Results for “reach code” — Page 44

DOE OSTI2022

BISON fuel performance modeling optimization for experiment X447 and X447A using axial swelling and cladding strain measurements

With the recent need to qualify new reactor designs such as the Versatile Test Reactor (VTR), fuel performance calculations need to be performed to determine safety criteria of the proposed designs. In order to validate the fuel performance results obtained by a fuel performance code, BISON, for new reactor designs, legacy fuel from EBR-II and FFTF MFF with Post -Irradiation Examination (PIE) data need to be used as validation cases to benchmark models. Here in this work, BISON has been paired with the Fuels Irradiation & Physics Database (FIPD) and IFR Materials Information System (IMIS) to supply PIE data for comparison with simulations of EBR-II experiments X447/X447A. X447/X447A were assessed by implementing models for Fuel Cladding Chemical Interaction (FCCI) within BISON and optimizing the friction coefficient between the fuel surface and the cladding, the anisotropic swelling factor, and the HT9 first thermal creep scalar (which scales the first term in the HT9 creep equation) to best match the PIE axial fuel swelling height and cladding profilometry for all pins in X447/X447A. The optimal values were found using a generic algorithm developed to select different values for the three parameters until end criteria was met and error couldn’t be reduced further. The BISON-simulated cladding profilometry was evaluated using Standard Error of the Estimate (SEE) to account for the profile shape of the cladding profilometry. Optimal values for the friction coefficient, anisotropic fuel swelling factor, and HT9 first thermal creep scalar were found to best fit the BISON simulation results to the PIE measurements found in IMIS and FIPD. Improvements to current models are suggested to account for the underprediction of fuel swelling at low burnups and the overprediction of fuel swelling at higher burnups observed for the axial fuel swelling height. Although two pins in EBR-II X447/X447A (DP70 and DP75) were known to fail due to FCCI, none of the pins simulated in BISON reached a cumulative damage fraction (CDF) above 0.008 with FCCI correlations coupled in the BISON simulations. The error estimate generated for all pins in X447/X447A using optimal values was 209 µm, which is deemed acceptable.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2014

Dynamic load balance scheme for the DSMC algorithm

The direct simulation Monte Carlo (DSMC) algorithm, devised by Bird, has been used over a wide range of various rarified flow problems in the past 40 years. While the DSMC is suitable for the parallel implementation on powerful multi-processor architecture, it also introduces a large load imbalance across the processor array, even for small examples. The load imposed on a processor by a DSMC calculation is determined to a large extent by the total of simulator particles upon it. Since most flows are impulsively started with initial distribution of particles which is surely quite different from the steady state, the total of simulator particles will change dramatically. The load balance based upon an initial distribution of particles will break down as the steady state of flow is reached. The load imbalance and huge computational cost of DSMC has limited its application to rarefied or simple transitional flows. In this paper, by taking advantage of METIS, a software for partitioning unstructured graphs, and taking the total of simulator particles in each cell as a weight information, the repartitioning based upon the principle that each processor handles approximately the equal total of simulator particles has been achieved. The computation must pause several times to renew the total of simulator particles in each processor and repartition the whole domain again. Thus the load balance across the processors array holds in the duration of computation. The parallel efficiency can be improved effectively. The benchmark solution of a cylinder submerged in hypersonic flow has been simulated numerically. Besides, hypersonic flow past around a complex wing-body configuration has also been simulated. The results have displayed that, for both of cases, the computational time can be reduced by about 50%.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

Hybrid-PIC modeling of laser-plasma interactions and hot electron generation in gold hohlraum walls

