The EGO R&D Program

1. The EGO R&D Program Filippo Menzinger EGO Date: 22 September 2005

2. EGO R&D program • EGO – The European Gravitational Observatory - in order to fulfill one of his statutory missions, i.e, to promote an open co-operation in R&D,has a specific R&D budget for major Virgo upgrades, for new detectors and, in general, for gravitational physics. • R&D contracts are open to all GW European laboratories.

3. Scope of the EGO R&D program • EGO launched in Autumn 2002 the first call for R&D proposals open to European groups regarding advanced GW detectors. • To this call responded groups pertaining to the Virgo collaboration, resonant detector groups, and groups in Germany and UK. • The proposals were examined by the EGO Scientific and Technical Advisory Committee, the “STAC”. • On STAC recommendation several R&D were financed by EGO

4. The R&D program 2003-2005 • Funds allocated or committed in years 2003-2006: 2,183 k€ • 25 Signed conventions/contracts with proponent laboratories • 12 Fellowships contained in those conventions. • Of these R&D programs the repartition may be broadly shown as in this graph

5. R&D themes Adaptive optics for GW ITFsNaples University CNRS OCA- ILGA Virgo Control System upgrade IN2P3 LAPP INFN-Pisa-EGO Surface corrective coatings for GW ITFsIN2P3 LMA Full scale prototype of fused Silica SuspensionsUniversity Perugia Improvement of Q measuring facility for mirrors University Perugia Improvement of coatings QUniversity Perugia IN2P3 LMA Optimisation of interferometer optical parametersCNRS OCA-ILGA ESPCI Modelling of Thermal NoiseUniversity Perugia University Firenze-Urbino Study of signal re-cyclingIN2P3 LAL Laser cooling of fibresPisa University CO2 laser for monolithic suspensionsGlasgow University Wide band transducer for Dual Torus detectorUniversity Padova Spherical detector for high frequency gwU.Roma-2 Tor Vergata Study of quantum noiseCNRS LKB CNRS ILGA Thermal Noise at Cryogenic TemperaturesINFN Pisa and al Data analysis of gw from coalescing BHCardiff University CNRS-ILGA Study hollow fibre opticsCNRS OCA - ILGA Si absorption characterization a 1.5 mm ESPCI

6. the 2003-2005 R&D program status Last April the STAC examined the intermediate reports submitted by most of the current contractors for the EGO R&D program Hereafter, some elements of those reports and of comments by STAC are reported.

7. Silicon Suspensions laser cooling University-Pisa The research group reported successful demonstration of anti-Stokes cooling of a small sample of BaY2F8 (BaYF) single crystals doped with Yb (2.5%) grown in the University of Pisa laboratory. The experiment consisted of measuring the cool down of the crystal over time (~50 minutes) while it was being pumped by 3W of 1025 nm CW light from laser diodes. The steady-state cooling achieved was 4K at room temperature. Observations: The experiment has been successful. The next key issue is to develop a detailed plan of how this idea can be actually implemented in a suspended interferometer in order to reduce thermal noise of fibres.

8. Improvement Q measuring facility Perugia A close collaboration, as STAC previously suggested, was set up between Perugia and LMA-Lyon on the measurement apparatus delivered to Lyon. The positive results are clear from both the Perugia and Lyon reports of progress. Progress has been made in improving the sensitivity of the instrument at Perugia which has as its goal the direct measurement of the thermal noise. The sensitivity of the instrument is now sufficient to measure the peaks of the thermally-excited resonances in the test piece, and the use of the instrument to characterize a series of coatings can now start.

9. Thermal Noise at Cryogenic Temperatures INFN-Pisa et al.,EGO The cryogenic facility is growing properly. The laboratory space at EGO is completed and the large cryostat is expected to be delivered at EGO in a few weeks time. It is designed to house a full last stage of Virgo-kind suspension with a full Virgo-size mirror. Everything seems in schedule and no major problems are foreseen, apart from the fact that no Company with the necessary experience to produce monolithic Si strips at reasonable price has been found so far. This could become a problem along the research line on the use of pure Si as mirror material.

10. Fused Silica Suspensions Perugia The research group reports completion of a fused silica wire production facility in Perugia. They validated the wire production procedure. The facility is now in production mode that is fully automated and stable. It is possible to set a fibre diameter and the computer selects the pulling speed to drive the machine. They are able to produce custom designed fibres with variable diameters from 10 - 400 microns. The group successfully developed and delivered an OH flame based fibre pulling system. The machine is currently under installation at EGO in the new laboratory there created to house both the fibre pulling techniques and the Cryogenic facility. They also validated the silicate bonding procedure and have transferred knowledge about the technique to the EGO staff at Cascina.

