Search

The electron-beam ion trap (EBIT) at the National Institute of Standards and Technology (NIST) was employed for the measurement and detailed analysis of the $\ensuremath{\delta}\ensuremath{\lambda}(^{124}\mathrm{Xe},^{136}\mathrm{Xe})$ isotopic shifts of the Al-like $3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}\ensuremath{-}3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{3/2}$, Al-like $3{s}^{2}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}\ensuremath{-}3{s}^{2}3d\phantom{\rule{4pt}{0ex}}^{2}D_{3/2}$, Mg-like $3{s}^{2}\phantom{\rule{4pt}{0ex}}^{1}S_{0}\ensuremath{-}3s3p\phantom{\rule{4pt}{0ex}}^{1}P_{1}$, Mg-like $3{s}^{2}\phantom{\rule{4pt}{0ex}}^{1}S_{0}\ensuremath{-}3s3p\phantom{\rule{4pt}{0ex}}^{3}P_{1}$, Na-like $3s\phantom{\rule{4pt}{0ex}}^{2}S_{1/2}\ensuremath{-}3p\phantom{\rule{4pt}{0ex}}^{2}P_{1/2}$ (${D}_{1}$), and Na-like $3s\phantom{\rule{4pt}{0ex}}^{2}S_{1/2}\ensuremath{-}3p\phantom{\rule{4pt}{0ex}}^{2}P_{3/2}$ (${D}_{2}$) transitions. Systematic analysis revealed possible line blends and contributing experimental uncertainties. Highly accurate atomic-structure calculations were conducted and used to determine the $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{136,124}$ difference in the mean-square nuclear charge radii of the two xenon isotopes. In the present work, $\ensuremath{\delta}{\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}}^{136,124}$ of 0.276 $\ifmmode\pm\else\textpm\fi{}$ 0.030 ${\mathrm{fm}}^{2}$ was obtained from the weighted average of the Na-like ${D}_{1}$, Mg-like $3{s}^{2}\ensuremath{-}3s3p$ and Al-like $3{s}^{2}3p\ensuremath{-}3{s}^{2}3p$ and $3{s}^{2}3p\ensuremath{-}3{s}^{2}3d$ transitions. This result confirms the value previously determined from the Na-like ${D}_{1}$ transition of 0.269 $\ifmmode\pm\else\textpm\fi{}$ 0.042 ${\mathrm{fm}}^{2}$. The uncertainty of our result is half of that of previous results for the same isotopes obtained from x-ray spectroscopy of muonic atoms, laser spectroscopy of neutral xenon atoms, and a global evaluation of charge radii. Our result is slightly outside the uncertainty of the value obtained from a King plot analysis of comparable precision. The present work illustrates that extreme-ultraviolet spectroscopy of highly charged ions is a viable approach for measurements of charge nuclear radii differences and can be used to benchmark conventional methods.

Background: The quadratic isobaric multiplet mass equation (IMME) has been very successful at predicting the masses of isobaric analog states in the same multiplet, while its coefficients are known to follow specific trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] $^{44}\mathrm{V}$ mass value results in an anomalous negative $c$ coefficient for the IMME quadratic term; a consequence of large uncertainty and an unresolved isomeric state. The $b$ and $c$ coefficients can provide useful constraints for construction of the isospin-nonconserving Hamiltonians for the $pf$ shell. In addition, the excitation energy of the ${0}^{+},T=2$ level in $^{44}\mathrm{V}$ is currently unknown. This state can be used to constrain the mass of the more exotic $^{44}\mathrm{Cr}$.Purpose: The aim of the experimental campaign was to perform high-precision mass measurements to resolve the difference between $^{44}\mathrm{V}$ isomeric and ground states, to test the IMME using the new ground state mass value and to provide necessary ingredients for the future identification of the ${0}^{+}$, $T=2$ state in $^{44}\mathrm{V}$.Method: High-precision Penning trap mass spectrometry was performed at LEBIT, located at the National Superconducting Cyclotron Laboratory, to measure the cyclotron frequency ratios of [${^{44g,m}\mathrm{VO}]}^{+}$ versus [${^{32}\mathrm{SCO}]}^{+}$, a well-known reference mass, to extract both the isomeric and ground state masses of $^{44}\mathrm{V}$.Results: The mass excess of the ground and isomeric states in $^{44}\mathrm{V}$ were measured to be $\ensuremath{-}23\phantom{\rule{4pt}{0ex}}804.9(80)$ keV/${c}^{2}$ and $\ensuremath{-}23\phantom{\rule{4pt}{0ex}}537.0(55)$ keV/${c}^{2}$, respectively. This yielded a new proton separation energy of ${S}_{p}=1\phantom{\rule{4pt}{0ex}}773(10)$ keV.Conclusion: The new values of the ground state and isomeric state masses of $^{44}\mathrm{V}$ have been used to deduce the IMME $b$ and $c$ coefficients of the lowest ${2}^{+}$ and ${6}^{+}$ triplets in $A=44$. The ${2}^{+}\phantom{\rule{4pt}{0ex}}c$ coefficient is now verified with the IMME trend for lowest multiplets and is in good agreement with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between $^{44}\mathrm{V}$ and $^{44}\mathrm{Sc}$, in line with isospin-symmetry for this multiplet. The new value of the proton separation energy determined, to an uncertainty of 10 keV, will be important for the determination of the ${0}^{+}$, $T=2$ state in $^{44}\mathrm{V}$ and, consequently, for prediction of the mass excess of $^{44}\mathrm{Cr}$.

