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71.
G. Stancari S. N. Atutov R. Calabrese L. Corradi A. Dainelli C. de Mauro A. Khanbekyan E. Mariotti P. Minguzzi L. Moi S. Sanguinetti L. Tomassetti S. Veronesi 《The European physical journal. Special topics》2007,150(1):389-392
Francium is one of the best candidates for atomic parity
nonconservation (APNC) and for the search of permanent electric
dipole moments (EDMs). APNC measurements test the weak force
between electrons and nucleons at very low momentum transfers. They
also represent a unique way to detect weak nucleon-nucleon
interactions. EDMs are instead related to the time-reversal
symmetry. Preliminary to these fundamental measurements are
precision studies in atomic spectroscopy and the development of
magneto-optical traps (MOT), which partially compensate for the lack
of stable Fr isotopes. At LNL Legnaro, francium is produced by
fusion of 100-MeV 18O with 197Au in a thick target,
followed by evaporation of neutrons from the compound nucleus.
Francium diffuses inside the hot target (1200 K) and is surface
ionized for injection at 3 keV in an electrostatic beamline.
Typically, we produce 1×106 (210Fr ions)/s for a
primary flux of 1.5×1012 particles/s. We have studied
Fr yields as a function of primary beam energy, intensity, and
target temperature. Information on the efficiency of bulk
diffusion, surface desorption and ionization is deduced. The beam
then enters a Dryfilm-coated cell, where it is neutralized on a
heated yttrium plate. The escape time of neutral Fr (diffusion +
desorption) is approximately 20 s at 950 K, as measured with a
dedicated setup. In the MOT, we use 6 orthogonal Ti:sapphire laser
beams for the main pumping transition and 6 beams from a stabilized
diode repumper. Fluorescence from trapped atoms is observed with a
cooled CCD camera, in order to reach noise levels from stray
light equivalent to approximately 50 atoms. Systematic tests are
being done to improve the trapping efficiency. We plan to further
develop Fr traps at LNL; in parallel, we will study APNC and EDM
techniques and systematics with stable alkalis at Pisa, Siena, and
Ferrara. 相似文献
72.
V. N. Panteleev O. Alyakrinskiy A. Andrighetto A. E. Barzakh M. Dubois C. Eleon S. Essabaa O. Bajeat D. V. Fedorov G. Gaubert A. M. Ionan V. S. Ivanov P. Jardin A. Lanchais C. Lau R. Leroy G. Lhersonneau C. Mhamed K. A. Mezilev P. L. Molkanov F. V. Moroz S. Yu. Orlov V. Rizzi M. G. Saint Laurent L. Stroe L. B. Tecchio A. C.C. Villari Yu. M. Volkov 《The European physical journal. Special topics》2007,150(1):297-300
The capacity of uranium carbide target materials of
different structure and density for production of neutron-rich and
heavy neutron-deficient nuclides have been investigated. The
yields of Cs and Fr produced by a 1 GeV proton beam of the PNPI
synchrocyclotron and release properties of different targets have
been measured. Yields and release efficiencies of Cs and Fr
produced from a high density UC target material and from low
density UCx prepared by the ISOLDE method at IRIS in the
collaboration with PARRNe group from Orsay are compared. The
yields from ISOLDE original target are presented for comparison as
well. 相似文献
73.
M. Barbui A. Andrighetto C. Antonucci S. Carturan F. Cervellera S. Cevolani M. Cinausero P. Colombo A. Dainelli P. Di Bernardo F. Gramegna G. Maggioni G. Meneghetti C. Petrovich L. Piga G. Prete V. Rizzi M. Santana-Leitner M. Tonezzer P. Zanonato D. Zafiropoulos 《The European physical journal. Special topics》2007,150(1):275-276
A Direct Target for a mid-term RIB ISOL-type facility is being developed at LNL, in the framework of the R&D for the SPES
project [1]. Using a 40 MeV proton beam impinging on a UCx thick target of 2.5 g/cm3 density, a production rate of 1013 in target fissions per second is expected [2]. The crucial point, when short-lived isotopes are produced in the target, is
to build systems (target + ion source) with good release properties and high efficiency.
Monte Carlo simulations were performed using the GEANT4 toolkit [3] and the RIBO code [4] in order to optimize our target
geometry and to estimate the average release time. 相似文献
74.
The measurement of the relative changes / of the radioactive decay by the electron capture process is a direct experimental way to determine the relative changes of the electron charge density on the nucleus. Here we present the results of the experiment with 57Co, where the differences of the decay rate were determined for different chemical states of 57Co. We analyzed the experimental time dependences of the activity of 57Co by means of the direct approximation method and the specialized optimization tool – a genetic algorithm. Using these methods improved the accuracy of the final / values between 57Co and 57Co(Pd), 57CoCl2,57CoS, 57CoSO47H2O, which are in good agreement with theoretical considerations reflecting the electron charge rearrangement and screening effects. 相似文献
75.
