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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Assessment of the Geomechanical Risks Associated with CO 2 Injection at the FutureGen 2.0 Site: Application of the State of Stress Assessment Tool (SOSAT)

This report presents the results of the application of the State of Stress Assessment Tool (SOSAT) on the FutureGen 2.0 data set. SOSAT was developed as part of the National Risk Assessment Partnership (NRAP) project and provides a unique integrated framework for estimating the state of stress probability distribution at a given depth in the subsurface and evaluating the risk of induced shear and tensile failure resulting from the injection of carbon dioxide (CO 2 ). The approach implemented by SOSAT is based on two deterministic and widely used methods of determining the state of stress (i.e., stress polygon and one-dimensional tectonic-elastic approach). These methods have been modified using a probabilistic approach to account for uncertainties in the input parameters. The methodology proposed in SOSAT was demonstrated using the data obtained for the FutureGen 2.0 project located in the Illinois Basin. Although the FutureGen 2.0 project was suspended by the U.S. Department of Energy prior to the start of injection operations, the extensive characterization efforts undertaken at the storage site have yielded a considerable amount of valuable data about this part of the sedimentary basin. The FutureGen 2.0 storage site was designed to accommodate the injection of 1.1 million metric tons of CO 2 per year over a 20-year period. The injection of CO 2 and the associated pressure buildup in the reservoir is expected to alter the state of stress over the course of the injection. These changes in the initial stress state may affect fault stability and potentially lead to the unintentional creation of hydraulic fractures, which could pose a leakage risk if not contained within the reservoir. Assessing these risks is critical to making informed decisions about the characterization, management of the injection operation, and monitoring of the storage site. The data required by SOSAT for the geomechanical assessment of the FutureGen 2.0 site were identified, and the methodology proposed in SOSAT was followed to evaluate the probability of reactivating critically oriented faults or potentially creating hydraulic fractures in the reservoir. The results of the geomechanical analysis performed using the SOSAT led to the following conclusions. 1. The probability distribution of the state of stress indicates significant uncertainties in the magnitude of the maximum horizontal stress S Hmax , while the minimum horizontal stress S hmin is well constrained by the stress measurements conducted during the characterization efforts at the storage site. This uncertainty in the magnitude of S Hmax is a common challenge and has significant implications for geomechanical risk at sites like FutureGen 2.0 where a strike-slip tectonic regime exists. 2. The probability that the Mount Simon reservoir was initially critically stressed is relatively high—25%. When the pore pressure increases to the maximum allowable pressure permitted under the Underground Injection Control Class VI regulation of the FutureGen 2.0 project, the risk of shear failure approaches a probability of 43%. These relatively high probabilities reflect the current state of information about the geomechanical conditions in this part of the Illinois Basin. For future operations in this basin this should be a high characterization priority because it could significantly lower the risk of operations. 3. Based on the maximum injection pressure allowed in the UIC Class VI, the risk of unintentional hydraulic fracturing is limited. The risk of shear failure as determined by SOSAT is based on a very conservative approach assuming that critically oriented faults exist in the subsurface. While no faults have been formally identified at the FutureGen 2.0 site, the results obtained with SOSAT using the FutureGen 2.0 data set highlight the importance of integrating uncertainties in critical parameters to quantify geomechanical risks in a defensible way. Should SOSAT have been available at the time the characterization activities were being planned, more characterization efforts would have been implemented to reduce the uncertainties on the magnitude of the maximum horizontal stress, and to dismiss with confidence the potential existence of a critically-oriented fault in the reservoir (e.g., 3D seismic survey).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

