PRELIMINARY DATA ON THE COATING AT THE

LIQUID NITROGEN TEMPERATURE

Flavio TravassoVirgo-Perugia Group

Samples• TiO2/SiO2 caoted slab (50 layers evaporated by

SILO) (Measured)

• TiO2 doped Ta2O5 coated slab (Sputtering by LMA) (Work in progress)

• Co doped Ta2O5 coated slab (Sputtering by LMA) (Next months)

• Uncoated fused silica (311) slab supplied by LMA (Next months)

Dimension of the slabs:

• Silo TiO2/SiO2: 25mm x 25mm x 50 μm with a coating of 5 μm

• LMA doped samples: 5mm x 41mm x 104 μm with a coating of about 5 μm

Labview Interface

Ni

He

Ni

He

He

Cu

Laser

HV Amplifier

Clamp tightened using a spring

Preliminary data: TiO2/SiO2

coating Loss angle vs. Temperature:

coated and uncoated sample have a minimum at about 160K

The trend of the coated The trend of the coated sample seems to be sample seems to be drivendriven by the behaviour of by the behaviour of substrate of fused sillicasubstrate of fused sillica

Levin model (using a FEM model): we need a good database about the thermal trend of ETiO2 (loss angle of the coating at room temperature is about 10-3)

50 100 150 200 250 300

1E-5

1E-4

1E-3

Membrane TiO2 / SiO

2

Mode 1760Hz Uncoated Mode 1180Hz Coated Mode 1525Hz Coated

Loss

Ang

le

Temperature [K]

Coated Sample

Uncoated Sample

The silica has a peak at the lower temperature…maybe we are seeing the first part (?)

Preliminary data: TiO2-doped Preliminary data: TiO2-doped Ta2O5 coating (1) Ta2O5 coating (1)

• Coated sample:same trend of the

TiO2/SiO2 coated sample • Uncoated sample: work in progress

Work done in collaboration with LMA/Virgo laboratory

Preliminary data: TiO2-doped Preliminary data: TiO2-doped Ta2O5 coating (2) Ta2O5 coating (2)

• Increasing of the loss angle decreasing the temperature

• The loss angle seems to be frequency dependent: we need much more data to increase the statistics

Temperature hysteresis

Cool down

Warm up

The dispersion of the data and the value of the ΦTot have a minimum around 160K cooling down and aroud 120K warming up

Open problem Short term upgrade: change present Short term upgrade: change present

clampclamp• New suspension system: MIT like New suspension system: MIT like • Thermalization of the sample: moving Thermalization of the sample: moving

contact, gas of He inside the contact, gas of He inside the chamber(?)chamber(?)

• Reading of the temperature: twin Reading of the temperature: twin systemsystem

Long term upgradeLong term upgrade• Pulse tube: evaluation of the noisePulse tube: evaluation of the noise

Ni

He

Ni

He

He

Cu

Laser

Labview Interface

Summary

Trend of the data versus the Trend of the data versus the temperature maybe driven by the temperature maybe driven by the substratesubstrate

Frequency dependency of the loss Frequency dependency of the loss angle at temperature lower than angle at temperature lower than 160K160K

Need to improve the system: short Need to improve the system: short and long term upgradesand long term upgrades