Astrophysics and Astronomy Commons^™

The Energetic Particle Detector (Epd) Investigation And The Energetic Ion Spectrometer (Eis) For The Magnetospheric Multiscale (Mms) Mission, B. H. Mauk, J. B. Blake, D. N. Baker, J. H. Clemmons, Geoffrey Reeves, Harlan E. Spence, S. E. Jaskulek, C. E. Schlemm, L. E. Brown, Steve Cooper, J. V. Craft, J. F. Fennell, R. S. Gurnee, C. M. Hammock, J. R. Hayes, P. A. Hill, G. C. Ho, J. C. Hutcheson, A. D. Jacques, S. Kerem, D. G. Mitchell, K. S. Nelson, N. P. Paschalidis, E. Rossano, M. R. Stokes, J. H. Westlake

Space Science Center

Abstract

The Energetic Particle Detector (EPD) Investigation is one of 5 fields-and-particles investigations on the Magnetospheric Multiscale (MMS) mission. MMS comprises 4 spacecraft flying in close formation in highly elliptical, near-Earth-equatorial orbits targeting understanding of the fundamental physics of the important physical process called magnetic reconnection using Earth’s magnetosphere as a plasma laboratory. EPD comprises two sensor types, the Energetic Ion Spectrometer (EIS) with one instrument on each of the 4 spacecraft, and the Fly’s Eye Energetic Particle Spectrometer (FEEPS) with 2 instruments on each of the 4 spacecraft. EIS measures energetic ion energy, angle and elemental compositional distributions from …

Plans For The Next Grape Balloon Flight, Mark L. Mcconnell, Peter F. Bloser, T P. Connor, Camden Ertley, Jason S. Legere, James M. Ryan, Sambid K. Wasti

Space Science Center

The Gamma RAy Polarimeter Experiment (GRAPE) was first flown on a 26-hour balloon flight in the fall of 2011. GRAPE consists of an array of Compton polarimeter modules (based on traditional scintillation technologies) designed to operate in the energy range from 50 keV up to 500 keV. The ultimate goal is to operate GRAPE in a wide FoV configuration for the study of gamma-ray bursts. For the first (demonstration) balloon flight, GRAPE was configured in a collimated mode to facilitate observations of known point sources. The Crab nebula/pulsar, the active Sun, and Cygnus X-1 were the primary targets for the …

Scintillator Gamma-Ray Detectors With Silicon Photomultiplier Readouts For High-Energy Astronomy, Peter F. Bloser, Jason S. Legere, Chris Bancroft, Mark L. Mcconnell, James M. Ryan, Nathan Schwadron

Space Science Center

Space-based gamma-ray detectors for high-energy astronomy face strict constraints of mass, volume, and power, and must endure harsh operating environments. Scintillator materials have a long history of successful operation under these conditions, and new materials offer greatly improved performance in terms of efficiency, time response, and energy resolution. The use of scintillators in space remains constrained, however, by the mass, volume, and fragility of the associated light readout device, typically a vacuum photomultiplier tube (PMT). Recently developed silicon photomultipliers (SiPMs) offer gains and efficiencies similar to those of PMTs, but with greatly reduced mass and volume, high ruggedness, and no …

An Imaging Neutron/Gamma-Ray Spectrometer, Amanda C. Madden, Peter F. Bloser, Dominique Fourguette, Liane Larocque, Matt Lewis, Jason S. Legere, Mark L. Mcconnell, Marissa Rouseau, James M. Ryan

Space Science Center

We present the test results of a neutron/gamma-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. The simultaneous detection of neutrons and gamma rays is a clear indication of the presence of fissile material. The instrument works as a double-scatter telescope, requiring a neutron or gamma ray to undergo an interaction in two detectors to be considered a valid event. While …

An Imaging Neutron/Gamma-Ray Spectrometer, James M. Ryan, Chris Bancroft, Peter F. Bloser, Dominique Fourguette, Liane Larocque, Jason S. Legere, Amanda C. Madden, Mark L. Mcconnell, Jane Pavlich, Greg Ritter, Greg Wassick, Marissa Rouseau

