Nicolo' Beverini

Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope

SUMMARY We propose an under-ground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a tri-axial laser detector of rotation. The proposed detector consists of six large ring-lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6

MEASUREMENT OF THE CALCIUM 1P1-1D2 TRANSITION RATE IN A LASER-COOLED ATOMIC-BEAM

m

Measurement of the atmospheric muon flux with the NEMO Phase-1 detector

side, assuming a shot noise limited sensitivity (

The Data Acquisition and Transport Design for NEMO Phase 1

20 prad/s/\sqrt{Hz}

Buffer gas pressure shift in the mF = 0 → mF = 0 ground state hyperfine line in Cs

). The multi-gyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedron structures. The symmetries of the proposed configurations provide mathematical relations that can be used to study the stability of the scale factors, the relative orientations or the ring-laser planes, very important to get rid of systematics in long-term measurements, which are required in order to determine the relativistic effects.

A LASER GYROSCOPE SYSTEM TO DETECT THE GRAVITO-MAGNETIC EFFECT ON EARTH

The efficiency of laser cooling in a thermal beam of calcium has been investigated under different cooling schemes. Special attention has been paid to analysis of the loss factor represented by the decay of atoms excited by the cooling laser to the 1P1 state into the metastable 1D2 level. The cooling scheme at a fixed laser frequency makes possible a good estimation of the branching ratio R between the decay probability from the 1P1 level to the ground 1S0 state and to the metastable 1D2 state. The measured value of (1.0 ± 0.15) × 105 seems high enough to produce only a small reduction in the cooling efficiency.

Solid-state power supply for gas lasers

Abstract The NEMO Collaboration installed and operated an underwater detector including prototypes of the critical elements of a possible underwater km3 neutrino telescope: a four-floor tower (called Mini-Tower) and a Junction Box. The detector was developed to test some of the main systems of the km3 detector, including the data transmission, the power distribution, the timing calibration and the acoustic positioning systems as well as to verify the capabilities of a single tridimensional detection structure to reconstruct muon tracks. We present results of the analysis of the data collected with the NEMO Mini-Tower. The position of photomultiplier tubes (PMTs) is determined through the acoustic position system. Signals detected with PMTs are used to reconstruct the tracks of atmospheric muons. The angular distribution of atmospheric muons was measured and results compared to Monte Carlo simulations.

Fiber laser strain sensor device

The NEMO collaboration proposes to build an underwater neutrino telescope located South-East off the Sicily coast. This paper describes the concepts underlying the communication link design going over the whole data acquisition and transport from the front-end electronics to the module sending data on-shore through a fiber optic link which relies on Dense Wavelength Division Multiplexing. An on-shore board, plugged into a PC, extracts and distributes data both to first-level trigger and control systems. Underwater apparatus monitoring and controls are guaranteed by oceanographic instruments and dedicated sensors, whose data are packed and sent back to shore using the same optical link. The communication is fully bidirectional, allowing transmission of timing and control commands. The architecture described here provides a complete real-time data transport layer between the onshore laboratory and the underwater detector. During winter 2006 a first prototype of the apparatus has been deployed: calibration results from the currently working system are here reported.

Gaussian envelope for 3D geomagnetic data inversion

Abstract The pressure shift of the mF:0 → 0 microwave transition of the cesium ground state has been measured for seven buffer gases (He, Ne, N2, CH4, C2H6, C3H8, C4H10). The high resolution of the experimental apparatus (about one part in 1011 also allows an accurate measurement of the temperature dependence of the shift.

Controlling the non-linear intracavity dynamics of large He–Ne laser gyroscopes

Large scale square ring laser gyros with a length of four meters on each side are approaching a sensitivity of . This is approximately the regime required to measure the gravito-magnetic effect (Lense–Thirring) of the Earth. For an ensemble of linearly independent gyros each measurement signal depends upon the orientation of each single axis gyro with respect to the rotational axis of the Earth. Therefore at least three gyros are necessary to reconstruct the complete angular orientation of the apparatus. In general, the setup consists of several laser gyroscopes (we would prefer more than three for sufficient redundancy), rigidly referenced to each other. Adding more gyros for one plane of observation provides a cross-check against intra-system biases and furthermore has the advantage of improving the signal-to-noise ratio by the square root of the number of gyros. In this paper we analyze a system of two pairs of identical gyros (twins) with a slightly different orientation with respect to the Earths axis. The twin-gyro configuration has several interesting properties. The relative angle can be controlled and provides a useful null measurement. A quadruple twin system could reach a 1% sensitivity after 3.2 years of data taking, provided each square ring has 6 m length on a side, the system is limited by shot noise and there is no source for 1/f-noise.