Binxun Ye and Binhua Li

1

• Binxun Ye and Binhua Li

2
The Project

• Large
• Sky Area
• Multi-Object
• Fiber Spectroscopic
• Telescope
• --LAMOST--

• Scientific objectives
• Extra-galactic Spectroscopic Survey
• --Large scale structure of universe
• Stellar Spectroscopic Survey
• --Structure of the Galaxy
• Cross Identification of Multi-
• wavelength Survey

3
The Project

• Technical Features
• Aperture gt4M, w/ 80 light concentrated in
  2".0, f/5,
• FoV5, 4000 Fibers
• --down to 20.5m, 2X107 Galaxies 108 Stellar
  Objects in three years
• Sky Coverage
• -1090
• --24,000 Sq. degree
• Spectral Coverage
• 390900 nm
• w/ Resolution 1 nm

• Schedule,etc.
• Schedule 7 yrs (19972004, delayed)
• Expected first
• light 2007
• Budget 235 M
• Site NAOC
• Xinglong Station
• 11734.5E
• 402336"N

4
The Telescope
5
The Spectrograph

• Overview
• Low Resolution Spectrograph
• --R1000
• --Limiting Magnitude 20m.5
• w/1h.5 exp.
• --?fiber320?m,
• 250 fibers/spectrograph
• --Gratings 700g/mm f. blue wing,
• 470g/mm f. red wing
• both blazed at 1080
• Medium Resolution Spectrograph
• High Resolution Spectrograph

Confirguration
Fiber positioning
Setup
6
The Camera System

• Overview
• 16 Spectrographs work for
• 4000 fibers
• 1 Blue 1 Red Camera
• f. each Spectrograph
• --32 in total cameras
• 250 object spectra from
• Each Camera
• --32 Large format CCDs
• --Half of them have to be
• Thinned Back-illumd
• Each Camera have to be
• positioned in middle of a
• Schmidt-type configuration

Fiber image over CCD pixels
96µm
96µm
dl0.5
nm
LRS
96µm
96µm
48µm
dl0.25
nm
HRS
7
The Camera System

• Design Parameters
• Spectral Coverage 390nm900nm
• Resolution 9 Å Dispersion 80Å/mm
• 250 Spectra per Frame, Each 112?m High
• Expos. 3 30mins w/ 1 min gap sep.

F4m aperture,1.5h exp. Photons at CCD Photons at CCD SNR
F4m aperture,1.5h exp. SKY OBJ. SNR
20m5,0.5nm, (21408) 16562 1571 12
17m0,0.25nm, (268871) 5043 12019 92
galaxies, Stars
8
System Design
Design Philosophy

• Clear difinitions of all the Interfaces to the
  Spectrograph and OCS
• Clean, Simple configurations, practicle and
  dedicated design all for reliable operation and
  burgit Saving
• Short scheduling to compensate the project time
  already lost.

9
System Design
E2V-CCD203-82-1
Imager selection
FORMAT 4K?4K , PIXEL 12?12 ?m QE
non-Uniformity 4 max. Readout Noise
3e(200KHz), 8e(1MHz) CTE 0.99999min (Parallel
Serial) Dark _at_173K 10e/pixel/hour max. Sensitive
Surface Flatness ?15 ?m Package with flexi-PCB
connector
Fiber positioning
10
System Design
Controller
AACAS
Astronomical Array Controling Acquisition System
SHUTTER
OPTO
shutter
TEMPERATURE
COUPLER

CONTROL

CCD

BIAS
FPGA
VOLTAGE

BIAS

CONFIGURE
CCD
PROTE
NIOS
Server
CTION
CCD CLK
CCD CLK

Dewar
EMBEDDED

DRIVER

CONFIGURE
TCP/IP
PROCESSOR
DC
RSTORE
PRE
16
BIT

GAIN
AMP
A/D

CDS
POWER
11
System Design
EMBEDDED PROCESSOR CONTROL
FPGA
SDRAM
NIOS
USER LOGIC
16MB
EMBEDDED
PROCESSOR
CCD Work MODE

ETHER NET IRQ
SRAM
GAIN CONTROL
1MB
MEMORY Interface
DMA INTERFACE
BINNING FACTOR

FLASH
8MB
RS232 INTERFACE

Window ReadOut

10M/100M
PIO INTERFACE

Integrate Timing
ETHERNET

USER INTERFACE
CCD SEQUENCE

V CONFIGURE
V-CLOCK
RJ45
H-CLOCK
12
System Design
EMBEDDED PROCESSOR
13
System Design
Limitation on dimensions
Camera head (A) has to be limited
within 100?100?100 mm But still rays like e
and r are obstructed. Another challenge is the
CCD chip has to be positioned only 6 mm behind
the field lens w/ accuracy of ?0.1mm. B cold
finger jacket C CCD controller D cryogenic
compressor
Beam Spliter
e
CCD
r
A
Grating
IMAGING MIRROR
Field lens
B
C
D
14
System Design
Cryogenics

• The mixed-gases Joule-Thomson (J-T)
  cryo-refrigerator (MJTR)
• built by the Technical Institute of Physics and
  Chemistry (TIPC), CAS
• Cooling temperature -120C
• High efficiency, COP gt 0.15 at -120C
• High reliability, long life without any
  maintenance for 5 years

15
System Design
Designed System
Camera head
C
C
D
Field Lens( window)
CCD holder
???
Heat Xchanger
??
????
???
??
??CCD???
?????
????
??
A/D
??
??
??
PWR
??
??
??
??
??
??
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
?
Compressor
Switching
Server
?
?
?
?
16
System Design
Software Flowchart