large -delayed neutron emission probabilities in the 78ni ... · j. a. winger et al., phys. rev....

Large -Delayed Neutron EmissionProbabilities in the 78Ni Region

Prof. Jeff Allen WingerMississippi State University

Background

Recent Experiments

The Future

Dr. Jeff Winger North American Workshop on Beta-Delayed Neutron Emission 5/3/2013

Why is -delayed neutron emission important?


r-process nucleosyntheis

Old t1/2 and Pn valuesNew t1/2 and Pn values

Decay properties are among important input data for the analysis of processes

occurring in nuclear fuels : half-lives, -delayed neutron branching

ratios, and total decay energy release (total decay heat)

Understanding of the fission yields and the properties of neutron-rich fission products

is important for the safe and efficient operation of current and future power

reactors as well as for nuclear fuel/waste (re)processing

*

0.1 1 10 10010-6

10-5

10-4

10-3

10-2

Del

ayed

neu

tron

yiel

d (n

/s/fi

ssio

n)

Time after fission (s)

ORIGEN Keepin (IAEA 6 group)

Application of -delayed neutron emissionin nuclear power simulations

Ian C. Gauld (2010)ORNL, Reactor and Nuclear Safety Division, Reactor Physics Group

Integral βn measurementsused for reactor analysis

-n isotopic decay data

ORIGEN is missing data for very short-lived

fission products

*Oak Ridge Isotope Generation and Decay Code

*


(N-1,Z+1)0

Energy

(N,Z)

Sn

S2n

Qβ

What factors into determining the Pn value?

Pygmy GTR

GTR

Sβ

Strength Function

f(Z+1,E*)

Fermi Integral

Iβ

Feeding Intensity

decay

2n decay

n decay


The devil is in the details!77 77 * 76Cu Zn Zn

n

77 1 2 77 2 35 72 25/2 9/2 5/2 9/2Cu: ( 1 ) ( 1 ) Zn: ( 1 ) ( 1 )f g f g

3 5 7, , Allowed2 2 2

5 3 5 7, , First Forbidden2 2 2 2

1 9, First Forbidden Unique2 2

N Z

9/ 21g

5/ 21 f

3/ 22 p

1/ 22 p 9/ 21g

Key Factors:1. Available energy for decay.2. Ordering and energy of the single-

particle orbitals.3. Composition of the states

70 72 74 76 78 80 82 84 86 88

0

20

40

60

80

100

P n [

%]

A

GT+FF GT GT, Moeller 97

I.N. Borzov, Phys. Rev. C71, 065801 (2005).

Ni isotopes

How do you measure -delayed neutron emission?


1. Direct detection of neutron

1 corrn nb imp corr nd

nn imp

N r N NP

N e

NERO/NSCL P. Hosmer et al., Phys. Rev. C82, 025806 (2010)

Neutron Detector

Detector

ImplantationDetector

1 1 2 2

1 1 1 1 2 2 2 2

21 2

1 2

coincicence summing correction

absolute branching ratio

saturation fraction

n

s

BR

SF

A s A sNP N NN N BR SF BR SF

2. Indirect determination using rays

1 2

2 2

2 2 2 2

nmp

A sP

N BR SF

HRBIF

J. A. Winger et al., Phys. Rev. Lett. 102, 142502 (2009)S. V. Ilyushkin et al., Phys. Rev. C80, 054304 (2009)J. A. Winger et al., Phys. Rev. C81, 044303 (2010)S. Padgett et al., Phys. Rev. C82, 064314 (2010)

Holifield Radioactive Ion Beam Facility


+/-40 keV +/-160 keV

Mass separatorM/ΔM ~ 600

fission fragments

charge exchange cell (removes Zn)

Positiveions

IRIS-1

UCx54 MeV protons

ORIC

Ranging outexperiment

LeRIBSSexperiment

Isobar separatorM/ΔM ~ 10000

2-3 MeV/u

200 keV

Positive or negative ions

Tandem accelerator(negative ions only)

IRIS-2

Ranging Out Detector Station


Particle Identification Energy (1 keV/chn)

624 keV

84Ga

76Cu

76Ga76Ge

203 torr

76Cu 76Ga76Ge

76Cu598 keV

76Ga 563 keV

161 torr

Energy (0.5 keV/chn)

Ene

rgy

6th

Ano

de

Total Energy

76Ga 563 keV

76Cu598 keV

Excellent system for the direct measurement of absolute branching ratios.

