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Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.

The most recent measurements by the Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) satellite of ultra-heavy cosmic ray isotopic and elemental abundances will be presented. A range of isotope and element ratios, most importantly Ne-22/Ne-20, Fe-58/Fe-56, and Ga-31/Ge -32 show that the composition is consistent with source material that is a mix of approx 80% ISM (with Solar System abundances) and 20% outflow/ejecta from massive stars. In addition, our data show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to an approx 80%/20% mix rather than pure ISM, that the refractory and volatile elements have similar slopes, and that refractory elements are preferentially accelerated by a factor of approx 4. We conclude that these data are consistent with an OB association origin of GCRs.

We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 <= Z <= 28 in the energy range approx. 50-550 MeV / nucleon. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than approx. 7%, and the relative abundances changed by less than approx. 4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2sigma, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple "leaky-box" galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

The ENTICE experiment is one of two instruments which make up the HNX mission. The experimental goal of ENTICE is to measure with high precision the elemental abundances of all nuclei with 10<=Z<=82. This will enable us to distinguish between possible injection mechanisms for the galactic cosmic ray accelerator such-as those dependent upon volatility or first ionization potential, and to study the mix of nucleosynthetic processes that contribute to the galactic cosmic ray source. The ENTICE experiment utilizes the dE/dx-C method of charge determination and consists of silicon dE/dx detectors, Cherenkov detectors with two different refractive indices, and a scintillating fiber hodoscope. The geometrical factor of the instrument is 8m2.sr. We will present a description of the instrument and its expected performance based on beam tests and a balloon flight of a prototype instrument.

The ENTICE experiment is one of two instruments that make up the HNX mission. The experimental goal of ENTICE is to measure with high precision the elemental abundances of all nuclei with Z between 10 and 82. This will enable us to determine if the injection mechanism for the cosmic ray accelerator is controlled by FIP or Volatility and to study the mix of nucleosynthetic processes that contribute to the galactic cosmic ray source. The ENTICE experiment utilizes the dE/dx-C method of charge determination and consists of silicon dE/dx detectors, Cherenkov detectors with two different refractive indices, and a fiber hodoscope. We will describe the instrument and its performance based on beam tests of a prototype instrument.

The Large Isotope Spectrometer for Astromag (LISA) is an experiment designed to measure the isotopic composition and energy spectra of cosmic rays for elements extending from beryllium through zinc. The overall objectives of this investigation are to study the origin and evolution of galactic matter; the acceleration, transport, and time scales of cosmic rays in the galaxy; and search for heavy antinuclei in the cosmic radiation. To achieve these objectives, the LISA experiment will make the first identifications of individual heavy cosmic ray isotopes in the energy range from about 2.5 to 4 GeV/n where relativistic time dilation effects enhance the abundances of radioactive clocks and where the effects of solar modulation and cross-section variations are minimized. It will extend high resolution measurements of individual element abundances and their energy spectra to energies of nearly 1 TeV/n, and has the potential for discovering heavy anti-nuclei which could not have been formed except in extragalactic sources.

An analysis is presented that, for the first time, systematically normalizes the data from the HEAO 3 heavy nuclei experiment on the cosmic-ray abundances of all the elements heavier than germanium to that of iron. In the range of atomic number Z from 33 to 60, the analysis yields abundances of odd-even element pairs. The abundances are consistent with a cosmic-ray source having a composition similar to that of the solar system, but subject to source fractionation correlated with the first ionization potential (FIP) of each element. For Z greater than 60, the analysis yields abundances of element groups. For these heaviest nuclei, we find an enhancement of the abundance of the platinum group, elements with Z of 74-80, relative to that in propagated solar system source, and a corresponding increase in the abundance of the largely secondary elements in the 62-73 range. These abundances suggest that there is an enhancement of the r-process contribution to the source nuclei in the Z greater than 60 charge region. Over the entire region of charge, standard leaky box models of propagation satisfactorily model secondary production.

Current work on the abundances of the ultraheavy elements in the cosmic radiation, i.e., those with Z greater than 30 is reviewed. Those abundances are compared with predictions based on propagation and fractionation of elemental abundances from various assumed sources of the cosmic rays. Striking similarities are found between the solar system and the cosmic ray source abundances for those elements with Z values between 32 and 60. For elements with Z greater than 60, there appears to be a substantial enhancement in the abundances of elements synthesized in the r-process.

