1超伝導共振器を用いた広視野電波カメラの開発

新田冬夢, 中井直正, 久野成夫, 永井誠, 今田大皓, 山田淑乃, 久松俊輔 (筑波大学)
関本裕太郎, 三ツ井健司, 岡田則夫, Agnes Dominjon, 野口卓, 松尾宏 (国立天文台
関根正和, 関口繁之, Shibo Shu (東京大学)
成瀬雅人 (埼玉大学)

2015/11/18：南極で切り開くテラヘルツ天文学発表概要
1. 南極10m望遠鏡搭載に向けた超伝導カメラ- カメラシステムの概要- 機械設計, 熱設計, 検出感度など

2. 多画素カメラ実現のkey technology- Microwave Kinetic Inductance Detector- レンズアレイ & ホーンアレイの開発- シリコンレンズを用いた冷却光学系- 極低温における反射防止コーティング- 0.1 Kへの冷却

3. 南極30m望遠鏡に向けて
4. まとめ2

10 mtmm]
多画素電波カメラの重要性thh

3m A.W. Blain et al. / Physics Reports 369 (2002) 111 – 176¯`{~ 2.5 m çzØ¬öþòýºè
電波カメラ：多素子u±-ÝČýºæÆó_ã¤-ÊĎ南極テラヘルツ望遠鏡

14010+0253
b²{ā¦mvr(Ò1000 km [ā£­:G?vr)Č ( (Ò 60kmcD galaxy"Ă+,:G?vrå+*
14011+0253
N*ĊFig. 2ċĎ +(µĉ 3800m ĉČ¶½č20 ďč80 ²r*Ď
14009+0252
$Č{¶L·Ü¶ą  ČùÓ%Vra\Î)Č2<>B»( THz {¶îõÄ²$ĉĊFig. 3ċĎ (§ÿÉ)ČòÖ»Ą»á¾&¼ä
14010+0252
t á¾%÷*Ď#Č¨Ä 68 %Ċ1994, 95
同時に観測が可能sċČ¨|Ä 85 % Îąĉ Čÿ[Y. Onodera
Fig. 4 A schematic illustration of the 10 m THz
sĈð
5.8 m/sReport,Î)Č
10 m/s RIĈ
Blainetal.,
Physics369,
111−176,2002
mparison of deep optical and submm views of the sky. The background image is a 3-color optical image ofter of galaxiesą
Abell 1835 atĎthe low=moderate
redshift z = 0:25
(Smail et al., 1998b) taken using the 5-m+(():G?vr2<telescope
遠方宇宙の暗黒銀河の大規模サーベイ観測pe, overlaidwiththe14-arcsec
resolution
contoursofaSCUBA
850-!msubmm-wave
imageofthesame
ALMA,TMTto theetc
et al., 2000a).>B»ČTHz
North is up and East»á¾rIªĉ®T)ČÃ
left. The brightest SCUBA galaxies at (−45; −15), (65,0) and=nd the central
9 cD galaxy( ((Edge et al., 1999), all have clear radioz detections at a frequency of 1:4 GHz in→多画素電波カメラが必須
1THz
RIOIrIoHá¾hÛ
発見した銀河の詳細観測
higher spatial
resolution than the SCUBA contours, obtained at the Very Large Array (VLA), supporting theirtmbright SCUBA*
galaxyat (−45;−15) is associated with SMM J14011+0253, an interacting pair of galaxies
-ÍĎ= 2:56 in the background of the cluster (Frayer et al., 1999). Spectacular fragmented structure appears in thecomponentSCUBA-2of thisHgalaxyČb²Ã«pćČkin Hubbleimages (Fig. 18). ¿#)t Space Telescopee (HST)m 350-GHz
広視野観測
t¹*hÛ*$ČĉiI
sThe commissioning
SCUBA-2
tzSub-Millimeter Arted at longer mm wavelengths.
of the 8-element
1; Ho, 2000)åÚin Hawaii with baselinesof up to about 500＝m, the!rst
広視野大口径望遠鏡+ 多画素電波カメラ+(ĊFig.
4ċĎ#Č!
m on Mauna Keatsubmm-wave interferometer, will provide images with sub-arcsecond resolution. The much

