Multiplicity and Energy of Neutrons from 233U(nth,f) Fission Fragments Katsuhisa NISHIO Japan Atomic Energy Agency (JAEA)

Japan Atomic Energy Agency (JAEA), Tokai Campus Japan Atomic Energy Research Institute Japan Atomic Energy Agency (JAEA), Tokai Campus Tokai Institute Tandem J-PARC Tokyo Tokai

Contents Neutron multiplicity and energy spectrum measurement ➢ 235U(nth,f), 233U(nth,f), 239Pu(nth,f) (2) Experiment at J-PARC ➢ n + actinide ➢ μー + actinide Research Reactor, Kyoto University

Contents Neutron multiplicity and energy spectrum measurement ➢ 235U(nth,f), 233U(nth,f), 239Pu(nth,f) (2) Experiment at J-PARC ➢ n + actinide ➢ μー + actinide

Research Reactor Institute, Kyoto University Tokyo Kyoto Tokai Osaka Supermirror Neutron Guide Tube 5×107 neutrons/cm2/s Kyoto University Reactor 1964 First Criticality 5 MW Operation

Fission Neutron Measurement at KURRI Fission Fragment ( mass and kinetic energy ) 　　➢　Si-detector : Pulse height Analysis ➢ Parallel Plate Avalanche Counter : Time-of-Flight analysis Prompt Fission Neutron (neutron energy) 　　➢　Flight path = 76.5 cm 　　➢　Liquid Scintillator NE213 ( Φ 5 ” × 2 ”) K. Nishio et al., J. Nucl.Sci.Technol., 35, 631 (1998).

Neutron Spectra For neutrons energy Spectra in the c.m. Frame FWHM = 1.5 ns For neutrons energy Spectra in the c.m. Frame ➢ Vn >= Vf1 / cos θ Assumption : All the neutrons are emitted from the fully accelerated fragments

Calculated Neutron yields Light Fragment Heavy Fragment Fragment 1 Fragment 2 Neutron detector θ < 18o

Fission Fragment Yield

Neutron energy spectra from fragments in c.m. frame for 233U(nth,f)

Average neutron energy from FFs for 233U(nth,f)

Neutron multiplicities for 233U(nth,f) νＬ ＝1.49 νH = 1.01

Total Neutron multiplicity as function of TKE for 233U(nth,f)

Neutron multiplicity from fragment as function of TKE for 233U(nth,f)

Scission configuration

Level density parameters of fission fragments

Total excitation energy of the fragments

Total neutron multiplicity for each TKE TKE (MeV)

Contents Neutron multiplicity and energy spectrum measurement ➢ 235U(nth,f), 233U(nth,f), 239Pu(nth,f) (2) Experiment at J-PARC ➢ n + actinide ➢ μー + actinide

J – PARC ( Japan Proton Accelerator Research Complex )

Neutrino Target Area Materials & Life Experimental Hall 3 GeV Linac Hadron Experimental Hall Linac ニュートリノと変更した。 施設建設における苦労話（地下水対策、塩田発掘調査、オオタカ保護など）について触れた方がよい。

J－PARC Now 100 kW (300 kW) Current (μA) Energy (GeV)

MLF Materials and Life Science Facility MLF Building Mercury Target and Its Container Shutter on the Top of the Source Proton Beam

MLF Materials and Life Science Facility Neutron Beam Lines Summer of 2007

MLF Materials and Life Science Facility Neutron Time-of-flight cource Proton

Neutron TOF course Flight path = 22 - 29 m Neutron energy = 0.01 eV – 100 keV Undergoing measurement ➜ Neutron capture cross-sections for 244,245Cm, 129I, 99Tc, 93Zr ➜ Fission experiments can be proposed !

Neutron induced Fission ➢　Prompt neutron multiplicity and energy spectra Mass – TKE correlations (Cm244,Cm245, …) Pre-scission neutron ? I. Tsekhanovich et al., Phys.Rev.C 70 , 044610 (2004)

Investigation for the Fission Neutrons Target Prompt Fisssion Neutron Neutron form J-PARC Fragment Neutron Detectors Fission Fragment Detectors Energy of prescission neutron ?

Neutron induced Fission ➢　Fragment mass distribution and angular distributions from each resonances. ➢ Resonance tunneling through the collective states in the 2nd minimum ( mass distributions )

Contents Neutron multiplicity and energy spectrum measurement ➢ 235U(nth,f), 233U(nth,f), 239Pu(nth,f) (2) Experiment at J-PARC ➢ n + actinide ➢ μー + actinide

muon course 3 GeV proton Positive or negative muons slower than 120 MeV/c are available. Beam intensity（＠100kW proton beam): 1.0×106/s

μ－ induced Fission E1(2p->1s) 238U = 6.6 MeV V.E. Oberacker et al., Phys.Rev.C 48, 1297 (1993). E1(2p->1s) 238U = 6.6 MeV E2(3d ->1s) 238U = 9.6 MeV 1s 2p 3d ? Delayed Fission (78 ns in 238U) Prompt Fission : muon stays at the fissioning nucleus H L