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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

A flexible event reconstruction based on machine learning and likelihood principles

Event reconstruction is a central step in many particle physics experiments, turning detector observables into parameter estimates; for example estimating the energy of an interaction given the sensor readout of a detector. A corresponding likelihood function is often intractable, and approximations need to be constructed. Here, in our work, we first show how the full likelihood for a many-sensor detector can be broken apart into smaller terms, and secondly how we can train neural networks to approximate all terms solely based on forward simulation. Our technique results in a fast, flexible, and close-to-optimal surrogate model proportional to the likelihood and can be used in conjunction with standard inference techniques allowing for a consistent treatment of uncertainties. We illustrate our technique for parameter inference in neutrino telescopes based on maximum likelihood and Bayesian posterior sampling. Given its great flexibility, we also showcase our method for geometry optimization enabling to learn optimal detector designs. Lastly, we apply our method to realistic simulation of a ton-scale water-based liquid scintillator detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, d-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Progress in the design of the future circular collider FCC-ee interaction region

In this paper we discuss the latest developments for the FCC-ee interaction region layout, which represents one of the key ingredients to establish the feasibility of the FCC-ee. The collider has to achieve extremely high luminosities over a wide range of center-of-mass energies with two or four interaction points. The complex final focus hosted in the detector region has to be carefully designed, and the impact of beam losses and of any type of synchrotron radiation generated in the interaction region, including beamstrahlung, have to be evaluated in detail with simulations. We give an overview of the progress of the whole machine-detector-interface-related studies, among which are the updated mechanical model of the interaction region, the plans for a novel R&D activity of a IR mockup which is just starting, the collimation scheme and evaluation of beam induced backgrounds in the detectors, evaluation of radiation dose in the experimental area, and MDI integration with the detector.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Experimental concept and design of DarkLight, a search for a heavy photon

This talk gives an overview of the DarkLight experimental concept: a search for a heavy photon A′ in the 10-90 MeV/c{sup 2} mass range. After briefly describing the theoretical motivation, the talk focuses on the experimental concept and design. Topics include operation using a half-megawatt, 100 MeV electron beam at the Jefferson Lab FEL, detector design and performance, and expected backgrounds estimated from beam tests and Monte Carlo simulations.

43 PARTICLE ACCELERATORS↗
NASA NTRS1987

Technology for satellite power conversion

The work is this reporting period was concentrated on electronically calibrating the bolometer detectors. The calibration is necessary for two reasons: first, the power delivered to the rectifying circuit must be known in order to choose a diode with the appropriate barrier height, and second, the power captured by the antenna must be measured if the efficiency of the rectenna is to be divided into antenna efficiency and rectification efficiency. The millimeter wave region operation of the bolometers was simulated with a VHF (10 to 90 MHz) test signal. These detectors are accurate to within roughly 10%. The typical responsivity of the bolometers is 10 volts/watt and the NEP at 20 Hz is 5 times 10 to the minus 9th power W(Hz)-1/2.

Gouker, M. A.↗
DOE OSTI2022

Conceptual Design of a Scintillator-Based Fast-Ion Loss Detector for the Wendelstein 7-X Stellarator

Here, a conceptual design of a scintillator-based fast-ion loss detector (FILD) has been developed for the Wendelstein 7-X stellarator (W7-X). Simulations using the Monte Carlo codes ASCOT5 and BEAMS3D have been performed to calculate the expected flux of neutral beam injection (NBI)-generated fast hydrogen ions onto the conceptual detector probe head. These fast-ion loss fluxes have been calculated for several magnetic field configurations as well as probe insertion positions. At the maximum insertion position, both co-and counter-going losses with high incident pitch angles are observed; however, at retracted positions, only co-going fast ions reach the probe head. The FILDSIM code has been used to optimize the geometry of the detector entrance and collimating elements to achieve a wide velocity space coverage as well as a high velocity–space resolution. A synthetic FILD signal is calculated for the expected loss distribution via forward modeling using the instrument response function. The synthetic signal is found to largely retain the velocity space features of the loss distribution.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Modeling surface backgrounds from radon progeny plate-out

