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The paper describes a novel detector for neutrons in the 1 to 20-MeV energy range with combined imaging and spectroscopic capabilities. The Fast Neutron Imaging Telescope (FNIT) was designed to detect solar neutrons from spacecraft deployed to the inner heliosphere. However, the potential application of this instrument to Special Nuclear Material (SNM) identification was also examined. In either case, neutron detection relies on double elastic neutron-proton (n-p) scattering in liquid scintillator. We optimized the design of FNIT through a combination of Monte Carlo simulations and lab measurements. We then assembled a scaled-down version of the full detector and assessed its performance by exposing it to a neutron beam and an SNM source. The results from these tests, which were used to characterize the response of the complete FNIT detector to fast neutrons, are presented herein.

The capability to detect fast neutrons with good angular and energy resolutions is gaining increased interest for different applications such as non-destructive testing, homeland security, and space-borne solar physics. To the latter aim, we recently developed and tested a novel type of instrument, the Fast Neutron Imaging Telescope (FNIT), for neutron spectroscopy and imaging in the 1-20 MeV range. Assessments of the instrument prototype performances, based on Monte Carlo simulations and on results from calibration tests performed in a monoenergetic neutron beam, are presented here. The purpose of the study is twofold: (1) to provide a comprehensive characterization of the prototype response, notably in terms of efficiency, event selection, energy and angular resolution; (2) to validate the simulation tool to support data analysis and reduction, and also to help in the design of more complex fast neutron telescopes.

The PAMELA space experiment is providing first direct observations of Solar Energetic Particles (SEPs) with energies from about 80 MeV to several GeV in near-Earth orbit, bridging the low energy measurements by other spacecrafts and the Ground Level Enhancement (GLE) data by the worldwide network of neutron monitors. Its unique observational capabilities include the possibility of measuring the flux angular distribution and thus investigating possible anisotropies associated to SEP events. The analysis is supported by an accurate back-tracing simulation based on a realistic description of the Earth's magnetosphere, which is exploited to estimate the SEP energy spectra as a function of the asymptotic direction of arrival with respect to the Interplanetary Magnetic Field (IMF). In this work we report the results for the May 17, 2012 event.

The Medium Energy Gamma-ray Astronomy (MEGA) telescope concept will soon be proposed as a MIDEX mission. This mission would enable a sensitive all-sky survey of the medium-energy gamma-ray sky (0.4–50 MeV) and bridge the huge sensitivity gap between the COMPTEL and OSSE experiments on the Compton Gamma Ray Observatory and the visionary Advanced Compton Telescope (ACT) mission. The scientific goals include compiling a much larger catalog of sources in this energy range, performing far deeper searches for supernovae, better measuring the galactic continuum and line emissions, and identifying the components of the cosmic diffuse gamma-ray emission. MEGA records and images gamma rays by completely tracking Compton and pair creation events in a stack of double-sided Si strip detectors surrounded by a pixellated CsI calorimeter. A prototype instrument has been developed and calibrated in the laboratory and at a gamma-ray beam facility. We present calibration results from the prototype and describe the proposed satellite mission.

We report the first measurement of the deuterium abundance in cosmic rays above 10 GeV nucleon � 1 of kinetic energy. The data were collected by the balloon-borne experiment CAPRICE98, which was flown on 1998 May 28–29 from Fort Sumner, New Mexico. The detector configuration included the NMSU-WiZard/CAPRICE superconducting magnet spectrometer equipped with a gas RICH detector, a silicon-tungsten calorimeter, and a time-of-flight system. By combining the information from the spectrometer and the RICH detector, it was possible to separate deuterons from protons in the kinetic energy range from 12 to 22 GeV nucleon � 1 .I n order to estimate the proton background and the deuteron selection efficiency, we developed an empirical model for the response of the instrument, based on the data collected in this experiment. The analysis procedure is described in this paper, and the result on the absolute flux of deuterium is presented. We found that the deuterium abundance at high energy is consistent with the hypothesis that the propagation mechanism of light nuclei is the same as that of heavier secondary components. Subject headings: balloons — cosmic rays — Galaxy: abundances — ISM: abundances

The Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) will perform a direct measurement of the elemental composition and energy spectra of cosmic-ray particles up to an energy of 10 15 eV. The detector complement of ACCESS consists of a TRD and a ionization calorimeter, and six different concepts for the ACCESS calorimeter design alone have been proposed in the recent past. In this work, we present the structure optimization analysis and the Monte Carlo simulation results on detector performance for the silicon–tungsten (Si–W) imaging calorimeter design for ACCESS, developed as part of the NASA-sponsored mission concept and detector assessment study for this experiment.

Two recent balloon-borne experiments have been performed by the Wizard/CAPRICE collaboration in order to study the electron and positron components in the cosmic radiation. On 1994 August 8-9 the CAPRICE94 experiment flew from norther Canada and on 1998 May 28-29 the CAPRICE98 experiment flew from New Mexico, USA at altitude8 corresponding to 3.9 and 5.5 g/cm2 of average residual atmosphere respectively. The apparatus were equipped with a Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a superconducting magnet spectrometer with a tracking system and a 7-radiation-length silicon-tungsten imaging calorimeter. The RICH used in 1994 had a solid NaF radiator while in 1998 the RICH had a CbFlO gaseous radiator. We report on the electron and positron spectra and positron fraction at the top of the atmosphere from few hundred MeV to 40 GeV measured by these two experiments.

This paper describes a few relevant features of beam emittance that usually go unnoticed in typical beam profile measurements, but are of significance when determining the performance of a muon cooling channel with high accuracy, in the presence of a wide energy spread and solenoidal magnetic field.

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 1–20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

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 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

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, constrained by earlier measurements at 1 AU. Laboratory results and simulations will be presented illustrating the instrument sensitivity and resolving power.

The Fast Neutron Imaging Telescope (FNIT) instrument is a NA-22 funded project for the design, construction, calibration and modeling of an instrument specifically tailored to measure and identify sources of fission neutrons - a key signature of Special Nuclear Material (SNM). A neutron detector that is sensitive to this energy range is of utmost importance to stop the proliferation of these materials. The proof of concept of this instrument has been successfully demonstrated with a limited FNIT prototype. After being constructed and fine-tuned at the University of New Hampshire (UNH), the prototype was calibrated with quasi-monoenergetic neutron beams at Crocker Nuclear Laboratory. Extensive Monte Carlo calculations are currently in the advance stages for the modeling of FNIT. These simulations, along with the calibration and tests that have been performed with a 252Cf source at UNH, will be used to determine the instrument efficiency and response. Further instrument simulations will allow us to determine the best methods for spectral and imaging de-convolution. Ultimately, these methods will be implemented into “on-line” software being designed for real-time analysis algorithms to be used in conjunction with a fully populated, portable neutron telescope. We present the most recent laboratory and instrument modeling results.

We describe the development, testing and performance of a Fast Neutron Imaging Telescope (FNIT) with the capability of detecting and composing real-time images of a neutron source. A key signature unique to Special Nuclear Material (SNM) is the emission of fission neutrons. An efficient neutron detector that is sensitive to neutrons in the energy range of 1-10 MeV and with imaging capability represents a key tool for the interdiction of smuggling of clandestine amounts of SNM into the country. A small, modular, organic liquid scintillator detector - initially developed at the University of New Hampshire to study solar neutrons - has been tailored to locate fission neutron sources in homeland security applications. The principle of detection is based on multiple elastic neutron-proton scattering. By measuring the interaction locations and the recoil proton energies, we can determine the direction and energy spectrum of the primary neutron flux along with the location of the neutron source. Key parameters determined in the laboratory thus far have been an energy (trigger) threshold of 200 keV (proton equivalent) and a 5deg (sigma) angular resolution across a broad energy range. This paper outlines the most recent results on instrument development, the FNIT detector's response to SNM and real-time neutron imaging development.

