Instrumentationfor

Cosmic Microwave Background (CMB) Telescopes

Maria SalatinoStanford University and KIPAC

marias5@stanford.edu

AIMS Future of Science Kigali, July 7 2019

Pictu

re credit: act.p

rinceto

n.ed

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• Cosmic Microwave Background (CMB)

• Ingredients for a CMB telescope

AN EXPERIMENTAL COSMOLOGY TALK …

from 1014m to 10-8m

from 10-37s to 10-8s

from 1028K to 0.1K

primordialuniverse

CMB detectors

COSMOLOGY: A TRAVEL

… SPANNING MANY ORDERS OF MAGNITUDE

primordialuniverse

CMBdetectors

Working condition of a CMB instrumentalist:0m to 5200m above sea level

-10°C to 30°C10e5 part(>0.5um/min)@lab to 10 part(>0.5um/ft3)@cleanroom

from 1014m to 10-8m

from 10-37s to 10-8s

from 1028K to 0.1K

size ofvisibleuniverse

HISTORY OF THE UNIVERSE1. expansion + cooling down2. anisotropy

CMBpicture credit: nasa.gov

picture credit: nasa.gov

size ofvisibleuniverse

opaque

HISTORY OF THE UNIVERSE1. expansion + cooling down 2. anisotropy

CMB

transparent

105K, 60eVH+g ↔p+e, no Hydrogen formation

scattering Thomson g +e ↔g +e

g

e-

p+ p+ p+

THE OPAQUE UNIVERSE

105K, 60eVH+g ↔p+e, no Hydrogen formation

scattering Thomson g +e ↔g +e

g

e-

p+ p+ p+

the photon is scattered

THE OPAQUE UNIVERSE

105K, 60eVH+g ↔p+e, no Hydrogen formation

scattering Thomson g +e ↔g +e

T=380,000 years, 3000K, z=1100Recombination (Hydrogen formation) + LAST SCATTERING

g

e-

p+ p+ p+

H H H

the photon is scattered

THE OPAQUE AND THE TRANSPARENT UNIVERSE

105K, 60eVH+g ↔p+e, no Hydrogen formation

scattering Thomson g +e ↔g +e

T=380,000 years, 3000K, z=1100Recombination (Hydrogen formation) + LAST SCATTERING

g

e-

p+ p+ p+

H H H

the photon is scattered

the photon is NO MORE scattered

THE OPAQUE AND THE TRANSPARENT UNIVERSE

COSMIC

MICROWAVE

BACKGROUND

related to Universe

THE CMB

COSMIC

MICROWAVE

BACKGROUND

past(optical)

today(microwave)

future(radio)

expansion of the Universe

related to Universe

THE CMB

COSMIC

MICROWAVE

BACKGROUND

past today future

expansion of the Universe

related to Universe

411 CMB photons/cm3

is everywhere!

past(optical)

today(microwave)

future(radio)

THE CMB

John Mather andGeorge SmootNobel Prize 2006

Guess who isJohn Mather ...

THE CMB IS A BLACK BODY AT 2.725 K

Fixsen et al., ApJ 473, 576, 1996

red spots -> warmer/denser regionsblue spots -> colder/less dense regions

SEEDS ->>> BOTH EVOLVED WITH GRAVITY ORIGINATINGTHE STRUCTURES WE OBSERVE TODAY

OUR UNIVERSE WHEN IT WAS 380,000 YEARS OLD

0.5° deg

Planck satellite

CMBANISOTROPIES

Imagine to be a FREE electronsurrounded by an ISOTROPIC distribution

of CMB photons.

What you would do?

FREE= not boundedinside an atom

e-

CMBphotons

Imagine to be a FREE electronsurrounded by an ANISOTROPIC distribution

of CMB photons.

What you would do?

e-

FREE= not boundedinside an atom

CMBphotons

ANISOTROPY SCATTERING

LINEAR POLARIZATION BY THOMSON SCATTERING

Nowimagine an isotropic distribution …

How it could become anisotropic?

Image from BICEP2, http://bicepkeck.org/

InflationHigh-energy physics -> GUT

LINEAR POLARIZATION BY INFLATION

THE CMB

Black Body at 2.725Kcontinuum spectrum

0.5°linearly polarized <0.3uK

CMB-S4 Science Book

SEVEN INGREDIENTS FOR

A CMB TELESCOPE

T = (2.72548 ±0.00057)K

CMB = Black Body at

Max emission at 150GHz

Fixsen et al., 1996

1. FREQUENCY

lmax T = 2.9 10-3 m*KWien’s Displacement law

30%150GHz

temperature

random motion of particles

noise

2. CRYOGENIC TEMPERATURES (0.1, 2K, 77K)

MINIMIZE:RADIATIVE LOAD -> COOLING TELESCOPE (e.g. MIRRORS, FILTERS)

CONVECTION -> HIGH VACUUM 10e-6 mbar

CONDUCTION -> REDUCE NUMBER OF ELECTRICAL WIRES (MULTIPLEXING)

EVERYTHING ABOVE 0K EMITS RADIATION…

plot from de Bernardis P.