The walls of the hohlraum used in experiments at the national ignition facility are heated by laser beams with intensities ∼1015 W/cm2, a wavelength of ∼1/3 μm, and pulse lengths on the order of a ns, with collisional absorption believed to be the primary heating mechanism. X-rays generated by the hot ablated plasma at the gold walls are then used to implode a target in the hohlraum interior. In addition to the collisional absorption of laser energy at the walls, non-linear laser-plasma interactions (LPI), such as stimulated Raman scattering and two plasmon decay, are believed to generate a population of supra-thermal electrons which, if present in the hohlraum, can have a deleterious effect on target implosion. We describe results of hohlraum modeling using a hybrid particle-in-cell code. To enable this work, new particle-based algorithms for a multiple-ion magneto-hydrodynamic (MHD) treatment, and a particle-based ray-tracing model were developed. The use of such hybrid methods relaxes the requirement to resolve the laser wavelength, and allows for relatively large-scale hohlraum simulations with a reasonable number of cells. But the non-linear effects which are believed to be the cause of hot electron generation can only be captured by fully kinetic simulations with good resolution of the laser wavelength. For this reason, we employ a two-tiered approach to hohlraum modeling. Large-scale simulations of the collisional absorption process can be conducted using the fast quasi-neutral MHD algorithm with fluid particle species. From these simulations, we can observe the time evolution of the hohlraum walls and characterize the density and temperature profiles. From these results, we can transition to smaller-scale highly resolved simulations using traditional kinetic particle-in-cell methods, from which we can fully model all of the non-linear laser-plasma interactions, as well as assess the details of the electron distribution function. We find that vacuum hohlraums should be stable to both two plasmon decay and stimulated Raman scattering instabilities for intensities ≤1015 W/cm2. In gas-filled hohlraums, shocks may be induced in the blowoff gold plasma, which leads to more complex density and temperatures profiles. The resulting effect on LPI stability depends strongly on the details of the profile, and it is possible for the gas-filled hohlraum to become unstable to two plasmon decay at 1015 W/cm2 if the quarter-critical surface reaches temperatures exceeding 1 keV.

Thoma, C.↗

DOE OSTI2011

TRISO Fuel Performance: Modeling, Integration into Mainstream Design Studies, and Application to a Thorium-fueled Fusion-Fission Hybrid Blanket

This study focused on creating a new tristructural isotropic (TRISO) coated particle fuel performance model and demonstrating the integration of this model into an existing system of neutronics and heat transfer codes, creating a user-friendly option for including fuel performance analysis within system design optimization and system-level trade-off studies. The end product enables both a deeper understanding and better overall system performance of nuclear energy systems limited or greatly impacted by TRISO fuel performance. A thorium-fueled hybrid fusion-fission Laser Inertial Fusion Energy (LIFE) blanket design was used for illustrating the application of this new capability and demonstrated both the importance of integrating fuel performance calculations into mainstream design studies and the impact that this new integrated analysis had on system-level design decisions. A new TRISO fuel performance model named TRIUNE was developed and verified and validated during this work with a novel methodology established for simulating the actual lifetime of a TRISO particle during repeated passes through a pebble bed. In addition, integrated self-consistent calculations were performed for neutronics depletion analysis, heat transfer calculations, and then fuel performance modeling for a full parametric study that encompassed over 80 different design options that went through all three phases of analysis. Lastly, side studies were performed that included a comparison of thorium and depleted uranium (DU) LIFE blankets as well as some uncertainty quantification work to help guide future experimental work by assessing what material properties in TRISO fuel performance modeling are most in need of improvement. A recommended thorium-fueled hybrid LIFE engine design was identified with an initial fuel load of 20MT of thorium, 15% TRISO packing within the graphite fuel pebbles, and a 20cm neutron multiplier layer with beryllium pebbles in flibe molten salt coolant. It operated at a system power level of 2000 MW th , took about 3.5 years to reach full plateau power, and was capable of an End of Plateau burnup of 38.7 %FIMA if considering just the neutronic constraints in the system design; however, fuel performance constraints led to a maximum credible burnup of 12.1 %FIMA due to a combination of internal gas pressure and irradiation effects on the TRISO materials (especially PyC) leading to SiC pressure vessel failures. The optimal neutron spectrum for the thorium-fueled blanket options evaluated seemed to favor a hard spectrum (low but non-zero neutron multiplier thicknesses and high TRISO packing fractions) in terms of neutronic performance but the fuel performance constraints demonstrated that a significantly softer spectrum would be needed to decrease the rate of accumulation of fast neutron fluence in order to improve the maximum credible burnup the system could achieve.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

