Birth and development of the experiments searching for gravitational waves

1. Birth and development of the experiments searching for gravitational waves Guido Pizzella Istituto Nazionale di Fisica Nucleare Laboratori Nazionali di Frascati

2. SEARCH FOR GRAVITATIONAL WAVES • General Relativity • Sources of gravitational waves • Beginning of GW experiments in Italy • Experiments • Resonant detectors • The contribution of the Rome group to the search for gravitational waves g.pizzella

9. Measurement of h

10. GENERATION OF GRAVITATIONAL WAVES

11. pulsars h = 10-27

12. chirp

16. Joe WeberUniversity of Maryland • He developed the first gravitational wave detectors (Weber bars) in the 1960s and published papers with evidence that he had detected gravitational waves. • This evidence has not been confirmed by other experiments EGO-Pizzella

17. Search of gravitational waves in RomePersonal recollections • During the sixties Amaldi tried to push the Italian physicists in the direction of researches in the birth phase: • Infrared Background and Gravitational Waves (after Weber’s experiments). • I was Amaldi’s assistant and I wanted to change my activity from space research to a more fundamental field.  EGO-Pizzella

18. On September 3rd 1970, coming back from a period spent in the USA (where I was studying the Van Allen belts with space probes), I proposed to Amaldi to make an experiment for the search of gravitational waves. • He agreed. This date marks the beginning of the GW search in Italy. EGO-Pizzella

19. What kind of experiment ? • With Renzo Marconero we visited in England the groups of W.D.Allen at the University of Reading and of P.S.Aplin in Bristol, who were constructing room temperature Weber type detectors, but it was immediately clear that these experiments would have never reached a good sensitivity. • We had meetings in Rome with Bruno Bertotti, Nicola Cabibbo and Bruno Touschek, discussing the Weber results and the possible techniques to employ for a new experiment. EGO-Pizzella

20. Interferometers • On 2 June 1972 during a Conference in Cambridge (USA), R.L.Forward, former PhD student of Weber, presented his results obtained with a 2m long interferometer, in the frequency range 1.6 to 24 kHz with a sensitivity of the order of h ~ 10-18 Hz-1 , playing a magnetic tape where he had recorded the data, so people could listen a whistle due to the interferometer signal (The voice of gravitational waves, he said). • On 7 December 1972, I received a circular letter by Forward addressed to all people searching for GW or interested in searching for GW, proposing to compare lists of events for the search of coincidences. EGO-Pizzella

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22. After the visit in England I had not made my mind yet what kind of experiment we should have aimed to, until in January 1971 Amaldi received confidentially from Remo Ruffini the Stanford and Louisiana proposal for a detector consisting in a 5 ton aluminum bar cooled to very low temperature (0.003 K), suspended magnetically and employing a dcSQUID amplifier coupled to a resonant transducer. • It was clear that this was the kind of experiment we should have aimed to realize. EGO-Pizzella

23. A collaboration then started among Louisiana, Rome and Stanford for the construction of three 5-ton cryogenic detectors, cooled to 0.003 K, to be installed in the three locations. EGO-Pizzella

24. We needed a laboratory where to develop the cryogenic detector. I suggested Frascati where I had already worked in 1956 and where cryogenic techniques were available.  • Amaldi on 22 February 1971 called a meeting with the Frascati director, who said to be interested.  • However, when next day I visited the Frascati Laboratory, I realized that the interest was only in words EGO-Pizzella

25. At the University of Rome Giorgio Careri was making experiments with liquid helium. In the late sixties he was the Director of the Nuovo Pignone Laboratory of the ENI group at Monterotondo, near Rome. • He proposed to install the large cryostat, made with Aluminum, in this Laboratory, after an agreement with ENI. The cryostat was delivered in the spring of 1974 and we started to make the initial tests with liquid nitrogen. EGO-Pizzella

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27. In Germany • Ludwig Biermann, President of the Max-Planck Physical Society, on 1 June 1974 visited us at the SNAM-Progetti in Monterotondo. • The Germans had made an experiment with two Weber type detectors located one in Frascati (ESRIN) and the other one in Munich with null result, but they wanted to continue in this new field of physics. • We showed Biermann the EXPLORER cryostat we were assembling. He was very impressed and concluded that we were to much ahead with the cryogenic resonant bars. • He said the German group would have been better to continue the search for GW with a different technique, say with interferometers. • The decision was taken in Germany to start with a 3 m long interferometer prototype EGO-Pizzella

