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We have studied the effects of proton irradiation on the AlGaN/GaN HEMTs with AlN buffer layer as well as conventional GaN buffer layer. It was found that a short time proton irradiation (~ 50 sec) can promote beneficial effects on device performances, which results in great reduction in the off-state leakage current and the gate leakage current without degrading the output current and transconductance. The pulsed I-V measurement demonstrated that both devices exhibit greatly improved current dispersion characteristics and, particularly, the device with AlN buffer layer shows stronger radiation hardness than that of the device with GaN buffer layer. These interesting results are believed to be due to the hydrogen passivation with thermal annealing effect during the proton irradiation. It is expected that the proper irradiation condition such as fluence, energy, and time is crucial to improve the device performances, rather than to deteriorate the performances.

This study examines thermal responses of skin to pulsed millimeter wave (mm-wave) and radiofrequency (RF) radiation. We review limits for pulse fluence in the IEEE Std. C95.1-2019 and the 2020 guideline of the International Commission on Nonionizing Radiation Protection (ICNIRP), as well as the recently re-affirmed guidelines of the U.S. Federal Communications Commission (FCC). The focus of the study is on millimeter-wave frequencies (30-300 GHz) where energy is absorbed close to the body surface and intense pulses could potentially cause high temperature gradients at the skin, but the model is extended to lower frequencies as well. The study employs a simple one-dimensional baseline thermal model for skin and Pennes' bioheat equation (BHTE), together with a baseline model for thermal damage to skin based on a standard model. The predicted temperature increases produced by 3-sec pulses at 94 GHz are consistent with previous experimental results with no adjustable parameters in the model. The few reported data on thermal damage to the skin from pulsed 94 GHz energy are insufficient to enable a conventional analysis of damage thresholds and the data may be affected by errors in dosimetry. The baseline model suggests that the implicit limits on pulse fluence in the present FCC guidelines might allow, in extreme (but in practice unrealistic) cases, transient increases in skin temperature that approach thresholds for thermal pain but which remain well below levels anticipated to cause thermal damage. Limits on pulse fluence in the current IEEE and ICNIRP exposure guidelines would preclude such effects. Such extreme pulses are far above those that are emitted by wireless and other technologies but may be emitted by some nonlethal weapons systems. FCC's proposed “device-based time averaging” rules will restrict thermal transients in skin from mm-wave transmitters to levels that are roughly an order of magnitude below the slower temperature increases produced by the low-frequency components of the modulation waveform and appear to be excessively conservative. An appendix discusses the applicability of two approximations to the analytical solutions to the bioheat equation that can be used to estimate temperature increases in skin from exposure to mm-waves.

The impulse generated by ablating aluminum targets was investigated in this study using the micro-impulse measurement method with a torsion pendulum, and the plasma plume characteristics were researched using fast photography and optical emission spectroscopy. The experiment was carried out with a pulsed laser with a wavelength of 1064 nm and a pulse duration of 8.7 ns. The fluence varied from 5.69 J/cm2 to 33.67 J/cm2. The impulse coupling coefficients were obtained from the impulse measurements and the images of the plasma plume were recorded with a gate width of 500 ns. The results indicated that the variation of the impulse coupling coefficient was affected by the change of the laser fluence and the decline of the coefficient at high fluence was because of the plasma shielding effect. The intense radiation region located above the target surface in the corresponding plume was evident. Additionally, the differential coupling coefficient was presented and compared with the impulse coupling coefficient. The plasma temperature and the electron number density were estimated with the Boltzmann plot method and the Stark broadening method, respectively, using optical emission spectroscopy. Furthermore, the relative energy coupling efficiency was deduced from the plume front positions to determine the influence of the plume expansion dynamics on the impulse coupling. The obtained results showed that the variation trend of efficiency versus the laser fluence was similar to that of the impulse coupling coefficient.