AGR-3/4 Irradiation Test Predictions using PARFUME

PARFUME, a fuel performance modeling code used for high temperature gas reactors, was used to model the AGR-3/4 irradiation test using as-run physics and thermal hydraulics data. The AGR-3/4 test is the combined third and fourth planned irradiations of the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program. The AGR-3/4 test train consists of twelve separate and independently controlled and monitored capsules. Each capsule contains four compacts filled with both uranium oxycarbide (UCO) unaltered “driver” fuel particles and UCO designed-to-fail (DTF) fuel particles. The DTF fraction was specified to be 1×10-2. This report documents the calculations performed to predict failure probability of TRISO-coated fuel particles during the AGR-3/4 experiment. In addition, this report documents the calculated source term from both the driver fuel and DTF particles. The calculations include the modeling of the AGR-3/4 irradiation that occurred from December 2011 to April 2014 in the Advanced Test Reactor (ATR) over a total of ten ATR cycles including seven normal cycles, one low power cycle, one unplanned outage cycle, and one Power Axial Locator Mechanism cycle. Results show that failure probabilities are predicted to be low, resulting in zero fuel particle failures per capsule. The primary fuel particle failure mechanism occurred as a result of localized stresses induced by the calculated IPyC cracking. Assuming 1,872 driver fuel particles per compact, failure probability calculated by PARFUME leads to no predicted particle failure in the AGR-3/4 driver fuel. In addition, the release fraction of fission products Ag, Cs, and Sr were calculated to vary depending on capsule location and irradiation temperature. The maximum release fraction of Ag occurs in Capsule 7 reaching up to 56% for the driver fuel and 100% for the DTF fuel. The release fraction of the other two fission products, Cs and Sr, are much smaller and in most cases less than 1% for the driver fuel. The notable exception occurs in Capsule 7 where the release fraction for Cs and Sr reach up to 0.73% and 2.4%, respectively, for the driver fuel. For the DTF fuel in Capsule 7, the release fraction for Cs and Sr are estimated to be 100% and 5%, respectively.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2011

DUST PROCESSING IN SUPERNOVA REMNANTS: SPITZER MIPS SPECTRAL ENERGY DISTRIBUTION AND INFRARED SPECTROGRAPH OBSERVATIONS

We present Spitzer Multiband Imaging Photometer (MIPS) spectral energy distribution (SED) and Infrared Spectrograph (IRS) observations of 14 Galactic supernova remnants (SNRs) previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [O I] emission, ionic lines, and emission from molecular hydrogen. Through blackbody fitting of the MIPS SEDs we find the large grains to be warm, 29-66 K. The dust emission is modeled using the DUSTEM code and a three-component dust model composed of populations of big grains (BGs), very small grains (VSGs), and polycyclic aromatic hydrocarbons. We find the dust to be moderately heated, typically by 30-100 times the interstellar radiation field. The source of the radiation is likely hydrogen recombination, where the excitation of hydrogen occurred in the shock front. The ratio of VSGs to BGs is found for most of the molecular interacting SNRs to be higher than that found in the plane of the Milky Way, typically by a factor of 2-3. We suggest that dust shattering is responsible for the relative overabundance of small grains, in agreement with the prediction from dust destruction models. However, two of the SNRs are best fitted with a very low abundance of carbon grains to silicate grains and with a very high radiation field. A likely reason for the low abundance of small carbon grains is sputtering. We find evidence for silicate emission at 20 {mu}m in their SEDs, indicating that they are young SNRs based on the strong radiation field necessary to reproduce the observed SEDs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

TU-D-201-00: Use of End-Of-Life Brachytherapy Devices

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2016

Fuel Performance Simulation of Iron-Chrome-Aluminum Cladding during Steady-State LWR Operation

During a severe accident scenario, such as a loss-of-coolant accident, a nuclear reactor may lose its capacity to cool its fuel. The fuel rod temperatures begin to increases, quickly reaching temperatures where the coolant begins to evaporate. This lowers the coolant level in the core and eventually uncovers the fuel. Without sufficient heat transfer from the fuel rods to the coolant, the temperature of the fuel and cladding will increase dramatically. In the case of traditional zirconium-based alloys, as the temperature of the cladding reaches ∼1200 deg. C the zirconium rapidly begins to oxidize with H{sub 2}O in the coolant and steam. This oxidation reaction causes both thinning of the Zr-alloy cladding as the metal reacts and releases large amounts of H{sub 2} gas into the reactor pressure vessel. In order to increase the safety margin of LWR fuel in severe accident scenarios, several alternative cladding materials have been proposed to replace the currently used zirconium-based alloys. Of these materials, there is a particular focus on select iron-chrome-aluminum (FeCrAl) alloys because of slower oxidation Kinetics in high temperature steam than zirconium-based alloys. This increased oxidation resistance may provide additional coping time to mitigate any further damage resulting from an accident. However, by changing the cladding material, the neutronic characteristics of the core will change. FeCrAl alloys exhibit thermal neutron absorption cross sections nearly ∼12-16 x greater than Zr-alloys. This decreases the reactivity of the core, subsequently decreasing the potential cycle length for operation. To counteract this, fissile material may be added in the form of increased enrichment or increased fuel mass or the cladding thickness might be decreased, effectively reducing the neutronic penalty from using the alloy. In this study, all three changes are considered. To assess the viability of FeCrAl as an alternative cladding to Zr-alloys, engineering-scale fuel performance analysis is used to monitor the cladding and integral fuel rod behavior through its operation. Ongoing work is being performed to identify key parameters essential to modeling FeCrAl alloys for LWR applications and properly model fuel compliance and stress relief mechanisms for UO{sub 2} fuel. To improve the predictive capability of fuel performance codes for FeCrAl cladding under normal operation, high-fidelity mechanistic/physics-based material models are needed. This information can be generated and improved by access to experimental data on targeted FeCrAl alloys. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2015

