Coincidences among the data recorded by the baksan, kamioka and mont blanc underground neutrino detectors, and by the Maryland and Rome gravitational-wave detectors during Supernova 1987 A

Summary The data recorded with the neutrino detectors at Mont Blanc, Kamioka, Baksan and with the gravitational-wave detectors in Maryland and Rome have been analysed searching for correlations associated with SN 1987 A, without presuming or excluding hypotheses for correlations due to neutrinos and gravitational waves. The statistical analysis has been based on a previous analysis that showed a correlation among Maryland, Rome and Mont Blanc with a probability to be accidental less than 10⁻⁵. Independent correlations are found during a period of one or two hours, around the Mont Blanc 5ν burst (2h 52 min 36 s UT), among the various sets of data: Mont Blanc-Baksan with a probability to be accidental of the order ofp∼4·10⁻³, Mont Blanc-Kamioka withp∼4·10⁻³, Maryland-Rome-Kamioka withp∼5·10⁻⁴, Maryland-Rome-Baksan withp∼5·10⁻². It is remarkable that the events from all the neutrino detectors follow the signals from the g.w. detectors by a time of the order of 1/2 or 1 s. At present we will not give a physical interpretation of the observed correlations which have strong statistical significance. Professor Edoardo Amaldi died on December 5, 1989.     

Correlation between gravitational-wave detectors and particle detectors during SN1987A

Summary A review of the correlations between gravitational-wave detectors and particle detectors during SN1987A is given. The correlation between the Maryland and Rome g.w. detectors with the Mont Blanc neutrino detector is illustrated. This correlation extends during a period of one or two hours centred at 2∶45 UT of 23 February 1987, with the ?neutrino? signals delayed by (1.1±0.5) s and with a probability of the order of 10⁻⁵ to be accidental. Using the data obtained with the Kamiokande and IMB detectors, with the same statistical choices and procedures for the data analysis used previously, the above result is confirmed with a probability of the order of 10⁻³ or 10⁻⁴ that the additional correlation be accidental. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Study of fission track registration efficiency of γ-irradiated polyester track detector in solution medium

The fission track registration efficiency (K _wet) of the Garware polyester track (GPF) detector in solution has been determined with respect to the Lexan detector whose K _wet is very well known in the literature. The K _wet is found to be (1.2 ± 0.1) 10⁻³ cm. The track registration efficiency of the GPF detector in solution is better than the efficiencies of other nuclear track detectors reported in the literature. This implies that the threshold energies for track registration are different for different detectors and that GPF detector has a lower threshold-energy value. The effects of gamma irradiation in the dose range of 5–51 Mrad on the fission track registration efficiency (K _wet) of this track detector from the solution medium are also investigated. The results show that the K _wet values for the gamma-irradiated detectors in the above dose range in 2M HNO₃ solution medium decreases by ∼7–15%. The changes induced in the gamma-irradiated detectors as a function of gamma dose have also been studied by bulk-etch rate measurements.     

Silicon detector technology development in India for the participation in international experiments

A specific research and development program has been carried out by BARC in India to develop the technology for large area silicon strip detectors for application in nuclear and high energy physics experiments. These strip detectors will be used as pre-shower detector in the CMS experiment at LHC, CERN for π ⁰/λ rejection. The fabrication technology to produce silicon strip detectors with very good uniformity over a large area of ∼40 cm², low leakage currents of the order of 10 nA/cm² per strip and high breakdown voltage of >500 V has been developed by BARC. The production of detectors is already under way to deliver 1000 detector modules for the CMS and 90% production is completed. In this paper, research and development work carried out to develop the detector fabrication technology is briefly described. The performance of the silicon strip detectors produced in India is presented. The present status of the detector technology is discussed.      

Search for β-delayed fission of the heavy neutron-rich isotope 230Ac

The ²³⁰Ra has been produced via multinucleon transfer reaction and dissipative fragmentation by 60 MeV/u ¹⁸O ion irradiation of ²³²Th targets. The radium was radiochemically separated from the mixture of thorium and reaction products. Thin Ra sources were prepared and exposed to the mica fission track detectors, and measured by a HPGe gamma detector. It is likely that the β-delayed fission of ²³⁰Ac was observed for the first time and the β-delayed fission probability of ²³⁰Ac was tentatively found to be (1.19±0.40)×10^-8. Received: 2 November 2000 / Accepted: 30 January 2001     

Bound on induced gravitational wave background from primordial black holes

The today’s energy density of the induced (second order) gravitational wave background in the frequency region ∼10⁻³–10³ Hz is constrained using the existing limits on primordial black hole production in the early Universe. It is shown, in particular, that at frequencies near ∼40 Hz (which is the region explored by LIGO detector), the value of the induced part of Ω_GW cannot exceed (1−3) × 10⁻⁷. The spread of values of the bound is caused by the uncertainty in parameters of the gravitational collapse of black holes.     

