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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Studies of uniformity of 50 μ m low-gain avalanche detectors at the Fermilab test beam

In this study, we report measurements of the uniformity of time resolution, signal amplitude, and charged particle detection efficiency across the sensor surface of low-gain avalanche detectors (LGAD). Comparisons of the performance of sensors with different doping concentrations and different active thicknesses are presented, as well as their temperature dependence and radiation tolerance up to 6 x 10 14 n/cm 2 . Results were obtained at the Fermilab test beam facility using 120 GeV proton beams, and a high precision pixel tracking detector. LGAD sensors manufactured by the Centro Nacional de Microelectrónica (CNM) and Hamamatsu Photonics (HPK) were studied. The uniformity of the sensor response in pulse height before irradiation was found to have a 2% spread. The signal detection efficiency and timing resolution in the sensitive areas before irradiation were found to be 100% and 30–40 ps, respectively. A “no-response” area between pads was measured to be about 130 μm for CNM and 170μm for HPK sensors. After a neutron fluence of 6 x 10 14 n/cm 2 the CNM sensor exhibits a large gain variation of up to a factor of 2.5 when comparing metalized and non-metalized sensor areas. An irradiated CNM sensor achieved a time resolution of 30 ps for the metalized area and 40 ps for the non-metalized area, while a HPK sensor irradiated to the same fluence achieved a 30 ps time resolution.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Operation of the prospective beamline calorimeter in the high-radiation forward environment of the international linear collider

Results on electromagnetically-induced radiation damage to silicon diode sensors, obtained from the T506 experiment at SLAC, are used in concert with detailed shower simulations to project the effects of radiation damage on the proposed International Linear Collider Beamline Calorimeter (BeamCal) detector system. The study makes use of the FLUKA Monte Carlo to simulate electromagnetic showers in both the T506 apparatus and the prospective BeamCal detector system. Under the conservative assumption that damage leading to sensor leakage currents is dominated by the neutron component of the electromagnetic shower, and assuming that resulting leakage currents depend linearly on neutron fluence, the power consumption required to operate the BeamCal detector at a temperature of -10° C would be expected to increase by approximately 100 W per year of operation. Lowering the operating temperature to -30° C would be expected to reduce the growth in power consumption to approximately 10 W per year. Under other assumptions about the source of damage, the accumulated power draw would be expected to be significantly less. Results on fluences of both electromagnetic and hadronic particles in regions peripheral to the bulk of the BeamCal detector system, where front-end electronics would be mounted, are also presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

A simulation model of front-end electronics for high-precision timing measurements with low-gain avalanche detectors

Here, we report simulation results of a study aiming to optimize parameters of a detector that uses low-gain avalanche detectors (LGAD) for high-precision timing measurements. The detector is assumed to be composed of a 50μm LGAD sensor coupled to front-end readout electronics which is used to measure the time of arrival of minimum ionizing particles. The simulation includes modeling of signal fluctuations in the LGAD sensor, variations of the analog bandwidth and signal-to-noise ratio (SNR) of the front-end electronics, time bin quantization, and radiation damage of the LGAD sensors. Two approaches to measure the timestamp are considered: leading edge and constant fraction. Simulated LGAD pulses before irradiation, and after irradiation with neutron fluences of 5×10 14 n/cm 2 and 1×10 15 n/cm 2 , are studied. The time resolution for a 50μm LGADs was found to be 35 ps for front-end electronics bandwidths larger than 350 MHz and SNRs larger than 30. The time resolution at SNR of 30 for fluences of 5×10 14 n/cm 2 and 1×10 15 n/cm 2 were found to be 31 ps and 37 ps, respectively.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Radiation campaign of HPK prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)

In this work, we report on the results of a radiation campaign with neutrons and protons of Low Gain Avalanche Detectors (LGAD) produced by Hamamatsu (HPK) as prototypes for the High-Granularity Timing Detector (HGTD) in ATLAS. Sensors with an active thickness of were irradiated in steps of roughly 2 up to a fluence of 3. As a function of the fluence, the collected charge and time resolution of the irradiated sensors will be reported for operation at °C.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Effects of trapped charge on the signal formation and detection efficiency for subsequent pulses in irradiated silicon sensors

