WINERED : Realizing Hires modes (R=80,000)
with mosaicked high efficiency high-blazed echelle gratings
Shogo Otsubo1, Yuji Ikeda1,2, Naoto Kobayashi3,1, Sohei Kondo1, Satoshi Hamano1, Hiroaki Sameshima1, Kei Fukue1, Ayaka Watase1

Tomohiro Yoshikawa4, Kenshi Nakanishi1, Keiichi Takenaka1, Taichi Murai1 , Kyoko Sakamoto1, Chikako Yasui5,1, Noriyuki Matsunaga3,1 and Hideyo Kawakita1
1Laboratory of Infrared High-resolution spectroscopy in Kyoto Sangyo university, 2Photocoding, 3The Uniersity of Tokyo, 4Edechs, 5National Astronomical Observatory of Japan

WINERED is a PI-type NIR high-resolution spectrograph which realizes both wide coverage and high sensitivity. The Wide mode of WINERED covers z, Y, J-bands in a single
exposure with R=28,000 and has been commissioned since 2013. Recently we built alternative observing channels “Hires-Y mode” and “Hires-J mode” providing R=80,000.
It employs a mosaicked grating consisting of two high-blazed echelle gratings (HBGs). The HBGs are designed to be with a groove pitch of 90.38μm, a blaze angle of 79.32deg, andan apex angle of 88deg, and then they were custom-made by CANON Inc. We also designed the grating holder for the precious alignment of two HBGs, which has the adjustingmechanism with sub-μm resolution using a small ruby ball and adjusting bolts made of invar. The extremely low CTE material (< 2.0 × 10−8 at 23℃) “cordierite CO-220 (KyoceraCorporation)” is chosen as the material of the grating holder to reduce the alignment error by the thermal expansions. As a result, we achieved an alignment with the parallelismof < 1.0 arcsec and the stability of <0.1 arcsec under the condition of ⊿T = 5K for 25 hours. Finally, we evaluated the total optical performances of the assembled Hires-modes.
The measured throughput and spectral resolution are ~42% and R ~78,000, which a most meet the specification.

2.OPTICAL DESIGN

1.INTRODUCTION

2.1 Optical Layout

NIR high-resolution spectrograph, WINERED●”No Cold Stop”- Only camera system & IR array are cooled- Ambient BG Radiation is reduced to 0.05e-/pix/sec●“Wide Spectral Coverage”- Δλ/λ ~ 1/6 realized with a large
format array (2K×2K) andX-disperser echelle spectrograph●“High Sensitivity”- Total throughout of optics: >60%
- High QE array: >80%
- Low noise electronics systems(σr=5.3e-/pix for NDR=32)

Wavelength Coverage
Maximum Spectral Resolution
Slit Width
Slit Length
Total Throughput
VolumeOperation Temperature

The spectral resolution & coverageof various IR high-resolution spectrographs

2.2 Echellograms and Spotdiagrams
Hires-Y mode

Hires-J mode

Wide mode++
Hires-Y mode
Hires-J mode
0.90-1.35μm
0.95-1.11μm
1.14-1.35μm
28,000 (2pix sampling)
80,000 (2pix sampling)100μm (0.54”)+, 200μm, 400μm
3.12mm (17”)+> 50%~ 32%~ 42%
1750mm(L) × 1070mm(W) × 500mm(H)270-300K (except for camera lens and IR array)

Box sizes are 2pix×2pixof the array (1pix = 18μm)

the 3.58m telescope and f/11
Specification of WINERED + mounted++onsee
a poster presentation: P02

4.VERIFICATION OF HIRES MODES

3.HIGH-BLAZED ECHELLE GRATING・WINERED employs “high-blazed echelle grating (HBG)” for Hires-modes
・HBG produces an extremely high dispersion spectrumby high-blaze angle (θB > 75deg)・For WINERED, two HBGs are mosaicked

4.1 Spectral Coverage
1.71~2.37pix(designed: 1.64~2.58pix)(due to the limitation of the physical size for fabrication)

3.1 Design and Fabrication
Design and Production results
Item
Designed
Physical Size
200mm × 60mm × 59.4mm
Orthogonality of grooves*< 1μm
Blaze Angle
Apex Angle
Groove Pitch
Random Pitch Error
Surface Irregularity
Rowland Ghost
Diffraction Efficiency**

HBG #A

79.32deg (R5.3)
88deg
90.38μm< 8nm (rms)< 150nm (PV)< 30nm (rms)< 0.1%> 70%

Hires-JHires-Y

HBG #A

HBG #B

0.7μm

0.5μm

87.95deg

87.95deg

4.9nm
54.1nm
5.6nm< 0.01%
68.6%

4.9nm
45.4nm6.0nm< 0.01%
68.8%

Hires-J

Hires-Y

Halogen Lamp

Th-Ar Lamp image

4.2 Spectral Resolution
Estimated from measured dispersion (R~78,000)

Average R~68,000
Degraded due tothe tilting of IR Array

Unavoidable degradation by rotated slit-images,
due to a large γ-angle (γ=6deg) of HBG* measured from the reference surface produced on the side face** average between TE and TM waves

HBG #B4.3 Total Throughput
10.9

Throughput

0.8

Wavefront maps of diffracted lights of m=201 (@633nm)

3.2 Mosaicking Mechanism

Completed HBG (#A)

Total reflectivity of telescope
Transmission of telluric atmosphere

0.7
0.6
0.5
0.4

Total throughput of Hires-J mode ~42%
(Including array QE)

0.3
0.2
0.1

T = 25℃

25 hours

T = 30℃

1.15

1.20

4.4 Preliminary Results

1.25

1.30

Wavelength (μm)

Telluric lines

Parallelism : 1.0”
Designed grating holder

Parallelism : 1.0”
Stability of alignmentof two mosaicked HBGs

CygOB2 No.12 “C2(0,0) Phillips band”
Hires-J mode : R=70,000

α Boo (K1.5Ⅲ)
28,0001.35