ODI Open Data Certificate

A Fast Compton Telescope for Detection and Imaging of Gamma-Ray Line Flares Project

View certificate

Published By National Aeronautics and Space Administration

Issued más de 9 años ago

beta

Summary

Type of release

a one-off release of a single dataset

Data Licence

Not Applicable

Content Licence

Creative Commons CCZero

Verification

automatically awarded

Description

One of the major goals of high-energy solar physics, and therefore of the Solar and Heliospheric Physics (SHP) Program, is a detailed understanding of the particle acceleration processes taking place on the Sun during solar flares. Flares can accelerate electrons to tens of MeV and ions to energies exceeding 1 GeV, as evidenced by the neutral radiation that can be studied remotely. The intense scientific interest in understanding this process is evidenced by the large number of wh ite papers dedicated to the topic that were submitted in response to the current Heliophysics Decadal Survey. A recurring theme in many white papers is the central role that new, sensitive observations of the gamma-ray line emissions from flares must play in disentangling the problem of acceleration and transport of energetic particles (Lin et al. 2010; Shih et al. 2010; Desai et al. 2010). More specifically, to significantly advance the study of solar flare particle acceleration, it will be necessary to&nbsp; compare in detail the spatial, spectral, and temporal evolution of electron signatures&nbsp; (hard X-ray and gamma-ray continuum emission from bremsstrahlung) and ion signatures (gamma-ray lines and pion-decay continuum from accelerated ions colliding with the solar atmosphere) over a wide dynamic range of flare sizes and intensities. For the gamma-ray lines, comprehensive measurements require angular resolution of ~10 arcsec or better at energies up to ~10 MeV, energy resolution of a few percent or better, and sensitivity at least 10 times better than that of previous instruments. Making such complex measurements over a large dynamic range presents a serious challenge to gamma-ray instrumentation, which must deal with large backgrounds for faint flares and high count rates for bright flares. In addition, future missions to study flare particle acceleration, such as the Solar Eruptive Events (SEE) 2020 concept presented by Lin et al. (2010), will contain entire suites of instruments to ensure that complementary measurements are made in a coordinated manner. Unprecedented gamma-ray measurements must therefore be made without consuming the spacecraft&rsquo;s mass, power, and telemetry budgets. Three recent technological developments potentially allow us to combine the abilities of these pioneering instruments: 1) Recently developed scintillator materials, in particular LaCl 3:Ce and LaBr 3:Ce, offer a far more attractive mix of stopping power, energy resolution, and fast time response than NaI and BGO scintillators. Energy resolution better than 3% above 0.6 MeV and timing resolution well below 500 ps are now well established. 2) Recently developed Silicon Photo-Multipliers (SiPMs) offer a compact, low-mass, and low-power alternative to PMTs. We have already shown that detectors composed of LaBr 3 scintillator coupled to SiPM readouts perform well as gamma-ray spectrometers (Bloser et al. 2008, 2010a). 3) Newly available compact arrays of SiPMs, with sensing elements typically 3 &ndash; 4 mm in size, promise the additional ability to achieve fine spatial resolution within scintillators in a compact Anger camera configuration. Gamma-ray detectors of this nature are currently being developed by the medical imaging community (e.g., Schaart et al. 2009), and position resolution of 1 mm or better has been demonstrated &nbsp; We propose a program of instrument development and modeling to show that a fast Compton telescope based on an innovative combination of new scintillator detectors and light readout devices, combined with an imaging grid or mask, is a scientifically competitive solution to this instrumentation challenge&nbsp;&nbsp;In effect, we will attempt to combine the best features of past solar gamma-ray instruments into an efficient, low-background, imaging gamma-ray spectrometer. The RHESSI mission (Lin et al. 2002) made the first high-angularresolution images at gamma-ray energies, adapting Fourier-synthesis methods previously used at hard X-ray energies (e.g., the Yohkoh Hard X-ray Telescope; Kosugi et al. 1991) to image the 2.2 MeV neutron-capture line with a resolution of about 35 arcsec (Hurford et al. 2006). Earlier gamma-ray spectrometers based on efficient inorganic scintillators, including those on the Solar Maximum Mission (SMM; Forrest et al. 1980), Yohkoh (Yoshimori et al. 1992), and the Compton Gamma Ray Observatory (e.g., Murphy et al. 1993), made sensitive spectral observations up to &gt;10 MeV over a large range of flare intensities. The most sensitive gammaray flare spectrometer of all was the COMPton TELescope (COMPTEL) on CGRO (Sch&ouml;nfelder et al. 1993; Ryan &amp; McConnell 1996). As a scintillator-based Compton telescope, COMPTEL was able to dramatically suppress background using a fast coincidence, time-of-flight (ToF) measurements, and coarse imaging ability. COMPTEL was able to detect nuclear emission from a C4 flare, the faintest such detection to date (Young et al. 2001). &nbsp; &nbsp;

A Fast Compton Telescope for Detection and Imaging of Gamma-Ray Line Flares Project

Summary

Description

Create a certificate

Sign in

Don't have an account?