The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength,λ=248nm; photon energy,EPh=5eV) is reported. The ND ...layers were deposited by means of a pulsed spray technique. Specifically, the active layer of each PC consisted of untreated (as-received) and hydrogenated ND particles, 250 nm in size, sprayed on ap-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at10−6mbarand compared to a Cu-based one, used as reference. All the photocathodes were irradiated at normal incidence. The quantum efficiency (QE) of the photocathodes was assessed. QE values of the ND-based photocathodes were higher than that of the reference one. In particular, the hydrogenated ND-based PC exhibited the highest QE due to the negative electron affinity that results from the surface terminated by hydrogen. Additionally, the photocathode surface/local temperature and the multiphoton process contribution to the electron emission were studied.
In this work we report a study on the influence of innovative pulsed stresses utilizing an UV laser and a homemade generator of magnetic field on radish seeds (Raphanus sativus L.) growth. We ...analysed the seed germination and seedling growth. The UV pulsed laser was an excimer KrF operating at 248 nm, 23 ns of pulse duration, with a laser fluence of about 40 mJ/cm2. The generator of pulsed magnetic field was realized by the electric discharge on a coil of a high voltage capacitor of 150 μF, 60 kV . The magnetic field pulse waveform exhibited damped oscillations at 215 kHz with a maximum intensity of 400 mT . Groups of uniform radish seeds were exposed to laser pulses at five different doses: 30000 shots (KrF/1), 80000 shots (KrF/2), 145000 shots (KrF/3), 225000 shots (KrF/4) and 275000 shots (KrF/5). Other groups were exposed to magnetic field at eight different doses: 3600 shots (MF/1), 7200 shots (MF/2), 10800 shots (MF/3), 14400 shots (MF/4), 18000 shots (MF/5), 21600 shots (MF/6), 32400 kshots (MF/7) and 36000 shots (MF/8). Simultaneously, untreated seeds were used as control. All treatments were performed at room temperature. Both untreated and treated seeds were transferred in Petri dishes and followed for their germination and seedling growth up to 96 h. The results showed that the stress induced by UV laser photons brought a significant stimulation on root growth which may contribute to improve the performance and the productivity of the plants. On the contrary, all physical stresses induced by magnetic fields did not have effect on seed germination, as well as on cell elongation growth and on hypocotyls in comparison to control seeds.
In this work, zebrafish (Danio rerio) embryos were subjected to different physical stresses, consisting of a static and two low frequency magnetic fields, and two radio frequencies. Specifically, ...embryos were exposed to static (Bo, 0 Hz), very low frequency (VLF, 0.2 Hz), low frequency (LF, 270 kHz), very high frequency (VHF, 100 MHz) and ultra-high frequency (UHF, 900 MHz) magnetic field irradiations for up to 5 days. The field intensities were 40 mT, 40 mT, 470 μT, 240 nT and 240 nT, respectively. Untreated embryos were used as control (n = 10 for each condition).
The Front Surface Acceleration (FSA) obtained in Laser Ion Source (LIS) systems is one of the most interesting methods to produce accelerated protons and ions. We implemented a LIS to study the ion ...acceleration mechanisms. In this device, the plasma is generated by a KrF excimer laser operating at 248 nm, focused on an aluminum target mounted inside a vacuum chamber. The laser energy was varied from 28 to 56 mJ/pulse and focused onto the target by a 15 cm focal lens forming a spot of 0.05 cm in diameter. A high impedance resistive probe was used to map the electric potential inside the chamber, near the target. In order to avoid the effect of plasma particles investing the probe, a PVC shield was realized. Particles inevitably streaked the shield but their influence on the probe was negligible. We detected the time resolved profiles of the electric potential moving the probe from 4.7 cm to 6.2 cm with respect to the main target axis, while the height of the shield from the surface normal on the target symmetry center was about 3 cm. The corresponding electric field can be very important to elucidate the phenomenon responsible of the accelerating field formation. The behavior of the field depends on the distance x as 1/x super(1.85) with 28 mJ laser energy, 1/x super(1.77) with 49 mJ and 1/x super(1.74) with 56 mJ. The dependence of the field changes slightly for our three cases, the power degree decreases at increasing laser energy. It is possible to hypothesize that the electric field strength stems from the contribution of an electrostatic and an induced field. Considering exclusively the induced field at the center of the created plasma, a strength of some tenth kV/m could be reached, which could deliver ions up to 1 keV of energy. These values were justified by measurement performed with an electrostatic barrier.
Abstract Hydrogenated amorphous silicon (a-Si:H) is a material with a very good radiation hardness and with the possibility of deposition on flexible substrates like Polyimide (PI). Exploiting these ...properties, the HASPIDE (Hydrogenated Amorphous Silicon PIxels DEtectors) project has the goal of developing a-Si:H detectors on flexible substrates for beam dosimetry and profile monitoring, neutron detection and space experiments. The detectors for this experiment will be developed in two different structures: the n-i-p diode structure, which has been used up to now for the construction of the planar a-Si:H detectors, and the recently developed charge selective contact structure. In the latter the doped layers (n or p) are replaced with charge selective materials namely electron-selective conductive metal-oxides (TiO 2 or Al:ZnO) and hole-selective conductive metal oxides (MoO x ). In this paper preliminary data on the capabilities of these detectors to measure X-ray and electron fluxes will be presented. In particular, the linearity, the sensitivity, the stability and dark current in various conditions will be discussed.
The surface of a detector grade CVD polycrystalline diamond sample (5×5×0.05mm3) was irradiated by an ArF excimer laser (λ=193nm, τ=20ns) to produce graphitic conductive layers.
