Transcript G060128-00 - DCC

HAM Passive Seismic Attenuation
System (SAS)
System Performance, Fabrication,
Assembly , Installation
Riccardo DeSalvo, Valerio Boschi, Dennis Coyne,
Yumei Huang, Virginio Sannnibale
LIGO Gravitational Wave Observatories
California Institute of Technology
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A seismically attenuated optical
bench for the HAM chambers
Existing Optical bench (recycled)
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Horizontal direction,
x, y,  the Inverted Pendula
Spring-box
platform
legs
Flex joints
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Attenuation in
the vertical direction,
the GAS springs
Optical bench
Spring-box
platform
GAS springs
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Performances
• Deliver more than 60 dB attenuation at > 1 Hz
• Single, passive layer attenuation to satisfy
requirements and minimize complexity
• Significant attenuation at the micro seismic peak
• Internal damping for minimized control burden
• Tidal control with pointing accuracy at ~ nm level
• No standing control forces
• Earthquake protection for up to ±12 mm shakes
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Performances
• Reliability ! ! !
1. No active components in vacuum
– Only coils in vacuum
– No electronics failures in vacuum ! ! !
– No power dissipation under vacuum ! ! !
2. No sealed gas volumes in vacuum
– No chance of crippling virtual leaks ! ! !
3. Four actuator/sensor groups for each three d.o.f.
– functions unimpeded by one sensor/actuator failure
4. Functionality unimpeded by power losses
– (earthquake protection)
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Difficulties
• Careful tuning and weight watching
required.
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Assembly philosophy
• Clean assembly and factory tuning
– Minimize expense of LIGO manpower
– Training fabricators to our procedures
• Shipping clean assembly
– Develop clean installation techniques in HAMs
– Install populated optical bench
assy.-proc.-D050198.doc
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Illustration of vertical attenuation
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
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Typical GAS performance
• LF tune sets the attenuation startup
– Can tune to 30 mHz
• 60 dB c.o.p. attenuation limit
– Can exceed with CW.
C.O.P. limit
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Transfer Function with Different Gain values
dB (G=1)
dB (G=5)
dB (G=4)
dB (G=3)
dB (G=2)
dB (G=8.5)
dB (G=-1)
dB (G=-2)
dB (G=-2.5)
dB (G=-2.8)
dB (G=-3)
40
30
20
10
0
-10
-20
-30
0.04
0.06
0.08 0.1
0.3
0.5
Frequency [Hz]
Lowering the system stiffness to 30 mHz
The Transfer Function shifts to lower frequencies,
The Q factor decreases
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Center Of Percussion effect
• Mass term
limiting the
attenuation
performance
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Magic Wand Implementation
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Magic wand tuning
80 dB GAS springs
vertical isolation
• (Still overcompensated)
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Horizontal direction, x, y, phi
the Inverted Pendula
GAS
platform
IP legs
Rigid Flex joints
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QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
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Typical IP
Horizontal performance
Loading factor
Leg mass &
counterweights
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IP performance
and improvements
• Minimize the mass of the legs
– => up to 80 dB attenuation
• Add counterweights to null the COP effect
– => beyond 80 dB attenuation
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Attenuation performance
10% payload
No counterweights
80 dB
at 100% load
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Introducing counterweights
from 80 dB to 100 dB
horizontal attenuation
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•10% CW tuning precision => x 10 perf.LIGO-G060128-00-R
Static and dynamic controls
MICRO POSITIONING
AND POINTING
• LVDT for local nanometer positioning memory
• Voice coil actuator dynamic controls
• Position and alignment controls < 30 mHz
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Sensors and coil actuators
• produced with UHV
compatible materials
and procedures
– TAMA resolution
(nm/√Hz)
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Assemblying a real
attenuator system
• What are we building
• How are we putting it together
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HAM SAS assembly
• Pull the blade over a form
• Clamp for transport
•Mount on the base and against the keystone
•Transfer the load and tune
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Tuning the GAS filter
• Use screws
for radial
compression
tuning
0,325
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• Add mass to
change
working point
0,32
Frequency [Hz]
0,315
• Best
mechanical
working point
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Y = M0 + M1*x + ... M8*x + M9*x
M0
0,28775
M1
-5,7998e-06
M2
1,2562e-07
R
0,99568
0,31
0,305
0,3
0,295
0,29
0,285
-600
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-400
-200
0
200
400
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LVDT voltage [V]
600
Horizontal direction,
x, y,  the Inverted Pendula
Spring-box
platform
legs
Flex joints
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Leg alignment procedure:
avoid cradle effect
• Legs aligned
(cradle effect depressed)
to 2.5 10-4 m/m
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Frequency/Load tuning
<30 mHz tune on stable ground
0.5
frequency [Hz]
frequency [Hz]
3.5
3
2.5
2
0.4
0.3
1.5
0.2
1
0.1
0.5
0
0
100
200
300
400
500
600
700
mass[kg]
800
0
500
y = m2 * sqrt(m1-M0)
Value
Error
m1
741.47
1.3757
m2
0.028992
0.00041402
Chis q
0.00062295
NA
R
0.99751
NA
550
600
650
700
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750
mass[kg]
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Installing SAS in the
HAMs
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Installing SAS in the
HAMs
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Installing SAS in the
HAMs
• Two long rails are installed across the HAM doors extending two
meter outside the chamber, resting on synchronous jacks on installation
carts
• The rails are lowered to extract the optical bench from the chamber
• The optical bench slides off the HAM chamber and is lowered on a
cart
• The rails descend to pick HAM-SAS from its cart
• The rails are raised to slide HAM-SAS inside the HAM
• The rails are lowered to position HAM-SAS on cross tubes
• The operation is repeated to pick-up the optical bench and lower it
over HAM-SAS. The optical bench can be installed with most preassembled optics
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HAM-SAS
primary seismic attenuation
for Advanced LIGO
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