Results from the Heavy Nuclei experiment on HEAO 3 are used to determine the primary abundances of Ni and Fe. Ni and Fe are found to have nearly constant relative abundances over the interval of 10 to about 500 GeV per amu. Individual secondary elements derived principally from interactions of primary Fe nuclei are shown to display a power-law decrease in relative abundance up to about 150 GeV per amu. Ar/Fe and Ca/Fe ratios of 2.6 + or - 0.7 percent and 8.8 + or - 0.7 percent, respectively, are found, confirming a fractionation of source abundances in which elements with high values of the first ionization potential are depleted relative to those with low first ionization potential.

The HEAO-3 Heavy Nuclei Experiment has measured abundances of elements from Ar-18 to U-92 in the cosmic rays. The results on the ultraheavy elements, those with atomic numbers greater than 30, indicate that the source of the cosmic rays contain a mixture of r-process and s-process material similar to that found in the solar system. This result is at variance with previous indications that the sources are greatly enhanced with freshly synthesized r-process material. Apparent discrepancies between the results and the accepted solar-system abundance have led to a reexamination of data on photospheric abundances of Ge and Pb, resulting in suggested reductions in their values.

An observation of the abundances of cosmic-ray lead and platinum-group nuclei using data from the HEAO-3 Heavy Nuclei Experiment (HNE) which consisted of ion chambers mounted on both sides of a plastic Cherenkov counter (Binns et al., 1981) is reported. Further analysis with more stringent selections, inclusion of additional data, and a calibration at the LBL Bevalac, have allowed the determination of the abundance ratio of lead and the platinum group of elements for particles that had a cutoff rigidity R(c) 5 GV. The observed ratio for Pb/Pt is distinctly lower than that predicted by any of the standard models for cosmic ray sources. It is possible that the difference is not an indication that the cosmic ray source composition is greatly different from that of the solar system, but rather that there is less Pb in the solar system and in the r-process than is assumed in the standard models.

Elemental, isotopic, and antiproton abundances in cosmic ray sources are examined. The elemental abundances for very rare elements with atomic numbers (Z) greater than 30, for individual elements with Z less than 33, and for even-Z elements with Z less than 60 are compared with elemental abundances in the solar system. The effects of nucleosynthesis of the material and the cosmic ray acceleration process on the abundances of elements is discussed. It is observed that the cosmic ray sources differ in composition from the solar system; however, the abundances are generally the same. The observations of the cosmic ray antiprotons are described.

The HEAO-3 Heavy Nuclei Experiment is composed of ionization chambers above and below a plastic Cerenkov counter. The energy dependence of the abundances of elements with atomic number, Z, between 18 and 28 at very high energies where they are rare and thus need the large area x time are measured. The measurements of the Danish-French HEAO-3 experiment (Englemann, et al., 1983) are extended to higher energies, using the relativistic rise of ionization signal as a measure of energy. Source abundances for Ar and Ca were determined.

The Heavy Nuclei Experiment on (HEAO-3) high energy astronomy observatory 3 uses a combination of ion chambers and a Cerenkov counter. During analysis, each particle is assigned two parameters, Z sub c and Z sub i, proportional to the square roots of the Cerenkov and mean ionization signals respectively. Because the ionization signal is double valued, a unique assignment of particle charge, Z, is not possible in general. Previous work was limited to particles of either high rigidity or low energy, for which a unique charge assignment was possible, although those subsets contain less than 50% of the total number of particles observed. The maximum likelihood technique was used to determine abundances for the complete data set from approx. 1.5 to approx. 80 GeV/amu.

The LBL Bevalac for the Heavy Nuclei Experiment on HEAO-3, compared the response of a set of laboratory ionization chambers to beams of 26Fe, 36Kr, 54Xe, 67 Ho, and 79Au nuclei at maximum energies ranging from 1666 MeV/amu for Fe to 1049 MeV/amu for Au. The response of these chambers shows a significant deviation from the expected energy dependence, but only a slight deviation from Z sq scaling.

The ratio of cosmic ray source abundance to solar-system abundance was examined for individual elements. Correlations of these ratios with first-ionization potential (FIP) and the expected mass-to-charge ratio (A/Q) of the elements in a million-degree plasma are analyzed. The FIP correlation was examined and it is shown that the correlation is affected by the choice of C2 or C1 chondritic meteorites as the solar-system standard for comparison. An A/Q correlation is suggested as a consequence of the shock acceleration model in the hot interstellar medium. The correlations are presented.

