igrins immersion grating infrared spectrograph: current design sungho lee korea astronomy and space...

IGRINSIGRINSImmersion GRating INfrared Spectrograph:Immersion GRating INfrared Spectrograph:

Current DesignCurrent Design

Sungho LeeSungho LeeKorea Astronomy and Space Science Institute (Korea Astronomy and Space Science Institute (KASIKASI) / Univ. of Texas at Austin () / Univ. of Texas at Austin (UTUT))

In-Soo Yuk In-Soo Yuk (KASI),(KASI), Moo-Young Chun Moo-Young Chun (KASI),(KASI), Soojong Pak Soojong Pak (KHU),(KHU), Hanshin Lee Hanshin Lee (UT),(UT), Chan Park Chan Park (KASI),(KASI), Joseph Strubhar Joseph Strubhar (UT),(UT), Weisong Wang Weisong Wang (UT),(UT), Casey Deen Casey Deen (UT),(UT), Mic Michael Gully-Santiago hael Gully-Santiago (UT),(UT), Jared Rand Jared Rand (UT),(UT), Jung-Hoon Kim Jung-Hoon Kim (SET),(SET), Won-Kee Park Won-Kee Park (SN(SNU/KHU),U/KHU), Haingja Seo Haingja Seo (KHU),(KHU), Kang-Min Kim Kang-Min Kim (KASI),(KASI), Heeyoung Oh Heeyoung Oh (KASI),(KASI), Sang-On Le Sang-On Lee e (KASI),(KASI), Marc Rafal Marc Rafal (UT),(UT), Stuart Barnes Stuart Barnes (Univ. of Canterbury/UT),(Univ. of Canterbury/UT), John Goertz John Goertz (UT),(UT),

John Lacy John Lacy (UT),(UT), Tae-Soo Pyo Tae-Soo Pyo (Subaru),(Subaru), Daniel T. Jaffe Daniel T. Jaffe (UT)(UT)

IGRINS Design SNU 2010-08-26

Instrument TeamInstrument Team

UTUTKoreaKorea

KASIKASI KHU/SETKHU/SET

Project ManagementProject Management Dan Jaffe (PI),Dan Jaffe (PI),

Marc RafalMarc Rafal

Systems EngineeringSystems Engineering Sungho Lee,Sungho Lee,

Joe StrubharJoe Strubhar

OpticsOptics Hanshin Lee Hanshin Lee

GratingsGratings Weisong WangWeisong Wang

MechanicsMechanics

CryogenicsCryogenics

In-Soo Yuk (Co-PI),In-Soo Yuk (Co-PI),

Chan ParkChan Park

ElectronicsElectronics Moo-Young ChunMoo-Young Chun

SoftwareSoftware Soojong Pak,Soojong Pak,

Jung-Hoon KimJung-Hoon Kim

Calibration UnitCalibration Unit Kang-Min Kim,Kang-Min Kim,

Heeyoung OhHeeyoung Oh


IGRINSIGRINS High resolution IR spectrograph which can cover a broad High resolution IR spectrograph which can cover a broad

wavelength range in a single exposurewavelength range in a single exposure

IGRINS will be commissioned at the McDonald 2.7-m telescope, IGRINS will be commissioned at the McDonald 2.7-m telescope, and also designed to be compatible with 4-8 m telescopes.and also designed to be compatible with 4-8 m telescopes.

Spectral resolutionSpectral resolution R=40,000 (3.66 pixel sampling)R=40,000 (3.66 pixel sampling)

Wavelength coverageWavelength coverage H-band : 1.49~1.80 µm (25 orders)H-band : 1.49~1.80 µm (25 orders) K-band : 1.96~2.46 µm (22 orders)K-band : 1.96~2.46 µm (22 orders)

Slit dimensionSlit dimension Telescope 2.7-m 2.7-m McDonaldMcDonald 4-m4-m 8-m8-m

Slit WidthSlit Width 1” 0.68” 0.34”

Slit LengthSlit Length 15” 10” 5”


Design ConceptDesign Concept Cross-dispersed echelle spectrographCross-dispersed echelle spectrograph

