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DOE OSTI2015

TU-EF-207-04: Advances in Detector Technology for Breast Tomosynthesis

Breast imaging technology is advancing on several fronts. In digital mammography, the major technological trend has been on optimization of approaches for performing combined mammography and tomosynthesis using the same system. In parallel, photon-counting slot-scan mammography is now in clinical use and more efforts are directed towards further development of this approach for spectral imaging. Spectral imaging refers to simultaneous acquisition of two or more energy-windowed images. Depending on the detector and associated electronics, there are a number of ways this can be accomplished. Spectral mammography using photon-counting detectors can suppress electronic noise and importantly, it enables decomposition of the image into various material compositions of interest facilitating quantitative imaging. Spectral imaging can be particularly important in intravenously injected contrast mammography and eventually tomosynthesis. The various approaches and applications of spectral mammography are discussed. Digital breast tomosynthesis relies on the mechanical movement of the x-ray tube to acquire a number of projections in a predefined arc, typically from 9 to 25 projections over a scan angle of +/−7.5 to 25 degrees depending on the particular system. The mechanical x-ray tube motion requires relatively long acquisition time, typically between 3.7 to 25 seconds depending on the system. Moreover, mechanical scanning may have an effect on the spatial resolution due to internal x-ray filament or external mechanical vibrations. New x-ray source arrays have been developed and they are aimed at replacing the scanned x-ray tube for improved acquisition time and potentially for higher spatial resolution. The potential advantages and challenges of this approach are described. Combination of digital mammography and tomosynthesis in a single system places increased demands on certain functional aspects of the detector and overall performance, particularly in the tomosynthesis mode due to lower photon fluence per projection. This may require fast-frame acquisition and symmetric or asymmetric pixel binning in some systems. Recent studies investigated the performance of increased conversion layer thickness for contrast-enhanced imaging of the breast in dual-energy acquisition mode. In other direct conversion detectors operating in the avalanche mode, sensitivities close to the single photon response are also explored for mammography and breast tomosynthesis. The potential advantages and challenges of this approach are described. Dedicated breast CT brings x-ray imaging of the breast to true tomographic 3D imaging. It can eliminate the tissue superposition problem and does not require physical compression of the breast. Using cone beam geometry and a flat-panel detector, several hundred projections are acquired and reconstructed to near isotropic voxels. Multiplanar reconstruction facilitates viewing the breast volume in any desired orientation. Ongoing clinical studies, the current state-of-the art, and research to advance the technology are described. Learning Objectives: To understand the ongoing developments in x-ray imaging of the breast To understand the approaches and applications of spectral mammography To understand the potential advantages of distributed x-ray source arrays for digital breast tomosynthesis To understand the ongoing developments in detector technology for digital mammography and breast tomosynthesis To understand the current state-of-the-art for dedicated cone-beam breast CT and research to advance the technology. Research collaboration with Koning Corporation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Detector dose response in megavoltage small photon beams. II. Pencil beam perturbation effects

Purpose: To quantify detector perturbation effects in megavoltage small photon fields and support the theoretical explanation on the nature of quality correction factors in these conditions. Methods: In this second paper, a modern approach to radiation dosimetry is defined for any detector and applied to small photon fields. Fano’s theorem is adapted in the form of a cavity theory and applied in the context of nonstandard beams to express four main effects in the form of perturbation factors. The pencil-beam decomposition method is detailed and adapted to the calculation of perturbation factors and quality correction factors. The approach defines a perturbation function which, for a given field size or beam modulation, entirely determines these dosimetric factors. Monte Carlo calculations are performed in different cavity sizes for different detection materials, electron densities, and extracameral components. Results: Perturbation effects are detailed with calculated perturbation functions, showing the relative magnitude of the effects as well as the geometrical extent to which collimating or modulating the beam impacts the dosimetric factors. The existence of a perturbation zone around the detector cavity is demonstrated and the approach is discussed and linked to previous approaches in the literature to determine critical field sizes. Conclusions: Monte Carlo simulations are valuable to describe pencil beam perturbation effects and detail the nature of dosimetric factors in megavoltage small photon fields. In practice, it is shown that dosimetric factors could be avoided if the field size remains larger than the detector perturbation zone. However, given a detector and beam quality, a full account for the detector geometry is necessary to determine critical field sizes.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

