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The search for neutrinoless double-beta (0νββ) decay is currently a key topic in physics, due to its possible wide implications for nuclear physics, particle physics, and cosmology. The NUMEN project aims to provide experimental information on the nuclear matrix elements (NMEs) that are involved in the expression of 0νββ decay half-life by measuring the cross section of nuclear double-charge exchange (DCE) reactions. NUMEN has already demonstrated the feasibility of measuring these tiny cross sections for some nuclei of interest for the 0νββ using the superconducting cyclotron (CS) and the MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS.) Catania, Italy. However, since the DCE cross sections are very small and need to be measured with high sensitivity, the systematic exploration of all nuclei of interest requires major upgrade of the facility. R&amp, D for technological tools has been completed. The realization of new radiation-tolerant detectors capable of sustaining high rates while preserving the requested resolution and sensitivity is underway, as well as the upgrade of the CS to deliver beams of higher intensity. Strategies to carry out DCE cross-section measurements with high-intensity beams were developed in order to achieve the challenging sensitivity requested to provide experimental constraints to 0νββ NMEs.

Radiochromic film dosimetry has been widely employed in most of the applications of radiation physics for over twenty years. This is due to a number of appealing features of radiochromic films, such as reliability, accuracy, ease of use and cost. However, current radiochromic film reading techniques, based on the use of commercial densitometers and scanners, provide values of dose only after the exposure of the films to radiation. In this work, an innovative methodology for the real-time reading of radiochromic films is proposed for some specific applications. The new methodology is based on opto-electronic instrumentation that makes use of an optical fiber probe for the determination of optical changes of the films induced by radiation and allows measurements of dose with high degree of precision and accuracy. Furthermore, it has been demonstrated that the dynamic range of some kinds of films, such as the EBT3 Gafchromic films (intensively used in medical physics), can be extended by more than one order of magnitude. Owing to the numerous advantages with respect to the commonly used reading techniques, a National Patent was filed in January 2018.

We report on a innovative Lab on Fiber (LOF) dosimeter for ionizing radiation monitoring at ultra-high doses. The new dosimeter consists in a metallo-dielectric resonator at sub-wavelength scale supporting localized surface plasmon resonances realized on the optical fiber (OF) tip. The resonating structure involves two gold gratings separated by a templated dielectric layer of poly(methyl methacrylate) (PMMA). Two LOF prototypes have been manufactured and exposed, at the IRRAD Proton Facility at CERN in Geneva, to 23 GeV protons for a total fluence of 0.67x10(16) protons/cm(2), corresponding to an absorbed dose of 1.8 MGy. Experimental data demonstrate the "radiation resistance" feature of the LOF devices and a clear dependence of the reflected spectrum on the total dose, expressed by a cumulative blue-shift of similar to 1.4 nm of the resonance combined with a slight increase of 0.16 dBm in the reflected spectrum. According to the numerical analysis and the literature, the main phenomenon induced by exposure to proton beam and able to explain the measured spectral behavior is the reduction of the PMMA thickness. Preliminary results demonstrated the potentiality of the proposed platform as dosimeter at MGy dose levels for High Energy Physics (HEP) experiments.

The present invention relates to a method and a system for real-time determination of characteristics of radio-chromic films, which is based on optical-fiber technology and allows determining the characteristics through real-time reading and from a remote location.

Commercial-off-the-shelf system-on-chip field-programmable gate arrays (FPGAs) are gaining momentum in space applications and their radiation characterization becomes crucial. This paper targets a cost-effective test setup and procedures for total ionization dose testing of miniaturized complex devices. We combine hardware and software techniques to perform on-chip irradiation via a 90Sr/90Y electron source and assess in detail the degradation of complex SRAM FPGAs. Our methodology combines multiple sensing mechanisms with correlation analysis to facilitate modeling of effects and tuning of a custom ring-oscillator network for future autonomous in-flight use. Focusing on 28-nm Zynq7000 devices, our results show Mrad total ionizing dose tolerance with parameters’ degradation in the area of 5%, zero functional errors, and nonuniform spatial response.

