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24th International Conference on Nuclear Tracks in SolidsBologna, 1-5/9/2008

Fragmentation cross sections of Fe26+, Si14+ and C6+ ions of 0.310 A GeV on polyethylene, CR39 and aluminum targets

M. Giorgini* on behalf of the Bologna group*Bologna University and INFN

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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

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EXPERIMENTAL PROCEDURE

Survived beam

Fragments

FragmentsIncident beam

CR39 Detectors

Target

CR39 sheets : area 11.5 × 11.5 cm2

thickness 0.65 mm

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)

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

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AUTOMATIC MEASUREMENTSAutomatic 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

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

5 AGeV Fe26+

Nu

mb

er o

f ev

ents

Nu

mb

er o

f ev

ents 1 AGeV Fe26+

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TOTAL FRAGMENTATION CROSS SECTION

tot = AT ln(Nin/Nout) T tT NAV

AT = mass number of the targetT = density of the target tT = thickness of the targetNAV = Avogadro's numberNin = number of incident ions before the targetNout = number of incident ions after the target

ToPTEMDnucltot ZbAA 231312o )(r10

ro = 1.31 fmbo = 1.0 = 1.57 = 1.9

ZT = atomic number of the target Ap = mass number of the beam

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FRAGMENTATION CROSS SECTIONS OF Fe26+ ON CH2 , CR39 AND Al

Energy (AGeV) Target AT tot (mb)

10 CH2 4.7 1147 ± 97

10 CR39 7.4 1105 ± 360

5 CH2 4.7 1041 ± 130

5 CR39 7.4 1170 ± 470

3 CH2 4.7 904 ± 140

3 CR39 7.4 1166 ± 67

1 CH2 4.7 1105 ± 60

1 CR39 7.4 1113 ± 176

1 Al 27 1870 ± 131

0.41 CH2 4.7 948 ± 54

0.41 CR39 7.4 1285 ± 245

0.41 Al 27 1950±126

0.30 CH2 4.7 949 ± 61

0.30 CR39 7.4 1174 ± 192

0.30 Al 27 2008±144The quoted uncertainties are statistical standard deviations

Fe26+ on Al

Fe26+ on CH2

[ Phys. Rev. C 56 (1997) 388 ][ Phys. Rev. C 56 (1997) 388 ]

[ Phys. Rev. C 56 (1997) 388 ]

Tot

al c

ross

sec

tion

(m

b)

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FRAGMENTATION CROSS SECTIONS OF Si14+ ON CH2 , CR39 , Al , C e H

Energy (A GeV) Target tot (mb)

5 CH2 757 ± 168

3 Al 1533 ± 133

1 CR39 1113 ± 176

1 H 483 ± 76

1 CH2 694 ± 70

1 C 1117 ± 62

1 Al 1397 ± 138

The quoted uncertainties are statistical standard deviations

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 ]

[ Nucl. Phys. A 784 (2007) 341 ]

Tot

al c

ross

sec

tion

(m

b)

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DATA-PREDICTIONS COMPARISON

0.29 A GeV C Present work

Tot

al c

ross

sec

tion

(m

b) [ Phys. Rev. C 39 (1989) 2222 ]

[ Nucl. Phys. A 784 (2007) 341 ]

[ Phys. Rev. C 66 (2002) 014609 ]

Target mass AT

[ Phys. Rev. C 56 (1997) 388 ][ Phys. Rev. C 56 (1997) 388 ]

Tot

al c

ross

sec

tion

(m

b)

Target mass AT

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PARTIAL CHARGE CHANGING CROSS SECTIONS

Charge resolutionZ ~ 0.2e

Average base areas for tracks present in at least 2 out of 3 measured CR39

sheets located after the target

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Z Z (mb) Z (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 CHARGE CHANGING CROSS SECTIONS

Partial fragmentation chargechanging cross sections for 1 AGeV Si14+ and 1 AGeV Fe26+ ions on the CH2 target

The quoted uncertainties are statistical standard deviations

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CONCLUSIONSThe 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 dependenceThere 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 Z 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