A study of possibilities of development of GaAs detectors for high-power nanosecond X-ray pulses

It is proposed to use chromium-compensated semi-insulating GaAs detectors for detecting high-power nanosecond X-ray pulses. An X-ray facility based on a small direct-acting electron accelerator “Sinus-150” developed at the Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk was used as a source of pulsed X-ray radiation. The detectors are shown to detect 5 ns pulses under exposure to 30 mR radiation during one pulse without distortions. In so doing, one-ampere currents flow through the active detector area 0.2 cm². It is found that the physical processes limiting the working capacity of GaAs detectors are due to capture of nonequilibrium electrons and holes by deep centers. At the nonequilibrium charge-carrier concentrations higher than 5·10¹³ cm³, nonuniform distributions of the electric field are formed in the active region and these can result in distortion of the output detector signal shape. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 14–18, September, 2008.     

Challenges in thermal noise for 3rd generation of gravitational wave detectors

Various noise sources limit the sensitivity of current interferometric gravitational wave detectors, including seismic noise, thermal noise of the optical components and suspension elements and photon shot noise. Plans are in place for a suite of hardware upgrades which should increase the sensitivity of these detectors by reducing the various noise sources. With these designs for 2nd generation detectors mature, techniques for further improvement of detector sensitivity by a factor of approximately 10 are under study. A particular challenge is the reduction of the thermal noise associated with the interferometer mirrors and their suspensions. We review the current status of research on thermal noise in interferometric gravitational wave detectors. Aspects of possible techniques for use in future ‘3rd generation detectors’ such as cryogenics and diffractive optics are discussed.     

The Three-Arm Michelson-Fabry-Perot Detector for Gravitational Waves

A three-arm Michelson-Fabry-Perot detector for gravitational waves is designed.It consists of three MichelsonFabry-Perot interferometers,one for each pair of arms.The new detector can be used to confirm whether the gravitational waves are in general relativity polarization states and to set the strong constraints on non-GR gravitational wave polarization states.By the new detectors,the angular resolution of sources can be improved significantly.With the new detector,it is easier to search for and confirm a gravitational wave signal in the observation data.     

Forty Years to the Artemovsk Scintillation Detector for Neutrinos

The current status of the ASD (Artemovsk scintillation detector) experiment aimed at search for a neutrino flux from gravitational collapses of stellar cores is presented. Experimental data obtained for 40 years of operation of the detector situated in a salt mine at a depth of 570 mwe are processed. The results obtained by calculating the expected signal in the detector on the basis of two models of supernova explosion are described. No candidates for neutrino bursts from gravitational star collapses have been revealed: the limit on the frequency of gravitational collapses was found to be less than one event per 17.15 yr at a 90% confidence level (f_col < 0.058 yr^?1).     

Magnetic monopole search at high altitude with the SLIM experiment

The SLIM experiment was a large array of nuclear track detectors located at the Chacaltaya high altitude Laboratory (5230 m a.s.l.). The detector was in particular sensitive to intermediate mass magnetic monopoles, with masses 10⁵ GeV <M_M< 10¹² GeV. From the analysis of the full detector exposed for more than 4 years a flux upper limit of 1.3×10^-15 cm^-2 s^-1 sr^-1 for downgoing fast intermediate mass monopoles was established at the 90% C.L. PACS 14.80.Hv; 29.40.Wk; 29.90.+r     

The ALTAIR cryogenic gravitational-wave experiment

Summary We report on the experimental results obtained with the cryogenic Gravitational-Wave resonant detector ALTAIR located in Frascati (Italy) at the Istituto di Fisica dello Spazio Interplanetario of Consiglio Nazionale delle Ricerche. The peculiarity of this experiment is its working frequency. The first longitudinal mode of resonance of the antenna is at 1.8 kHz. The antenna, now equipped with a resonant capacitive transducer and a d.c. SQUID preamplifier, after a first test in November 1989, has operated almost continuously from May 1990. The best sensitivity, recently reached, expressed in terms of the effective noise temperatureT _eff, is 20 mK, corresponding, for a short pulse of gravitational wave, to a metric perturbationh of 3×10⁻¹⁸. In the last period of measurements (from April 1991 to March 1992) two other antennas were operating: the Explorer antenna (2300 kg,T=2.0 K) at CERN in Geneva and the LSU antenna (2500 kg,T=4.2 K) at Louisiana State University in USA, both having a resonant frequency below 1 kHz. The data of these three detectors can be remote observed, in real time, by the international computer network. Coincidence analysis between the data of these three detectors is in progress. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990 (updated version).     

