Design, deployment andcommissioning of the Simons Arrayexperiment
Daisuke Kaneko, from KEK IPNSWhat’s CMB

2EventInflation

After 380k years from beginning of theuniverse, temperature was lowered
down to 3000K, photon decoupled frommatter, to freely travel the universe.

Whatdominate theuniverse? energySize of the universe

Cosmic neutrino backgroundCνB

Gravitational wave
GW

Electromagnetic wave
CMB

Big bang

radiation

Recombination

matterReionization

dark energy
TodayTimeKnown facts about CMB

3Intensity

0.5 , ℓ=360
size of moon

wave number [cm-1]

CMB spectrum agrees extremely well with
Planck’s black body radiation formula.
Temperature 2.725 K
Peak is at λ ~ 2 mm, ν ~ 150 GHz.

Radiation strength (temperature)
has non-uniformity. It’s usuallyindicated in power spectrum.

Why more CMB?

4

Temperature non-uniformity is thoroughly searched in previous experiments,
but there are more information can be derived from polarization.

E mode+E mode-B mode+B mode-high-ℓ E mode, number of light relic particle “𝑁eff ”
high-ℓ B mode, sum of the neutrino mass “Σm𝜈 ”very low-ℓ E mode, optical thickness of universe “𝜏”low-ℓ B mode, tensor-scalar ratio “𝑟”etc. etc.

How polarization generated

5mode

mode
Gravitational wave

Wave vector

Sound wave

E modeE modeB modeB mode from inflation

6Unknownmechanism

Inflation at
early universe

Primordial GW(tensor-scalar ratio)

Tensor to scalar ratio,𝑟

From measured
amplitude of B mode,
limit for the inflation
model can be set.

Planck 2018 results. VI.
Cosmological parameters
arXiv:1807.06209[astro-ph.CO]

B mode polarization
Spectral index,

𝑛𝑠CMB observation and neutrino mass

7pure E

weak lensing effectSum of the neutrino masscan be measured as theheight of B mode peak.

B mode power [μK]

Dark matter and normal
matter concentrate to form
largescale structure, but
neutrino don’t in small scale.

E + small B

Dark matter
Normal matter
Neutrino

Degree of spherical harmonic function

How CMB could be measured

8

CMB is radiation from
low temperature 2.725 K,
B mode is nK order.

mm range wavelength
typically 2-3 mm

Special optic elements

photon energy is weak100 GHz -> 0.4 meV

Not observe one photon,Continuously scan the sky.

Detector as sensitive as
possible. Transition Edge
Sensor is trend now.

Readout multiplexing

Cryogenic readout
Everything higher than
CMB temperature can benoise source
Cryogenic optics

telescope size and observation band

9BICEP: 25 cm

ACT: 6m

Telescope Size
Large telescope has better angular resolution, but fluctuation
at larger scale is worse. Small telescope is opposite.

Band (frequency)
2 major polarized “foregrounds”, Thermal dust at highfrequency, and Synchrotron radiation at low frequency.

10POLARBEAR / Simons Array’s strategy• Location• Chile, Atacama desert• Larger sky, better accessibility than Antarctica, but Inferior at sky condition• Optics• 2.5 m telescope, adopt half-wave plate (HWP)• Unique middle-sized telescope among CMB experiments• HWP modulates polarization to reduce 1/f noise at low frequency• Observation band
• 150 GHz (PB) → 90, 150 (PB-2a,b) + 220, 270 GHz (PB-2c)

Basics of PB-2/Simons Array11NicholasSimonsTelescope

PB-2AHuan TranTelescope

PB-1↘PB-2CPaulSimons
Telescope

PB-2B• Chile, Atacama, Chajnantor plateau• >100 recearchers from US, Japan, etc. 8 contries• predecessor: PB-1 observed from 2012 to 2016
• 3 telescopes equipped with POLARBEAR-2(PB-2) receivers, number of TES are 20 times more
• Aiming at (1σ error)• tensor to scalar ratio r 0.006 (at r = 0.1)
• neutrino mass sum Σmν 40meV (conbine with DESI experiment)

12Optics of PB-2
primarymirror• Huan Tran Telescope: 2.5 m off-axis Dragone system• 50 cm receiver window, 3 alumina lenses
Signal port

ReceiverHalf-wave
plate

Secondarymirror

Detector
tower

Collimator
lens

Aperture stop+ filter

Aperturelens

FieldlensZotefoamwindow

Alumina
IR filterResistance [Ω]13Sensor of SA

1.6

1.4

Normal state

1.2

Transition toSuper Conductance

1.0010• Transition Edge Sensor• Wide-band sinuous antenna

20 30 40
Input [pW]

Feed line

Bling

Load resister
Antenna →3 mm
Readout →PB-2a detector structure

Frequency Filter

TES (Al/Mn)

0.1 mmReadout of SA
carrier

C2LLRbias

nuller

DAC

x40…
0.3 K

SQUID
4K

amplifierDAN
readout

demodresidual
readout
room temperature
ADC

RTES1 RTES2

Modulation
Synthesis

DANfeedback

SA adopts frequency
multiplexing, 40 channels areread with one SQUIDC1DACFPGA control &Front-end PC

14

LC circuit :Inductance and capacitance are
implemented as superconducting micro stripe.
LC resonance frequency 1-4 MHz
SQUID circuit board at 4K stage

transportation to Chile

15

Receiver prepared for packing

Packed in wooden box
Disassembled optics tube

Special palette withdumping spring

16

Assembly at the site
Assembly work was performed at high bay building.
It finished in 3 weeks as expected.

