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Cryogenic Measurements on Disks at LMA

This research project involves cryogenic measurements on disks using a Closed Cycle Cryostat and GeNS technology. The focus is on studying the internal friction of IBS sputtered Silicon thin films before and after annealing. The measurements reveal strong mode dependence of the quality factor, which requires further investigation and a procedure to remove the contribution of the thermoelastic effect.

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Cryogenic Measurements on Disks at LMA

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  1. CryogenicMeasurements on Disks at LMA Mereni L., Granata M., Michel C., Cesarini E., Lorenzini M., Amato A., Piergiovanni F., Cagnoli G.

  2. -Somepreviouscryogenic tests withGeNSwere made in 2013 by Cagnoli and Granata, but the Setup wasbuiltaround a Standard Heliumflow cryostat. -The Cryo-GeNSiscurrentlybeingused in the context of a collaboration with Naval ResearchLabsaimed at studying the internal friction of IBS sputteredSilicathin films before and afterannealing.

  3. The Setup: Closed Cycle Cryostat Cryomech Pulse Tube GeNS Plate cooled by a thermal link Additional radiation shield

  4. The sampleiscooled down by radiation. There is a caveatwithlowtemperatures! A Silicondiode wasattached to a 3’’ wafer and the temperaturewascontinuoslymonitored and compared to thatshown on the temperaturecontroller. As the temperaturerises the heatexchangedby radiation becomes more and more efficient makingless important the laser heating and the other ‘’strayheat sources’’

  5. The frequency shift is a good probe to check the thermalization of the sample. The accuracy of the frequencymeasurementdepends on the SNR and the sampling frequency

  6. Local maximum of the quality factor due to the null of the thermoelasticeffect -Measurements on the baresubstrateprovidefurther information on the actualtemperature of the sample. -The Quality Factor seems to bestrongly mode dependant. The reason for theseaccentuated mode dependencyisstill to be made clear…

  7. Afterannealing, the losses of the resonator (substrate + coating) becomelowerthanthose of the substratealone. Weascribethisphenomenon to the thermo-elasticeffect. See Poster ‘’ThermoelasticDamping’’ by Cesarini et al.

  8. W15040 Whenthishappens the extractedcoatingloss angle becomesnegative…

  9. -Six complete sets of measurements (substrate + as depositedresonator + annealedresonator, repeated for 2 differentsamples) have been performed at cryogenictemperaturesin a closed cycle cryostat hosting a GeNS. -Weobserved a strong mode dependence of the quality factor that has to beexplained - Even at cryogenictemperatures the thermoelasticeffect of the wholeresonatorhinders a simple interpretation of the data and a procedure must bedeveloped to removeits contribution

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