A Proposal of Long Slit Spectrograph for WSOUV

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					A Proposal of Long Slit Spectrograph for WSO/UV
Zhongwen Hu

Nanjing Institute of Astronomical Optics and Technology, National Astronomical Observatory of China, CAS National WSO/UV Implementation Committee of China 2006-June-28

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, Dr. Zhongwen Hu, Dr. Yi Chen, Ms. Jianing Wang, Mr. Lei Wang, director Optics FEA Electronics 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 soft X-ray projection lithograph

Dr. Zhongwen Hu
• 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

Soft x-ray beamline optics
First gas absorption spectrum with resolution 1000

 Movements in super high vaccum
3 Gratings could be exchanged Gratings rotated to scan wavelength Mirror rotated to compensate defocus

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

LSS References
• 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

New designs of LSS
Possible layouts with various resolutionwavelength 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 types Classical gratings VLS concave gratings Holographic gratings of the first generation Holographic gratings of the second generation

How to determine requirements of the LSS

?

Interactive procedure between science mission
requirements and technology capability and availability

Distance of slit from optical axis
Entrance: Width of slit Length of slit Coating of surfaces Far Ultraviolet (FUV) Near Ultraviolet (NUV) Refl. at 1150 Å; 1, /3 surfaces at 1216 Å; 1 , /3 surfaces at 3000 Å; 1 , /3 surfaces LSS optical layout: Dispersive element Curvature radii Light diameter Approximate size Spectral resolution  : FUV NUV Spectral resolution  for stars Space resolution Number of detectors

10  49.5 mm
Rectangular: 1  82 m 75  6.2 mm
Al + MgF2 1150  1775 Å 1750  3000 Å 60 %, / 21 % 82 %, / 55 % 87 %, / 66 % Modified Rowland-circle spectrograph with one reflection Concave grating R1 and R2 ~ 1 m 110 mm 1050 mm  350 mm 2000  3000 1500  3000 ~ 5000

Requirements baseline of current NIAOT design

Performance of the LongSlit Spectrograph (LSS)

Preliminary results

V. Terebizh, April 2005

0.40”
24

Optical configuration of LSS and Position
589 313
Unit of LSS mounting to the Optical Bench

Spectrometer case LSS

120

60

52.

7

VUV Spectrometer

UV Spectrometer

Modified Rowland configuration

+Z

LSS position in the instrument bay

450 462

LSS

+Y

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 resolutionwavelength pattern

3 layouts of NIAOT design
Layout 1a
Resolution Wavelength range(Å) Layout 1b Resolution Wavelength range(Å)

Detector 1
500 1450 5000 2000-2370

Detector 2
5800 2360-2710 Detector 2 2500 1150-1775 2000 1750-3050 5800 2700 -3100

1100-3500 1150-1655 Detector 1 500 1450

1100-3500 1150-1655

Layout 2 Resolution Wavelength range(Å)

Detector 1 500 11003500

Detector 2 2500 11501775 2000 17503050 5000 20002370

Detector 3 5800 23602710 5800 2700 3100

Resolution-Wavelength pattern
Layout 1a(5 gratings, 2 detctors)
6000

Two gratings cover 2360-3100 2000-2370

5000

4000

Resolution

3000

2000

1150-1655

1000

Very good image across 1100-3500
0 1000 1500 2000 2500 3000 3500

Wavelength

Resolution-Wavelength pattern
Layout 1b(4 gratings, 2 detctors)
3000

1150-1775

2000

One grating cover 1750-3050

Resolution

1150-1655

1000

Very good image across 1100-3500

0 1000 1500 2000 2500 3000 3500

Wavelength

Resolution-Wavelength pattern
Layout 2(6 gratings, 3 detctors)
6000

Two gratings cover 2360-3100 2000-2370

5000

4000

Resolution

3000

1150-1775 One grating cover 1750-3050

2000

1000

Very good image across 1100-3500
0 1000 1500 2000 2500 3000 3500

Wavelength

R.E. Gershberg’s proposal
with 3 detectors and 6 gratings
6000 5500 5000 4500 4000

1385-1575

1788-2032

Resolution

3500 3000 2500 2000 1500 1000 500 0 1000 1500 2000 2500 3000 3500

3 gratings cover 1200-3500 Image quality merely acceptable 1200-3400

Wavelength

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 1 Grating No. Wavelength range(Å) Incident Angle(deg) Diffraction Angle(deg) Detector size (mm^2) 42.1x6.5 1( Resolution 500) 1100 ~3500 4.176 -1.6363 Pixel size (um^2) 25x12 10( Resolution 1450) 1150-1655 6.625 0.814

Detector Tilt(deg)
Incident Length(mm) Detector Position(mm) Detector Radius

3.39
897.737 895.0517 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 size (mm^2) Detector 2 (alternative) 93.5 x6.5 Grating No. Wavelength range(Å) Incident Angle(deg) Diffraction Angle(deg) Detector Tilt(deg) Incident Length(mm) Detector Position(mm) Detector Radius(mm) 2 (Resolution 2500) 1150~1775 12 0.1253 8.3755 1035 1022 1037.832 25x12 3 (Resolution 2000) 1750~3050 10.725 -1.1456 Pixel size(um^2)

Layout parameters for detector 3
(2000 Å ~ 3500 Å, three gratings). R=5000
Detector size (mm^2)
76 x6.5 Grating No. Wavelength range(Å) Incident Angle(deg) Diffraction Angle(deg) Detector Tilt(deg) Incident Length(mm) Detector Position(mm) Detector Radius(mm) 4 (R= 5000) 2000~2370 21.486 8.532

Detector 3

Pixel size (um^2)
25x16 5 (R= 5800) 2360~2710 22.982 10.0267 0 1035 953.471 902.776 6 (R= 5800) 2700 ~3100 23 10.0445

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

LSS

VUV Spectrometer

UV Spectrometer

+Y

+Z

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 system) could be supplied by Britain?

• Electronics
– Digital process unit provided by Germany?

• other

Detectors available?
– Curved surface detector 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), Spectra-physics (U.S.), Carl Zeiss(Germany), Shimadzu(Japan), Bruno Touzet Doug Buerkle Klaus Heidemann Shinn Takada

Grating has a diameter 115mm. Gratings could be one of the following type. a. spherical gratings fabrcated by aspheric optics b. asperical grating available

Grating parameters
(Recording wavelength 310nm.)
Grating No. Tangential Radii 1 900 2 1023.278 3 1026.626 1005.007 -131.237 -1022.002 92.791 4 987.6782 990.4428 178.386 -692.005 2974.360 5 607.54 5 982.812 994.145 294.7175 -1043.679 2755.836 -780.765 6 982.336

Sagital Radii
Y of P1 Z of P1 Y of P2 Z of P2

895.917 1001.634
53.4717 -217.144 -976.88 244.804

994.602
387.576 -1043.92 2577.349 -827.065

897.115
0.1468

-1060.278 -1042.999 895.451

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 !


				
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