Building a VME spectrometer and testing Si PIN diode detector: a feasibility study for the first nuclear astrophysical experiments using a pelletron

This work presents the logical design, connections between NIM and VME elec­tronic modules, and the data acquisition programming to build a complete detector readout system. The test experiments were carried out with commercial silicon PIN diode S3590-09 bare detectors bombarded by charged particles from a 241Am α-source and Rutherford elastic backscattering (RBS) protons induced by 2.5 MeV proton beam bombarding on an Au-on-glass target, and with a NaI scintillation detector bombarded by gammas from 27Al(p, γ)28Si reaction with proton beam energy of 1.379 MeV. The test showed that the spectrometer operated steadily and its versatility for different kind of detector. The energy resolutions of the Si diodes were less than 0.5% energy of a charged particle, which satisfies the foreseen requirement for the upcoming experiments.

Combined use of Mie–Raman and fluorescence lidar observations for improving aerosol characterization: feasibility experiment

To study the feasibility of a fluorescence lidar for aerosol characterization, the fluorescence channel is added to the LILAS multiwavelength Mie–Raman lidar of Lille University, France. A part of the fluorescence spectrum induced by 355 nm laser radiation is selected by the interference filter of 44 nm bandwidth centered at 466 nm. Such an approach has proved to have high sensitivity, allowing fluorescence signals from weak aerosol layers to be detected and the fluorescence backscattering coefficient from the ratio of fluorescence and nitrogen Raman backscatters to be calculated. Observations were performed during the November 2019–February 2020 period. The fluorescence capacity (ratio of fluorescence to elastic backscattering coefficients), measured under conditions of low relative humidity, varied in a wide range, being the highest for the smoke and the lowest for the dust particles. The results presented also demonstrate that the fluorescence measurements can be used for monitoring the aerosol inside the cloud layers.

ELASTIC BACKSCATTERED CROSS-SECTIONS OF 14N(P,P0)14N AT HIGH ANGLES

The importance and present needs of proton cross section data of nitrogen needed by the Ion Beam Analysis (IBA) community are briefly reviewed. Previous experimental data presently used for the theoretical determination of the proton cross-sections are discussed. The Azure code based on the R-matrix formalism was then used to evaluate the data and to determine the nitrogen cross section in the previous and presently desired angular domain and energy region of interest. The experimental elastic backscattering cross section data, as spectra, for back-scattering analysis determined at angles in the laboratory frame of reference, θi,lab, of 165o, 170o and 176o are presented.

Combined use of Mie-Raman and fluorescence lidar observations for improving aerosol characterization: feasibility experiment

To study the feasibility of a fluorescence lidar for aerosol characterization, the fluorescence channel is added to LILAS – multiwavelength Mie-Raman lidar of Lille University, France. A part of fluorescence spectrum is selected by the interference filter of 44 nm bandwidth centered at 466 nm. Such an approach has demonstrated high sensitivity, allowing to detect fluorescence signal from weak aerosol layers (backscattering coefficient at 1064 nm is below 0.02 Mm−1 sr−1) up to a height of 5000 m. Simultaneous detection of nitrogen Raman and fluorescence backscatters allows to quantify the fluorescence backscattering coefficient. Observations were performed during November 2019–February 2020 period. The fluorescence capacity (ratio of fluorescence to elastic backscattering coefficients) varied in a wide range, being the highest for the smoke and the lowest for the dust particles. The fluorescence capacity depends as well strongly on the relative humidity, because the water uptake at the condition of high RH increases the elastic backscattering, without significant modification of the fluorescence. Thus, simultaneous measurements of Mie-Raman and fluorescence lidars open opportunity for the study of the particle hygroscopic growth. The fluorescence technique can be used also for monitoring the aerosol inside the cloud layers. The results presented demonstrate, that aerosol and cloud particles can be mixed both externally and internally. When the cloud is formed at the top or inside the aerosol layer (such scenario can be probably considered as internal mixing) we observed significant (up to factor 5) increase of fluorescence backscattering. Among possible mechanisms of such enhancement we can assume modification of the scattering phase function of the particles embedded in the water microspheres and the lens effect due to the water shell presence.

Measurement of differential cross sections of deuteron elastic scattering on 31P for EBS purposes

The 31P(d,d0)31P elastic scattering differential cross-sections were measured, for the first time, in the energy range Ed,lab=900-2400 keV, using a variable energy step, for elastic backscattering spectrometry (EBS) purposes. The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of the N.C.S.R. “Demokritos”, implementing a high precision goniometer. The experimental setup consisted of five silicon surface barrier (SSB) detectors, placed at the laboratory scattering angles between 130° and 170° (in steps of 10°). The target used was a thin GaP layer evaporated on a self-supporting carbon foil. To validate the obtained results, benchmarking measurements were performed, using a polished GaP crystal. The determined cross-section datasets are compared with the corresponding ones using Rutherford’s formula, and similarities and discrepancies will be discussed and analyzed.

Elastic backscattering measurments for 6,7Li+58Ni, 6,7Li+116,120Sn, 6,7Li+208Pb at near barrier energies

We have performed, elastic backscattering measurements for the weakly bound nuclei 6,7Li on the medium and heavy mass targets 58Ni, 116,120Sn, 208Pb at sub- and near-barrier energies (0.6 to 1.3 EC.b.). Excitation functions of elastic scattering cross sections have been measured at 160O and 170O and the corresponding ratios to Rutherford scattering and relevant barrier distributions have been extracted. These measurements will complement recent work on a 28Si target for probing the potential at sub- and near barrier energies and relevant reaction mechanisms.