E528SNeutron correlation in 6He studied

through its nuclear break-up.

Reaction : 6He + Pb @ 20 MeV/A 4He + n + n + Pb

M.AssieM.Assie, J.A.Scarpaci, D.Lacroix, M.Alahari, J.C.Angelique, T.Aumann, D.Bazin, Y.Blumenfeld, D.Beaumel, W.Catford, M.Chabot, A.Chatterjee, M.Fallot,

D.Mengoni, J.Nyberg, C.Petrache, F.Skaza, H.Iwasaki, T.Tuna

SPIRAL beam6He is an archetype of a Borromean nucleus ; high intensities

most suitable nucleus to investigate new experimental approach and develop new theoretical tools

Cigar configuration

Zhukov et al., Phys. Rep. 231 (1993) 151

Di-neutron configuration

Neutron angular emission

Large impact parametersCoulomb break-up

cigar di-neutron

n

d/dd

60°0°

Small differencesin relative angles

G.Normand, PhD thesis 2004F.M.Marques, PR C64, 2001

Measure neutrons at large anglesNeeds a theoretical development

Small impact parametersNuclear break-upcigar di-neutron

extension of TDHF (TDDM)(M.Assie-D.Lacroix)

n

d/dd

60°0°

di-neutron

cigar

6He20 MeV/u

EDEN

EDEN

I = 106~107 pps

Set-up for E528S

Gazeous profiler

neutrons

Measurement

6He

4He

SiLi

Strips

NWall

Experimental relative angular distribution

cigar

di-neutron

Uncorrelated (mixed events)

10 < En < 30 MeV

All Nwall and EDEN

For En > 10MeV 20% of the events are cross-talk events

12C11C11B

10B

8% remains

Measurement of crosstalk with 12C + 208Pb 10B

1n+1p

Rejection criterea : •Ecalc<Eloss ==> cross talk

•Eout(i)>Eloss(j) & Eout(i)> Eij

min ==>might be crosstalk

Ecalc=time of flightEout=Ecalc-Eloss

Eijmin=minimum E to go from i to j

Eloss(j)

Ecalc(i)

Eout(i)

Detector Number

Dete

ctor

Num

ber

Close detectors

Test of the rejection algorithm with GEANT4

One emitted neutron - 2 detectors hit Only 15% of the crosstalk events remain

With and without crosstalk for >40° (nuclear break-up)

Counts for rel <20° : 1 492 860 (with crosstalk) 953 203 (without crosstalk)63% remains

10 < En < 30 MeV

PRELIMINARY

without crosstalk

with crosstalk

35% of the events remains in the Neutron Wall after subtraction of the crosstalk pour rel<20°

10 < En < 30 MeV

PRELIMINARY

degrees in the NWall

Without crosstalk correction

With crosstalk correction

10 < En < 30 MeV

Correlations subtracted from the cross-talk

PRELIMINARY

New neutron detector characteristics

• No cross-talk! (think of the best protocol to remove it)

• Variable thickness (two sets of detectors)

• Large angular coverage (nuclear break-up, SPIRAL2)

• Compact electronics• New materials!

Efficiencies measured with Californium and calculated ?

Seuil =100 keVee

Exp E337 S2s = 0,47± 0,04

S1d= 0,50 ± 0,20 S1p= 3.9

4*1p

0.5*1d

no-

incoincidence

Neutron energy spectra

TDSE calc.2s

11Be 10Be + n + @ 41 MeV/A

10Be

48Ti

48Ti11Be

3 m

n-detectors

10Be

SPEG

Château de cristal

TDSE Calculationnon-perturbative

V.Lima et al., Bormio 2004V.Lima, Ph.D. Paris XI, oct 2004V.Lima et al., in preparation