TU-PIS-Exhibit Hall-2: Deformable Image Registration, Contour Propagation, and Dose Mapping inMIM Maestro - MIM Software

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-PIS-Exhibit Hall-3: Under the hood of Deformable Image Registration: Similarity Functions and Regularization

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-PIS-Exhibit Hall-4: Philips Pinnacle3 clinical solutions for adaptive radiotherapy

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-PIS-Exhibit Hall-5: ABAS - Atlas Based Auto Segmentation

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-D-201-01: Definition and Purpose of End-Of-Life for Brachytherapy Devices and Software

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-D-201-02: Physicist’s Responsibility On “End-Of-Life for Brachytherapy Devices and Software

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-D-201-03: Proposed Solutions to End-Of-Life Issue

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2015

TU-PIS-Exhibit Hall-1: Therapy: Deformable Image Registration, Contour Propagation, and Dose Mapping

Brachytherapy devices and software are designed to last for a certain period of time. Due to a number of considerations, such as material factors, wear-and-tear, backwards compatibility, and others, they all reach a date when they are no longer supported by the manufacturer. Most of these products have a limited duration for their use, and the information is provided to the user at time of purchase. Because of issues or concerns determined by the manufacturer, certain products are retired sooner than the anticipated date, and the user is immediately notified. In these situations, the institution is facing some difficult choices: remove these products from the clinic or perform tests and continue their usage. Both of these choices come with a financial burden: replacing the product or assuming a potential medicolegal liability. This session will provide attendees with the knowledge and tools to make better decisions when facing these issues. Learning Objectives: Understand the meaning of “end-of-life or “life expectancy” for brachytherapy devices and software Review items (devices and software) affected by “end-of-life” restrictions Learn how to effectively formulate “end-of-life” policies at your institution Learn about possible implications of “end-of-life” policy Review other possible approaches to “end-of-life” issue.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2014

Lower hybrid current drive favoured by electron cyclotron radiofrequency heating

The important goal of adding to the bootstrap a fraction of non-inductive plasma current, which would be controlled for obtaining and optimizing steady-state profiles, can be reached by using the Current Drive produced by Lower Hybrid waves (LHCD). FTU (Frascati Tokamak Upgrade) experiments demonstrated, indeed, that LHCD is effective at reactor-graded high plasma density, and the LH spectral broadening is reduced, operating with higher electron temperature in the outer region of plasma column (T{sub e-periphery}). This method was obtained following the guidelines of theoretical predictions indicating that the broadening of launched spectrum produced by parametric instability (PI) should be reduced, and the LHCD effect at high density consequently enabled, under higher (T{sub e-periphery}). In FTU, the temperature increase in the outer plasma region was obtained by operating with reduced particle recycling, lithized walls and deep gas fuelling by means of fast pellet. Heating plasma periphery with electron cyclotron resonant waves (ECRH) will provide a further tool for achieving steady-state operations. New FTU experimental results are presented here, demonstrating that temperature effect at the plasma periphery, affecting LH penetration, occurs in a range of plasma parameters broader than in previous work. New information is also shown on the modelling assessing frequencies and growth rates of the PI coupled modes responsible of spectral broadening. Finally, we present the design of an experiment scheduled on FTU next campaign, where ECRH power is used to slightly increase the electron temperature in the outer plasma region of a high-density discharge aiming at restoring LHCD. Consequent to model results, by operating with a toroidal magnetic field of 6.3 T, useful for locating the electron cyclotron resonant layer at the periphery of the plasma column (r/a∼0.8, f{sub 0}=144 GHz), an increase of T{sub e} in the outer plasma (from 40 eV to 80 eV at r/a∼0.8) is expected by the JETTO code, sufficient for recovering LHCD. An ECRH power of 0.8 MW, and the standard FTU regime at high plasma density (n{sub eav}∼1.3×10{sup 20}m{sup −3} and plasma current of 0.5 MA) have been considered. The code has been set with transport modelling to reproduce the evolution of FTU kinetic profiles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

SU-C-201-01: Investigation of the Effects of Scintillator Surface Treatment On Light Output Measurements with SiPM Detectors

Purpose: To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM). Methods: Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light produced by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital-SiPM sensor (DPC-3200). Results: The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face. Conclusion: This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