1. Experimental base of the United Experimental laboratory for Gravitational-Optical Investigations (UELGOI).

The main experimental base of UELGOI is presented by the located in FSPC SIAO specialized compartments, equipped with any necessary facilities: lasers, high-reflective mirrors, polarizing prisms, hologram diffraction gratings, piezoelectric cells, phase modulators, multichannel analyzers of spectral information, photodetectors, radio and optoelectronic devices and computers.

All the investigations are performed in the specialized experimental cage (EC), placed in the underground laboratory (UL) at the depth 12 m from the ground level, what provides minimization of the vibration background effect and reduction of the temperature stabilization problem. The laboratory walls and the flour are displaced in the all-metal chamber, which is rested on the sand cushion and dampproof from the wall sides. The laboratory has technical underground with depth 2 m from the flour level, which serves for installing the foundations of the main equipment of UL as well as for displacing the electric communications and systems of power supply of the main equipment. Experimental cage consists of two departments, one containing another. In the internal compartment all the high-sensitive devices including the developed two-resonator laser system are mounted on the special foundation, which, in its turn, is vibroisolated from the room foundation. The foundation represents the ferroconcrete block of 100 tonn weight and is vibroisolated by means of the spiral car springs. The equipment is additionally vibroisolated by means of various special vibration isolators.

To provide necessary temperature conditions the three-stage system of thermal stabilization is incorporated. the first stage is provided with conditioner, which warms the air flow, coming as an influent ventilation to UL, and keeps the temperature within the limits ±0.250C from the set nominal value. The second and the third stages are provided with specially developed independent system of temperature stabilization. At the second stage the temperature in the external room of the compartment is stabilized within tenths degree from the nominal value, and at the third one the temperature in the internal room of the compartment is correspondingly stabilized within hundredths degree.

2. Passive variant of GW-detector.

The first step in realizing the complex programme of gravitational experiments on "Dulkyn" project was the construction of passive variant of GW-detector on the basis of pentagonal ring two-contour interferometer, which optical radiation source being out of it.

The pentagonal interferometer, operating at the wave length 0,63 mm, was mounted and adjusted on the polished round glass plate of 10 cm thickness and with diameter 65 cm, the pentagonal side being 30 cm, in December of 1995. The following technical problems were solved in the course of test experiments on the passive interferometer:

1. The original procedure of adjusting the complex two-contour pentagonal optical resonator built on the common optical elements, two of them being holographic diffraction gratings custom-made in the UELGOI, was developed. The experiments, performed in a strong mechanical disturbances environment, demonstrated that pentagon as a two-contour optical configuration was stable and there was no need in additional monitoring the adjustment. The requirements to the degree of identity of the first and the second holographic reflective elements were determined. The considered procedure was totally used when constructing the active variant of GW-detector which is pentagonal two-resonator laser system.
2. Various schemes of forming the interference pattern at the detector output are tested as well as corresponding procedures of processing the interference pattern; the interferometer duality and possibility of creating two informational channels are maximally used. The developed and proved computer algorithms were entirely used in the active variant.
3. The system of correlative self-cancellation of disturbances (SCSCD) is designed and tested in real disturbances and noises environment. For the passive interferometer variant the SCSCD sensitivity threshold is determined. The conclusion is made that this SCSCD version could be used for the primary rough filtration of strong correlated disturbances.
4. The original system of stabilizing the phase difference of optical radiations in the first and the second pentagonal contours is created and proved, which allowed to decrease by several orders of magnitude the phase noise in the low frequency range.
5. In the infra-low-frequency range 10^-5 - 10^-1 Hz (operating band for the detectors of periodic gravitational radiation from the binary relativistic astrophysical objects) the phase noise actual spectral density (stochastic component of the phase difference of the interferometer first and the second channels ) is investigated. With a view to it a series of continuous long-term measurements was performed with the switched-off and switched-on stabilization system. The spectral curves for the nonreduced and reduced noises are respectively obtained.
6. A series of experiments with analogous and digital GW effect simulation is performed. The periodic signal of an amplitude 10-4 - 10-6 rad was delivered to the signal contour, where it was mixed with actual disturbance signals (with operating and switched-off stabilization system), and then it was extracted from the output signal by means of the expressly developed threshold algorithm. For the passive interferometer the relationships are obtained for the signal amplitude, stabilization threshold and nonreduced noise level, at which the simulated periodic noise 'recognition criterion' is fulfilled.
7. The periodic signals intraperiodic and interperiodic accumulation procedures are developed and tested, providing reliable extraction of a weak low-frequency friendly signal on the background of great disturbances.
8. An integrated test of availability of the total operational cycle of 'simulation-recognition' of periodic signal at the infra-low frequency was performed in automated mode with cycles duration from 2 to 8 days.

