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50 Annual Report 1999 PL0001489

2.12 Radiative Capture by Fast 3He++ by D.Cbmielewska, P.Rymuza, Z.Sujkowski, Y.Fujita0, H.Fujita", A.Akimune2', M.Fujiwara2), T.Inomata2), A.Tami3), M.Tanaka.4)

The photon spectrum originating from the radiative n,=1500 extends the systematics by four orders of electron capture, REC, by 150 MeV/amu 3He++ ions magnitude. impinging on thin carbon foils has been observed in 3 + + The REC photons may be an observable of coincidence with He ions. The He particles were astrophysical relevance. In particular, the photon recorded with the Grand Raiden spectrometer of the spectrum in 100 keV energy region recorded by the RCNP, Osaka, set at 0° with respect to the beam. This space based gamma-ray observatories may carry and the measured dependence of the total capture to information on the intergalactic primordial helium, stripping cross-section ratio versus the target which, if totaly ionized, is invisible for the usual tbickness, Fig. 1, permit to determine independently optical observations. the values of the cross-sections for REC, for the non- radiative electron capture, NREC, and for the electron 1.0E-KK :.::.-~*^t + stripping from He , correspondingly: cREC = (54±20) ub, 0NREC = (40+20) ub, oion = (375±80) kb.

150MeV/u3He->C 3.5x10"" -i

:) 3.0x10' - T

2.5x10" - ?o 2,0x10" - /A '' 'o 1.5x10"- I •g 1.0x10"-

1 10 100 1000 10000 5.0x10" - • experiment Adiabatic'rty Parameter c 0,0- Itieory a =115jib, a =20^b. a =435kb Fig.2 Universal curve for the K REC cross-section dependence on 10 100 1000 the adiabaticity parameter. Target Thickness (fig/cmJJ Fig. 1 Dependence of th1 e 33»HeT +H/3He++ singles yield ratio on the carbon target thickness. [1] Th.Stoehlker et al., Phys. Rev. A51(1995) 2098

Fig. 2 shows the systematics of the measured 11 Department of Physics, Osaka University, values for oREC plotted versus the adiabaticity Toyonaka, Osaka 560, Japan 2 2) parameter r\ = (Vp/ve) , where vp and ve are the RCNP, Osaka, Japan velocities of the projectile and of the captured electron 3) Department of Physics, Kyoto University, Kyoto in the bound state of the projectile, respectively. The 606, Japan data for r|<10 are from [1]. The present point at 4) Kobe Tokiwa Jr College, Nagata 653, Japan

2.13 Monte Carlo Simulations for the ANKE Spectrometer by I.Zychor for the ANKE Collaboration (IKP Jiilich ) PL0001490

The Monte Carlo code GEANT [1] is used to address, provides programs for the momentum simulate experiments with the ANKE spectrometer. reconstruction based on information from multiwire The program is located under the following address: proportional chambers (MWPC ). http://ikpd 15.ikp.kfa-juelich.de:8085/doc/Anke.html. One of the major parts of the ANKE-GEANT Three files: field_maps.tar.gz, input_ntuple_roc.tar.gz program is the geometry package which has two main and iza_geant.tar.gz are necessary for this purpose. functions: (1) define, during the initialisation of the The main program must be adjusted to the problem program, the geometry in which the particles will be analysed by the user. Information about input files for tracked, (2) communicate, during the event processing the ANKE-GEANT code can be found in manuals phase, to the tracking routines the information for the available in the iza_geant.tar.gz file. A file transport of the particles in the geometry which has iza_momenturn.tar, located under the above given been defined. DEPARTMENT OF NUCLEAR SPECTROSCOPY AND TECHNIQUE 51

