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

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

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

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

Cryogenic fluids and G.W. Detectors The first cryogenic antenna in the world 1974-1980: M=20 kg, T =4 K , n ~ 5 kHz No excess noise Piero Rapagnani – INFN Roma ILIAS April 27th, 2006

Piero Rapagnani – INFN Roma ILIAS April 27th, 2006

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

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

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

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

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

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

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

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

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

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

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

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

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

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 (fulvio.ricci@roma1.infn.it) Stefano Braccini (stefano.braccini@pi.infn.it ) Piero Rapagnani – INFN Roma ILIAS April 27th, 2006

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

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

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

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

( 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

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