Instrumentationfor
Cosmic Microwave Background (CMB) Telescopes
Maria SalatinoStanford University and KIPAC
AIMS Future of Science Kigali, July 7 2019
Pictu
re credit: act.p
rinceto
n.ed
u
• 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
ACT – pic: J. Ward