For the first time the Rutherford Back-Scattering Spectroscopy (RBS) technique has been successfully exploited for the measurement of the energy of a proton beam accelerated by the IBA Cyclone 18/18 medical cyclotron in operation at the Bern University Hospital. This accelerator, routinely used for radioisotope production for Positron Emission Tomography (PET) imaging is equipped with an external beam line devoted to research activities in several fields such as detector physics, medical applications of particle physics, accelerator physics. Recently a widespread request has raised for the availability of well characterized proton and neutron beams, particularly for radiation hardness studies and the development of new neutron detectors. A feasibility study for a future upgrade of the Bern cyclotron towards a neutron facility was started, which requires a complete and precise characterization of the proton beam. Along this line, the measurement of fundamental parameters of the primary proton beam, such as the maximum proton energy and its spread have been performed by means of the RBS technique with two different targets, namely gold and graphite foils.

A new methodology for Total Ionizing Dose (TID) tests is proposed. It is based on the employment of an on-chip 90Sr/90Y beta source as alternative to standard methods such as 60Co gamma rays and electrons from LINAC. The use of a compact beta source for TID tests has several advantages. In particular, the irradiation of devices with more than one radiation source results in a better representation of the complex space radiation environment composed of several types, energies and dose-rates. In addition, the use of an easy handling beta source allows the irradiation of electronic devices without any damage to other auxiliary circuit. In this work, 90Sr/90Y beta source dosimetry and related radiation field characteristics are discussed in depth. In order to validate the proposed source for TID tests, a rather complex device such as the “SPC56EL70L5” microcontroller from ST-Microelectronics was exposed to 90Sr/90Y beta rays. The results of this test were compared to that of a previous test of another sample from the same lot with a standard gamma 60Co source. The electronic performances following the two irradiations have been found to be in excellent agreement, by demonstrating therefore the validity of the proposed beta source for TID tests.

The tolerance to the cumulative effects of ionizing radiation is one of the most important parameters to keep into account when selecting an EEE component for space applications. TID sensitivity is normally investigated measuring changes induced by gamma rays from 60Co sources to nominal parameters of a component or to its expected functional behavior. In this work we propose an on-chip 90Sr/90Y electron source as an alternative methodology for TID tests.60Co and 90Sr/90Y TID test setups for a complex SoC are compared in terms of complexity and of experimental results, investigating the use of a 90Sr/90Y as well as the established 60Co. We show that 90Sr allows a simpler test setup, manages to reproduce specific modes of failure obtained with 60Co and causes failures at comparable total doses. This makes 90Sr an interesting alternative to 60Co qualification and the use of untested components, to be further investigated especially for complex COTS SoCs.

The use of System-on-Chip (SoC) solutions in the design of on-board data handling systems is an important step towards further miniaturization in space. However, the Total Ionizing Dose (TID) and Single Event Effects (SEE) characterization of these complex devices present new challenges that are either not fully addressed by current testing guidelines or may result in expensive, cumbersome test configurations. In this paper we report the test setups, procedures and results for TID testing of a SoC microcontroller both using standard C 60 o and low-energy protons beams. This paper specifically points out the differences in the test methodology and in the challenges between TID testing with proton beam and with the conventional gamma ray irradiation. New test setup and procedures are proposed which are capable of emulating typical mission conditions (clock, bias, software, reprogramming, etc.) while keeping the test setup as simple as possible at the same time.