Main disperser : silicon immersion grating (R3, 36.5 l/mm)Main disperser : silicon immersion grating (R3, 36.5 l/mm) Cross disperser : VPH gratings (H: 650 l/mm, K: 400 l/mm)Cross disperser : VPH gratings (H: 650 l/mm, K: 400 l/mm)

High sensitivityHigh sensitivity Silicon immersion gratingSilicon immersion grating VPH gratingsVPH gratings HAWAII-2RG (2048x2048) detectorsHAWAII-2RG (2048x2048) detectors

Compact (0.9 x 0.6 x 0.4 m) Compact (0.9 x 0.6 x 0.4 m) Silicon immersion gratingSilicon immersion grating VPH gratingsVPH gratings White pupil optical designWhite pupil optical design

Simple and reliable operationSimple and reliable operation No cold moving parts in the spectrographNo cold moving parts in the spectrograph Only switching mechanism for the calibration sourcesOnly switching mechanism for the calibration sources

Model of IGRINS on 2.7m


Optical Design LayoutOptical Design Layout

Collimated beam size = 25 mmCollimated beam size = 25 mm Slit size = 0.13 mm x 1.94 mmSlit size = 0.13 mm x 1.94 mm


H-Band Spectral FormatH-Band Spectral Format


K-Band Spectral FormatK-Band Spectral Format


Spectrograph Optical PerformanceSpectrograph Optical Performance

H-band K-band

Geometric spot diagram across the spectraGeometric spot diagram across the spectra Squares: 2 x 2 pixels (36 x 36 micron)Squares: 2 x 2 pixels (36 x 36 micron) Circles: Airy disk sizeCircles: Airy disk size Optical quality does not degrade spectral resolutionOptical quality does not degrade spectral resolution


Input Relay OpticsInput Relay Optics Convert a telescope f-ratio (f/9-f/16) to f/10Convert a telescope f-ratio (f/9-f/16) to f/10 Provide a cold stop to prevent thermal radiationProvide a cold stop to prevent thermal radiation Deliver 2 x 2 arcmin FOV to the slit-viewing/guiding cameraDeliver 2 x 2 arcmin FOV to the slit-viewing/guiding camera

Circle: Airy disk size • 1 arcsec seeing disk image through the input optics at the slit mirror• 4.4 arcsec per size

Left: Center of the slitMiddle: One edge of the slitRight: One corner of the 2 x 2 arcmin field


Slit-Viewing CameraSlit-Viewing Camera Target acquisition and slit monitoringTarget acquisition and slit monitoring Offset guiding in a 2 x 2 arcmin FOV at the 2.7-m telescopeOffset guiding in a 2 x 2 arcmin FOV at the 2.7-m telescope Use 1024 x 1024 clean area of an Engineering Grade H2RGUse 1024 x 1024 clean area of an Engineering Grade H2RG Ks-band filterKs-band filter

• 1 arcsec seeing disk image through the input optics and slit viewer • 4.4 arcsec per size

Left: Center of the slitMiddle: One edge of the slitRight: One corner of the 2 arcmin x 2 arcmin field


Immersion GratingImmersion Grating Outstanding capability of IGRINS in the compact design comes from the silicon immersion

gratings. The high refractive index (n=3.4) of silicon keep the high spectral resolution with a much smaller

beam size. Silicon lithography can make a very coarse grating which enables continuous spectral coverage.

max

(sin sin )

2 sin

2 tan

G

G

G

m n

n LR

nd

d


IGRINS Immersion GratingIGRINS Immersion Grating Silicon R3 grating (10 cm) Silicon R3 grating (10 cm)

Spectral ghost < 0.3% Spectral ghost < 0.3% (~5 nm periodic error)(~5 nm periodic error)

Spectral grass ~10Spectral grass ~10-5-5 (scattering at groove surfaces)(scattering at groove surfaces)

Will make another gratingWill make another grating Choose and cut into the shapeChoose and cut into the shape


VPH GratingsVPH Gratings Volume Phase Holographic grating Volume Phase Holographic grating Cross-dispersers in each H and K band spectrographCross-dispersers in each H and K band spectrograph Advantages of VPH gratings over conventional gratingsAdvantages of VPH gratings over conventional gratings

Higher efficiency by less scattersHigher efficiency by less scatters Enabling compact optical systems by transmission configurationEnabling compact optical systems by transmission configuration High durability and easy handlingHigh durability and easy handling

Has been used in optical and NIR (H-band) spectrographsHas been used in optical and NIR (H-band) spectrographs We have purchased H-VPHGs which show good performances.We have purchased H-VPHGs which show good performances.