A simple deuterium DC glow discharge was employed to study the production of densely packed deuterium clusters with high binding energies in palladium. The incident ions create damage cascades leading to the production of defects such as vacancies, dislocations, and voids. These defects trap interstitial deuterons with binding energies dependent on the trap’s geometry and volume. 1 Varying fluences of incident ions were used (1E18 ions/cm 2 , 1E19 ions/cm 2 , and 1E20 ions/cm 2 ) and incident energies dependent on cathode bias (-0.75 kV, -0.875 kV, and -1.0 kV). Thermal Desorption Spectroscopy (TDS) was used to estimate the clusters’ trapping energies. 2 There appeared to be a deuterium trapping limit dependent on defect concentration where once a distinct defect density was met any further damage was counterproductive in deuterium trapping. The condition that produced the most trapped deuterium was -0.75 kV in 1 Torr deuterium with a fluence of 1E18 ions/cm 2 . Some samples were observed under SEM and TEM. The results showed surface pit and blister formations which grew in concentration as the fluence increased. Beneath the surface formations, cross-section images showed large voids and holes in the material with cracks at grain boundaries. TEM images displayed the resulting damage structure which extended ~250 nm into the cathode for a sample at 1.0 Torr and -1.0 kV. A proposal is that as the damage concentration increased, these voids grew to such an extent that they formed the blisters and eventually ruptured.

High fluence K-shell and L-shell x-ray sources are desired for various high energy density physics experiments. One efficient method for creating such a source is the laser heating of materials that are underdense to laser light. Nano-wire foams are an ideal choice for an underdense material and have average densities of 6-15 mg/cm 3 . The manufacture of robust Cu, Ag and Au nano-wire foams into millimeter scale targets is possible through a technique of freeze casting an aqueous suspension of nano-wires. Cylindrical targets with sizes between 2 to 4 mm have been shot on both the NIF and the Omega laser facilities. For example, x-ray conversion efficiencies (XRCE) from silver nano-wire foams have been measured to be ~1.0% when heated with ~400 TW of 3w laser light in a 2.5 ns square pulse from the NIF laser system. The XRCE from foam targets have been found to be ~2 times that observed in metal lined cylindrical cavity targets and ~5 times that observed in prepulsed metal foils. Experimental results and comparisons with simulations will be presented.

The structural evolution of laser-excited systems of gold has previously been measured through ultrafast MeV electron diffraction. 1 - 3 However, there has been a long-standing inability of atomistic simulations to provide a consistent picture of the melt process, concluding in large discrepancies between the predicted threshold energy density for complete melt, as well as the transition between heterogeneous and homogeneous melting. 1 We make use of two-temperature classical molecular dynamics simulations utilizing two highly successful interatomic potentials and reproduce electron diffraction data presented by Mo et al.. We recreate the experimental electron diffraction data employing both a constant and temperature-dependent electron-ion equilibration rate. In all cases we are able to match time-resolved electron diffraction data, and find consistency between atomistic simulations and experiments, only by allowing laser energy to be transported away from the interaction region for the duration of the melt process. This additional energy-loss pathway, which scales strongly with laser fluence, we attribute to hot electrons leaving the target during melt before refluxing.

Photo acoustic microscopy (PAM) achieves high contrast, intravital imaging of the microvasculature by utilizing the specificity of endogenous optical absorption. PAM has been further augmented by using loss of correlation (LoC) methods to image blood flow. However, estimating blood flow using LoC methods necessitates dense spatial sampling which increases laser fluence. To address concerns over the increase in laser fluence, we develop a sparse modeling algorithm to reconstruct blood flow in PAM from downsampled data. The proposed method is superior to reconstruction by bicubic interpolation, exhibiting an error of 5.6 ± 3.4% in vivo compared to 33.4 ± 32.7% for bicubic interpolation, for data downsampled eight times.

An iterative fluence compensation and spectral unmixing algorithm for spectroscopic photoacoustic imaging (SPA) is described. The algorithm focuses on solving the optical inverse problem. It employs optical prior knowledge of tissues, leverages a Monte Carlo simulator for fluence estimation, and assumes a linear mixed model for absorption, scattering, and anisotropy. After an initial guess of the tissue composition, the algorithm sequentially estimates the light fluence, solves for tissue concentrations in spectral unmixing, and updates the optical parameters iteratively until the estimated initial pressure converges to the measurement. The algorithm was validated in simulation, where ground truth data was synthesized from an in vivo study of prostate cancer on mice model. Performance of the algorithm and the scenario without fluence compensation was compared, and the convergence and the precision of the algorithm are reported.

