B-mode Search” Bolometer arrayBolometer array

phase phase shifteshifte

rsrs

hornshorns

backbackhornshorns

30 K

300 mK

30 K

30 K

Sky

70 cm

60 cm

10 cm

10 cm

40 cm

•United States•Brown University•University of Wisconsin, Madison•University of Richmond•UC San Diego•University of Illinois

•United Kingdom•University of Wales, Cardiff•University of Manchester•NUI Maynooth

•France–Astroparticule et Cosmologie (APC), Paris–Centre d’Étude Spatiale de Rayonnements (CESR), Toulouse–Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Orsay–Institut d’Astrophysique Spatiale (IAS), Orsay

•Italy–Università di Milano - Bicocca–Università di Roma - La Sapienza

•United Kingdom–University of Manchester–University of Wales - Cardiff

Bolometric Radiation INterferometer MBI


Adding Interferometer Technology Readiness

Planck & HerschelGISMO

86

focal plane bolometer arrays - NTD Ge- Backshort-Under-Grid TES

BICEP & MBIPAPPA

52/3

phase modulator- ferrite (2 state, <150 GHz)- MEMs/SIS (2 state)

MBITBD

52

beam combinerquasi-optical- guided-wave

ASTRO-E29Sub-K Cooler: Single-shot ADRSpitzer, ISO, Herschel, COBE9LHe Cryostat

WMAPClOVER

94/5

OMT (< 100 GHz)ClOVER OMT (150 GHz?)

WMAP & COBEQUIETTBD

953

corrugated horn antennas (singles)platelet arrayssmooth-wall horn arrays

HeritageTRLTechnology


SummaryWhy interferometry?ChallengesBeam combination: pairwise vs ‘all-on-one’Guided-wave beam combinerQuasi-optical beam combiner

MBIEPIC Interferometer

Required technologies (bolometric interferometer)horn antenna arraysOMTsphase modulatorsbeam combiner/correlatorfiltersbolometers/readout100 mK cooler

adding interferometry for cmbpolcmbpol.uchicago.edu/workshops/technology2008/depot/... · 2008. 9....

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