The ratios of fluxes of heavy nuclei from sulfur (Z = 16) to chromium (Z = 24) to the flux of iron were measured by the ATIC-2 experiment. The ratios are decreasing functions of energy from 5 GeV/n to approximately 80 GeV/n, as expected. However, an unexpected sharp upturn in the ratios are observed for energies above 100 GeV/n for all elements from Z = 16 to Z = 24. Similar upturn but with lower amplitude was also discovered in the ATIC-2 data for the ratio of fluxes of abundant even nuclei (C, O, Ne, Mg, Si) to the flux of iron. Therefore the spectrum of iron is significantly different from the spectra of other abundant even nuclei.

New analysis to separate electrons from protons in the ATIC experiment has been performed. Five new discriminants were studied by different Monte Carlo programs. New electron spectrum, when compared with the published results [1], show good agreement in the most interesting region of energy (from 90 GeV to 600 GeV). It is argued that there is no disagreement between ATIC’s results and Fermi-LAT ones. Finally, high-resolution electron spectrum is obtained and possible fine structure is found out in it. The ATIC (Advanced Thin Ionization Calorimeter) balloon-borne spectrometer was designed to measure the energy spectra of elements from H to Fe with individual resolution of charges in primary cosmic rays for energy region from 50 GeV to 100 TeV. ATIC has had three successful flights around the South Pole in 2000–2001 (ATIC-1), 2002-2003 (ATIC-2) and 2007-2008 (ATIC-4). ATIC is comprised of a fully active bismuth germanate (BGO) calorimeter, a carbon target with embedded scintillator hodoscopes, and a silicon matrix that is used as the main charge detector. The calorimeter is comprised of 8 layers with 40 BGO crystalls in each for ATIC-1 and ATIC-2 and of 10 layers for ATIC-4. The details of the construction of the apparatus are described in the papers [2–4]. It was shown that it is possible also to measure the spectrum of cosmic ray electrons plus positrons [5] with ATIC (hereinafter we use ’electrons’ for brevity). To separate electrons from the higher background of protons and other nuclei some differences in shower development for incident electrons and for nuclei are used. The spectrum of electrons measured with the ATIC spectrometer by this method was published in the paper [1]. The most notable detail of the electron spectrum reported was an ‘excess’ of electrons between energies of 300–800 GeV. The main purpose of this work is to investigate possible alternate techniques to separate electrons from hadrons and was curried ae-mail: panov@dec1.sinp.msu.ru E, GeV 2 10 3 10 ) 2 G eV -1 st er -1 s -2 (m 3

A strong excess in a form of a wide peak in the energy range of 300-800 GeV was discovered in the first measurements of the electron spectrum in the energy range from 20 GeV to 3 TeV by the balloon-borne experiment ATIC (J. Chang et al. Nature, 2008). The experimental data processing and analysis of the electron spectrum with different criteria for selection of electrons, completely independent of the results reported in (J. Chang et al. Nature, 2008) is employed in the present paper. The new independent analysis generally confirms the results of (J. Chang et al. Nature, 2008), but shows that the spectrum in the region of the excess is represented by a number of narrow peaks. The measured spectrum is compared to the spectrum of (J. Chang et al. Nature, 2008) and to the spectrum of the Fermi/LAT experiment.

A rotating modulator (RM) is capable of imaging hard x-rays and gamma rays by the temporal modulation of incident photons. It combines a single mask of equally-wide slats and slits, rotating above an array of detectors with diameter equal to the slats. Since the RM works in the temporal domain, appropriate analysis of the measured data enables super-resolution (resolution better than the geometric resolution), which consequently allows for larger detector elements, better efficiency at higher energies, and a simplified detector design. We describe the RM concept and discuss briefly a novel image reconstruction technique to achieve super-resolution and suppress fluctuations arising from noise. We present experimental results from a laboratory prototype and the concept and expected results for a high-altitude balloon flight of an RM. The High-Altitude Rotating Modulator for Energetic Radiation Imaging (HARMEnI) is a prototype balloon-borne instrument that offers a 20° field-of-view and 1.9° intrinsic resolution with a sensitivity in the range of 30-700 keV. At its intrinsic resolution, HARMEnI will obtain a 20σ observation of the Crab Nebula and Cygnus X-1 in approximately one hour. For a 1-day flight from Ft. Sumner, New Mexico, exposure times for these sources will exceed 3 hours, enabling enhancement of image resolution.

