Richard A. Leske

Large diameter lithium compensated silicon detectors for the NASA Advanced Composition Explorer (ACE) mission

Fabrication of the 100 mm diameter, 3 mm thick lithium-compensated silicon, Si(Li), detectors for the Cosmic Ray Isotope Spectrometer (CRIS) instrument on board the ACE satellite required development of: new float-zone silicon growing techniques, new Si(Li) fabrication procedures, and new particle beam testing sequences. These developments are discussed and results are presented that illustrate the advances made in realizing these CRIS Si(Li) detectors, which, when operational in the CRIS detector telescopes, will usher in a new generation of cosmic-ray isotope spectrometers.

A 360° Survey of Solar Energetic Particle Events and One Extreme Event

We report on a 3-point longitudinal survey of Solar Energetic Particle (SEP) events during 2010-2014 using data from the STEREO and near-Earth spacecraft. During the period from August 2010 through September 2014 a total of 77 SEP events were identified with >10 MeV proton intensities that exceeded the NOAA criterion of >10 protons/(cmsr-s), including 37 events at STEREO-A and 36 each at GOES and STEREO-A. Thirty-seven percent of the events reached this threshold intensity at more than one location. Unexpected solar activity in December 2006 provided an opportunity to cross-calibrate the STEREO and GOES sensors, demonstrating that the >10 MeV response for GOES was ~5%-8% greater than for the STEREOs, while the STEREO A&B responses agreed to within 2%. The July 23, 2012 event observed by STEREO-A was found to be the most intense SEP event in more than 20 years. We present observations of the longitude distribution of SEP events and fluences and compare properties of the July 23, 2012 event with those of the largest events of earlier solar cycles.

Observation of

M. H. Israel*, W. R. Binns, E. R. Christian, A. C. Cummings, G. A. de Nolfo, K. A. Lave, R. A. Leske, R. A. Mewaldt, E. C. Stone, T. T. von Rosenvinge, M.E. Wiedenbeck Washington University, St. Louis, MO 63130 USA NASA/Goddard Space Flight Center, Greenbelt, MD 20771 USA California Institute of Technology, Pasadena, CA 91125 USA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA

^{60}{\rm Fe}

M. E. Wiedenbeck∗†a, C. M. S. Cohenb, A. Klassenc, R. A. Leskeb, P. A. Liewera, G. M. Masond, and N. V. Nittae a Jet Propulsion Laboratory, California Institute of Technology Pasadena, CA 91109 USA b California Institute of Technology Pasadena, CA 91125 USA c Christian-Albrechts Universität zu Kiel D-24118 Kiel, Germany d Applied Physics Laboratory, Johns Hopkins University Laurel, MD 20723 USA e Lockheed-Martin Solar and Astrophysics Lab Palo Alto, CA 94304 USA E-mail: mark.e.wiedenbeck@jpl.nasa.gov

in the Galactic Cosmic Rays

A high pressure gas ionization chamber has been developed for studies of cosmic ray isotopic composition. In tests using accelerator beams of heavy ions it has achieved mass resolution ranging from σM≂0.1 amu for oxygen to σM≂0.3 amu for iron.

Constraints on Mechanisms for Longitudinal Spreading of Impulsive SEPs from Multispacecraft Observations of Scatter-free Even

Abstract We have developed a high pressure (3–10 atm) segmented-anode gas ionization chamber and have investigated the capabilities of this type of instrument for identifying energetic heavy nuclei. For individual nuclei which stop in the active volume of the detector, we use one or more measurements of the particles energy loss ( ΔE ) and its residual energy ( E ′) to derive its charge and mass. Experiments using accelerator beams have yielded unambiguous charge identification over the range of elements studied (up to Z = 26), and mass resolutions from σ M ⋍ 0.08 amu (Z = 6) to σ M ⋍ 0.35 amu (Z = 26) . The energy loss measurements provided by the segmented anode are supplemented by two-dimensional measurements of particle track coordinates made using a combination of drift time and charge division in a set of single-wire proportional counters. These tracking detectors provide a position resolution ≲ 0.6 mm for each coordinate, and make possible the path length corrections needed to study isotropic particle distributions such as those encountered in the cosmic radiation.