SECARB Report on Post-Injection In-Situ Monitoring

The Southeast Carbon Sequestration Partnership Phase III Anthropogenic Test at Citronelle Field is the United States’ largest prototype of commercial CO 2 capture from a coal-fired power station and transportation, injection, storage and monitoring. This report focuses on the results of the post-injection monitoring period for the Anthropogenic Test. Monitoring methods include both direct and indirect measurements. The Class V Experimental Permit requires extensive monitoring of injected CO 2 at the surface and at deep and shallow depths. The safety, integrity and information objectives of the CO 2 monitoring plan are in place to: (1) create and sustain wellbore integrity; (2) assure safe CO 2 injection operations; (3) verify the location and migration of the injected CO 2 plume; and (4) monitor for any CO 2 leakage. A robust suite of monitoring approaches is utilized for the in-situ monitoring and include, pressure monitoring, various seismic surveys, pulsed neutron logging, reservoir fluid sampling and injection surveys. Data and observations collected using these monitoring methods will be used in the numerical model to inform the post-injection site care monitoring plan. This report describes actions pertaining to in situ monitoring at the Anthropogenic Test Site that were undertaken during the period of September 2014 to May 2016. These monitoring techniques include the acquisition of pressure data, seismic data, pulsed neutron capture logs, reservoir fluid sampling, and tracer gas monitoring. CO 2 injection operations began on August 20, 2012 and terminated on September 1, 2014.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2015

Characterization of Reactivity Controlled Compression Ignition (RCCI) Using Premixed Gasoline and Direct-Injected Gasoline with a Cetane Improver on a Multi-Cylinder Engine

The focus of the present paper was to characterize Reactivity Controlled Compression Ignition (RCCI) using a single-fuel approach of gasoline and gasoline mixed with a commercially available cetane improver on a multi-cylinder engine. RCCI was achieved by port-injecting a certification grade 96 research octane gasoline and direct-injecting the same gasoline mixed with various levels of a cetane improver, 2-ethylhexyl nitrate (EHN). The EHN volume percentages investigated in the direct-injected fuel were 10, 5, and 2.5%. The combustion phasing controllability and emissions of the different fueling combinations were characterized at 2300 rpm and 4.2 bar brake mean effective pressure over a variety of parametric investigations including direct injection timing, premixed gasoline percentage, and intake temperature. Comparisons were made to gasoline/diesel RCCI operation on the same engine platform at nominally the same operating condition. The experiments were conducted on a modern four cylinder light-duty diesel engine that was modified with a port-fuel injection system while maintaining the stock direct injection fuel system. The pistons were modified for highly premixed operation and feature an open shallow bowl design. The results indicate that the authority to control the combustion phasing through the fuel delivery strategy (e.g., direct injection timing or premixed gasoline percentage) is not a strong function of the EHN concentration in the direct-injected fuel. It was also observed that NOx emissions are a strong function of the global EHN concentration in-cylinder and the combustion phasing. Finally, in general, NOx emissions are significantly elevated for gasoline/gasoline+EHN operation compared with gasoline/diesel RCCI operation at a given operating condition.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Climate response to off-equatorial stratospheric sulfur injections in three Earth system models – Part 1: Experimental protocols and surface changes

There is now substantial literature on climate model studies of equatorial or tropical stratospheric SO 2 injections that aim to counteract the surface warming produced by rising concentrations of greenhouse gases. Here we present the results from the first systematic intercomparison of climate responses in three Earth system models wherein the injection of SO 2 occurs at different latitudes in the lower stratosphere: CESM2-WACCM6, UKESM1.0 and GISS-E2.1-G. The first two use a modal aerosol microphysics scheme, while two versions of GISS-E2.1-G use a bulk aerosol (One-Moment Aerosol, OMA) and a two-moment (Multiconfiguration Aerosol TRacker of mIXing state, MATRIX) microphysics approach, respectively. Our aim in this work is to determine commonalities and differences between the climate model responses in terms of the distribution of the optically reflective sulfate aerosols produced from the oxidation of SO 2 and in terms of the surface response to the resulting reduction in solar radiation. A focus on understanding the contribution of characteristics of models transport alongside their microphysical and chemical schemes, and on evaluating the resulting stratospheric responses in different models, is given in the companion paper (Bednarz et al., 2023). The goal of this exercise is not to evaluate these single-point injection simulations as stand-alone proposed strategies to counteract global warming; instead we determine sources and areas of agreement and uncertainty in the simulated responses and, ultimately, the possibility of designing a comprehensive intervention strategy capable of managing multiple simultaneous climate goals through the combination of different injection locations. We find large disagreements between GISS-E2.1-G and the CESM2-WACCM6 and UKESM1.0 models regarding the magnitude of cooling per unit of aerosol optical depth (AOD) produced, which varies from 4.7 K per unit of AOD in CESM2-WACCM6 to 16.7 K in the GISS-E2.1-G version with two-moment aerosol microphysics. By normalizing the results with the global mean response in each of the models and thus assuming that the amount of SO 2 injected is a free parameter that can be managed independently, we highlight some commonalities in the overall distributions of the aerosols, in the inter-hemispheric surface temperature response and in shifts to the Intertropical Convergence Zone, as well as some areas of disagreement, such as the extent of the aerosol confinement in the equatorial region and the efficiency of the transport to polar latitudes. In conclusion, we demonstrate that it is possible to use these simulations to produce more comprehensive injection strategies in multiple climate models. However, large differences in the injection magnitudes can be expected, potentially increasing inter-model spreads in some stratospheric quantities (such as aerosol distribution) while reducing the spread in the surface response in terms of temperature and precipitation; furthermore, the selection of the injection locations may be dependent on the models' specific stratospheric transport.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Finding Balance Between Biological Groundwater Treatment and Treated Injection Water

