24th International Conference on Nuclear Tracks in Solids Bologna, 1-5/9/2008 Fragmentation cross sections of Fe26+, Si14+ and C6+ ions of 0.310 A GeV on polyethylene, CR39 and aluminum targets M. Giorgini* on behalf of the Bologna group *Bologna University and INFN

MOTIVATIONS An accurate description of the fragmentation of medium and high Z ions is important for the following reasons : (i) to understand the effects of medium Z cosmic rays on humans in space (ii) for shielding in space and in accelerator environments (iii) for radiotherapy and radioprotection purposes (iv) to confirm the simulated data from the FLUKA* and RQMD** (Relativistic Quantum Molecular Dynamics) Monte Carlo codes * hep-ph/0306267 ** J. Phys. Conf. Ser. 41 (2006) 519

EXPERIMENTAL PROCEDURE Survived beam Fragments Incident beam CR39 Detectors Target Beam : Fe26+ (E = 0.3 , 0.41 , 1.0 , 3.0 , 5.0 AGeV) Si14+ (E = 1.0 , 3.0 , 5.0 AGeV) C6+ (E = 0.29 AGeV) CR39 sheets : area 11.5 × 11.5 cm2 thickness 0.65 mm Targets : CH2 , Al , CR39 thickness 1 mm After exposure, the CR39 sheets were etched in 6N NaOH aqueous solution at 70 °C for 30 h

AUTOMATIC MEASUREMENTS Automatic image analyzer ELBEK (A. Noll et al., Nucl. Tracks Radiat. Meas. 15 (1988) 265) The base area, eccentricity and brightness are measured for each track Tracking : the trajectory of each ion is followed through the stack 5 AGeV Fe26+ 1 AGeV Fe26+ Number of events Number of events Average base areas for tracks present in at least 2 out of 3 measured CR39 sheets located before the target Average base areas for tracks present in at least 2 out of 3 measured CR39 sheets located after the target

TOTAL FRAGMENTATION CROSS SECTION stot = AT ln(Nin/Nout) rT tT NAV AT = mass number of the target rT = density of the target tT = thickness of the target NAV = Avogadro's number Nin = number of incident ions before the target Nout = number of incident ions after the target ZT = atomic number of the target Ap = mass number of the beam ro = 1.31 fm bo = 1.0  = 1.57  = 1.9

FRAGMENTATION CROSS SECTIONS OF Fe26+ ON CH2 , CR39 AND Al Fe26+ on Al Fe26+ on CH2 [ Phys. Rev. C 56 (1997) 388 ] Total cross section (mb) Energy (AGeV) Target AT stot (mb) 10 CH2 4.7 1147 ± 97 CR39 7.4 1105 ± 360 5 1041 ± 130 1170 ± 470 3 904 ± 140 1166 ± 67 1 1105 ± 60 1113 ± 176 Al 27 1870 ± 131 0.41 948 ± 54 1285 ± 245 1950±126 0.30 949 ± 61 1174 ± 192 2008±144 The quoted uncertainties are statistical standard deviations

FRAGMENTATION CROSS SECTIONS OF Si14+ ON CH2 , CR39 , Al , C e H Si14+ on Al Si14+ on CH2 Si14+ on CR39 [ Phys. Rev. C 39 (1989) 2222 ] [ Radiat. Meas. 34 (2001) 237 ] [ Nucl. Phys. A 784 (2007) 341 ] Total cross section (mb) Energy (A GeV) Target σtot (mb) 5 CH2 757 ± 168 3 Al 1533 ± 133 1 CR39 1113 ± 176 H 483 ± 76 694 ± 70 C 1117 ± 62 1397 ± 138 The quoted uncertainties are statistical standard deviations

DATA-PREDICTIONS COMPARISON [ Phys. Rev. C 56 (1997) 388 ] Total cross section (mb) Target mass AT 0.29 A GeV C Present work Total cross section (mb) [ Phys. Rev. C 39 (1989) 2222 ] [ Nucl. Phys. A 784 (2007) 341 ] [ Phys. Rev. C 66 (2002) 014609 ] Target mass AT

PARTIAL CHARGE CHANGING CROSS SECTIONS Average base areas for tracks present in at least 2 out of 3 measured CR39 sheets located after the target Charge resolution sZ ~ 0.2e

PARTIAL CHARGE CHANGING CROSS SECTIONS DZ sDZ (mb) -1 - 293 ± 18 -2 338 ± 11 177 ± 12 -3 285 ± 11 123 ± 11 -4 252 ± 10 122 ± 11 -5 249 ± 10 62 ± 8 -6 197 ± 9 117 ± 11 -7 168 ± 8 83 ± 9 -8 132 ± 7 90 ± 10 -9 175 ± 8 -10 107 ± 7 -11 152 ± 6 -12 105 ± 8 -13 103 ± 6 -14 81 ± 6 -15 80 ± 6 -16 50 ± 4 -17 76 ± 5 -18 86 ± 6 Partial fragmentation charge changing cross sections for 1 AGeV Si14+ and 1 AGeV Fe26+ ions on the CH2 target The quoted uncertainties are statistical standard deviations

CONCLUSIONS The total fragmentation cross sections for Fe26+, Si14+ and C6+ ion beams of 0.3  10 A GeV energies on polyethylene, CR39 and aluminum targets were measured using CR39 nuclear track detectors The total cross sections for all the targets and energies used in the present work do not show any observable energy dependence There is a dependence on target mass. The highest cross section values, observed for Al targets, are mainly due to the contribution of electromagnetic dissociation The present data of total fragmentation cross sections are in agreement with similar experimental data in the literature The presence of well separated fragment peaks allowed the determination of the partial fragmentation cross sections. On the average the partial cross sections decrease as the charge change DZ increases The measured cross section data indicate that the CR39 detector can be used effectively for studies of the total and partial charge changing cross sections, also in comparison with active detectors