Mount to telescope

17
Lifting receiver by hand.
It took a half day
Temporary hoist system
mounted on telescope

Truck was hired forreceiver transport

Refrigerator’s gasket replace on
telescope, hardest work in my stay.

First observations

18

In the end of year 2019, all receiver cooling,telescope control and readout electronics got ready.
First light was achieved in beginning of year 2019.
Sun scan on 2018 December 30

Sun !

Venus scan on 2019 January 5

Venus !

Planet observation

19Jupiter observation 90 GHz TESs averaged

Telescope focusing performance is checkedwith planet observation.
After several alignment work of receiver,similar resolution as design was obtained.
Expected beam width (FWHM)
3.5 arcmin (150 GHz)
5.2 arcmin (90 GHz)Role
• Evaluation of detector

Stimulator• Response magnitude
gain (g )• Response delay
time constant (τ )• Use as a reference withconstant intensity

receiversecondary

Optical input

Calibration source: Stimulator

primaryTin
𝑔 = 𝑃det /𝑇inTES output

20ττPdettimePB-2a stimulator design21
optical hornheater unit Black body radiation from ceramic heater (~700℃)

is modulated with chopper and is emitted from thepipe to the receiver.

21 cm

pipe

motorchopper

Ceramicheater

cross-section image of heater
unit. Heater unit could bereplaced on telescope withminimal cabling work.

fan23 cmencoder
inner coverCurrent implementation

22
Signal cables

LabJack
thermometerreadout

Motor controller

Switch etc.

5V DC supply

Power cables

Thermometercables

Mount jig
Connectors

ArduinoEncoder readout

raspberry pi
main controlControlling electronics are installed in a 19” box,
and it is inserted in a telescope co-moving rack.

Operation principle ofstimulator
37
19

5929

13Time1.
Operate stimulator withvarious modulation frequency.

9 Hz
13 Hz

Time (superposed)
2.
Measure detector output
amplitude for each frequency

Amplitude

5 Hz

44

TES output

Modulation [Hz]23

Frequency [Hz]3.
Fit curve to obtain gain andtime constant of detector

Long-term stability

24

Stimulator have worked ~150 days since installation
without serious trouble. No deterioration is seen.

Heater temperature [degC]

PB-1 stimulator

690

685

PB-2astimulator
debut

inspectionwindmaintenanceshieldinstall

chopper closed
chopper open

680
675
19-05

06

0708

strong wind

09

10

11

12

20-01

02

03

PB-2b arrived at site

25

Picture when container arrived

PB-2b assembly at high bay• PB-2b container is at site, and assembly work started• Telescope, electric apparatus etc. are prepared in parallel.
2020/3/27

Status of the site26
• 2020 March, COVID-19 finally landed Chile. The
infection spread whole country.
• We decided evacuation from the site.
• All system were shutdown, instruments wereprotected from weather, and all personnel
evacuated.
• As of August, we start discussion how to returnto the site.

Covered telescope

27

Next experiment, Simons Observatory
Next experiment of Simons Array,
Simons Observatory is in preparation.
Feature is combination of small telescope forlarge-scale, and large telescope for small-scale.
Total number of sensor is about 3 times morethan SA.

Each component is being produced, assembly
and test are being performed.

28

Future plan of ground experiment

NOW

POLARBEAR

SimonsArray

SimonsObservatory

CMB-S420122020

2021

Late 20s~ 1,000~ 20,000~ 60,000~ 500,000

0.006

0.003

0.001

29Fin.
Thanks for listening3031()CMB

BICEP/Keck, SPT
ACT, POLARBEAR, CLASSQUIJOTE, GroundBIRD ()

32
2000s

2010s

2020s

WMAP

Lite
BIRD

PlanckEBEXBOOMERranG
DASI

BICEP

SPIDER
BICEP3

BICEP2BICEP Array

Keck Array
SPT

SPTpolACT

QUIET

101,000

CMB
S4

SPT3G

ACTpolAdvACT

POLARBEAR

PB-210,000

Simons Obs.

500,000

POLARBEAR (PB)

335,200m
PB-1
UC(KEK, IPMU)

2012
B

8100
PB-2
Simons Array201973

34
22250 km

35

36

WD37
←

→→←

38
Wikipedia

Wikipedia

1.2m

1.5m

1.0m

1.4m

39

James ax

POLARB
EAR
ACT

CLASS
SO

ALMA

TAO

POLARBEAR

40

CLASS

ACT

3

Bad weather in northern Chile

41

From the end of January to mid of February, there was unusually heavy
rain in Atacama desert. Site crew needed to escaped to Calama, a 100km
away city.

Wall of hotel room wasbroken

Flood in middle of desert

Road to site was damaged42100