At the U.S. Department of Energy’s Hanford Site, CH2M HILL Plateau Remediation Company operates the 200 West Pump and Treat which was engineered to treat radiological and chemical contaminants in groundwater as a result of the site’s former plutonium production years. Fluidized bed bioreactors (FBRs) are used to remove nitrate, metals, and volatile organic compounds. Increasing nitrate concentrations in the treatment plant effluent and the presence of a slimy biomass (a typical microorganism response to stress) in the FBRs triggered an investigation of nutrient levels in the system. Little, if any, micronutrient feed was coming into the bioreactors. Additionally, carbon substrate (used to promote biological growth) was passing through to the injection wells, causing biological fouling of the wells and reduced specific injectivity. Adjustments to the micronutrient feed improved microorganism health, but the micronutrients were being overfed (particularly manganese) plugging the injection wells further. Injection well rehabilitation to restore specific injectivity required repeated treatments to remove the biological fouling and precipitated metal oxides. A combination of sulfamic and citric acids worked well to dissolve metal oxides and sodium hypochlorite effectively removed the biological growth. Intensive surging and development techniques successfully removed clogging material from the injection wells. Ultimately, the investigation and nutrient adjustments took months to restore proper balance to the microbial system and over a year to stabilize injection well capacities. Carefully tracking and managing the FBRs and well performance monitoring are critical to balancing the needs of the treatment system while reducing fouling mechanisms in the injection wells.

Carlson, Mark A.↗
DOE OSTI2023

Can strong substorm-associated MeV electron injections be an important cause of large radiation belt enhancements?

It has become well-established that strong outer radiation belt enhancements are due to wave-driven electron energization by whistler-mode chorus waves. However, in this study, we examine strong MeV electron injections on 10 July 2019 and find substantial evidence that such injections may be a crucial contributor to outer radiation belt enhancement events. For such an examination, it is essential to precisely separate temporal flux changes from spatial variations observed as Van Allen Probes move along their orbits. Employing a new “hourly snapshot” analysis approach, we discover unprecedented details of electron flux evolutions that suggest that for this event, the outer belt enhancement was not continuous but instead intermittent, mostly composed of 4 large discrete injection-driven flux increases. The injections appear as sharp flux increases when observed near apogee. Otherwise, by comparing hourly snapshots for different times, we infer injections and infer temporally stable fluxes between injections, despite strong and continuous chorus emission. The fast and intermittent electron flux growth successively extending earthwards implies cumulative outer belt enhancement via a series of repetitive inward transport associated with injection-induced electric fields.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Investigating the Influence of the Initial Biomass Distribution and Injection Strategies on Biofilm-Mediated Calcite Precipitation in Porous Media