SU-F-J-51: A Cone-Based Scintillator Detector for IGRT QA for Scattered and Scanning Proton Therapy

Purpose: IGRT commissioning and QA are critical components for precise delivery of proton treatment beams to patients. In order to ensure high quality IGRT, a new cone-based scintillator detector was evaluated for our QA activities for double-scattered and scanning proton modalities. This allows a routine evaluation of the gantry-angle dependent position offset between the radiation and imaging. Methods: The cone-based scintillator detector (XRV-124, Logos Systems, Int’l CA, USA) features a unique configuration of measuring stereotactic paths of proton and x-ray beams in a single setup with arbitrary gantry angles. For the beams-eye-view (BEV) analysis of x-ray crosshair images, a cylindrical representation of the cone image was newly developed. The calibration accuracy was evaluated using different CT resolutions for a range of 55 – 95mm in patient’s cranial direction and ±9mm in the lateral direction. Energy-dependent spot sizes (σ) of pencil beams were characterized and compared to measurements by the MatriXX detector (IBA, Germany). Iso-centric deviations between radiation and x-ray imaging were characterized as a function of gantry angle. Results: The position calibration of the detector was successfully verified with a reproducible positioning by x-ray imaging. The measurements were reproducible within clinical tolerances (±1mm). The spot size vs. energy at zero gantry angle measured with the scintillating cone detector agreed with the MatriXX detector measurements within 17%. Conclusion: The new approach to investigate the accuracy of IGRT and pencil beam properties could successfully be implemented into the QA program. The system will improve efficiency in our QA activities for proton treatments.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-T-473: Evaluation of Off-Axis And Peripheral Dose Using Different Detectors

Purpose: In radiation therapy, measurement of off-axis and peripheral dose is a tedious task. The dose distribution along the beam central axis give only part of the information required for an accurate dose description inside the patient. Dose distributions in 2-D and 3-D are determined with central axis data in conjunction with off-axis dose profiles. Combining a central axis dose distribution with off-axis data results in volume dose matrix that provides 2-D and 3-D information on dose distribution. By considering the importance of these two parameters this study investigates and compares the off axis and peripheral dose measurement using Ionization chamber, MOSFET, Radiochromic film and EDR2 film. Methods: In the measurement of off-axis and peripheral doses 0.6cc farmer type chamber, EDR-2 film, MD-55 radiochromic film and MOSFET detectors were used for both 6MV and 15MV beams. The off-axis and peripheral dose was measured at every 1 cm interval by changing the position of the couch without disturbing the other experimental setup in particular, the phantom with detector position. Results: Readings were obtained for both 6MV and 15MV photon beams at SSD technique for various field size using MOSFET, Ionization chamber and Radiochromic film. The results shows the percentage difference between various detectors for various field sizes. For Peripheral dose measurement were taken from the edge of the field size and for off axis it is measured form central axis dose. Conclusion: In conclusion, our study shows that no detector is ideal and only a comparison between different detectors highlights the weaknesses of each detector. MOSFET provides adequate dose assessment in off-axis and peripheral regions in 6MV and 15MV photon beams. Film dosimetry in general a convenient method to generate one- and two-dimensional dose distributions. The result of this indicates that MOSFET is flexible tool for relative dosimetry as films.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2016