Background: Isobaric quintets provide the best test of the isobaric multiplet mass equation (IMME) and can uniquely identify higher order corrections suggestive of isospin symmetry breaking effects in the nuclear Hamiltonian. The generalized IMME (GIMME) is a novel microscopic interaction theory that predicts an extension to the quadratic form of the IMME. Only the $A=20,32$ $T=2$ quintets have the exotic ${T}_{z}=\ensuremath{-}2$ member ground state mass determined to high precision by Penning trap mass spectrometry.Purpose: We aim to establish $A=36$ as the third $T=2$ isobaric quintet with the ${T}_{z}=\ensuremath{-}2$ member ground state mass measured by Penning trap mass spectrometry and provide the first test of the predictive power of the GIMME.Method: A radioactive beam of neutron-deficient $^{36}\mathrm{Ca}$ was produced by projectile fragmentation at the National Superconducting Cyclotron Laboratory. The beam was thermalized and the masses of $^{36}\mathrm{Ca}^{+}$ and $^{36}\mathrm{Ca}^{2+}$ were measured by the time-of-flight ion cyclotron resonance method in the LEBIT 9.4 T Penning trap.Results: We measure the mass excess of $^{36}\mathrm{Ca}$ to be $\mathrm{ME}=\ensuremath{-}6483.6(56)$ keV, an improvement in precision by a factor of 6 over the literature value. The new datum is considered together with evaluated nuclear data on the $A=36$, $T=2$ quintet. We find agreement with the quadratic form of the IMME given by isospin symmetry, but only coarse qualitative agreement with predictions of the GIMME.Conclusion: A total of three isobaric quintets have their most exotic members measured by Penning trap mass spectrometry. The GIMME predictions in the $T=2$ quintet appear to break down for $A=32$ and greater.

Background: The $^{51}\mathrm{Fe}(p,\ensuremath{\gamma})^{52}\mathrm{Co}$ reaction lies along the main rp-process path leading up to the $^{56}\mathrm{Ni}$ waiting point. The uncertainty in the reaction $Q$ value, which determines the equilibrium between the forward proton-capture and reverse photodisintegration $^{52}\mathrm{Co}(\ensuremath{\gamma},p)^{51}\mathrm{Fe}$ reaction, contributes to considerable uncertainty in the reaction rate in the temperature range of interest for Type I x-ray bursts and thus to an $\ensuremath{\approx}10%$ uncertainty in burst ashes lighter than $A=56$.Purpose: With a recent Penning trap mass measurement of $^{52}\mathrm{Co}$ reducing the uncertainty on its mass to 6.6 keV [Nesterenko et al., J. Phys. G 44, 065103 (2017)], the dominant source of uncertainty in the reaction $Q$ value is now the mass of $^{51}\mathrm{Fe}$, reported in the 2016 atomic mass evaluation to a precision of 9 keV [Wang et al., Chin. Phys. C 41, 030003 (2017)]. A new, high-precision Penning trap mass measurement of $^{51}\mathrm{Fe}$ was performed to allow the determination of an improved precision $Q$ value and thus new reaction rates.Method: $^{51}\mathrm{Fe}$ was produced using projectile fragmentation at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory, and separated using the A1900 fragment separator. The resulting secondary beam was then thermalized in the beam stopping area before a mass measurement was performed using the LEBIT 9.4T Penning trap mass spectrometer.Results: The new mass excess, $\mathrm{ME}=\ensuremath{-}40189.2(1.6)$ keV, is sixfold more precise than the current AME value, and $1.6\ensuremath{\sigma}$ less negative. This value was used to calculate a new proton separation energy for $^{52}\mathrm{Co}$ of 1431(7) keV. New excitation levels were then calculated for $^{52}\mathrm{Co}$ using the nushellx code with the GXPF1A interaction, and a new reaction rate and burst ash composition was calculated.Conclusions: With a new measured $Q$ value, the uncertainty on the $^{51}\mathrm{Fe}(p,\ensuremath{\gamma})$ reaction rate is dominated by the poorly measured $^{52}\mathrm{Co}$ level structure. Reducing this uncertainty would allow a more precise rate calculation and a better determination of the mass abundances in the burst ashes.

