• DEVELOPMENT OF RESONATORS BASED ON VIBRATING STRING
• EXPERIMENTS BASED ON RESONATOR WITH VIBRATING STRING
• SENSORS BASED ON RESONATOR WITH VIBRATING STRING

RESEARCH INTO RESONATORS BASED ON VIBRATING STRING

The category of sensors based on the vibrating string as the resonance sensible element is widely used in control and measuring systems, as well as in experimental physics. Resolution of specific technical problems (string fixing methods, methods of limitation the parasitic degrees of freedom, methods and approaches for generating of oscillations) allowed to reach the utmost currently received specs for stability and sensibility of resonators. The long-term relative stability (about few days) is better than 10^-5. The relative sensibility is about 10^-6. The resonator based on vibrating string with above-mentioned specs was used as the basis for development of wide range of sensors and accomplishing a number of experiments.
 

SENSORS OF TENSION

A sensor of tension was the resonator based on vibrating string with an end of the string being loose in longitudinal direction.
 

THERMOGRAVIMETRIC INSTALLATION

For thermogravimetric experiments, the sensor of tension was used as the mass sensor in high temperature ovens. The mass deviations were caused by a number of complex physical and chemical processes. The range of measurements was from 50 to 500 grams. Measurement accuracy was 0.2 mg. The entire installation for thermogravimetric measurements included:
- vacuum-pumped (adjustable) high temperature oven for heating up to 1,700 degrees of Celsius;
- mass sensor with the unit for autogeneration and multiplication of frequency;
- PC interface card;
- PC software including a feature for assigning and controlling the oven temperature and the oven temperature scenario correcting system based on the results of gravimetric measurements.
 

ACCELEROMETRIC SENSORS

 

DISPLACEMENT SENSORS 

Frequency bias of the resonator with vibrating string arised when the length of the string was changed was used for measuring of the displacement 
The thermal strain and deformation displacements in typical concrete buildings were studied (points of control were on floor and ceiling). When a mass of less than 10 kg have been moved, the reproducible frequency bias of sensor have been observed. The equivalent displacement of the end of the string was about 2 - 3 nanometers.
 

GEOPHYSICAL MEASUREMENTS 

A displacement sensor has been used for geophysical research purposes in the salt mine, Yerevan in December 1998 through February 1999.
 

MAGNETOMETRIC MEASUREMENTS (SPACE DISTRIBUTION OF MAGNETIC FIELD GRADIENTS)

The tension sensor with magnetosensible specimen has been used as a sensing element in the magnetic field under test. The permanent magnets (magnetic field gradiometers) or "soft-magnetic" materials were used as specimens. In comparison with traditional methods for magnetic field measuring (the Hall sensors), the mentioned approach had a advantage of forming the noise-free frequency signal and providing direct measuring of magnetic field gradients.
 

CRYOGENIC INSTALLATION FOR MEASURING OF MAGNETIC PROPETIES OF MATERIALS

The measurements of the interaction of a specimens with unknown magnetic properties in known magnetic field allow measuring the magnetic properties of materials.
The cryogenic installation for analyzing the properties of high-temperature ceramics has been assembled. This enabled to research the magnetic properties within a range of nitrogen and helium temperatures.
 

SENSORS OF CROSS-SECTION PROFILE OF BEAMS IN ACCELERATORS

The proposal for scanning the beams in accelerators by using a vibrating string approach has been developed. An important advantage of this method in contrary to the traditional scanning methods was in eliminating of the unit for measurement of particle or radiation dispersed on a vibrating string. The "Designing and researching the sensors based on a vibrating string for accelerator beam diagnostics and thermogravimetry" project has been awarded with a grant ISTC of the Program on Conversion.
 

ULTRA-LOW TEMPERATURE THERMOMETER 

An application of resonators based on a vibrating string in ultra-low temperature thermometry is practically the only method of measuring the temperatures below 400 microK. The U-shaped loop resonators based on elastic superconductive wire were in use traditionally. The using of resonators based on the straight string with fixed ends has allowed improving the resonator’s Q-factor essentially. This enabled to figure out an increasing the resolution limit of the method.
 

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