119259804
Lifetime measurements of 214Po and 212Po with the CTF liquid scintillator detector at LNGS
We have studied the α-decays of 214Po into 210Pb and of 212Po into 208Pb tagged by the coincidence with the preceding β-decays from 214Bi and 212Bi, respectively. The 222Rn, 232Th, and 220Rn sources used were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214Po is (236.00 ± 0.42(stat) ± 0.15(syst)) μs and that of 212Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.
137334067
First scientific application of the membrane cryostat technology
We report on the design, fabrication, performance and commissioning of the first membrane cryostat to be used for scientific application. The Long Baseline Neutrino Experiment (LBNE) has designed and fabricated a membrane cryostat prototype in collaboration with IHI Corporation (IHI). Original goals of the prototype are: to demonstrate the membrane cryostat technology in terms of thermal performance, feasibility for liquid argon, and leak tightness; to demonstrate that we can remove all the impurities from the vessel and achieve the purity requirements in a membrane cryostat without evacuation and using only a controlled gaseous argon purge; to demonstrate that we can achieve and maintain the purity requirements of the liquid argon during filling, purification, and maintenance mode using mole sieve and copper filters from the Liquid Argon Purity Demonstrator (LAPD) R&D project. The purity requirements of a large liquid argon detector such as LBNE are contaminants below 200 parts per trillion oxygen equiva...
121900736
THE BOREXINO DETECTOR
118577347
First Large Scale Production of Low Radioactivity Argon From Underground Sources
We report on the rst large-scale production of low radioactivity argon from underground gas wells. Low radioactivity argon is of general interest, in particular for the construction of large scale WIMP dark matter searches and detectors of reactor neutrinos for non-proliferation eorts. Atmospheric argon has an activity of about 1 Bq/kg from the decays of 39 Ar; the concentration of 39 Ar in the underground argon we are collecting is at least a factor of 100 lower than this value. The argon is collected from a stream of gas from a CO2 well in southwestern Colorado with a Vacuum Pressure Swing Adsorption (VPSA) plant. The gas from the well contains argon at a concentration of 400-600 ppm, and the VPSA plant produces an output stream with an argon concentration at the level of 30,000-50,000 ppm (3-5%) in a single pass. This gas is sent for further processing to Fermilab where it is puried by cryogenic distillation. The argon production rate is presently 0.5 kg/day.
35606815
Response of AGATA segmented HPGe detectors to gamma-rays up to 15.1 MeV
In many in-beam gamma spectroscopy experiments the detection of high-energy gamma rays in the range up to 10–20 MeV is of primary importance. New generation high-resolution gamma-ray spectrometers like AGATA and GRETA are composed of position sensitive segmented HPGe detectors and provide a reconstruction of the gamma-ray tracks. The performance of AGATA detectors in this energy range has, however, never been studied in detail. A measurement of the response to 15.1 MeV gamma rays has been performed using two HPGe triple clusters of the AGATA Demonstrator array, operating at LNL-INFN. This manuscript presents the preliminary results of a test of the AGATA detectors for the measurement of high-energy gamma rays, in terms of detection efficiency, energy resolution, tracking and performance of the pulse shape analysis (PSA) algorithms.
119979898
Lifetime measurements of excited states in neutron-rich Ar44,46 populated via a multinucleon transfer reaction
Lifetimes of low-lying excited states of the neutron-rich {sup 44,46}Ar nuclei, populated via multinucleon transfer reactions, are measured by means of the differential recoil distance Doppler shift method. The extracted electromagnetic transition probabilities are compared with previous intermediate-energy Coulomb-excitation measurements and with large-scale shell-model calculations. The increase in the deduced B(E2;2{sup +{yields}}0{sup +}) transition probability from {sup 44}Ar to the closed-shell nucleus {sup 46}Ar contradicts the earlier results of Coulomb-excitation experiments. Shell-model calculations using different effective interactions agree with the new measured values.
