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

2. 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

3. 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

4. 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

5. 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

6. 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).

7. 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

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

9. Fission Fragment Yield

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

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

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

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

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

15. Scission configuration

16. Level density parameters of fission fragments

17. Total excitation energy of the fragments

18. Total neutron multiplicity for each TKE
TKE (MeV)

19. 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

20. J – PARC ( Japan Proton Accelerator Research Complex )

21. 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。

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

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

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

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

26. 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 !

27. 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 , (2004)

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

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

30. 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

31. 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

32. 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