28. In the following years our experiment went on with changing fortunes and, after leaving the SNAM Projects and after a further attempt to go to Frascati, then unavailable for political reason, we landed in 1980 at CERN, very well received, where finally we realized the cryogenic antenna EXPLORER cooled to 2 K. This antenna has worked continuously until 2010. In the years 1991-1998 it was the most sensitive detector in the world (with NAUTILUS since 1996). In 2010 the collaboration with CERN was terminated. EGO-Pizzella

29. CERN When I proposed to Amaldi to go to CERN he stared at me and said: Are you sure ? CERN is a big Center and it is possible that they will take over. My reply: if they do, much better for the experiments itself. EGO-Pizzella

30. Impact of our activity in Italy on the gravitational waves experiments EGO-Pizzella

31. On 16 July 1982 (at the time we were assembling our first detector, EXPLORER), we had a visit by Richard Isaacson, in charge of the NSF funds for all types of gravitational wave experiments. • Isaacson was very much impressed by our experiment and he wrote to me the following letter: EGO-Pizzella

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33. He also told me that since the Rome group was very much ahead with the resonant detectors it would have been a good policy in U.S. to speed up the LIGO program which was just in the initial phase…. • …and so he did, going back to the USA. EGO-Pizzella

34. In 1991 I was asked by Vogt, Weiss and Thorne to write to the U.S. senator Mikulski supporting the LIGO project. • I did it, the only word of caution I had, in this case, was that, in my opinion, the project would have taken longer than envisaged. EGO-Pizzella

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36. VIRGO e Adalberto Giazotto In 1985 Adalberto took the decision to switch from particle physics to General Relativity. He had a very clear idea: he wanted to be able to detect GW emitted by the pulsars, in particular by the CRAB pulsar(60.4 Hz) and by the VELA pulsar (22 Hz). We collaborated for a few months trying to find out how to use a bar detector for such a goal. EGO-Pizzella

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38. But, it was soon clear that the use of bars was not the best one for the search of low frequency GW… • ….and VIRGO had birth. EGO-Pizzella

39. When I was asked to give my opinion about VIRGO at an INFN meeting in L'Aquila in 1987, in presence of Adalberto Giazotto and Alain Brillet, I said I was in favor, although I think it was a big error by the European scientific community to decide to construct just one detector, and not two, as in the case of LIGO. EGO-Pizzella

40. Interferometers or resonant bars ? After the year 2005 interferometers became more sensitive to GW The bars are also sensitive to the passage of particles EGO-Pizzella

41. The resonant bar experiments in Italy. EGO-Pizzella

42. CERN

43. Going to the Frascati Laboratories: NAUTILUS • On December 5, 1989 suddenly Edoardo Amaldi, the Sower of the Italian Physics, passed away. A few days later, on December 18, I was in my office at the University La Sapienza in Rome, when I received a phone call from Enzo Iarocci. Enzo, who was to become director of the LNF from January 1, 1990, was proposing to bring the NAUTILUS detector under construction at CERN in the Laboratories of Frascati, were liquid helium liquefiers were available. NAUTILUS was under construction at CERN because this was the only lab available for our group, but the idea was to carry NAUTILUS in another place as soon as the construction was over, in order to be able to study events in coincidence between two detectors installed in far away places. EGO-Pizzella

44. NAUTILUS INFN - LNF

45. NAUTILUS Frascati

46. AURIGA • On 10 November 1988 I had a meeting with Massimo Cerdonio (who had become professor in Trento and later in Padua). • I convinced Massimo to came back (after 17 years) to the GW research by installing a new detector, similar to NAUTILUS, near Padua: AURIGA. • (An attempt to install another detector at he University of Lecce failed). EGO-Pizzella

47. AURIGA Padova

48. Cryogenic bar detectors in the world EGO-Pizzella

49. Stanfordthe founder of cryogenic detectors EGO-Pizzella

50. Bar Network Massimo Cerdonio