4

南極10m望遠鏡：全体光学系
視野 : 1 @ F/6 focus

観測周波数→ 広域サーベイ観測・400 / 850 / 1300 GHz
副鏡(1.5 m)

400 GHz 850 GHz 1300 GHz
HPBW

18.6”

8.7”

5.8”

Optics design : H. Imada

主鏡(10m)

観測装置：カメラシステム

ヘテロダイン受信機
望遠鏡焦点 (F/6)(dia. 1m)

冷却光学系
( T < 4K)

電波カメラ
(T < 0.2K)

信号の伝送
集光系
ミラー or レンズ 信号の結合

検出器

5

カメラシステムの伝送光学系✴ ミラーによる反射系 (e.g. SCUBA-2) ✴ レンズによる屈折系 (e.g. APEX-SZ)

Schwan et al., Rev. Sci. Instrum., 82, 091301, 2011

Holland et al., MNRAS, 430, 2513−2533, 2013

Zotefoamwindowmesh LP filter
stack
HDPE imaginglens

LP shader

HDPE aperturelens

Horn array
280 mK stage
370 mK stage
Vespelstrut~3K stage
Pulse tubecooler
G10 strut
4 K thermallink

RF seal
Vacuum port
・視野1度で伝送するとミラーが巨大化
mirror to the detector arrays inside the cryostat. The beam envelope, shown
mes of the field-of-view for this projection of the optics. The arrow shows theFIG. 11. Drawings showing two orthogonal sections of the APEX-SZ cryostat.
・複数枚の組み合わせではアライメント
・屈折率が高いSi等のレンズを用いることでnside the cryostat window, whilst mirrors N4 and N5 relay the optical beamshown looking upward in the orientation used in the laboratory for work on thal plane調整が困難
units (FPUs).
can be removed for access to the focal plane and readout components. The alum
冷却部をコンパクトにできる
separates the optical and readout sections of the cryostat. Optical componentsorange, 380 mK in yellow, and the 4 K SQUID card housing and readout wirin
・ミラーの配置を工夫することで冷却部をthe cryostat is downward-looking, with the window pointed at a mirror on thescientific potential of SCUBA-2 with a selection of early re- ・低温での反射防止対策が必要
ngths
sults.
m for コンパクトにできる光学 / 熱 / 構造設計

Stage

65K

4K

1K

WmWmW

• 誘電体(Si)レンズを２枚用いたシンプルな冷却光学系• 1 の視野を７モジュールに分割• GM冷凍機２台+希釈冷凍機で0.1 Kまで冷却
FoV : 1

1.3THz0.4THz

28.3

410

0.2

1Conduction

6100

0.33160

Dilution

5500

Window

44.8

711.3

0.07

Total

84.1

1882

0.5

11Capacity

100

2400

120

Margin

16%

22%

46%

45%

0.65m

0.85THz
1.3THz0.4THz6uWRadiation
Dissipation

光学ー熱ー構造設計

0.1K

1.4m0.85THz
1.3THzreference : Stacey et al., Proc. SPIE, 9153, 91530L, 2014

7

焦点面アレイ
光学ー熱ー構造設計
4 K Si Lens
(dia. = 400 mm)

1 K Si Lens
(dia. = 110 mm)

超伝導カメラ
8.3 Design of 850 GHz-bands Camera

telescopefocus@F/6

レンズアレイ  145（0.4 & 0.85 THz)

24

ホーンアレイ（1.3 THz) 

Chapter 2. Millimeter/Submillimeter-Wave Kinetic Inducta

camera@F/1 focus

HDPE window(dia. = 340 mm)

Figure 8.8: A module design of 850-GHz band camera. (Left) Green part showed図
the2: 37 個のホーンが並んだホーンアレイ
silicon substrate, and the bottom space is used for the carbon based absorber. (Right)
The camera module with the 2977 pixel silicon lens array and the springs for fixing thecamera module and the lens array.