SU-F-T-557: Evaluation of Detector Response in Rectangular Small Field Dosimetry

Purpose: As stereotactic treatment modalities grow towards becoming the standard of care, the need for accurate dose computation in small fields is becoming increasingly essential. The purpose of this study is to evaluate the response of different detectors, intended for small field dosimetry, in jaw defined small rectangular fields by analyzing output factors from a stereotactic clinical accelerator. Methods: Two Dosimeters, the Exradin A26 Microionization Chamber (Standard Imaging) and Edge Diode Detector (Sun Nuclear) were used to measure output factors taken on the Varian Edge Stereotactic Linear accelerator. Measurements were taken at 6MV and 6FFF at 10cm depth, 100cm SSD in a 48×48×40cm3 Welhoffer BluePhantom2 (IBA) with X and Y jaws set from 0.6 to 2.0cm. Output factors were normalized to a 5×5cm2 machine-specific reference field. Measurements were made in the vertical orientation for the A26 and horizontal orientation for both the A26 and Edge. Output factors were measured as: OF{sub FS} = M{sub FS}/M{sub ref} where M{sub FS} and M{sub ref} are the measured signals for the clinical field and the reference field, respectively. Measured output factors were then analyzed to establish relative responses of the detectors in small fields. Results: At 6MV the Edge detector exhibited a variation in output factors dependent on jaw positioning (X-by-Y vs Y-by-X) of 5.7% of the 5×5cm reference output and a variation of 3.33% at 6FFF. The A26 exhibited variation of output factor dependent on jaw positioning of upto 7.7% of the 5×5cm reference field at 6MV and upto 5.33% at 6FFF. Conclusion: Both the Edge detector and A26 responded as expected at small fields however a dependence on the jaw positioning was noted. At 6MV and 6FFF the detector response showed an increased dependence on the positioning of the X jaws as compared to the positioning of the Y jaws.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TU-H-CAMPUS-TeP2-03: High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

Purpose: Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research. Methods: We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has green output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1×1mm2 to 5×5mm2 were used for detector characteristics comparison. Results: The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5×5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1×1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples. Conclusion: The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based microdetectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Alignment of the ATLAS Inner Detector in Run 2

The performance of the ATLAS Inner Detector alignment has been studied using pp collision data at s√=13TeV collected by the ATLAS experiment during Run 2 (2015–2018) of the Large Hadron Collider (LHC). The goal of the detector alignment is to determine the detector geometry as accurately as possible and correct for time-dependent movements. The Inner Detector alignment is based on the minimization of track-hit residuals in a sequence of hierarchical levels, from global mechanical assembly structures to local sensors. Subsequent levels have increasing numbers of degrees of freedom; in total there are almost 750,000. The alignment determines detector geometry on both short and long timescales, where short timescales describe movements within an LHC fill. The performance and possible track parameter biases originating from systematic detector deformations are evaluated. Momentum biases are studied using resonances decaying to muons or to electrons. The residual sagitta bias and momentum scale bias after alignment are reduced to less than ~0.1 TeV -1 and 0.9×10 -3 , respectively. Impact parameter biases are also evaluated using tracks within jets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

The NEXT-100 Detector

The NEXT collaboration is dedicated to the study of double beta decays of 136 Xe using a high-pressure gas electroluminescent time projection chamber. This advanced technology combines exceptional energy resolution (≤ 1% FWHM at the Q ββ value of the neutrinoless double beta decay) and powerful topological event discrimination. Building on the achievements of the NEXT-White detector, the NEXT-100 detector started taking data at the Laboratorio Subterráneo de Canfranc (LSC) in May of 2024. Designed to operate with xenon gas at 13.5 bar, NEXT-100 consists of a time projection chamber where the energy and the spatial pattern of the ionising particles in the detector are precisely retrieved using two sensor planes (one with photo-multiplier tubes and the other with silicon photo-multipliers). The detector has been operating at stable conditions using argon and xenon gases at ~4 bar and drift fields of 74 V cm –1 and 118 V cm –1 , respectively. Alpha decays from the 222 Rn chain have been used to test and monitor the stability of the detector, showing a constant electron lifetime in the drift volume. In this paper, in addition to reporting the results of the commissioning run, we provide a detailed description of the NEXT-100 detector, describe its assembly, and present the current estimation of the radiopurity budget.

Adams, C. [Argonne National Laboratory; NVIDIA] (O↗
DOE OSTI2016

Conceptual design studies for a CEPC detector

The physics potential of the Circular Electron Positron Collider (CEPC) can be significantly strengthened by two detectors with complementary designs. A promising detector approach based on the Silicon Detector (SiD) designed for the International Linear Collider (ILC) is presented. Several simplifications of this detector for the lower energies expected at the CEPC are proposed. A number of cost optimizations of this detector are illustrated using full detector simulations. We show that the proposed changes will enable one to reach the physics goals at the CEPC.