Envisaged high energy physics experiments like the Future Circular Collider require unprecedented radiation hardness of the detectors, as well as short readout time due to high luminosity and occupancy. Silicon has proven to be extremely radiation hard. Sufficient signals can be recorded even at fluences close to 1 ∙ 1 0 16 n e q / cm 2 . Here, the signal formation was studied in silicon strip sensors, irradiated and annealed until the phenomenon of charge multiplication occurred. ATLAS12EC R0 mini sensors were tested by means of edge TCT measurements at temperatures around –20 °C. It was observed that the detection of subsequent signals separated up to several microseconds is altered by the charge trapped during the preceding pulses. The effects of trapped charge on the electrical configuration of a sensor are well known as a polarization or pumping effect in larger band-gap materials like diamond, but is often neglected for silicon at this relatively high temperature. The investigation of the effect created by trapped charges in silicon sensors using subsequent pulses allows to gain information on important parameters such as de-trapping times. Furthermore, it shows a severe impact on the sensor performance in a pile-up scenario. The irradiation fluence and hence the effective doping concentration, the temperature and the amount of initially created charge have a large impact on this phenomenon. The measurements presented help to characterize this phenomenon; particular attention was paid to the application point of view.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Charge collection study with the ATLAS ITk prototype silicon strip sensors ATLAS17LS

The inner tracker of the ATLAS detector is scheduled to be replaced by a completely new silicon-based inner tracker (ITk) for the Phase-II of the CERN LHC (HL-LHC). The silicon strip detector covers the volume 40 < R < 100 cm in the radial and | z | < 300 cm in the longitudinal directions. The silicon sensors for the detector will be fabricated using the n + -on-p 6-inch wafer technology, for a total of 22,000 wafers. Here, intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics (HPK). The charge collection properties were examined using penetrating 90 Sr β -rays and the ALIBAVA fast readout system for the miniature sensors of 1 cm × 1 cm in area. The samples were irradiated by protons in the 27 MeV Birmingham Cyclotron, the 70 MeV CYRIC at Tohoku University, and the 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor for fluence values up to 2 × 10 15 n eq /cm 2 . The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for the ITk. Sensors with two active thicknesses, 300 μ m (standard) and 240 μ m (thin), were compared and the difference in the charge collection was observed to be small for bias voltages up to 500 V. Some samples were also irradiated with gamma radiation up to 2 MGy, and the full depletion voltage was found to decrease with the dose. This was caused by the Compton electrons due to the 60 Co gamma radiation. To summarize, the design of the ATLAS17LS and technology for its fabrication have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors already delivered in January of 2020.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Performance of neutron and proton irradiated AC-LGAD sensors

Characterization of strip and pixel AC-LGAD devices with both laser TCT and probe station (IV/CV) will be shown on AC-LGADs irradiated with 1 MeV reactor neutrons at JSI/Ljubljana and with 400 MeV protons at FNAL ITA to fluences from 1e13~$n_{eq}/cm^2$ to a few times 1e15~$n_{eq}/cm^2$. This study was conducted within the scope of the ePIC detector time of flight (TOF) layer R&D program at the EIC, which will feature AC-LGADs with strip and pixel geometry. Sensors in the TOF layer will receive up to 1e13 $n_{eq}/cm^2$ fluence over the lifetime of the experiment.

AC-LGAD strips↗
DOE OSTI2017

Microstructural, mechanical and optical properties research of a carbon ion-irradiated Y 2 SiO 5 crystal

Ion irradiation has been a popular method to modify properties of different kinds of materials. Ion-irradiated crystals have been studied for years, but the effects on microstructure and optical properties during irradiation process are still controversial. In this study, we used 6 MeV C ions with a fluence of 1 × 10 15 ion/cm 2 irradiated Y 2 SiO 5 (YSO) crystal at room temperature, and discussed the influence of C ion irradiation on the microstructure, mechanical and optical properties of YSO crystal by Rutherford backscattering/channeling analyzes (RBS/C), X-ray diffraction patterns (XRD), Raman, nano-indentation test, transmission and absorption spectroscopy, the prism coupling and the end-facet coupling experiments. We also used the secondary ion mass spectrometry (SIMS) to analyze the elements distribution along sputtering depth. Finally, 6 MeV C ions with a fluence of 1 × 10 15 ion/cm 2 irradiated caused the deformation of YSO structure and also influenced the spectral properties and lattice vibrations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Modeling charge collection efficiency degradation in partially depleted GaAs photodiodes using the 1- and 2-carrier Hecht equations