We experimentally measure percent-level optical-to-multi-cycle terahertz conversion efficiencies by injecting a home-made wavelength- and duration-tunable two-line laser into periodically poled lithium niobate. We study the efficiency vs. the input laser peak fluence, pulse duration, crystal length and poling period at cryogenic temperature. Our work is a significant step towards high energy terahertz pulses for linear electron acceleration.

THz stealth and shielding devices with low reflection and strong absorption are promising in terahertz (THz) communication and radar. In this study, active THz reflection and absorption properties based on strong correlated electron oxides VO x (x= 1.5, 2) thin films are investigated. By varying the laser fluence, the reflection can be modulated to near 0 and the absorption can be tuned to near 70%. Our work suggest strong correlated electron oxide films could provide a possible approach for the design of tunable THz stealth and shielding devices.

In this work, we use optical pump-terahertz (THz) probe spectroscopy to investigated the impurity-induced topological phase transition and the photo-induced carrier behavior in cadmium arsenide (Cd3As2), a three-dimensional Dirac semimetal. By comparing the dynamics of different temperature and pump fluence, we discuss the carrier dynamics and physical mechanism caused by impurity.

We demonstrate an optical switch based on gold implanted germanium (Ge:Au) suitable for cavity dumping of a free-electron laser (FEL). We achieve a switching contrast of more than 50 % in a broad range of FEL wavelengths from 6 to 90 µm. A linear relationship between the switching fluence and the frequency of the FEL optical field supported by our simulation highlights the role of a photoinduced finite sub-µm thickness of the reflecting plasma layer. The plasma switch exhibits negligible absorption of the FEL radiation in the ʻoffʼ state and requires only a moderate thermoelectric cooling at incident FEL power of several Watts.

Neutron induced single event failure mechanism in commercial SiC Schottky diode was researched with Single-Event Burnout(SEBO) radiation test equipment and precise fluence correlation and correction system. To evaluate and quantify the diode immunity to terrestrial neutron, we derived 50% fail fluence, the slope of the fail rate versus the fluence of each device and voltage acceleration factor. Moreover, physical analysis was conducted on SiC to verify the result of SEBO.

This work evaluates the degradation mechanisms of the proton irradiated HEMTs incorporating graded AlGaN layers that support 3DEG for the conduction and 3DHG as a back barrier and subsequently evaluating it for dosimeter applications. The results presented demonstrate the deleterious effects of the proton fluence on the device's transfer characteristics in creating a bottleneck towards the flow of carriers in the 3DEG sheet. However, the trench gate arrangement with HfO 2 insulator controlling the bottleneck for the device operation remains intact even at a high proton fluence.

A novel nanosecond (ns) laser anneal (multiple laser shots at sub-melting low laser energy) was employed to reduce the blanket sheet resistance of Ru thin films deposited by physical vapor deposition (PVD). The laser anneal was conducted after PVD Ru deposition and then followed up with a standard 400°C anneal in a forming gas environment. Blanket sheet R decreased by 30% for the laser + furnace annealed Ru films, whereas the drop for just 400°C furnace annealed Ru films was only 18%. Multiple laser exposures at an optimized laser fluence was identified as a key factor in enabling this benefit at BEOL compatible thermal budget suitable for scaled-down Ru interconnects.

Non-linear interactions between light and matter are crucial for widespread applications in physical sciences, life science and engineering. Second harmonic generation (SHG) and sum-frequency generation spectroscopy in the near infrared and optical range have enabled intriguing insights into surface properties and how they influence for instance chemical reactions [1] . Expansion of these methods by developing non-linear X-ray spectroscopies has recently added the capability of studying surfaces [2] , symmetry-breaking [3] and buried interfaces [4] with elemental specificity. However, widespread application is currently limited by access to free-electron laser facilities. Here we report the first generation of second harmonic emission in the extreme ultraviolet (XUV-SHG) at the titanium M-edge. The experiments were carried out with a high-harmonic seeded SXRL [5] bringing nonlinear XUV spectroscopy with atomic specificity to the table-top. The SXRL pulses with an energy of (14 ± 2) nJ, a pulse duration of (1.73 ± 0.13) ps, wavelength of 32.8 nm and a Gaussian-like beam profile is focused down with a gold ellipsoidal mirror down to an elliptical spot with a size of roughly 20 µ m x 40 µ m. The estimated intensity on target is about of (1.0 ± 0.1)•10 10 W/cm 2 . In the focus we exceeded the damage threshold fluence of 2 mJ/cm 2 and observed single-shot damage of 50 nm Ti foils. At these intensities we also generate second harmonic light at 75.6 eV. The fundamental and SHG beams are refocused with a toroidal mirror, spectrally separated by a grating and imaged on a cooled CCD camera.