CEPC↗
DOE OSTI2013

The Era of Kilometer-Scale Neutrino Detectors

Neutrino astronomy beyond the Sun was first imagined in the late 1950s; by the 1970s, it was realized that kilometer-scale neutrino detectors were required. The first such instrument, IceCube, transforms a cubic kilometer of deep and ultra-transparent Antarctic ice into a particle detector. KM3NeT, an instrument that aims to exploit several cubic kilometers of the deep Mediterranean sea as its detector medium, is in its final design stages. The scientific missions of these instruments include searching for sources of cosmic rays and for dark matter, observing Galactic supernova explosions, and studying the neutrinos themselves. Identifying the accelerators that produce Galactic and extragalactic cosmic rays has been a priority mission of several generations of high-energy gamma-ray and neutrino telescopes; success has been elusive so far. Detecting the gamma-ray and neutrino fluxes associated with cosmic rays reaches a new watershed with the completion of IceCube, the first neutrino detector with sensitivity to the anticipated fluxes. In this paper, we will first revisit the rationale for constructing kilometer-scale neutrino detectors. We will subsequently recall the methods for determining the arrival direction, energy and flavor of neutrinos, and will subsequently describe the architecture of the IceCube and KM3NeT detectors.

Halzen, Francis↗
DOE OSTI2017

Design of Faraday cup ion detectors built by thin film deposition

Thin film Faraday cup detectors can provide measurements of fast ion loss from magnetically confined fusion plasmas. These multilayer detectors can resolve the energy distribution of the lost ions in addition to giving the total loss rate. Prior detectors were assembled from discrete foils and insulating sheets. Outlined here is a design methodology for creating detectors using thin film deposition that are suited to particular scientific goals. The intention is to use detectors created by this method on JET and NSTX-U. The detectors will consist of alternating layers of aluminum and silicon dioxide, with layer thicknesses chosen to isolate energies of interest. Thin film deposition offers the advantage of relatively simple and more mechanically robust construction compared to other methods, as well as allowing precise control of film thickness. Furthermore, this depositional fabrication technique places the layers in intimate thermal contact, providing for three-dimensional conduction and dissipation of the ion-produced heating in the layers, rather than the essentially two-dimensional heat conduction in the discrete foil stack implementation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Optimization of the angular orientation for a fast ion loss detector in a tokamak

A scintillator type fast ion loss detector measures the gyroradius and pitch angle distribution of superthermal ions escaping from a magnetically confined fusion plasma at a single location. Described here is a technique for optimizing the angular orientation of such a detector in an axisymmetric tokamak geometry in order to intercept losses over a useful and interesting ranges of pitch angle. The method consists of evaluating the detector acceptance as a function of the fast ion constants of motion, i.e. energy, canonical toroidal momentum, and magnetic moment. The detector acceptance can then be plotted in a plane of constant energy and compared with the relevant orbit class boundaries and fast ion source distributions. Knowledge of expected or interesting mechanisms of loss can further guide selection of the detector orientation. The example of a fast ion loss detector for the National Spherical Torus Experiment-Upgrade (NSTX-U) is considered.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Reduction in radioactivity-induced backgrounds using a novel active veto detector for rare event search experiments

The results of a newly developed annular cryogenic phonon-mediated active veto detector are discussed which shows a significant reduction of radioactivity-induced backgrounds in rare event search experiments. The veto detector is made up of germanium weighing ∼500 g with an outer diameter of 76 mm and an inner diameter of 28 mm. The detector can host a 25 mm diameter germanium inner target detector of mass ∼10 g. A GEANT4 simulation with the active veto and inner target detector shows a gamma background reduction of 50 - 80% which is further improved (> 90%) with 4pi veto coverage. Experimental measurements with the detector assembly agree well with the simulation.

Chaudhuri, Mouli↗
DOE OSTI2013

Application of Subspace Detectors to 2012 Sumatera Earthquake Sequence

In this report the aftershock sequence of the 2012 Sumatra earthquake is used to study the performance of subspace detectors (Harris, 2006) to detect and classify the events. The ground truth used for this study is 1222 aftershock solutions from the LLNL database drawn mostly from the Reviewed Event Bulletin (REB). Subspace detectors are built using several spawning strategies with waveforms recorded by the Makanchi Array (MKAR). Because we desire the subspace detectors to have a very low false alarm rate, the subspace templates are required to be about 50 seconds long (most of the P-bundle). For the same reason, the power detections used to create the subspace templates are restricted to have high SNR. Because of these restrictions, none of the subspace detectors are able to reproduce the entire ground truth catalog. They do have a very low false alarm rate, however, and so can reliably be used as single-array detection classifiers. Because of their reliability, in a suitably designed system, these detectors could be used to segregate detections from regions of high seismicity such as aftershock sequences, and allow processing of those detections in isolation from routine seismicity. It may also be possible to use these detectors to process groups of detections simultaneously. This leads to the concept of “analyst workload reduction factor”; a measure of the reduction in effort achieved by processing N detections in M groups instead of individually. If M is much smaller than N, a significant reduction factor is achieved.