The scintillating optical fiber isotope experiment (SOFIE) is a Cerenkov-dE/dx-Range experiment which was developed initially for balloon flight to study the isotopic composition of cosmic rays in the iron region. The electronic range and hodoscope detectors use scintillating optical fibers to image the tracks of stopping charged particles and to determine their trajectory. The particle range is determined and used together with a Cerenkov measurement to determine the mass of the stopping particle. Preliminary results of a Bevalac calibration performed in August, 1984 with a prototype of the balloon flight instrument, to study the measurement precision in range and trajectory which could be attained with this detector are described.

The results of a new balloon borne cosmic ray detector flown from Palestine, TX in Sept., 1982 are discussed. The exposure of 62 square meter-ster-hr is sufficient to prove the concept of using gas ionization chambers as energy measuring devices in the relativistic rise region. The abundances, relative Fe-26, of the pure secondaries Cr-22 and Ti-24, the pure primary Ni26, and the mixed primary and secondary Ca-20 between 6 and 70GeV/amu were measured.

Observations of the abundances of elements of charge 62 or Z or = 73 in the cosmic radiation from the HEAO-3 Heavy Nuclei Experiment (HNE) are discussed. These elements, having solar, and presumably source, abundances much less than the heavier Pt and Pb groups, are expected to be largely products of spallation. Thus they are indicators of the conditions prevailing during the propagation of cosmic rays. The abundances have changed from those reported previously due to a different data selection. This results in better charge resolution and in a higher mean energy for the particles. All the particles included were required to have had a cutoff rigidity R sub c 5 GV. This allowed the charge determination to be based solely on the Cherenkov measurement.

Over the past few years, the HEAO-3 measurements of the abundances of ultra-heavy cosmic ray nuclei (Z 26) at earth have been analyzed. In order to interpret these abundances in terms of a source composition, allowance must be made for the propagation of the nuclei in the interstellar medium. Vital to any calculation of the propagation is a knowlege of the total and partial interaction cross sections for these heavy nuclei on hydrogen. Until recently, data on such reactions have been scarce. However, now that relativistic heavy ion beams are available at the LBL Bevalac, some of the cross sections of interest can be measured at energies close to those of the cosmic ray nuclei being observed. During a recent calibration at the Bevalac of an array similar to the HEAO-C3 UH-nuclei detector, targets of raphite (C), polyethylene (CH2), and aluminum were exposed to five heavy ion beams ranging in charge (Z) from 36 to 92. Total and partial charge changing cross sections for the various beam nuclei on hydrogen can be determined from the measured cross sections on C and CH2, and will be applied to the propagation problem. The cross sections on Al can be used to correct the abundances of UH cosmic rays observed in the HEAO C-3 detector for interactions in the detector itself.

Over the past few years, the HEAO-3 measurements of the abundance of ultra-heavy cosmic ray nuclei (Z 26) at Earth were analyzed. In order to interpret these abundances in terms of a source composition, allowances must be made for the propagation of the nuclei in the interstellar medium. Vital to any calculation of the propagation is a knowlege of the total and partial interaction cross sections for these heavy nuclei on hydrogen. Until recently, data on such reactions have been scarce. The semi-empirical formalism of Silberberg and Tsao were relied upon to predict the partial cross sections. However, now that relativistic heavy ion beams are available at the LBL Bevalac, some of the cross sections of interest can be measured at energies close to those of the cosmic ray nuclei being observed.

An observation of the abundances of cosmic-ray lead and platinum-group nuclei using data from the HEAO-3 Heavy Nuclei Experiment (HNE) which consisted of ion chambers mounted on both sides of a plastic Cerenkov counter is reported. Further analysis with more stringent selections, inclusion of additional data, and a calibration at the LBL Bevalac, have allowed obtaining the abundance ratio of lead and the platinum group of elements for particles that had a cutoff rigidity R sub c 5 GV.