The ANKE-GEANT geometry package describes GEANT original output files, prepared by calling precisely a full spectrometer: magnets, vacuum corresponding procedures [1]. One event consists of chambers, target chambers, detector systems etc. The several tracks and more than one particle can appear in real set-up is divided into parts easily converted into it. Typical parameters of the particle track, like time of shapes supplied by GEANT. Preparation of flight, energy loss and path length for each detector, description of the ANKE geometry for the Monte are stored. These data can be written in the same Carlo code was a time consuming task, which has format as measured data. So, the same data analysis started from measurements of dimensions and program may be used for experimental and simulated positions of all ANKE elements. Necessary data are data. already placed in the ANKE WWW page and in a Simple response functions for scintillators are close future will be available from the database. implemented in the ANKE-GEANT program and Measured dimensions and positions of all elements of placed in the ntuple-like file called the ANKE set-up are then used to calculate shape anke_geant_output.ntuple. parameters and positions of volumes according to the Monte Carlo simulations are very useful to GEANT convention. For the moment these determine a detector acceptance, estimate background, conversions are done in the main part of the ANKE- understand measured particle spectra. These GEANT program (written in FORTRAN). calculations are also necessary for identification of All physical phenomena (pair production, particles and calculations of their energy losses. The Compton scattering, photoelectric effect, Rayleigh Monte Carlo simulations are the only method to scattering, bremsstrahlung, hadronic process, reconstruct the momenta of ejectiles, from measured annihilation, 8-rays, muon nuclear interaction, hits in MWPC's for the two body calibration reactions. , decay in flight, energy loss, multiple Calculated and measured parameters are used to verify scattering, Cerenkov photon generation, Cerenkov positions of set-up elements, or even to find correct light absorption, synchrotron radiation generation, values (e.g. by comparing the simulated and different energy fluctuation models) can be switched experimental hit distributions in MWPC's). on or off by the user. The user must choose values of parameters controlling these processes. [1 ] GEANT3 Manual, CERN Program Library Long For the description of the magnetic field in the Writeup W 5013 ( October 1994 ) space occupied by the ANKE facility the measured [2] MAFIA, The MAFIA Collaboration field maps are used in combination with three [3] S.Barsov et al., "Dipole Field Characterisation by dimensional field calculations made with the MAFIA Floating Wire and Field Map Ray Tracing", Proc. code [2]. The MAFIA calculations are checked by 16th Int. Conf. on Magnetic Technology, Ponte comparison with the floating wire measurements [3]. Vedra Beach (USA), Sept.26 - Oct.2. 1999 Full information about events can be obtained either from special files described in manuals or from PL0001491 2.14 Spin-Flip Transitions in Radiative Electron Capture into Bare uranium Ions by T.Ludziejewski, Th.StohIkerU), H.F.Beyer2), F.Bosch2), J.Eichler3), B.Franzke2), S.Hagmann4), A.Kramer1>2), C.Kozhuharov2', J.Lekki6', D.Liesen2), P.H.Mokler2), Z.Stachura5', P.Swiat6', and A.Warczak6)

Photoionization is one of the most important inclusion of terms beyond dipole in a multipole interaction processes between radiation and matter. expansion of the photon field, results in a break-down Recently, it has been demonstrated that photo- of symmetry around 90° of the REC angular ionization can best be studied via its time inverse distribution. Surprisingly, deviations from sin20 reaction - the radiative electron capture (REC) distribution, turned out to be rather unimportant at ion occurring in ion- collisions [1]. For REC into the energies up to 300 MeV/u and nuclear charges up to ^-states of bare non-relativistic ions, the complete Z=50 or 70 [3]. However, a significant cross section at cancellation between retardation effects and the forward angles has been predicted for REC into the K Lorentz transformation occurs, leading to the classical shell of bare uranium (Z=92) at the same collision sin2G term in the angular distribution. In particular, energy, and shown to be a unique signature of spin-flip photon emission at 0° is forbidden by angular transitions [2]. momentum conservation law, unless a magnetic spin- Here, we report the first experimental study of a flip transition accounts for the spin of the emitted complete photon angular distribution for radiative photon [2]. For very high-Z systems, relativistic effects electron capture into the K shell of a bare high-Z ion become important and require the exact theoretical (uranium, Z=92). Our measurement conducted at the treatment, both in terms of electron wave-functions internal gas-jet target of the ESR Storage Ring at GSI used and the interaction potential. In particular, the Darmstadt, encompasses laboratory observation angles