1. Piero Rapagnani I.N.F.N. Sezione di Roma
Cryogenic payloads and cooling systems (towards a third generation interferometer) part I: An Interferometer at Cryogenic Temperatures
Piero Rapagnani
I.N.F.N. Sezione di Roma
I will report on the activity C1 carried on in Rome to develop a facility for cooling mirrors of the interferometric gravitational antennas
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

2. Piero Rapagnani – INFN Roma
Why cool the mirrors?
Test masses and suspensions thermal noise reduces at low temperature:
Thermoelastic noise both of the mirror substrates and coatings decrease:
Thermal expansion rate a decreases at low temperature;
Mechanical Q of some materials increases at low temperature
@ w << wint
Thermal lensing:
Thermal conductivity increases and consequently reduces thermal gradients on the coating;
Refraction index variation with temperature is very small at low temperature;
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

3. Piero Rapagnani – INFN Roma
R&D on Cryogenics
Liquid helium
Refrigerators
Hybrid system
1) Study of the refrigeration system
- noise
- refrigeration power
2) Suspension compatibility: thermal conduction and acoustic quality factor Q measurements
3) Sensors at low temperatures
- accelerometers and position sensing devices
- actuators
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

4. Issues to cool the mirrors
Refrigeration system:
The injected mechanical noise must be negligible, the sensitivity must be preserved:
Þ Good mechanical isolation between the mirror and the cooling system;
Cooling time of the mirror as low as possible:
Þ Good thermal couplings;
Þ High refrigeration power;
Suspension system compatible with good mechanical and thermal couplings:
Thermal conductivities change with temperature;
Mechanical quality factor Q;
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

5. Cryogenic fluids and G.W. Detectors
The first cryogenic antenna in the world :
M=20 kg, T =4 K , n ~ 5 kHz
No excess noise
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

6. Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

7. Piero Rapagnani – INFN Roma
The second cryogenic antenna of the Rome group -1978:
M~ 400 kg, T =4 K , n ~ 1.8 kHz
Excess noise in the first
phase of operation:
Due to suspension system!!
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

8. Advantage of the superfluid liquid Helium: the  transition
He phase transition to superfluid
Data from the Antenna
EXPLORER
installed at CERN
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

9. Piero Rapagnani – INFN Roma
The current technique to cool down a Resonant Antenna requires “Heavy Work” and several weeks
Detector duty cycle: less than 1 month.
VIRGO
For an interferometric antenna 6 masses to be cooled.
To preserve the duty cycle this “heavy work” must be done in parallel.....
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

10. In a BIG Laboratory, large Cryogenic Facilities are possible
The example of LHC at CERN:
The Cryogenic Distribution Line (QRL) for the LHC (Large Hadron Collider). Each of the eight ~3.2 km QRL sectors is feeding Helium at different temperatures and pressures to the local cooling loops of the strings of superconducting magnets operating in superfluid helium below 2 K. With an overall length of 25.8 km the QRL has a very critical cost to performance ratio.
Technologies are available, but are VERY expensive and require extensive manpower
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

11. Piero Rapagnani – INFN Roma
An alternative way to cool down without liquid helium: the new generation of Cryocoolers
A Pulse Tube Refrigerator (PTR) or "G-M style" pulse tube cryocooler, is a variant of a Gifford-McMahon (GM) cryocooler.
PTR operate at low frequencies, typically <5 Hz.
Used a conventional oil-flooded G-M compressor and a valve set near the cold head to convert the continuous flow of helium to a low frequency pressure wave.
First stage
Second stage
Suitable for applications that require efficient operation:
No moving parts in cold head. Minimal vibration, low acoustic noise, reliability.
High efficiency: 2 to 3 times higher efficiency than GM cryocoolers for loads temperatures between 55 and 120 K.
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

12. Piero Rapagnani – INFN Roma
A possible solution
Passive vibrational isolation system for the heat link
Long heat link
Part of the refrigerating power absorbed by the isolators
Attenuation of the refrigerating power
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

13. Piero Rapagnani – INFN Roma
Our solution
Active vibration isolation system for the heat link
Shorter heat link
Refrigerating power preserved
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

14. Integration of VFC, payload and Superattenuator
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

15. Piero Rapagnani – INFN Roma
Q from refrigerator
Vacuum Chamber and Cryostat Thermal Shields
Marionetta Reaction Mass:
Thermal Shield at ~ 4K
High Efficiency Thermal Links
Silicon Monolithic Wire
Mirror Reaction Mass:
Thermal Shield at ~ 4K
Q from laser beam
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

16. Piero Rapagnani – INFN Roma
Q from refrigerator
Vacuum Chamber and Cryostat Thermal Shields
Marionetta Reaction Mass:
Thermal Shield at ~ 4K
High Efficiency Thermal Links
Silicon Monolithic Wire
Mirror Reaction Mass:
Thermal Shield at ~ 4K
Q from laser beam
Rough Estimates give
Tmirror ~ 10 K
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

17. Piero Rapagnani – INFN Roma
Q from Superfluid Helium Reservoir
A hybrid system using
Superfluid Helium could allow to reach T ~ 1.5 K
Vacuum Chamber and Cryostat Thermal Shields
Marionetta Reaction Mass:
Thermal Shield at ~ 1.5 K
High Efficiency Thermal Links
Silicon Monolithic Wire
Mirror Reaction Mass:
Thermal Shield at ~ 1.5 K
Q from laser beam
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

18. Piero Rapagnani – INFN Roma
Thermal Links:
Many Materials and
Composites available
Thermal behavior
at low temperatures
must be tested
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