IR VPH Grating TestIR VPH Grating Test Performance verificationPerformance verification K-band grating development in collaboration with KOSIK-band grating development in collaboration with KOSI Thermal cycling testsThermal cycling tests


Mechanics – CyrostatMechanics – Cyrostat Size of the cryostat : 900 x 600 x 400 mmSize of the cryostat : 900 x 600 x 400 mm Total mass : 210 kgTotal mass : 210 kg Compactness minimizes the flexure issueCompactness minimizes the flexure issue All access from the bottom of the cryostatAll access from the bottom of the cryostat Optical bench is mounted on the bottom plate and Optical bench is mounted on the bottom plate and

thermally isolated by G10 supportsthermally isolated by G10 supports

Input relay optics

Slit-viewing camera


Cyrostat – Structual AnalysisCyrostat – Structual Analysis

Mostly looking upward to the straMostly looking upward to the straight Cassegrain focusight Cassegrain focus

Deflection is < 10 um at the G10 Deflection is < 10 um at the G10 supports supports

Corrected out by focussing and Corrected out by focussing and guidingguiding


Mechanics – Camera BarrelsMechanics – Camera Barrels

(H-band, 130 K)(H-band, 130 K) Lens 1Lens 1 Lens 2Lens 2 Lens 3Lens 3 Lens 4Lens 4

MaterialMaterial CAF2CAF2 S-FTM16S-FTM16 INFRASILINFRASIL INFRASILINFRASIL

Thickness (mm)Thickness (mm) 55 7.57.5 11.511.5 8.58.5

Diameter (mm)Diameter (mm) 5454 5454 5454 6767


Mechanics – Camera BarrelsMechanics – Camera Barrels

Axial spring

Radial spring

Built in Baffle

Bent Holes

M3 screws with helicoil

Axial spring

Radial spring

3 Baffle Plates

Precision Pin

Radial Spring

Axial Spring

Camera is the most sensitive Camera is the most sensitive Design it first to minimize riskDesign it first to minimize risk 3+1 baffle vanes3+1 baffle vanes 3-point kinematic mount3-point kinematic mount Springs for thermal expansionSprings for thermal expansion


Mechanics – Detector MountsMechanics – Detector Mounts

Cryo ASIC Board

H2RG

Flex Cable

Cold Strap from H2RG

Cold Strap from ASIC board

Thermal insulation

Flex cable to the outside electronicsFlex cable to the outside electronics H2RG & ASIC thermally isolated from the optical H2RG & ASIC thermally isolated from the optical

benchbench


Mechanics – Telescope MountMechanics – Telescope Mount

4-point structure4-point structure Only translation on the FP Only translation on the FP Same mount for 2.7 m and GeminiSame mount for 2.7 m and Gemini


CryogenicsCryogenics

Operating temperatureOperating temperature Optical bench and optics : 130 KOptical bench and optics : 130 K Detectors : 77 KDetectors : 77 K

Temperature stability controlTemperature stability control Silicon immersion grating : ±0.06 KSilicon immersion grating : ±0.06 K Detector : ±0.1 KDetector : ±0.1 K Optical bench : ±1 KOptical bench : ±1 K

The temperature will be monitored The temperature will be monitored at least at six positions at least at six positions Cold head, optical bench, radiation Cold head, optical bench, radiation

shield, input optics, two spectrograph shield, input optics, two spectrograph camerascameras

2 rubber springs

Metal bellows

Vibration isolation designVibration isolation design


DetectorsDetectors

H & K spectrographH & K spectrograph

(Science grade)(Science grade)

Slit-viewing cameraSlit-viewing camera

(Engineering grade)(Engineering grade)