Space Science Center

We present the design and development of a dual-species, neutron/γ-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials (SNM). Real-time detection and identification is important for locating fissile materials. These materials, specifically uranium and plutonium, emit neutrons and γ rays via spontaneous or induced fission. Co-located neutron and γ-ray emissions are a sure sign of fissile material, requiring very few spatially correlated events for a significant detection. Our instrument design detects neutrons and γ rays from all sources in its field of view, constructs images of the emission pattern, and reports the spectra for both …

Development Of A Telescope For Medium-Energy Gamma-Ray Astronomy, Stanley D. Hunter, Peter F. Bloser, Michael P. Dion, Georgia A. Denolfo, Jason S. Legere, Mark L. Mcconnell, Suzanne F. Nowicki, James M. Ryan, Seunghee Son, Floyd Stecker

Space Science Center

The Advanced Energetic Pair Telescope (AdEPT) is being developed at GSFC as a future NASA MIDEX mission to explore the medium-energy (5–200 MeV) gamma-ray range. The enabling technology for AdEPT is the Three- Dimensional Track Imager (3-DTI), a gaseous time projection chamber. The high spatial resolution 3-D electron tracking of 3-DTI enables AdEPT to achieve high angular resolution gamma-ray imaging via pair production and triplet production (pair production on electrons) in the medium-energy range. The low density and high spatial resolution of 3-DTI allows the electron positron track directions to be measured before they are dominated by Coulomb scattering. Further, …

A Portable Neutron Spectroscope (Nspect) For Detection, Imaging And Identification Of Nuclear Material, James M. Ryan, Chris Bancroft, Peter F. Bloser, U Bravar, Dominique Fourguette, Colin Frost, Liane Larocque, Mark L. Mcconnell, Jason S. Legere, Jane Pavlich, Greg Ritter, Greg Wassick, Joshua Wood, R S. Woolf

Space Science Center

We have developed, fabricated and tested a prototype imaging neutron spectrometer designed for real-time neutron source location and identification. Real-time detection and identification is important for locating materials. These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike other forms of radiation (e.g. gamma rays), penetrating neutron emission is very uncommon. The instrument detects these neutrons, constructs images of the emission pattern, and reports the neutron spectrum. The device will be useful for security and proliferation deterrence, as well as for nuclear waste characterization and monitoring. The instrument is optimized for imaging and spectroscopy in the …

Simulations Of A Monolithic Lanthanum Bromide Gamma-Ray Detector, Camden Ertley, Chris Bancroft, Peter F. Bloser, Taylor Connor, Jason S. Legere, Mark L. Mcconnell, James M. Ryan

Space Science Center

We have been working on the development of a detector design for a large area coded aperture imaging system operating in the 10-600 keV energy range. The detector design is based on an array of Lanthanum Bromide (LaBr₃) scintillators, each directly coupled to a Hamamatsu 64-channel multi-anode photomultiplier tube (MAPMT). This paper focuses on the development of the GEANT4-based simulations as an aid in the optimization of the detector design. The simulations have been validated by comparisons with various laboratory data sets. We will summarize the current status and latest findings from this study.

Plans For The First Balloon Flight Of The Gamma-Ray Polarimeter Experiment (Grape), Taylor Connor, Chris Bancroft, Peter F. Bloser, Jason S. Legere, Mark L. Mcconnell, James M. Ryan

Space Science Center

We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), has been successfully demonstrated in the lab using partially polarized gamma-ray sources and using fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model, consisting of a single detector module, was flown on a high altitude balloon flight to further demonstrate the design and to collect background data. We are currently preparing a much larger balloon payload for a flight in the fall of 2011. …

A Fast Scintillator Compton Telescope For Medium-Energy Gamma-Ray Astronomy, Peter F. Bloser, James M. Ryan, Jason S. Legere, Manuel Julien, Chris Bancroft, Mark L. Mcconnell, Mark Wallace, R M. Kippen, Shawn Tornga

Space Science Center

The field of medium-energy gamma-ray astronomy urgently needs a new mission to build on the success of the COMPTEL instrument on the Compton Gamma Ray Observatory. This mission must achieve sensitivity significantly greater than that of COMPTEL in order to advance the science of relativistic particle accelerators, nuclear astrophysics, and diffuse backgrounds, and bridge the gap between current and future hard X-ray missions and the high-energy Fermi mission. Such an increase in sensitivity can only come about via a dramatic decrease in the instrumental background. We are currently developing a concept for a low-background Compton telescope that employs modern scintillator …