Attachment of bacteria in porous media is a complex mixture of processes resulting in the transfer and immobilization of suspended cells onto a solid surface within the porous medium. However, quantifying the rate of attachment is difficult due to the many simultaneous processes possibly involved in attachment, including straining, sorption, and sedimentation, and the difficulties in measuring metabolically active cells attached to porous media. Preliminary experiments confirmed the difficulty associated with measuring active Sporosarcina pasteurii cells attached to porous media. However, attachment is a key process in applications of biofilm-mediated reactions in the subsurface such as microbially induced calcite precipitation. Independent of the exact processes involved, attachment determines both the distribution and the initial amount of attached biomass and as such the initial reaction rate. As direct experimental investigations are difficult, this study is limited to a numerical investigation of the effect of various initial biomass distributions and initial amounts of attached biomass. This is performed for various injection strategies, changing the injection rate as well as alternating between continuous and pulsed injections. The results of this study indicate that, for the selected scenarios, both the initial amount and the distribution of attached biomass have minor influence on the Ca 2+ precipitation efficiency as well as the distribution of the precipitates compared to the influence of the injection strategy. The influence of the initial biomass distribution on the resulting final distribution of the precipitated calcite is limited, except for the continuous injection at intermediate injection rate. But even for this injection strategy, the Ca 2+ precipitation efficiency shows no significant dependence on the initial biomass distribution.

58 GEOSCIENCES↗
DOE OSTI2022

CO 2 zonal injection rate allocation and plume extent evaluation through wellbore temperature analysis

Temperature analysis during a pause in injection operations, known as warmback analysis, has been used in the petroleum industry for evaluating the injection conformance and estimating the location of the flooded front in applications, such as waterflooding oil reservoirs. Here in this work, methods are introduced to extend the application of temperature warmback analysis to estimate the zonal CO 2 injection rate and zonal CO 2 plume extent during geologic CO 2 storage in a saline aquifer. First, novel analytical solutions are developed to model transient temperature in the aquifer during the injection and subsequent shut-in periods considering two-phase flow (gaseous CO 2 and aqueous brine) conditions in the aquifer. The solution involves a discretization of the aquifer into regions; the energy and mass conservation equations for the regions are solved simultaneously considering appropriate boundary conditions at the interfaces. Two solutions techniques are presented: multi-region and three-region solutions. Inverse models are developed accordingly to evaluate the injection profile and estimate the extent of the plume front in the reservoir during the injection period. The multi-region solution results in an inversion approach that requires regression analysis. However, the three-region formulation results in a simple graphical technique for inverse modeling. The analytical solutions are validated against a thermally coupled reservoir simulation tool using different synthetic cases for CO 2 injection in deep saline aquifers. The results of the developed solutions provide a good match with numerical results during forward and inverse modeling.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

A comparison of implantation methods for large PIT tags or injectable acoustic transmitters in juvenile Chinook salmon

The miniaturization of acoustic transmitters may allow greater flexibility in terms of the size and species of fish available to tag. New downsized injectable acoustic tags similar in shape to passive integrated transponder tags can be rapidly injected rather than surgically implanted through a sutured incision, as is current practice. Before wide-scale field use of these injectable transmitters, standard protocols to ensure the most effective and least damaging methods of implantation must be developed. Three implantation methods were tested in various sizes of juvenile Chinook salmon Oncorhynchus tschawytscha. Methods included a needle bevel-down injection, a needle bevel-up injection with a 90-degree rotation, and tag implantation through an unsutured incision. Tagged fish were compared to untagged control groups. Weight and wound area were measured at tagging and every week for 3 weeks; holding tanks were checked daily for mortalities and tag losses. No differences among treatments were found in growth, tag loss, or survival, but wound area was significantly reduced among incision-treated fish. The bevel-up injection had the worst results in terms of tag loss and wound area and also had high mortality. Implantation through an incision resulted in the lowest tag loss but the highest mortality. Fish from the bevel-down treatment group had the least mortality; wound areas also were smaller than the bevel-up treatment group. Cumulatively, the data suggest that the unsutured incision and bevel-down injection methods were the most effective; the drawbacks of both methods are described in detail. However, we further recommend larger and longer studies to find more robust thresholds for tagging size that include more sensitive measures.

injection↗
DOE OSTI2012

Intensity Modulated Proton and Photon Therapy for Early Prostate Cancer With or Without Transperineal Injection of a Polyethylen Glycol Spacer: A Treatment Planning Comparison Study

