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A Measurement of Cosmic Ray Deuterium from 0.5-2.9 Gev/Nucleon G.A Nolfoe D

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A Measurement of Cosmic Ray Deuterium from 0.5-2.9 Gev/Nucleon G.A Nolfoe D A Measurement of Cosmic Ray Deuterium from 0.5-2.9 GeV/nucleon G.A Nolfoe .d 1, L.M. Barbier2, E.R. Christian2, A.J. Davis1, R.L. Golden . Hof5,M 4, K.E. Krombel2, A.W. Labrador6, W. Menn4, R.A. Mewaldt1, J.W. Mitchell2, J.F. Ormes2,1.L. Rasmussen Reimer. 7,O 3, S.M. Schindler . Simon1,M 4, S J. Stochaj5, R.E. Streitmatter2, W.R. Webber5 1 California Institute of Technology, Pasadena, California 91125 2NASA/Goddard Space Flight Center, Greenbelt, 20771MD 3Max-Planck-lnstitut fuer extraterrestrische Physik, Garching, Germany Universitat4 Siegen, Siegen, Germany 5New Mexico State University, Cruces,Las 88003NM 6 University of Chicago, Chicago, IL 60637 7Danish Space Research Institute, Copenhagen, Denmark Abstract. The rare isotopes 2H and 3He in cosmic rays are believed to originate mainly from the interaction of high energy proton heliud an s m wit galactie hth c interstellar medium unique Th . e propagation histor f thesyo e rare isotopes provides important constraint galactin so c cosmi sourcy cra e spectrmodeln o d their aan sfo r propagation within the Galaxy. Hydrogen and helium isotopes were measured with the balloon-borne experiment, MAX, which flew from Lynn Lake, Manitob n 1992 ai e energ Th . y spectru f deuteriumo GeV/nucleo2 m3. betweed an 5 n0. n measurey db experimenX theMA wels a tpreviousl s a l y published resultfroe same H 3 m th f seo instrument wil comparee b l d with prediction f cosmiso galactiy cra c propagation models observee Th . d compositio lighe th tf no isotope founs se i b o dt generally consistent wit predictione hth standare th f so d Leak Modex yBo l derive observationt fi o dt heavief so r nuclei. INTRODUCTION affecte fewey b d r nuclear destruction processes during propagation. These isotope alsy oma s provid tesea f o t Extensive observation cosmif so abundancey cra s over whether cosmic rays undergo continuous acceleratior no a wide range in energy help to form a comprehensive "reacceleration" during their passage through the Galaxy pictur f cosmio e y origi ra cpropagationd nan e th n I . (8). Hydroge heliud nan m isotopes have been measured simplest picture such as the standard Leaky Box Model, by the Isotope Matter-Antimatter Experiment (MAX) in- cosmic rays propagate withi Galaxe nth y influencey db strument over a wide range in energies extending to 2.9 the competing processes of nuclear interactions and es- GeV/nucleon (6) thin I . s paper presen e meaX w , -MA t cape fro e Galaxymth e lighTh .t isotopes, sucLi s ha surements of 2H as well as the previously published re- Be, B are significantly enhanced over solar system abun- sults of 3He (6) and compare these observations with pre- dances indicating that these elements are produced as sec- dictions from current propagation models. ondary or spallation products of primary C, N, and O ele- ments. Thus, the determination of the secondary/primary INSTRUMENT AND FLIGHT ratio provides a measure of the amount of material tra- versed by primary cosmic rays during propagation. At 1 MAX was designed to measure antiprotons and the GeV/nucleon, the mean free pathlength for escape from light isotopes ove widra e energy range. IMAX employed Galaxe th g/cm0 1 founs yXi e ~ 2 b . o dt a combinatio f detectorno s includin gsuperconductina g The isotopes 2H and 3He are of particular interest as magnetic spectrometer (2) time-of-fligha , t (TOP) sys- these isotopes are considered to be interaction products of tem, scintillation counters (S1,S2), and large-area aero- more th e abundant hydroge heliud nan m nuclei addin I . - gel Cherenkov detectors. Particle identification is accom- tion, the abundance of 2H and 3He can, in principle, pro- plishe measuriny db particle gth e velocity (3, charg, eZ vide a more sensitive determination of the escape path- and rigidity R (momentum/charge). For further details on length than heavier cosmic ray nuclei, since H and He are the performance of the IMAX instrument see (1). CP528, Acceleration and Transport of Energetic Particles Observed in the Heliosphere: ACE 2000 Symposium, edited by Richard A. Mewaldt, et al. © 2000 American Institute of Physics l-56396-951-3/00/$17.00 425 Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp 2 4 0 2. 5 1. 