Technical and scientific performance of the prototype Schwarzschild-Couder telescope for CTA

The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma rays. One candidate design for CTA's medium-sized telescopes consists of the Schwarzschild-Couder Telescope (SCT), featuring innovative dual-mirror optics. The SCT project has built and is currently operating a 9.7-m prototype SCT (pSCT) at the Fred Lawrence Whipple Observatory (FLWO); such optical design enables the use of a compact camera with state-of-the art silicon photomultiplier detectors. A partially-equipped camera has recently successfully detected the Crab Nebula with a statistical significance of 8.6 standard deviations. A funded upgrade of the pSCT focal plane sensors and electronics is currently ongoing, which will bring the total number of channels from 1600 to 11328 and the telescope field of view from about 2.7° to 8° . In this work, we will describe the technical and scientific performance of the pSCT

Spurious ferromagnetic remanence detected by hybrid magnetometer

Nuclear magnetic resonance detection in ultra-low-field regime enables the measurement of different components of a spurious remanence in the polymeric material constituting the sample container. A differential atomic magnetometer detects simultaneously the static field generated by the container and the time-dependent signal from the precessing nuclei. The nuclear precession responds with frequency shifts and decay rate variations to the container magnetization. Two components of the latter act independently on the atomic sensor and on the nuclear sample. A model of the measured signal allows a detailed interpretation on the basis of the interaction geometry. Published under license by AIP Publishing

ToF diagnostic of Tin resonant laser photoionization in SPES laser offline laboratory

Tin is the principal element of interest in the SPES ISOL facility, which is under construction at Legnaro INFN Laboratories. Atomic nuclei have a shell structure in which nuclei with 'magic numbers'of protons and neutrons are analogous to the noble gasses in atomic physics. In particular, recent theoretical studies, reveal double-magic nature of radioactive Sn-132. For this reason the nuclear physics community demonstrated, in the last years, a huge interest to produce and study this radioactive neutron rich isotope. Experiments on Tin laser resonant ionization have been performed in the offline SPES laser laboratory to investigate the capability of the new home-made Time of Flight (ToF) mass spectrometer. Several three-step, two color ionization schemes have been tested by comparing fast and slow optogalvanic signals from a Tin Hollow Cathode Lamp (HCL) and Time of Flight signals from the spectrometer. By scanning the wavelength of one of the two dye lasers across the specific resonance, comparisons of ionization signals from both the ToF and the HCL have been made, finding perfect agreement. Furthermore, with the mass spectrometer, resolved peaks of all the natural Tin isotopes have been detected. The natural abundances extracted from these measurements are in agreement with the table values for Tin isotopes. This work, with comparison of OGE and ToF signals, confirm the fully functional SPES offline laser laboratory capability in order to develop scheme studies also for the other possible Radioactive Ion Beam (RIB) elements

Dynamics of Optical Pumping Processes in Coated Cells Filled with Rb Vapour

A better theoretical understanding of the atom – surface interactions and of the experimental consequences and applications to a reproducible method for the construction of reliable coated absorption cells is the main scope of our research. In this paper we report on the influence of diode laser intensity and of diode frequency scanning rate on the spectrum of the D2 line of Rb atoms, contained in paraffin or PolyDiMethylSiloxane (PDMS) coated glass cells. The anti-relaxation coating of inner walls of the glass cells allows to extend the optical orientation of atoms induced by the light to the entire cell volume and atomic velocity distribution. Moreover, in order to further investigate the role of atoms adsorbed in the anti-relaxation coatings, the D2 line spectra are compared for two cases: without and with illumination of the walls of the cell by an ultraviolet lamp. A theoretical model based on rate equations is introduced in order to analyze the experimental results. The extracted behaviour is a simple method to test the conditions of a coated surface. This finds applications in all cases where timely assessment of an organic coating layer is critical, from vapour spectroscopy to magneto-optical trapping of rare and radioactive species

Observation of 7p²P₃/₂ -> 7d²D optical transitions in 209 and 210 francium isotopes

We report on the direct experimental observation of the 7pP23/2→7dD2 optical transitions in 209 and 210 francium isotopes. By continuously monitoring the fluorescence emitted by the isotopes collected in a magneto-optical trap (MOT), the electric dipole transitions 7pP23/2→7dD25/2 of Fr209, not yet experimentally observed, and 7pP23/2→7dD25/2, 7pP23/2→7dD25/2 of Fr210 were detected as sub-Doppler depletion dips of the cold atom population. This approach allowed unambiguous identification of the excited state hyperfine structures, even in the absence of a large stable vapor. Our findings demonstrate the effectiveness and the flexibility of fluorescence monitoring of trap depletion upon laser excitation, and broaden the experimental knowledge of francium isotopes and their electronic and nuclear properties. These results will have a relevant impact on ongoing researches for low-energy testing of fundamental symmetries with francium, from atomic parity non-conservation to the electron dipole moment

A new setup for the study of adsorption/desorption processes and nanoparticles formation in porous alumina

We present a setup devoted to the study of adsorption and desorption processes of alkali atoms after deposition on a 300 nm thick porous alumina substrate in an Ultra High Vacuum chamber. Rubidium atoms, delivered by a dispenser source, enter the 20-30 nm diameter pores, diffuse in and stick to their walls. A 1 W power laser is used in order to induce detachment and take the atoms back in the vapor phase in a very tight confinement region. The desorbed atoms coming out the sample can be monitored via both a resonant optical detection and an electronic amplifier after ionization. The desorbing laser is also able to promote the formation of Rubidium nanoparticles, as the high Rb vapor density in the pores favors aggregation around nucleation point defects. In this way, the apparatus allows for the study of the fundamental processes related to atom – surface interactions in presence of light as well as of several promising application to nanomaterials