The Heavy Nuclei Experiment on HEAO-3 uses a combination of ion chambers and a Cerenkov counter. During analysis, each particle is assigned two parameters Z sub c and Z sub l proportion signal is double valued, a unique assignment of particle charge, Z, is not possible in general. Previous work was limited to particles of either high rigidity or low energy, for which a unique charge assignment was possible, although those subsets contain less than 50% of the total number of particles observed. The use of the maximum likelihood technique to determine abundances for the complete data set from approximately 1.5 to approximately 80 GeV/amu is studied.

Observations of the abundances of elements of charge 62 or = Z or = 73 in the cosmic radiation from the HEAO-3 Heavy Nuclei Experiment (HNE) are discussed. These elements, having solar, and presumably source, abundances much less than the heavier Pt and Pb groups, are expected to be largely products of spallation. Thus they are indicators of the conditions prevailing during the propagation of cosmic rays. The abundances have changed from those reported previously due to a different data selection. This resulted in better charge resolution and in a higher mean energy for the particles. All the particles included in this paper were required to have had a cutoff rigidity R sub c 5 GV. This allowed the charge determination to be based solely on the Cerenkov measurement.

The HEAO-3 Heavy Nuclei Experiment is composed of ionization chambers above and below a plastic Cherenkov counter. The energy dependence of the abundances of elements with atomic number, Z, between 18 and 28 were measured at very high energies where they are rare and thus need the large area x time of this experiment. The measurements of the Danish-French HEAO-3 experiment were extended to higher energies, using the relativistic rise of ionization signal as a measure of energy, and determine source abundances for Ar and Ca.

As part of a recent calibration at the LBL Bevalac for the Heavy Nuclei Experiment on HEAO-3, the response of a set of laboratory ionization chambers were compared to beams of 26Fe, 36 Kr, 54Xe, 67 Ho, and 79 Au nuclei at maximum energies ranging from 1666 MeV/amu for Fe to 1049 MeV/amu for Au. The response of these chambers shows a significant deviation from the expected energy dependence, but only a slight deviation from Z squared scaling.

The ratio of cosmic-ray source abundance to solar-system abundance for individual elements is examined. In particular correlations of these ratios with first-ionization potential (FIP) and also with the expected mass-to-charge ratio (A/Q) of the elements in a million-degree plasma are examined. The FIP correlation were previously examined and shown that the correlation is affected by the choice of C2 or C1 chondritic meteorites as the solar-system standard for comparison. An A/Q correlation was suggested by Eichler and Hainebach as a consequence of their model of shock acceleration in the hot interstellar medium, and has been examined by Israel. These correlations are presented.

The elemental composition of the cosmic-ray source is different from that which has been generally taken as the composition of the solar system. No general enrichment of products of either r-process or s-process nucleosynthesis accounts for the differences over the entire range of ultraheavy elements; specific determination of nucleosynthetic contributions to the differences depends upon an understanding of the nature of any acceleration fractionation. Comparison between the cosmic-ray source abundances and the abundances of C1 and C2 chondritic meteorites suggests the possibility that differences between the cosmic-ray source and the 'standard (C1) solar system' may not be due to acceleration fractionation of the cosmic rays, but may be due instead to a fractionation of the C1 abundances with respect to the interstellar abundances.

The interaction mean-free-path of cosmic-ray iron in air has been determined by observing the change in flux as a function of atmospheric depth. A large detector and a large variation in altitude during the balloon flight result in a high precision measurement. The result is in agreement, though slightly larger than the mean-free-path deduced from the measurements of interactions of iron on different targets at the Bevalac accelerator.

The measured elemental composition of cosmic rays with charge Z from 16-28 as a function of atmospheric depth was compared with a propagation calculation including energy loss. The resulting composition at the top of the atmosphere has better precision than previously possible on balloon borne experiments, and agrees well with the only satellite data available in this charge range. The extrapolation method also provides checks on assumed cross-sections for interactions of cosmic rays in air.

The relative abundances of elements in the charge ranges of Z = 75-79 (platinum) and Z = 80-83 (lead) should be a sensitive indication of the contributions of the r- and s-processes in nucleosynthesis. Data from the HEAO 3 Heavy Nuclei Experiment are used to establish abundances, relative to iron, of these elements in the cosmic radiation, as well as the ratio of 'secondary' elements, in the Z = 62-74 range, to the primary lead-platinum elements. These results appear to suggest that either the source abundances are deficient in s-process elements or that they are not organized solely by first ionization potential. In addition, present propagation models can adequately represent the relative abundances of primary and secondary elements.