Purpose: Rectal toxicity is a serious adverse effect in early-stage prostate cancer patients treated with curative radiation therapy (RT). Injecting a spacer between Denonvilliers' fascia increases the distance between the prostate and the anterior rectal wall and may thus decrease the rectal radiation-induced toxicity. We assessed the dosimetric impact of this spacer with advanced delivery RT techniques, including intensity modulated RT (IMRT), volumetric modulated arc therapy (VMAT), and intensity modulated proton beam RT (IMPT). Methods and Materials: Eight prostate cancer patients were simulated for RT with or without spacer. Plans were computed for IMRT, VMAT, and IMPT using the Eclipse treatment planning system using both computed tomography spacer+ and spacer- data sets. Prostate {+-} seminal vesicle planning target volume [PTV] and organs at risk (OARs) dose-volume histograms were calculated. The results were analyzed using dose and volume metrics for comparative planning. Results: Regardless of the radiation technique, spacer injection decreased significantly the rectal dose in the 60- to 70-Gy range. Mean V{sub 70Gy} and V{sub 60Gy} with IMRT, VMAT, and IMPT planning were 5.3 {+-} 3.3%/13.9 {+-} 10.0%, 3.9 {+-} 3.2%/9.7 {+-} 5.7%, and 5.0 {+-} 3.5%/9.5 {+-} 4.7% after spacer injection. Before spacer administration, the corresponding values were 9.8 {+-} 5.4% (P=.012)/24.8 {+-} 7.8% (P=.012), 10.1 {+-} 3.0% (P=.002)/17.9 {+-} 3.9% (P=.003), and 9.7 {+-} 2.6% (P=.003)/14.7% {+-} 2.7% (P=.003). Importantly, spacer injection usually improved the PTV coverage for IMRT. With this technique, mean V{sub 70.2Gy} (P=.07) and V{sub 74.1Gy} (P=0.03) were 100 {+-} 0% to 99.8 {+-} 0.2% and 99.1 {+-} 1.2% to 95.8 {+-} 4.6% with and without Spacer, respectively. As a result of spacer injection, bladder doses were usually higher but not significantly so. Only IMPT managed to decrease the rectal dose after spacer injection for all dose levels, generally with no observed increase to the bladder dose. Conclusions: Regardless of the radiation technique, a substantial decrease of rectal dose was observed after spacer injection for curative RT to the prostate.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Prostate Hypofractionated Radiation Therapy With Injection of Hyaluronic Acid: Acute Toxicities in a Phase 2 Study

Purpose: Hypofractionated radiation therapy (RT) in prostate cancer can be developed only if the risk of rectal toxicity is controlled. In a multicenter phase 2 trial, hypofractionated irradiation was combined with an injection of hyaluronic acid (HA) to preserve the rectal wall. Tolerance of the injection and acute toxicity rates are reported. Methods and Materials: The study was designed to assess late grade 2 toxicity rates. The results described here correspond to the secondary objectives. Acute toxicity was defined as occurring during RT or within 3 months after RT and graded according to the Common Terminology Criteria for Adverse Events version 4.0. HA tolerance was evaluated with a visual analog scale during the injection and 30 minutes after injection and then by use of the Common Terminology Criteria at each visit. Results: From 2010 to 2012, 36 patients with low-risk to intermediate-risk prostate cancer were included. The HA injection induced a mean pain score of 4.6/10 ± 2.3. Thirty minutes after the injection, 2 patients still reported pain (2/10 and 3/10), which persisted after the intervention. Thirty-three patients experienced at least 1 acute genitourinary toxicity and 20 patients at least 1 acute gastrointestinal toxicity. Grade 2 toxicities were reported for 19 patients with urinary obstruction, frequency, or both and for 1 patient with proctitis. No grade 3 or 4 toxicities were reported. At the 3-month visit, 4 patients described grade 2 obstruction or frequency, and no patients had any grade 2 gastrointestinal toxicities. Conclusions: The injection of HA makes it possible to deliver hypofractionated irradiation over 4 weeks with a dose per fraction of > 3 Gy, with limited acute rectal toxicity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Prospective Randomized Comparison of the Effectiveness of Radiation Therapy and Local Steroid Injection for the Treatment of Plantar Fasciitis

