arXiv subjects
Publications and source records attributed to M. Guarise.
A novel photodetector based on a MCP-PMT vacuum tube with encapsulated CMOS ASIC has been tested at the CERN SPS high energy hadron beam, allowing single photon Cherenkov detection operating at 10$^4$ gain and with timing resolution of about 280~ps.
The Deep Underground Neutrino Experiment (DUNE) is a long-baseline neutrino experiment based in the USA and composed of a Near Detector (ND) complex at Fermi National Laboratory (FNAL), and a Far Detector (FD) complex located at the Sanford Underground Research Facility (SURF) $\sim$1300\,km distant. DUNE will study neutrino oscillations looking for unresolved issues of the Standard Model of particle physics (SM) such as CP violation in the leptonic sector, neutrino mass ordering and others, starting from the early 2030s. The FD, with a mass of $\sim$17\,kt, that will exploit both ionization and scintillation signals to detect neutrino interactions with Argon. Scintillating photons in LAr will be detected by the photon detection system (PDS) based on light collectors coupled to Silicon Photomultipliers (SiPMs). During a test campaign, different laboratories of the collaboration performed an investigation of the best SiPM candidates that fulfill the DUNE FD requirements. We identified two models of SiPM, produced by Hamamatsu Photonics K.K. (HPK) and Fondazione Bruno Kessler (FBK), respectively. In this paper, we focus on the FBK selected model showing its main features. We will describe the characterization protocol, the results at both room and cryogenic temperatures and the photon detection efficiency measurements.
The photon detection system of the first far detector (FD1-HD) of the DUNE experiment will detect scintillation photons produced by particle interactions in a kiloton-scale liquid Argon time projection chamber. The photon detectors of choice are silicon photomultipliers (SiPM), 6$\times$6 mm$^2$ each, arranged in groups of 48, which present a significantly low impedance to the front-end electronics. This paper details the design of a cryogenic amplifier with exceptionally low white voltage noise of 0.37 nV$\sqrt{Hz}$, based on a silicon-germanium input transistor and a BiCMOS fully differential operational amplifier. It yields excellent single photoelectron resolution even at low overvoltage values. The signal rise time is below 100 ns, and the dynamic range is about 2000 photoelectrons at the typical operating overvoltage. It draws 0.7 mA from a single 3.3 V supply, for a power consumption of 2.4 mW per channel. Simplified models were developed to predict the single photolectron signal shape and the signal to noise ratio, with a good match to measured performance.
We present the development of a single-photon detector and the connected read-out electronics. This `hybrid' detector is based on a vacuum tube, transmission photocathode, microchannel plate and a pixelated CMOS read-out anode encapsulating the analog and digital-front end electronics. This assembly will be capable of detecting up to $10^9$ photons per second with simultaneous measurement of position and time. The pixelated read-out anode used is based on the Timepix4 ASIC ($65~\mathrm{nm}$ CMOS technology) designed in the framework of the Medipix4 collaboration. This ASIC is an array of $512\times448$ pixels distributed on a $55~\mathrm{μm}$ square pitch, with a sensitive area of $\sim 7~\mathrm{cm}^2$. It features $50$-$70~\mathrm{e^{-}}$ equivalent noise charge, a maximum rate of $2.5~\mathrm{Ghits/s}$, and allows to time-stamp the leading-edge time and to measure the Time-over-Threshold (ToT) for each pixel. The pixel-cluster position combined with its ToT information will allow to reach $5$-$10~\mathrm{μm}$ position resolution. This information can also be used to correct for the leading-edge time-walk achieving a timing resolution of the order of $10~\mathrm{ps}$. The detector will be highly compact thanks to the encapsulated front-end electronics allowing local data processing and digitization. An FPGA-based data acquisition board, placed far from the detector, will receive the detector hits using $16$ electro-optical links operated at $10.24~\mathrm{Gbps}$. The data acquisition board will decode the information and store the relevant data in a server for offline analysis. These performance will allow significant advances in particle physics, life sciences, quantum optics or other emerging fields where the detection of single photons with excellent timing and position resolutions are simultaneously required.
The capture of scintillation light emitted by liquid Argon and Xenon under molecular excitations by charged particles is still a challenging task. Here we present a first attempt to design a device able to grab sufficiently high luminosity in order to reconstruct the path of ionizing particles. This preliminary study is based on the use of masks to encode the light signal combined with single-photon detectors. In this respect, the proposed system is able to detect tracks over focal distances of about tens of centimeters. From numerical simulations it emerges that it is possible to successfully decode and recognize signals, even complex, with a relatively limited number of acquisition channels. Such innovative technique can be very fruitful in a new generation of detectors devoted to neutrino physics and dark matter search. Indeed the introduction of coded masks combined with SiPM detectors is proposed for a liquid-Argon target in the Near Detector of the DUNE experiment.
thermal radiation emitted by a %hot cobalt wire in the temperature range from \(T\approx 400\,\)K up to melting. The radiation is linearly polarized perpendicular to the wire. \(P\) decreases from \(30\,\%\) just above room temperature down to \(6.5\,\%\) near melting and does not show any particular behavior neither at the martensitic {\em hcp}$-${\em fcc} transition at \(\approx 700\,\)K nor at the Curie point at \( \approx 1400\,\)K. However, \(P\) shows a rapid decrease for \(T\gtrsim 1000\,\)K and, contrary to previous measurements with tungsten wires, it hysteretically behaves if the temperature change is reversed. This behavior is rationalized by %taking into account accounting for the irreversible thermal demagnetization of the wire with magnetic domain size change.
We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy $m_a c^2$. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy ($\sim $ hundreds of $μ$eV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of $4f^N$ electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range $1.9-4.2$ K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.