11. CO2 laser for monolithic suspensions Glasgow Good progress was made on the development of the CO2 laser fibre pulling and welding machine. A simple machine with a fixed feed-pull speed ratio was tested and used to produce ribbons (5-9mm wide and 100mm-300mm thick) and fibres (15mm-18mm diameter). The power stability of the CO2 laser was improved to get better control on the width and thickness of the ribbons. Components for the first version of the more complicated pulling machine are on order and the test of the first prototype is expected to start soon. The performance of that prototype will give a good indication on the overall progress made in this project. Its deliver at EGO is expected in early spring 2006

12. Signal re-cycling LAL The Orsay LAL group works together with groups in LIGO on the development of simulation tools for a dual recycled interferometer and on the commissioning of the 40m Caltech prototype in its dual recycled configuration. The proposed work for the next period is side-band phase noise propagation, radiation pressure effects, higher order modes, implementation into SIESTA. STAC suggested to put high priority on the validation of the simulation with experimental results wherever possible.

13. Data analysis ILGA-Cardiff Spinning binary black holes A new postdoc was engaged (Nov 2004) at Cardiff for this effort. Her first efforts (April 2005) have been to ‘get up to speed’ in the field; new work has led to developing a code to compute the waveform from a pair of spinning binary black holes. This is still in development and testing. The objective remains to develop templates which cover the additional variable of the black hole spins, a quite necessary undertaking.

14. Control System upgrade Annecy-LAPP, Pisa, EGO -Task 1 - DSP (Pisa, EGO). 6U VME Carrier board hosting a PC/104Plus CPU module with Fast Ethernet and Linux OS, a mezzanine board with up to 6 DSPs and a mezzanine board for timing and optical link interface. Prototypes are in construction; tests in course. -Task 2 and 3 – (LAPP) TOLM (Timing and Optical Link mezzanine) - Good progress with extensive test of the digital optical link and start of development of interface programs have been reported. -Task 4 - ADC (LAPP). Improved differential interface modules with programmable filter for the existing ADC boards: 30 boards (60 channels) ready for tests by May. The new ADC board will integrate such new features after tests. -Task 5 - New DAC/Coil driver  (Pisa, EGO) Conceptual design ready. A prototype has been tested smoothly. -Task 6 - New demodulation board (LAPP). No progress reported as yet. -Task 7 - New detection electronics at higher modulation frequency (LAPP). No progress reported as yet.  Observations: -Overall, the activities are progressing quite well. -Most activities at Pisa are reportedly focused on the DSP board. However, progress has been made also on the development of the new DAC (Task 5). -It is advisable that a detailed prioritized plan for the swap of the new electronic boards and modules is agreed with Virgo and prepared.

15. Modeling Thermal Noise Perugia and Florence-Urbino The collaboration set up, tested and shared a simulation environment, with ANSYS, to model thermal noise in mirrors and mirror suspensions. Perugia     Then Perugia dedicated to model the VIRGO mirrors, to a simulation of substrate+suspension wires+multilayer coating (taken from F/U results)+silicate bond , and made comparisons  between the outcome of the model and relevant quantities, as mirror modes frequencies and quality factors, measured during the Virgo Commissioning runs. Results are satisfactory for frequencies, while for quality factors indicate that thermo-elastic losses should be taken in account. Florence/Urbino     Then Florence/Urbino dedicated  to  silicon fibres, to include soon thermoelastic effects, and to methods for a fruitful modelisation of coatings, with aim to extract relevant parameters as the loss angle. 

16. Spherical Resonator Roma Tor Vergata The objective of the research is to demonstrate the feasibility of ultra-cryogenic spherical detectors. The scheduled milestone is to start data taking of MiniGrail, a solid sphere copper-aluminium detector with a mass of about 1 ton at the end of the second year. At the first run, the noise spectrum was taken and compared with the full electro-mechanical numerical model. The noise temperature was 70 mK and eight thermal peaks were identified without any unexpected resonances and spurious noise.         The observation by resonant antennae makes up for less sensitive frequency band by laser interferometers. The R&D of resonant antennae is of benefit also to cryogenic interferometers. Therefore, the importance of the R&D of resonant antennae does not reduce even though interferometric detectors attain better sensitivity at around 100 Hz. Also good point of the R&D of the resonant antennae is the cost effectiveness of the experiments, which makes small experimental groups enter this field. They may supply future good scientists working on gravitational wave research.