Ion Chamber

CARDS Ge Array

Moving Tape Collector

Clarion ARay for Decay Spectroscopy

Low-energy Radioactive Ion Beam Spectroscopy Station


CARDS Ge ArrayMoving Tape Collector

MTC and CARDS frame built by Ed Zganjar (LSU)

1. Much higher beam currents since we do not use tandem. (Factor of ~20.)

2. The ability to use positive or negative ions.3. With positive ions, additional gain of ~10 from not

using charge exchange cell.4. Better effective mass resolving power for the high

resolution separator when using positive ions. Can achieve nearly pure beams.

5. Faster MTC drive allows study of shorter lived nuclides.

6. Higher beam intensity allows for detailed decay spectroscopy.

7. Higher beam intensity allows us to reach further from stability.

8. Possibility to implement tagging in the future.

HRIBF n-Decay Studies Near 78Ni


40 5045 54

Cu

Ni

Ge

Ga

Zn

As

78Ni

83Ga 84Ga

77Cu

81Zn

78Cu76Cu

HRBIF J. A. Winger et al., Phys. Rev. Lett. 102, 142502 (2009)S. V. Ilyushkin et al., Phys. Rev. C80, 054304 (2009)J. A. Winger et al., Phys. Rev. C81, 044303 (2010)S. Padgett et al., Phys. Rev. C82, 064314 (2010)

Co

82Zn

74Cu 75Cu

83Zn

85Ga

79Cu

*NERO/NSCL P. Hosmer et al., Phys. Rev. C82, 025806 (2010)

**

* ** *

* * *

* *

***

*

How it all works out.


Ex: 76,77 76,77 * 75,76Cu Zn Zn

n


76Zn199 keV

77Zn189 keV

75Zn228 keV


76Zn199 keV

76Cu

76Ga76Ge

RO Mode203 torr

76Cu 76Ga

76Ge

PT Mode161 torrE

nerg

y 6t

hA

node

Total Energy

76

6 6

77

3 3

4 25

24 23

21 19

78

8

5

27

8

23 5

83

Old

4.2

1

PT Sat. 7.3 7.0

RO 10.2 29 29

20.2 28 28.7

PT 7.2 31.5 34.0

Sat.

Adopt

7.

Experiment Theory

Nuclide Mode MTC Rel

9.7

New

7

32.1 28.5

PT 5.2 6

.2

30.0

65

62.8

42.6

2

40.4

50.5

. Abs

5

PT 20.2 6

.

4

Cu

Cu s

s

s

Cu s

Ga s

4

50.7

Sat

1 .7

. 61

5

It ain’t always that easy!


Major complications:1. Unknown or incorrect branching ratios.2. Unknown feeding through isomers.

J. A. Winger et al., Phys. Rev. Lett. 102, 142502 (2009) S. V. Ilyushkin et al., Phys. Rev. C80, 054304 (2009)

5/2- ground stateFlanagan et al., PRL103, 142501 (2009)

75Zn Level Scheme

Dr. Jeff Winger

(421) 19(4)%BR

1. Set limits on the absolute branching ratio.2. Identified the 1/2- isomer and the 9/2+

excited state

North American Workshop on Beta-Delayed Neutron Emission 5/3/2013

Dr. Jeff Winger

-decays of 83,84,85GaWinger et al., PRC81, 044303 (2010)

624 keV

107 keV85Ga at LeRIBSS, Feb. 2011 1. Refined the energy of the1/2+

state and identified the second excited state in 83Ge

2. Establish the 5/2- gs for 83Ga3. Established the energy of the

first 2+ state in 84Ge4. Observed the decay of 85Ga for

the first timeNorth American Workshop on Beta-Delayed Neutron Emission 5/3/2013


Results Pn values are consistently higher than previously reported for nuclides in this region.

The Future


0

20

40

60

80

100

0.001 0.01 0.1 1 10

Energy (MeV)

Eff

icie

ncy

(%)

HRIBF

long-counter

NERO

Neutron Efficiency by Ring

0

20

40

60

80

100

0.001 0.01 0.1 0.5 1 2 3 5

Energy (MeV)

Eff

icie

ncy

(%)

Ring 4

Ring 3

Ring 2

Ring 1

large -delayed neutron emission probabilities in the 78ni ... · j. a. winger et al., phys. rev....

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