System Design of Extreme Ultraviolet Three-Order Slitless Imaging Spectrometer for Solar Upper Transition Region

Wenjie Shen; Yangguang Xing; Yifan Huang; Jilong Peng; Shuwu Dai; Ying Wang; Chenglin Zhu; Lei Yan; Yue Liu; Lin Li

doi:10.3788/AOS231182

Acta Optica Sinica, Volume. 44, Issue 6, 0611001(2024)

System Design of Extreme Ultraviolet Three-Order Slitless Imaging Spectrometer for Solar Upper Transition Region

Wenjie Shen¹, Yangguang Xing^1、*, Yifan Huang^1、**, Jilong Peng², Shuwu Dai³, Ying Wang³, Chenglin Zhu³, Lei Yan⁴, Yue Liu^1、***, and Lin Li¹

Author Affiliations

¹School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China

²Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, China

³Beijing Institute of Astronautical Systems Engineering, Beijing 100094, China

⁴Beijing Institute of Spacecraft System Engineering, Beijing 100076, China

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Figures & Tables(18)

Fig. 1. New concept of three-order slitless spectral imaging. (a) Dispersion direction diagram of three-order slitless imaging spectrometer; (b) schematic of single-order subsystem of three-order slitless imaging spectrometer

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Fig. 2. Curve of solar atmospheric temperature changing with surface height^[9]

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Fig. 3. Schematic of aberration-corrected TULS grating^[23]

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Fig. 4. Paraxial optical model diagram of slitless imaging spectrometer in spatial imaging plane

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Fig. 5. Design flow process for slitless imaging spectrometer

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Fig. 6. Optical layouts of three-order slitless imaging spectrometer. (a) 3D model diagram; (b) optical layout of ±1 order subsystems; (c) optical layout of 0-order subsystem

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Fig. 7. Transmission of Si filter with 0.1 μm thickness

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Fig. 8. Reflectivity of Sc/Si multilayer

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Fig. 9. Surface sag map of secondary mirror array

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Fig. 10. RMS radius of defocused spot varying with 2D field. (a) -1 order; (b) 0 order; (c) +1 order

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$MTF of design system under different diffraction orders. (a) -1 order; (b) 0 order; (c) +1 order$

Fig. 11. MTF of design system under different diffraction orders. (a) -1 order; (b) 0 order; (c) +1 order

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Fig. 12. Geometric ensquared energy to evaluate system's spatial resolution. (a) -1 order; (b) 0 order; (c) +1 order

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Fig. 13. Spectral resolution verification for -1 order and +1 order. (a) -1 order; (b) +1 order

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Table 1. Technical specifications for three-order slitless imaging spectrometer

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Table 1. Technical specifications for three-order slitless imaging spectrometer

Performance parameter	Design value
Instrument bandpass /nm	46.0-47.0
Objective emission line /nm	Ne VII 46.52
Temperature of plasma /MK	0.5
Light-of-sight velocity /（km·s^-1）	≥50
FOV /［（′）×（′）］	24×24
Spectral dispersion /（nm·pixel^-1）	≤0.0078
Spectral resolution of inversion /nm	≤0.0078
Spatial plate scale /［（″）·pixel^-1］	≤1.0
Spatial resolution /（″）	≤2.0
Entrance aperture /mm	60
Pixel size of detectors /μm	12（2048 pixel×2048 pixel）
Optical volume /（mm×mm×mm）	≤1000×300×300

Table 2. Initial structural parameters of slitless imaging spectrometer
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Table 2. Initial structural parameters of slitless imaging spectrometer
Parameter Value
f /mm 3200
R_T /mm -1413.193
Δ /mm 80
r_A /mm 202.222
β 4.5
d₀ /mm^-1 2000
m -1，0，+1
R /mm 330.909
ρ /mm 330.909

Table 3. Specifications and optical element parameters for three-order slitless imaging spectrometer

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Table 3. Specifications and optical element parameters for three-order slitless imaging spectrometer

Design	Parameter	Value
Three-order slitless imaging spectrometer	Instrument bandpass /nm	46.0-47.0
	Objective emission line /nm	Ne VII 46.52
	Temperature of plasma /MK	0.5
	Light-of-sight velocity /（km·s^-1）	≥50
	FOV /［（′）×（′）］	24 × 24
	Spectral resolution /nm	0.0078
	Spatial resolution /（″）	1.547
	System focal length /mm	3200
	Entrance aperture /mm	60
	Pixel size of detectors /μm	12（2048 pixel×2048 pixel）
	Optical volume /（mm×mm×mm）	950×280×240
Telescope design	R_T /mm	-1343.265
	Conic	-1.439
	Δ_x，Δ_y /mm	-80，0（-1 order）
		0，80（0 order）
		80，0（+1 order）
Spectral imaging system design	Field stop size /（mm×mm）	5.2×5.2
	Groove spacing /mm^-1	2000
	Diffraction order	-1 order，0 order，and +1 order
Grating	r_A /mm	198.702
	β	4.575/4.623/4.724（-1，0，+1 order）
	i /（°）	6.243/5.672/4.384（-1，0，+1 order）
	R /mm	326.159
	ρ /mm	324.389
	Ruling area /（mm×mm）	30×30
Three independent detector design	Order	-1，0.1
Three independent detector design	Tilt angle of detectors /（°）	19.38，25.03，28.54

Table 4. Theoretically calculated spectral resolution of ±1 order
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Table 4. Theoretically calculated spectral resolution of ±1 order
m Spectral resolution /nm λ/Δλ Light-of-sight velocity /（km·s^-1）
-1 0.00622 7479.10 40.11
+1 0.00509 9139.49 32.82

Table 5. Tolerance limits of key components of system

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Table 5. Tolerance limits of key components of system

Component	Tolerance item	Single grating working in single order	Single grating working in three orders
Primary mirror	Surface irregularity（RMS）	λ/25（λ=632.8 nm）	λ/40（λ=632.8 nm）
	Conic	±0.003	±0.001
	Radius of curvature /mm	±0.8	±R/3000
	Microroughness（RMS）/nm	0.6	0.4
	Element decenter /μm	±25	±30
	Element tilt /（°）	±0.01	±0.01
TULS grating	Surface irregularity（RMS）	λ/30（λ=632.8 nm）	λ/40（λ=632.8 nm）
	Line density /（groove·mm^-1）	±1	±1
	Radius of curvature /mm	±0.12	±R/3000
	Microroughness（RMS）/nm	0.4	0.25
	Element decenter /μm	±10	±5
	Element tilt /（°）	±0.025	±0.010

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Wenjie Shen, Yangguang Xing, Yifan Huang, Jilong Peng, Shuwu Dai, Ying Wang, Chenglin Zhu, Lei Yan, Yue Liu, Lin Li. System Design of Extreme Ultraviolet Three-Order Slitless Imaging Spectrometer for Solar Upper Transition Region[J]. Acta Optica Sinica, 2024, 44(6): 0611001

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