Development Of The Advance Energetic Pair Telescope (Adept) For Medium-Energy Gamma-Ray Astronomy, Stanley D. Hunter, Peter F. Bloser, Michael P. Dion, Mark L. Mcconnell, Georgia A. Denolfo, Seunghee Son, James M. Ryan, Floyd Stecker

Space Science Center

Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (~0.3< E_γ < ~200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, mediumenergy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30×30×30 cm³ prototype of the AdEPT instrument.

Advanced Characterization And Simulation Of Sonne: A Fast Neutron Spectrometer For Solar Probe Plus, R S. Woolf, James M. Ryan, Peter F. Bloser, U Bravar, E O. Fluckiger, Jason S. Legere, A L. Mackinnon, Procheta Mallik, Mark L. Mcconnell, B Pirard

Space Science Center

SONNE, the SOlar NeutroN Experiment proposed for Solar Probe Plus, is designed to measure solar neutrons from 1-20 MeV and solar gammas from 0.5-10 MeV. SONNE is a double scatter instrument that employs imaging to maximize its signal-to-noise ratio by rejecting neutral particles from non-solar directions. Under the assumption of quiescent or episodic small-flare activity, one can constrain the energy content and power dissipation by fast ions in the low corona. Although the spectrum of protons and ions produced by nanoflaring activity is unknown, we estimate the signal in neutrons and γ−rays that would be present within thirty solar radii, …

Grape: A Balloon-Borne Gamma-Ray Polarimeter, Mark L. Mcconnell, Chris Bancroft, Peter F. Bloser, Taylor Connor, Jason S. Legere, James M. Ryan

Space Science Center

The Gamma-RAy Polarimeter Experiment (GRAPE) is a concept for an astronomical hard X-ray Compton polarimeter operating in the 50 - 500 keV energy band. The instrument has been optimized for wide-field polarization measurements of transient outbursts from energetic astrophysical objects such as gamma-ray bursts and solar flares. The GRAPE instrument is composed of identical modules, each of which consists of an array of scintillator elements read out by a multi-anode photomultiplier tube (MAPMT). Incident photons Compton scatter in plastic scintillator elements and are subsequently absorbed in inorganic scintillator elements; a net polarization signal is revealed by a characteristic asymmetry in …

A New Low-Background Compton Telescope Using Labr3 Scintillator, Peter F. Bloser, James M. Ryan, Jason S. Legere, Manuel Julien, Chris Bancroft, Mark L. Mcconnell, Mark Wallace, R M. Kippen, Shawn Tornga

Space Science Center

Gamma-ray astronomy in the MeV range suffers from weak fluxes from sources and high background in the nuclear energy range. The background comes primarily from neutron-induced gamma rays, with the neutrons being produced by cosmic-ray interactions in the Earth's atmosphere, the spacecraft, and the instrument. Compton telescope designs often suppress this background by requiring coincidences in multiple detectors and a narrow time-of-flight (ToF) acceptance window. The COMPTEL experience on the Compton Gamma Ray Observatory shows that a 1.9-ns ToF resolution is insufficiently narrow to achieve the required low background count rate. Furthermore, neutron interactions in the detectors themselves generate an …

A Compton Telescope For Remote Location And Identification Of Radioactive Material, Peter F. Bloser, Jason S. Legere, Shirley M. Dame, Mark L. Mcconnell, U Bravar, James M. Ryan

Space Science Center

The spare detectors from NASA's Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of gamma radiation. The gamma-ray experimental telescope assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 95 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of-flight for each coincident detection and compiles histograms of total energy and incident angle as computed using the kinematics of Compton scattering. GRETA's field of view is …

Statistical Properties Of Gamma‐Ray Burst Polarization, Kenji Toma, Takanori Sakamoto, Bing Zhang, J E. Hill, Mark L. Mcconnell, Peter F. Bloser, Ryo Yamazaki, Kunihito Ioka, Takashi Nakamura