In this work, we report on the first demonstration of Lab on Fiber (LOF) dosimeter for ionizing radiation monitoring at ultra-high doses. The new dosimeter consists in a metallo-dielectric resonator at sub-wavelength scale supporting localized surface plasmon resonances realized on the optical fiber (OF) tip. The resonating structure involves two gold gratings separated by a templated dielectric layer of poly(methyl methacrylate) (PMMA). Two LOF prototypes have been manufactured and exposed at the IRRAD Proton Facility at CERN in Geneva to 23 GeV protons for a total fluence of 0.67 × 1016 protons/cm2, corresponding to an absorbed dose of 1.8 MGy. Experimental data demonstrated the “radiation resistance” feature of the LOF devices and a clear dependence of the reflected spectrum versus the total dose, expressed by a cumulative blue-shift of ~1.4 nm of the resonance combined with a slight increase of 0.16 dBm in the reflected spectrum. The numerical analysis carried out to correlate the experimental results with the dimensional and physical properties of the resonator, expected to be tightly connected to the absorbed dose, suggests that the main phenomenon induced by exposure to proton beam and able to explain the measured spectral behavior is the reduction of the PMMA thickness, which is also consistent with past literature in the field. Preliminary results demonstrated the potentiality of the proposed platform as dosimeter at MGy dose levels for high energy physics experiments.

We have newly developed a Hybrid Photo-Detector (HPD) with 2-inch diameter. It consists of a bialkali photocathode and a 3 mm x 3 mm Multi-Pixel-Photon Counter (MPPC) sealed in a glass tube. The electric field inside the tube is designed so that photoelectrons emitted from the photocathode are collected in the MPPC, where photoelectrons are amplified. For conventional HPDs with an avalanche diode , extremely high voltage such as -8kV has to be provided to achieve gain sufficient for single photon detection. However, our HPD with MPPC has single photon sensitivity only with lower voltage like PMTs due to high gain of MPPC. In addition, this device can cover larger area with only one MPPC. These features enable us to easily handle high performance HPD in various applications, such as high energy physics, biomedical field etc. This test sample was produced in 2016, and we have checked its basic characteristics. The peak photocathode quantum efficiency was found to be very high of 37% at the wavelength of 340 nm. We have confirmed that HPD with MPPC has capability of single photon detection in low operation voltage less than -2 kV. This report will present detailed performance studies of this sample.

Radiochromic film dosimetry is a technique particularly suitable for dose measurements of radiation hardness assurance tests. The main characteristics of radiochromic films are the precise, accurate and permanent dose values, ease of handling and data analysis, high spatial resolution and wide range of dose. However, measurements of the trend of the dose in time with radiochromic films are very difficult by means of commercial read-out tools. In this work we propose a new method, for which a National Patent was filed, for the determination of the dose in real-time and by remote control with radiochromic films. This method based on optoelectronic instrumentation, makes radiochromic film dosimetry an ideal technique for radiation hardness quality assurance tests.

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a hybrid photodetector. The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a special SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier. The excellent photon counting capability, fast response, low power consumption and the stability are among the most attractive features of the VSiPMT.We now present the progress on the realization of a 1-in. prototype and the preliminary tests we are performing on it. © 2017 Elsevier B.V.

The continuous beam provided by the TTT-3 accelerator of the University of Naples have to be pulsed with 5 ns length bunch to allow experiments in many fields of the fundamental and applied physics. The characteristics of the first low energy chopper prototype and the results obtained during preliminary test with the beam are presented.

Projects attempting the direct detection of WIMP dark matter share the common problem of eliminating sources of background or using techniques to distinguish background events from true signals. Although experiments such as DarkSide have achieved essentially background free exposures through careful choice of materials and application of efficient veto techniques, there will still be a high burden of proof to convince the greater scientific community when a discovery is claimed. A directional signature in the data would provide extremely strong evidence to distinguish a true WIMP signal from that of an isotropic background. Two-phase argon time projection chambers (TPCs) provide an experimental apparatus which can both be scaled to the ton-scale size required to accommodate the low cross-section expected for WIMP interactions and have an anisotropy that could be exploited to evaluate the polar angles of the resulting nuclear recoils from WIMP collisions with target nuclei. Our studies show that even a modest resolution in the polar angle reconstruction would offer a powerful tool to detect a directional signature. In this contribution, the status of the ReD experiment, which is under construction at Naples University, will be also shown. The aim of the project is to assess and enhance the directionality of two-phase argon TPCs. ReD will use a small TPC exposed to a beam of mono-energetic neutrons to study the so called “columnar recombination” in liquid argon. This development could have high impact on the future experiments in the field, opening up the potential to find conclusive evidence for dark matter or disprove the WIMP hypothesis at and above the mass range explored by planned accelerator experiments.

