Multiplicity and Energy of Neutrons from 233U(nth,f) Fission Fragments

Katsuhisa NISHIO

Japan Atomic Energy Agency (JAEA)

Japan Atomic Energy Research Institute

Tokai InstituteJapan Atomic Energy Agency (JAEA),

Tokai Campus

Tokyo

Tokai

J-PARC

Tandem

Contents

(1) 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

(1) 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

TokyoKyoto

Tokai

Supermirror Neutron Guide Tube

1964 First Criticality 5 MW Operation

Kyoto University Reactor

Research Reactor Institute, Kyoto University

5×107 neutrons/cm2/s

Osaka

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

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

Fragment 1 Fragment 2 Neutron detector

θ < 18o

Light Fragment Heavy Fragment

Fission Fragment Yield

233U(nth,f)

Tota

l Kin

etic

Ene

rgy

[MeV

]

Fragment Mass [u]

Q-value

80 90 100 110 120 130 140 150

140

160

180

200

220

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)

ν Ｌ ＝ 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)

-d

/ dT

KE

(M

eV-1

)

Fragment Mass [u]

Yie

ld

(%)

132102

80 100 120 140 1600.00

0.02

0.04

0.06

0.08

0.10

0.12

0

1

2

3

4

5

6

7

8

Scission configuration

233U(nth,f)132 u102 u

Tot

al K

inet

ic E

nerg

y [M

eV]

Fragment Mass [u]

Q-value

80 90 100 110 120 130 140 150

140

160

180

200

220

Neutron multiplicity ;

132 u

102 u

0 1 2 3 4 5

- d

/ dT

KE

[1/

MeV

] 132102

TKEFragment Mass [u]

Yie

ld [

%]

80 100 120 1400.00

0.02

0.04

0.06

0.08

0.10

0

1

2

3

4

5

6

7

Level density parameters of fission fragments

Neu

tron

M

ulti

plic

ity

Mas

s Y

ield

(%

)

0

1

2

3

4

0

2

4

6

T (

MeV

)a

(M

eV -

1)

1.0

1.5

2.0

2.5

Fission FragmentStable Nuclei

E*=aT2

0

10

20

Fission Fragment

Stable Nuclei

132Sn78Ni

She

ll C

orre

ctio

n E

nerg

y

(MeV

)

Fragment Mass [u]80 100 120 140 160

-10

-5

0

5

Total excitation energy of the fragments

Total neutron multiplicity for each TKE

TKE (MeV)

233U(nth,f)

Tota

l Kin

etic

Ene

rgy

[MeV

] Fragment Mass [u]

Q-value

80 90 100 110 120 130 140 150

140

160

180

200

220

Contents

(1) 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 )

3 GeV

Linac

Materials & LifeExperimental Hall

Hadron Experimental Hall

Materials & LifeExperimental Hall

NeutrinoTargetArea

J － PARC

Energy (GeV)

Cur

rent

(μ

A)

Now 100 kW (300 kW)

MLF Building MLF Materials and Life Science Facility

Mercury Target and Its Container

Shutter on the Top of the Source

ProtonBeam

Neutron Beam Lines

Summer of 2007

MLF Materials and Life Science Facility

MLF Materials and Life Science Facility

Proton

Neutron Time-of-flight cource

Neutron TOF course

Undergoing measurement ➜ Neutron capture cross-sections for 244,245Cm, 129I, 99Tc, 93Zr ➜ Fission experiments can be proposed !

Flight path = 22 - 29 mNeutron energy = 0.01 eV – 100 keV

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

Neutron Detectors

Fission Fragment Detectors

Prompt Fisssion Neutron

Target

FragmentNeutron form J-PARC

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

(1) 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

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

3 GeV proton

μ － induced Fission

V.E. Oberacker et al., Phys.Rev.C 48, 1297 (1993).

Delayed Fission (78 ns in 238U)

Prompt Fission : muon stays at the fissioning nucleus

1s

2p

3d

?

E1(2p->1s) 238U = 6.6 MeVE2(3d ->1s) 238U = 9.6 MeV

H L