Due to numerous unique properties, such as the capability of resonantly exciting crystal lattice vibrations, molecular rotations and other low energy transitions in solids, liquids and gases, terahertz radiation belongs to one of the most interesting but yet less explored spectral regions. Recently, a considerable progress has been demonstrated in THz generation by optical rectification (OR) in organic crystals, conventionally driven by near-IR fs-pulses centred at the telecommunication wavelength of 1.5 µm. Although high optical- to THz conversion efficiencies of 1-3% with pulse energies of up to 0.9 mJ [1] can be achieved, the conversion efficiency is nevertheless deteriorated by multiphoton absorption and is fundamentally limited by the damage threshold of the crystal. This restricts the applicable pump fluence to nothing more than 20 mJ/cm 2 .

There is a strong interest in mid-infrared (mid-IR) Semiconductor Saturable Absorber Mirrors (SESAMs) [1] . We have established an accurate nonlinear reflectivity and time-resolved SESAM characterization which covers a wavelength range from 1.9 µm to 3 µm transferring our near-IR knowhow [2] , [3] to the mid-IR ( Fig. 1a , 1b ). The nonlinear reflectivity of a SESAM is characterized by the saturation fluence, modulation depth, non-saturable losses and a rollover parameter. The temporal response determined with the pump-probe (PP) setup is described by a fast and slow recovery time. We present the nonlinear reflectivity and PP characterization with three different SESAMs designed and grown at ETH Zurich within FIRST clean room facility. The low-finesse antiresonant SESAMs contain either 2, 3 or 4 In 0.26 Ga 0.74 Sb quantum wells (QWs), operating at a wavelength of 2.05 µm (see absorption dip in Fig. 1c ).

Experimental studies on the fundamentals of laser ablation often rely on characterizing ablated morphologies at irradiated spots as first clues to the processes involved. For example, the regression of the squared diameter of ablated spots as a function of the pulse energy is a well-known and often-used method to measure the laser-induced damage threshold of materials [1] . However, there is a significant amount of information lost during the conversion of two-dimensional data to a single representative value, for example, in the above case, the diameter. Were more of the original information utilized, more accurate and complete data on the laser ablation phenomena could be retrieved from each irreversible ablation trial. Such high-throughput and reliable measurement methods are particularly important when aiming for big-data enabled analysis, such as deep-learning approaches.

A Semiconductor Saturable Absorber Mirror (SESAM) is a key optical component used extensively for passively modelocking of diode-pumped solid-state and semiconductor disk lasers. Modulation depth (ΔR), saturation fluence (F sat ), non-saturable losses (ΔR ns ) and recovery times are the key parameters of a SESAM, which depend on semiconductor layer design and growth parameters. It has been shown that the recovery dynamics of InGaSb-based mid-infrared (mid-IR) SESAMs are less effected from low-temperature growth of the absorber layer and strain unlike InGaAs-based near-infrared SESAMs [1] . Here we demonstrate type-I InGaSb/GaSb quantum well (QW) based SESAMs operating well above 2 µm with full nonlinear reflectivity and pump-probe characterizations for the first time.

A passively-Q-switched Yb:Lu1-x-yYxLayVO4 laser based on a two-dimension (2D) molybdenum ditelluride (MoTe2) saturable absorber (SA) is reported for the first time to the best of our knowledge. High quality few layered 2D MoTe2 nanosheets were fabricated by liquid phase exfoliation (LPE) method and used as the SA, whose saturable absorption properties around 1.0 μm were characterized with a saturation fluence of 3.02 μJ/cm2 and a modulation depth of 8.3%. In the passively Q-switched laser operation, the shortest pulse width of 500 ns was obtained with an average output power of 0.33 W at a pulse repetition rate of 117 kHz, corresponding to the maximum single pulse energy of 2.8 μJ and the peak power of 5.6 W.