58 GEOSCIENCES↗
DOE OSTI2013

Detector Simulation and WIMP Search Analysis for the Cryogenic Dark Matter Search Experiment

Astrophysical and cosmological measurements on the scales of galaxies, galaxy clusters, and the universe indicate that 85% of the matter in the universe is composed of dark matter, made up of non-baryonic particles that interact with cross-sections on the weak scale or lower. Hypothetical Weakly Interacting Massive Particles, or WIMPs, represent a potential solution to the dark matter problem, and naturally arise in certain Standard Model extensions. The Cryogenic Dark Matter Search (CDMS) collaboration aims to detect the scattering of WIMP particles from nuclei in terrestrial detectors. Germanium and silicon particle detectors are deployed in the Soudan Underground Laboratory in Minnesota. These detectors are instrumented with phonon and ionization sensors, which allows for discrimination against electromagnetic backgrounds, which strike the detector at rates orders of magnitude higher than the expected WIMP signal. This dissertation presents the development of numerical models of the physics of the CDMS detectors, implemented in a computational package collectively known as the CDMS Detector Monte Carlo (DMC). After substantial validation of the models against data, the DMC is used to investigate potential backgrounds to the next iteration of the CDMS experiment, known as SuperCDMS. Finally, an investigation of using the DMC in a reverse Monte Carlo analysis of WIMP search data is presented.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

GADRAS Detector Response Function.

The Gamma Detector Response and Analysis Software (GADRAS) applies a Detector Response Function (DRF) to compute the output of gamma-ray and neutron detectors when they are exposed to radiation sources. The DRF is fundamental to the ability to perform forward calculations (i.e., computation of the response of a detector to a known source), as well as the ability to analyze spectra to deduce the types and quantities of radioactive material to which the detectors are exposed. This document describes how gamma-ray spectra are computed and the significance of response function parameters that define characteristics of particular detectors.

Mitchell, Dean J.↗
DOE OSTI2015

Computer simulation of the CSPAD, ePix10k, and RayonixMX170HS X-ray detectors

The invention of free-electron lasers (FELs) has opened a door to an entirely new level of scientific research. The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory is an X-ray FEL that houses several instruments, each with its own unique X-ray applications. This light source is revolutionary in that while its properties allow for a whole new range of scientific opportunities, it also poses numerous challenges. For example, the intensity of a focused X-ray beam is enough to damage a sample in one mere pulse; however, the pulse speed and extreme brightness of the source together are enough to obtain enough information about that sample, so that no further measurements are necessary. An important device in the radiation detection process, particularly for X-ray imaging, is the detector. The power of the LCLS X-rays has instigated a need for better performing detectors. The research conducted for this project consisted of the study of X-ray detectors to imitate their behaviors in a computer program. The analysis of the Rayonix MX170-HS, CSPAD, and ePix10k in particular helped to understand their properties. This program simulated the interaction of X-ray photons with these detectors to discern the patterns of their responses. A scientist’s selection process of a detector for a specific experiment is simplified from the characterization of the detectors in the program.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

CHerenkov detectors In mine PitS (CHIPS) Letter of Intent to FNAL

This Letter of Intent outlines a proposal to build a large, yet cost-effective, 100 kton fiducial mass water Cherenkov detector that will initially run in the NuMI beam line. The CHIPS detector (CHerenkov detector In Mine PitS) will be deployed in a flooded mine pit, removing the necessity and expense of a substantial external structure capable of supporting a large detector mass. There are a number of mine pits in northern Minnesota along the NuMI beam that could be used to deploy such a detector. In particular, the Wentworth Pit 2W is at the ideal off-axis angle to contribute to the measurement of the CP violating phase. The detector is designed so that it can be moved to a mine pit in the LBNE beam line once that becomes operational.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