ATACAMA COSMOLOGY TELESCOPE (ACT)

1.5m

Atacama desert - 5,200 m above sea level

ACT CRYOSTAT

Thorton R.J. et al, ApJSS 227,2 ,21, 2016

BICEP3

Ahmed et al., SPIE 9153, 9153N, 2014

55cm

South PoleCRYOSTAT

BICEP3 Collaboration

3. DETECTOR

p.slide adapted from P. de Bernardis

• The CMB spectrum is continuum• Wide band detectors• High sensitivity

CMB

AMGUL(angularselection)

(spectralselection)

Readout Electronics

Detector

3. DETECTOR R(T) CMB photon -> power depositedon the Au meander-> delta T -> delta R

we measure delta Current

AlMn bylayerAu meanderSiN legs

(thermal isolation)Li D. et al, JLPT 184,66, 2016

280umTransition Edge-Sensor (TES)Irwin K. and G. Hilton, 2005

normal

superconducting

transition

DP -> DT -> DR -> DI

A typicalcleanroomlaboratory

Chalmers MC2Göteborg

1. DETS COOLED DOWN AT 0.1K(-> this maximize their sensitivity)

NOISE from DETS itself (since T>0K)

2. Also the CMB radiation is noisy itselfCMB= photons fluctuations in their time of arrival -> Delta NN=number of photons

3. Current dets technologyDETS are PHOTON-NOISE LIMITED

-> they are so good that their sensitivityis limited by the noise in your target radiation

To detect your target radiation we need more sensitivity….What we can do?

4. DETS…. How…?

AdvancedACTPolHF

29 cm

4. KILOPIXELDETECTORARRAY

0.1K

Henderson S. et al.,SPIE 9914, 99141G, 2016

FEEDHORN ARRAY

Coupling incoming radiation to detector arrayWard J. et al., SPIE 9914, 991437, 2016. Simon S.M. et al., SPIE 9914, 991416, 2016

AdvancedACTPolHF

29 cm

0.1K

CMBPHOTONS

4. KILOPIXELDETECTORARRAY

Henderson S. et al.,SPIE 9914, 99141G, 2016

printed circuit board

flex

Cu support

componentsfor thereadout electronics

detector array

1 cm

• 15μm thick polyimide• one line:• Al 50 μm wide, 70 μm pitchPappas C. et al., JLTP 184,476, 2016

• 2012 TESes• 20,000 wire bonds• 300 readout chips• 4,056 flex traces

AdvancedACTPolHF

Can we observe the CMB from NYC - Times Square?

roto-vibrational emission lines of O2 (60 and 119 GHz)and H2O (at 22 and 183 GHz)

5. SITEDRY & HIGH ALTITUDE

PRECIPITABLE WATER VAPOR (pwv)

ACTPol bandpassesThorton R.J. et al, ApJSS 227,2 ,21, 2016

1mm pwv4mm pwv

NE

Necessity of shields

Sidelobes:like yourself(view capability awayfrom direction of view)

Planck’s law T4

IMPORTANCE OF LOW SIDELOBES

(2.7K)^4 1 << 1srad (300K)^4 10^(-7) 2pi sradslide from P. de Bernardis

ACT

BICEP3

SouthPoleTelescope

BICEP3

Kosowsky A. et al., New Astron.Rev. 50, 11, 969, 2006

BICEP2 Coll., ApJ 792, 62, 2014

What do you do,Maria?

ALICPT-1

• ALI CMB Polarization Telescope-1• First CMB experiment on the Tibetan plateau, 5250m a.s.l.• Northern hemisphere• O(4) AlMn TESes, 4 modules late 2020, umux readout

HIMALAYA MOUNTAINS

TIBETANPLATEAU

ALICPT-1SITE

• Site construction finished by IHEP & NAO• Control system\DAQ by IHEP & Stanford• System integration\Calibration by IHEP & NTU• Telescope mount under test in Beijing• Cryostat receiver designed at Stanford

fab is starting ~mid July• Detector array design at NIST• Readout design at ASU

CURRENT STATUS OF ALICPT-1

1. Thermal history/expansion universe Frequency 150GHz2. Thermal history/continuun spectrum Wide band 33% 150GHz3. Small signal Large number detector arrays 2,000 TESes4. Thermal noise Cryogenics cryostat, multiplexing readout 5. Atm transmission Dry site Atacama, South Pole, Tibet6. Angular dimension CMB anisotropies Angular Resolution 0.5m diameter7. Inflation theory Polarized CMB OMT/polarizer

Reason/origin Ingredient kind Ingredient

Target:Measure a very small polarized signal, <0.3uK

SEVEN INGREDIENTS FOR A CMB TELESCOPE

Remember to look up at the stars and not down at your feet.

Try to make sense of what you see and wonder about what makes the Universe exist.

Be curious.

Stephen Hawking

marias5@stanford.edu

ACT – pic: J. Ward