Transcript Wide FOV Off-Axis Telescope with Fabry

Tandem Fabry-Perot Spectrometer
SQUEAN: Spectrometer for QUasar in EArly uNiverse
Presented
at
The 2nd Survey Science Group Workshop, High1 Resort
on
2012 Feb 14
by
Soojong Pak (Kyung Hee University)
Classification of
Spectrometers
Types of Dispersing Elements
Mechanism
Type
refraction
Prism Spec.
diffraction,
interference
Grating Spec.
reflection,
interference
Image
Slit
(1D)
Fourier Transform Spec. Imaging
(2D)
Fabry-Perot Spec.
Slit Sp. vs. Imaging Sp.
Imaging Spectrometer
Slit Spectrometer

Top View
Spatial
L
d
Side View
Spec
tr
W
al
DATA Format
Imaging Spectrometer
Slit Spectrometer
io
ct
n
SpectralDirection
Direction
Spatial
ire
lD
Spectral Direction
tra
ec
Spatial Direction
Direction
Spatial
Sp
Spatial Direction
Spatial
Direction
Other Kinds of Imaging Spectrometer:
Integral Field Unit
Other Kinds of Imaging Spectrometer:
Multi-Object Spectrometer
What is
Fabry-Perot Spectrometer?
Fabry-Perot Parameters
Path Difference 2 d o cos   m o
Finesse

d
 R
F 
1 R
m=1
Instrument Profile
I(, ,d , ) 
I (
T
1 R
)2
4R
2 d cos 
2
1
sin (
)
2

(1  R )
2
3 ….
Basic Etalon Equations
•
•
Conventions
–
–
𝑅 = 𝑚𝐹 : Spectral Resolution
We assumed that the incident angle is zero, 𝜃 = 0, and the mirror space is in vacuum, 𝑛 = 1.
–
It is convenient to use wave numbers, 𝜆 = .
–
–
–
–
–
𝑑𝜆,𝑚 : mirror distance for 𝜆 at order m
Δ𝜆𝐹𝑆𝑅 : Free Spectral Range in units of wave number
Δ𝑑𝐹𝑆𝑅,𝑚 : Corresponding mirror distance for FSR at m
Δ𝜆𝐹𝑊𝐻𝑀 : Full Width at Half Maximum of the instrument profile in units of wavelength
Δ𝑑𝐹𝑊𝐻𝑀 : Corresponding mirror distance for Δ𝜆𝐹𝑊𝐻𝑀
1
𝜆
Etalon Equations
2𝑑𝜆,𝑚 = 𝑚𝜆
2𝑑𝜆,𝑚 𝜆 = 𝑚
Δ𝜆𝐹𝑆𝑅 = 𝜆𝑚+1 − 𝜆𝑚 =
Δ𝑑𝐹𝑆𝑅,𝑚 =
=
1
2𝜆𝑚
𝑚
2𝜆𝑚+1
−
1
𝜆
1
= =
2𝑑 𝑚 𝑚𝜆
𝑚
2 𝜆𝑚
=
𝑚
1
1
𝑚
1
−
=
−1
2 𝜆𝑚 − Δ𝜆𝐹𝑆𝑅 𝜆𝑚
2 𝜆𝑚 1 − 1
𝑚
𝑚
1
1
𝜆𝑚 𝑚
1
=
=
=𝑑
𝑚−1
2 𝑚−1
𝑚−1
2Δ𝜆𝐹𝑆𝑅 𝑚 − 1
Δ𝜆𝐹𝑊𝐻𝑀 =
𝜆
𝜆
=
𝑅 𝑚𝐹
Δ𝑑𝐹𝑊𝐻𝑀 =
𝑚
𝜆
Δ𝜆
=
2 𝐹𝑊𝐻𝑀 2𝐹
Simulated Spectra
Δ𝜆𝐹𝑆𝑅 = 𝜆𝑚+1 − 𝜆𝑚
1
𝜆
1
=
= =
2𝑑 𝑚 𝑚𝜆
1.0
0.9
m=7
m=8
m=9
m=10
m=11
m=12
m=13
0.8
Relative Intensity
0.7
FSR
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.1000
10 um
0.1200
0.1400
0.1600
1/wavelength [1/um]
0.1800
0.2000
5 um
Simulated Spectra
Order Sorting Filter
1.0
0.9
0.8
Relative Intensity
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.1000
10 um
0.1200
0.1400
0.1600
1/wavelength [1/um]
0.1800
0.2000
5 um
Simulated Spectra
1.0
0.9
0.8
Relative Intensity
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.1000
10 um
0.1200
0.1400
0.1600
1/wavelength [1/um]
0.1800
0.2000
5 um
Order Sorting Method
of Tandem Fabry-Perot
Telescope
Collimator
Camera Lens
Detector
FP-A FP-B
(m=20) (m=250)
Disadvantage of FP
io
ct
Takes Long Time for Wide Spectral Band
n
SpectralDirection
Direction
Spatial
ire
lD
Spectral Direction
tra
ec
Spatial Direction
Direction
Spatial
Sp
Spatial Direction
Spatial
Direction
Advantage of FP
io
ct
n
SpectralDirection
Direction