73707465
Single and pair neutron transfers at sub-barrier energies
Multinucleon transfer cross sections in the {sup 96}Zr+{sup 40}Ca system have been measured, in inverse kinematics, at bombarding energies ranging from the Coulomb barrier to {approx}25% below. Targetlike recoils have been identified in A, Z and velocity with the large solid angle magnetic spectrometer PRISMA. The experimental data for one- and two-neutron transfer channels have been compared with semiclassical microscopic calculations. For the two-neutron transfer channels the relevance of the transitions to the ground state and to the 0{sup +} excited states of {sup 42}Ca are discussed by employing, for the reaction mechanism, the successive approximation. It is found that the transition to the 0{sup +} state at {approx}6 MeV, whose wave function is dominated by the two neutrons in the 2p{sub 3/2} shell, is much larger than the ground state one. The comparison with the inclusive data reveals that transitions to states with high multipolarity and non-natural parity are important. This suggests that more complex two-particle correlations have to be incorporated in the treatment of the transfer process.
53130577
Isospin mixing at finite temperature in 80Zr
Isospin mixing induced by the Coulomb interaction has been studied in the compound nucleus 80 Zr at T~2 MeV produced in the fusion-evaporation reaction 40 Ca+ 40 Ca at E beam = 136 MeV. The isospin impurity was measured using the first step of the Giant Dipole Resonance γ decay. The preliminary value of the Coulomb spreading width has been extracted via statistical model analysis of the measured γ spectrum.
17188150
The Population of Metastable States as a Probe of Relativistic-energy Fragmentation Reactions
Isomeric ratios have been measured for high-spin states in Po-198,200,206,208(84), At-208,209,210,211(85), Rn-210,211,212,213,214(86), Fr-208,211,212,213,214(87), Ra-210,211,212,214,215(88), and Ac-215(89) following the projectile fragmentation of a 1 AGeV U-238 beam by a Be-9 target at GSI Helmholtzzentrum fur Schwerionenforschung. The fragments were separated in the fragment separator (FRS) and identified by means of energy loss and time-of-flight techniques. They were brought to rest at the centre of the RISING gamma-ray detector array and intensities of gamma rays emitted in the decay of isomeric states with half-lives between 100 ns and 40 mu s and spin values up to 55/2 (h) over bar were used to obtain the corresponding isomeric ratios. The data are compared to theoretical isomeric ratios calculated in the framework of the abrasion-ablation model. Large experimental enhancements are obtained for high-spin isomers in comparison to expected values. (C) 2013 Elsevier B.V. All rights reserved. (Less)
120912280
Measurement of isospin mixing at a finite temperature in Zr-80 via giant dipole resonance decay
A. Corsi,1,2,* O. Wieland,2 S. Barlini,3,4 A. Bracco,1,2 F. Camera,1,2 V. L. Kravchuk,5 G. Baiocco,7 L. Bardelli,4 G. Benzoni,2 M. Bini,3 N. Blasi,2 S. Brambilla,2 M. Bruno,7 G. Casini,4 M. Ciemala,8 M. Cinausero,5 F. C. L. Crespi,1,2 M. D’Agostino,7 M. Degerlier,5 A. Giaz,1,2 F. Gramegna,5 M. Kmiecik,8 S. Leoni,1,2 A. Maj,8 T. Marchi,5,6 K. Mazurek,8 W. Meczynski,8 B. Million,2 D. Montanari,6 L. Morelli,7 S. Myalski,8 A. Nannini,4 R. Nicolini,1,2 G. Pasquali,3 G. Poggi,3 V. Vandone,1,2 and G. Vannini7 1Dipartimento di Fisica, Università di Milano and INFN Sezione di Milano, Italy 2INFN, Sezione di Milano, Milano, Italy 3Dipartimento di Fisica, Università di Firenze and INFN Sezione di Firenze, Italy 4INFN Sezione di Firenze, Italy 5INFN Laboratori Nazionali di Legnaro, Padova, Italy 6Dipartimento di Fisica, Università di Padova and INFN Sezione di Padova, Italy 7Dipartimento di Fisica, Università di Bologna and INFN Sezione di Bologna, Italy 8The Henryk Niewodniczaǹski Institute of Nuclear Physics PAN, Krakow, Poland (Received 20 March 2011; published 20 October 2011)