The Orbiting Astrophysical Observatory in Space (OASIS) is a mission to investigate Galactic Cosmic Rays (GCRs), a major feature of our galaxy. OASIS will use measurements of GCRs to determine the cosmic ray source, where they are accelerated, to investigate local accelerators and to learn what they can tell us about the interstellar medium and the processes that occur in it. OASIS will determine the astrophysical sources of both the material and acceleration of GCRs by measuring the abundances of the rare actinide nuclei and make direct measurements of the spectrum and anisotropy of electrons at energies up to approx.10 TeV, well beyond the range of the Fermi and AMS missions. OASIS has two instruments. The Energetic Trans-Iron Composition Experiment (ENTICE) instrument measures elemental composition. It resolves individual elements with atomic number (Z) from 10 to 130 and has a collecting power of 60m2.str.yrs, >20 times larger than previous instruments, and with improved resolution. The sample of 10(exp 10) GCRs collected by ENTICE will include .100 well-resolved actinides. The High Energy Particle Calorimeter Telescope (HEPCaT) is an ionization calorimeter that will extend the electron spectrum into the TeV region for the first time. It has 7.5 sq m.str.yrs of collecting power. This talk will describe the scientific objectives of the OASIS mission and its discovery potential. The mission and its two instruments which have been designed to accomplish this investigation will also be described.

Recently the Advanced Thin Ionization Calorimeter (ATIC) balloon experiment reported observations of high energy cosmic ray electrons over the energy range 300 to 800 GeV, indicating a feature or bump in the otherwise smoothly decreasing energy spectrum. The severe energy losses that occur as these high energy particles traverse the galaxy render the cosmic ray electron spectrum sensitive to local (a few kiloparsecs) sources and hence very interesting. The ATIC results are the first time that such a cosmic ray spectrum anomaly has been observed at high energy. Potential sources of this electron excess include pulsars, microquasars, supernovae remnants as well as the annihilation of exotic dark matter candidate particles. ATIC has had three successful high altitude flights over the continent of Antarctica 2000-2001, 2002-2003 and 2007-2008. Only results from the first two flights have been reported so far. During this talk we will discuss the ATIC experiment, the electron observations (including preliminary results from the most recent ATIC flight), examine the merits of the various source models and compare the ATIC observations with other recent measurements.

Laser Gated Imaging is a unique camera technology. It provides long-range night vision in complete darkness as well as in degraded weather conditions, such as rain, fog and haze. Burst illumination laser (BIL) imaging combines an active laser illumination with time gating (or range gating) camera. For these reasons, BIL imaging has become increasingly important in Defense and security applications. In an associated paper [01], we present a model (PIAF) developed to evaluate the relevant physical phenomena (scintillation, speckle...) impacting on the BIL imaging. This paper presents preliminary experimental results and comparisons with PIAF simulations.

High-energy cosmic rays The ATIC (Advanced Thin Ionizaton Calorimeter) cosmic-ray astronomy experiment sends helium balloons to altitudes of 35 km and more above Antarctica for up to 15 days at a time. These forays to the edge of space have resulted in the detection of an excess of Galactic cosmic-ray electrons at energies of around 300–800 GeV, which indicates a nearby source of energetic electrons. The source could be an unseen astrophysical object that accelerates electrons to those energies, or the electrons could arise from the annihilation of 'Kaluza-Klein' dark matter, an exotic concept predicted by theories of the Universe involving compactified extra dimensions.

,acharacteristic distance for energy loss by bremsstrahlung) in eightlayers arranged in orthogonal pairs to measure the energy depositedthrough a cascade (shower) of nuclear and electromagnetic interac-tions.Ateachstepofthecascade,theenergyoftheprimaryparticleissubdividedamongmanysecondaryparticles.Theareaunderthecurveof ionization energy plotted against depth in the medium provides ameasureoftheincidentparticleenergy,andthelateraldistributionofenergy across each layer can be used to separate electrons from pro-tons.Thetopmostelementisapixelatedsiliconmatrix(SiM)detector(4,480pixels)whichmeasuresthechargeoftheincidentparticle.Thisisfollowedbythreelayersofscintillatorhodoscopesembeddedwithina 30-cm-thick graphite target (this amount of material is 0.75 timesthe proton interaction length, and 1.5 times X

The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined.

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed for high energy cosmic ray ion detection. The possibility to identify high energy primary cosmic ray electrons in the presence of the ‘background’ of cosmic ray protons has been studied by simulating nuclear-electromagnetic cascade showers using the FLUKA Monte Carlo simulation code. The ATIC design, consisting of a graphite target and an energy detection device, a totally active calorimeter built up of 2.5cm×2.5cm×25.0cm BGO scintillator bars, gives sufficient information to distinguish electrons from protons. While identifying about 80% of electrons as such, only about 2 in 10,000 protons (@ 150GeV) will mimic electrons. In September of 1999 ATIC was exposed to high-energy electron and proton beams at the CERN H2 beam line, and this data confirmed the electron detection capabilities of ATIC. From 2000-12-28 to 2001-01-13 ATIC was flown as a long duration balloon test flight from McMurdo, Antarctica, recording over 360h of data and allowing electron separation to be confirmed in the flight data. In addition, ATIC electron detection capabilities can be checked by atmospheric gamma-ray observations.