1. Nuclear emulsions
One of the eldest particle detectors, still used in particle physics experiment (CHORUS, DONUT, OPERA) for its unique peculiarities:
Space resolution (< 1 mm)
3 D Reconstruction
Continuous recording
Nuclear fragment
Muon track
300 mm
nm CC interaction (OPERA experiment

2. The OPERA nuclear emulsion
Two emulsion layers coated on a plastic support.
Dimensions: 12.5 x 10.0 cm2
The emulsions were produced by Fuji Film in Japan after a long R&D program held jointly with Nagoya university.
Enhanced AgBr/gel WRT standard photographic films
12.5 cm
200 m
BASE
EMULSION
42 m
10.0 cm

3. Tracking efficiency (mip)
Main features
Intrinsic resolution: 0.06 m
Sensibility: 33 grains / 100 m (m.i.p.)
Accidental grains: 5-10 grains / 1000 m3
Angular resolution
(X,Y) = 1.4 (1 + 4X,Y) mrad
100 m
Tracking efficiency (mip)

4. Emulsion Cloud Chamber
8.3 Kg
The ECC is a sandwich of nuclear emulsion films interleaved by absorbers (1 mm thick Lead in OPERA)
10 X0’s Pb
Emulsion layers n t
1 mm
The ECC is a self consistent detector:
Vertex reconstruction, decays, momentum measurements (multiple scattering), shower reconstruction
neCC candidate
E.shower = 4.71.3 GeV
nmCC interaction with charmed particle produced
8 mm
24 mm

5. Automatic scanning Bern emulsion scanning lab.
An R&D has been conducted among several european labs to design an automatic scanning system able to scan up to 20 cm2/h of emulsion surface
Bern peculiarities: automatic emulsion plate changer, dry scanning

6. Working cycle
Tomographic scan: 16 images (360 x 280 m2) grabbed in 44 m
CMOS Camera working at ~400 fps
Vertical movement at constant speed: 987 m/s
Full cycle lasting ~ 150 ms
Vertical Axes
Orizontal Axes
150 ms

7. 3rd International Workshop on Nuclear Emulsion Techniques
An application to medical physics: Study of the fragmentation of Carbon ions
Presented at the
3rd International Workshop on Nuclear Emulsion Techniques
Nagoya, Japan, Jan 24, 2008
Published in: JINST 2:P06004,2007

8. 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:  = 1.15 g/cm3 and electron density = 3.6 x 1023/cm3
e.g. Water 3.3 x 1023/cm3
Cell structure
LEXAN 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.)

9. Carbon exposure at HIMAC (NIRS-Chiba)

10. C ions angular spectrum
slope X
(3 )
slope Y P1
±0.004
±0.005 P2
±0.004
±0.005 P3
±0.004
±0.005
Slope Y
Slope X
3.4 cm2 area full analyzed in each emulsion sheet

11. Vertex reconstruction About 2300 vertices analyzed
3 cm

12. Impact parameter distribution
Hydrogen tracks
Helium tracks µm µm

13. Charge identification through ionization
We define the track volume as the sum of the areas of the clusters belonging to the track. It is directly related to the energy loss by ionization. The average track volume, calculated for the different emulsion types (R0, R1, R2) is the key variable for particle ID.
one sheet – R0 type
BG, mip
Z > 1 H
Downstream sheet
(about 5 cm)
Mip are visible only on R0, H on R0 and slightly on R1, Z > 1 on R0,R1,R2.

14. R0 vs R1 and R1 vs R2 scatter plotHe He H

15. 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 (6 cm)
20 R1 VS 20 R2 (8 cm)
Z = 5
Z = 3
Z = 6
Z = 4
Z = 2

16. Charge separation
VR01 defined in the VR0 VR1 plane and VR12 in the VR1 VR2 plane

17. Inefficiency Charge = 0
Charge distribution of secondary particles charge reconstruction efficiency
Inefficiency Charge = 0
Charge efficiency =
( )/2848 =
99.1±0.2%

18. Carbon interaction Track multiplicity Bragg peak
Contamination at the % level

19. Angular distribution of secondary particles
Hydrogen
Elastic scattering
large angle (a few percent)
Lithium
Helium

20. 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 (z = 3) is 183, as beryllium (z = 2) is 118, as Boron (z = 1) is 258
Toshito et al.
Toshito et al.
Toshito et al.

21. Interaction length for different secondary ions

22. 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