0 Rigidity (GV) Mass (amu) FIGURE 1. IMAX mass separation for Z=l, (3=1 particles along with the corresponding mass histograms in two separate energy intervals mase Th determines .si d between 2.5-2.860 GeV/nucleon usin velocite gth y obtained fro Cherenkoe mth v counterse Th . thick solid lines represen instrumenn a t t simulation, whil thie eth n solid lines refe measureo t r d distributions. IMAX fle Julyn wi , 1992 from Lynn Lake, Manitoba, from the interaction of protons and helium in the 5 g/cm2 Canada. The flight lasted 16 hours at float including a residual atmosphere abov instrumente eth attenuae Th . - long ascent of ^7 hours. IMAX reached a maximum float tion of 2H within the instrument and atmosphere is de- g/cm5 ( residuaf m altitud2o k 6 3 f elo atmosphere)e Th . termined using a universal parametrization for the total geomagnetic cutoff varied betwee nLynt a 0.3 V n5 G Lak e reaction cross section given by Tripathi et al. (10). This an dPeact a 0.6 V 3eG River, Alberta. model is in good agreement with current measurements inelastie foth r c cross section 2f H+ so 3 d He+pan p reac- DATA ANALYSIS tions (10), (11). IMA meaa s Xnha grammag- in e th n ei strument of 13.8 g/cm2. The different materials encoun- IMAX event acceptee sar d base four-fola n do d coin- tered durin particle'e gth s traversal throug IMAe hth - Xin cidence betwee photomultipliee nth r signal- s froop e mth strumen accountee tar thin i sr dcalculationfo . bottod positscintillatorsan P p mTO to e e sideth e f so Th . selection criteria employe obtaio dt ncleaa n samplef o charge one particles are discussed in (1). °'08 : Atmospheric Model (Papini 1993) --- 0.06 r Figure 1 shows the isotopic separation for charge particlee on s usin (3-rigidite gth y technique corree Th . - 0.04 sponding mass histogram representativo tw n si e energy 0.02 200-80: V 0Me intervals are shown in Figure 1, where the velocity in 0.00 0 10 20 30 highee th r energy interva s obtainei l d fro aerogee mth l Residual Atmosphere (g/cm2) Cherenkov counter. Due to the non-gaussian behavior 0.060 Atmospheric Model (Papini 1993) ___ distributionse oth f simulatioa , s developenwa - ac o dt 0.045 curately model the instrument response (6),(7). The sim- 0.030 ulation takes into account evenn a eveny n b to , t basis, 0.015 the actual spectral incomine shapth f eo g particlese th , 0.000 800-1200 MeV timinP TO g resolution photoelectroe th , n statistical fluc- 0 10 20 30 tuation 8-rad an s y contribution Cherenkoe th o st v light Residual Atmosphere (g/cm2) yield t alsI . o takes into accoun spatiae tth l resolutiod nan rigidity resolution of the tracking system, and the effects FIGURE 2. IMAXH/H as a function of atmospheric depth 1 of multiple coulomb scattering. The simulation results separato intw e energy intervals mode2 e Th .f Papin o l nors i i - showe ar thice Figurn th i ks a soli1 e d lines; . malize IMAe th o dt X dat discusses aa text.e th n di 2 RESULTS contributioe Th n from atmospheric secondars i H y determined from calculation Papiny . b s(4),(5)al t e i . In orde determino rt fluf e deuteriuo f e th x o p to e th mt a Several other calculations have been performed includ- atmospheree th necessars i t i , accouno yt nuclear tfo - rin ing those of Webber (12) and Lijowski et al. (3). Current teraction losses withiinstrumene th n ni atmospherd an t e calculations differ by as much as a factor of 2-3 where as well as for the secondary population of 2H produced the differences are most likely due to the assumed pri- 426 Downloaded 02 Oct 2007 to 131.215.225.176. Redistribution subject to AIP license or copyright, see http://proceedings.aip.org/proceedings/cpcr.jsp mary proton and helium spectra and the assumed interac- growth curve consistene ar s t with Papini's atmospheric tion cross sections orden I . betteo rt r constrai estir nou - secondary calculation at solar minimum conditions. On contributioe matth f eo f secondarno obtaie w e , nth H y 2 the other hand, the BESS secondary calculations result 2H/1H ratio as a function of depth in the atmosphere dur- in fluxe factoa s f ~o r2 lower, close Papini'o t r s solar ing IMAX's long ~7 hour ascen floao t t altitudes. Fig- maximum calculation (11). Table 1 lists the IMAX mea- ure 2 shows the 2H/1H ratio at seven separate depth instrumene th f so p d to tan e surementfluth H 2 t xa e th r sfo atmospheree inth dashee Th . d curvcalculatioe th s ei n atmosphere. by Papini (4) for the production of secondary deuterium in 5 g/cm2 residual atmosphere during solar minimum Table 1. 2H Flux at the top of the instrument (TOI) and conditions Papine Th .
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