Durante, M.

Krämer, M.

Scifoni, E.

Wälzlein, C.

GSI Repository

Solid target extensions in TRAXC. Wa¨lzlein∗1,2, M. Kra¨mer1, E. Scifoni1, and M. Durante1,21GSI, Darmstadt, Germany; 2FIAS, Frankfurt, GermanyThe GSI track structure Monte Carlo (MC) codeTRAX [1], whose main purpose is to properly describe cre-ation and transport of low-energy electrons, has been fur-ther extended. TRAX is intended to be suitable for a vari-ety of different target materials and projectiles. In ion irra-diation the distribution of produced secondary electrons isdominated by energies below 100 eV. Therefore electronswith initial energies in this range are the most relevant forradiation damage.One of our goals is to reproduce the data from the GSIToroid experiment [2] to gain further insight on low-energyelectron creation and transport in solids. Therefore ourcross section database was extended to account for elec-tron induced excitations. Consideration of excitation re-duces the cut-off energy, below which electrons are con-sidered to be stopped, as no further cross sections for in-elastic interactions are available below. Cross sections forelectron induced ionization can be easily calculated for alltarget materials using a simplified formula based on binaryencounter theory according to Kim and Rudd [3]. With afew input parameters like the binding and kinetic energy ofelectrons in any target atom or molecule, we can easily ac-cess ionization cross sections. For electron induced excita-tion neither a complete database nor a simple model existswhich could calculate all desired cross sections. With theToroid experiment in mind we consider the target materialscarbon, nickel, silver and gold.CarbonThe cross section database for low energy electrons inci-dent on carbon has been extended to account for electronicexcitations. Collision strengths from a review of Suno [4]have been used to calculate cross sections for 21 individ-ual excitation channels. Considered are excitations from2s to 2p states (6 channels), 2p→3s (2 ch), 2p→3p (6 ch),2p→3d (5 ch) and 2p→2p (2 ch). Below ≈ 100 eV the ex-citation cross sections exceed the ionization cross sections.and below the ionization threshold (11.26 eV) excitationis the only source of energy deposition in our simulation.With the newly introduced excitation cross sections, thecut-off energy is reduced from 11.26 eV to 1.26 eV. Moredetails are given in [5].GoldWe consider 3 single excitation channels (6s-6p and 5d-6s excitations) by using experimental cross sections fromMaslov and Zatsarinny et al. [6, 7]. The cross sections were∗Work supported by Beilstein Institute (NanoBiC project).Work is part of HGS-HIRe.extrapolated to higher energies using the Bethe-Born ap-proximation [8]. We also consider plasmon excitation byusing the formula given by Quinn [9]. This reduces the cut-off energy from 9.23 eV to 2.7 eV. More details are givenin [10].Nickel and SilverFor excitations in Nickel and Silver we used the ACEcode [11] which is a collision code based on distorted wavemethods by Mann [12]. We account for 9(Ni) and 11(Ag)dielectric excitation channels. For Ni we have transitionswith energy losses down to 0.12 eV (4s-3d) and for Agdown to 3.28 eV (5s-5p).Figure 1: Energy dependent electron stopping power fortarget materials used in the Toroid experiment. The stop-ping powers were calculated using the ionization and exci-tation cross sections and the corresponding energy losses.References[1] M. Kra¨mer and M. Durante, Eur. Phys. J. D, 60 (2010) 195.[2] N. Lineva et al., NIM B 267 (2009) 891.[3] Y.K. Kim and E. Rudd, Phys. Rev. A 50 (1994) 3954.[4] H. Suno et al., At. Data and Nucl. Data Tabl. 92 (2006) 407.[5] C. Wa¨lzlein et al., Phys. Rev. E., submitted.[6] M. Maslov et al., Phys. Rev. A 77 (2008) 062711.[7] O. Zatsarinny et al., Phys. Rev. A 78 (2008) 042713.[8] G.W. Bransden et al., Int. J. Radiat. Biol. Stud. Phys. Chem.Med. 10 (1966) 317.[9] J.J. Quinn, Phys. Rev. 126(4) (1962) 1453.[10] C. Wa¨lzlein et al., Appl. Rad. and Isot., in press.[11] R.E.H. Clark et al., Manual LA-11436-M, Los Alamos Lab-oratory (1988).[12] J.B. Mann, At. Dat. Nuc. Data Tables 29 (1983), 407.GSI SCIENTIFIC REPORT 2012 HEALTH-51475

Solid target extensions in TRAX

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Solid target extensions in TRAX

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