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), F.Ronga(LNF)

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 2002

EXPLORER has taken data continuously with 80% duty cycle and high sensitivity. The typical value of the noise temperature has been at the level of 1 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 . On August, 2002 an unexpected failure involving the cryogenic and the readout system, forced the interruption of the data taking and the start of extraordinary maintenance activities on the detector. EXPLORER was again ready to resume data taking on December, 2002.

NAUTILUS has operated continuously with a duty cycle near 80% until the start of the upgrade activities (spring 2002). The upgrade, completed on December, 2002, involved the tuning of the detector at 935 Hz frequency, to search for the possible gravitational wave signal coming from the pulsar remnant of SN1987a and the installation of a new readout system, including a new resonant transducer, to increase the detection bandwidth.

A synergic collaboration with the MINIGRAIL group, operating in Holland and aimed to deploy an ultracryogenic spherical antenna, has initiated for the readout system of the detector.

Main aspects of the data analysis activity were related to study of coincidences in the data produced by Explorer and Nautilus in the year 2001, to the study of the cosmic rays detected by NAUTILUS operating in the superconductive state and to the study of coincidences in the NAUTILUS and EXPLORER data with the gamma ray bursts detected by BATSE and BEPPO-SAX.

The level of fulfillment of the planned milestones for the year is the following:

Continuos data taking with Explorer at Teff<10 mK: 80% (due to the unexpected failure)

Continuos data taking with Nautilus at Teff<5 mK: 50% (upgrade completed on December 2002)

Milestones 2003

1 year of data taking with Explorer at a noise temperature less than 2 mK (subject to adequate funding for foreign mission) | 31-12-2003
1 year of data taking with Nautilus at a noise temperature less than 2 mK | 30-12-2003
Start of data taking with MINIGRAIL at a noise temperature less than 5 mK | 30-06-2003

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

Manpower: 22 physiscists (15.7 FTE). 12 technicians (7 FTE).

Budget for the Year 2003: 2.4% of the CSNII total budget

4. Publications in refereed journals (Year 2002): 13

5. Conference talks (Year 2002): 10

6. Number of undergraduate and doctoral thesis:

1 undergoing doctoral thesis

1 undergoing undergraduate thesis

7. Leadership roles and primary responsibilities in the experiment

- Spokeperson: Eugenio Coccia and Francesco Ronga.
- Other leading roles: Guido Pizzella 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.