We report the mass measurement of $^{56}\mathrm{Cu}$, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of $^{56}\mathrm{Cu}$ is critical for constraining the reaction rates of the $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ $^{56}\mathrm{Cu}(p,\ensuremath{\gamma})$ $^{57}\mathrm{Zn}({\ensuremath{\beta}}^{+})$ $^{57}\mathrm{Cu}$ bypass around the $^{56}\mathrm{Ni}$ waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, $\mathrm{ME}=\ensuremath{-}38626.7(7.1)\text{ }\text{ }\mathrm{keV}$, is a factor of 30 more precise than the extrapolated value suggested in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C 41, 030003 (2017)]. The new experimental average, using our new mass and the value from AME2016, is used to calculate the astrophysical $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ and $^{56}\mathrm{Cu}(p,\ensuremath{\gamma})$ forward and reverse rates and perform reaction network calculations of the $rp$ process. These show that the $rp$-process flow redirects around the $^{56}\mathrm{Ni}$ waiting point through the $^{55}\mathrm{Ni}(p,\ensuremath{\gamma})$ route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

The variation in mean-square nuclear charge radius of xenon isotopes was measured utilizing a new method based on extreme ultraviolet spectroscopy of highly charged Na-like ions. The isotope shift of the Na-like D1 (3s $^{2}$S$_{1/2}$ - 3p $^2$P$_{1/2}$) transition between the $^{124}$Xe and $^{136}$Xe isotopes was experimentally determined using the electron beam ion trap facility at the National Institute of Standards and Technology. The mass shift and the field shift coefficients were calculated with enhanced precision by relativistic many-body perturbation theory and multi-configuration Dirac-Hartree-Fock method. The mean-square nuclear charge radius difference was found to be $\delta^{136, 124}$ = 0.269(0.042) fm$^2$. Our result has smaller uncertainty than previous experimental results and agrees with the recommended value by Angeli and Marinova [I. Angeli and K. P. Marinova, At. Data and Nucl. Data Tables {\bf 99}, 69-95 (2013)]., Comment: 6 pages, 3 figures

We report the mass measurement of ^{56}Cu, using the LEBIT 9.4 T Penning trap mass spectrometer at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of ^{56}Cu is critical for constraining the reaction rates of the ^{55}Ni(p,γ) ^{56}Cu(p,γ) ^{57}Zn(β^{+}) ^{57}Cu bypass around the ^{56}Ni waiting point. Previous recommended mass excess values have disagreed by several hundred keV. Our new value, ME=-38626.7(7.1) keV, is a factor of 30 more precise than the extrapolated value suggested in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)CPCHCQ1674-113710.1088/1674-1137/36/12/003], and more than a factor of 12 more precise than values calculated using local mass extrapolations, while agreeing with the newest 2016 atomic mass evaluation value [Chin. Phys. C 41, 030003 (2017)CPCHCQ1674-113710.1088/1674-1137/41/3/030003]. The new experimental average, using our new mass and the value from AME2016, is used to calculate the astrophysical ^{55}Ni(p,γ) and ^{56}Cu(p,γ) forward and reverse rates and perform reaction network calculations of the rp process. These show that the rp-process flow redirects around the ^{56}Ni waiting point through the ^{55}Ni(p,γ) route, allowing it to proceed to higher masses more quickly and resulting in a reduction in ashes around this waiting point and an enhancement to higher-mass ashes.

We report on a simple method to perform an absolute calibration of the magnetic beam analyzer of the reaccelerator ReA3 at the National Superconducting Cyclotron Laboratory. The method is based on the time of flight between two beam stoppers 7.65 m apart. Based on two independent time-of-flight measurements at three different beam energies, the beam analyzer magnet is calibrated with an accuracy of 0.12 %, corresponding to a beam energy accuracy of 0.24 %.

We report the determination of the Q(EC) value of the mirror transition of (11)C by measuring the atomic masses of (11)C and (11)B using Penning trap mass spectrometry. More than an order of magnitude improvement in precision is achieved as compared to the 2012 Atomic Mass Evaluation (Ame2012) [Chin. Phys. C 36, 1603 (2012)]. This leads to a factor of 3 improvement in the calculated Ft value. Using the new value, Q(EC)=1981.690(61) keV, the uncertainty on Ft is no longer dominated by the uncertainty on the Q(EC) value. Based on this measurement, we provide an updated estimate of the Gamow-Teller to Fermi mixing ratio and standard model values of the correlation coefficients.