3. Active-type GW-detector.

The second step in realizing the 'Dulkyn' project is the creation of a prototype of GW detector active variant that is the compact two-resonator laser system.

In summer of 1999 two-resonator laser systems of pentagonal ring configuration (running waves) [2] and of triangle linear configuration (standing waves) [6] were built and adjusted. Using these schemes, stable lasing at the wavelength 3,39 mm was obtained.

All the optical elements, forming a specific two-resonator laser system, were rigidly fixed on a single basement. For the pentagonal resonator configuration the plate basement was used, made of thermally treated to stabilize its dimensions aluminum alloy D 16 (its weight is 400 kg), its diameter and thickness being 1,4 m and 8 cm correspondingly. Thermal treatment included four regimes of heating and cooling at various temperatures to remove all the internal strains in metal.

At present time the GW-detector active variant prototype is used to adjust and debug servosystems of frequency and phase stabilization of generated optical radiation.

4. Vacuum chamber.

The specialized vacuum chamber (VC) with diameter 1,7 m and height 0,67 m (550 kg weight) is fabricated, designed to isolate outside the two-resonator laser system. The residual pressure inside the vacuum chamber does not cross the level 10^-3 torr.

The two-resonator laser system plate basement rests inside the VC on three bearing supports, displaced at the corners of a proper triangle and distant from the plate centre by 2/3 of its radius.

5. Preparation to performing of calibration for GW-detector the first level of imitation signal (“Lunar test”).

The following work was fulfilled after restarting of funding since February 2006 till March 2007:

• calculations were performed for theoretical provision of experiment on calibration of GW-detector and testing of its construction conception by realization of Einstein's equivalence principle at lunar-solar variations of geo-potential. Theoretical substantiation of Lunar test is published in two leading Russian scientific journals “Gravitation and Cosmology” and “Journal of Experimental and Theoretical Physics”;
• Specialized vacuum chamber (VC) with diameter 1.7 m and height 0.67 m (mass 550 kg) is tested. It is designated for isolation of double-resonator laser system (DLS) from surrounding medium. The rest pressure inside chamber is not higher 10-3 Torr. The basement plate of DLS lays freely inside VC on three bearings situated in tops of regular triangular with offset 2/3 of its radius from the center of plate;
• modification of forevacuum system is performed with the goal to optimize the work of vacuum pumps during long time of continuous GW-detector operation;
• upgrading of mechanical DLS units is done by the results of preliminary testing;
• technical requirements are developed for specialized gas discharge tubes (active elements for DLS) with feeding units and ballast resistances;
• current noises of active elements are investigated; it is determined that the level of noises satisfies technical requirements;
• the simultaneous generation is obtained at the wavelength 3.39 ?m in the reference and signal resonators of DLS; generation regimes of DLS are investigated, concurrence of magnitudes is eliminated for difference frequency in all range and for generation frequency offset form line center of active element;
• precision mono-block stabilized He-Ne/CH4 laser is acquired and introduced into exploitation; it provides high accuracy and high stability as an optical standard of frequency;
• stabilization system (SS) and system of frequency-phase auto-tuning (SFPA) is checked by etalon frequency standard;
• coupling of SS and SFRA with DLS of triangular configuration is performed inside vacuum chamber;
• specialized system is developed and fabricated for measurement of output DLS signals;
• precision phase modulator (PM) is developed and fabricated for the imitation of useful signal with the goal of performing calibration of GW-detector “Dulkyn”; scheme is created for the control of turning angle of FM and operation ability of FM is checked at the turning angles in the range of 1?0.001 angular seconds with oscillation periods from 0.5 hour to 6 hours during 14 days;
• additional units of computer-electronic equipment are acquired and mounted into units and blocks of GW-detector;
• regime of synchronization is got for reference and signal resonators of DLS with simultaneous binding of reference resonator generation frequency to frequency of mono-block stabilized He-Ne/CH4 laser; the possibility is checked for detection of periodic signal imitated by FM in the signal resonator of DLS at the work within locking zone;
• temperature and pressure sensors are mounted inside vacuum chamber; works are fulfilled on the coupling of electro-communications of DLS through the connections of vacuum chamber;
• works are started on the creation of information-technical provision of subsequent (after “Lunar test”) experiments;
• setup is ready to the start of performing “Lunar test” (duration of experiment is 6 months).