Here, the Hecht equation can be used to model the nonlinear degradation of charge collection efficiency (CCE) in response to radiation-induced displacement damage in both fully and partially depleted GaAs photodiodes. CCE degradation is measured for laser-generated photocurrent as a function of fluence and bias in Al 0.3 Ga 0.7 As/GaAs/Al 0.25 Ga 0.75 As p-i-n photodiodes which have been irradiated with 12 MeV C and 7.5 MeV Si ions. CCE is observed to degrade more rapidly with fluence in partially depleted photodiodes than in fully depleted photodiodes. When the intrinsic GaAs layer is fully depleted, the 2-carrier Hecht equation describes CCE degradation as photogenerated electrons and holes recombine at defect sites created by radiation damage in the depletion region. If the GaAs layer is partially depleted, CCE degradation is more appropriately modeled as the sum of the 2-carrier Hecht equation applied to electrons and holes generated within the depletion region and the 1-carrier Hecht equation applied to minority carriers that diffuse from the field-free (non-depleted) region into the depletion region. Enhanced CCE degradation is attributed to holes that recombine within the field-free region of the partially depleted intrinsic GaAs layer before they can diffuse into the depletion region.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Excitation functions for (p,x) reactions of niobium in the energy range of E p = 40–90 MeV

In this paper, a stack of thin Nb foils was irradiated with the 100 MeV proton beam at Los Alamos National Laboratory’s Isotope Production Facility, to investigate the 93 Nb(p,4n) 90 Mo nuclear reaction as a monitor for intermediate energy proton experiments and to benchmark state-of-the-art reaction model codes. A set of 38 measured cross sections for nat Nb(p,x) and nat Cu(p,x) reactions between 40–90 MeV, as well as 5 independent measurements of isomer branching ratios, are reported. These are useful in medical and basic science radionuclide productions at intermediate energies. The nat Cu(p,x) 56 Co, nat Cu(p,x) 62 Zn, and nat Cu(p,x) 65 Zn reactions were used to determine proton fluence, and all activities were quantified using HPGe spectrometry. Variance minimization techniques were employed to reduce systematic uncertainties in proton energy and fluence, improving the reliability of these measurements. The measured cross sections are shown to be in excellent agreement with literature values, and have been measured with improved precision compared with previous measurements. This work also reports the first measurement of the nat Nb(p,x) 82m Rb reaction, and of the independent cross sections for nat Cu(p,x) 52g Mn and nat Nb(p,x) 85g Y in the 40–90 MeV region. The effects of nat Si(p,x) 22,24 Na contamination, arising from silicone adhesive in the Kapton tape used to encapsulate the aluminum monitor foils, is also discussed as a cautionary note to future stacked-target cross section measurements. Finally, a priori predictions of the reaction modeling codes CoH, EMPIRE, and TALYS are compared with experimentally measured values and used to explore the differences between codes for the nat Nb(p,x) and nat Cu(p,x) reactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Hexagonal boron nitride (h-BN) irradiated with 140 MeV protons

Here, hexagonal boron nitride was irradiated with 140 MeV protons to a fluence of ~6 10 20 p/cm 2 at T irr ~200 °C. Isotropic graphite was also irradiated alongside h-BN under similar conditions and fluence to enable direct comparison of the two similar structures. The effects of proton irradiation on dimensional stability and microstructure were studied using precision dilatometry and energy dispersive Xray diffraction techniques revealing by direct comparison to graphite that h-BN can better resist radiation damage from bombardment when irradiated with protons impinging normal to the crystallographic planes or along the crystallographic c-axis. X-ray diffraction experiments also revealed a preferred orientation of the crystallites in bulk samples near the sample surface, an orientation influenced by irradiation. Thermal studies using differential scanning calorimetry and thermogravimetric analysis to 740 °C, augmented by precision dilatometry, provided evidence of subtle phase transitions attributed to residual w-BN in the matrix. Irradiation appears to induce shifting of such transitions.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Bias-dependent displacement damage effects in a silicon avalanche photodiode