ROICROIC HAWAII-2RGHAWAII-2RG

Detector materialDetector material HgCdTeHgCdTe

Format (pixels)Format (pixels) 2048 x 20482048 x 2048

Pixel sizePixel size 18 18 mm

Cutoff wavelengthCutoff wavelength 2.5 2.5 mm

Quantum efficiencyQuantum efficiency > 80 %> 80 %

Read noise (CDS)Read noise (CDS) < 12 e-< 12 e-

Dark currentDark current < 0.01 e-/s/pixel< 0.01 e-/s/pixel

ControllerController SIDECAR ASICSIDECAR ASIC


Detector TestingDetector Testing

Collaboration with WIFIS at Univ. of TorontoCollaboration with WIFIS at Univ. of Toronto ROIC functional test is ongoingROIC functional test is ongoing Cryogenic EG detector test in this yearCryogenic EG detector test in this year

Test at KASITest at KASI Test dewar design Test dewar design Cryogenic test at KASI next yearCryogenic test at KASI next year


Electronics ArchitectureElectronics Architecture

IP based control system (each device has an IP address)IP based control system (each device has an IP address) Standard SW protocols and HW devicesStandard SW protocols and HW devices System can evolve as needed.System can evolve as needed.


Software ArchitectureSoftware Architecture

Standard observing scenariosStandard observing scenarios Software Requirements DocumentSoftware Requirements Document Software Specification DocumentSoftware Specification Document: working for each SW package: working for each SW package


Calibration UnitCalibration Unit Line Calibration : Line Calibration :

Th-Ar lamp or Uranium lamp Th-Ar lamp or Uranium lamp OH emission linesOH emission lines Telluric absorption linesTelluric absorption lines

Continuum Calibration : Continuum Calibration : Tungsten-halogen lampTungsten-halogen lamp

Compatible with f/8 ~ f/16 telescopesCompatible with f/8 ~ f/16 telescopes

Considering an absorption gas cell for future RV programsConsidering an absorption gas cell for future RV programs


Integration and TestIntegration and Test – Lab Setup and Handling Plan – Lab Setup and Handling Plan

Clean room, optical bench, interfaceClean room, optical bench, interface Multi-purpose cartMulti-purpose cart

Storage and transportationStorage and transportation Telescope installationTelescope installation


Overall Alignment ProcedureOverall Alignment Procedure[M1] Input-relay lens module

[M2] Slit-viewer lens module

[M3] H & K camera lens module

[M4] Calibration optics

[M5] Optical bench assembly

[Sb1] Input-relay optics

[Sb2] Slit-viewer optics

[Sb3] Spectrograph reflective optics

[Sb4] Slit-viewer system

[Sb5] Input+Slitviewer system

[Sb6] Spectrograph system

Module Alignments (Warm)

Warm Test

Cold Test

[S1] Instrument alignment

[S2] Telescope alignment

System Alignments (Cold)


Fabrication & Alignment PlanFabrication & Alignment PlanFabricate and test

H & K camera lenses

Correct design ofH & K camera barrels

FabricateH & K camera barrels

Assemble and alignH & K camera barrels

Fabricate and testdispersion part components

Correct design ofM2 mirror mount

Fabricatedispersion part mounts

Assemble and aligndispersion part

(compensator: M2 mirror)

Correct positions ofH & K cameras + detectors

Assemble and aligndispersion part + camera barrels + detectors

(compensator: detector assembly)


Future WorkFuture Work

Overall timelineOverall timeline PDR : 2009. 12PDR : 2009. 12 Camera CDR : 2010. 11Camera CDR : 2010. 11 Main CDR : 2011 (TBD)Main CDR : 2011 (TBD) Commissioning : 2012. 11 (TBD)Commissioning : 2012. 11 (TBD)

Tasks for the Camera CDRTasks for the Camera CDR Camera lens barrel designCamera lens barrel design Scattered light and ghost analysisScattered light and ghost analysis Revise engineering requirements: OCDD, FPRD, error budgetRevise engineering requirements: OCDD, FPRD, error budget Revise I/T plan, acceptance test plan, alignment planRevise I/T plan, acceptance test plan, alignment plan

igrins immersion grating infrared spectrograph: current design sungho lee korea astronomy and space...

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