Piezoelectric actuators are candidates for use in radioactive environments but specific radiation tests are necessary to understand the radiation effects on the whole actuator assembly. The results of three irradiation tests on a piezoelectric actuator used for Crystal Collimation are presented. The total ionising dose effects are studied with two Gamma (60Co) Tests up to 10 MGy and 1 MGy, whereas the displacement damage effects are studied in a Proton Test up to 2 MGy and 1.14 × 1016 p/cm2 fluence. The main results are summarised for each test, presenting a maximum impedance increase of less than 25% (Proton Test), a maximum free stroke reduction of less than 25% (Proton Test) and a variation in the shape of the hysteresis response of the actuator.

The whole 3D simulation of SGEMP from X-ray to electromagnetic field environment is realized by developing 3D PIC code with compiling MC function modules in it, so that photoelectrons of arbitrary energy, angular, spatial and time distributions which calculated by transport code JMCT could be transformed into the initial current source used in PIC simulation directly. The simulation results are analyzed preliminarily. It is obtained that the emitted current is 0.11 A while the electric field could get 100 kV/m and magnetic field is over 1.6×10−6 T when the blackbody X-ray of temperature 1 keV and emitted fluence 1 J/cm2 perpendicularly irradiates the side of cylindrical object with material of Al and height of 2.0 cm, radius of 1.0 cm.

We demonstrate efficient multicycle THz generation with periodically poled lithium niobate crystals via difference frequency generation using a multiple-line source. The THz yield for different crystal lengths as well as pump pulse durations is investigated. Our experimental results show excellent agreement with the theoretical predictions. By employing a 20-mm PPLN crystal, up to 2.7 μJ at 0.5 THz was obtained with 6.2 mJ input pump pulse energy (130 m.J/cm2 peak fluence) at 77 K, corresponding to an internal conversion efficiency of 0.3%. The record internal efficiency at the peak fluence of 130 m.l/cm? shows the great potential for high-energy multicycle THz generation with a multiple-line source.

Silicon surface modifications induced by single femtosecond laser pulses at minimally disruptive fluences near melting threshold in air and water are investigated using atomic-force microscopy. At threshold fluence the modified surface in air is presented by chaotically-located nanobumps and nanopits, while in water they appear to be circumferentially-spaced. Phenomena of cracking, corrugated surface and eruption of material are also observed.

An ultrafast pulsed laser processing for materials can obtain submicometer- to nanometer-sized parts or patterns because the heat cannot diffuse in time during the ultrafast pulsed duration and the multiphoton absorption leads to a threshold of ablation. An ultra-fast pulsed laser is first absorbed due to optical penetration. Therefore, the direct optical penetration or coulomb explosion leads to the initial optical ablation during ultrafast pulsed duration without thermal diffusion. After the direct optical ablation and sequent thermal diffusion, the thermal ablation occurs for the residual heat of an ultrafast pulsed laser maintaining the material temperature above the evaporated temperature. This study uses Laplace transform method to show the effects of optical ablation and thermal ablation, respectively. The results reveal that both optical and thermal ablations follow Beer's exponential law as experimental observations in the published papers. The optical ablation triggered by the only energy source of directly incident ultrafast pulsed laser governs the main ablation depth, and then thermal ablation induced by the residual heat after the optical ablation gives the enhancement of the ablation depth. The optical ablation is preferred for obtaining the better processing quality of an ultrafast pulsed laser due to no thermal damage of thermal diffusion-induced ablation. The ablated depth per pulse versus laser fluence predicted by this work agrees with that measured by the published paper. This study will provide the closed-form solution to elucidate direct optical ablation and sequent thermal ablation for the ultra-fast pulsed laser photo-thermal processing.

Proton-induced SEE results are reported for the ADC12D1620. Output clock SEU cross sections were measured over a range of proton energies. No SEFI events were observed at 250 MeV to a fluence of 2.0×1011 p/cm2.

High voltage terminals are enclosed with RTV560 silicone rubber. Space travelling wave tubes are exposed in irradiation environment. As one organic elastomer, silicone rubber is degraded by the radiation. In the paper, effect of electron irradiation on properties of RTV560 silicone rubber was investigation. The used electrons have an energy range 10~100 keV, and the irradiation fluence ranges from 1.0×106 rad to 1.0×107 rad. At last, roughness, hardness, DTA and TGA were measured and analyzed for all samples.