Space Science Center

The emission mechanism and the origin and structure of magnetic fields in gamma‐ray burst (GRB) jets are among the most important open questions concerning the nature of the central engine of GRBs. In spite of extensive observational efforts, these questions remain to be answered and are difficult or even impossible to infer with the spectral and lightcurve information currently collected. Polarization measurements will lead to unambiguous answers to several of these questions. Recent developments in X‐ray and γ‐ray polarimetry techniques have demonstrated a significant increase in sensitivity enabling several new mission concepts, e.g. POET (Polarimeters for Energetic Transients), providing wide …

Grb Polarimetry With Poet, Mark L. Mcconnell, L Angelini, Matthew Baring, Scott Barthelmy, J Kevin Black, Peter F. Bloser, B Dennis, A G. Emslie, J Greiner, W Hajdas, A K. Harding, H Hartmann, J E. Hill, Kunihito Ioka, Philip Kaaret, G Kanbach, D Kniffen, Jason S. Legere, John R. Macri, R Morris, Takashi Nakamura, N Produit, James M. Ryan, Takanori Sakamoto, Kenji Toma, X Wu, Ryo Yamazaki, Bing Zhang

Space Science Center

POET (Polarimeters for Energetic Transients) represents a concept for a Small Explorer (SMEX) satellite mission, whose principal scientific goal is to understand the structure of GRB sources through sensitive X‐ray and γ‐ray polarization measurements. The payload consists of two wide field‐of‐view (FoV) instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2–15 keV and a high energy polarimeter (Gamma‐Ray Polarimeter Experiment or GRAPE) that would measure polarization in the 60–500 keV energy range. The POET spacecraft provides a zenith‐pointed platform for maximizing the exposure to deep space. Spacecraft rotation provides a means of effectively …

A Compton Telescope For Remote Location And Identification Of Radioactive Material, James M. Ryan, Justin Baker, John R. Macri, Mark L. Mcconnell, Richard Carande

Space Science Center

The spare detectors from NASA Compton Gamma-Ray Observatory COMPTEL instrument have been reconfigured to demonstrate the capability at ground level to remotely locate and identify sources of g radiation or the movement of material that might shield γ-ray sources. The Gamma-Ray Experimental Telescope Assembly (GRETA) employs two 28 cm diameter scintillation detectors separated by 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick NaI(Tl) detector. The assembly electronics and real-time data acquisition system measures the energy deposits and time-of- flight for each coincident detection and compiles histograms of total energy and incident angle as computed …

Development And Performance Of The Fast Neutron Imaging Telescope For Snm Detection, James M. Ryan, U Bravar, E O. Fluckiger, John R. Macri, Mark L. Mcconnell, B Pirard, R S. Woolf

Space Science Center

FNIT (the Fast Neutron Imaging Telescope), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the range 0.8-20 MeV, was initially conceived to study solar neutrons as a candidate design for the Inner Heliosphere Sentinel (IHS) spacecraft of NASA's Solar Sentinels program and successively reconfigured to locate fission neutron sources. By accurately identifying the position of the source with imaging techniques and reconstructing the Watt spectrum of fission neutrons, FNIT can detect samples of special nuclear material (SNM), including heavily shielded and masked ones. The detection principle is based on multiple elastic neutron-proton scatterings in organic …

Poet: Polarimeters For Energetic Transients, J E. Hill, Mark L. Mcconnell, Peter F. Bloser, Jason S. Legere, John R. Macri, James M. Ryan, Scott Barthelmy, L Angelini, Takanori Sakamoto, J Kevin Black, H Hartmann, Philip Kaaret, Bing Zhang, Kunihito Ioka, Takashi Nakamura, Kenji Toma, Ryo Yamazaki, X Wu

Space Science Center

POET (Polarimeters for Energetic Transients) is a Small Explorer mission concept proposed to NASA in January 2008. The principal scientific goal of POET is to measure GRB polarization between 2 and 500 keV. The payload consists of two wide FoV instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2–15 keV and a high energy polarimeter (Gamma‐Ray Polarimeter Experiment—GRAPE) that will measure polarization in the 60–500 keV energy range. Spectra will be measured from 2 keV up to 1 MeV. The POET spacecraft provides a zenith‐pointed platform for maximizing the exposure to deep space. …