Radiation effects studies on a commercial beveled-edge avalanche photodiode (APD) showed that applying reverse bias to the device during irradiation enhanced the severity of apparent damage. Proton microbeam irradiations were made using a proton beam energy of 2 MeV and fluence ranging from 2.0 × 10 10 to 5.1 × 10 12 cm -2 . Charge collection measurements using the ion beam induced charge (IBIC) technique showed that relative losses increased by up to an order of magnitude when the reverse bias applied during irradiation increased from 50 to 1500 V. The presence of reverse bias also led to equivalent losses in charge collection that would only be seen in irradiations with an order of magnitude higher fluence in unbiased APDs. The results demonstrate that bias-enhanced irradiation damage is insufficiently understood and must be accounted for in characterizations of radiation effects.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Charge collection efficiency of diamond and silicon sensors irradiated with alpha particles

To evaluate the viability of using semiconductors as sensor materials in a detector for the Associated Particle Imaging technique, the radiation hardness of silicon and diamond diodes to alpha particles has been assessed. Here, the detector lifetimes for both silicon and diamond sensors were measured under the prolonged exposure to alpha particles emitted by an 241 Am source. The silicon detector was exposed to alpha radiation for approximately two months, reaching an accumulated fluence of ~ 1.5 x 10 12 α cm –2 . Additionally, by using a high purity single-crystal diamond with coplanar electrodes operating with full charge collection, the diamond detector response was measured over approximately ten months reaching an accumulated fluence of over 6 x 10 12 α cm –2 cm.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Deuterium retention and blistering in tungsten foils

To investigate deuterium retention and the onset of blistering, deuterium was implanted in cold rolled tungsten foils at fluences ranging from 3x1020 to 3x1022 D/m2. Ion energies were 300 eV and 2000 eV in order to be below and above the tungsten theoretical damage energy threshold. While there were energy dependent phenomena, blistering occurs regardless of ion energy. Both plastically and elastically deformed blisters were observed, as manifest in before and after micrographs. The fraction of plastically deformed blisters did not saturate at the fluences used in these studies. However, the size of the largest blister that relaxes during TDS does saturate at ~7 µm. A simple conceptual model is presented that identifies that deuterium released from elastically deformed blisters appears at ~600 K in the thermal desorption spectra, which is consistent with large vacancy clusters.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

The microstructure and He + ion irradiation behavior of novel low-activation W-Ta-Cr-V refractory high entropy alloy for nuclear applications

Microstructure and nanohardness of a nearly equimolar W-Ta-Cr-V high entropy alloy (HEA), as well as its irradiation response under He + irradiation, were investigated. The single-phase body-centered cubic nanostructured alloy with a 1 µm thick layer was fabricated on a silicon substrate using a magnetron sputtering method. The HEA film has a complex microstructure consisting of micrometric domains that exhibit internal nanostructure controlled by their crystal orientation. The measured nanohardness of the W-Ta-Cr-V alloy is 13 ± 2 GPa, which significantly exceeds the hardness of nanocrystalline tungsten as a result of the high solid-solution strengthening effect. In order to evaluate the irradiation resistance of the HEA film, the material was irradiated with 200 keV He + ions at room temperature, with two different ion fluences: 1 × 10 16 and 5 × 10 16 ions/cm 2 . Using transmission electron microscopy, a high density of extremely fine He bubbles is observed that were uniformly distributed in the matrix. The increase of He + ion fluence increased the density of bubbles, whereas their size remained at a similar level, which indicates that the damage proceeds by the nucleation of additional He bubbles, not by their growth.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Cr plasma-material-interaction in PISCES-RF: D thermal release, retention, and erosion

Pure chromium (Cr) targets were exposed to high-flux deuterium (D) plasmas in the Pisces-RF linear plasma device, and measurements of D retention, release, and erosion were subsequently performed. Post-exposure D retention was quantified using temperature-programmed desorption on Cr targets irradiated by 50 eV ions over a broad range of exposure temperatures (423–873 K) and ion fluences (3 × 10 24 – 3 × 10 26 m −2 ). The retained D inventory was observed to decrease rapidly with increased exposure temperature, from approximately ∼7 × 10 20 m −2 at ∼ 420 K, to then saturate near ∼ 10 20 m −2 for exposure temperatures above ∼550 K. Separately, at fixed exposure temperature (∼450 K), D retention was found to have only a weak dependence on increasing ion fluence. Lastly, the erosion of Cr in D plasma was investigated for ion impact energies in the range 40 ≤ E i ≤ 250 eV. Erosion was inferred using optical emission spectroscopy (OES) from the ratio of emission lines (Cr I (425.4 nm)/D I (656.1 nm)) measured close to the target. Conversion of the OES yield data to net erosion yield was made with singular ion energy target mass-loss measurements. These net erosion yield data were then further corrected to obtain gross erosion yield by accounting for a re-deposition factor, computed using a simple model. The gross erosion yield is found to be 2–4 times lower than predicted by SDTrimSP, consistent with that typically observed for light-ion sputtering under high-flux plasma conditions.

