Eugenio Monticone

Photon-number discriminating superconducting transition-edge sensors

Photon-number discriminating detectors are fundamental to new quantum photon-based standards. We report results on superconducting transition-edge sensors based on Ti/Au and Ti/Pd bilayers allowing pulses containing up to five photons to be discriminated.

Ti/Au Transition-Edge Sensors Coupled to Single Mode Optical Fibers Aligned by Si V-Groove

Transition-edge sensors (TESs) are promising micro-calorimeters for applications in the field of quantum information, quantum computation and metrology due to their photon-number resolving capability. Quantum efficiency (QE) is fundamental in single-photon detection and it should be as high as possible. For this reason the coupling between the light source and the sensor plays a crucial role.

Investigation of Ti/Pd Bilayer for Single Photon Detection

Transition-edge sensor (TES) microcalorimeters are promising for application in the field of quantum information and quantum computation thanks to their outstanding single photon detection capabilities. Good energy resolution and photon number discrimination at visible and near-infrared wavelengths make them extensively used as single photon detectors. In this work we report details on the fabrication of Pd/Ti TESs deposited by e-beam evaporation on silicon nitride substrates. We use Pd as alternative to Au layer thanks to its stronger influence on the Ti layer, that allows to obtain the same temperature reduction with thinner layers. The transition temperatures Tc of the devices range from 83 to 110 mK with a transition width DeltaTc=0.5 mK. Thermal and electric characteristics of Pd/Ti TESs at different temperatures and its capability as single photon sensor are reported.

Optical Transition-Edge Sensors Single Photon Pulse Analysis

Transition-edge sensors (TES) are detectors able to count single photons from x-ray to infrared, generating pulses with amplitudes proportional to the absorbed photon energy. The TES performance depends on the sensor parameters and also on the noise level. The evaluation of the energy resolution is thus dependent on the type of signal analysis applied.

Reduced Active Area in Transition-Edge Sensors for Visible-NIR Photon Detection: A Comparison of Experimental Data and Two-Fluid Model

Transition-edge sensors (TESs) are very versatile superconducting devices used to detect radiation from gamma-rays to visible and submillimeter. The intrinsic capability to measure the energy of the absorbed photons with very high energy resolution and the related possibility to resolve the number of incident photons distinguish photon-number resolving (PNR) devices from any other photon detectors. PNR detectors are fundamental for the measurement of the photon-number distribution of singlephoton emitters and for the progress of quantum information technology and quantum metrology. By reducing the active area of TESs for visible-NIR light from typical values of 10-10 m2 toward 10-12 m2 and by increasing the TES operating temperature, we should be able to combine the high energy resolution permitted by very low heat capacity with fast response time. To support the future design and development of this new type of detector, in this work we compare experimental data with circuit simulation results based on the two-fluid theory.

Thin-film thermopiles in microcalorimeters

Abstract Microcalorimeters are special devices used for effective efficiency measurements of bolometric power sensors. The performance of the microcalorimeters, such as their sensitivity and accuracy, is mainly dependent on the thermoelectric detector. It can be improved by using thin-film thermopiles (copper-constantan or nickel-chrome) as an alternative to the traditional thermopile with bulky junctions. A thin-film thermopile specially designed for a microcalorimeter is described and experimental results are reported.

Enhancement of T/sub c/ in MgB/sub 2/ thin films by laser local annealing

Films of magnesium diboride are promising for superconducting electronic and for detector applications. One of the main obstacles for device fabrication by traditional lithography is the sensitivity of this material to the chemical solutions normally employed in the standard structuring process. Moreover, underetching often limits the patterns resolution. By focused laser beam, high temperature can be reached suddenly in areas of few micrometer square, therefore in principle MgB/sub 2/ film patterning is feasible by local laser modification. In this work we investigate the effect of laser processing on MgB/sub 2/ thin films deposited by in-situ method. Before the exposure to the laser, the strip was wirebonded to enable the resistance to be monitored during the experiment. Increasing the power from 0.1 to 1 Watt, the room temperature resistance of the stripline increased until reaching the open circuit for higher laser power. By optical inspection, we observed that the color of irradiated area changed from yellow to black. The structure defined by laser presented a periodicity of about 1.7 /spl mu/m, where the width of each tracks was 1.5 /spl mu/m, thus comparable to the laser spot size. The T/sub c/ of the strip was increased by the laser process. This technique open the possibility to pattern superconducting film for device fabrication and circuits.

New development of HgI2 X-ray and soft gamma ray detector for synchrotron radiation research and dosimetry applications

Abstract This paper describes recent progress in the development of HgI2 as an X-ray and soft γ-ray detector for synchrotron radiation research and dosimetry application. The high efficiency of the detector depends on the photon absorption inside the crystal and on the free charge carrier collection at the electrodes under the influence of the applied bias. The dominant mechanisms determining the collection of charge carriers, produced by incident ionizing radiations, are the trapping-detrapping phenomena and the carrier drift mobility. The relative role of these two mechanisms, photon absorption and carrier collection, is related to the thickness of the HgI2 crystal. The analysis of trapping-detrapping phenomena, which are strongly related to the detector fabrication process, are discussed and the measurement of the carrier drift mobility, cutting the crystal parallel and perpendicular to the c-axis, is presented. The results of energy resolution measurements obtained exposing HgI2 detector prototypes of different thickness and with the electrodes realized by evaporizing different metals on the crystal surface, to X- and γ-radiactive source, are presented and discussed. We have found, using a 900-μm-thick detector with 500 A Pd electrodes evaporated on both surfaces (sandwich arrangement), an energy resolution equal to 600 eV at 5.9 keV X-ray (Mn-Kα) and 10.5 keV at 122 keV γ-ray (57Co).

A power supply with temperature and N2 level test controlled by a PC IBM-XT for a HP-Ge detector

Abstract A high voltage power supply controlled by a PC IBM-XT has been constructed, to work in connection with a HP-Ge detector. Extra controls of temperature and N 2 level have been realized on the same board.

Realization of a low noise preamplifier for low capacitance solid state detectors

Abstract In this paper we describe the project of realizing a low noise preamplifier for low capacitance solid state detectors that could match the needs of high resolution in nuclear physics and of high counting rates in high energy physics. We present a particular design and we give an evaluation of the electronic noise. Some applications to nuclear spectroscopy are presented and discussed.