Fast cooling of interferometer payload Nomi, istituzioni? Un po’ di colore Marco Bazzan, Giacomo Ciani*, Livia Conti, Filippo Martelli, Antonio Perreca, Francesco Piergiovanni, Luca Taffarello, Flavio Travasso, Helios Vocca, Jean-Pierre Zendri *giacomo.ciani@unipd.it

The future is cold… and slow Thermal noise is in the way of exploring the Universe Many future GW IFO designs foresee cryogenic operations Room temperature IFO recovery after opening Dominated by pump-down Order 1 week Cryogenic IFOs recovery after opening: Dominated by cool-down Order month(s) Huge impact on commissioning activities and possibly duty cycle! Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

Situation even more critical! The KAGRA case Vanilla Diamond Like Coating Y. Sakakibara et al, 2014 Class. Quantum Grav. 31 224003 Additional thermal links ET larger masses thinner and longer fiber higher circulating laser power? Situation even more critical! Y. Sakakibara et al 2014, AIP Conf. Proc 2014 1573:1, 1176-1183 Add details on KAGRA suspension fibers Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

Cooling quietly ≠ cooling quickly Cooling to go in operation and cooling while in operation have conflicting requirements In operation: avoid vibrations! To go in operation: cool fast! Small cooling power sufficient to compensate (mainly) absorption of laser light Mechanical isolation required: Long fibers Small cross/sections Intermediate isolation stages Large cooling power required to cool down quickly from room temperature Seismic isolation irrelevant: Can use short links Can use big cross section No need for intermediate stages Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

Divide et impera! Separate and control… In operation Before operation Priority to minimization of vibrations from: seismic noise cooling system Radiative cooldown (boosted by high- emissivity coatings?) Conduction through thin suspension fibers Priority to fast cooldown of payload High-conductivity thermal link to the TM by direct mechanical contact Short, direct path to (dedicated?) cryostat Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

A quite simple idea… Build a separate device dedicated to initial cooldown, with minimal (zero?) impact on scientific operations Establish a temporary, strong thermal link to the payload Use it to quickly extract most of the heat from the TM, until it is close to the operating temperature Disengage the thermal link and any related mechanical short-circuit, leaving the IFO ready for operation High power cryostat Low noise, low power cryostat Low-temperature shield Low conductivity, Quite cooling path High conductivity cooling path Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

…a not so simple implementation High-conductivity thermal link to the TM without spoiling its mechanical characteristics Geometry of contact areas? Material, structure and surface finish of contact pads? Precise actuation mechanism Make solid contact with TM Avoid stresses on the suspension system Work in vacuum and wide range of temperatures Active control to compensate for suspension chain drifts Compatible with GW IFO vacuum requirements Avoid additional constraints on the already complex design of the suspension system Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

The CryoMirror project Define requirements Identify and later down-select viable approaches Build a prototype device Characterize prototype’s thermal and mechanical performance and impact on payload Demonstrate its operation on a full-size, plausible payload design Presented in Summer 2018 in response to a call from INFN group 5 -> Rejected Large budget (can be reduced) High engineering character (contacted interested groups with right expertise in Padova, but lack of framework to directly involve them) Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

Time is of the essence The more direct/urgent/definite application of such a device would be in ET ET is aiming at a technical design in ~2023 CryoMirror development timeline ~ 3 years The right time to start working on the problem would be… …now! Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

Recap In-operation requirements imply: slow cool-down times important impact on commissioning and duty cycle Idea: disentangle the initial and in-operation phases can significantly reduce cool-down times Proposal: study and develop a device capable of… Establishing temporary strong thermal link with payload Disengaging completely with no impact on scientific operation Start now to be ready for ET Currently no funding. Looking for: General interest Collaboration opportunities Funding ideas Let us know if you are interested and/or have ideas! Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia) Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia) CryoMirror WBS WP1: definition of requirements and control observables WP2: development of cryogenic test facility WP3: development of dummy payload WP4: development of moveable thermal link prototype WP5: development of in-loop and out-of-loop sensors WP6: study/development of contact interface with TM WP7: Functional test of the prototype WP8: High-vacuum compatibility Giacomo Ciani 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)