This paper discusses radiation tests on complex System-on-Chip (SoC) controllers using Low-Energy Protons (LEPs). The aim of this novel set of guidelines is to be also applicable to System In Package (SIP) or hybrid components that are now often used to overcome printed circuit board's real estate restrictions in Hi-Rel electronics.

This paper presents an intended test setup and methodology for testing micro-controller SoCs against the effects of ionizing radiations. The method structure is based on a modular test sequence for test definition, coding, validation and setup. It will be illustrated by the relevant example of a microcontroller solution including lockstep options. Our methodology proposes using low-energy protons for irradiation, and this paper compares this approach with current techniques, showing how proton testing is becoming increasingly interesting, especially for ultra-deep submicron processes in proton dominated environments like low-shielded Low Earth Orbit missions or aircraft avionics. Beyond the convenience of a simplified test setup one of the main advantages of the proton irradiation approach is that it can be used for simultaneous Single Event Effects (SEE) and Total Ionizing Dose (TID) characterization, closer to the "test as you fly" approach.

The indirect effect of oxygen background gas on the La/Al ratio during the growth of LaAlO3 (LAO) films by pulsed laser deposition (PLD) is analyzed, in a pressure range between 10^-3 and 10^-1 mbar. We resort to two complementary investigation methods: Rutherford backscattering spectroscopy and spectrally resolved, time-gated imaging of the laser plume. The first technique allows us to analyze the stoichiometry of the deposited films, and the latter allows us to analyze the plume expansion phase of the PLD process by collecting chemically resolved two-dimensional images of the relevant atomic/molecular species. The comparison between the results obtained by the two techniques allows us to highlight the role of the plume-gas interaction in affecting cations stoichiometry. Our results indicate that, in the considered pressure range, the background oxygen pressure affects the cations stoichiometry of the LAO films, besides determining their oxygen content.

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research. Focusing the attention on photodetectors for particle astrophysics, the future experiments aimed at the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) will require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of these class of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube). The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as an electron detector and amplifier. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology.

Nowadays we live in the so-called "Silicon Era", in which devices based on the silicon technology permeate all aspects of our daily life. One can simply think how much silicon is in the everyday household objects, gadgets and appliances. The impact of silicon technology has been very relevant in photodetection as well. it enables designing large or very large-scale integration devices, in particular microchips and pixelled detectors like the Silicon Photo Multiplier made of micrometric channels grouped in mm(2) pixels. However, on the horizon, the recent development of nanotechnologies is opening a new direction in the design of sub-micron photodevices, owing to the capability to deal with individual molecules of compounds or to chemically grow various kinds of materials. Among them, carbon compounds appear to be the most promising materials being chemically very similar to silicon, abundant and easy to handle. In particular, carbon nanotubes (CNT) are a very intriguing new form of material, whose properties are being studied worldwide providing important results. The photoelectric effects observed on carbon nanotubes indicate the possibility to build photodetectors based on CNTs inducing many people to claim that we are at the beginning of a Post Silicon Era or of the Carbon Era. In this paper, we report on the most important achievements obtained on the application of nanotechnologies to photodetection and medical imaging, as well as to the development of radiation detectors for astro-particle physics experiments.

