A Proposal of Long Slit Spectrograph

for WSO/UV

Nanjing Institute of Astronomical Optics and Technology,National Astronomical Observatory of China, CAS

National WSO/UV Implementation Committee of China

2006-June-28

Zhongwen Hu

Contents

• Team Members Introduction• Requirements and assumption• layout overview of NIAOT LSS • Configurations and performance of LSS • Cooperation Expected• Quotation results of diffraction Gratings• Cross check results of the optics design• Schedule

NIAOT Introduction

• A unique research base in China, specialized in professional astronomical telescopes and instruments – 50 astronomical telescopes and instruments ;

30 exported to the USA, Spain, Japan and South Korea.

• Four main Laboratory– Mirror Technology – Astronomical Spectrum and High Resolution Imaging – Solar Instruments – New Technology Telescope

Team members introduction

• Prof. Yongtian Zhu, director

• Dr. Zhongwen Hu, Optics

• Dr. Yi Chen, FEA

• Ms. Jianing Wang, Electronics

• Mr. Lei Wang, Precision mechanics

Prof. Yongtian Zhu

• Vice Director of NIAOT

• Experience– the Coude Echelle Spectrograph for Chinese

2.16-meter astronomical Telescope– Spectrographs for LAMOST project – Proposed a novel two-mirror system for the so

ft X-ray projection lithograph

• Soft X-ray beamline construction and calibration of a varied angle spherical grating monochromator

(12-120nm)• Echelle spectrograph (200-500nm)• Polychromator ( 31channels) (UV-Visible).

• High precision measurements of grating groove density for VLS concave diffraction gratings (Uncertainty 1x10-5). Especially small curvature radius gratings.

• Expression of groove density (N) and groove function (n) applicable for any gratings

Dr. Zhongwen Hu

Soft x-ray beamline optics

Movements in super high vaccum 3 Gratings could be exchangedGratings rotated to scan wavelengthMirror rotated to compensate defocus

First gas absorption spectrum with resolution 1000

NIAOT contribution to LSS

• Under direction of WIC working group of China• NIAOT responsibilities

– Participate system requirement definition– Design of LSS– Construction of prototype, flight model and test system– Complete instrument level test in China

• Some crosscheck of LSS test in Ukraine ?

– Participate Integration with rest of WSO– Develop Calibration and data reduction methodology

• THE ROWLAND MULTICHANNEL LONG SLIT SPECTROGRAPH FOR THE WSO/UV MISSION ----- R.E. Gershberg ,et.al

• HIRDES Phase A Study -----Dr. Schwarz & Project Team

• Performance of the Long-Slit Spectrograph (LSS) ----V. Terebizh

•

LSS References

New designs of LSS

Possible layouts with various resolution-

wavelength pattern

Optimized space and spectrum resolution with

extended wavelength coverage

Expect better image quality for every point on

slit

Use of special gratings

Diffraction grating typesClassical gratingsVLS concave gratingsHolographic gratings of

the first generationHolographic gratings of

the second generation

How to determine

requirements of the LSS ?

Interactive procedure between science mission

requirements and technology capability and

availability

Performance of the Long-Slit Spectrograph (LSS)

Preliminary results

V. Terebizh, April 2005

Distance of slit from optical axis 10 49.5 mm

Entrance ： Width of slit Length of slit

Rectangular: 1 82 m

75 6.2 mm

Coating of surfaces Al + MgF2

Far Ultraviolet (FUV) Near Ultraviolet (NUV)

1150 1775 Å1750 3000 Å

Refl. at 1150 Å ； 1, /3 surfacesat 1216 Å ； 1 , /3 surfacesat 3000 Å ； 1 , /3 surfaces

60 %, / 21 %82 %, / 55 %87 %, / 66 %

LSS optical layout ： Modified Rowland-circle spectrograph with one reflection

Dispersive element Curvature radii Light diameter

Concave gratingR1 and R2 ~ 1 m

110 mm

Approximate size 1050 mm 350 mm

Spectral resolution : FUV NUV

2000 30001500 3000

Spectral resolution for stars ~ 5000

Space resolution 0.40”