The next generation low-background detectors operating deep underground aim for unprecedented low levels of radioactive backgrounds. The surface deposition and subsequent implantation of radon progeny in detector materials will be a source of energetic background events. We investigate Monte Carlo and model-based simulations to understand the surface implantation profile of radon progeny. Depending on the material and region of interest of a rare event search, these partial energy depositions can be problematic. Motivated by the use of Ge crystals for the detection of neutrinoless double-beta decay, we wish to understand the detector response of surface backgrounds from radon progeny. We look at the simulation of surface decays using a validated implantation distribution based on nuclear recoils and a realistic surface texture. Results of the simulations and measured α spectra are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2010

New tracking system of the SND detector

A new tracking system (TS) of the Spherical Neutral Detector (SND) for experiments at the VEPP-2000 e{sup +}e{sup -} collider is described. The TS is completely assembled, mounted on the detector, and ready for collecting data from the VEPP-2000. Test experiments with cosmic-ray events and VEPP-2000 beams showed a stable operation of the system. The simulation, calibration, and reconstruction procedures were debugged by using available data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

TH-AB-201-11: Small-Field Beam Quality Corrections and Their Clinical Impact for Flattened and Unflattened Fields of the TrueBeam

Purpose: To determine small-field beam quality correction factors for several detectors used with flattened and unflattened beams of the Varian TrueBeam accelerator, and to quantify the clinical impact of these corrections through a treatment planning study. Methods: Small-field beam quality correction factors were measured and simulated in EGSnrc for several microchambers and diodes. The Exradin W1 plastic scintillation detector was used as a reference for the measured results, and its response was validated using alanine measurements traceable to a primary standard. Symmetric, jaw-defined field sizes ranging from 6 mm to 10 cm were used. Twelve hypofractionated clinical cases were then recalculated and/or reoptimized using beam models that were modified based on the resulting output factors. Three-dimensional dose distributions and cumulative dose-volume-histogram plots were compared between the models. The impact of these measurements on the flattening-filter-scatter-source (FFSS) model, and its subsequent effect on treatment plans, was also investigated. Results: The diodes exhibited over-response in small fields, whereas the microchambers tended to under-respond as field size decreased. Field-size-dependent effects were less significant for the flattening-filter-free beams (i.e., corrections were closer to unity) than for flattened fields of the same size. Recalculated and reoptimized plans displayed varying levels of deviation from the original dose distributions, with larger discrepancies at effective jaw settings of 3×3 cm{sup 2} or smaller. Dose distributions calculated using uncorrected microchamber output factors and/or modified FFSS showed large discrepancies in the low-dose regions, which manifested as DVH changes for the organs at risk (OAR). Conclusion: Field-size-dependent beam quality corrections were measured and simulated for ionization chambers and diodes typically used in small fields. Plans calculated with models based on these measured data showed dosimetric deviations mainly out of field, which affected OAR dose metrics. Accordingly, these beam quality corrections should be accounted for during commissioning to ensure greater treatment planning accuracy.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2015

SU-C-304-01: Investigation of Various Detector Response Functions and Their Geometry Dependence in a Novel Method to Address Ion Chamber Volume Averaging Effect