MKID Arraycold baffle

それぞれのホーンは 2F λ ∼ 15.7 mm 程
ビームサイズは約 15′′ であり、ここで計画

8

感度予想
coupling

400 GHzLens

No. of module
total beam

850 GHzLens

1300 GHzHorn

22

3

1800

5600

9000

Field of View

total : 1 degree

bandwidth [GHz]

4085

90

HPBW [″]

18.6

8.7

5.8

sky transparency0.90.80.38

cold optics efficiency

0.8

0.65

0.6

detector quantum efficiency

0.6

0.6

0.6

10-18, ~ 0.3 K

10-18, ~ 0.3 K

10-18, ~ 0.3 K

4.3 × 10-16

5.5 × 10-16

5.5 × 10-16

single beam NEFD [mJy・Hz0.5]

41.8

43.2

137.5

Sensitivity (5σ, Tint = 1h) [mJy/beam]

3.48

3.6

11.5

Sensitivity (5σ, Tint = 10h) [mJy/beam]

1.10

1.14

3.62

confusion limit [mJy/beam]~21.450.26

detector sensitivity (NEP [W/Hz0.5], Trx [K])photon noise NEP [W/Hz0.5]• 850 GHz以下：観測限界はconfusion limit• 850 GHz以上：観測限界は大気雑音

南極観測におけるKey Technology

9

南極という極限の環境で広視野観測を実現する多画素カメラを開発する✴ 重要となる開発技術(1) 多画素の効率的な読み出し、高い歩留まりを実現する検出器•

Microwave Kinetic Inductance Detector(2) 限られた焦点面に多画素を効率良く配置•

誘電体レンズアレイ & ホーンアレイの開発(3) 誘電体レンズを用いたコンパクトな冷却光学系•

屈折率の高い誘電体を利用する ( Si : ~ 3.4, HDPE ~ 1.5 )•低温でも使用可能な反射防止コーティングの開発•0.1 Kへの冷却Day et al., Nature, 425, 817−821, 2003 10

Microwave Kinetic Inductance Detector (MKID)✴ MKIDの動作原理

・マイクロ波帯で動作する超伝導共振器

マイクロ波 (3 - 9GHz)

C・入射光子によりクーパー対が解離→ 超伝導に由来する力学インダクタンスが変化→ 共振周波数 (f0) が変化→ f0の変化量 = 入射光子の強度に対応

超伝導ギャップエネルギー以上の光子を検出

CLm+Lkδf500 um

金：超伝導体(Al)黒：シリコン基板ex ) Al : > 90 GHz

入射前

入射後

f(LC)1/2✴ MKIDの利点
・共振器の長さをわずかに変えることで共振周波数が変化し、周波数方向に多重化が可能
・1つのアンプで1000素子程度を読み出せる → 他の超伝導検出器にはない特徴
MKID246

MKID344マイクロ波

S21 [dB]

MKID1

MKID1 MKID2

MKID3424038低雑音アンプ366.376

6.378

6.38

6.382 6.384 6.386
Frequency [GHz]

6.388

6.39

11608素子MKIDアレイの評価
・国立天文台クリーンルームにて素子を製作
50✴ 検出器歩留まり- ほぼ100%の非常に高い歩留まりを達成

45S21 [dB]584 / 608 ( ~ 96%)600 pixel MKID S2140353 inch wafer

304T(stage) : 0.1 K
Spacing ~ 2 MHz
4.555.5

66.5

Frequency [GHz]S21 [dB]4644

図 4.7: 600 素子 MKID S21 信号

4240
38366.355

6.363

6.371
6.379
一素子の検出器応答 Frequency [GHz]

6.387

6.395

Nitta et al., J. Low Temp. Phys., 176, 684−690, 2014 12

レンズアレイの集積化設計✴ 高い集積度を持つレンズアレイ→ 望遠鏡焦点面の大きさには制限があるため、集積度の向上が重要

レンズ内の電界強度

Z

レンズ表面XY
平面アンテナ・電界が集中するのはレンズ上部.2 Height
Dependence of Small-Diameter Silicon Lens
134

