Carbon ion fragmentation study for medical applications

Protons (hadrons in general)especially suitable for deep-sited

tumors (brain, neck base, prostate)and fat people

G. De LellisNapoli University

Dose modulation

From the overlap of close peaks (close energies) , 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 Z2

• Multiple scattering or magnetic field provides either p or p

• From the combined measurement, we can get p and the mass A,Z

Exposure of an ECC to 400 Mev/u Carbon ions

ECC structure: 219 OPERA-like emulsions and 219 Lexan sheets ( = 1.15 g/cm3) 1 mm thick (73 consecutive “cells”)

exposed to 400 Mev/u Carbon ions

Cell structure

LE

XA

N

LE

XA

N

LE

XA

N

R0 R1 R2

R0: sheet normally developed after the exposure

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 X

Slo

pe

Y

slope X

(3 )

slope Y

(3 )

P1-0.150 ±0.004

-0.003 ±0.005

P2-0.017 ±0.004

-0.002 ±0.005

P3 0.134 ±0.004

-0.001 ±0.005

3.4 cm2 scanning in each sheet (all sheets scanned)

Track volume: sum of the areas of the clusters belonging to the track

BG, mip

Z > 1

p

Upstream sheet

Downstream sheet(about 5 cm)

p Z > 2

one sheet – R0 type one sheet – R1 type

Downstream sheet(about 5 cm)

Upstream sheet

R0 vs R1 and R1 vs R2 scatter plot

H

He

He

R1 versus R2

HeLi

Be

B

C

20 to 30 sheets5 to 10 sheets

Charge identification

Z = 2

Z = 3

Z = 4

5 R1 VS 5 R2 (2 cm) 10 R1 VS 10 R2 (4 cm)

15 R1 VS 15 R2 (6 cm)

20 R1 VS 20 R2 (8 cm)

Z = 4

Z = 3

Z = 2

Z = 5

Z = 6

Charge separation

Charge separation versus the number of segments

Helium-Lithium Lithium-Beryllium

Charge separation versus the number of segments

Boron-CarbonBeryllium-Boron

Charge identification efficiency

One vertex

C

3 cm

Vertex analysis

Impact parameter distribution

Track multiplicity at interaction vertex

Charge distribution of secondary particlescharge reconstruction efficiency

Inefficiency Charge = 0Charge efficiency = (2848-27)/2848 =

99.1±0.2%

Sum of the charge at the interaction vertex

Carbon interactions

Bragg peak

Contamination at the percent level

Angular distribution of secondary particles

Particle ranges for different charges

Ranges and interaction lengths for stopping and interacting particles

Elastic scattering angle

~ 6% Contamination

Conclusions• The charge identification works well up to the Carbon• 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

• The vertex reconstruction works with impact parameters of 10 µm or less

• Elastic and anelastic scattering are well separated

Outlooks•Improve the identification capability for short tracks

•Measure the momentum for isotope discrimination