Purpose: The purpose of this study was to conduct a randomized trial of radiation therapy for plantar fasciitis and to compare radiation therapy with local steroid injections. Methods and Materials: Between March 2013 and April 2014, 128 patients with plantar fasciitis were randomized to receive radiation therapy (total dose of 6.0 Gy applied in 6 fractions of 1.0 Gy three times a week) or local corticosteroid injections a 1 ml injection of 40 mg methylprednisolone and 0.5 ml 1% lidocaine under the guidance of palpation. The results were measured using a visual analog scale, a modified von Pannewitz scale, and a 5-level function score. The fundamental phase of the study was 3 months, with a follow-up period of up to 6 months. Results: The median follow-up period for all patients was 12.5 months (range, 6.5-18.6 months). For the radiation therapy patients, the median follow-up period was 13 months (range, 6.5-18.5 months), whereas in the palpation-guided (PG) steroid injection arm, it was 12.1 months (range, 6.5-18.6 months). After 3 months, results in the radiation therapy arm were significantly superior to those in the PG steroid injection arm (visual analog scale, P<.001; modified von Pannewitz scale, P<.001; 5-level function score, P<.001). Requirements for a second treatment did not significantly differ between the 2 groups, but the time interval for the second treatment was significantly shorter in the PG steroid injection group (P=.045). Conclusion: This study confirms the superior analgesic effect of radiation therapy compared to mean PG steroid injection on plantar fasciitis for at least 6 months after treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Modeling injection-induced fault slip using long short-term memory networks

Stress changes due to changes in fluid pressure and temperature in a faulted formation may lead to the opening/shearing of the fault. This can be due to subsurface (geo)engineering activities such as fluid injections and geologic disposal of nuclear waste. Such activities are expected to rise in the future making it necessary to assess their short- and long-term safety. Here, a new machine learning (ML) approach to model pore pressure and fault displacements in response to high-pressure fluid injection cycles is developed. The focus is on fault behavior near the injection borehole. To capture the temporal dependencies in the data, long short-term memory (LSTM) networks are utilized. To prevent error accumulation within the forecast window, four critical measures to train a robust LSTM model for predicting fault response are highlighted: (i) setting an appropriate value of LSTM lag, (ii) calibrating the LSTM cell dimension, (iii) learning rate reduction during weight optimization, and (iv) not adopting an independent injection cycle as a validation set. Several numerical experiments were conducted, which demonstrated that the ML model can capture peaks in pressure and associated fault displacement that accompany an increase in fluid injection. The model also captured the decay in pressure and displacement during the injection shut-in period. Further, the ability of an ML model to highlight key changes in fault hydromechanical activation processes was investigated, which shows that ML can be used to monitor risk of fault activation and leakage during high pressure fluid injections.

58 GEOSCIENCES↗
DOE OSTI2026

Deuterium retention characteristics during lithium powder and granule injection in EAST

Fuel retention remains a critical challenge for magnetic confinement fusion devices. As a low-Z material, lithium plays a key role in tokamak wall conditioning and impurity control. In this study, the fuel retention behaviors associated with two lithium forms—powder and granule—are systematically examined using the gas balance method. Both forms of lithium injection significantly enhance fuel retention, shifting the wall behavior from net outgassing to net absorption. For lithium powder injection, compared with the reference discharge, a suppression efficiency exceeding 40% is achieved relative to the number of injected lithium atoms. Moreover, discharges with different injection rates show a monotonic increase in retained fuel with the injected lithium quantity. In contrast, repeated granule injections exhibit a pronounced cumulative effect, with the retention ratio varying from 0.16 to 0.65 over successive discharges, indicating progressive enhancement of wall absorption and deuterium retention. These results advance the understanding of wall behavior modification induced by solid material injection and provide insights for developing effective wall-conditioning strategies using low-Z materials in ITER and future fusion reactors, while the expected high retention may ultimately exclude the use of Li wall conditioning in future fusion devices.