Photoacoustic tomography (PAT) is a non-invasive, high-resolution imaging modality capable of providing functional and molecular information about various pathologies, such as cancer. In PAT imaging, the depth dependent light attenuation limits the fluence as a function of depth and thereby reduces the PA amplitude of signals from deeper regions of tissue. This makes it impossible to equally compare signals from various depths and causes inaccuracies when measuring spectroscopic-based measurands such as oxygen saturation levels. Previous fluence compensations studies used a homogeneous assumption for optical properties of the phantom or compensated relatively small objects. In this work, we propose an algorithm in which PAT images are compensated for the speed-of-sound (SOS) and optical heterogeneities. Keywords—Photoacoustics, ultrasound, fluence compensation, image reconstruction.

Using low-k oxide silica based dielectrics is the usual approach to diminish signal interconnections in VLSI CMOS ICs. To decrease this effect in SOI ICs, a high resistivity silicon substrate with a trap-rich (HR-TR) layer is used. We study the properties of standard SOI wafers both with high-k or silica BOX and substrate layers after the high fluence CO+ implantation for using them instead of HR-TR SOI wafers.

Photo-modulated reflectance measurements provide a powerful, non-contact, non-destructive and inline-compatible method with low-cost operation for statistical process control of ion implantation steps on monitor and on product wafers. We present case studies describing how photo-modulated reflectivity measurements (PMR) can be used for ion implantation dose, fluence and tilt angle monitoring with excellent resolution, even for low-energy ion implantation processes. This is important because precise dopant and damage profile control is crucial in state-of-the art semiconductor processes utilizing shallow junctions and complex 3D doping profiles.

We investigate the effect of pressure and gas species on the electrical transport in nanosheets of palladium diselenide (PdSe2) and molybdenum disulfide (MOS2), used as the channel of back-gate field-effect transistors. Air pressure can control the carrier polarity in PdSe2 devices and the dominant n-type conduction in a high vacuum can reversibly transform in p-type transport at atmospheric pressure. Structural defects facilitate gas adsorption, which widens the hysteresis of the transfer characteristics. For Mos2 the hysteresis has a monotonic dependence on gas adsorption energy. We investigate the effect of low-energy electron irradiation and find that few tens e−/nm2 fluence can significantly change the transistor characteristics. Finally, the field emission currents from both PdSe2 and Mos2 nanoflakes are measured. The first experimental observation of the gate modulation of the field emission current from a Mos2 monolayer is reported. Such a finding constitutes the proof-of-concept of a field-effect transistor based on field emission and paves the way for new applications of 2D materials in vacuum electronics.

Focal laser ablation offers a minimally invasive method of treating solid organ tumors via hyperthermia. Real-time monitoring of the induced tissue damage is critical for clinical success, and is typically accomplished using thermal measurements and Arrhenius models. In this manuscript, the utility of interstitial fluence probes in assessing coagulation directly in real-time was assessed through a Monte Carlo simulation and an experimental study in tissue mimicking prostate phantoms. In the simulation results, fluence increases greater than 100% were observed inside the coagulation zone, as coagulation effectively acts as a 'light trap'. Moreover, the passing of the coagulation boundary at any given point was shown to correspond with an inflection in fluence with a mean absolute difference of 0.1mm and 0.4mm observed for the simulation and phantom respectively. These results suggest that interstitial fluence probes may be capable of providing real-time feedback during focal laser ablation.

The impact of high energy proton radiation, as would be encountered in highly eccentric and Europa orbits, on ultra-thin GaAs solar cells was studied. The cells were irradiated with 68 MeV protons at fluences of 2 × 1012 cm−2 and 1 × 1013cm−2. Cathodoluminescence and dark I-V were used to evaluate the variation of defect density and J 02 with fluence, respectively. The applicability of cathodoluminescence to the study of radiation damage in photovoltaic devices is discussed.

Radiation-hard semiconductor devices are becoming more important for a growing number of nuclear and space applications. Gallium Nitride (GaN) semiconductor devices can be highly beneficial in this regard. In this paper, we report the electrical performance of multiple AlGaN/GaN deep UV LEDs irradiated by high fluence fast neutrons. The irradiation experiment was conducted in a newly enhanced beamline at the Los Alamos Neutron Science Center (LANSCE) from 2014-2016 with a maximum fluence of 2.41x1013 neutrons/cm2 over a 3-year span, in an temperature varying, semi-open outdoor housing. We continuously monitored the I-V characteristics of all GaN devices, and showed that they maintained proper I-V behaviors as the neutron fluence increased. Extensive data analysis further shows that effects of neutron irradiation fluence increment in a given day are actually smaller than that induced by daily temperature variation. Our experimental results facilitate the design of diagnostics systems such as multi-pixel imagers for high energy density physics experiments, and complex space electronics that must survive through both high fluence radiation and large orbital temperature variations.

