Global - PowerPoint Presentation

Slide1

Global EoR Experoments

Ron

Ekers

, CSIRO

CAASTRO Global

EoR

Workshop

Uluru, 17 July 2013Slide2

SummaryStrategy for technically difficult experiments

Either masochists or people who don’t know any better!

NB the Crick and Watson story on DNA structure

Global HI EoR v imaging HI EoRStatistical v direct detectionCORE  ZEBRA  SARASOther global HI experimentsEDGES, BIGHORNS, COREII, DARE, Pulse calibrationEpoch of (re)combination

July 2013

2Slide3

Global HI EoR prediction

Pritchard et al, Nature

468

, 772 (2010)

Z = 6.3

Peter Shaver

conjecture

(200/65)

2.5

=17Slide4

The 21cm EoR challenge

Global 

T ~30mK in few MHz

S/N easy – can reach a few mK in few hoursT/T < 10-4 to10-5Calibrate the complex gainMinimize the number of unknowns that can couple to EoR

Remove the forgrounds

Remove the additive constantCorrelation receiver

Eliminate LNA additive noise

Position switching

T now very small so large antenna and long integration times

Correlation interferometer

Arrays

Statistical detectionDirect detection

Zero spacing interferometer

Zero spacing interferometerSlide5

From CoRE to ZEBRA

CoRE

(Chippendale)

ZEBRA  SARAS 

ZEBRA II

Calibratable

receiver

CSIRO

RRI

MRO

July 2013

5Slide6

COREfrequency independent antenna beamSlide7

Global EoR system RRI Bangalore

Ravi

Subrahmanyan

Ron

Ekers

Peter Shaver

A.

RaghunathanSlide8

Zebra – fat dipole v1Slide9

ZEBRA Global EoR Experiment

ZE

ro

-spacing measurement of the Background RAdio spectrumPartially reflecting resistive screenVirtual zero spacing interferometer

Removes all additive errorsModulate screen ?

Subrahmanyan,

Ekers

Patra

Partial

reflector/transmitter

XSlide10

The space beam-splitter: a resistive wire mesh

Need a space beam-splitter before the antenna

A lossless screen (e.g. a conducting grid)

transmitted & reflected waves are orthogonalResistive wire meshThickness of wire < skin depthFrequency independentRe-radiated fields no longer cancel the incident field on the far side of the wire screenLumped resistance on scale << 

Practical solution instead of resistance wireSlide11

Building resistive screenSlide12

The Resistive Screen

copper wire + lumped resistors

resistor value

= free space impedance/2

3x4 metres

holes to reduce wind loading

Roll up for transportSlide13

ZEBRA – interferometerfirst CMB correlation 20 Jan 2011

3.4m

1.5m separation

Max sky coverage at zero spacing 26%

Contributions to correlated output

Global sky signal

Screen radiating

1.5m interferometer sky correlation

One path through screen

Both paths miss screen

Ferrite absorberSlide14

ZEBRA at GauribidanurSlide15

Zebra correlated output

Baseline ripple

changes with LST

Repeats each dayMultipath scattering of galaxy foreground signalShifted location …….Slide16

SARAS receiver evolutionSlide17

SARAS receiverPatra &

Subramanyan

, EA (2013)

88-175MHZDifferential correlation spectrometerDigital correlator well separated from receiverMinimize number of parameters in solution (11)Solve for multipath propagation from internal reflectionsEg noise from receiver inputSlide18

SARAS internal reflectionsShort connections to keep broad bandwidthLong connections to decrease couplingSlide19

SARAS internal reflectionsShort connections to keep broad bandwidthLong connections to decrease couplingSlide20

SARAS waterfall plotSlide21

Pulse calibration ?

Pulse injected at

Parkes

vertexPulse reflected from Parkes focus

Inject and integrate short (



sec

) pulses

Calibrated

noise spectrum

Understand & c

alibrate reflections

Nipanjana

Patra

, Paul RobertsSlide22

Pulse calibrationBand limited pulse with -20db reflectionPulse repetition rate 10

6

Hz

Accuracy 0.05%Slide23

Other Global EoR Experiments

WSRT:

Lunar occultation

EDGES: Rogers & BowmanPolynomial fits Δz > 0.06Absolute calibration of components for wider bandwidthsBIGHORNS: Sokolowski, Tremblay, Wayth, Tingay

⑫

Low rfi site, high stabilityCore II: Bannister, Chipendale, Dunning

①

Precision self calibrating receiver

DARE

Go to moon to avoid ionosphere and rfi

July 2013

23Slide24

Estimates of the sources of error and their magnitude expressed as the residuals to fits with increased numbers of parameters along with the bias in EOR estimation

Parameters of 10 parameter solution:

1] EoR signature

(30 mK, 50@145MHz)

2] scale

(assumes spectral index of -2.5)

3] constant

(ground emission)

4] frequency

-2

(ionosphere emission)

5] frequency

-4.5

(ionosphere absorption)

6] Magnitude of antenna S11

7] Magnitude of LNA S11

8] S11 phase error9] S11 delay error

10] temperature scale

Estimate of errors using simulations – for more details see EDGES memo 99

Rogers & Bowman

(EDGES memo #99)Slide25

BIGHORNSSokolowski

,

Tremblay

, Wayth, Tingay ⑫Low rfi site, high stabilityDynamic spectrum normalised by the medianDynamic range 2%Required 10-4

Day

200MHzSlide26

CORE2: A global EOR experiment with a self-calibrating receiver on two antennas

CORE2: A global EOR experiment with a self-calibrating receiver and two antennas|

Keith Bannister | Page

26

CORE2-MONO

60 Degree beam

Optimised

for frequency

Independence

and low RFI and

CORE2-DISH

5 Degree beam

Optimised

for foreground removalSlide27

27

The Richness and Beauty of the Physics of Cosmological Recombination

well

defined quasi-periodic spectral dependencephotons are coming from redshifts z 1300−1400i.e. before the time of the formation of the CMB angular fluctuations

Chluba

&

Sunyaev

A&A, 458, L29 (2006)Slide28

28Observing

All sky so dish size is not relevant

Needs a wideband spectrograph in 2-10 GHz range

Can measure multiple independent patches of skyMany dishes/receiversNeed lowest possible TsysCan integrate over all oscillationsSpectral dependence is accurately predictedSlide29

29Sensitivity Required

Need

Δ

T/T = 10-8Tsys = 25KΔν = 1010 Hz2 pol 100

antennasTime = 1month (3.106

sec)ΔT/T = 25/(

√(

10

10

.

2.100.3.10

6 .)) = 10-8 !