The lifetime of the 6.79 MeV state in 15O as a challenge for nuclear astrophysics and gamma-ray spectroscopy: a new DSAM measurement with the AGATA Demonstrator array

The determination of the thermonuclear reaction rates is a challenging task of nuclear astrophysics. In order to investigate this and other nuclear processes in the stellar medium, new techniques and new advanced setups for nuclear physics experiments are of vital importance. In this Thesis an advanced γ-ray spectroscopy system has been used in an experiment of astrophysical interest, that is a new Doppler shift attenuation measurement of the lifetime of the 6.79MeV state in 15O. An accurate measurement of this quantity is of paramount importance in the determination of the astrophysical S-factor and the derived cross section for the 14N(p, γ)15O reaction, the slowest one in the CNO cycle. The results of a new direct measurement of this nuclear level lifetime are discussed. The first excited states in 15O (and 15N) were populated via fusion-evaporation and Nucleon-transfer reactions of 14N on 2H (implanted at the surface of a ≈4 mg=cm2 Au layer) at 32MeV beam energy, provided by the XTU Tandem at the Legnaro National Laboratories. Gamma rays were detected with 4 triple clusters of the AGATA Demonstrator array, placed at backward angles, allowing to measure the angular distribution of the emitted γ rays in a continuous way. The energy resolution and position sensitivity of this state-of-the-art gamma spectrometer have been exploited to investigate lifetimes of nuclear levels in the ≈fs range via the Doppler Shift Attenuation Method. The deconvolution of the lifetime effects on the line-shapes of the gamma peaks from the ones due to the kinematics of the emitting nuclei has been performed by means of detailed Monte Carlo simulations of the gamma emission and detection. Coupled-channel calculations for the nucleon transfer process have been used for this purpose. Being one of the first experiments using this state-of-the-art γ ray spectroscopy tool, particular emphasis will be put in the description of the not trivial data replay and analysis, as well as the development of an ad hoc simulation tool. The comparison of experimental and simulated spectra of high-energy gamma-rays, de-exciting levels with lifetimes in the few fs range, will be shown for the 6.79MeV transition in 15O and for known cases in 15N, together with details of the chi-square analysis. Lifetime estimates for excited levels in 15N will be given and compared with previous results. The data analysis allows to give a new limit to the lifetime of the 6.79MeV state in 15O

LA FIGURA DEL SINDACO E LE ORDINANZE IN QUALITA' DI UFFICIALE DEL GOVERNO

la ricerca, dopo un inquadramento storico della figura del Sindaco, analizza le ordinanze di necessità e urgenza sindacali. In particolare, ampia trattazione viene effettuata sulle ordinanze di competenza del sindaco, in qualità di ufficiale di Governo, ex art. 54 Tuel, alla luce delle più recenti modifiche

AGATA: Performance of γ\gamma-ray tracking and associated algorithms

AGATA is a modern $\gamma$-ray spectrometer for in-beam nuclear structure studies, based on $\gamma$-ray tracking. Since more than a decade, it has been operated performing experimental physics campaigns in different international laboratories (LNL, GSI, GANIL). This paper reviews the obtained results concerning the performances of $\gamma$-ray tracking in AGATA and associated algorithms. We discuss $\gamma$-ray tracking and algorithms developed for AGATA. Then, we present performance results in terms of efficiency and peak-to-total for AGATA. The importance of the high effective angular resolution of $\gamma$-ray tracking arrays is emphasised, e.g. with respect to Doppler correction. Finally, we briefly touch upon the subject of $\gamma$-ray imaging and its connection to $\gamma$-ray tracking

Determination of gamma-ray widths in 15^{15}N using nuclear resonance fluorescence

The stable nucleus $^{15}$N is the mirror of $^{15}$O, the bottleneck in the hydrogen burning CNO cycle. Most of the $^{15}$N level widths below the proton emission threshold are known from just one nuclear resonance fluorescence (NRF) measurement, with limited precision in some cases. A recent experiment with the AGATA demonstrator array determined level lifetimes using the Doppler Shift Attenuation Method (DSAM) in $^{15}$O. As a reference and for testing the method, level lifetimes in $^{15}$N have also been determined in the same experiment. The latest compilation of $^{15}$N level properties dates back to 1991. The limited precision in some cases in the compilation calls for a new measurement in order to enable a comparison to the AGATA demonstrator data. The widths of several $^{15}$N levels have been studied with the NRF method. The solid nitrogen compounds enriched in $^{15}$N have been irradiated with bremsstrahlung. The $\gamma$-rays following the deexcitation of the excited nuclear levels were detected with four HPGe detectors. Integrated photon-scattering cross sections of ten levels below the proton emission threshold have been measured. Partial gamma-ray widths of ground-state transitions were deduced and compared to the literature. The photon scattering cross sections of two levels above the proton emission threshold, but still below other particle emission energies have also been measured, and proton resonance strengths and proton widths were deduced. Gamma and proton widths consistent with the literature values were obtained, but with greatly improved precision.Comment: Final published version, minor grammar changes, 10 pages, 4 figures, 8 tables; An addendum is published where the last section is revised: T. Sz\"ucs and P. Mohr, Phys. Rev. C 92, 044328 (2015) [arXiv:1510.04956

Is It Time to Call Time on Bone Marrow Biopsy for Staging Ewing Sarcoma (ES)?

Primary malignant bone sarcomas are rare and Ewing sarcoma (ES), along with osteosarcoma, predominates in teenagers and young adults. The well-established multimodality treatment incorporates systemic chemotherapy with local control in the form of surgery, with or without radiation. The presence and extent of metastases at diagnosis remains the most important prognostic factor in determining patient outcome; patients with skeletal metastases or bone marrow infiltration having a significantly worse outcome than those with lung metastases alone. There is, however, no accepted staging algorithm for ES. Large cooperative groups and national guidelines continue to advocate bone marrow biopsy (BMB) for staging but functional imaging techniques, such as 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) with computerised tomography (CT) have been increasingly used for staging cancers and whole-body magnetic resonance imaging (WB-MRI) for staging skeletal metastases. This review outlines the current literature, from which we conclude that BMB is no longer required for the staging of ES as it does not influence the standard of care management. BMB may, however, provide prognostic information and insights into the biology of ES in selected patients on prospective clinical trials

Improving Outcomes After Relapse in Ewing's Sarcoma: Analysis of 114 Patients From a Single Institution

The outcome for patients with relapsed Ewing's sarcoma is poor. A retrospective analysis was carried out to identify factors associated with improved survival. Between 1992 and 2002, 114 patients presented with relapsed or progressive disease. Median time to progression/relapse was 13 months (range, 2–128). Treatment at relapse included high dose treatment (HDT) in 29 patients, and surgery or definitive radiotherapy in 29. 2 and 5-year post relapse survival (PRS) was 23.5% and 15.2%, respectively. In multivariate analysis, the most significant factors associated with improved survival were disease confined locally or to the lungs (2-year PRS, 40% versus 6%; P < .001), relapse > 18 months from diagnosis (2-year PRS, 53% versus 8%; P < .001), HDT at relapse (2-year PRS, 62% versus 11%; P < .001), and surgery and/or radiotherapy at relapse (2-year PRS, 51% versus 14%; P < .001). First treatment failure in Ewing's sarcoma is mostly fatal. Improved survival can be achieved in selective patients with aggressive treatment. These improvements are confined to those without bone or bone marrow metastases