We report the determination of the Q(EC) value of the mirror transition of (11)C by measuring the atomic masses of (11)C and (11)B using Penning trap mass spectrometry. More than an order of magnitude improvement in precision is achieved as compared to the 2012 Atomic Mass Evaluation (Ame2012) [Chin. Phys. C 36, 1603 (2012)]. This leads to a factor of 3 improvement in the calculated Ft value. Using the new value, Q(EC)=1981.690(61) keV, the uncertainty on Ft is no longer dominated by the uncertainty on the Q(EC) value. Based on this measurement, we provide an updated estimate of the Gamow-Teller to Fermi mixing ratio and standard model values of the correlation coefficients.

We report the first direct measurement of the (14)O superallowed Fermi β-decay QEC value, the last of the so-called "traditional nine" superallowed Fermi β decays to be measured with Penning trap mass spectrometry. (14)O, along with the other low-Z superallowed β emitter, (10)C, is crucial for setting limits on the existence of possible scalar currents. The new ground state QEC value, 5144.364(25) keV, when combined with the energy of the 0(+) daughter state, Ex(0(+))=2312.798(11) keV [F. Ajzenberg-Selove, Nucl. Phys. A523, 1 (1991)], provides a new determination of the superallowed β-decay QEC value, QEC(sa)=2831.566(28) keV, with an order of magnitude improvement in precision, and a similar improvement to the calculated statistical rate function f. This is used to calculate an improved Ft value of 3073.8(2.8) s.

The energy-integrated reaction cross-sections of several neutron-rich nuclei ( 17−22 N, 19−24 O, 21−27 F, 23−30 Ne, 26−33 Na, 28−35 Mg, 31−38 Al, 33−40 Si, 36−42 P, 39−44 S, 42−45 Cl, 45,46 Ar), measured at intermediate energy (30–65 A MeV), via direct method, are presented. Silicon detectors have been used as the active target as well as for particles identification. The reduced strong absorption radii r 0 2 are extracted and compared to the data available from the literature. New measurements for 19 nuclei ( 27 F, 27,30 Ne, 33 Na, 28,34–35 Mg, 36−38 Al, 38−40 Si, 41−42 P, 42−44 S, 45 Cl) are revealed. From the study of the isospin dependence of the reduced strong absorption radius, a new quadratic parameterisation of the nuclear radii in the closed shell regions N = 8 and N = 28 , is proposed. According to this parameterisation, the proton/neutron rich nuclei skin effect is well described and a new anomalous structure: halo-structure or large deformation is suggested for 35 Mg and 44 S nuclei.

Since 2001, the SPIRAL I Facility (Systeme de Production d’Ions Radioactifs en Ligne, version I) located at GANIL in Caen (France) has delivered radioactive ion beams mainly of “light” gaseous elements, from He to Kr. In March 2004, a beam of some pps of 31Ar (15 ms) was produced. Very soon, a new target-and-ion-source system (TISS) will be tested for the production of radioactive multi-charged ions of alkaline elements. For making radioactive ion beams of heavier elements, the SPIRAL II project is under study. The proposed technique is to produce heavy fragments by fission of uranium induced by neutrons, themselves produced by a 200 kW deuteron beam hitting a carbon converter. The technical studies should be completed by the end of 2004. After a short presentation of results from the operation of SPIRAL I, the design of the SPIRAL II target and ion-source system is presented.

We report a series of measurements performed to characterize the atom-to-ion transformation time in singly charged electron cyclotron resonance ion sources (ECRISs). Three ECRISs were used with He, Ne, Ar and Kr noble gases. The transformation time as a function of the support gas flow, the ionization efficiency, and source volume is presented and compared to a calculation made with a simple dynamic model.

Transfer reactions are verified to be an important tool for the study of light unbound nuclei. We have studied the proton-rich unbound nuclei 15 F and 11 N, 10 N respectively through the 16 O( 14 N, 15 C) 15 F and 12 C( 14 N, 15 C) 11 N, 10 B( 14 N, 13 B) 11 N, 10 B( 14 N, 14 B) 10 N reactions. Resonance energies and width were obtained.

Minimono is a 2.45 GHz electron cyclotron resonance ion source for singly charged ions which uses only permanent magnets. Measurements of ionization efficiencies, maximum currents extracted, and emittances for H+, 3,4He+, N+, Ne+, Ar+, Kr+, S+, and Si+ were carried out. In the case of buckminster fullerenes, C60+, C602+, and C603+ ions were extracted. The results obtained, the general mechanical simplicity of this ion source, and its low cost make this source attractive for the production of stable and radioactive ions.