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 81 cm: one 8.5 cm thick liquid scintillator detector and one 7.5 cm thick Nal(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 a cone with full angle approximately 120deg. The sensitive energy range is 0.3 to 2.6 MeV. Energy resolution is ~10% FWHM. The angular resolution, ~15deg in the simplified configuration tested, will improve to better than 5deg with well-defined enhancements to the data acquisition hardware and data analysis routines. We conducted a series of laboratory demonstrations to characterize the performance of the GRETA detector. Following detector characterization, we demonstrate GRETA 's ability to locate and identify an unknown source and position within its field of view. In this scenario, the location and isotope-identifying energy spectrum of an 800 muCi137 Cs source 10 meters from the instrument with two intervening walls was determined in less than one minute. We will present further details of the instrument design and the measurements.

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 scintillators. By reconstructing n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. We describe the design of the FNIT prototype and present its energy reconstruction and imaging performance, assessed by exposing FNIT to a neutron beam and to a Pu fission neutron source. Keywords: fast neutrons, neutron imaging, passive SNM search, container screening 1. INTRODUCTION A critical gap in national security is the inability to efficiently detect and identify problematic quantities of Special Nuclear Material (SNM). These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike the other forms of radiation produced by SNM (e.g. -rays), copious and penetrating neutron emission is unique to fissionable material. From a practical point of view, shielding of fission neutrons ( e.g. in a cargo container) represents a far greater challenge and requires a considerably larger and heavier amount of passive material than shielding of other forms of radiation emitted by SNM. Neutron detection, therefore, is of particular interest for SNM identification for security and proliferation deterrence, as well as for nuclear waste detection and monitoring. While improvements in all forms of radiation detection are necessary to close the SNM security gap, there are unique problems associated with the detection and measurement of neutrons. Some of these are: • current neutron detectors used in the field ( e.g. Bonner spheres

Illicit nuclear materials represent a threat for the safety of the American citizens, and the detection and interdiction of a nuclear weapon is a national problem that has not been yet solved. Alleviating this threat represents an enormous challenge to current detection methods that have to be substantially improved to identify and discriminate threatening from benign incidents. Rugged, low-power and less-expensive radiation detectors and imagers are needed for large-scale wireless deployment. Detecting the gamma rays emitted by nuclear and fissionable ma terials, particularly special nuclear materials (SNM), is the most convenient way to identify and locate them. While there are detectors that have the necessary sensitivity, none are suitable to meet the present need, primarily because of the high occurrence of false alarms. The exploitation of neutron signatures represents a promising solution to detecting illicit nuclear materials. This work presents the development of several detector configurations such as a mobile active interrogation system based on a compact RF-Plasma neutron generator developed at LBNL and a fast neutron telescope that uses plastic scintillating-fibers developed at the University of New Hampshire. A human-portable improved Solid-State Neutron Detector (SSND) intended to replace pressurized

We describe the design and performance of a prototype instrument with capabilities for both imaging and spectroscopy of sources of 1-10 MeV neutrons. The laboratory prototype is composed of custom-designed liquid scintillator detectors and employs measurements of double neutron-proton scattering to determine the direction and energy of incident neutrons. The detectors provide measurements of the position, energy deposit and pulse shape for each interaction. Pulse shape discrimination and a time-of-flight measurement between coincident interactions in two detectors are used to identify the neutron events, reject background due to Compton scattered gamma radiation and provide a measure of the scattered neutron energy. Calculations employing double n-p scattering kinematics are used to accumulate images and spectra of the neutron source. The quality of these images and spectra is correlated with the energy, position and timing resolution of the detectors. The prototype instrument achieves ~5deg angular resolution and 20% energy resolution (1sigma). This paper presents the design and the most recent results.

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 shielded and masked samples. The detection principle is based on multiple elastic neutron-proton (n-p) scatterings in organic scintillators. By reconstructing the n-p event locations and sequence and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron point sources identified. The performance of FNIT is being evaluated through a series of Monte Carlo simulations and lab tests of detector prototypes. The Science Model One (SM1) of this instrument was recently assembled and is presently undergoing performance testing.

