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Geant4 Validation of
12C Bragg Peaks in Water
Miguel A. Cortés-Giraldo Universidad de Sevilla (Seville, Spain)
In collaboration with:
V. Ivanchenko (CERN), J. M. Quesada (Univ. Sevilla), M. I. Gallardo (Univ. Sevilla)
and D. Schardt (GSI)
19th Geant4 Collaboration Meeting
Okinawa Convention Center, Okinawa (Japan)
September 30th, 2014
2 Experimental Setup
Relative ionization
measurements (IC2/IC1)
courtesy of D. Schardt (GSI).
Precise measurement of
absolute depth in water.
For carbon ions, reported
uncertainty of the Bragg peak
absolute depth is 0.2 mm.
D. Schardt et al., GSI Scientific Report 2007
3 Simulated Setup
Just a water tank (G4_WATER).
Water density corrected
according to report (24ºC, 0.997
g/cm3).
Energy deposition scored in
cylindrical voxels along beam
axis, with same radius as IC2
(28 mm). Thickness of 50
microns, similar to water
equivalent thickness of ICs.
First-order approximation beam
parameters (pencil beam, 0.10%
energy spread).
D. Schardt et al., GSI Scientific Report 2007
4
QGSP_BIC_HP_EMY
physics list
5 Results with Geant4-10.0.2
QGSP_BIC_HP_EMY – 100 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
-0.15 mm.
6 Results with Geant4-10.0.2
QGSP_BIC_HP_EMY – 200 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.2mm
• Deviation from experiment:
BP(G4)-BP(exp) =
-0.1 mm.
7 Results with Geant4-10.0.2
QGSP_BIC_HP_EMY – 400 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
+0.30 mm.
• The calculation seems to
agree well with
measurements …
8 Results with Geant4-10.0.2
QGSP_BIC_HP_EMY – 400 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
+0.30 mm.
• … although the BP position
shift is slightly larger than
experimental uncertainty.
9
QGSP_BIC_HP
physics list
10 Results with Geant4-10.0.2
QGSP_BIC_HP – 100 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
-0.4 mm.
(I = 78 eV)
11 Results with Geant4-10.0.2
QGSP_BIC_HP – 200 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
-0.9 mm.
(I = 78 eV)
12 Results with Geant4-10.0.2
QGSP_BIC_HP – 400 MeV/u
Bragg peak position:
• Sensitivity to production cut
value < 0.1mm
• Deviation from experiment:
BP(G4)-BP(exp) =
-2.0 mm.
• The deviation found is larger
than that reported for with
version 9.3, G4EmStandard :
[Lechner et al. NIMB 268 (2010)]
(I = 78 eV)
13 Results with Geant4-10.0.2
QGSP_BIC_HP – Water I-value estimation
(I > 90 eV) (I ~ 88 eV)
(I = 86 eV) • The I-value needed to fit the experimental
data shifts systematically to higher values as
the 12C beam range becomes larger.
• A water I-value of 86-90 eV is far than the
latest values accepted for water.
To verify this with other ion beams.
14
CSDA Range Computation
15
CSDA range comparisons with values at ICRU73 report
and other codes
Geant4 values obtained either through direct computation and via
GetCSDARange() at stepping level. Calculated with EmStandard_option3 (EMY)
and EmStandard_option0 (Opt0).
Data from MSTAR (H. Paul) and SHIELD-HIT (labeled as BETHE_EXT00)
calculated using libdEdx (see at http://dedx.au.dk/).
16 Results with Geant4-10.0.2
Computed CSDA range with TestEm7
(No secondaries, msc nor eLoss fluctuations)
The agreement of EmStandard eLoss
is within +-1 mm w.r.t. ICRU73 !!
17
The finite angular acceptance of
the experimental setup
may also help to verify hadronic
fragmentation models
18 Results with Geant4-10.0.2
Experimental vs Full Lateral Acceptance
19 Results with Geant4-10.0.2
BIC-ion vs. QMD Ion Model
20
Conclusions & Final Remarks
New precise Bragg peak data, courtesy of Dieter Schardt (GSI) – Good opportunity
to fine tune ion electronic stopping power data in water.
Experimental angular acceptance is not full. Thus, they can also be used to check
nuclear fragmentation models.
Reference QGSP_BIC_HP_EMY physics list performs remarkably well for carbon
ions.
EmStandard (opt0) ion processes revision needed according to the water I-values
obtained and CSDA ranges computed through TestEm7. Calculations with ‘eLoss’
model gives results within acceptable accuracy, but Bragg peaks are systematically
displaced with respect to data and opt3.
Further work with other energy values and ion types is expected.
21
Thanks for your attention