Number of detectors 2 4

Requirements

baseline of current

NIAOT design

Optical configuration of LSS and Position

313589

52.7

120

450

Spectrometer case LSS

+Z

+Y

60

462

Unit of LSS mounting to the Optical Bench

UV SpectrometerVUV Spectrometer

LSS

Modified Rowland configuration LSS position in the

instrument bay

A layout by R.E. Gershberg et.al(3 detectors and 6 gratings)

Overview of our layout

Three possible layouts are considered:

Layout 1a, Layout 1b, layout2

Each layout is shown with its resolution-wavelength pattern

3 layouts of NIAOT designLayout 1a Detector 1 Detector 2

Resolution 500 1450 5000 5800 5800

Wavelength range(Å)

1100-3500 1150-1655 2000-2370 2360-2710 2700 -3100

Layout 1b Detector 1 Detector 2

Resolution 500 1450 2500 2000

Wavelength range(Å)

1100-3500 1150-1655 1150-1775 1750-3050

Layout 2 Detector 1 Detector 2 Detector 3

Resolution 500 2500 2000 5000 5800 5800

Wavelength range(Å)

1100-3500

1150-1775

1750-3050

2000-2370

2360-2710

2700 -3100

Resolution-Wavelength pattern Layout 1a(5 gratings, 2 detctors)

1000 1500 2000 2500 3000 35000

1000

2000

3000

4000

5000

6000

Re

solu

tion

Wavelength

Very good image across 1100-3500

Two gratings cover 2360-3100

1150-1655

2000-2370

Resolution-Wavelength patternLayout 1b(4 gratings, 2 detctors)

1000 1500 2000 2500 3000 35000

1000

2000

3000

One grating cover 1750-3050

Res

olut

ion

Wavelength

Very good image across 1100-3500

1150-1775

1150-1655

Resolution-Wavelength pattern Layout 2(6 gratings, 3 detctors)

1000 1500 2000 2500 3000 35000

1000

2000

3000

4000

5000

6000

One grating cover 1750-3050Re

solu

tion

Wavelength

Very good image across 1100-3500

Two gratings cover 2360-3100

1150-1775

2000-2370

R.E. Gershberg’s proposal with 3 detectors and 6 gratings

1000 1500 2000 2500 3000 35000

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

Re

solu

tion

Wavelength

Image quality merely acceptable 1200-3400

3 gratings cover 1200-3500

1385-1575 1788-2032

Layout 1a(2 detectors and 5 gratings) Grating

Detector

Configurations and performance

Optical parameters

Image quality

Resolution achieved

Layout parameters for detector 1.R=500

Detector 1Detector size (mm^2)

Pixel size(um^2)

42.1x6.5 25x12

Grating No. 1( Resolution 500) 10( Resolution 1450)

Wavelength range(Å) 1100 ~3500 1150-1655

Incident Angle(deg) 4.176 6.625

Diffraction Angle(deg) -1.6363 0.814

Detector Tilt(deg) 3.39

Incident Length(mm) 897.737

Detector Position(mm) 895.0517

Detector Radius Infinite

Spot diagram on detector 1 with grating 1. Left is the images for different points on 6.2 mm slit within the related wavelength. Right is RMS spot radius which shows good space and spectrum resolution for varied slit positions.

Resolution test

Slit width is 82 microns along spectrum direction space resolution 32 microns along the entrance slit. Gaussian distribution of image on slit with FWHM equals the slit width is assumed.

Layout parameters for detector 2 (1150 Å ~ 3050 Å, two gratings). R=2500

Detector 2 (alternative)

Detector size (mm^2) Pixel size(um^2)

93.5 x6.5 25x12

Grating No. 2 (Resolution 2500) 3 (Resolution 2000)

Wavelength range(Å) 1150~1775 1750~3050

Incident Angle(deg) 12 10.725

Diffraction Angle(deg) 0.1253 -1.1456

Detector Tilt(deg) 8.3755

Incident Length(mm) 1035

Detector Position(mm)

1022

Detector Radius(mm) 1037.832

Layout parameters for detector 3(2000 Å ~ 3500 Å, three gratings). R=5000

Detector 3

Detector size(mm^2)

Pixel size (um^2)