Design Optimization And Performance Capabilities Of The Fast Neutron Imaging Telescope (Fnit), U Bravar, P J. Bruillard, E O. Fluckiger, Jason S. Legere, John R. Macri, A L. Mackinnon, Procheta Mallik, Mark L. Mcconnell, M R. Moser, B Pirard, James M. Ryan, R S. Woolf

Space Science Center

We describe the design optimization process and performance characterization of a next generation neutron telescope, with imaging and energy measurement capabilities, sensitive to neutrons in the 1-20 MeV energy range. The response of the Fast Neutron Imaging Telescope (FNIT), its efficiency in neutron detection, energy resolution and imaging capabilities were characterized through a combination of lab tests and Monte Carlo simulations. Monte Carlo simulations, together with experimental data, are also being used in the development and testing of the image reconstruction algorithm. FNIT was initially conceived to study solar neutrons as a candidate instrument for the Inner Heliosphere Sentinel (IHS) …

Using Lax Scintillator In A New Low-Background Compton Telescope, James M. Ryan, Peter F. Bloser, John R. Macri, Mark L. Mcconnell

Space Science Center

The ability of Compton telescopes to perform imaging and spectroscopy in space depends directly on the speed and energy resolution of the calorimeter detectors in the telescope. The calorimeter detectors flown on space-borne or balloon-borne Compton telescopes have included NaI(Tl), CsI(Na), HPGe and liquid organic scintillator. By employing LaX scintillators for the calorimeter, one can take advantage of the unique speed and resolving power of the material to improve the instrument sensitivity and simultaneously enhance its spectroscopic performance and thus its imaging performance. We present a concept for a space-borne Compton telescope that employs LaX as a calorimeter and estimate …

A Burst Chasing X-Ray Polarimeter, Joanne E. Hill, Scott Barthelmy, J Kevin Black, Philip Deines-Jones, Keith Jahoda, Takanori Sakamoto, Philip Kaaret, Mark L. Mcconnell, Peter F. Bloser, John R. Macri, Jason S. Legere, James M. Ryan, Billy R. Smith Jr, Bing Zhang

Space Science Center

Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of …

Characterization Of Single-Sided Charge-Sharing Czt Strip Detectors For Gamma-Ray Astronomy, B Donmez, John R. Macri, James M. Ryan, Jason S. Legere, Mark L. Mcconnell, Mark Widholm, T Narita, L A. Hamel

Space Science Center

We report progress in the study of thick single-sided charge-sharing cadmium zinc telluride (CZT) strip detector modules designed to perform spectroscopy and 3-D imaging of gamma-rays. We report laboratory measurements including spectroscopy, efficiency and 3-D imaging capability of prototype detectors (15 × 15 × 7.5mm³) with 11×11 unit cells. We also report on Monte Carlo simulations (GEANT4 v7.1) to investigate the effect of multihits on detector performance in both spectroscopy and imaging. We compare simulation results with data obtained from laboratory measurements and discuss the implications for future strip detector designs.

The Advanced Compton Telescope, S E. Boggs, J Kurfess, James M. Ryan, Elena Aprile, Neil Gehrels, R M. Kippen, Marc Leising, U Oberlack, Cornelia B. Wunderer, Allen Zych, Peter F. Bloser, M Harris, A Hoover, Alexei Klimenk, Dan Kocevski, Mark L. Mcconnell, Peter Milne, E I. Novikova, B F. Phlips, Mark Polsen, Steven Sturner, Derek Tournear, G Weidenspointer, Eric Wulf, A Zoglauer, Matthew Baring, John Beacom, Lars Bildsten, Charles Dermer, Dieter H. Hartman, Margarita Hernanz, David Smith, Sumner Starrfield

Space Science Center

The Advanced Compton Telescope (ACT), the next major step in gamma-ray astronomy, will probe the fires where chemical elements are formed by enabling high-resolution spectroscopy of nuclear emission from supernova explosions. During the past two years, our collaboration has been undertaking a NASA mission concept study for ACT. This study was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We present the results of this study, including scientific goals and expected performance, mission design, …