17. Wide band transducer (Dual Torus) Padova The objective of the research is to investigate the noise characteristic of the proposed wideband mechanical amplifier for the dual cylindrical detector. The mechanical amplifier realizes noise matching between a massive resonant antenna and a sensitive displacement sensor to produce optimised signal. The target is in three years to measure thermal noise of the mechanical amplifier at room temperature and to investigate contributed noises at a level of thermal noise. For this target, a mechanical amplifier prototype was designed and successfully analysed by ANSYS in the first year. And in the second year, its transfer function has been measured with a test oscillator. The research is only a part of the development of the dual cylindrical detector and the final result of this research will be tested in the future. However, STAC supports the activity of this group by the same reason as for 'Spherical detectors'.

18. Quantum noise LKB/ARTEMIS This experiment, with the objective to study both theoretically and experimentally the quantum noise in gravitational wave interferometers, continues to progress well. It is a collaboration of the Paris-LKB and Nice-ARTEMIS laboratories, and both sides are contributing to the effort. Recent progress involves the fabrication of a higher-finesse cavity, using mirrors coated by LMA; a finesse of 230 000 has been realized. An improvement in the frequency stabilization has been made.

19. Improvement of coatings Q and Corrective coatings LMA • Improvement of coatings Q LMA-Lyon • The report gives a clear and helpful description of the ringdown apparatus built by Perugia and with modifications by Lyon. Following the STAC recommendations of Fall 2004, a much stronger collaborative effort has been pursued, and the result is that the apparatus is now fully functional and capable of making measurements which can discriminate at the required level. The objective of the research has been met: Now it is possible to make a coating run and then, without removing the sample from the clean room where the coating was made, a definitive characterization of the mechanical loss of the coating undertaken. • Corrective coatings LMA-Lyon • The first three mirrors with Mexican Hat produced so far have been sent to Caltech for testing, to better learn about their appropriate construction procedure. A first simulation of the mirrors has been done and it looks rather promising.  The project, globally, sounds good.

20. Hollow Fibers ILGA Nice concentrated their R&D activities on studying the use of fibres as mode cleaners, activity encouraged by the STAC. They first positively checked the possibility of efficient laser-fibre coupling. Other tests showed that fibres do not add significant to frequency noise and at high frequency to amplitude noise. Problems with low frequency noise do not seem to be serious. Polarization noise is under study but in any case existing fibres do not preserve polarization. Collaboration with Limoges began on improving fibre quality (existing fibres are not single-mode). Also fibre end are very sensitive to dust. Various solutions of this problem are under study.

21. Interferometer Optimization Nice and ESPCI The R&D program consists in upgrading the two simulation codes and software systems developed in Nice and at ESPCI and in comparing the results of the codes. The Nice code has been upgraded and made more user friendly. First comparison between the Nice (DARKF) and ESPCI (NV) codes have been performed pointing towards bugs that have been corrected. Preliminary studies of a flat mode interferometer are also on their way and turn out to be promising.

22. Absorption at 1.5 micron of Si ESPCI With their own CW laser, they have found a minimum absorption of 40 ppm/cm for slightly doped silicon crystals (P and N, with resistivity of the order of 1000 Ohm.cm). For VIRGO at low temperature (77 K and below) this is already better than silica for the thermal point of view (thermal lens effect), With the new laser provided byEGO the density of power in their experiment is about 40 GW/m2 (30 W peak power focused on a 30 micron spot) and, even with a new generation of antenna with a 1 kW source and an order of 1 MW in the arm, the density of power in VIRGO will be around 0.1 GW/m2. This will induce an extra absorption of a few hundredth ppm which is negligible.

23. The VESF fellowship program In Autumn 2004, in the framework of its R&D program, and in support of the Virgo-EGO Scientific Forum, VESF, EGO launched a program of fellowships open to European groups working on theory of gravitation interested in dedicating work to the sources of gravitational waves that may fall within the observational reach of Virgo and its possible upgrading. These fellowships were for up to 10 man-years for 2005 and for 2006 (and similar amounts for the following years, subject to the availability of funds). The durations of the fellowships was intended to be from a month to two years. The great majority are two-years. It was expected that fellowship holders would come periodically to EGO to illustrate the advancements of their work. 9 Conventions were drawn with groups of 4 European Countries: France, Greece, Italy, Spain

24. The approved VESF fellowship bi-annual program 2005-2006

25. Future call for R&D proposals The STAC – the EGO Scientific and Technical Advisory Committee - recommended that a White paper on R&D be completed by the Virgo collaboration in a timely way to be made available as part of the next call for proposals for research. The next STAC meeting, in the middle of October, is expected to give suggestions on the general targets for a new call for proposals in R&D. The STAC recommended already that the Fellowships be used creatively to draw groups to the Observatory, and engage them in a mix of commissioning, data analysis, and research targeting future developments. At the VESF executive board of last 2 September it was considered important to open a new a new call for proposals for a few fellowships in theoretical and DA studies. The EGO Council next November will decide on the when, how and how much for the development of EGO R&D program.