In particular, two ...sets of four parallel graphitic strip-like contacts, with 1mm pitch, were created along the whole sample on the top and on the rear surfaces of the sample respectively. The two series of stripes lie normally to each other. Such a grid allows to obtain a segmented all-carbon device capable of giving bi-dimensional information on particle detection processes in nuclear applications.
Afterwards, an extensive characterization of the samples was performed: SEM and micro-Raman investigations to study the morphological and structural evolution of the irradiated areas, EDS measurements to individuate any absorption phenomena from environment associated to laser treatment, and nanoindentation mapping to understand how the hard-soft transformation occurred depending on the locally transferred energy. Finally, current-voltage analyses were carried out checking the ohmic behavior of the diamond-graphite contact. By comparing the results of the different characterization analyses, a strong periodicity of the modified surface properties was found, confirming the reliability and reproducibility of the laser-induced graphitization process.
The results demonstrate that the laser-writing technique is a good and fast solution to produce graphitic contacts on diamond surface and therefore represents a promising way to fabricate segmented all-carbon devices.
Hardness and reduced elastic modulus mappings of a graphitic strip induced by laser on diamond surface. Display omitted
•The manufacturing of strip-like graphitic contacts on diamond surface by laser-writing was carried out.•The contacts were created on diamond surface of both sides, with orthogonal orientation, to obtain a segmented all-carbon device capable to give bi-dimensional information during detection processes.•SEM and micro-Raman Spectroscopy analyzes allowed understanding the physical evolution of the graphitization process, and how the morphological and structural changes depend on laser processing.•Phenomena of chemical modifications were found by EDS: oxidation reactions were present on all the irradiated areas, with increasing intensity values for the most damaged zones.•Nano-indentation investigations were performed showing that hard-soft transformation occurred depending on the locally deposited energy and in agreement with the changes of hybridization (sp3→sp2) of carbon atoms.•Current-voltage analyses allowed to verify the ohmic behavior of the contacts and to evaluate the resistivity values of every strip, which range from 2.5 × 10-5 Ωm up to 3 × 10-5 Ωm.
The DARTWARS project has the goal of developing high-performing innovative traveling wave parametric amplifiers with high gain, large bandwidth, high saturation power, and nearly quantum-limited ...noise. The target frequency region for its applications is 5–10 GHz, where the expected noise temperature is below 600 mK. The development follows two different approaches, one based on Josephson junctions and one based on kinetic inductance of superconductors. This contribution mainly focuses on the Josephson traveling wave parametric amplifier, presenting its design, preliminary measurements and the test of homogeneity of arrays of Josephson junctions.
Progress in the development of a KITWPA for the DARTWARS project Borghesi, M.; Barone, C.; Borghesi, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
February 2023, 2023-02-00, Letnik:
1047
Journal Article
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DARTWARS (Detector Array Readout with Traveling Wave AmplifieRS) is a three years project that aims to develop high-performing innovative Traveling Wave Parametric Amplifiers (TWPAs) for low ...temperature detectors and qubit readout (C-band). The practical development follows two different promising approaches, one based on the Josephson junctions (TWJPA) and the other one based on the kinetic inductance of a high-resistivity superconductor (KITWPA). This paper presents the advancements made by the DARTWARS collaboration to produce a first working prototype of a KITWPA.
Abstract
Hydrogenated Amorphous Silicon (a-Si:H) is a well known material for its intrinsic radiation hardness and is primarily utilized in solar cells as well as for particle detection and ...dosimetry. Planar p-i-n diode detectors are fabricated entirely by means of intrinsic and doped PECVD of a mixture of Silane (SiH
4
) and molecular hydrogen. In order to develop 3D detector geometries using a-Si:H, two options for the junction fabrication have been considered: ion implantation and charge selective contacts through atomic layer deposition. In order to test the functionality of the charge selective contact electrodes, planar detectors have been fabricated utilizing this technique. In this paper, we provide a general overview of the 3D fabrication project followed by the results of leakage current measurements and X-ray dosimetric tests performed on planar diodes containing charge selective contacts to investigate the feasibility of the charge selective contact methodology for integration with the proposed 3D detector architectures.
ABSTRACT—Left ventricular (LV) mass and geometry predict risk for cardiovascular events in hypertension. Regression of LV hypertrophy (LVH) may imply an important prognostic significance. The ...relation between changes in LV geometry during antihypertensive treatment and subsequent prognosis has not yet been determined. A total of 436 prospectively identified uncomplicated hypertensive subjects with a baseline and follow-up echocardiogram (last examination 72±38 months apart) were followed for an additional 42±16 months. Their family doctor gave antihypertensive treatment. After the last follow-up echocardiogram, a first cardiovascular event occurred in 71 patients. Persistence of LVH from baseline to follow-up was confirmed as an independent predictor of cardiovascular events. Cardiovascular morbidity and mortality were significantly greater in patients with concentric (relative wall thickness ≥0.44) than in those with eccentric geometry (relative wall thickness <0.44) in patients presenting with LVH (P =0.002) and in those without LVH (P =0.002) at the follow-up echocardiogram. The incidence of cardiovascular events progressively increased from the first to the third tertile of LV mass index at follow-up (partition values 91 and 117 g/m), but for a similar value of LV mass index it was significantly greater in those with concentric geometry (OR4.07; 95% CI1.49 to 11.14; P =0.004 in the second tertile; OR3.45; 95% CI1.62 to 7.32; P =0.001 in the third tertile; P <0.0001 in concentric versus eccentric geometry). Persistence or development of concentric geometry during follow-up may have additional prognostic significance in hypertensive patients with and without LVH.
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