Measurement of n xn reactions on actinides GANILNFS

Measurement of (n, xn) reactions on actinides @GANIL/NFS G. Bélier, A. Chatillon, B. Laurent, P. Marini, V. Méot, O. Roig and J. Taieb – CEA/DIF X. Ledoux - GANIL, Caen JOINT JEFF-CHANDA MEETING, NOV 20 -21, 2017

Introduction Three methods ü Activation: can be very precise but requires very pure targets, short half-life activation product and monoenergetic neutron beams. ü Neutron counting experiment: need efficient fission veto, high and well defined efficiency counter. ü Partial (n, xn ) measurements: requires excited level feeding modeling. Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Introduction Three methods ü Activation: can be very precise but requires very pure targets, short half-life activation product and monoenergetic neutron beams. ü Neutron counting experiment: need efficient fission veto, high and well defined efficiency counter. ü Partial XS measurements: requires excited level feeding modeling. → Long term experimental plan at GANIL/NFS facility Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Accepted experiment @NFS on 238 U (n, 2 n) and (n, 3 n) reaction cross sections Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

(n, 2 n) reaction experiment commissioning Activation measurement Neutron counting experiment Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

(n, 3 n) reaction Only 2 measurements on exfor + almost no overlap Systematic uncertainties ? Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Accepted exp@NFS: neutron counter + fission veto Multiplate fission chamber: 360 mg of 238 U 72 deposits, CF 4 gas, homemade dedicated preamps Fission veto SCONE (Solid COunter for NEutron) Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Experimental setup: neutron counter + fission veto Multiplate fission chamber: 360 mg of 238 U 72 deposits, CF 4 gas, homemade dedicated preamps Fission veto SCONE (Solid COunter for NEutron) Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Neutron counting experiment: what is new? • Fission chamber fission veto NIMA 833(2016)1 ü Fast: time resolution < 1 ns ü High efficiency ü Very good α-fission separation ü Very high count rates capability • Neutron counter: solid version of usual long counters Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Neutron counter principle: Gd loaded scintillator High Hydrogen content neutron thermalisation High probability of capture on Gd stochastic delayed captures individual neutron counting in a 50 µs time - window Neutrons from the same event are time correlated Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Solid equivalent: SCONE scintillator structure • 896 plastic bars (EJ 200) total Ring 2 ü Inner ring: 320 bars 1 m long ü Outer ring: 576 bars 50 cm long Ring 1 MCNP simulations capturetime distribution similar to usual neutron ball tanks for scintillator bars 25 x 25 mm² large Ti. O 2 loaded paint Gd 2 O 3 loaded paint 25 x 25 mm² Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Advantages of a solid neutron ball • No aging associated to Gd dissolution into an organic solvant • No metallic tank higher efficiencies at low energy • Higher optical segmentation -rays multiplicity ? • Long first ring small solid angle for beam openings • No hazardous material (organic solvant have low temperatures flash-point + are highly toxic) Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Simulated detection efficiency Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Measurement method Triggerless data acquisition Store every event • Background estimated to 100 neutron/s : time-uncorrelated • Fission events 8. 3 neutrons/s : time-correlated and vetoed @ 8 Me. V • n, 2 n reactions 4. 6 neutrons/s : time-correlated Correlated neutrons detected in a time window less than 50 µs Typical signal/background is higher than 100 Measurement strategy: • (p, Li) quasi monoenergetic beams for reaction opening measurement: no way to measure the incoming neutron energy at reaction openings. • (d, Be) white neutron surce at higher energy incoming energy measured by TOF technique. Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

Outlooks • (n, xn) reactions ü 2020– measurement on uranium 238 (33 UT allocated) ü Mid-term plan (2022): 239 Pu (EUFRAT proposal for targets production), 235 U • Fission studies ü Neutron multiplicities full distributions ((n, xn) experiment) ü Fission -rays (total energy, multiplicities ) simulations needed (dedicated experiment) ü Cross sections ((n, xn) experiment) Joint JEFF-CHANDA meeting, Nov 20 -21, 2017

En vrac • Spectres et nubar ü mesure U 238 en 2020 ü suite ? ? ? • Captures radiatives, inélastique (très prospectif ) Joint JEFF-CHANDA meeting, Nov 20 -21, 2017