Chromium↗
DOE OSTI2026

Retention and surface morphology evaluation of fine-grain dispersion-strengthened tungsten for plasma-facing component applications

This study exposed novel fine-grain dispersion-strengthened tungsten (W) to high fluence, low energy deuterium (D) and helium (He) plasmas to evaluate how material microstructure and composition affect hydrogen retention and surface morphology. Tested materials included fine-grain dispersion-strengthened tungsten (DSW) with 3 wt% zirconium carbide (ZrC) dispersoids, fine-grain dense W without any dispersoids (FGW), and coarse-grained polycrystalline ‘ITER-grade’ W. Samples were exposed to D 2 + and He + plasmas at fusion-relevant fluences (∼10 25 m -2 ) and ion energies (75 eV) over a range of temperatures (200 °C, 300 °C, 450 °C for D, 850 °C for He). Helium ion microscopy was performed on the exposed samples to evaluate surface morphology changes and material integrity. After D plasma exposure, the ZrC dispersoids showed near-surface degradation at exposure temperatures above 300 °C, but no detrimental morphology changes were observed for the adjacent W grains. After He plasma-exposure, nano-structured fuzz formation was observed in the tungsten matrix of all samples. The ZrC dispersoids maintained their integrity despite the surrounding fuzz growth, with clear delineation between the W fuzz and dispersoid regions. Thermal desorption spectroscopy showed that ZrC DSW consistently retained more D than the FGW by about a factor of 2 across all temperatures. At 200 °C and 300 °C, the ITER-W displayed lower D retention than both the DSW and FGW, however at 450 °C ITER-W showed the highest retention, about 50% more than DSW. He retention was comparable across all samples, with the highest retention observed in the fine-grain W, only 26% higher than in ITER-W. These insights on retention behavior will inform further optimization of these novel fine-grained tungsten materials with and without dispersoid additives.

Dispersion-strengthened tungsten↗
DOE OSTI2017

The AGR-3/4 fission product transport irradiation experiment

AGR-3/4 was the combined third and fourth planned irradiations for the U.S. Department of Energy Advanced Gas Reactor (AGR) Fuel Development and Qualification Program. The primary purpose of the AGR program is to support the development and qualification of tristructural isotropic (TRISO) coated particle fuel for use in High Temperature Gas-cooled Reactors. AGR-3/4 was designed as a fission product transport irradiation experiment whose specific objectives were to: (1) irradiate fuel containing UCO (uranium oxycarbide) designed-to-fail (DTF) fuel particles that provide a fixed source of fission products for subsequent transport through compact matrix and structural graphite materials, (2) assess the effects of sweep gas impurities on fuel performance and fission product transport, (3) provide irradiated fuel and material samples for post-irradiation examination and post-irradiation heating, and (4) support the refinement of fuel performance and fission product transport models. The AGR-3/4 test train was irradiated in the northeast flux trap of the Advanced Test Reactor at Idaho National Laboratory for 369.1 effective full power days from December 2011 to April 2014. The experiment was successful in achieving its specification goals in terms of burnup and fast fluence levels reached at the end of irradiation and fuel temperature levels maintained throughout irradiation: peak compact burnup reached 15.27% fissions per initial heavy-metal atom and peak compact fast fluence reached 5.32 × 10 25 n/m 2 (E > 0.18 MeV), while the time-average volume-average temperatures of the compacts ranged from 854 to 1345°C. Fission product release to birth ratios reached values in the 10 -4 - 10 -3 range early during irradiation as the DTF particles started to fail. In conclusion, subsequent post-irradiation examination will provide information on fission product distributions in matrix and core graphite materials, enabling refinement of fission product transport models.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