Mass measurements of the N = Z nuclei 80Zr, 76Sr, 68Se were performed for the first time and a new measurement was obtained for 80Y, using the second cyclotron CSS2 of GANIL as a high-resolution spectrometer. Ions around N = Z were produced by fusion-evaporation in the inverse 58Ni (4.32 MeV A) + 24Mg and 12C reactions. New masses were measured by a time-of-flight method, with a precision of 2 · 10-6, by using well-known masses as references. Study of the double binding energy difference δV np is then performed leading to a strong N = Z Wigner effect around N = Z = 40. Knowledge of new masses in this region also plays a crucial role in the modelling of the astrophysical rp process.

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 31 Ar radioactive nuclei with a precision of 10-6.

The ground state of the proton-rich, unbound nucleus ${}^{11}\mathrm{N}$ was observed, together with six excited states using the multinucleon transfer reaction ${}^{10}\mathrm{B}{(}^{14}\mathrm{N}{,}^{13}\mathrm{B}{)}^{11}\mathrm{N}$ at $30A$ MeV incident energy at Grand Acc\'el\'erateur National d'Ions Lourds. Levels of ${}^{11}\mathrm{N}$ are observed as well defined resonances in the spectrum of the ${}^{13}\mathrm{B}$ ejectiles. They are localized at 1.63(5), 2.16(5), 3.06(8), 3.61(5), 4.33(5), 5.98(10), and 6.54(10) MeV above the ${}^{10}\mathrm{C}+p$ threshold. The ground-state resonance has a mass excess of 24.618(50) MeV; the experimental width is smaller than theoretical predictions.

Secondary ions of100Ag,100Cd,100In and100Sn were produced via the fusion-evaporation reaction50Cr+58Ni at an energy of 5.1 MeV/nucleon. TheA=100 secondary ions were accelerated in the second cyclotron of GANIL, which was used as a high-resolution mass spectrometer. The masses of the three latter isobars were measured with respect to the abundantly produced100Ag. The known mass of100Cd was very well reproduced and the masses of100In and100Sn were determined for the first time with precisions of 3×10−6 and 10−5, respectively.

NESTER; International audience; ISOL beams of $^{19-22}$O were produced at ISOLDE and GANIL. At ISOLDE the neutron-rich oxygen isotopes are produced by 1.4 GeV proton-induced reactions in a UCx/graphite target. The target is connected via a water-cooled transfer line (to retain all non-volatile isobars) to an ISOLDE type FEBIAD ion source where the released CO is dominantly ionized as CO+. $^{19-22}$O beams were also produced at SPIRAL (GANIL). A 77.5 MeV/nucleon 36S beam was fragmented in a thick graphite target, coupled by a cold transfer tube to an ECR ion source which ionizes the released CO dominantly as O$^+$ and CO$^+$.

The binary decay into strongly damped fragments and the quasielastic reactions of the $^{28}\mathrm{Si}$+ $^{16}\mathrm{O}$ system were measured at ${E}_{\mathrm{lab}}=107.5 \mathrm{and} 139.0$ MeV in the angular range of $30\ifmmode^\circ\else\textdegree\fi{}l~{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}l~150\ifmmode^\circ\else\textdegree\fi{}$ using kinematic coincidence. The loss in the binary decay cross section due to light particle evaporation by the highly excited fragments was evaluated. The $Q$-value-integrated angular distributions of the primary decay exhibit the $\frac{1}{{sin\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}}$ behavior at backward angles, indicating a long lifetime. Mass distributions and the $^{16}\mathrm{O}$/$^{12}\mathrm{C}$ ratio suggest a noncompound process for the reaction mechanism. Coupled-channels calculations, including a great number of channels populated in the reactions, yield good agreement with the experimental angular distributions.

In a high precision experiment, Mott scattering of the 208Pb+208Pb and elastic scattering of the 208Pb+238U systems was measured at 6 energies near the Coulomb barrier with kinematic coincidences for angle pairs at θlab=30°, 60°. The relative laboratory angle between scattered and recoiling nuclei, measured with an absolute precision of 0.003° provides a measurement of the reaction kinematics and the energy loss in the reaction. The binding energy of internal shells of the quasiatioms formed during the collision can be measured in this way.

We report on direct time-of-flight based mass measurements of 16 light neutron-rich nuclei. These include the first determination of the masses of the Borromean drip-line nuclei (19)B, (22)C, and (29)F as well as that of (34)Na. In addition, the most precise determinations to date for (23)N and (31)Ne are reported. Coupled with recent interaction cross-section measurements, the present results support the occurrence of a two-neutron halo in (22)C, with a dominant ν2s(1/2)(2) configuration, and a single-neutron halo in (31)Ne with the valence neutron occupying predominantly the 2p(3/2) orbital. Despite a very low two-neutron separation energy the development of a halo in (19)B is hindered by the 1d(5/2)(2) character of the valence neutrons.

