Transcript Slide 1

Decay studies of exotic nuclei
Krzysztof P. Rykaczewski
Physics Division, Oak Ridge National Laboratory
Oak Ridge, Tennessee
exotic nuclei:
- fission products of 238U
- super heavy nuclei produced in hot fusion
It is my first trip to Japan
but I had several joint publications with Japanese collaborators before:
“Beta decay of 20Mg”, Nucl. Phys. A 584, 509, 1995
with S. Kubono and T. Nakamura
GANIL LISE exp in 1991
decay data relevant for the break-out from CNO cycle
several papers from 1998 to 2004
with M. Shibata
Total Absorption Spectroscopy at GSI ISOL facility performed
with M. Nitschke’s (Berkeley) TAS by Warsaw -Valencia-GSI teams
“True Gamow-Teller strength distribution around 100Sn and 146Gd”
Early work in GANIL on 20Mg triggered the expansion of GSI ISOL program
of Gamow-Teller β-transitions studies near 100Sn to fragmentation reactions.
It resulted the identification and studies of s-isomers
R. Grzywacz et al.,Phys. Lett. B 355, 439,1995; PR C55, 1126, 1997; PRL 81, 766, 1998
R. Grzywacz et al., Phys. Rev.C55, 1126, 1997
R. Grzywacz et al., Phys. Lett. B355, 439, 1995
many results on new and important s-isomers obtained afterwards
at GANIL (LISE), GSI (FRS) , NSCL(A1900)
and more recently at RIKEN
see, e.g., Kameda, Kubo,.. et al, PR C86, 054319, 2012
among motivations of the HRIBF
decay studies of fission products :
- understanding the evolution of nuclear structure
-- single-particle levels around shell gaps
-- beta strength function related to the structure of parent and daughter states
beta-decay data for the analysis of post r-process isotopic
distributions and nuclear fuel cycle
-
------
half-lives
properties of beta-delayed neutron emission
decay heat
antineutrino energy spectra (deduced from true β-transition probabilities)
low-energy states, isomers ...
HRIBF based decay studies of fission products
substantially contributed
to our understanding of neutron-rich nuclei
Holifield Radioactive Ion Beam Facility
capable to produce and study nuclei at the neutron-rich
and proton-rich limits of nuclear landscape
ORIC
Tandem
IRIS-1
OLTF
IRIS-2
RMS
isobar
separator
lasers
= Holifield Radioactive Ion Beam Facility
at Oak Ridge (1996 - 2012)
J.R. Beene et al., J. Phys. G: Nucl. Part. Phys. 38, 024002, 2010
proton-induced fission of 238U
creates a lot of neutron-rich nuclei
for spectroscopic studies
86Ga:
HRIBF: ~10,000/hour at 15 A protons
pure beam at the HRIBF !
RIKEN:10/hour at 0.2 pnA 238U
(now ~ 5 pnA)
Decay studies of fission products at the
IRIS-1 and IRIS-2,
IRIS-1laser ionization
Mass separator
M/ΔM ~ 1000
fission fragments
~1011/s
~6 g 238U
ORIC : 54 MeV protons
12- 18 A
+/-40 keV
charge exchange cell
(removes Zn, Cd)
0% - 40% efficiency
typically 5% efficiency
Positive
ions
+/-160 keV
eg~7 % eb ~70%
g
g
b
g
Tandem accelerator
(negative ions only)
~ 10% efficiency
g
200 keV
LeRIBSS
experiment
Range out
experiment
gas
cell
2-3 MeV/u
C.J.Gross et al.,
EPJ A25,115,2005
Isobar separator
M/DM ~ 10000
Positive or negative
ions
beam kicker
Range out exp
gas cell spectra
Energy loss
b
76Cu
no 76Zn !!!
76Ga
76Ge
Total ion energy
A variety of beam purification methods
selective
laser ionization
two-stage magnetic separation:
from molecular beams like A=118 86Ge32S+
to pure “nominal mass A ” ion beam
example: new 84-86Ge,84-87As- results
Detectors for beta decay studies
CARDS β-g at LeRIBSS
VANDLE n-TOF array at LeRIBSS
Ed Zganjar, LSU
3Hen array after “ranging-out”
Hybrid 3Hen-βg array at LeRIBSS
Robert Grzywacz,
UTK
εn~80%
850 liters of 3He at 10 atm
εn~30%
nearly 80% efficient and segmented
3Hen
neutron counter
εn~80%
ORNL, UTK
LSU , Mississippi
UNIRIB
850 liters of 3He at 10 atm
Detectors for beta decay studies
2200 pounds of NaI(Tl) - Modular Total Absorption Spectrometer (MTAS)
and its 12,000 pound shielding
January 2012
Decays studied at HRIBF Tandem-OLTF-MTAS
are marked by yellow squares.
