次世代赤外線天文衛星 SPICA 搭載用
遠赤外線観測装置 SAFARI
Toyoaki Suzuki (JAXA)
P. Khosropanah, M. Ridder, R.A. Hijmering,
J.R. Gao, H. Akamatsu, L. Gottardi, J. van der Kuur
and B.D. Jackson (SRON)

Japan Aerospace Exploration Agency

SPICA: space mission for mid-& far-IR astronomy
 Telescope: 2.5 m & <8 K
-Natural background limited Infrared (IR) observations→ Need ultra-sensitive IR detectors

34–210 μm

 IR instruments-SMI (12-37 µm)-SAFARI (34-210 µm)-Three-band
grating spectrometerswith TES bolometer arrays

M-bandL-bandS-band © Cambridge Univ.

Toyoaki Suzuki: IR-detector workshop Dec.9, 2015 2

Noise Equivalent Power (NEP)
required by SPICA/SAFARI
Minimum detectable input power to have
S/N=1 with Tint=0.5 sec

Higher sensitivity = Lower NEP
ISO-Herschel era

SPICA/SAFARI~10-16 -10-17 W/√Hz

2x10-19 W/√HzToyoaki Suzuki: IR-detector workshop Dec.9, 2015 3

Transition Edge Sensors (TESs)

Tc
NormalstateC

ResistanceI

Superconductingstate

ΔP → ΔT → ΔR

Temperature

Toyoaki Suzuki: IR-detector workshop Dec.9, 2015 4

Typical TES pixel for SAFARI/S-band
TES (Ti/Au)

IIsland (SiN)
VaccumCLeg (SiN)

Absorber (Ta)

Thermal bath

Intrinsic noise = phonon noise→Noise Equivalent Power (NEPph)∝ √G
Toyoaki Suzuki: IR-detector workshop Dec.9, 2015 5

Long-standing questions (1)SRON-TESs fabricated by KOH wet-etching
SiN legs-Width (W ) = 1 µm
-Thickness (T ) = 0.5 µm-Length (L ) = 400 µm
Gmeas = 330 fW/K
NEPmeas = 4.2x10-19 W/√Hz (best)
Khosropanah, Hijmering+ 2012

→ Deep Reactive Ion Etching (DRIE)

Q1. Can we achieve lower G and thus NEP values
by making narrower and thinner SiN legs??
Toyoaki Suzuki: IR-detector workshop Dec.9, 2015 6

Long-standing questions (2)Suzuki+2014

Multi-body models
with PextNEPph

NEPmeas/NEPph~2-3 (typ.)Khosropanah, Hijmering+ 09,10,11,12

Excess noises
1) Extra-phonon noise (f >~10Hz)
Ctes~Cisland & Clegs

2) Photon noise

CTES TES
G0

Cisland IslandG1Q2. Can we reduce the extra-phonon noise

Thermal bathby making lighter SiN island and SiN legs??

Q3. How dark is our setup??
Toyoaki Suzuki: IR-detector workshop Dec.9, 2015 7

New TESs fabricated by DRIE
- Deep Reactive Ion Etching (DRIE) process success- Narrow SiN legs ~0.5-0.7 µm- Thin SiN legs and island ~0.2 µm
TES(TiAu)

50 µm

Fabricated by Marcel Ridder (SRON)

Small island
without absorber

Large island
without absorber

Large islandwith absorber

200 µm200 µm200 µm8

Do not blow a puff of air, please!!

9AC measurement setup SQUIDs

LC resonators
TES array chip

FDM assembly

Stray-light absorber

FDM bracket+Nb tubeToyoaki Suzuki: IR-detector workshop Dec.9, 201510

FDM readout
Cold part

Warm part

10pix-FDM system
1-3 MHz resonators
df=100 kHz
1 MHz

3 MHz
Toyoaki Suzuki: IR-detector workshop Dec.9, 201511

G (fw/K)

Measured thermal conductance

Khosropanah, Hijmering+ 2012

WT/L (µm)
Toyoaki Suzuki: IR-detector workshop Dec.9, 201512

NEPdark (x10-19 W/√Hz)

Measured NEPs
1.1x10-19 W/√HzSAFARI req.

Tc=94 mK,P =1 fW @50mK
G=30 fW/K

Small island
Tc=93 mK,P = 2.0 fW @50mK
G=60 fW/K1.5x10-19 W/√HzSAFARI req.

Large island

Meet the SAFARI requirement
Frequency (Hz)Toyoaki Suzuki: IR-detector workshop Dec.9, 201513

NEPdark (x10-19 W/√Hz)

Measured NEPs
1.1x10-19 W/√Hz

Tc=94 mK,P =1 fW @50mK
G=30 fW/K

Small island
NEPph

Tc=93 mK,P = 2.0 fW @50mK
G=60 fW/K

1.5x10-19 W/√Hz
Large island

NEPph

Achieved phonon noise level (f<~100Hz)
Frequency (Hz)Toyoaki Suzuki: IR-detector workshop Dec.9, 201514

NEP-evolution track of SRON TESs
Dark NEP(x10-19 W/√Hz)

100.0

10.0

1.0

This work!!

0.1
2008

2010

2012

2014

2016

2018

2020

Toyoaki Suzuki: IR-detector workshop Dec.9, 201515

Excess noise
Normalized NEP

Legs: x3 mass
Island: x14 mass

Reduced excess noise
Frequency (Hz)Toyoaki Suzuki: IR-detector workshop Dec.9, 201516

NEPdark (x10-19 W/√Hz)

Darkness of current setup
Similar TES properties,
but with and without absorbers

Tc=87 mK,
G=58 fW/K
Psat=1.9fW@50mK

With absorber

NEPphoton~5x10-19 W/√Hz

Tc=93 mK,
G=63 fW/K
Psat=2.0fW@50mK

No absorber

Need a stray-light free setup
Frequency (Hz)Toyoaki Suzuki: IR-detector workshop Dec.9, 201517

Summary
Ultra-low G TESs were fabricated by DRIE
 Without an absorber
We measured an electrical NEP as low as 1.1x10-19 W/√Hz,
which achieved the phonon noise limit, and alsoa reasonable response speed (<1 msec).

 With an absorber
We confirmed a higher NEP (~5x10-19) due to stray light.

Toyoaki Suzuki: IR-detector workshop Dec.9, 201518