Download High resolution magnetoresistive position sensor for cryogenic use

High resolution
magnetoresistive position
sensor for the JWST
Tobias Junginger
Contents

The JWST
 Scientific
goals
 Instruments

Nirspec (near infrared spectrograph)
 Microshutters
 The
Grating wheel position sensor
The James Webb Space Telescope
Infrared space telescope
 scheduled for launch in 2013
 large mirror 6.5 meters in diameter and a
sunshield the size of a tennis court
 Both will fold up in space
 Orbit second sun-earth Langrangian point
(1,5 million kilometers from earth)

Scientific goals
Identify the first bright objects that formed
in the early Universe
 Assembly of Galaxies
 The birth of stars and protoplanatary
systems
 study the physical and chemical properties
of solar systems

Instruments
Type
Wavelength
Nircam
imager with a large
field of view and high
angular resolution
0,6-5 μm
Miri
imager/spectrograph
5-27 μm
Nirspec
Spectrograph
1-5 μm
The Micro-shutters
The GWA (Grating Wheel Assembly)
The GWA Position Sensor
 R3
R1 

U B  U e 

 R3  R2 R1  R4 
The GWA Position Sensor
Requirements
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Can measure two dimensions
Ready for using at a wide temperature range down to 4K
High sensitivity in movement direction (0,3 arcsec)
Low impact on the sensitivity by small deflections in Z
axis
Minimal power dissipation
No forces in movement direction
Compact size and very lightweight design (fieldplates +
magnets < 10g)
The GWA Position Sensor
Breadboard
Mount for the
fieldplates
Michelson
Interferometer
Light output to
photo diode
Mount for the
magnets
Piezoelectric
positioning unit
Light Input
from Laser