We have studied the cathodo- and radioluminescence of Nd:YAG and of Tm:YAG single crystals in an extended wavelength range up to $\approx 5\,μ$m in view of developing a new kind of detector for low-energy, low-rate energy deposition events. Whereas the light yield in the visible range is as large as $\approx 10^{4}\,$photons/MeV, in good agreement with literature results, in the infrared range we have found a light yield $\approx 5\times 10^{4}\,$photons/MeV, thereby proving that ionizing radiation is particularly efficient in populating the low lying levels of rare earth doped crystals.
We propose a new technique to measure the infrared scintillation light yield of rare earth (RE) doped crystals by comparing it to near UV-visible scintillation of a calibrated Pr:(Lu$_{0.75}$Y$_{0.25}$)$_{3}$Al$_5$O$_{12}$ sample. As an example, we apply this technique to provide the light yield in visible and infrared range up to \SI{1700}{nm} of this crystal.
We demonstrate an all-optical method for manipulating the magnetization in a 1-mm YIG (yttrium-iron-garnet) sphere placed in a $\sim0.17\,$T uniform magnetic field. An harmonic of the frequency comb delivered by a multi-GHz infrared laser source is tuned to the Larmor frequency of the YIG sphere to drive magnetization oscillations, which in turn give rise to a radiation field used to thoroughly investigate the phenomenon. The radiation damping issue that occurs at high frequency and in the presence of highly magnetizated materials, has been overcome by exploiting magnon-photon strong coupling regime in microwave cavities. Our findings demonstrate an effective technique for ultrafast control of the magnetization vector in optomagnetic materials via polarization rotation and intensity modulation of an incident laser beam. We eventually get a second-order susceptibility value of $\sim10^{-7}$ cm$^2$/MW for single crystal YIG.
We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at $1064\,$nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO$_3$), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.
We report about a novel scheme for particle detection based on the infrared quantum counter concept. Its operation consists of a two-step excitation process of a four level system, that can be realized in rare earth-doped crystals when a cw pump laser is tuned to the transition from the second to the fourth level. The incident particle raises the atoms of the active material into a low lying, metastable energy state, triggering the absorption of the pump laser to a higher level. Following a rapid non-radiative decay to a fluorescent level, an optical signal is observed with a conventional detectors. In order to demonstrate the feasibility of such a scheme, we have investigated the emission from the fluorescent level $^4$S$_{3/2}$ (540 nm band) in an Er$^{3+}$-doped YAG crystal pumped by a tunable titanium sapphire laser when it is irradiated with 60 keV electrons delivered by an electron gun. We have obtained a clear signature this excitation increases the $^{4}I_{13/2}$ metastable level population that can efficiently be exploited to generate a detectable optical signal.
Using low-energy projection of the one-band t-t'-t"-Hubbard model we derive an effective spin-Hamiltonian and its spin-wave expansion to order 1/S. We fit the spin-wave dispersion of several parent compounds to the high-temperature superconducting cuprates: La2CuO4, Sr2CuO2Cl2 and Bi2Sr2YCu2O8. Our accurate quantitative determination of the one-band Hubbard model parameters allows prediction and comparison to experimental results of measurable quantities such as staggered moment, double occupancy density, spin-wave velocity and bimagnon excitation spectrum and density of states, which is discussed in relation to K-edge RIXS and Raman experiments.
We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$ and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$ excitations and we extensively studied their polarization and scattering geometry dependence. In a pure ionic picture, we calculated the theoretical cross sections for those excitations and used them to fit the experimental data with excellent agreement. By doing so, we were able to determine the energy and symmetry of Cu-3$d$ states for the four systems with unprecedented accuracy and confidence. The values of the effective parameters could be obtained for the single ion crystal field model but not for a simple two-dimensional cluster model. The firm experimental assessment of $dd$ excitation energies carries important consequences for the physics of high $T_c$ superconductors. On one hand, having found that the minimum energy of orbital excitation is always $\geq 1.4$ eV, i.e., well above the mid-infrared spectral range, leaves to magnetic excitations (up to 300 meV) a major role in Cooper pairing in cuprates. On the other hand, it has become possible to study quantitatively the effective influence of $dd$ excitations on the superconducting gap in cuprates.
Using high-resolution resonant inelastic x-ray scattering (RIXS), we performed a momentum-resolved study of magnetic excitations in the model spin-1/2 2D antiferromagnetic insulator Sr_2CuCl_2O_2. We identify both a single-spin-wave feature and a multi-magnon continuum, and show that the X-ray polarization can be used to distinguish these two contributions in the cross-section. The spin-waves display a large (70 meV) dispersion between the zone-boundary points ($π$,0) and ($π$/2,$π$/2). Employing an extended $t$-$t'$-$t"$-$U$ one-band Hubbard model, we find significant electronic hopping beyond nearest-neighbor Cu ions. We conclude that sizeable extended magnetic interactions are present in \scoc{} and probably important in all undoped cuprates.
We present a detailed analysis of resonant inelastic scattering (RIXS) from Fe$_{1.087}$Te with unprecedented energy resolution. In contrast to the sharp peaks typically seen in insulating systems at the transition metal $L_3$ edge, we observe spectra which show different characteristic features. For low energy transfer, we experimentally observe theoretically predicted many-body effects of resonant Raman scattering from a non-interacting gas of fermions. Furthermore, we find that limitations to this many-body electron-only theory are realized at high Raman shift, where an exponential lineshape reveals an energy scale not present in these considerations. This regime, identified as emission, requires considerations of lattice degrees of freedom to understand the lineshape. We argue that both observations are intrinsic general features of many-body physics of metals.