Fnit: The Fast Neutron Imaging Telescope For Snm Detection, U Bravar, P J. Bruillard, E O. Fluckiger, John R. Macri, Mark L. Mcconnell, M R. Moser, James M. Ryan

Space Science Center

We report on recent progress in the development of the Fast Neutron Imaging Telescope (FNIT), a detector with both imaging and energy measurement capabilities, sensitive to neutrons in the 2-20 MeV range. FNIT was initially conceived to study solar neutrons as a candidate design for the Solar Sentinels program under formulation at NASA. This instrument is now being configured to locate fission neutron sources for homeland security purposes. By accurately identifying the position of the neutron source with imaging techniques and reconstructing the energy spectrum of fission neutrons, FNIT can locate problematic amounts of Special Nuclear Material (SNM), including heavily …

The Caster Black Hole Finder Probe, Mark L. Mcconnell, Peter F. Bloser, G L. Case, M L. Cherry, J Cravens, T G. Guzik, K Hurley, R M. Kippen, John R. Macri, R S. Miller, W Paciesas, James M. Ryan, B Schaefer, J G. Stacy, W T. Vestrand, J P. Wefel

Space Science Center

The primary scientific mission of the Black Hole Finder Probe (BHFP), part of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X‐ray coded‐aperture imaging mission operating in the 10–600 keV energy band. The development of new inorganic scintillator materials provides improved performance that is well suited to the BHFP science requirements. Detection planes formed with these materials coupled with a new generation of readout devices represent a major advancement in the performance capabilities of scintillator‐based gamma …

Simulated Performance Of 3-Dti Gamma-Ray Telescope Concepts, Peter F. Bloser, Mark L. Mcconnell, James M. Ryan, Louis M. Barbier, Alan Centa, Stanley D. Hunter, John F. Krizmanic, Jason T. Link, Geoergia A. De Nolfo, Seunghee Son

Space Science Center

We present Monte Carlo simulations of two astronomical gamma-ray telescope concepts based on the ThreeDimensional Track Imager (3- DTI) detector. The 3-DTI consists of a time projection chamber with two-dimensional, crossedstrip micro-well detector readout. The full three- dimensional reconstruction of charged-particle tracks in the gas volume is obtained from transient digitizers, which record the time signature of the charge collected in the wells of each strip. Such detectors hold great promise for advanced Compton telescope (ACT) and advanced pair telescope (APT) concepts due to the very precise measurement of charged particle momenta that is possible (Compton recoil electrons and electron-positron …

Prospects For Grb Polarimetry With Grape, Mark L. Mcconnell, Peter F. Bloser, Jason S. Legere, John R. Macri, T Narita, James M. Ryan

Space Science Center

This paper discusses the latest progress in the development of GRAPE (Gamma‐Ray Polarimeter Experiment), a hard X‐ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X‐rays in the 50–300 keV energy range. We are particularly interested in X‐rays that are emitted from solar flares and gamma‐ray bursts (GRBs). Accurately measuring the polarization of the emitted radiation from these sources will lead to a better understating of both the emission mechanisms and source geometries. The GRAPE design consists of an array of plastic scintillators surrounding a central high‐Z crystal scintillator. We can monitor individual Compton scatters …

Medium-Energy Gamma-Ray Astrophysics With The 3-Dti Gamma-Ray Telescope, Stanley D. Hunter, Robert G. Baker, Louis M. Barbier, Peter F. Bloser, La Vida Cooper, John F. Krizmanic, Jason T. Link, Mark L. Mcconnell, Geoergia A. De Nolfo, James M. Ryan, Satpal Singh, Seunghee Son

Space Science Center

Gamma-ray observations in the medium energy range (0.50-50.0 MeV) are central to unfolding many outstanding questions in astrophysics. The challenges of medium-energy gamma-ray observations, however, are the low photon statistics and large backgrounds. We review these questions, address the telescope technology requirements, and describe our development of the 3-Dimensional Track Imaging (3-DTI) Compton telescope and its performance for a new mediumenergy gamma-ray mission. The 3-DTI is a large-volume time projection chamber (TPC) with a 2-dimensional gas micro-well detector (MWD) readout.