ROG

Collaboration:

- Laboratori Nazionali di Frascati, Univ. of Rome "La Sapienza" and INFN/Roma1, Univ. of Rome "Tor Vergata" and INFN/Roma2, IFS Rome and INFN LNF and Roma1, Univ. L'Aquila and INFN

Laboratory: CERN and LNF

National Responsible: E. Coccia (Roma2)

1. Goal of the experiment

ROG (the acronym stands for Ricerca Onde Gravitazionali – Gravitational Wave Research) is a collaboration which has designed and constructed two massive (M=2.3 tons) cryogenic resonant bar detectors: EXPLORER, cooled at 2 K, in operation at CERN since 1990, and NAUTILUS, cooled at the record temperature (for such massive bodies) of 0.1 K, in operation at LNF since 1995.

The goal is the detection and study of gravitational wave signals emitted by high frequency (kHz) cosmic sources, such as gravitational collapses with formation of neutron stars and black holes, coalescing binaries, fast pulsars and a stochastic background.

More on the experiment…

2.

Activities during 2001

The EXPLORER detector has taken data continuously with 80% duty cycle and high sensitivity. The typical value of the noise temperature has been between 2 and 3 mK. The strain sensitivity has been of about 2x10-21 Hz-1/2 with a bandwidth of about 10 Hz.

The bandwidth is of about 40 Hz at a strain level of 10-20 Hz-1/2 . This result demonstrates that the bandwidth of resonant detectors can be increased.

NAUTILUS has operated continuously during all the year, with a duty cycle near 80%.

The detector is equipped with a cosmic ray telescope, and was capable to detect signals due to the interaction of EAS on the bar. In order to investigate the unexpected energetic signals detected last year, during 2001 NAUTILUS was operated at a thermodynamic temperature of1.5 K, above the superconducting transition temperature of the bar material.

We remind the reader that the detection of cosmic rays with NAUTILUS means being able to measure impulsive signals exciting the mode of vibration to an energy of 10-7 eV.

A new readout system including a new resonant transducer, has been prepared for the next NAUTILUS run, when the detector will be tuned at 935 Hz frequency to search for the possible gravitational wave signal coming from the pulsar remnant of SN1987a.

All the planned milestones have been fulfilled:

Continuos data taking with Explorer at Teff<10 mK

Continuos data taking with Nautilus at Teff<5 mK

Milestones 2002

EXPLORER: continuos data taking with Teff<5 mK and cosmic ray detector | 30-06-2002
NAUTILUS: continuos data taking with Teff<1 mK and detector tuned on pulsar of the SN1987A | 30-06-2002

3. INFN contribution to the experiment in terms of manpower and financial support

Manpower: 26 physiscists (16.6 FTE). 11 technicians (6.5 FTE).

Budget for the Year 2002: 339 kEuro.

4. Publications in refereed journals (Year 2001): 3

5. Conference talks (Year 2001): 9

6. Number of undergraduate and doctoral thesis:

2 Laurea diplomas.

7. Leadership roles and primary responsibilities in the experiment

- Spokeperson: Eugenio Coccia, member of the GWIC (Gravitational Wave International Committee).
- Other leading roles: Guido Pizzella and Francesco Ronga at LNF, Giovanni Vittorio Pallottino at Roma1, Ivo Modena at Roma2.

8. Innovative instruments

- High coupling capacitive transducer for the measurements of small mechanical vibrations.
- Dc SQUIDs of very low noise. Record energy resolution of 5.5 hbar.
- Largest 3He- 4He dilution refrigerator in the world, developed in collaboration with Oxford Instruments.

9. Competing experiment

- Operating detectors (resonant bars): AURIGA at INFN-LNL, ALLEGRO at Louisiana State University (USA) and NIOBE at University of Western Australia (Australia).
- Formal collaboration agreement for joint coincidences analysis has been established with these groups (IGEC = International Gravitational Events Collaboration).
- Interferometric detectors: TAMA (in Japan, just starting the data taking). Others detectors will start operating in the next years: GEO (Germany), LIGO (USA), VIRGO (Italy).

10. International committee which has reviewed the experiment

- EXPLORER is a CERN Recognized Experiment (RE5) and follows the CERN policy.
- NAUTILUS results are reported regularly to the LNF Scientific Committee.