76.
Unterricker S. Samokhvalov V. Burlakov I. Degering D. Dietrich M. Deicher M. the ISOLDE Collaboration 《Hyperfine Interactions》2001,136(3-8):275-280
The ferromagnetic spinels CdCr2Se4 and CuCr2Se4 were investigated by PAC (perturbed angular correlations) after implantation of the probes 111In(111Cd), 111mCd, 111Ag(111Cd) and 77Br(77Se). The site occupation of different probes was determined by magnetic and electric hyperfine interactions. Theoretical calculations
of hyperfine parameters by the WIEN97 code gave satisfactory efg (electric field gradients) but the magnetic hyperfine fields
are inconsistent with the experiments.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
77.
M. Chartier W. Mittig G. Auger B. Blank J. M. Casandjian M. Chabert J. Fermщ L. K. Fifield A. Gillibert A. S. Lalleman A. Lépine-Szily M. Lewitowicz M. Mac Cormick M. H. Moscatello F. de Oliveira N. A. Orr G. Politi F. Sarazin H. Savajols C. Spitaels P. Van Isacker A. C. C. Villari M. Wiescher 《Hyperfine Interactions》2001,132(1-4):273-279
The mass-measurement programme at GANIL aims to measure the masses of heavy nuclei close to the N=Z line which is the ideal region to study neutron-proton pairing. An original direct time-of-flight mass-measurement method
was developed at GANIL which uses the CSS2 cyclotron as a high-resolution spectrometer. The masses of ions of A=68,76,80 and 100 have been measured with a precision of a few 10−6. Mass measurements will be performed with the new CIME cyclotron of SPIRAL using a similar method based on the measurement
of the phase of the accelerated ions for different radio-frequencies. A recently approved experiment will help develop this
new technique and aims to measure the mass of 31Ar radioactive nuclei with a precision of 10−6.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
78.
R. Béraud G. Canchel A. Emsallem P. Dendooven J. Huikari W. Huang Y. Wang K. Peräjärvi S. Rinta-Antila A. Jokinen V. S. Kolhinen A. Nieminen H. Penttilä J. Szerypo J. Äystö B. Bruyneel A. Popov 《Hyperfine Interactions》2001,132(1-4):481-486
A new HIGISOL chamber devoted to the study of short-lived products from heavy-ion-induced fusion-evaporation reactions is
proposed. It enables, via the extraction of ions by means of a SPIG (SextuPole rf Ion Guide), to improve the mass resolving
power by a factor 2.5 compared to the previous system using a skimmer-ring assembly. The gas cell was also equiped with an
electric field for faster transportation of recoiling ions to the nozzle where they are ejected with the gas jet. The first
results obtained both with a radioactive α-source and cyclotron beam will be reported.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
79.
A. Toyoda K. Ishida K. Shimomura Y. Matsuda W. Higemoto S. N. Nakamura T. Matsuzaki K. Nagamine 《Hyperfine Interactions》2001,132(1-4):307-312
Recently, the applicability of Penning trap mass spectrometry has been extended to nuclides with a half-life of less than
one second. The mass of 33Ar (T
1/2=174 ms) was measured using the ISOLTRAP spectrometer with an accuracy of 4.2 keV. This measurement provided a stringent test
of the Isobaric Multiplet Mass Equation (IMME) at mass number A=33 and isospin T=3/2. The fast measurement cycle that shows the way to other measurements of very-short-lived nuclides is presented. Furthermore,
the results of the IMME test are displayed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
80.
Ch. Schlegel P. von Neumann-Cosel J. de Boer J. Gerl M. Kaspar I. Kozhoukharov M. Loewe H.J. Maier P.J. Napiorkowsky I. Peter M. Rejmund A. Richter H. Schaffner J. Srebrny M. Würkner H.J. Wollersheim 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):135-138
In-beam Coulomb excitation of the exotic odd-odd nucleus 180Ta has been studied by using a 136Xe beam and a setup consisting of five EUROBALL CLUSTER detectors and the Darmstadt-Heidelberg Crystal Ball array. Spectroscopic
information on the extremely rare 180Ta is obtained from the comparison between an enriched (3.6±0.3% 180Ta) and a natural tantalum target. Possible evidence for a depopulation from the long-lived high-spin J
π = 9- isomer to the short-lived J
π = 1+ ground state is searched for by different methods. The decay of low-K bandheads, which are nanosecond isomers, towards the ground-state band can be demonstrated in delayed spectroscopy. A γγ
coincidence analysis provides indications of K = 5 in-band transitions. Finally, when the Crystal Ball is used as an energy and γ multiplicity filter, signals of decay
into the K = 0 band are observed.
Received: 23 January 2001 / Accepted: 8 February 2001 相似文献