In a recent experiment performed in Naples by using the TTT-3 tandem accelerator, the 19F(p, α0) reaction has been investigated at low bombarding energies, Ep = 0.6–1 MeV. Excitation functions and angular distributions have been obtained by using several solid state detectors preceded by thin aluminium absorbers. By analysing angular distributions in terms of Legendre and cosine polynomials, a few spectroscopic ambiguities concerning the excited states of the compound nucleus, 20Ne, in the excitation energy region E* = 13.4–13.8 MeV, have been solved. Moreover, this reaction plays an important role for the description of the fluorine nucleosynthesis. For this reason, the astrophysical S-factor has also been extracted and the results have been compared with the literature data.

We report some recent experimental results on the spectroscopy of 13C and 20Ne nuclei by means of low energy nuclear reactions carried out with high resolution electrostatic accelerators. In the case of 13C we investigated the possible existence of a-cluster states above the a emission threshold by means of low energy elastic resonant scattering α+9Be in direct kinematics. Excitation functions show the presence of various resonances that have been reproduced by R-matrix fit. We studied also the structure of 20Ne by means of the 19F(p,α0) reaction at sub-barrier energies. The spectroscopy of 20Ne excited states in the region Ex 13.5-14.0 MeV can be probed by analyzing experimental angular distributions and excitation functions. This reaction plays an important role also in the CNOF cycle and is an important ingredient to describe hydrogen-induced destruction of fluorine in massive stars. For this reason we investigated the trend of S-factor, that has been compared with results previously reported in the literature. © Published under licence by IOP Publishing Ltd

We invented (2007) the VSiPMT, a novel, high-gain, photo detector device and we publically proposed this idea in an International Conference for the first time at the 11th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08) in Siena, triggering deep discussions on the feasibility of the device itself and on the convenience of such a solution. After several years spent in designing, evaluation, tests and eventually negotiations with some suppliers, we finally got a couple of prototypes of the Vacuum Silicon Photo Multiplier Tube (VSiPMT) made under our specifications by Hamamatsu. We present in this paper the most important results of characterization tests of the first prototypes of the VSiPMT. © 2014 IOP Publishing Ltd and Sissa Medialab srl.

VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a modern hybrid, high gain, silicon based photodetector based on the combination of a SiPM with a hemispherical vacuum glass PMT standard envelope. In such a device photoelectrons emitted by the photocathode are accelerated and focused by an electric field towards a small focal area covered by the SiPM which therefore acts as an amplifier, thus substituting the classical dynode chain of a PMT. With a view to the realization of a first prototype of VSiPMT our group is carrying out a preliminary work aimed at the study of SiPM performances as an electron detector, including an accurate Geant4-based simulation of the interaction between SiPM and electron beams. In order to perform a full characterization of the SiPM we developed an experimental setup for the extraction and the acceleration of a beam of backward secondary electrons emitted after the bombardment of a carbon foil by a proton beam extracted in a TTT-3 accelerator. © 2012 Elsevier B.V. All rights reserved.

The 3 MV tandem accelerator of the Naples University is used for research activities and applications in many fields. At the beginning of operation (1977) the main utilization was in the field of nuclear physics. Later, the realization of new beam lines allowed the development of applied activities as radiocarbon dating, ion beam analysis, biophysics, ion implantation etc. At present, the availability of different ion sources and many improvements on the accelerator allow to run experiments in a wide range of subjects. An overview of the characteristics and major activities of the laboratory is presented.

The Vacuum Silicon PhotoMultiplier Tube (VSiPMT) is an innovative design we propose for a modern hybrid photodetector based on the combination of a Silicon PhotoMultiplier (SiPM) with a hemispherical vacuum glass PMT standard envelope. The basic idea is to replace the classical dynode chain of a PMT with a SiPM, which acts as an electron multiplying detector. Such a solution will match the goal of a large photocathode sensitive area with the performances of a SiPM. This will lead to many advantages such as lower power consumption, mild sensitivity to magnetic fields and high quantum efficiency. The feasibility of this idea has been throughly studied both from a theoretical and experimental point of view. As a first step we performed the full characterization of a special non-windowed Hamamatsu MPPC with a laser source. The response of the SiPM to an electron beam was studied as a function of the energy and of the incident angle by means of a Geant4-based simulation. In this paper we present the preliminary results of the characterization of the SiPM with an electron source and we discuss how the development of next generation SiPMs will overcome the main weaknesses of VSiPMT, such as relatively low PDE and high photocathode voltage.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