The HEAO-3 Heavy Nuclei Experiment measures cosmic-ray energy directly in the interval 400 to about 1200 MeV/amu. Geomagnetic cutoffs can also be derived up to about 15 GV. Preliminary rigidity spectra of various ultraheavy cosmic-ray elements relative to iron are presented.

An analysis is presented of 454 days of data from the Heavy Nuclei Experiment aboard the HEAO-3 satellite using an improved charge estimation algorithm is presented. A more precise normalization of Z = 32-42 abundances relative to iron is obtained, and more accurate detector response maps are used to recognize and reject a small class of events which was previously misidentified. The resulting abundances are in generally good agreement with solar system abundances with the first ionization potential (FIP) and with the Cameron solar system r-process (1982) with and without an applied FIP bias. The simplest interpretation of the results is that the cosmic ray source has solar system abundances modified by an FIP and/or volatility-dependent bias.

The cosmic-ray-source abundances inferred from HEAO-3 observation by the Heavy Nuclei Experiment for Z = 30-60 generally follow the correlation with first-ionization potential which has previously been observed for Z less than 30. However the low Ge abundance suggests that the elemental 'volatility' may be an organizing factor.

The HEAO-3 Heavy Nuclei Experiment has measured elemental abundances of ultraheavy cosmic rays near earth. The elements with atomic number (Z) in the intervals Z = 44-48 and Z = 62-74 arriving at earth are expected to have significant secondary components. However, their source abundances are unlikely to be low enough to warrant treating them as pure secondaries. The present results are consistent with solar system abundances modified for first ionization potential with possibly some enhancement of the r to s ratio.

Elements with even atomic number (Z) in the interval Z = 50-58 have been resolved in the cosmic radiation using the Heavy Nuclei Experiment on the HEAO-3 satellite. The observation that Sn-50 and Ba-56 are more abundant than Te-52 and Xe-54 indicates a substantial s-process contribution to the cosmic ray source. A significant abundance of Ce-58 provides further support for this finding.

The HEAO 3 detector of heavy cosmic-ray nuclei has observed one possible actinide nucleus and some 100 nuclei of the platinum-lead group of elements. The resulting upper limit of 3% for the abundance ratio of actinides to platinum-lead nuclides is significantly lower than previous results from other observations. This new limit is inconsistent with freshly synthesized, pure r-process sources for cosmic-ray nuclei in this charge interval but is consistent with a source having a composition similar to the solar system, or to aged r-process material. We observe no events with a charge greater than 96.

Preliminary results are reported from 430 days of exposure of the heavy nuclei experiment on the HEAO-3 spacecraft. These results are confined to the heavy nuclei with Z equal to or greater than 50 and emphasize the conclusions obtained on the relative numbers of actinides and heavy stable elements in the lead-platinum region. The extreme paucity of actinides found is inconsistent with the predictions of a cosmic ray source that is highly enriched in r-process material, but quite consistent with a source whose composition is similar to that of normal solar system material. An upper limit, at the 95 percent confidence level, is placed in the ratio of nuclei with Z equal to or greater than 88/(Z in the range from 74 to 87) of 0.03.

The instrumentation and results from the Heavy Nuclei experiment on the HEAO 3 satellite are described. Six independently analyzed dual-gap ionization chambers measured the energy loss of the cosmic rays while a Cerenkov counter with 8 independently analyzed photomultipliers viewed two sheets of Pilot 425 plastic in a white box. Trajectories of the cosmic ray nuclei were determined in multiwire ionization hodoscopes. Variations in abundances were observed to be imperfectly ordered in terms of the first ionization potential, and volatility was also ruled out as the controlling factor. A predicted drop in abundance after Ba-56 was found, along with another sharp fall above Pb-82. Only one actinide-type event was detected during the 14 mos of viewing, a result consistent with other findings but which testifies against r-process formation.

Individual elements in the cosmic radiation of even atomic number (Z) in the interval 26-40 have been resolved and their relative abundances measured. The results are inconsistent with a cosmic-ray source whose composition in this charge interval is dominated by r-process nucleosynthesis. The ratios of cosmic-ray source abundances to solar system abundances in this interval follow the same general correlation with first ionization potential as for the lighter elements, although there are deviations in detail.