Purpose: A novel convolution-based approach has been proposed to address ion chamber (IC) volume averaging effect (VAE) for the commissioning of commercial treatment planning systems (TPS). We investigate the use of various convolution kernels and its impact on the accuracy of beam models. Methods: Our approach simulates the VAE by iteratively convolving the calculated beam profiles with a detector response function (DRF) while optimizing the beam model. At convergence, the convolved profiles match the measured profiles, indicating the calculated profiles match the “true” beam profiles. To validate the approach, beam profiles of an Elekta LINAC were repeatedly collected with ICs of various volumes (CC04, CC13 and SNC 125) to obtain clinically acceptable beam models. The TPS-calculated profiles were convolved externally with the DRF of respective IC. The beam model parameters were reoptimized using Nelder-Mead method by forcing the convolved profiles to match the measured profiles. We evaluated three types of DRFs (Gaussian, Lorentzian, and parabolic) and the impact of kernel dependence on field geometry (depth and field size). The profiles calculated with beam models were compared with SNC EDGE diode-measured profiles. Results: The method was successfully implemented with Pinnacle Scripting and Matlab. The reoptimization converged in ∼10 minutes. For all tested ICs and DRFs, penumbra widths of the TPS-calculated profiles and diode-measured profiles were within 1.0 mm. Gaussian function had the best performance with mean penumbra width difference within 0.5 mm. The use of geometry dependent DRFs showed marginal improvement, reducing the penumbra width differences to less than 0.3 mm. Significant increase in IMRT QA passing rates was achieved with the optimized beam model. Conclusion: The proposed approach significantly improved the accuracy of the TPS beam model. Gaussian functions as the convolution kernel performed consistently better than Lorentzian and parabolic functions. Further improvement of using geometry-dependent kernels was marginal.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Rapid evaluation of particle properties using inverse SEM simulations

The characteristic X-rays produced by the interactions of the electron beam with the sample in a scanning electron microscope (SEM) are usually captured with a variable-energy detector, a process termed energy dispersive spectrometry (EDS). The purpose of this work is to exploit inverse simulations of SEM-EDS spectra to enable rapid determination of sample properties, particularly elemental composition. This is accomplished using penORNL, a modified version of PENELOPE, and a modified version of the traditional Levenberg Marquardt nonlinear optimization algorithm, which together is referred to as MOZAIK-SEM. The overall conclusion of this work is that MOZAIK-SEM is a promising method for performing inverse analysis of X-ray spectra generated within a SEM. As this methodology exists now, MOZAIK-SEM has been shown to calculate the elemental composition of an unknown sample within a few percent of the actual composition.

Bekar, Kursat B↗
DOE OSTI2014

A benchmark concept for simulation in radiographic testing

The new standard ISO 17636–2:2013 “NDT of welds: Radiographic testing - Part 2: X- and gamma ray techniques with digital detectors” describes a complex procedure for film replacement by phosphor imaging plates and digital detector arrays. RT modeling software should consider these detector types, X-ray film, and the standard requirements for image quality. Practitioners expect the same visibility of image quality indicators (IQI) in the simulated radiographs as in the experimental exposures. The proposed benchmark test is based on the comparison of experimental radiographs taken at BAM with modeled ones of participants. The experimental setup and the determination of the equivalent penetrameter sensitivity (EPS) as described in the procedure of ASTM E 746 are used for quantitative evaluation of the achievable contrast sensitivity for step hole IQIs as considered in Annex B of ISO 17636–2. System classification data for Computed Radiography (CR) and film systems will be provided by BAM according to ISO 11699–1 for selected film systems and according to ASTM E 2446 for selected CR systems. The classification of films and digital detectors is based on the measurement of the dose response function, the basic spatial resolution (SR{sub b}) of the image, and the measured image noise, which depends on the detector efficiency, the quantum statistics, and the detector fixed pattern noise.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

A numerical solver for investigating the space charge effect on the electric field in liquid argon time projection chambers

This paper reports the development of a numerical solver aimed to simulate the interaction between the space charge (i.e. ions) distribution and the electric field in liquid argon time projection chamber (LArTPC) detectors. The ion transport equation is solved by a time-accurate, cell-centered finite volume method and the electric potential equation by a continuous finite element method. The electric potential equation updates the electric field which provides the drift velocity to the ion transport equation. The ion transport equation updates the space charge density distribution which appears as the source term in the electric potential equation. The interaction between the space charge distribution and the electric field is numerically simulated within each physical time step. The convective velocity in the ion transport equation can include the background flow velocity in addition to the electric drift velocity. The numerical solver has been parallelized using the Message Passing Interface (MPI) library. Numerical tests show and verify the capability and accuracy of the current numerical solver. It is planned that the developed numerical solver, together with a Computational Fluid Dynamics (CFD) package which provides the flow velocity field, can be used to investigate the space charge effect on the electric field in large-scale particle detectors.