Labels “1” and “2” indicate the priority
for decay heat measurements established
by the Nuclear Energy Agency (NEA) in 2007
Beta decay of very neutron-rich nuclei
is very rich in interesting features
neutron
detection
3Hen, VANDLE
βg and MTAS
22 parent radioactivities in 78Ni region studied by means of βg spectroscopy at the HRIBF
78Ni to 132Sn region (~ 10), + MTAS (22), + VANDLE (29)
Z=28
83Se
84Se
85Se
86Se
87Se
88Se
89Se
77As
78As
79As
80As
81As
82As
83As
84As
85As
86As
87As
88As
76Ge
77Ge
78Ge
79Ge
80Ge
81Ge
82Ge
83Ge
84Ge
85Ge
86Ge
87Ge
75Ga
76Ga
77Ga
78Ga
79Ga
80Ga
81Ga
82Ga
83Ga
84Ga
85Ga
86Ga
74Zn
75Zn
76Zn
77Zn
78Zn
79Zn
80Zn
81Zn
82Zn
83Zn
73Cu
74Cu
75Cu
76Cu
77Cu
78Cu
79Cu
80Cu
72Ni
73Ni
74Ni
75Ni
76Ni
77Ni
78Ni
79Ni
N=50
79Cu
decay (HRIBF LeRIBSS)
~ 2 days exp
N=50
81Ga
78Zn
79Zn
81Zn
79Cu
0.29(2) s
78Ni
79Zn ~ 105 pps 79Cu+ ~ 40 pps
initial yields :
after charge exchange : 79Zn 0.0 pps 79Cu- ~ 2 pps
pure beam of 79Cu ions → single neutron-hole states in N=49 79Zn
detected 79Cu ions:
NSCL 2005 (2010): 754
HRIBF 2006: ~16 000
RIKEN 2010: ~ 10 000
HRIBF 2011: ~158 000
half-life of 79Cu
Kratz 1991 : 188(25) ms (multi βn fit)
Hosmer 2010 : 257(+ 29,- 26) ms (ion-β)
Miller 2013: 290(20) ms (β-g 730 keV)
D. Miller, R Grzywacz et al., to be published
Beta-delayed neutron emission:
counting identified ions → absolute branching ratios
HRIBF results pointed to much higher β-delayed neutron branching
ratios in comparison to earlier measurements and calculations
see, e.g., Pfeiffer, Kratz, Moeller (PKM 2002) Progress in Nucl. Energy, 41, 5 (2002)
all βn-precursors
given in this plot
have T1/2 < 1 s
J. Winger et al., PRL 102, 142501 (2009)
PRC 80, 054304,2009; PRC 81,044303,2010;
PRC 82, 064314 (2010); PRC 83, 014322 (2011); PRC 86, 024307,2012
similar conclusions: P. Hosmer, H. Schatz et al., PR C82 , 025806, 2010
Delayed Neutron Yield following 235U fission
Integral β,n measurements
used for reactor analysis
Delayed neutron yield (n/s/fission)
10-2
10-3
b-n isotopic decay data
Note log scales !
ORIGEN is missing data
for very short-lived
fission products
10-4
10-5
ORIGEN
Keepin (IAEA 6 group)
10-6
0.1
1
10
100
Time after fission (s)
from Ian C. Gauld, ORNL Reactor Science Group (2010)
Example of MTAS data – 139Xe decay (A. Fijałkowska et al., ND2013)
(139Xe ~5% cumulative fission yield for nth+ 235U)
MTAS data (black) compared to
ENDSF-based simulations (red).
Lack of β-feeding and following
g -energy release from highly excited
states in current data base !
MTAS-revised decay of 139Xe
average g-energy release
increased
from 935 keV to 1146 keV (23%)
http://www.ornl.gov/sci/casl/
May 2010 : the Department of Energy creates the first nuclear energy
innovation hub -- the Consortium for Advanced Simulation of Light Water
Reactors (CASL) -- headquartered at Oak Ridge.
The first task will be to develop computer models that simulate nuclear
power plant operations, forming a "virtual reactor" for the predictive simulations
of light water reactors. Other tasks include using computer models to reduce
capital and operating costs per unit of energy, safely extending the lifetime of
existing U.S. reactor and reducing nuclear waste volume generated by enabling
higher fuel burn-ups.
We should remember that even the very best simulations of
nuclear fuel cycles require correct experimental input data.
“Conquering nuclear pandemonium”
KR’s Viewpoint in Physics, 3, 94, 2010
(credit to A. Algora et al., PRL 105, 202501, 2010)
βg spectroscopy - new beta decays
79Cu, 81,82,83Zn, 85,86Ga, 86Ge, 86,87As
.....
