G. Politi

Mass Measurements of Exotic Nuclei around N = Z = 40 with CSS2

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 (4.32MeVA) + 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 δVnp 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.

Mass measurements near N=Z

Abstract After an outline of the physics motivations, that illustrate why we think it is important to measure masses in the region N≈Z, we report on on experiments performed at Ganil. An experiment aimed at measuring the masses of proton-rich nuclei in the mass region A ≈ 60–80 has been performed, using a direct time-of-flight technique in conjunction with SISSI and the SPEG spectrometer at GANIL. The nuclei were produced via the fragmentation of a 78 Kr beam (73 meV/nucleon). A novel technique for the purification of the secondary beams, based on the stripping of the ions and using the α and the SPEG spectrometers, was succesfully checked. It allows for good selectivity without altering the beam quality. Secondary ions of 100 Ag, 100 Cd, 100 In and 100 Sn were produced via the fusion-evaporation reaction 50 Cr + 58 Ni at an energy of 5.1 MeV/nucleon, and were accelerated simultaneously in the second cyclotron of GANIL (CSS2). About 10 counts were observed from the production and acceleration of 100 Sn 22+ . The masses of 100 Cd, 100 In and 100 Sn were measured with respect to 100 Ag using the CSS2 cyclotron, with precisions of 2 × 10 −6 , 3 × 10 −6 and 10 −5 respectively.

The Mass Programme at GANIL Using the CSS2 and CIME Cyclotrons

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.

A cyclotron as a powerful tool for mass measurements of exotic nuclei

Abstract An original method using the second cyclotron of GANIL as a high resolution mass spectrometer was recently developed to measure the masses of exotic nuclei. This direct time of flight technique has been successfully used with A = 100 isobars in the vicinity of 100Sn, produced via the fusion-evaporation reaction 50 Cr + 58 Ni at 255 MeV. The secondary ions were simultaneously accelerated and detected inside the cyclotron close to the extraction radius, using a silicon detector telescope mounted on a radially movable probe. The cyclotron was first tuned, using this detection system, with the 50Cr11+ primary beam degraded to the same velocity as the A = 100 secondary ions. This very critical and quite tricky preliminary tuning procedure, as well as the mass determination procedure, which are common to all the experiments using this method, are presented and discussed.

Investigation by pXRF of Caltagirone Pottery Samples Produced in Laboratory

Abstract In the study of archaeological ceramics, it is important to have compositional data to identify their origin and source. The fabric also provides useful information on the production technology, especially with regard to the firing steps. The work presented here is connected to this field and focuses on the main parameters related to the terracotta artefacts preparation. Thus, one can consider the effects in terracotta characteristics of different raw materials and firing parameters, in particular for pottery of Caltagirone, which is one of most important centres of pottery production in Italy, active since the Neolithic. To this end, terracotta samples have been reproduced in a laboratory setting according to the ancient procedure of Caltagirone manufacture, starting from clay and degreaser extraction in local historical sites. The analysis was conducted using a portable X-Ray Fluorescence (pXRF) spectrometer for elemental characterization of sand degreaser and of clays during each step of the realization process and in different firing conditions. SEM-ED techniques were also employed to verify the method and results for some of the samples after firing process. Framing the technological context of manufacture production, known in the specific case, it is also possible to identify potential outcomes and limits in the study of potsherds using pXRF technology, in applying the methodology to historic artefacts.

Direct mass measurement of N ∼ Z nuclei with A = 64-80 using the CSS2 cyclotron

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 68Se and 80Y are −53.958(246) MeV and −60.971(180) MeV, respectively. The new results for 68Se and 80Y are compared to other recent experimental values.

Mass measurements far from stability around theN=Z line (100Sn,100In,100Cd)

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.