42 ENGINEERING↗
DOE OSTI2019

Development of a novel high quantum efficiency MV x-ray detector for image-guided radiotherapy: A feasibility study

Purpose: To develop a new scintillating fiber-based electronic portal imaging device (EPID) with a high quantum efficiency (QE) while preserving an adequate spatial resolution. Methods: Two prototypes were built: one with a single pixel readout and the other with an active matrix flat-panel imager (AMFPI) for readout. The energy conversion layer of both prototypes was made of scintillating fiber layers interleaved with corrugated lead sheets to form a honeycomb pattern. The scintillating fibers have a diameter of 1 mm and the distance between the centers of neighboring fibers on the same layer is 1.35 mm. The layers have 1.22 mm spacing between them. The energy conversion layer has a thickness of 2 cm. The modulation transfer function (MTF), antiscatter properties and sensitivity of the detector with a single pixel readout were measured using a 6-MV beam on a LINAC machine. In addition, a Monte Carlo simulation was conducted to calculate the zero-frequency detective quantum efficiency (DQE(0)) of the proposed detector with an active matrix flat-panel imager for readout. Results: The DQE(0) of the proposed detector can be 11.5%, which is about an order of magnitude higher than that of current EPIDs. The frequency of 50% modulation (f 50 ) of the measured MTF is 0.2 mm –1 at 6 MV, which is comparable to that of video-based EPIDs. The scatter to primary ratio (SPR) measured with the detector at 10 cm air gap and 20 x 20 cm 2 field size is approximately 30% lower than that of ionization chamber–based detectors with a comparable QE. The detector noise which includes the x-ray quantum noise and absorption noise is much larger than the electronic noise per pixel of the flat-panel imager at a dose of less than two LINAC pulses. Thus, the proposed detector is quantum noise limited down to very low doses (~a couple of radiation pulses of the LINAC). A proof-of-concept image has been obtained using a 6-MV beam. Conclusions: This work indicates that by using scintillating fibers and lead layers it is possible to increase the thickness of the detecting materials, and therefore the QE or the DQE(0) of the detector, while maintaining an adequate spatial resolution for MV x-ray imaging. Due to the use of lead as the spacing material, the new detector also has antiscatter property, which will help improve the signal-to-noise ratio of the images. Further investigation to optimize the design of the detector and achieve a better combination of DQE and spatial resolution is warranted.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Operational Reactor Depletion Analysis Capability