6. Results of “Lunar Test” experiment.

Long-term continuous “Lunar Test” experiment has started on 8th of September 2008 and successfully accomplished on 5th of March 2009 by Scientific Center for Gravitational Wave Research (SC GWI) of Tatarstan Republic Academy of Sciencies. Its performance had confirmed the validity of concept for the construction of gravitational wave detector “Dulkyn” and highlighted accomplishing the first of three successive stages of low frequency gravitational detector creation.

Performance of “Lunar Test” is the result of theoretical, design and experimental work during more than 15 years effort of the whole set scientific collectives and leading enterprises: AS RT SC GWI “Dulkyn”, KGU, FGUP NPO GIPO, ннн “FITRAN” etc.

The success of scientific collective is certified: the diploma and golden medal were acquired by the results of scientific “Dulkyn” presentation at the international exposition of innovations in Brussels in 2005.

While performing the 1st phase (“Lunar Test”) of the III (final) stage of scientific-technical project “Dulkyn” the following tasks were accomplished:

• all necessary works on the creation of the first level detector “Dulkyn-1” (mounting, assembling, tuning and testing of all detector nodes and systems) were carried out;
• conditions were secured for round-the-clock steering of apparatus operation and for the recording phase, temperature and pressure variations;
• long-term experiment on the calibration of “Dulkyn-1” detector and the acquisition experimental data base for testing Einstein's equivalence principle was started on 8th of September 2008;
• calibration of “Dulkyn-1” detector was carried out, linearity of the detector response was proved for the influence of periodic signals in the whole operation frequency range;
• spectrum of “Dulkyn-1” detector phase noise was acquired;
• long-term experiment “Lunar Test” was successively accomplished on the 5th of March 2009 with preservation of operation ability for all units and nodes of “Dulkyn-1” detector during six months of continuous round-the-clock exploitation.

Summarizing the results of the unique experiment “Lunar Test”, it is necessary to point out that all goals and tasks of the 1st phase of science-technical project “Dulkyn” ь (final) stage are achieved.

Calibration problem of “Dulkyn-1” - extraction of calibration signals in the predetermined infra-low range - is completely fulfilled. Operation ability of detector and all supplementary equipment during many months is proved.

The achieved sensitivity of “Dulkyn-1” detector that is 10^-12 - 8*10^-16 in the frequency range 10^-5 - 1 Hz, corresponds to values necessary to detector of the first level and is unique in the world for this infra-low frequency range in present time (up to the launch in 2015 of international space project LISA).

Einstein's equivalence principle is checked (for universality of gravitational “red” shift law for clocks of various physical nature) at the level of 0.9% that is twice higher than the best world achievement (1.7% - USA, 1983)! The experiment of such a kind was performed for the first time in Russia (and former USSR).

The construction conception validity was confirmed for GW detector “Dulkyn”, which elasto-dynamic response is calculated on the basis of G. Mozhene approach corresponding to the value of phenomenological parameter ξ=1 in contrast to alternative approach of J. Weber (ξ=0), since experimental value got at the testing of equivalence principle was ξ=1±0.009.

In whole, successful accomplishing of “Lunar Test”, reach material and experience accumulated during its conduction inspire confidence in fast successful accomplishing of 2nd and 3rd phases tasks for “Dulkyn” project which final goal is the creation of gravitational wave detector and the beginning of astrophysical research in the field of gravitational wave astronomy.

In the case of science-technical project ”Dulkyn” funding prolongation, the fulfillment of the project 2nd phase will be started that is creation of the second level detector “Dulkyn-2” with a sensitivity three orders higher than that of “Dulkyn-1”. Supposed time of detector “Dulkyn-2” creation and calibration is 3 years.

The final goal is the construction of the third level detector “Dulkyn-3” with sensitivity three orders higher than “Dulkyn-2”, i.e. the creation of real gravitational-wave detector capable to discover low-frequency gravitational radiation from double astrophysical objects. SC GWI “Dulkyn” is open to the collaboration with scientific and commercial organizations that are interested in the prolongation of this work.