Expérience GANIL E511 , Spectromètre VAMOS; We investigated deep inelastic reactions in 238U+238U collisions at 6.09, 6.49, 6.91, 7.1 and 7.35×AMeV at the VAMOS spectrometer (GANIL). A large transfer of neutrons and protons was observed at all beam energies. For a transfer of more than 10 nucleons the total kinetic energy of the detected fragments becomes independent of the beam energy and reaches values far below the Coulomb barrier for spherical fragments. This points to the formation of a di-nuclear system in the entrance channel which develops an elongated shape and a strong neck. For such reactions we expect an enhanced lifetime of the di-nuclear system which is significantly longer than the time scale for elastic and quasi-elastic reactions. Different theoretical approaches predict delay times of more than 5 × 10−21 s for a subset of our data.

Experimental results on orbiting phenomena in 18 O+ 10,11 B systems at E c.m. =18.8 and 19.9 MeV are presented. We show that all features of the orbiting phenomena of 11 B( 18 O, 18 O) 11 B and related transfer reactions are explained by a complete coupled-channels calculation in the AST framework. It is also shown that the orbiting features and the back-angle anomaly are strongly related and explained by the same channel coupling.

Use has been made of the interference between the nuclear and Coulomb amplitudes in the scattering of 84 MeV/nucleon $^{17}\mathrm{O}$ ions by $^{124}\mathrm{Sn}$ to study the isospin character of the giant quadrupole transition. The data are well described by assuming the transition is ``isoscalar,'' i.e., ${\mathit{M}}_{\mathit{n}}$/${\mathit{M}}_{\mathit{p}}$=N/Z. This is in disagreement with the results of ${\mathrm{\ensuremath{\pi}}}^{+}$/${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ scattering on $^{118}\mathrm{Sn}$ and recent (e,e'n) measurements on $^{116}\mathrm{Sn}$. Cross sections for excitation of the ${2}^{+}$ state at 1.132 MeV, ${3}^{\mathrm{\ensuremath{-}}}$ state at 2.614 MeV, and giant monopole resonance are included with corresponding coupled-channels calculations.

Using an inversion procedure for the SO(3,1) algebraic potential the best shape for reproducing the S l matrix elements of a Woods-Saxon potential is determined. The algebraic optical potential thus found is applied to the elastic scattering of 12 C+ 24 Mg at E LAB =24.8, 27.7, 31.2, 34.8, 37.8 and 40.0 MeV.

The masses of neutron-deficient nuclides near the $N=Z$ line with $A=64\text{\ensuremath{-}}80$ have been determined using a direct time-of-flight technique which employed a cyclotron as a high-resolution spectrometer. The measured atomic masses for $^{68}\mathrm{Se}$ and $^{80}\mathrm{Y}$ were 67.9421(3) u and 79.9344(2) u, respectively. The new values agree with the 2003 Atomic Mass Evaluation. The result for $^{68}\mathrm{Se}$ confirms that this nucleus is a waiting point of the rp-process, and that for $^{80}\mathrm{Y}$ resolves the conflict between earlier measurements. Using the present results and the 2003 Atomic Mass Evaluation compilation, the empirical interaction between the last proton and the last neutron in $N=Z$ nuclei has been revisited and extended.

We searched for a long-living component in the collision of 238U+238U between 6.09 A and 7.35 A MeV. The experiment was performed at GANIL using the spectrometer VAMOS, tuned for observing reactions with kinematics similar to quasi-fission events. Theoretical calculations indicate that reactions with strong energy dissipation and a large number of transferred nucleons are correlated to a time delay in the decay of the giant system. We detected events of such type in the focal plane of VAMOS. These events present an excitation function increasing with bombarding energy.

The scattering of 84-MeV/nucleon {sup 17}O ions by {sup 118}Sn has been studied. Inelastic cross sections for excitation of the 2.327-MeV state (3{sup {minus}}), the giant quadrupole resonance, and the giant monopole resonance are reproduced by distorted-wave approximation calculations using the deformed potential model and assuming isoscalar transitions. A minimum predicted in the angular distribution at {theta}{sub c.m.}=1.9{degree} from utilization of the small {ital B}({ital E}2){up arrow} strength suggested by {pi}{sup +}/{pi}{sup {minus}} scattering is not apparent in the data.

We measured six fairly complete angular distributions of elastic, inelastic and α-transfer reactions of the 12 C + 24 Mg system at E CM =25.2 MeV. We performed coupled channels calculations using algebraic scattering theory with the nuclear algebraic potential derived from nuclear phase shifts and using the available structure information for the inelastic coupling strengths. The back angle rise in the elastic cross section is fully explained by the couplings between elastic and transfer channels.

