FSU Jena Nawrodt 10/06 #1/16 Ronny Nawrodt ILIAS/STREGA Annual Meeting London, 27 October 2006 Friedrich-Schiller-Universität Jena, Germany Cryogenic Q-measurements on Calcium Fluoride

FSU Jena Nawrodt 10/06 #2/16 Calcium fluoride research manufacturer: Schott 1 polishing: surface + circumference (Hellma-Optik 2 ) (100) orientation  75 mm  75 mm mass: ~ 1100 g 1 www-schott.de, 2

FSU Jena Nawrodt 10/06 #3/16 CaF 2 – Measuring Setup special cryostat 1 (5…300 K, p<10 -3 Pa) suspension: polished tungsten wire 2 ( 75 µm) electroststic exciter (~ 1.2 kV) interferometric read-out 3 (1 point) L < 0.2 nm up to 500 kHz 1 Nawrodt et al., Cryogenics 46 (2006) , 2 Advent Research Materials, 3

FSU Jena Nawrodt 10/06 #4/16 CaF 2 – Mode Scan mode excitation: high voltage ~ 1.2 kV 33 modes found within 25 kHz – 100 kHz interferometer spot CaF 2, (100) orientation,  75 mm  75 mm

FSU Jena Nawrodt 10/06 #5/16 CaF 2 – Ring-Down Experiment CaF 2, (100) orientation,  75 mm  75 mm T = (79.5  0.2) K f 0 = (  0.1) Hz t = (1490  10) s Q = (1.97  0.01)  10 8 reproducibility ~ 20% Q = (2.0  0.4)  10 8

FSU Jena Nawrodt 10/06 #6/16 CaF 2 – Measured Q-values Hz Hz Hz influence of the suspension maximum 64 K: Q = 3.2  10 8,  = 3.1  K ongoing work (defects? similar to crystalline quartz) intrinsic limit thermoelastic ? CaF 2, (100) orientation,  75 mm  75 mm

FSU Jena Nawrodt 10/06 #7/16 CaF 2 – Interaction with Suspension (1) Hz K CaF 2, (100) orientation,  75 mm  75 mm ~140 K~196 K

FSU Jena Nawrodt 10/06 #8/16 CaF 2 – Interaction with Suspension (2) Hz Hz ~140 K ~196 K

FSU Jena Nawrodt 10/06 #9/16 CaF 2 – Interaction with Suspension (3) Hz K Hz Hz Difference fits to a harmonic of the suspension! CaF 2, (100) orientation,  75 mm  75 mm At lower temperatures no resonances are possible!

FSU Jena Nawrodt 10/06 #10/16 CaF 2 – Impurities? (1) temperature dependence Hz Hz K no Arrhenius-law ? ongoing work CaF 2, (100) orientation,  75 mm  75 mm

FSU Jena Nawrodt 10/06 #11/16 CaF 2 – Impurities? (2) substrate: crystalline quartz, Q(T) understood phonon-phonon large contribution crystalline quartz, c-axis orientation,  75 mm  12 mm impurities sum

FSU Jena Nawrodt 10/06 #12/16 CaF 2 – Low Temperature Limits (1) Thermoelastic limit Braginski 1 : longitudinal mode of a bar CaF 2, (100) orientation,  75 mm  75 mm  - thermal conductivity  - thermal expansion c – heat capacity per unit volume  - mass density  0  - resonant frequency 1 Braginski et al., Systems with Small Dissipation

FSU Jena Nawrodt 10/06 #13/16 CaF 2 – Low Temperature Limits (2) thermal conductivity heat capacity  - 30 … 320 K, Batchelder et al., The Journal of Chemical Physics 41 (1964)  - 3 … 500 K, Slack et al., Phys. Rev. 122 (1961) C – 3 … 30 K, Huffman et al., Phys. Rev. 117 (1960) 53 … 300 K, Todd et al., Journal of the American Chemical Society 71 (1949) thermal expansion

FSU Jena Nawrodt 10/06 #14/16 Grating Research pure substrate 1 mm grating crystalline quartz, c-axis orientation,  75 mm  12 mm

FSU Jena Nawrodt 10/06 #15/16 Silicon research new substrates - doping: boron, phosphorus - electron / hole - different doping concentration (10 14 … cm -3 for n-doped, … cm -3 for p-doped) - CZ / floating zone  100 mm  100 mm (~2 kg)  150 mm  90 mm (~4 kg)

FSU Jena Nawrodt 10/06 #16/16 Summary calcium fluoride research: 3.210 64 K lower Q‘s at lower temperatures solid-state basic research ongoing (phonon-phonon interaction) further steps in Jena: silicon bulk research (doping!) tantala research all-reflective components