The investigation of the 19F(p, α0) reaction at low bombarding energies allows the study of the spectroscopy of the 20Ne compound nucleus in an energy region where the existence of quartet excitations has been suggested in the literature. Moreover, this reaction plays a major role in the fourth branch of the CNO cycle since it is relevant for the correct description of the hydrogen burning of fluorine in stars. For these reasons, we decided to investigate the 19F(p, α0) reaction in the Ep ≃ 0.6-1 MeV energy range. The analysis of angular distributions and excitation functions allows one to improve the 20Ne spectroscopy in an excitation energy region where some ambiguities concerning Jπ assignments exist in the literature. In particular, the present data suggest a Jπ = 0 + assignment to the Ex = 13.642 MeV resonance. For this state, both partial and reduced widths for the α0 channel have been deduced. The trend of the astrophysical factor has been obtained from the integrated cross section. A comparison of the present results with data reported in the literature is also discussed.

A new direct measurement of the absolute cross section of the 1H(7Be,γ)8B reaction has been performed in inverse kinematics at Ecm = 990 keV. A radioactive 7Be beam (Elab, = 8 MeV) and a windowless H2 gas target were used; 8B recoils were identified and counted by a recoil mass separator. The reaction cross section was derived by normalization to the elastic scattering cross section, measured in a separate run. The resulting value σr = 0.40 ± 0.12 μb yielded an astrophysical S-factor at zero energy So = 15.3 ± 4.5 eV b, in fair agreement with recommended values. © 2001 Elsevier Science B.V. All rights reserved.

The D(He-3,p)He-4 cross section has been measured at E = 4.2 to 13.8 keV using the LUNA accelerator facility installed in the Gran Sasso National Laboratory (LNGS). The experimental setup and the interpretation of results in terms of electron screening potential are described. In the same experiment an estimate of the observed stopping power of the He-3 ions in D-2 target has been obtained and it turned out to be in good agreement with the standard compilation.

CdTe crystals grown by the Traveling Heater Method (THM) often show a pronounced non-uniformity along the ingots due to the thermal irregularities, the Te-excess growth conditions resulting from the retrograde slope of the solidus line of the phase diagram, and to the introduced impurities. In addition, structural defects can be present that affect the electrical and optical properties of the crystals. © 2011 IEEE.

X- and Gamma-Ray spectroscopy measurements have been performed on differently prepared CdTe samples (as-grown or annealed, different surface treatments, etc.) with Pt electrodes deposited by electroless technique in order to extract the typical figures of merit of the material and the detectors. Moreover, Rutherford Backscattering Spectrometry (RBS) using 8 MeV $^{7}{\hbox {Li}}^{+++}$ ions and X-Ray Fluorescence (XRF) using a Pd-anode X-Ray generator were performed to characterize the crystal surface as well as the semiconductor-electrode interface. The thickness, the stoichiometry and the concentration profiles of platinum, cadmium and tellurium present at the surface layers were determined. The distribution of Cd deficiency at the interface layers was profiled using simulations and showed complex profiles in the samples, that can greatly affect the electrical quality of the detectors. In addition, resistivity and mu-tau product mapping and electrical measurements have been performed for material characterization. The aim of this work is to understand and improve the structure of the material-electrode interface; in particular, to understand the effect of the annealing process on the fabrication of the contacts and, at the end, on the performances of the detectors. For this reason a large number of detectors have been produced applying various chemical surface treatments on as-grown and annealed material, in order to determine the best routine way to fabricate high-quality X- and Gamma-ray detectors to be used both as large size planar detectors and as elements of imaging systems in medical or industrial applications.