→レンズの上部のみを使用
有効部分

Chapter 7. Development ofエンドミルによる直接加工
a Wide-Field Camera System for Millimeter-Wave
Observations(国立天文台ATC)83

8.3 Design of 850 GHz-bands Camera

608画素220-GHzカメラFig 2.㻌 The ultra-precision cutting machine
レンズアレイ1

850GHz用3000画素へ(a) A photograph of the ultra-precision cutting(dia.machine
1.6 (Toshibamm) Machine ULG-300)(b) A photograph of the high speed spindle (Toshiba Machine ABC-20M)(c) A photograph when cutting the honeycomb groove~ 50 mm4ashi , Tom Nitta , Kenichi Karatsu , Masakazu Sekine , Agnes Dominjon , Masato Naruse , Takashi Noguchi
1. Department of Astronomy in School of Science, the University of Tokyo
Sekiguchi, Sugimoto et al., LTD Conference, 2015 13
2. National Astronomical Observatory of Japan
3. Institute of Physics, University of Tsukuba
4. Graduate School of Science and Engineering, Saitama University

ホーンアレイの開発

used
millimeter astronomy and CMB observations because of their excellent beam properties. We have designed and devel✴for広帯域ホーンアレイ
ed horn which is directly machined from an aluminum bulk at NAOJ machine shop. A prototype horn array with 4 pixels for obs
h is scaled・fromthe 120 - 270 GHz horn, has◎80
also beenthese horns, symmetric co-polarization, low cross-polariza
コルゲーションを工夫することで広帯域を実現– 180fabricated.
GHz hornInarrayin each frequency
band. The unnecessary part of horn array has been caved to reduce surface reflection and total weight. Hor
・ レンズアレイ同様、高速スピンドルを用いて直接Alブロックを加工• Corrugated pattern is a scaling of single pixel horn.
rn array with broadband planar OMT on SOI wafer has been designed.

2. Measurement• We have measured horn property, beam pattern and return loss, at room tempe(eg.[1]).
• The horn is made from aluminum bulk.
• Measurement results are consistent with the simulation.

◎ 120 – 270 GHz horn
専用の工具による直接加工(国立天文台ATC)・80 ­ 180 GHzの広帯域をカバー

3. Horn array MKID cameraθi = 0

Λ
11
≤
=
0.3
λ
ns
3.388

Λ
1≤λns

Λ
= 0.001
λ

レンズを用いた冷却光学系✴ レンズ材料の比較

ZotefoamwindowΛ1≤=
0.3=λns
3.388
λn→熱容量大、損失大、製作困難なため広視野化に向かない sλ→屈折率が大きいためHDPEより薄くできるΛ
1→南極に向けた広視野観測には必須の技術=nλns

HDPE imaging
lens

Horn array
280 mK stage
370 mK stage= 0.001

AR =λΛ=
nsVespelstrut~3K stage√✴ 反射防止コーティング・無反射の条件nAR =√nair · nSi = 1.84

(4)

LP shaHDPE alens(5)

Pulse tubecooler

nair · nSi = 1.84

→屈折率が大きいため、表面で約30%の反射損失があるλΛ=ns(3)

mesh LP filterstackΛ
11✓ HDPE (n ~ 1.5) : 屈折率が低くレンズが巨大化Λ✓ Silicon (n ~ 3.4) or Alumina(n ~ 3.1)(2) 14G10 strut
4 K thermallink(6)

Vacuum port

FIG. 11. Drawings showing two orthogonal sections of the APE

Schwanshown
et al.,
Rev.upward
Sci. Instrum.,
82, 091301,
2011
lookingin the orientation
used in the laboratory
be removed for access to the focal plane(7)and readout compon
nSi =can
3.388
separates the optical and readout sections of the cryostat. Optic

orange, 380 mK in yellow, and the 4 K SQUID card housing an
the cryostat is downward-looking, with the window pointed at a

λPulse-Tube Coolerd=(8)4 ·APEX-SZ
nAR uses a commercial pulse-tube refrigerator,B.

model PT410-OP3 manufactured by Cryomech, Inc.,52 toprovide cooling at 4 K and 60 K. In a pulse-tube cooler,high pressure He gas from a compressor is passed througha high heat capacity regenerator and then allowed to expand while in contact with a cold head, absorbing heatfrom the head. A motor outside the cryostat drives avalve which controls the pressure cycle of the pulse-tube.
There are no moving parts or valves in the cold section.

