Transcript Design study for ET 3rd generation Gravitational Wave

Design study for ET
3rd generation
Gravitational Wave Interferometer
Work Package 2
Suspension, Thermal noise and Cryogenics
Piero Rapagnani
e-mail: [email protected]
Contract NumberRII3-CT-2004-506222 
The Challenge:
Find a way to push the sensitivity of a gw detector as
near as possible to 1 Hz
Underground
Passive and active seismic attenuation
Low dissipation materials for mirror suspensions
Cryogenics
B 1.3 .4.2: WP 2 description
Work package
2
Start date or starting event:
number
Work package title
Suspensionrequirements characteristics
Activity type:
RTD
Participant number
1
2
3
4
Person-months per
18
69
0
28
participant
M2
5
0
6
41
Objectives: Definition of the requirements of the optics suspension in ter
ms of seismic isolation, mechanical losses
and thermal conduction. Conceptual designof the suspension
Partecipants:
1 - EGO (FRA-ITA)
2 - INFN (ITA) (GE, FI, NA,PI, PG, RM1, RM2)
3 - MPG (DEU)
4 - CNRS (FRA)
5 - University of Birmingham (UK)
6 - University of Glasgow (UK)
7 - VU (NL)
8 - University of Cardiff (UK)
+ Science Team
Thermal Noise Requirements for the Suspensions of the 3rd Gen ITF - Task ID 18
Month 1-33
Month 1-12
Material Intrinsic losses requirements at low temperatures
Month 1-15
Seismic Attenuation Requirements of the suspension (100 days – M15)
Suspension seismic attenuation requirements (input from site selection)
Identification of control strategy and optimal mode frequencies for suspension elements
Month 10-26
Preliminary Conceptual Design of the overall Cryogenic Suspension (360 days – M24)
Month 12-26
Upper Suspension preliminary Design:
Active vs. Passive Super Attenuator (4 Months)
Conceptual design of damping, alignment and control strategy (12 Months)
Cryogenic compatibility of Upper Suspension Design (12 Months)
Month 10-24
Last Stage Suspension Preliminary Design (300 days - M24)
Test Mass Requirements (3 Months – M13)
Test Mass Definition (4 Months – M23)
Suspension Wires material and size choice (Input from Material Selection)
Definition of last stage actuation strategy and technology
Month 10-26
Cooling Requirements and Cooling Strategy definition (360 days - M26)
Thermal Path definition and Thermal Links Requirements (6 Months - M21)
Thermal Links Conceptual design (6 Months – M26)
P. Rapagnani
Finalization of the Conceptual Design of the Overall Cryogenic Suspension Month
26-33
Material Intrinsic losses requirements at low temperatures (12 Months – M12)
Identify the materials with best properties for:
Mirror Bulk, Mirror Coating, Mirror Suspension Wires
Quantify the constraints from the thermal, optical and anelastic point of view and identify
possible tradeoffs.
Identify a possible R&D path to materials selection.
Seismic Attenuation Requirements of the suspension (100 days – M26)
Suspension seismic attenuation requirements (3 Months – M26) (input from site selection)
Identification of control strategy and optimal mode frequencies for suspension elements
An extended simulation of the suspension must be developed, where the best control strategy can
be identified and tested.
It is necessary to verify that the system has no mechanical modes which involve critical degrees
of freedom and are not sensitive to the foreseen control loops.
P. Rapagnani
Preliminary Conceptual Design of the overall Cryogenic Suspension (12 Months – M23):
Upper Suspension preliminary Design:
Active vs. Passive Super Attenuator (4 Months)
Conceptual design of damping, alignment and control strategy (12 Months)
Cryogenic compatibility of Upper Suspension Design (12 Months)
Identify the constraints on the upper suspension elements due to the connection with the low
temperature last stage elements. Identify a suspension interface between last stage element
and suspension chain which minimize thermal conduction.
