W. K. H. Schmidt

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.

Energy Dependence of the Ionic Charge State Distribution During the November 1997 Solar Energetic Particle Event

3 Abstract. Ionic charge state distributions for a variety of species, such as C, O, Ne, Mg, Si and Fe were obtained with the Solar Energetic Particle Ionic Charge Analyzer (SEPICA) on ACE for the strongest of a series of energetic particle events after the November 4 and 7, 1997, flares. The capabilities of SEPICA allow a much more detailed analysis of the charge dis- tributions than previous instrumentation. Over the energy range from ≈ 0.2 to 1 MeV/Nuc a trend is observed that shows charge states increasing with energy, in particular for Mg, Si and Fe. In addition, for Fe a mixed charge state distribution with a distinct peak at lower charge states (10 - 14) is ob- served simultaneously with a tail reaching to charge states up to ≈ 20. This may be an indication of a mixture of different energetic particle populations. 1

A proposed X-ray focusing device with wide field of view for use in X-ray astronomy

Abstract A device is described that consists of a set of flat reflecting surfaces. At glancing incidence of X-rays of wavelength several A and longer, this device can be used for the focusing of a sizable portion of an intercepted beam of X-rays incident in parallel. Focusing is not perfect and the image size is finite. But a one-dimensional focusing device offers a wide field of view, up to a maximum of 2π. It appears practically possible to achieve an angular resolution of the order of one tenth of a degree. Two such systems in sequence, so as to form a double-focusing device, should offer a field of view of up to 100 square degrees at moderate angular resolution. It is proposed to use such devices in X-ray astronomy survey or monitor experiments.

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.

SMART-1 mission to the moon: Technology and science goals

Abstract SMART-1 is a technology demonstration mission for deep space solar electrical propulsion and Technologies for the Future. SMART-1 will be Europes first lunar mission and will contribute to developing an international program of lunar exploration. The spacecraft has been readied in April 2003 for a launch in summer 2003, as an auxiliary passenger to GTO on Ariane 5, to reach the Moon after 15 months cruise. SMART-1 will carry six experiments, including three remote sensing instruments that will be used during the missions nominal six months in lunar orbit. These instruments will contribute to key planetary scientific questions, related to theories of lunar origin and evolution, the global and local crustal composition, the search for cold traps at the lunar poles and the mapping of potential lunar resources.

A study of the properties of an ionization spectrometer with 10, 20.5 and 28 GeV/c incident protons

Abstract Results of calibration measurements of an ionization spectrometer with 10, 20.5 and 28 GeV/ c protons are presented. An ionization spectrometer has been employed in several successful balloon flights in combination with spark chambers and different target materials to study high energy cosmic rays. A brief description of the apparatus is given along with details of the balloon flights as well as the exposures at the Brookhaven AGS. The calibration measurements show that it is possible to measure the energy of high energy particles with an ionization spectrometer which is only three interaction lengths deep. A linear dependence has been found to exist between the primary energy and the mean of the measured ionization loss, as well as between primary energy and the mean of the maximum of the measured ionization loss for particles whose first interaction was in the spectrometer. However, this linear relationship does not hold for particles which undergo their first interaction in a target above the spectrometer. For incident protons which interact in the top layer of the spectrometer, the accuracy of the energy determination is +60% and −30%; +50% and −30%; +50% and −25%; at 10, 20.5 and 28 GeV/ c , respectively. An attempt has been made to simulate alpha-particle interactions in the spectrometer by using combinations of separate proton events. It is shown that the accuracy of the energy determination for these simulated alpha particles is +50% and −28%; +44% and −26%; +44% and −25%, respectively, for kinetic energies of 9, 19.5 and 27 GeV/nucleon.

Advanced Thin Ionization Calorimeter (ATIC) balloon experiment: expected performance

An advanced thin ionization calorimeter (ATIC) will be used to investigate the charge composition and energy spectra of ultrahigh energy primary cosmic rays in a series of long- duration balloon flights. While obtaining new high priority scientific results, this balloon payload can also serve as a proof of concept for a BGO calorimeter-based instrument on the International Space Station. The ATIC technical details are presented in a companion paper at this conference. Here we discuss the expected performance of the instrument based on a GEANT code developed for simulating nuclear- electromagnetic cascades initiated by protons. For simulations of helium and heavy nuclei, a nucleus-nucleus interaction event generator LUCIAE was linked to the GEANT based program. Using these models, the design of the ATIC detector system has been optimized by simulating the instrument response to particles of different charges over the energy range to be covered. Results of these simulations are presented and discussed.

Measurements of the development of cascades in a tungsten-scintillator ionization spectrometer☆

Abstract The response of a tungsten-scintillator ionization spectrometer to accelerated particle beams has been investigated. Results obtained from exposure of the ∼ 1000 g/cm 2 apparatus to 5, 10, and 15 GeV/ c electrons and pions as well as to 2.1 GeV/ nucleon 12 C and 16 O ions are presented. These results include cascade-development curves, fractions of the primary energy measured by the spectrometer, and resolutions of the apparatus for measuring the primary energies. The response of spectrometers having smaller depths than 1000 g/cm 2 was estimated by successively omitting signals from the downstream end of the modular apparatus. For 15 GeV/ c electrons, an average of ∼ 82% of the incident energy is measured by the apparatus with resolution (normal standard deviation) of ∼ 6%. For 15 GeV/ c pions, an average of ∼ 65% of the incident energy is measured with resolution of ∼ 18%. The energy resolution improves with increasing energy and with increasing depth of the spectrometer.

Advanced thin ionization calorimeter to measure ultrahigh energy cosmic rays

Abstract An Advanced Thin Ionization Calorimeter (ATIC) will be used to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 10 10 to >10 14 eV in a series of long-duration balloon flights. The totally active BGO calorimeter, 22 radiation length thick, will measure the electromagnetic energy ensuing from nuclear interactions in a one interaction length thick carbon target. Trajectory information will be obtained from the location of the cascade axis in the BGO calorimeter and in the segmented scintillator layers of the upstream carbon target. The highly segmented charge module comprised of scintillator strips, a silicon matrix, and a Cherenkov array will minimize the effect of backscattered particles on primary charge measurements. While obtaining new high priority scientific results, the ATIC balloon payload can also serve as a proof of concept, or engineering model, for a BGO calorimeter-based instrument on the International Space Station. We examine the added advantage of locating such an experiment for long durations on a platform such as the Space Station.