The root-mean-square (rms) nuclear charge radius of 8He, the most neutron-rich of all particle-stable nuclei, has been determined for the first time to be 1.93(3) fm. In addition, the rms charge radius of 6He was measured to be 2.068(11) fm, in excellent agreement with a previous result. The significant reduction in charge radius from 6He to 8He is an indication of the change in the correlations of the excess neutrons and is consistent with the 8He neutron halo structure. The experiment was based on laser spectroscopy of individual helium atoms cooled and confined in a magneto-optical trap. Charge radii were extracted from the measured isotope shifts with the help of precision atomic theory calculations.

The possibility of observing neutrinoless double beta decay offers the opportunity of determining the effective neutrino mass if the nuclear matrix element were known. Theoretical calculations are uncertain, and measurements of the occupations of valence orbits by nucleons active in the decay can be important. The occupation of valence neutron orbits in the ground states of 76Ge (a candidate for such decay) and 76Se (the daughter nucleus) were determined by precisely measuring cross sections for both neutron-adding and removing transfer reactions. Our results indicate that the Fermi surface is much more diffuse than in theoretical calculations. We find that the populations of at least three orbits change significantly between these two ground states while in the calculations, the changes are confined primarily to one orbit.

Expérience GANIL; International audience; We performed an experiment to search for a signature of a long living component in the collision of $^{238}$U + $^{238}$U between 6.09 and 7.35A MeV. The experiment was performed at GANIL using the spectrometer VAMOS, tuned for observing reactions with kinematics similar to fusion-fission events. Theoretical calculations indicate that if a long living component would exist for this reaction, the most probable fission channel of such a giant system would be via the emissionof quasi-lead nuclei. We detected events of such a category in the focal plane of VAMOS. These events present an excitation function growing as a function of the bombarding energy.

International audience; This report summarizes the experiments relative to Super-Heavy Element studies done at GANIL — CEA — CNRS since 1999. It also gives an overview of future experiments and opportunities offered by SPIRAL 2 and LINAG beams in a medium term.

International audience; An original approach to the time behavior of an isotope-separator-on-line production system is proposed in the case of a production system where the target and the ion source are connected through a conductance much larger than that of the exit hole of the source. One major goal of this article is to derive the analytical expression of the response time of the system for noble gases from statistical parameters only, which can be deduced from a few simple measurements. The validity limits of the expression of the total efficiency are given, and the calculations are compared to the results obtained at GANIL during operation of SPIRAL 1, using a carbon target close coupled to a multicharged electron cyclotron resonance ion source. The final analytical expression for the total efficiency shows that the usual product of diffusion efficiency, effusion efficiency, and ionization efficiency cannot be applied in our case. We show how it is possible to predict the atom-to-ion transformation efficiency for radioactive isotopes of noble gas using response times measured for stable isotopes.

International audience; In the frame of the production of radioactive ion beams by isotope separator on line method, a new principle of target/ion-source system has been developed at GANIL to produce multicharged ions of alkalis. The principle consists of a surface ionization source associated to a multicharged electron-cyclotron-resonance ion source (ECRIS) named NANOGAN III [R. Leroy et al., AIP Conf. Proc. 749, 137 (2004)] presently used to produce radioactive ions of gas on Système de Production d'Ions Radioactifs Accélérés en Ligne partie I. The singly charged ions are injected in the multicharged ion source without mass separation, through a very short beam line including several stages of acceleration, focusing, deceleration, and rf injection. The first tests showed a good behavior of the ECRIS with the new rf coupling. A study of the surface ionization source is in progress in order to improve its coupling to the $1^+$ beam line.

International audience; A new system has been designed to inject the 10 GHz rf power in the NANOGAN III ion source dedicated to the ionization of exotic atoms from the production target of the SPIRAL system at GANIL. The present system, based on a rectangular-to-coaxial transition equipped with a tuning piston, has been replaced by a direct rectangular-to-circular wave guide to feed the plasma of the source. We present the constraints related to the rf injection and a comparison is given of the present and new injection systems.

Commune avec ACEN; This paper presents two original direct mass-measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high-resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time-of-flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are -53.958(246) MeV and -60.971(180) MeV, respectively. The new mass-measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio-frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass-measurement method and to understand the systematic errors.

The masses of the radioactive nuclei {sup 46}V and its decay daughter {sup 46}Ti have been measured with the Canadian Penning Trap on-line Penning trap mass spectrometer to a precision of 1x10{sup -8}. A Q{sub EC} value of 7052.90(40) keV for the superallowed beta decay of {sup 46}V is obtained from the difference of these two masses. With this precise Q value, the Ft value for this decay is determined with improved precision. An investigation of an earlier Q-value measurement for {sup 46}V uncovers a set of 7 measurements that cannot be reconciled with modern data and affects previous evaluations of V{sub ud} from superallowed Fermi decays. A new evaluation, adding our new data and removing the discredited subset, yields new values for G{sub V} and V{sub ud}. When combined with recent results for V{sub us}, this yields modified constraints for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix and other extensions of the standard model.