19. The short/medium term future: The Cryogenic Suspension Test Facility
Still non investigated Problems:
Cryogenic (T~ 50 K)
Suspension Elements
Thermal link (T ~ 4 K)
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

20. Piero Rapagnani – INFN Roma
Frossati G., Leiden University, Leiden, The Netherlands
Gammaitoni L., INFN Perugia
Gennai A., INFN Pisa
Giazotto A., INFN Pisa
Giordano G., LNF INFN, Frascati
Guidi G., INFN Firenze/Urbino
Hello P., LAL-Orsay IN2P3/CNRS
La Penna P., EGO
Losurdo G., INFN Firenze/Urbino
Majorana E., INFN Pisa
Marchesoni F., INFN Perugia
Martelli F., INFN Firenze/Urbino
Mazzoni M., INFN Firenze/Urbino
Milano L., INFN & University Federico II, Napoli
Palomba C., INFN Roma
Passaquieti R., INFN & University of Pisa
Passuello D., INFN Pisa
Perniola B., INFN Firenze/Urbino
Punturo M., INFN Perugia
Puppo P., INFN Roma
Rapagnani P., INFN & University La Sapienza, Roma
Ricci F., INFN & University La Sapienza, Roma
Stanga R., INFN Firenze/Urbino
Vetrano F., INFN Firenze/Urbino
Vicere' A., INFN Firenze/Urbino
Vocca H., INFN Perugia
Acernese F., INFN & University Federico II, Napoli
Babusci D., LNF INFN, Frascati
Barone F., INFN Napoli & University of Salerno
Barsuglia M., LAL-Orsay IN2P3/CNRS
Bizouard M.A., LAL-Orsay IN2P3/CNRS
Brisson V., LAL-Orsay IN2P3/CNRS
Braccini S., INFN Pisa
Bradaschia C., INFN Pisa
Brocco L., INFN & University La Sapienza, Roma
Calloni E., INFN & University Federico II, Napoli
Cattuto C., INFN Perugia
Cavalier F., LAL-Orsay IN2P3/CNRS
Cella G, INFN & University of Pisa
Cuoco E., INFN Firenze/Urbino
Dattilo V., INFN Pisa
Davier M., LAL-Orsay IN2P3/CNRS
DeWaard A., Leiden University, Leiden, The Netherlands
De Rosa R., INFN & University Federico II, Napoli
Di Fiore L., INFN Napoli
Di Virgilio A., INFN Pisa
Dominici P., INFN Firenze/Urbino
Eleuteri A., INFN & University Federico II, Napoli
Ferrante I., INFN Pisa
Fidecaro F., INFN Pisa
Frasca S., INFN & University La Sapienza, Roma
Frasconi F., INFN Pisa
Contact persons: Fulvio Ricci Stefano Braccini )
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

21. Gravitational Wave group of the University of Rome La Sapienza &
ILIAS activity of the
Gravitational Wave group of the
University of Rome La Sapienza &
INFN Roma 1
L. Brocco, S. Frasca, G. Martinelli, M Perciballi, C. Palomba, P. Puppo, P. Rapagnani, F. Ricci, E. Serrani
The main R&D activities to achieve the realization of a full cryogenic suspension (task C1)
are focused on
Modification of a cryogenic facility hosting a new PTR refrigeration system for the mirror cooling
Low temperature monitor of the additional noise generated by the refrigeration system
Heat absorption measurements of the mirror substrates
Development of sensors and actuators for the position control of the mirror that are
compatible with the cryogenic environment
e) Design and construction of a suspension last stage protype for a cryogenic environment
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

22. Piero Rapagnani – INFN Roma
The VIRGO-CRYO tasks
The final goal of VIRGO-cryo is the construction of full scale prototype of a suspended test mass at cryogenic temperatures
The final goal is reached by merging the activity of task C1 and C3 during the last (4th) year of the project
Task C1 : main activity ==>>the cryogenic payload ( lower part) -->> “Roma La SAPIENZA”
Task C3 :main activity ==>>the cryogenic super-attenuator (upper part) -->> “INFN PISA”
There are several items in common between C1 and C3 also during the first part of the project : for example the development of sensor and actuators at low temperature, the simulation software …..
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

23. Piero Rapagnani – INFN Roma
Two possible strategies
COLD FINGER
Very Soft
Joint
Cryostat
COLD FINGER
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006
C3 task

24. Piero Rapagnani – INFN Roma
Work in progress
PT Refrigeration system : noise characterization to be completed in the low frequency region.
Set up of the vibration compensation system.
The results of the FEM simulation will be used to develop a new mirror cryogenic suspension to reduce the thermal resistance.
The PT Refrigeration system will be used to study the thermal properties of the materials candidates for the mirrors of a cryogenic interferometer and also of the e.m. actuators which can be used at low temperatures.
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

25. ( if Commission II agree )
Future work
( if Commission II agree )
- PT Refrigeration system : noise characterization to be completed in the very low frequency region
- In 10 weeks from now, we will start to operate the installation that includes the vibration compensation system
Q measurements on CaF2 sample of 10 cm in diameter.
New mirror suspension coupled to an elastic holder at 4K
We will produce also an alternative design based on sub-cooled superfluid helium (at pressure of 1 bar)
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006

26. Piero Rapagnani – INFN Roma
Modification of a cryogenic facility hosting a new PTR refrigeration system for the mirror cooling
Low temperature monitor of the additional noise generated by the refrigeration system
Heat absorption measurements of the mirror substrates
Development of sensors and actuators for the position control of the mirror that are
compatible with the cryogenic environment
e) Design and construction of a suspension last stage protype for a cryogenic environment
Piero Rapagnani – INFN Roma
ILIAS
April 27th, 2006