The contribution of r-process and s-process nucleosynthesis to the Cameron (1980) solar system (SS) abundances for Z at least 33 has been derived. In the interval Z equals 34-40 HEAO-3 data extrapolated to the cosmic-ray source (CRS) fit the solar system mix better than r-process. In the interval Z between 26-40 the HEAO-3 results for CRS/SS follow the same general correlation with first ionization potential as for the lighter elements although there are deviations in detail.

The HEAO-3 experiment to study the heavy and ultraheavy nuclei in cosmic radiation is described. The array is double-ended and consists of three main elements. Two pressure chambers, filled with an argon-methane mixture at about 850 torr, each contain two x-y hodoscopes made of wires spaced 1 cm apart and three parallel plate ionization chambers. Between the pressure chambers is mounted a Cerenkov counter composed of two layers of Pilot 425 radiator looked at by eight photomultipliers. The instrument is designed to achieve a charge resolution of 0.3 charge units over the charge range 17-120, which requires a measurement accurate to 0.6 percent at Z = 100. Examination of selected data shows that the instrument has the intrinsic resolution needed.

Relative abundances of elements with Z values between 14 and 28 in the energy range from 870 to 1400 MeV/nucleon are reported, including Ni/Fe ? 0.050 + or - 0.004 and Co/Fe below 0.012 + or - 0.006. The Si/Fe ratio shows no major energy dependence, but the ratio of Fe-secondaries (Z values between 21 and 25) to Fe shows some variation, approximately consistent with the energy dependence of the fragmentation cross-sections.

The paper describes a Cerenkov detector system designed to obtain abundances and energy spectra of cosmic ray nuclei above charge 12 and above 350 MeV/nucleon. The detector system consists of three pulse ionization chambers, a Lucite Cerenkov counter and a plastic scintillation-counter hodoscope. The data analysis follows from the standard dE/dx-C technique. It is shown that by using the relativistic ionization rise, the resolution and pulse height corresponding to charged particles of Beta ? 1 in Cerenkov detectors can be determined. Least-squares-fit procedures are used to obtain area and time variations of detector response from flight data and to extract elemental abundances from data with charge resolution of roughly 0.3 charge units.

Detailed examination of the differential velocity spectra of Si and Fe observed near 3 GV geomagnetic cutoff and at much lower cutoff indicates that if the Si nuclei are primarily mass 28 then the data fit Iron 54 better than Iron 56.

Results are presented from two balloon flights of an ionization/Cerenkov detector system. Well-defined peaks at nickel (Z = 28) and zinc (Z = 30) yield abundances relative to iron (Z = 26) of 0.05 and 0.006, respectively. About sixty events observed in the interval yield abundances relative to iron similar to those of the standard solar-system.

Relative abundances of individual Iron-secondary elements have been measured using a balloon-borne 6.6 m ster ionization/Cerenkov detector system. The unusually large geometry factor and single-charge resolution yield empirical atmospheric attenuation curves for individual elements which combine with high statistics at float altitude to yield individual element abundances, extrapolated to the top of the atmosphere, with high precision. Results are presented for top-of-the-atmosphere abundances (relative to iron) of individual elements in the Z range 13-30.

The relative abundances of Fe, Co, Ni, Cu, and Zn in the cosmic rays have been measured using a large-area balloon-borne electronic detector system. The abundance ratios Ni/Fe and Zn/Fe are 5.0 + or - 0.2% and 0.06 + or - 0.01%, respectively. The Zn abundance is low (40%) compared with the Cameron (1973) (C1) solar system, and is best consistent with the solar system C2 meteorite abundances. The ratios Co/Fe and Cu/Fe, extrapolated to the top of the atmosphere, are 0.68 + or - 0.14% and 0.066 + or - 0.030% respectively; since charge peaks are not resolved at Co and Cu, these results are taken as upper limits of 0.8% and 0.1%, respectively. The Co upper limit is consistent with complete decay of Co-57 at the source and implies a lower limit of 2 years for the time between nucleosynthesis and acceleration of these nuclei.

A 6.6-sq m-sr electronic detector was employed on a 28-hour balloon flight to obtain abundances of nuclei of Z at least 30 in cosmic rays. A Zn abundance of Zn/Fe = (7 + or - 2) x 10 to the -4th is obtained. The abundances relative to iron of nuclei with Z between 30 and 40 are lower than in the solar-system abundances of Cameron (1973), but individual elements do seem to follow the trend of the solar system.