Inner heliosphere measurements of the Sun can be conducted with the proposed Solar Sentinel spacecraft and mission. One of the key measurements that can be made inside the orbit of the Earth is that of lower energy neutrons that arise in flares from nuclear reactions. Solar flare neutrons below 10 MeV suffer heavy weak-decay losses before reaching 1 AU. For heliocentric radii as close as 0.3 AU, the number of surviving neutrons from a solar event is dramatically greater. Neutrons from 1-10 MeV provide a new measure of heavy ion interactions at low energies, where the vast majority of energetic ions reside. Such measurements are difficult because of locally generated background neutrons. An instrument to make these measurements must be compact, lightweight and efficient. We describe our progress in developing a low-energy neutron telescope that can operate and measure neutrons in the inner heliosphere and take a brief look at other possible applications for this detector.

The Medium Energy Gamma-ray Astronomy (MEGA) telescope concept will soon be proposed as a MIDEX mission. This mission would enable a sensitive all-sky survey of the medium-energy gamma-ray sky (0.4 - 50 MeV) and bridge the huge sensitivity gap between the COMPTEL and OSSE experiments on the Compton Gamma Ray Observatory, the SPI and IBIS instruments on INTEGRAL, and the visionary Advanced Compton Telescope (ACT) mission. The scientific goals include, among other things, compiling a much larger catalog of sources in this energy range, performing far deeper searches for supernovae, better measuring the galactic continuum and line emissions, and identifying the components of the cosmic diffuse gamma-ray emission. MEGA will accomplish these goals using a tracker made of Si strip detector (SSD) planes surrounded by a dense high-Z calorimeter. At lower photon energies (below ~ 30 MeV), the design is sensitive to Compton interactions, with the SSD system serving as a scattering medium that also detects and measures the Compton recoil energy deposit. If the energy of the recoil electron is sufficiently high (> 2 MeV) its momentum vector can also be measured. At higher photon energies (above ~ 10 MeV), the design is sensitive to pair production events, with the SSD system measuring the tracks of the electron and positron. A prototype instrument has been developed and calibrated in the laboratory and at a gamma-ray beam facility. We present calibration results from the prototype and describe the proposed satellite mission.

Muon cooling represents an essential component of a Neutrino Factory. The short muon lifetime makes it impossible to employ traditional cooling techniques to reduce the muon beam emittance while maintaining its intensity. Therefore a new concept, ionization cooling, has been developed specifically for muons. It will be tested for the first time in the international Muon Ionization Cooling Experiment (MICE), by placing a short section of a realistic cooling channel in a muon beam at the Rutherford Appleton Laboratory (RAL) and measuring its performance. The layout of MICE, its instrumentation and implementation at RAL are described, together with a discussion of the predicted performance and current status of this experiment.

The measurement of the atmospheric muon spectrum is currently of great interest because of the study of atmospheric neutrinos and the claim of neutrino oscillations made in 1998 by the Super-Kamiokande Collaboration. A measurement of the muon flux is an indirect measure of the neutrino flux. Therefore, it can be used to improve the calculation of the atmospheric neutrino flux, which in turn can be compared with the observed neutrino rates in underground detectors. This article reports a new measurement of the m 1 and m 2 spectra at several atmospheric depths in the momentum ranges 0.3‐20 GeV/c and 0.3‐40 GeV/c, respectively. The data were collected by the balloon-borne experiment CAPRICE98 during the ascent of the payload on 28 May 1998 from Fort Sumner, N. M. The experiment used the NMSU-WIZARD/CAPRICE 98 balloon-borne magnet spectrometer equipped with a gas ring imaging Cherenkov detector and a silicon-tungsten calorimeter.