The masses of the radioactive nuclei (46)V and its decay daughter (46)Ti have been measured with the Canadian Penning Trap on-line Penning trap mass spectrometer to a precision of 1 x 10(-8). A Q(EC) value of 7052.90(40) keV for the superallowed beta decay of (46)V is obtained from the difference of these two masses. With this precise Q value, the Ft value for this decay is determined with improved precision. An investigation of an earlier Q-value measurement for (46)V uncovers a set of 7 measurements that cannot be reconciled with modern data and affects previous evaluations of V(ud) from superallowed Fermi decays. A new evaluation, adding our new data and removing the discredited subset, yields new values for G(V) and V(ud). When combined with recent results for V(us), this yields modified constraints for the unitarity of the Cabibbo-Kobayashi-Maskawa matrix and other extensions of the standard model.

International audience; The masses of ten neutron-deficient nuclides near the N = Z line with A = 64–80 have been measured with the direct time-of-flight technique using the CSS2 cyclotron as a high-resolution spectrometer. All measured masses agree with the 2003 atomic mass evaluation and are compared to the predictions of the finite range droplet model. The atomic mass excesses obtained for $^{68}$Se and $^{80}$Y are -53.958(246) MeV and -60.971(180) MeV, respectively. The new results for $^{68}$Se and $^(80}$Y are compared to other recent experimental values.

A number of on-line and off-line tests have been performed at the IRIS (investigation of radioactive isotopes at synchrocyclotron) facility in order to develop uranium carbide targets with a high density (11 g/cm3) for the on-line production of neutron-rich isotopes by fission of 238U. A 1 GeV proton beam was used to bombard two kinds of targets held at temperatures in the range of 1900–2100 °C. The first one was a target-ion source assembly slightly modified to withstand 3 months of continuous heating at a temperature of about 2050 °C. The second unit was of a new kind, where ionisation takes place in the target volume itself. A comparison of the on-line isotopic yields before and after heating for 3 months is here reported. The yields and release times of Rb, Cs and In are compared with the ones obtained from a standard reference target, as measured in previous experiments.

A series of on-line mass separation experiments have been performed at the IRIS facility to measure the yield and release of Rb and Cs neutron-rich isotopes produced by fission reaction of 238U. A 1 GeV proton beam was used to bombard uranium carbide targets with the densities of 11 g/cm3 and 1.5 g/cm3 held at temperatures in the range (2000-2230) °C. The release curves of Rb and Cs long-lived isotopes were measured from both kinds of targets. The overall production efficiency was determined making use of experimentally measured cross-sections of that isotope production. Comparison of the experimental yields of Rb and Cs isotopes with the calculated ones after corrections for losses due to finite release times suggests that the diffusion is the dominating process reducing the efficiency for short-lived isotopes. When normalized to the same thickness, an enhancement for the high-density rod target of the measured isotope yields is observed when going far from stability. This is possibly explained by the reactions induced by secondary neutrons. A significant odd-even effect with higher yields of Cs even neutron isotopes has been observed, confirming a similar effect obtained in earlier experiments.

Production of radioactive ions has started at GANIL on the SPIRAL facility since 2001 and numerous multicharged radioactive ion beams have been delivered for high energy nuclear experiments. This article makes an overview of the different beams that have been produced. In the mean time, an important R and D research program is continued in oder to produce new species of radioactive elements. A new concept of multicharged radioactive production that couples a monocharged ion source, based on the monolithe concept, to an ecr ion source like nanogan3 is under developments and is described The development of monocharged ion sources with high efficiencies is also motivated by a new big project that is under studies at GANIL : the SPIRAL 2 Project. The goal of this project consists in extending the disponible radioactive ion beams to very heavy elements created with a new method of production : while the spiral 1 facility uses the projectile fragmentation for radioactive nuclei production, the spiral 2 project is based on the fission of a Uranium carbide target induced by a neutron flow created by a high intensity deuton beam. The principle and an overview of the project is presented.Production of radioactive ions has started at GANIL on the SPIRAL facility since 2001 and numerous multicharged radioactive ion beams have been delivered for high energy nuclear experiments. This article makes an overview of the different beams that have been produced. In the mean time, an important R and D research program is continued in oder to produce new species of radioactive elements. A new concept of multicharged radioactive production that couples a monocharged ion source, based on the monolithe concept, to an ecr ion source like nanogan3 is under developments and is described The development of monocharged ion sources with high efficiencies is also motivated by a new big project that is under studies at GANIL : the SPIRAL 2 Project. The goal of this project consists in extending the disponible radioactive ion beams to very heavy elements created with a new method of production : while the spiral 1 facility uses the projectile fragmentation for radioactive nuclei production, the spiral 2 project ...