Neutron interactions as seen by a segmented germanium detector

The GERmanium Detector Array (GERDA) is designed for the search for “neutrinoless double-beta decay” ( 0ν2β with germanium detectors enriched in ⁷⁶Ge . An 18-fold-segmented prototype detector for GERDA Phase II was exposed to an AmBe neutron source to improve the understanding of neutron-induced backgrounds. Neutron interactions with the germanium isotopes themselves and in the surrounding materials were studied. Segment information is used to identify neutron-induced peaks in the recorded energy spectra. The Geant4-based simulation package MaGe is used to simulate the experiment. Though many photon peaks from germanium isotopes excited by neutrons are correctly described by Geant4, some physics processes were identified as being incorrectly treated or even missing.     

Search for monochromatic sources with the GEOGRAV gravitational-wave antenna

Summary The data of 46 months of the GEOGRAV gravitational-wave antenna are analysed to search for monochromatic Doppler-shifted signals from rotating neutron stars, in the frequency band (856.2÷859.2) Hz. Two different methods were used. With the first, the gravitational radiation from the whole sky is investigated and a limit ofh≤1·10⁻²¹ is found. With the second method only the radiation from a single source is searched. The Galactic Centre and the Large Magellanic Cloud are considered as sources and the limit ofh≤6·10⁻²² is found.     

Spectroscopy of neutron deficient 108Te

The neutron deficient nucleus ¹⁰⁸Te was studied in the ⁵⁴Fe(⁵⁸Ni,2p2n) reaction. A detector system consisting of 4 Euroball cluster detectors, a charged-particle detector ball and a 16 element neutron multiplicity filter was used to detect the emitted particles and γ rays. A new, significantly extended level scheme was constructed on the basis of γγ-coincidence relations. Spin values for the states were determined from angular distribution ratios. The experimental results are discussed in terms of the shell model. Received: 7 September 1998     

Search for strong gravitational lensing effect in the current GRB data of BATSE

Because gamma-ray bursts(GRBs)trace the high-z universe,there is an appreciable probability for a GRB to be gravitational lensed by galaxies in the universe.Herein we consider the gravitational lensing effect of GRBs contributed by the dark matter halos in galaxies.Assuming that all halos have the singular isothermal sphere(SIS)mass profile in the mass range 1010h?1M?M2×1013h?1M?and all GRB samples follow the intrinsic redshift distribution and luminosity function derived from the Swift LGRBs sample,we calculated the gravitational lensing probability in BATSE,Swift/BAT and Fermi/GBM GRBs,respectively.With an derived probability result in BATSE GRBs,we searched for lensed GRB pairs in the BATSE5B GRB Spectral catalog.The search did not find any convincing gravitationally lensed events.We discuss our result and future observations for GRB lensing observation.     

Search for Neutrino Bursts from Collapsing Stars by Means of the LVD and BUST Detectors

A long-term and stable operation of the LVD and BUST detectors in searches for neutrino bursts from gravitational star collapses is demonstrated, and a random origin of background pulses in the detectors is confirmed thereby. The experimental results obtained by means of the LSD and BUST detectors on February 23, 1987, are considered in detail. The probability for the possible backgroundmimicked coincidences of clusters of pulses recorded in the LSD detector at 2 : 52 UT with a group of correlations of pulses within 1 s between LSD and BUST in the interval from 1 : 45 to 3 : 45 UT is estimated. Also, coincidences of the background pulses in the LVD and BUST detectors over the period of about eight years are analyzed. The results obtained in this way give sufficient grounds to conclude that the cluster of pulses recorded by the LSD detector on February 23, 1987, at 2 : 52 UT and the coincidences of individual pulses in the LSD and BUST detectors are events associated with the gravitational collapse of SN 1987A.     

Application of pulse shape discrimination in Si detector for fission fragment angular distribution measurements

Pulse shape discrimination (PSD) with totally depleted transmission type Si surface barrier detector in reverse mount has been investigated to identify fission fragments in the presence of elastic background in heavy ion-induced fission reactions by both numerical simulation and experimental studies. The PSD method is compared with the other conventional methods adopted to identify fission fragments with solid-state detectors such as ΔE–E telescope and single thin ΔE detector and the data for the¹⁰B +²³²Th fission reaction are presented. Results demonstrate the usefulness of a single transmission-type surface barrier detector for the identification of fission fragments and projectiles like heavy ions     

Gravitational wave generation in power-law inflationary models

We investigate the generation of gravitational waves in power-law inflationary models. The energy spectrum of the gravitational waves is calculated using the method of continuous Bogoliubov coefficients. We show that, by looking at the interval of frequencies between 10⁻⁵ and 10⁵ Hz and also at the GHz range, important information can be obtained, both about the inflationary period itself and about the thermalization regime between the end of inflation and the beginning of the radiation-dominated era. We thus deem the development of gravitational wave detectors, covering the MHz/GHz range of frequencies, to be an important task for the future.