Directed Energy System (DES) is highly efficient to damage both static and dynamic targets. Each target demands a minimum lethal fluence to make engagement successful, depending on the material, thickness, coating and structural properties. DES provides the required lethal fluence on the target to reach the melting or burning temperature. The static target consumes approximately constant fluence, but for the dynamic target, the flux density requirement estimation varies within the dwell time, which is proportional to the distance between the DES and the target. In this paper, the initial power requirement of DES has been estimated based on target specification.

The change in the current-voltage characteristics (CVC) of silicon n-JFETs and p-JFETs when exposed to gamma rays 60Co and electrons with the energy of 6 MeV is considered. The obtained approximations of the dependences of the pinch-off voltage and drain current on the fluence of fast electrons are presented.

This paper reports a novel technique to perform photoacoustic spectroscopy using low-energy fluence, toward development of non-invasive glucose monitor. The fluence with lower energy can make the system simple and compact, although it generates weak photoacoustic wave. To detect the weak photoacoustic wave, we improve the propagation efficiency adopting an acoustic wave forming technique that generates a phase-aligned and low-frequency acoustic wave. This technique was both verified by analysis and experiment with deionized water by using wavelengths in the near-infrared region to change the absorbance. The excitation light was as weak as 50 mW. The center frequency of the photoacoustic wave ranged from 0.2 to 0.9 MHz. The resolution of optical absorption was 2×10-4/mm, which is equivalent to the resolution to measure physiological glucose levels. This technique has high potential for a noninvasive monitoring of glucose and other components in interstitial fluid.

The effort to characterise detector sensors and components for the High Luminosity upgrade of the CERN Large Hadron Collider requires collaboration between irradiation facilities around the world. By convention, the radiation damage following irradiation with particle beams is reported as the 1 MeV neutron equivalent fluence, obtained using the corresponding hardness factor. Measurements of proton hardness factors at three different kinetic energies are presented, by characterisation of commercially available diodes before and after irradiation, using irradiations at the University of Birmingham, the Karlsruhe Institute of Technology, and CERN. Possible future improvements to these measurements are also discussed.

This study was done to evaluate whether the irradiation of dentine with ultrashort laser pulses prior to adhesive procedures contributes to increase the adhesive resistance to microtraction essays. Twenty-four human teeth (third molars) were used, divided into 4 groups (n=6): standard adhesive procedures with etch-rinse adhesive were used in the control group, and in the experimental groups, the dentin was irradiated by 25 fs pulses prior to the adhesive procedures, with varying fluences. One tooth from each group was used to evaluate its surface roughness. After 24h, the teeth were sectioned with perpendicular cuts, producing toothpicks that were submitted to the microtraction test. The results showed that the groups irradiated with fluences under 4 J/cm² presented similar results among themselves, comparable to the control group, while the group irradiated with 8 J/cm² showed lower adhesive strength. We propose that the adhesive strength and surface roughness reduction resulting from the fluence increase is probably related to the shielding arising from an electron plasma formation during the ablation, decreasing the material removal efficiency. Nevertheless, the lower energy densities did not affect the adhesiveness, maintaining values similar to the control.

We report in this work the SEL hardness assurance test (HAT) for the XCR4C ASIC, which is a rad-hard fullfunction four-channel correlated double sampling (CDS) ASIC targeting the readout of X-ray CCDs for applications in the fields of X-ray spectroscopy, imaging and timing observations. The ASIC is implemented in a novel differential switchedcapacitor architecture, which makes it high linear, low power, immune to commom-mode noise and interferences as well as easy configurable. Some SEL-oriented rad-hard strategies are adopted to combat the harsh low-earth-orbit (LEO) space environment, among which we describe in detail the pesudo double guard ring (PDGR) layout technique and the process hardness method. The XCR4C ASIC was fabricated with AMS 0.35 µm 2P4M bulk CMOS process with an epitaxial layer and occupies a chip area of 3.47×1.84 mm2. The HAT was carried out at the Heavy Ion Research Facility in Lanzhou (HIRFL), where the ASIC was irradiated by 181Ta31+ ions with a linear energy transfer (LET) in silicon up to 81.35 MeV-cm2/mg. The results showed that till to a total fluence as high as 1.68×107 ions/cm2, not a single latchup was monitored, and the performance degradations after irradiation were negligible.

