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Exposure of an ECC to 400 Mevu Carbon ions

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Exposure of an ECC to 400 Mevu Carbon ions Powered By Docstoc
					Study of the fragmentation of Carbon ions for
             medical applications


             Giovanni De Lellis
             Napoli University


                            Protons (hadrons in general)
                          especially suitable for deep-sited
                         tumors (brain, neck base, prostate)
                                   and fat people
                     Dose modulation

 From the overlap of close peaks
(close energies), a conformational
        profile is obtained




The patient is rotated so to avoid
  a long exposure time of the
        healthy tissues


         Size of the sick part
Carbon beam

         Same energy deposit profile
          as protons but with larger
          energy loss per unit length




                one ionization
                every ~ 10nm
              (DNA helix ~ 2nm)
         Charge and mass measurement
 • Density of energy along the track path µ Z2
 • Multiple scattering or magnetic field provides
   either pb or p
 • From the combined measurement, we can get p
   and the mass à A,Z
                     Open issues
•Knowledge of the Carbon cross-section with human
tissues
•In particular the exclusive cross-section in the different
channels so to predict the detailed irradiation of the
neighboring tissues à optimization of the therapy with
higher effectiveness
              Facilities in Europe
• Typically joint beam (physicists) and therapeutic
  (biological, medical) facilities.
• In Europe, a high energy (few hundred MeV/nucleon)
  carbon beam is at GSI, Darmstadt, Germany
• In Italy (Pavia, close to Milan) the CNAO under
  construction, starting on 2009
• Proton centers more numerous
• In Italy (linked with INFN) one proton center
  operative in Catania, Sicily
Exposure of an ECC to 400 Mev/u Carbon ions
   ECC structure: 219 OPERA-like emulsions and 219 Lexan
          sheets 1 mm thick (73 consecutive “cells”)
              exposed to 400 Mev/u Carbon ions
 Lexan: r = 1.15 g/cm3 and electron density = 3.6 x 1023/cm3
                  e.g. Water 3.3 x 1023/cm3
     Cell structure
R0           R1           R2
                                       R0: sheet normally developed after
                                                  the exposure
     LEXAN




                  LEXAN




                               LEXAN




                                          R1: sheet refreshed after the
                                       exposure (3 days, 300C, 98% R.H.)


                                           R2: sheet refreshed after the
                                        exposure (3 days, 380C, 98% R.H.)
Carbon exposure at HIMAC (NIRS-Chiba)
            C ions angular spectrum
Slope Y




                                                       slope X   slope Y
                                                       (3 s)     (3 s)

                                                       -0.150    -0.003
                                                 P1
                                                       ±0.004    ±0.005

                                                       -0.017    -0.002
                                                 P2
                                                       ±0.004    ±0.005

                                                       0.134     -0.001
                                                 P3
                                                       ±0.004    ±0.005

                                      Slope X

          3.4 cm2 scanning in each sheet (all sheets scanned)
   Vertex reconstruction
About 2300 vertices analyzed




C




             3 cm
   Impact parameter distribution

Hydrogen tracks     Helium tracks




           µm                       µm
Track volume: sum of the areas of the
   clusters belonging to the track
one sheet – R0 type         one sheet – R1 type

   BG, mip              p       a   Z>2
             Z>1




       Upstream sheet         Upstream sheet




      p




 Downstream sheet           Downstream sheet
   (about 5 cm)               (about 5 cm)
R0 vs R1 and R1 vs R2 scatter plot

   He




                           He
   H
                      Charge identification
5 R1 VS 5 R2 (2 cm)                   10 R1 VS 10 R2
                                      (4 cm)




                       Z=4
                 Z=3


 Z=2




15 R1 VS 15 R2                        20 R1 VS 20 R2
(6 cm)                                (8 cm)
                                                        Z=5
                                                Z=3
                                                              Z=6
                                                       Z=4



                                        Z=2
         Charge separation




Journal of Instrumentation 2 (2007) P06004
Charge distribution of secondary particles
        charge reconstruction efficiency



                              Inefficiency àCharge = 0
                                 Charge efficiency =
                                  (2848-27)/2848 =
                                      99.1±0.2%
             Carbon interaction

Track multiplicity




                                             Bragg peak




              Contamination at the % level
 Angular distribution of secondary particles
Elastic scattering                    Hydrogen


        large angle (a few percent)




              Helium                    Lithium
           Cross-section measurement
• A volume of about 24cm3 was analyzed
• 2306 interaction vertices found (475 elastic)
• The number of events with maximal charge as Lithium (Dz = 3) is
  183, as beryllium (Dz = 2) is 118, as Boron (Dz = 1) is 258




                                                    Toshito et al.




                 Toshito et al.                  Toshito et al.
Interaction length for different secondary ions
                  Very preliminary    He-proton
• 8Be à He + He (10-16 s)            opening angle
• Q value 90 keV
           He
      q
           He

                                      Real event




                q (rad)
                     Conclusions
• The charge separation capability is about 5 sigma
  for protons and helium already with less than 10
  plates where other detectors fail
• The separation between boron and carbon requires
  30 plates to reach 2.5 sigma
• Emulsions provide unprecedented results in the light
  ion identification
• Preliminary results cross-section measurement
              Possible improvements
    •Improve the identification capability for short tracks
 •Measure the momentum for isotope discrimination
 •Extend the energy range for cross-section measurements

				
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posted:7/24/2013
language:English
pages:21