The milestone for the operational reactor depletion demonstrates a cycle depletion simulation of Watt's Bar Unit 1 Cycle 1. The simulation was performed using the VERA-CS components MPACT and COBRA-TF. The simulation was performed on the Titan and Eos machines at the Oak Ridge Leadership Computing Facility. The simulation results include the critical boron concentration, the pin resolved power, temperature, and fluid density distributions, and detector responses as a function of time. These results are presented and the critical boron concentration is compared with measured data. The comparison is reasonable given the modeling approximation used at this point. Several suggestions, both near and longer term, are given for areas of future work which include improving the methods, data, models, and computational performance. For those solution results which are not compared to measurement, e.g. power and temperature distributions, their behavior coincides with analysts' expectations. An important next step in the validation of VERA-CS will be the comparison of the computational results to the measured flux data. To satisfy this L1 milestone, numerous capabilities were successfully added as a part of supporting L2 and L3 milestones. These include: full core depletion, generation of a new cross section library, coupling of neutronics and thermal hydraulic feedback, and detector response modeling. In addition to the operational reactor depletion, several 2-D core parametric studies were performed to assess the new simulation capability and to develop guidelines on model approximations and discretizations. Some of the conclusions from these studies are: • The simulation of B-10 depletion in the coolant is necessary to accurately predict critical boron concentrations, • If the end of cycle state is of primary interest in the simulation, then significant approximations may be made in the cycle history. The ability to make use of this approximation without a notable loss in accuracy will considerably accelerate multi-cycle analysis, • The new 47-group cross section library with a transport correction of the P 0 scattering can provide solutions very efficiently and which are nearly as accurate as solutions generated with explicit P 2 scattering, and • Simplified modeling of the equilibrium xenon concentration is well predicted by the existing depletion solver, and only in certain circumstances (e.g. large and "instantaneous" changes to rod position or T/H conditions) would an explicit physical model need to be included. Overall the milestone is considered a success as the objectives were met and several new and important results were produced from this work. The results and conclusions of this milestone will continue to guide future work and become the basis for addressing the CASL Challenge Problems.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2026

Precise Modeling of a Complex Solenoidal Magnetic Field Using a Combination of Analytic Functions and a PINN

We demonstrate an iterative approach to modeling a sparsely measured magnetic field in a large-bore solenoid. This approach uses a hybrid of traditional and machine learning techniques. The traditional technique is a linear least-squares fit using a series solution to Laplace's equation, while the machine learning technique involves the training of a physics-informed neural network (PINN) on the least-squares fit residuals. We use a newly defined activation function "DELTAsnake," a modification to the snake activation function proposed by Ziyin et al. that allows for stronger curvature and non-monotonicity. The combined model approximately obeys Maxwell's equations to a level sufficient for producing high quality physics simulations and analysis. Our approach is applied to a highly realistic calculation of the expected magnetic field in the Mu2e experiment's Detector Solenoid which includes a simple model for the expected statistical measurement uncertainties. Using ten toy measurement simulations, we demonstrate the capabilities of our model in comparison to the least-squares method alone; the least-squares method alone results in a reduced chi-squared statistic of ${2.15 \pm 0.01}$, while our approach improves the reduced chi-square to ${1.034 \pm 0.005}$. Furthermore, for an average toy simulation, we show that the range of the RMS of the three field component residuals reduces from ${0.07-0.37}$ Gauss to ${0.05-0.07}$ Gauss. We find that this novel method is robust against a realistic systematic uncertainty deriving from Hall probe calibration bias and can be used to significantly reduce the number of measurements required to achieve an accurate model.

Kampa, Cole [Caltech] (ORCID:0000000192972920)↗
DOE OSTI2024

Electromagnetic shower separation in LArTPCs: study of the calorimetric method at LArIAT

This thesis reports a study of the prospects of using calorimetry for separating photon- from electron-initiated electromagnetic (EM) showers in liquid argon time projection chambers (LArTPCs), a prevalent need for neutrino oscillation experiments based on the LArTPC technology as $\gamma$-initiated showers are a significant background to electron neutrino ($\nu_e$) events, whose signature is electron showers. From events simulated in the LArIAT (Liquid Argon In A Testbeam) experiment's detector, we quantitatively evaluated the dependence of the calorimetric separation on the initial momentum and position (along the beamline) of the primary particle. We could conclude that the separation is more efficient if the primary particle is created inside the chamber, whereas the impact of the momentum is not as significant. Furthermore, a first step was taken towards applying the calorimetric method to the showers measured in LArIAT. A convolutional neural network (CNN) trained on simulation was deployed to find EM showers among the events collected by the experiment. The charge deposition at the beginning of the showers found is centered at a plausible value, although the width of the distribution demands further inquiry.

43 PARTICLE ACCELERATORS↗