A new measurement of the primary cosmic-ray proton and helium fluxes from 3 to 350 GeV was carried out by the balloon-borne CAPRICE experiment in 1998. This experimental setup combines different detector techniques and has excellent particle discrimination capabilities allowing clear particle identification. Our experiment has the capability to determine accurately detector selection efficiencies and systematic errors associated with them. Furthermore, it can check for the first time the energy determined by the magnet spectrometer by using the Cherenkov angle measured by the RICH detector well above 20 GeV/n. The analysis of the primary proton and helium components is described here and the results are compared with other recent measurements using other magnet spectrometers. The observed energy spectra at the top of the atmosphere can be represented by (1.27+-0.09)x10^4 E^(-2.75+-0.02) particles (m^2 GeV sr s)^-1, where E is the kinetic energy, for protons between 20 and 350 GeV and (4.8+-0.8)x10^2 E^(-2.67+-0.06) particles (m^2 GeV nucleon^-1 sr s)^-1, where E is the kinetic energy per nucleon, for helium nuclei between 15 and 150 GeV nucleon^-1., To be published on Astroparticle Physics (44 pages, 13 figures, 5 tables)

The PAMELA equipment will be assembled in 2001 and installed on board the Russian satellite Resurs. PAMELA is conceived mainly to study the antiproton and positron fluxes in cosmic rays up to high ...

The CAPRICE98 balloon-borne instrument was flown on 28–29 May 1998 from Fort Sumner (New Mexico, USA). The detector configuration included the NMSU-WiZard/CAPRICE superconducting-magnet spectrometer equipped with a gas RICH, a silicon-tungsten calorimeter and a time-of-flight system. By combining the information from the spectrometer and the RICH, which was used as a threshold device, it was possible to separate 2 H from 1 H in the kinetic energy range from 12 to 22 GeV/n. In order to estimate the proton background and the deuteron selection efficiency, an empirical model for the response of the instrument, based on the data collected in this experiment, was developed. The analysis procedure is described in this paper and the results on the absolute flux of 2 H and 2 H/He ratio are presented. These data on 2 H abundance represent the only measurements above 10 GeV/n.

We report on a new measurement of the cosmic ray antiproton spectrum. The data were collected by the balloon-borne experiment CAPRICE98 which was flown on 28-29 May 1998 from Fort Sumner, New Mexico, USA. The experiment used the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a tracking device consisting of drift chambers and a superconducting magnet and a silicon-tungsten calorimeter. The RICH detector was the first ever flown capable of mass-resolving charge-one particles at energies above 5 GeV. A total of 31 antiprotons with rigidities between 4 and 50 GV at the spectrometer were identified with small backgrounds from other particles. The absolute antiproton energy spectrum was determined in the kinetic energy region at the top of the atmosphere between 3.2 and 49.1 GeV. We found that the observed antiproton spectrum and the antiproton-to-proton ratio are consistent with a pure secondary origin. However, a primary component may not be excluded., Comment: 39 pages, 11 Postscript figures, uses AAS LATEX style; changes in sections 3.1.1, 3.3, 3.4 and 6, Figure 8 modified, 2 figures added, typos corrected

CAPRICE98 is a superconducting magnetic spectrometer, equipped with a gas RICH and a silicon calorimeter, launched from Ft. Sumner (USA), on the 28th of May 1998, by the WiZard collaboration. For the first time a gas RICH detector flew together with a silicon electromagnetic calorimeter, allowing mass resolved antiprotons, with E>18 GeV, to be detected. The detector configuration was completed by a time of flight for particle identification, and a set of three drift chambers for rigidity measurement. The science objectives are the study of antimatter in cosmic rays and the cosmic ray composition in the atmosphere with special focus on muons.

We provide in this paper a status report of the space experiment PAMELA. PAMELA aims primarily to measure the flux of antiparticles, namely antiprotons and positrons, in cosmic rays with unpreceden ...

We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28‐29 from Fort Sumner, New Mexico. The measured /p ¯ p ratio is in agreement with a pure secondary interstellar production. Subject headings: acceleration of particles — balloons — cosmic rays — dark matter — elementary particles

CAPRICE98 is a superconducting magnetic spectrometer built by the WiZard collaboration. It was launched from Ft. Summer, NM, USA on the 28th of May 1998. For the first time a gas RICH detector has been flown together with a silicon electromagnetic calorimeter. The instrument configuration included a time of flight detector and a drift chamber stack, which were placed in the region of a magnet field, for rigidity measurement. Science objectives for this experiment include the study of antimatter in cosmic rays and that of cosmic ray composition in the atmosphere with special focus on muons.

