Mark J. Christl

An excess of cosmic ray electrons at energies of 300-800 GeV

Galactic cosmic rays consist of protons, electrons and ions, most of which are believed to be accelerated to relativistic speeds in supernova remnants. All components of the cosmic rays show an intensity that decreases as a power law with increasing energy (for example as E-2.7). Electrons in particular lose energy rapidly through synchrotron and inverse Compton processes, resulting in a relatively short lifetime (about 105 years) and a rapidly falling intensity, which raises the possibility of seeing the contribution from individual nearby sources (less than one kiloparsec away). Here we report an excess of galactic cosmic-ray electrons at energies of ∼300–800 GeV, which indicates a nearby source of energetic electrons. Such a source could be an unseen astrophysical object (such as a pulsar or micro-quasar) that accelerates electrons to those energies, or the electrons could arise from the annihilation of dark matter particles (such as a Kaluza–Klein particle with a mass of about 620 GeV).

Energy spectra of abundant nuclei of primary cosmic rays from the data of ATIC-2 experiment: Final results

The final results of processing the data from the balloon-born experiment ATIC-2 (Antarctica, 2002–2003) for the energy spectra of protons and He, C, O, Ne, Mg, Si, and Fe nuclei, the spectrum of all particles, and the mean logarithm of atomic weight of primary cosmic rays as a function of energy are presented. The final results are based on improvement of the methods used earlier, in particular, considerably increased resolution of the charge spectrum. The preliminary conclusions on the significant difference in the spectra of protons and helium nuclei (the proton spectrum is steeper) and the non-power character of the spectra of protons and heavier nuclei (flattening of carbon spectrum at energies above 10 TeV) are confirmed. A complex structure of the energy dependence of the mean logarithm of atomic weight is found.

Elemental energy spectra of cosmic rays from the data of the ATIC-2 experiment

This paper reports on the results of measurements performed in the course of the ATIC-2 balloon experiment (2002–2003) for the energy spectra of particles (such as protons; He, C, O, Ne, Mg, Si, and Fe nuclei; and some groups of nuclei) and the all-particle energy spectrum in primary cosmic rays at energies ranging from 50 GeV to 200 TeV. The conclusion is drawn that the energy spectra of protons and helium nuclei differ substantially (the spectrum of protons is steeper) and that the shape of the energy spectra of protons and heavy nuclei cannot be described by a power function.

Intense electron and proton beams from PetaWatt laser}matter interactions

Recent experiments at the LLNL Petawatt Laser have demonstrated the generation of intense, high-energy beams of electrons and ions from the interaction of ultra-intense laser light with solid targets. The focused laser intensities are as high as 6]1020 W/cm2, at which point the quiver energies of the target electrons extend to &10 MeV. In this new, fully relativistic regime of laser}plasma interactions, nuclear processes become important and nuclear techniques are required to diagnose the high-energy particle production. We describe recent experiments in which we have observed electrons accelerated to 100 MeV, photo-nuclearssion, positron}electron pair creation, monoenergetic electron jets and intense beams of protons emitted from the back surface of a laser-irradiated target. ( 2000 Elsevier Science B.V. All rights reserved.

The JEM-EUSO Mission

The JEM‐EUSO mission explores the origin of the extreme energy cosmic rays (EECRs) above 100 EeV and explores the limits of the fundamental physics, through the observations of their arrival directions and energies. It is designed to achieve an exposure larger than 1 million km2 sr year at the highest energies to open a new particle astronomy channel. This super‐wide‐field of view (60 degrees) telescope with a diameter of about 2.5 m looks down from space onto the night sky to detect near UV photons (330–400 nm, both fluorescent and Cherenkov photons) emitted from the giant air showers produced by EECRs. The arrival direction map with more than five hundred events after just the three years will tell us the origin of the EECRs, allow us to identify the nearest EECR sources with known astronomical objects, which can afterwards be examined in other astronomical channels. This is likely to lead to an understanding of the acceleration mechanisms perhaps producing discoveries in astrophysics and fundamental ph...

Possible structure in the cosmic ray electron spectrum measured by the ATIC-2 and ATIC-4 experiments

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.

Characterization of a multianode photomultiplier tube for use with scintillating fibers

Abstract The characteristics of a multianode photomultiplier tube (MAPMT; Hamamatsu R5900-00-M64) with 64 anodes have been studied. We report measurements that include single photoelectron sensitivity, electrical and optical cross-talk, dark count, and gain variation. Environmental test results relevant to use of these devices in space are also presented. The characteristics of the MAPMT make it well suited for detection of light from scintillating fibers as well as other applications.

Energy Dependence of Ti/Fe Ratio in the Galactic Cosmic Rays Measured by the ATIC-2 Experiment*

Titanium is a rare, secondary nucleus among Galactic cosmic rays. Using the Silicon matrix in the ATIC experiment, Titanium has been separated. The energy dependence of the Ti to Fe flux ratio in the energy region from 5 GeV per nucleon to about 500 GeV per nucleon is presented.

Overall View of the JEM‐EUSO Instruments

JEM‐EUSO mission with a large and wide‐angle telescope mounted on ISS has been planned to open up “particle astronomy” through the investigation of extreme‐energy cosmic rays by detecting fluorescent and Cherenkov photons by air showers developed in the earth’s atmosphere. The JEM‐EUSO telescope consists of optical Fresnel lenses with a diameter of about 2.5 m, 300 k channels of MAPMT, frontend readout electronics, trigger electronics, and system electronics. An infrared camera and a LIDAR system will be used to monitor the earth’s atmosphere.

Scientific capabilities of SIFTER for discovering and monitoring gamma-ray bursts and active galactic nuclei

An exciting possibility for the GLAST main instrument is a scintillating fiber system where the properties of both a tracker and a calorimeter are combined in one type of detector module. This instrument provides all the detector capabilities required to achieve the science goals of the GLAST mission, at a substantially reduced cost compared to the baseline technology, and with the benefit of increased effective area and superior low energy angular resolution.