Studies of Higgs boson pair production at the LHC

The most recent results of the ATLAS and CMS searches for Higgs boson pair production at the LHC using the full Run-2 data collected in proton-proton collisions at a center-of-mass energy of Vs = 13 TeV with an integrated luminosity of about 140 fb -1 are presented. The focus is on the analyses of most sensitive di-Higgs channels, bb-bb- , bb-yy- , and bb-TT, and their combination is in the non-resonant context, and a brief overview on the resonant processes and projections for the future data taking LHC runs are discussed

VUV-Vis optical characterization of Tetraphenyl-butadiene films on glass and specular reflector substrates from room to liquid Argon temperature

The use of efficient wavelength-shifters from the vacuum-ultraviolet to the photosensor's range of sensitivity is a key feature in detectors for Dark Matter search and neutrino physics based on liquid argon scintillation detection. Thin film of Tetraphenyl-butadiene (TPB) deposited onto the surface delimiting the active volume of the detector and/or onto the photosensor optical window is the most common solution in current and planned experiments. Detector design and response can be evaluated and correctly simulated only when the properties of the optical system in use (TPB film + substrate) are fully understood. Characterization of the optical system requires specific, sometimes sophisticated optical methodologies. In this paper the main features of TPB coatings on different, commonly used substrates is reported, as a result of two independent campaigns of measurements at the specialized optical metrology labs of ENEA and University of Tor Vergata. Measured features include TPB emission spectra with lineshape and relative intensity variation recorded as a function of the film thickness and for the first time down to LAr temperature, as well as optical reflectance and transmittance spectra of the TPB coated substrates in the wavelength range of the TPB emission

Versatile lithium fluoride thin-film solid-state detectors for nanoscale radiation imaging

Point defects in insulating materials are successfully used for radiation detectors. Among them, colour centres in lithium fluoride (LiF) are well known for application in dosimeters and in light-emitting devices and lasers. LiF thin-film detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging application with laboratory radiation sources, e.g. laser-driven plasma sources and conventional X-ray tubes, as well as large-scale facilities, e.g. synchrotrons and free-electron lasers. Among the peculiarities of these detectors, noteworthy ones are the very high intrinsic spatial resolution ( 1 cm2) and the wide dynamic range. Moreover, they are insensitive to ambient light and no development process is needed. The latent images stored in the LiF thin layer can be read with fluorescence optical microscopy techniques. These detectors prove to be highly versatile, as LiF is sensitive to almost any kind of radiation, including charged particles and neutrons, and can be grown in the form of polycrystalline thin films, whose photoluminescence response can be tailored trough the control of the growth conditions

Fully-digital low-frequency lock-in amplifier for photoluminescence measurements

Lock-in amplifiers, used in several experimental physics applications, are instruments performing quadrature demodulation, which is useful when signals are affected by much noise. Generally, commercially-available lock-in amplifiers are very accurate, but expensive, especially if their operating range includes radiofrequencies. In many applications, high precision is not necessary for the measurements, but it is preferable to have low-cost, low-weight, compactness and a user-friendly graphical unit interface. In this paper, we describe a new fully-digital low-frequency lock-in amplifier developed at ENEA C.R. Frascati Laboratories for photoluminescence experiments based on an innovative low-cost architecture and processing algorithms. The hardware, firmware and software developed for the whole photoluminescence measurement set-up is presented. The present lock-in was first characterized with synthetic electrical sine wave signals and white noise. A dynamic reserve of 43 dB and a noise figure in the range of 25–44 dB were estimated. These results show compatibility with several measurement applications, such as photoluminescence, and the adequacy of the resolutions with respect to the hardware costs. Finally, preliminary results of photoluminescence measurements are presented

Optical spectroscopy and microscopy of radiationinduced light-emitting point defects in lithium fluoride crystals and films

Broad-band light-emitting radiation-induced F₂ and F₃⁺ electronic point defects, stable and laser-active at room temperature in lithium fluoride crystals and films, find applications in dosimeters, tuneable color-center lasers, broad-band miniaturized light sources and in novel radiation imaging detectors. A brief review of their photoemission properties is presented, and their peculiarities at liquid nitrogen temperature are discussed. A few experimental results about optical spectroscopy and fluorescence microscopy of these radiation-induced point defects in LiF crystals and thin films are presented to obtain information about the coloration curves, the point defects formation efficiency, the effects of the photo-bleaching processes, and so on. The control of local formation, stabilization and transformation of radiation-induced light-emitting defect centers is crucial for the development of optical active micro-components and nanostructures. Some of the advantages of low temperature measurements for novel confocal laser scanning fluorescence microscopy techniques, widely used for the spatial mapping of these point defects thorough the optical reading of their visible photoluminescence, are highlighted

Photoluminescence of radiation-induced color centers in lithium fluoride thin films for advanced diagnostics of proton beams