Last Stage Suspension Preliminary Design
Test Mass Requirements (460 days – M22)
Test Mass Geometry and Size definition (Input from Optical Configuration)
Test Mass Mechanical and Optical losses requirements (12 Months – M12)
Test Mass Definition (4 Months – M23)
Suspension Wires material and size choice (Input from Material Selection)
Definition of last stage actuation strategy and technology
Actuation and Sensing at low temperatures allow the use of superconducting
techniques which are the lowest noise technologies available, at the cost of an
increased complexity of the system and of the necessity to be at low temperatures to
make it work. It is possible to design hybrid systems which could have traditional
sensing and actuation, working also at room temperature, in parallel with
superconducting low noise sensors, which could be used once the proper operating
point of the antenna is reached.
P. Rapagnani
Cooling Requirements and Cooling Strategy definition
Identify the requirements on test mass temperature in order to have a negligible thermal noise,
with respect to seismic, newtonian and radiation pressure noises.
Identify the best cooling strategy (refrigeration only, cryogenic liquids, hybrid techniques)
regarding:
underground facilities safety and costs (input from site selection),
power to extract from the test mass (input from mirror optical properties)
noise input constraints
Thermal Path definition and Thermal Links Requirements
Identify the best possible path depending on the cooling strategy: tradeoff between the
necessity to have a short thermal link and a very low frequency, (hence very long)
connection of the mirror to the refrigeration apparatus.
Identify the constraints on the acoustic attenuation chain for the thermal links.
Thermal Links Conceptual design (3 Months – M24)
Finalization of the conceptual design of thermal links attenuation chain, i
including the thermal contacts between refrigeration apparatus and last
stage elements.
P. Rapagnani
Following the approval of the ET Design Study:
Definition of tasks and tasks responsibles
together with involved groups
Kick-off meeting of the WP2 activity
Periodic (bimonthly?quarterly?) meetings
Encourage exchanges and coordination between
The involved groups and with other groups
in the Science Team
P. Rapagnani
The Prototype
of Cryogenic Payload
We have designed and built a
cryogenic payload scaled 1:3.5
compared to the VIRGO standard
Marionette hosting the central insert made
of silicon (at present the central insert is
made of Al)
Mirror suspended by silicon strips attached
with silica bonding
(Present suspensions are copper strips)
Electromagnetic actuators like
the Virgo mirrors lateral ones
(macor support, copper wire
kapton insulated)
Silicon mirror (Preliminary
assembly with a fake
aluminum mirror)P. Rapagnani
Reaction mass of the mirror
made of copper, gold coated
Minipayload
Mechanical
Modes
(room temperature
measurements;
Noise injected by coils)
sensor monitoring the
mirror position
PSD (Horizontal displacement)
PSD (Vertical displacement)
Fiber Bundle (Sensor used also at low temp.)
1
10
10
10-1-1
10
1/2
2
V/(Hz)
V/Hz
10-3-3
10
10-5-5
-7
10 -7
Torsional mode
October, 27 2006
10-9-9
10
Hz
0
1
Frequency [Hz]
Puppo
P.Paola
Rapagnani
ILIAS Meeting - London
2
3
4
5
Pendulum mode
10
300
Cooling test on the
small scale
payload prototype
Temperature (K)
2 (First Cold stage)
3 (Second Cold Stage)
10 (Mirror)
11 (Reaction Mass)
250
200
150
Fiber
Bundle
Sensor
100
Hours
50
0
0
50
100
October, 27 2006
150
200
250
300
P. Rapagnani
11
Next steps
 Improve the vibration reduction scheme
 To modify the sensing scheme to improve the noise floor at closed loop to
the control of the horizontal degrees of freedom ;
 Full scale cryogenic payload (with silicon)
 Test a full scale silicon mirror at cryogenic temperature in
the EGO cryostat in Cascina, Virgo Site;
 To define in a realistic way the refrigeration procedure
 The properties of the full scale silicon mirror.
P. Rapagnani
12
Cryo-Compatible Superattenuator design
Pintracavity= 500 kW
acoating=1ppm
Pcoating=500 mW
•High Thermal impedance
MRM wire
•The upper part is thermally
insulated by thermal screens
P. Rapagnani
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