Fast cooling of interferometer payload

1. Fast cooling of interferometer payload 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

2. 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! 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

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

4. Cooling quietly cooling quickly Cooling to go in operationand cooling while in operation have conflicting requirements To go in operation: cool fast! In operation: avoid vibrations! 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 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

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

6. A quite simple idea… • 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 Build a separate device dedicated to initial cooldown, with minimal (zero?) impact on scientific operations Low noise, low power cryostat Low conductivity, Quite cooling path Low-temperature shield High power cryostat High conductivity cooling path 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

7. …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 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

8. 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) 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

9. 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 Theright time to start working on the problem would be… …now! 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

10. 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! 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

11. 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)

12. 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 16-Feb-19, KAGRA-Virgo-3G detectors Workshop (Perugia)