・Si, Aluminaと反射防止膜の熱膨張係数が異なるため、冷却時に剥がれる可能性がある

nSi = 3.388

・反射防止膜の誘電損失がある

1(9)Raguin & Morris., Applied Optics, 32, 1154−1167, 199315

反射防止コーティング：サブ波長構造✴サブ波長構造：対象とする波長より十分小さい構造を表面に形成	 

入射光

サブ波長構造	 

周期直径

有効屈折率の媒質
シリコン (n ~ 3.4)

単層膜多層膜(1 < n < 3.1)

シリコン (n ~ 3.4)

連続的な変化→ 入射光は空間構造を捉える事が出来ない： 空気とアルミナの間の屈折率を持つ媒質✴誘電体膜に対するメリット
1. 単一の物質で反射防止対策が可能
2. 冷却サイクルに強い
3. 膜による余分な誘電損失がない

大口径レンズには必須の技術

広帯域サブ波長構造の開発

16

Nitta + in prep

one-layer structure

two-layer structure

taper structure

T. Okada, Master Thesis, The University of Tokyo, 2015 17

ビームパターン測定✴ レンズアレイ+冷却光学系のシステム
MKID Camera-12-9-6・焦点面におけるビームパターン-3Lenses

50504040

Cold Baffle
MKID 130302020
1010Vacuum Window
focal planeflat mirror

MKID 30-10-10MKID 2-20-20-30-30-15-25-5-50-10-20-30-40
0-40-40-30 -20 -10 0 10 20 30

forms an integration cavity to couple the stray light directly
to the MKIDs. In a future experiment the amount of straylight can be reduced by a better design of the sample box14
and using intermediate optics to improve the coupling efficiency from the source to the lens-antenna. Here we takeadvantage of the fact that the background signal is common
for all channels and use it first to calibrate the responsivity
variation between the MKIDs. Then we flatten the spectra bynormalizing each spectrum on the background signal. As aresult, we obtain a spectrum for each channel which has a

30 mテラヘルツ望遠鏡に向けて032601-2

18

Endo et al., Appl. Phys. Lett.,103, 032601, 2013

Endo et al.

Appl. Phys. Lett. 103, 032601 (2013)✴ MKIDを用いた面分光測定
・ MKID + narrow band ﬁlterを用いた