Spatial
ire
lD
Spectral Direction
tra
ec
Spatial Direction
Direction
Spatial
Sp
Spatial Direction
Spatial
Direction
Takes Many Targets for Short Spectral Band
Suggested Fabry-Perot Spectrometer
Specifications
• Target Emission Lines at Optical Bands
– [OII] 372.7nm
– H 486.1nm
– [O III] 495.9 500.7nm
– H 656.2 nm
– [SII] 671.6 673.1 nm
• Spectral Resolutions
– The spectral resolution R = Finesse X m,
where Finesses comes from the FP mirrors reflectivity and the order of interference, m,
from the mirrors distance.
– If Finesse=40 and m=50-250, we can expect that R
• FOV (in case we use CQUEAN CCD)
– 13 um 1024 X 1024
– Total FOV 5 X 5 arcmin with 0.27 arcsec/pixel
= 2000 – 10000
Sciences (1/2)
• Emission Lines of Star Forming Regions in the Galaxy (Soojong Pak)
• Emission Lines of Star Forming Regions in the nearby galaxies (Luis
Ho suggested)
• Emission Lines of Merging AGNs (Julia Comerford suggested)
– Ref. Comerford et al. 2012, ApJ, 753, 42, Kpc-Scale Spatial Offsets in DoublePeaked Narrow-Line AGN. I
– Ref. Liu et al. 2011, ApJ, 737, 101, AGN Pairs from the SDSS. I.
• Narrow Emission Line Survey of Galaxies at z=1.
– H_beta 486nm, [OII] 372.7nm
– Ref. Glazebrook et al. 2004, AJ, 128, 2652, Cosmic Star Formation History to
z=1 from Narrow Emission Line Selected Tunable Filter Survey
Sciences (2/2)
• Dark Matter in Globular Clusters (Karl Gebhardt)
– 1000 Stellar velocities at the edges of the visible clusters in order to constrain the
dark matter distributions.
– R=10000 for velocity accuracy of 1 km/s
– m_R = 20 – 21 mag
• Chemical Composition Studies in Globular Cluster (Chris Sneden)
– a search for (the rare) Li-rich giant stars. The Li I resonance line is at 6708A
– characterizing Na variations in clusters. One could choose Na D lines, but
probably I would be happier with one of the 5680A doublet lines.
– searching for Ba abundance variations. Probably the 6496A or 6141A lines are
best.
– finding out the level of metallicity variations as a function of evolutionary
state. One could use one of the Ca IR triplet lines, for example.
McDonald Observatory
Otto Struve 2.1m telescope
2011-02-08
2011 IR Workshop
CQUEAN at 2.1m telescope
Science CCD
Filter Wheel
Control PC
Guide CCD
Motor for guide
CCD field rotator
2011-02-08
Guide CCD field
2011 IR Workshop
rotator
Science CCD Camera
(Andor iKon-M 934 BR-DD)
CCD
E2V Deep Depletion Chip
Pixels
1024 x 1024, 13μm
Readout
Speed
QE
Fringe
RD Noise
(Measured)
2011-02-08
2011 IR Workshop
2.5 MHz (0.4 sec)
1 MHz (1 sec)
50 kHz (20 sec)
Better than 25% at 1 μm
None
8.1 electrons/pixel
Possible Designs of Tandem Fabry-Perot
Serial Configuration of 2 etalons
FP-A FP-B
(m=20) (m=250)
Integrated Configuration of 3 mirrors
Etalon Specifications for Tandem Fabry-Perot
• Basic Specifications
– We use two etalons for high spectral resolution (ET-H) and low spectral resolution
(ET-L).