We report on the absolute antiproton Nux and the antiproton to proton ratio in the energy range 0.62E3.19 GeV at the top of the atmosphere, measured by the balloon-borne experiment CAPRICE Nown from Lynn Lake, Manitoba, Canada, on 1994 August 8E9. The experiment used the New Mexico State University WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cherenkov (RICH) detector and a silicon-tungsten calorimeter for particle identi-cation. This is the -rst time a RICH is used together with an imaging calorimeter in a balloon experiment, and it allows antiprotons to be clearly identi-ed over the rigidity range 1.2E4 GV. Nine antiprotons were identi-ed in the energy range 0.62E3.19 GeV at the top of the atmosphere. The data were collected over 18 hr at a mean residual atmosphere of 3.9 g cm~2. The absolute antiproton Nux is consistent with a pure secondary production of antiprotons during the propagation of cosmic rays in the Galaxy. Subject headings: balloons E cosmic rays E elementary particles E Sun: activity

We report a new measurement of the momentum spectra of both positive and negative muons as a function of atmospheric depth in the momentum range 0.3 ‐ 2 and 0.3 40 GeVyc, respectively. The measured flux values have been compared with the spectra obtained from simulations, which were carried out to interpret the atmospheric neutrino data. We find that our data disagree with the results from the simulations. The ratio of the flux of muons derived from simulations to that measured is at largest 1.8 and varies with atmospheric depth and muon momentum. [S0031-9007(99)09347-3]

As part of a series of experiments to search for antimatter in cosmic rays, the New Mexico State University balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than 3 × 104. This instrument was flown from Fort Sumner, New Mexico, at an average depth of 4.5 g cm-2 of residual atmosphere for a period of 25 hr. We report here the measured fraction of positrons e+/(e+ + e-) from ~5 to 60 GeV at the top of the atmosphere. Our measurements do not show any compelling evidence for an increase in this ratio with energy, and our results are consistent with a constant fraction of 0.078 ± 0.016 over the entire energy region.

The great challenge in constraining scenarios for solar energetic particle (SEP) acceleration is due to the fact that the signatures of acceleration itself are heavily modified by transport within interplanetary space. During transport, SEPs are subject to pitch angle scattering by the turbulent magnetic field, adiabatic focusing, or reflecting magnetic structures. Ground Level Enhancements (GLEs) provide an ideal way to study acceleration with minimal transport. In this work, we present a unique high-energy SEP observation from PAMELA of the 2012 May 17 GLE and interpret the observed pitch angle distributions as a result of local scattering (1 AU) by the Earth's magnetosheath.

A new measurement of the momentum spectra of both positive and negative muons as function of atmospheric depth was made by the balloon-borne experiment CAPRICE94. The data were collected during ground runs in Lynn Lake on the 19-20th of July 1994 and during the balloon flight on the 8-9th of August 1994. We present results that cover the momentum intervals 0.3-40 GeV/c for negative muons and 0.3-2 GeV/c for positive muons, for atmospheric depths from 3.3 to 1000 g/cm**2, respectively. Good agreement is found with previous measurements for high momenta, while at momenta below 1 GeV/c we find latitude dependent geomagnetic effects. These measurements are important cross-checks for the simulations carried out to calculate the atmospheric neutrino fluxes and to understand the observed atmospheric neutrino anomaly., Comment: 28 pages, 13 Postscript figures, uses revtex.sty, to appear in Phys. Rev. D

We report new measurements of the muon spectra and the muon charge ratio at ground level in the momentum range from 200 MeVc to 120 GeVc for two different geomagnetic locations. Above 0.9 GeVc the absolute spectra measured in the two locations are in good agreement and are about 10% to 15% lower than previous experimental results. At lower momenta the data show latitude dependent geomagnetic effects. These observations are important for the understanding of the observed neutrino anomaly.