on-chip上での分光・ FTS等に比べてコンパクト・ 焦点面に搭載しているイメージング用のカメラと可換・ R = f0/Δf ~ 1000

FIG. 1. (a) 3-port network model of a single submillimeter wave filter. kSM and kMW indicate the submillimeter wave and microwave wavelengths, respectively, which are reduced by the dielectric medium and also by the kinetic inductance of the superconductor. (b)FIG.
Networkmodel ofphasea singlechannel,
which
is a behind consecutive filters
2. Normalized
responseof theMKIDs
combination of a submillimeter wave filter and a microwave resonator (MKID). The channel is capacitively coupled
tothesignallineon
thefilterendandin the range of 600–700 GHz. All 5 curves haveto
been normalized so that thethe readout line on the MKID end. (c) Micrograph of a small area on the filter bank chip. The image captures theaverageantennabackgroundand 5 channelsof thefilter banknearresponse
outsidethe filter
band is equal to unity, andest to the antenna. (d) Double-slot antenna etched into the NbTiN ground plane. The horizontal line is the signal
is connectedto the forfilterbank.The stepped plots indicate
eachMSLcurvewhich
has been
given an offset
clarity.
(e) Submillimeter wave MSL filter, shaped like the character U. (f), (g) Sections of the MSL-MKID. (h), (i) Microwave
couplerthe MKID
reading
the measured
data, ofwhere
the solidforcurves
are out
Lorentzian fits to each set ofthe response. (j) Block diagram of the experimental setup.
data. (Inset) Example of spectra for two channels before dividing out thecommon stray light component. The vertical axis shows the phase responseof the MKIDs in units of milliradians. One of the spectra (solid blue curve)a filterlithography
with a frequency
measured band at 614 GHz, whereetched using electron has
beamandwithin
drytheetching.
At f ¼ f0 , the transmission reaches its maximum of
the other one (dashed black curve) has, by design, a filter centered at
Then a 1lm-thick layer759
of GHz,amorphousdepositedusing band. The spectrum ofx isthewhich is SiN
outsidemeasured frequency
2Q2i2
the 614vapour
GHz channel
after dividing
out the strayat
light component is included
plasma-enhanced
chemical
deposition(PECVD):(3)
jS31 j ¼
2&alsointhemainfigure,asindicatedby
thearrows.
300 C. We subsequently deposit a 200 nm-thick layer of Ta~3m✴ 30m望遠鏡に向けた電波カメラ

・10 mテラヘルツ望遠鏡の焦点面
The configuration of a single spectroscopic channel,ðQc þ 2Qi Þ- F/6 focus (dia. ~ 1m)

which is a combination of a filter and an MKID detector, ispresented in Fig. 1(b). At the top of the diagram is the submillimeter wave filter that we discussed in the previous paragraph. The signal line and the filters are made of NbTiN,
which typically has a gap frequency of %1.1 THz (Ref. 9)
and should therefore behave as a superconductor for a signalof 600–700 GHz. Now P3 is connected to the center of an
MKID which is open-ended on both sides. The MKID isitself a half wave resonator for a microwave readout tone in
the range of 6–7 GHz and is capacitively coupled on one ofits open ends to a through-line made of a NbTiN microstrip
line for probing the microwave response. For the prototype
device we have chosen Ta as the material for the top wire,
while the ground plane is the same NbTiN film continuingfrom the filter. Inferring from the measured Tc of the Ta filmof 4.4 K and assuming the BCS relation of 2D ¼ 3:5kB Tc ,・30 mテラヘルツ望遠鏡の焦点面- 同じF値の場合、焦点面面積は約3 m-10m望遠鏡で開発したクライオスタットを更にモジュール化

on top of a 7.5 nm-thicklayer asofindicatedNb, followed
by Reuse of AIP content is su
This article isseed
copyrighted
in the article.
electron-beam lithography and dry etching to define the 133.40.220.81 On: Wed
MKIDs. Finally, we deposit 85 nm of NbTiN and define thesignal line, the filters, the readout through line, and via-lessbonding pads to connect to the sample box. All wires have awidth of 3 lm, except at the feed point of the antenna, whereit decreases to 1 lm. The top NbTiN layer has a resistivity of
160 lX cm and a superconducting transition temperature ofTc ¼ 14.2 K.
The microwave losses of the transmission lines havebeen measured using a vector network analyzer while thechip was cooled to 350 mK using a 3He sorption cooler. All
30 Ta/SiNx /NbTiN microstrip MKIDs have a resonance frequency in the range of 6–7 GHz as designed and have anunloaded quality factor of Qi ¼ 1–5 '105 . We have also fabricated a single microwave resonator with a NbTiN wire tomeasure the microwave losses of the NbTiN/SiNx /NbTiN
microstrip line. This resonator showed an unloaded quality

まとめ
1. 南極10m望遠鏡搭載に向けた超伝導カメラの開発- Siレンズを用いた冷却光学系- 400GHz&850GHz : レンズ＋MKID array
1300GHz : ホーン+MKID array- 合計7モジュールで視野1度をカバー

2. 南極30m望遠鏡に向けて- MKID + on-chip ﬁlterを用いた面分光観測- 10m望遠鏡用に開発したカメラを更にモジュール化19