76 x6.5 25x16

Grating No.4

(R= 5000)5

(R= 5800)6

(R= 5800)

Wavelength range(Å) 2000~2370 2360~2710 2700 ~3100

Incident Angle(deg) 21.486 22.982 23

Diffraction Angle(deg)

8.532 10.0267 10.0445

Detector Tilt(deg) 0

Incident Length(mm) 1035

Detector Position(mm)

953.471

Detector Radius(mm) 902.776

Mechanical interface problem

+Z

+YUV SpectrometerVUV Spectrometer

LSS

1.Gratings enter into spaces of UV and VUV chamber--- Space resolution and detector pixel dimension

2.How many detectors mechanically available---with or without folding mirrors?---Interference with FC ?

International cooperation expected

• Detectors– The detector unit (with the High Voltage syste

m) could be supplied by Britain?

• Electronics– Digital process unit provided by Germany?

• other

Detectors available?

– Curved surfacedetector surface could be a flat plane

– Rectangular pixel Square pixel

degraded space resolution,two point sampling

– Maximum available pixels– Mechanical dimensions

Possible vendors of gratings

• Jobin Yvon (France), Bruno Touzet • Spectra-physics (U.S.), Doug Buerkle • Carl Zeiss(Germany), Klaus Heidemann • Shimadzu(Japan), Shinn Takada

Grating has a diameter 115mm. Gratings could be one of the following type.

a. spherical gratings fabrcated by aspheric opticsb. asperical grating available

Grating parameters(Recording wavelength 310nm.)

Grating No.1 2

3 4 56

Tangential Radii

900 1023.2781026.626 987.6782 982.812

982.336

Sagital Radii 895.917 1001.634 1005.007 990.4428 994.145 994.602

Y of P1-

53.4717-217.144

-131.237 178.386 294.7175387.576

Z of P1-

897.115-976.88

-1022.002 -692.005 -1043.679-1043.92

Y of P2 0.1468 244.80492.791 2974.360

52755.836

2577.349

Z of P2-

895.451-1042.999

-1060.278 607.54 -780.765-827.065

Gratings, Reply from Jobin Yvon (France),

– They can make our gratings on a custom substrate• difficult for them to fabricate the toroidal substrate

close to a sphere

– They made their own calculations use the same layout parameters with modified recording wavelength

Comparison (110nm~350nm resolution 500)

---by Jobin Yvon

NIAOT 310nm recording wavelength

Jobin Yvon with a different wavelength

Grating 1 (resolution 500)

Grating 10 (resolution 1450)

Summary of NIAOT design (1)

The incident, the diffracted angles and the positions of

detectors could be tuned to meet the space mechanically

available for LSS

Very good image quality with extended wavelength range

or increased resolution through points along the entrance slit.

Show the possibility to integrates some merits of several

previous designs.

Summary of NIAOT design (2)

For resolution 500 on detector 1

Very good image quality is obtained across wavelength

interval 1100 Å ~ 3500 Å through points on the slit.

No auxiliary reflecting mirror needed in principle.

─It depends on mechanical space available for LSS

Summary of NIAOT design (3)

For resolution ~2500, detector 2

the wavelength range is covered by two gratings like Willem

Wamsteker’s proposal,

yet it has the image quality similar to that described in R.E.

Gershberg’s four gratings mode or double gratings mode with

resolution 1500.

resolution ~5000 on detector 3

Notes

• Optical designs show improvements of the LSS performance.

• Yet it is not the finalized form considering the uncertainties in detectors and science mission requirements.

• System requirements concerning wavelength intervals and their resolution should be to optimized and balanced for newly claimed scientific mission

Schedule

• 2006.02-2007.03: Phase 0+A: Functional Requirements. Feasibility study. Initialization of procurement of component.

• 2006.12-2007.11: Phase B: Requirement specifications, Engineering environment set-up and preliminary design.

• 2007.11-2008.09: Phase C: Detailed design.

• 2008.09~2009.09: Phase D: Production of Flight Model. Ground qualification testing.

• 2009.09~2010.03: Assembling, Integration, and Verification, with the spacecraft.

• 2010.03~2010.09: Pre-launch testing

• 2010.10: Launch

Thank you !