ILIAS - GWA N5 - Strega JRA3 General Meeting

Orsay - November 5th-6th, 2004

M1 Activities

Collaboration : 4 groups• Groups that have done some work during months

1 to 6– Virgo-Mat Group (INFN Firenze, Perugia, Pisa)

– CNRS, Laboratoire d’optique de l’ESPCI, Paris

– University of Glasgow, IGR

• Groups that will produce deliverable before month 12– Auriga LNL (The design of the capacitive readout for the Q-factor

measurement has begun )

Aim of the M1 task • Aim: Investigation of mechanical thermal

and optical properties of candidate materials for next generation detectors.

• Materials considered: Si, CaF2, and white YAG.

Benefits for future detectors• Replacement of amorphous material by

crystalline material for mirror substrates.

• Decrease of the thermal noise contribution.

• Increase of the Q-factor of mirror substrates.

• Improvement of the optical performances (thermal lensing, birefringence,…)

M1 activities at Virgo-Mat laboratories

– Advanced materials for mirror substrates• First year task: Room temperature measurement on Si and CaF2

– Michelson-Morley ITF in Perugia– Measurement of substrates for future ITF

» Middle size CaF2 substrate» Mono-crystalline Si substrate “Virgo size”

– Milestone and Deliverables• Cryogenic facilities for mechanical measurements fully operational

– Involved groups• INFN Firenze• INFN Perugia• INFN Pisa

• Bulk dissipation• thermodynamical dissipation in the bulk

– new materials under investigation: CaF2, Silicon (Q meas. PG);– finite elements model of the mirror suspension in progress (Fi-Urb PG)

Mirror thermal noise

Calcium Fluoride• High thermal conductivity at low T, low expansion coefficient at low T

• Disk of 180mm diameter, 38 mm thickness

• Polished faces, rough lateral surface (to be polished)

107

• Measure dominated by excess losses

• In any case comparable with FS in the same condition (not usable at low T)

107

Silicon test masses• Mono-Crystalline silicon disk

– 350 mm diameter– 100 mm tick– Rough lateral surface– To be polished

• Excess losses under investigation and reduction

The cryogenic facility

• Located in Perugia

• Chamber for small samples

• Under cooling in these days

The clamping system

Evolution

• No delay expected in the next year

M1 activities - Glasgow Group

S. Reid1, G. Cagnoli1, D.R.M. Crooks1, E. Elliffe1, M.M. Fejer2, A. Heptonstall1, J.

Hough1, P. Murray1, O. Solgaard2, S. Rowan1, R. Route2, P. Sneddon1, S. Zappe2

1 University of Glasgow

2 Stanford University

M1 activities at Glasgow

• Aim to investigate:– internal dissipation of doped/un-doped bulk silicon as a function of

temperature– dissipation due to aspects of test mass design related to use as

diffractive optics

• Milestone and Deliverables• Q measurement facility fully operational• Room temperature mechanical measurements on Si achieved• Low temperature Q measurement facility

Studies of silicon as a test mass substrate

• Preliminary room T measurements made of mechanical dissipation of bulk silicon samples suspended on silk thread or wire loops– Internal resonant modes of the samples

excited; decay of mode amplitude measured To high voltage

Excitation plate(behind mass)

Silicon samples cut along different crystal axes, [111] and [100]. The [111] sample was boron-doped.

Dissipation of two silicon samples of identical geometry, supplied by Stanford, was measured over a range of frequencies.

Clamp

Suspension thread/wire

Schematic diagram of front view of suspended test mass.

Test mass

Results for silicon at room temperature

• Lowest loss obtained so far = (9.6 +/- 0.3) x 10-9

• Comparable with the lowest loss factors measured at room temperature

Sample [b] typically showed lower dissipation

Sample [a]: [100] cut, nominally undoped

Sample [b]: [111] cut, boron doped

Reason for difference seen in measured loss factors (eg crystalline orientation of the sample, the dopant, or some other reason) is– under investigation – some evidence to suggest may be due to crystalline orientation

Measured loss factors for two samples of bulk silicon

Recall, varying dopant concentrations can vary the thermal conductivity of silicon.

This can impact both levels of thermoelastic dissipation and mirror figure distortion under thermal loads – requires further study.

M1 activities at ESPCI

– Advanced materials for mirror substrates• First year task: Room temperature measurement on Si, CaF2, and

YAG– Absorption measurements– Birefringence measurements

– Milestone and Deliverables• Cryogenic facility for absorption measurements has begun (tested at

77K)

Room temp. absorption measurements

• Measurements performed on an existing bench for CaF2 and YAG, bench built for Si.

• CaF2 (@1064nm)– Between 2 and 10 ppm/cm, sample dependant, position dependant

• White YAG (@1064nm)– ~10 ppm/cm

• Si (@1300nm)– Undopped

– N-doped high resisitivity <10 ppm/cm

– P-doped high resistivity <10 ppm/cm

Bench sensitivity limit, problem solved thanks to EGO (month 10 ?)

Si birefringence measurements

• Silicon intrinsic birefringence– Tests on <111> (done month 6) and <100> samples

– Theoretical investigation has begun (month 4)

– Local (non-imaging bench) has been built (month 5) for orientation dependant birefringence measurements

• Silicon induced birefringence– Imaging bench realization has begun (expected working month

9) for strain and dislocation induced birefringence.

Si intrinsic birefringence

nmax=410-6 @1300nm

CaF2 and YAG birefringence measurements

• Intrinsic and induced birefringence– Local (non-imaging bench) has been built (month 5) for

orientation dependant birefringence measurements

– Imaging bench operational.

– Not tested on large scale single crystals

Evolution

• No delay expected in the next year