The radiation hardness of a fully depleted Pinned Photodiode (PPD) CMOS image sensor (CIS) has been evaluated with gamma and proton irradiations. The sensors employ an additional n-type implant in pixel which allows full depletion to be achieved by reversing biasing the substrate, and have been irradiated alongside reference devices in which the implant has been omitted. Event analysis under X-ray illumination has been used to study the charge collection and charge diffusion in the sensors. The results show no obvious charge collection degradation at 10 MeV equivalent proton fluence of up to 10 11 p/cm2. Moreover, it has been shown that charge diffusion is largely suppressed in the fully depleted sensors. After exposure to a total dose of 100 krad(Si), both the fully depleted and the reference sensors show high sense node leakage current. This is believed to be due to an exposed edge of the shallow trench insulation (STI) oxide near the sense node. Dark signal distribution shows that hot pixels are dominant for both sensors after proton irradiation. An activation energy of ~0.62 eV derived from the temperature-dependent dark current result suggests that irradiation induced bulk defects is the main dark current source.

Nano-antennas on silica or semiconductor substrate cannot handle high power due to their low thermal conductivity. This paper shows that high thermal conductivity substrates such as diamond can handle 20 times higher fluence than silica substrate based nano-antenna without affecting their electrical field enhancement capacities.

The competing interplay of photo-thermal and photo-doping effect of VO 2 nanofilm under fs laser excitation was studied at terahertz frequency. We find that with photo-thermal effect generated by fs laser pulses, both the character time constant of insulator-to-metal phase transition and the pump fluence threshold of transition were decreased, while the amplitudes of the two photo-response are competing.

Leakage current degradation of SiC junction barrier Schottky diodes were studied under heavy ion microbeam. Leakage current increased linearly with fluence and was positively related to bias voltage. It was proposed that leakage current occurred as a result of the accumulation of multiple leakage paths. The explanation that the increased leakage current was related to leakage paths formed by damage in the mechanism of "micro-SEB" was verified.

In this study, the degradation effects of inverted metamorphic four-junction (IMM4J) solar cells were investigated after 1 MeV electron irradiation using spectral response and electrical property measurements. The results show that, similar to traditional tri-junction (TJ) GaInP/GaAs/Ge solar cells, the electrical properties (such as I sc , V oc , and P max ) degrade as a function of logφ, where φ represents the electron fluence. In particular, the degradation of V oc is more serious than that of I sc because of the sum rule for V oc and the limit rule for I sc in IMM4J cells. Analysis of the spectral response curves indicates that, unlike traditional TJ cells, the In 0.3 Ga 0.7 As (1.0 eV) sub-cell exhibits the most severe damage in the irradiated IMM4J cells and the In 0.58 Ga 0.42 As sub-cell becomes a limits part for the electrical properties of the IMM4J solar cells.

This work will show the results of neutron interactions on 4 JANSR (100kRad) bipolar junction transistors (BJTs). The tests were carried out as per MIL STD 750, Method 1017. The total integral neutron fluence was stepped at 5 levels between 5. $0\mathrm{x}10^{11}\mathrm{n}/\mathrm{c}\mathrm{m}^{2}$ and $1.0\mathrm{x}10^{14} \mathrm{n}/\mathrm{c}\mathrm{m}^{2}$. The effects of this neutron bombardment are consistent with those of displacement damage. The primary effects were $\mathrm{h}_{F\mathrm{E}}$ degredation combined with increasing ICES and ICBO over increasing fluence. Secondary effects include a rise in VCESAT and a slight rise in BVCEO. While not specifically tested, it is believed that dynamic parameters are impacted by $\mathrm{h}_{F\mathrm{E}}$ reduction including the storage time in the BE junction in switching applications and BVcBo/BVcEO approaching unity. The end goal of this work is to offer an explanation of neutron irradiation that is useful in a switching power circuit design