The energy loss of deuterons in 3He gas was measured at E d = 15 to 100 keV using the 3He pressure dependence of the 3He(d,p)4He cross-section at a given incident energy. At the highest energies, the observed energy loss is in good agreement with a standard compilation. However, with decreasing energy the experimental values drop steadily below the theoretical values and near E d = 18 keV they drop sharply (within 1 keV) reaching the domain of nuclear stopping power. This threshold behavior is due to the minimum 1s → 2s electron excitation of the He target atoms, i.e. it is a quantum effect. Some consequences are discussed.

A distributed system based on intelligent substations and a central MacIntosh II console has been designed to perform automatic monitoring and control of the HVEC TTT-3 tandem of our University. Each substation is a crate containing a G-64 bus, a 6809 CPU and several specific interfaces connected to various accelerator devices (e.g.: vacuum meters, valve-, quartz- and Faraday cup actuators, magnet supplies and related field meters, etc.). Communications between peripheral stations and central console are supported by a low-cost optical link. All interfaces are commercial ones, except a few designed for the purpose, particularly an ADC board which performs in hardware a conversion of the digitized data in absolute values according to a previously stored table. Modular software has been developed to obtain user-friendly system interaction, taking advantage of the graphic interface of the MacIntosh.

The stopping power of atomic and molecular deuterons in 3 He gas was measured over the range Ed = 10 to 100 keV using the 3 He pressure dependence of the 3 He(d,p) 4 He reactionyield. At en ergies above 30 keV, the observed stopping power values are in good agreement with a standard compilation. However, near 18 keV the experimental values drop by a factor 50 below the extrapolated values of the compilation. In a simple model, the behavior is due to the minimum 1s → 2s electronexcitationof the He target atoms (= 19.8 eV, corresponding to Ed = 18.2 keV), i.e. it is a quantum effect, by which the atoms become nearly transparent for the ions.

The performance of semi-insulating GaAs detectors, grown with the LEC technique, has been studied by irradiating the Schottky diodes with 2 and 2.4 MeV monoenergetic protons in a pencil beam with sub-millimeter width (70 or 600 μm). The beam was moved across the surface of the front (Schottky) contact, in order to investigate the uniformity of the detection characteristics over the sensitive area of the diodes, and to study the electric field behavior around the Schottky contact. For each scanning position, a pulse-height spectrum was measured. Then, the charge collected and the energy resolution were obtained as a function of the irradiation position both on the contact and outside it. The data show that • the best spectroscopic response occurs for the beam with 70 μm width, • when the beam is incident onto the contact, the energy resolution is between 1% and 5%, and the variation of the charge collected, for different irradiation position, is less than 30%, • when the beam is incident onto the border of the contact (substrate is irradiated), the spectrum is degraded and no clear peak is present, • collection of charge still occurs at distances up to about 500 μm from the border of the Schottky contact (for a pixel size of 200 μm), or up to about 200 μm (for a pixel diameter of 3 mm), • saturation of the curve collected charge vs. reverse bias voltage occurs at about 100 V for both 2 MeV (range=32 μm) and 2.4 MeV protons (range=41 μm).

A data transfer problem using FERA modules was found in a heavy ion nuclear physics experiment. The source of the problem was spotted in the handling of some signals on the FERA control bus. A modification of this handling is proposed and performed by means of a new CAMAC-FERA control module, the EBOFERA. Furthermore, this module has a number of useful features like the master gate and clear signals handling, event tagging, pattern unit and event counter.

Nuclear fusion reactions play a key role in the understanding of energy production, neutrino emission and nucleosynthesis of the elements in stars. The direct measurement of the cross section of these reactions at the relevant energies is usually hampered by cosmic radiation, beam induced background and/or the radioactivity of the nuclei involved. The measurements are expected to be completed by fall 1996.