Systematic irradiation of thermally evaporated 0.8 μm thick polycrystalline lithium fluoride films on glass was performed by proton beams of 3 and 7 MeV energies, produced by a linear accelerator, in a fluence range from 1011 to 1015 protons/cm2. The visible photoluminescence spectra of radiation-induced F2 and F3+ laser active color centers, which possess almost overlapping absorption bands at about 450 nm, were measured under laser pumping at 458 nm. On the basis of simulations of the linear energy transfer with proton penetration depth in LiF, it was possible to obtain the behavior of the measured integrated photoluminescence intensity of proton irradiated LiF films as a function of the deposited dose. The photoluminescence signal is linearly dependent on the deposited dose in the interval from 103 to about 106 Gy, independently from the used proton energies. This behavior is very encouraging for the development of advanced solid state radiation detectors based on optically transparent LiF thin films for proton beam diagnostics and two-dimensional dose mapping

High resolution and high efficiency coloration of lithium fluoride by soft X-rays irradiation

The efficient coloration of LiF material, in the form of bulk and films, by EUV and soft X-rays emitted by a laser-plasma source is demonstrated. The short penetration depth of soft-X-rays is exploited to obtain high spatial resolution luminescent patterns while the high dynamic range of proportionality between X-ray dose and coloration is exploited for using LiF as image detector in micro-radiography and soft X-ray microscopy applications

Advanced spectroscopic investigation of colour centres in LiF crystals irradiated with monochromatic hard x-rays

Nominally-pure lithium fluoride (LiF) crystals were irradiated with monochromatic hard x-rays of energy 5, 7, 9 and 12 keV at the METROLOGIE beamline of the SOLEIL synchrotron facility, in order to understand the role of the selected x-ray energy on their visible photoluminescence (PL) response, which is used for high spatial resolution 2D x-ray imaging detectors characterized by a wide dynamic range. At the energies of 7 and 12 keV the irradiations were performed at five different doses corresponding to five uniformly irradiated areas, while at 5 and 9 keV only two irradiations at two different doses were carried out. The doses were planned in a range between 4 and 1.4 × 103 Gy (10.5 mJ cm−3 to 3.7 J cm−3), depending on the x-ray energy. After irradiation at the energies of 7 and 12 keV, the spectrally-integrated visible PL intensity of the F2 and F3+ colour centres (CCs) generated in the LiF crystals, carefully measured by fluorescence microscopy under blue excitation, exhibits a linear dependence on the irradiation dose in the investigated dose range. This linear behaviour was confirmed by the optical absorption spectra of the irradiated spots, which shows a similar linear behaviour for both the F2 and F3+ CCs, as derived from their overlapping absorption band at around 450 nm. At the highest x-ray energy, the average concentrations of the radiation-induced F, F2 and F3+ CCs were also estimated. The volume distributions of F2 defects in the crystals irradiated with 5 and 9 keV x-rays were reconstructed in 3D by measuring their PL signal using a confocal laser scanning microscope operating in fluorescence mode. On-going investigations are focusing on the results obtained through this z-scanning technique to explore the potential impact of absorption effects at the excitation laser wavelength

Thermal neutron detection by means of Timepix3

Thermal neutron detection plays a crucial role in numerous scientific and technical applications such as nuclear reactor physics, particle accelerators, radiotherapy,materials analysis and space exploration. There are several challenges associated with the accurate identification and quantification of thermal neutrons. The present work proposes a detailed characterization of a Timepix3 (TPX3) detector equipped with a Lithium Fluoride (6LiF) converter in order to study its response to thermal neutrons that are identified through the 6Li(n,α)3H reaction. The TPX3-based test system has been installed at the HOTNES facility in ENEA and the analysis highlighted its excellent performance showing high effectiveness in the identification of neutrons through morphological analysis of tracks produced by alpha and triton particles, after accurate discrimination from the gamma background. With the use of Monte Carlo simulations, it has been demonstrated that the main contribution is due to tritons and its signal can be used effectively in the identification of thermal neutrons obtaining an efficiency of 0.9 % for 25 meV neutrons. This allows the TPX3 to have important applications as an environmental monitor for thermal neutrons. This monitoring system can be simply realized and is easy to manage because of its compact size and its digital acquisition that allows a real-time analysis

Beam commissioning of the 35 MeV section in an intensity modulated proton linear accelerator for proton therapy

This paper presents the experimental results on the Terapia Oncologica con Protoni-Intensity Modulated Proton Linear Accelerator (TOP-IMPLART) beam that is currently accelerated up to 35 MeV, with a final target of 150 MeV. The TOP-IMPLART project, funded by the Innovation Department of Regione Lazio (Italy), is led by Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) in collaboration with the Italian Institute of Health and the Oncological Hospital Regina Elena-IFO. The accelerator, under construction and test at ENEA-Frascati laboratories, employs a commercial 425 MHz, 7 MeV injector followed by a sequence of 3 GHz accelerating modules consisting of side coupled drift tube linac (SCDTL) structures up to 71 MeV and coupled cavity linac structures for higher energies. The section from 7 to 35 MeV, consisting on four SCDTL modules, is powered by a single 10 MW klystron and has been successfully commissioned. This result demonstrates the feasibility of a “fully linear” proton therapy accelerator operating at a high frequency and paves the way to a new class of machines in the field of cancer treatment