– The ET-L will sort the overlapped orders of ET-H.
– We also need broad band filters for the overlapped orders of ET-L.
– The mirror sets and housing of ET-H and ET-L are identical. The only difference is
the mirror distances.
• Etalon Specs
Etalon Finesse
𝜆𝑜 [nm]
m
R
d [nm]
𝜆𝐹𝑆𝑅
𝑑𝐹𝑆𝑅
𝜆𝐹𝑊𝐻𝑀 𝑑𝐹𝑊𝐻𝑀
ET-H
15
650
250
3750
81,250
2.60
325
0.17
21.7
ET-L
15
650
20
300
6,500
32.5
325
2.17
21.7
ET-H
40
650
250 10000
81,250
2.60
325
0.065
8.1
ET-L
40
650
6,500
32.5
325
0.813
8.1
20
800
Fore-Optics Design
• We need collimator
units and camera units
• before and after the Fabry-Perot.
Telescope
Collimator
Camera Lens
Detector
FP-A
FP-B
(m=150) (m=10)
Fore-Optics Design with Traditional Lens System
Example from CQUEAN Focal Reducer
Fore-Optics Design with Off-Axis Mirrors
• We can apply the off-axis mirror design of Dr. Seunghyuk Chang.
Eccentric section of an on-axis
parent system
The mirrors of a confocal system do not need to have a
common axis for a perfect image at the system focus
Re-imaging Optics for KASINICS
(cf. Offner System)
Schwartzschild-Chang Type Telescope
- from "Inverse Cassegrain" ellipsoid
paraboloid
off-axis (Schwartzschild-Chang Type)
on-axis
D=50mm, F/D=2 et al. 2011
(Schwartzschild Type)
(Kim, Pak, Chang et al. 2010)
Off-Axis Design for SQUEAN (by Chang)
Off-Axis Design for SQUEAN (by Chang)
(x,y)
Spot Diagrams
13um
Project Roadmap and Required Resources
GS Labor
[year]
Work Definition
Cost
[M KRW]
Etalon Development
3
60
Fore-Optics
(Off-Axis Mirrors or Lens)
2
30
Telescope Interface and Structure
0.5
10
Instrument Operation Software
0.5
Data Reduction Software
1
Telescope Installation and
Commissioning
0.5
30
7.5
130
TOTAL
Comments
Karl Gebhardt
Cost includes HW and Travel.
Appendix
Fabry-Perot Etalon Vendors
• Bristol Instruments
– They make the replacement FP mirrors for OLD Burleigh RC series.
– The basic price for one set of mirrors starts from $8,000.
– The man in the company recommends www.lightmachinery.com for custommade etalons.
• LightMachinery.com
Etalon
• LightMachinery.com
– They make customized Etalon mirrors.
– Piezo Tunable Etalons with clear aperture of 4 mm.
– Ian Miller, Director of R&D, gives very kind detailed technical supports.
PZT Tunable Etalon Housing
• ThorLabs.com
–
–
–
–
Scanning Fabry-Perot Interferometer: SA210-5B
• 535-820 nm, 10 GHz FSR
• $2,533
• This is for laser, but we can use this for scanning test.
PZT Drives & Actuator: PE4
• Micrometer Travel Range = 4mm with 1 um resolution
• PZT Travel Range = 15 um with 10 nm resolution
• 3 X $479.60 / unit
Open-Loop PZT Controllers: MDT693A
• 3 Channel
• $1,580
Piezoelectric Actuators
• Open Loop Piezo Actuator, 17um/150V: AE0505D16F, $153
• Full Bridge Strain Gauge Piezo Actuators, AE0505D16F: PZS001, $175
• Strain Gauge Amplification Circuit, AMP002, $161
• www.PhysikInstrumente.com
Coefficient of Thermal Expansion
• Fused Silica
– CTE = 0.55 ppm/K
• Invar
– CTE = 0-2 ppm/K
• Piezo Material
– CTE = 6E-3/K
http://www.piceramic.com/datasheet/Piezo_Material_Datasheet_Cofefficients_Te
mperature_Measurements.pdf