Fuel retention↗
DOE OSTI2019

Seasonal Injection Strategies for Stratospheric Aerosol Geoengineering

Simulations of stratospheric aerosol geoengineering have typically considered injections at a constant rate over the entire year. However, the seasonal variability of both sunlight and the stratospheric circulation suggests seasonally-dependent injection strategies. In this work, we simulated single point injections of the same amount of SO 2 in each of the four seasons and at five different latitudes (30S, 15S, Equator, 15N, 30N), 5 km above the tropopause. Our findings suggest that injecting only during one season reduces the amount of SO 2 needed to achieve a certain aerosol optical depth (AOD), thus potentially reducing some of the side-effects of geoengineering. We find, in particular, that injections at 15N or 15S in spring of the corresponding hemisphere results in the largest reductions in incoming solar radiation. Compared to annual injections, by injecting in the different seasons we identify additional distinct spatiotemporal AOD patterns, thanks to seasonal differences in the stratospheric circulation.

58 GEOSCIENCES↗
DOE OSTI2013

Studies of beam injection with a compensated bump and uncompensated bump in a synchrotron

Synchrotron radiation sources Indus-1 and Indus-2 have a synchrotron as the common injector. A three kicker compensated bump injection scheme was employed for beam injection into this synchrotron. The stored beam current in the synchrotron is higher, when all the three kickers are operated at the same current than when kickers are operated at currents required to generate compensated bump. Beam dynamics studies have been done to understand why this happens. Theoretical studies indicate that higher stored current in the later case is attributed to smaller residual oscillations of injected beam. These studies also reveal that if the angle of the injected beam during beam injection is kept varying, the performance could be further improved. This is experimentally confirmed by injecting the beam on rising part of the injection septum magnet current pulse.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Comparative study of boron and neon injections on divertor heat fluxes using SOLPS-ITER simulations

Here, based on the EAST equilibrium, the effects of boron (B) and neon (Ne) injected at different locations on the target heat load, and the distributions of B and Ne particles were investigated by transport code SOLPS-ITER. It was found that the B injection was more sensitive to the injection location for heat flux control than impurity Ne. The high electron and ion densities near the inner target in the discharge with impurity B injected from over X-point (R 1 ) led to plasma detachment only at the inner target, and the localized B ions in the cases with injection from outer target location (R 2 ) and upstream location (R 3 ) led to far-SOL detachment at the outer target, but not at the inner target. In contrast, for Ne, the spatial distributions of Ne ions and electrons were found to be similar in all the cases at the three injection locations, and the detached plasma was achieved at the inner target and the electron temperature was reduced at the outer target. For locations R 2 and R 3 , impurity B showed a more pronounced effect on the heat flux at the far-SOL of the outer target. Further analysis indicated that Ne atoms came mainly from the recycling sources, whereas B atoms came mainly from injection, and that their distinct atomic distributions resulted from the difference in the ionization threshold and ionization mean free path. In addition, the radiation proportion of B in the divertor region was larger than that of Ne when the total radiation power was similar, which suggests that B has less influence on the core region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Core plasma fueling by fast inward particle transport after hydrogen pellet injection in Wendelstein 7-X

A large database of more than 1000 individual cryogenic hydrogen pellets injected into Wendelstein 7-X for plasma fueling was analyzed to improve the understanding of the three phases of the process: the ablation, deposition and transport of the pellet material. Kilohertz-sampled electron density and temperature measurements revealed a more complex drift behavior than predicted by numerical code simulation. It could be explained by the poloidal plasma E r x B- drift rotation, which plays a significant role in stellarators, but was not previously considered in pellet injection codes like HPI2. The drift results in a fast poloidal rotation of the pellet material around the plasma core, leading to an almost homogeneous deposition over the involved flux surfaces regardless of magnetic high and low field side injection geometry. Additionally, a novel fast inward directed transport mechanism (‘FIT-effect’) was observed. The effect occurs on timescales of tens of milliseconds and cannot be explained by neoclassical transport or diffusion. It might be linked to the turbulence pinch recently found in Wendelstein 7-X. When the FIT-effect occurs, the pellet particles are rapidly transferred from the deposition flux surfaces to the plasma core, causing the plasma density profile to peak, which is beneficial for confinement in Wendelstein 7-X. The large pellet injection database was statistical analyzed with regard to pellet and plasma parameters, which delivered some starting points towards developing an understanding of the physics behind the FIT-effect. The results indicate, that plasma core fueling via pellet injection is largely independent of the injection geometry in stellarators under certain conditions, reducing the technical complexity of the injection system.

Wendelstein 7-X↗