1 Nuclear Activation Techniques to measure the energy distribution of laser-accelerated protons bunches T.Bonnet, M.Comet, D.Denis-petit, F. Gobet, F. Hannachi, M. Tarisien and M. Versteegen Centre d’Etudes Nucléaires de Bordeaux Gradignan (CENBG/ Université de Bordeaux/CNRS-IN2P3) Palaiseau, June 7 th 2012

2 Nuclear Activation x +T  R+ y T (x, y) R A(t) = n x σ TR N T  z λe -λt T 1/2 = ln(2) / λ A : activity (Bq) N T : nuclei density of the target (cm -3 ) n x  number of incident particles  z : target thickness (cm)  TR : reaction cross section (cm²) A(t) = N R (t) λ x T y R R Radioactive constante Half life period

3 High flux of energy Optik & Photonik June 2010 No. 2 Electron energy (MeV) Electron yield (MeV -1 sr -1 ) Physical signal in a detector E ~ 0.1 J (~10 12 MeV) in few ns P ~ 100 MW  ~ 10 8 W/cm² Target Al 10µm TW LULI

4 Nuclear Time Multiplexer target Laser x Particles Radioactive period is a time multiplexer Each nucleus is a detector : no saturation Activity measurement give information on  number or radioactive nuclei  number of particles passing through the target zz Standard nuclear physic detector

5 target Laser zz Projectile Type Discrimination x Particles x’ Particles Standard nuclear physic detector T (x, y) R T (x’, y’) R’ Time (min -1 )

6 How to deduce energy distribution? *Knowing the stopping power of x particles in the matter *even Better : Simulating particles interactions with matter : GEANT4 simulations

7 How to deduce energy distribution? Response function of the stack : GEANT4 simulations 1 incident particle E 1  N R11 ; N R12 ; … ; N R1j ; …... N R1k radioisotopes in each k foils 1 incident particle E 2  N R21 ; N R22 ; … ; N R2j ; …... N R2k radioisotopes in each k foils  = 1 incident particle E n  N Rn1 ; N Rn2 ; … ; N Rnj ; …... N Rnk radioisotopes in each k foils ……………………………….. Response function matrix =

8 How to deduce energy distribution? Response function of the stack Least Squares Minimization varying on k foils Measured radioisotope in each foil Energy distribution of incident particles

9 Beta+ radioactivity Scintillators Two 511 keV photons detected in coïncidence  low noise : 20 counts / hour T 1/2 = several minutes

10 NATALIE* detection system NATALIE detection system : 16 pairs of NaI(Tl)  16 foils measured together. Nuclear Activation Techniques for Analysis of Laser Induced Energetic particles - compact electronic system - energy, time, dead time measured GEANT4 efficiency calculations for *different energy release by beta+ decays *extended sources

11 Copper field of applications Natural copper : 2 stable isotopes 63 69,17 % 65 30,83 % 65 Cu ( n,2n) 64 Cu 64 Cu → 64 Ni + e + + ν e T 1/2 ( 64 Cu) = h and E thr = 10.1 MeV Nuclear reactions with neutrons Nuclear reactions with electrons : no nuclear reactions Nuclear reactions with protons 63 Cu ( p,n) 63 Zn 63 Zn → 63 Cu + e + + ν e T 1/2 ( 64 Cu) = 38.5 min and E thr = 4 MeV Nuclear reactions with gamma rays 63 Cu ( ,n) 62 Cu 62 Cu → 62 Ni + e + + ν e T 1/2 ( 62 Cu) = 9.73 min and E thres = 10.8 MeV 63 Cu ( ,2n) 61 Cu 61 Cu → 61 Ni + e + + ν e T 1/2 ( 61 Cu) = 3.33 h and E thres = MeV

12 Nuclear Activation is everywhere Not only copper ; Carbon also… Together energy and space distributions Least Squares Minimization ParameterOptical Densitometry Nuclear activation E 0 (MeV)0.86 ± ± 0.1 E cut (MeV)17.1 ± ± 0.1 n 0 protons(1.65 ± 0.14) (3.0 ± 0.3) C (p,  ) 13 N 13 N → 13 C + e + + ν e T 1/2 ( 13 N) = 9.96 min and E thr = 0 MeV

13 Nuclear Activation is everywhere Even IP… 3.1 MeV on TR image plate Spectrum obtained with a Germanium detector

14 In the Future Autoradiography on counting activation station *Imaging Plate : - Spatial distribution of the particle bunch *Activation : - Absolute numbers because of response stability of activation - any β+ radioisotopes ; large choice of activation sample matter

15 In the Future Matrix modelisation of the stack Response function of the whole stack  long GEANT4 calculation k foils stack Stopping power of a foil type j Energy distribution at the entrance of each foil j : Response function of each foil type  number of radioisotopes on each foil : (N R1j … N R2j … N Rnj ) 

16 In the Future User friendly modular counting station Collaboration with a company to develop compact and modular electronics Depends on community demand

17 Conclusion Possible spatial distribution measurement with autoradiography technique Possible simplifications of the method  User friendly tools With activation techniques : - No flux saturation - Stable response function, no surrounding conditions dependence - Particle responses discrimination Different materials can be activated : - Pure material (copper ; carbon ; …) - Mixed material (alloy, powders, etc…) - Detectors (RCF, IP, …)

18 Conclusion Thank you for your attention

19 Conclusion