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

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

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)

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

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

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

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

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.)

Carbon exposure at HIMAC (NIRS-Chiba)

C ions angular spectrum slope X (3 ) slope Y 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 Slope Y Slope X 3.4 cm2 area full analyzed in each emulsion sheet

Vertex reconstruction About 2300 vertices analyzed 3 cm

Impact parameter distribution Hydrogen tracks Helium tracks µm µm

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.

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

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

Inefficiency Charge = 0 Charge distribution of secondary particles charge reconstruction efficiency Inefficiency Charge = 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 Hydrogen Elastic scattering large angle (a few percent) Lithium Helium

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.

Interaction length for different secondary ions

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