molecular beams
GeS, AsS
83Ge
84Ge
861ms
484 ms
86As
87As
494 ms
226 ms
85Ge
86Ge
85 ms
81Ga
82Ga
304 ms
81Zn
290 ms
79Cu
78Ni
83Ga
228 ms
82Zn
84Ga
93 ms
85Ga
86Ga
117 ms
83Zn
~ 3 ions/s, April 2012
pure Ga beams from
laser ion source
and hybrid 3Hen array
Departing from
β-half-lives of
78Ni into a deformed region
84,85,86Ge and 84,85,86,87As isotopes
C. Mazzocchi , KR, et al., → Phys. Rev. C87, 034315, 2013
I.N. Borzov’s DF3a+CQRPA
Exp half-lives → β-theory
→ r-process
(HRIBF measurements → I.Borzov’s analysis → R.Surman’s modeling)
M. Madurga et al., Phys. Rev. Letters, 109, 112501, 2012
R. Surman 2012
+ post r-process abundances
experiment
FRDM Moeller 2003
DF3a+CQRPA Borzov 2011
simulations with Moeller’sT1/2’s
simulations with Borzov’s T1/2’s
Evolution of single-particle states beyond N=50
evolution of neutron 3s1/2 vs 2d5/2 states in N=51 isotones (N=58 sub-shell closure)
see J. Dobaczewski’s global calculations along N=50 isotones
in J. Winger, KR, .. et al., PR C 81, 044303, 2010
(energy of s1/2
Emerging N=58 d5/2-s1/2 subshell ?
state dropping down towards d5/2 gs for n-rich nuclei)
Neutron states in N=51 isotones, from Z=30 81Zn to Z=50 101Sn
3000
2800
2600
n1g7/2
2400
2200
n3s1/2
2000
n2d5/2
E (keV)
1800
1600
1400
1200
1000
800
600
Darby, Grzywacz et al.,
PRL 105, 162502,2010
101Sn-103Sn-105Sn ...
400
200
0
-200
28
30
32
34
36
38
40
42
Z al.,
Padgett , Madurga, Grzywacz et
81Zn decay,PR C82, 064314, 2010
44
46
48
50
52
Interesting experiment for RIKEN: 82Cu β-decay to s1/2 state in N=51 81Zn
( 80,81,82Cu β-decay experiments were accepted at the HRIBF, but ...)
T.Ohnishi,T.Kubo .. JPSJ 2010
0.2 pnA 238U
82Cu
(4-,5-)
Qβ~ 17 MeV
T1/2 ~ 60 ms
βn
Sn~ 5 MeV
~ 0.6 MeV
81Zn
s1/2
d5/2
N=51
0+
82Zn
with 100 part*nA of relativistic 238U beam (RIKEN, FRIB ?) we can go for
more ambitious study of
80Co βn-decay to the s
79Ni 
1/2 excited state in N=51
Beta-delayed multi-neutron emission
Decay of N=55 86Ga studied with “hybrid 3Hen” at LeRIBSS in April 2012. Pure and intense beams
of 83,85,86Ga isotopes were produced at the IRIS-2 RIB platform using laser ion source RILIS
Y. Liu et al., Nucl. Instr. Meth. Phys. Res. B298, 5, 2013.
pure beams: 100 pps of 85Ga, ~ 1- 3 pps of 86Ga
Summary
Decay studies of fission products at the HRIBF created
a lot of new and reliable data on fission products decays
1. High energy resolution measurements with pure beams
of known intensities (when post accelerated)
ranging-out technique and gamma-beta-conversion electron detectors
→ basic “high energy resolution” decay scheme + bn-branching ratio
2. Measurements with Modular Total Absorption Spectrometer MTAS
MTAS energy spectra in segmented array
→ beta strength within bg-window (decay heat)
3. Measurements involving 3Hen and VANDLE → b-delayed neutrons
βn-intensities and βn-energy spectra /Robert Grzywacz/
→ beta strength above neutron separation energy
Combining high-res g-data, 3Hen, MTAS, VANDLE
→ determination of a full b-strength function and its consequences
→ comparison with theory and further development of modeling
2008-2012 LeRIBSS – OLTF (MTAS) HRIBF campaigns
ORNL : C.J. Gross, Y. Liu, T. Mendez, K. Miernik, KR , D. Shapira, D. Stracener
UT Knoxville : R. Grzywacz, K.C. Goetz, M. Madurga, D. Miller, S. Paulauskas,
S. Padgett, L. Cartegni , A. Fijałkowska, M. Al-Shudifat and C.R. Bingham
ORAU/ORNL : C. Jost, M. Karny, M. Wolińska-Cichocka
Mississippi : J. A. Winger, S. Ilyushkin
Louisiana : Ed Zganjar, B.C. Rasco
UNIRIB : J.C. Batchelder , S. H. Liu
Vanderbilt : N. Brewer, J.H. Hamilton, J.K. Hwang, A. Ramayya, C. Goodin
Warszawa : A. Korgul , C. Mazzocchi
Kraków : W. Królas IAEA: I. Darby NSCL-MSU: S. Liddick
+ VANDLE collaboration (talk by R. Grzywacz)
theoretical analysis :
I.N. Borzov (JIHIR/Dubna/Obninsk), K. Sieja (Strasbourg), R. Surman(NY-JINA)
R. Grzywacz (UTK), J. Dobaczewski (Warszawa/Jyväskylä)
Studies of Super Heavy Elements
ORNL, Oak Ridge
~ 250 mg
252Cf
~ 8 g
254Es
J. Roberto et al., workshop on SHE studies at the Dubna SHE Factory
College Station, TX, 12-13th March 2013
about 12 mg to 15 mg of actinide material is needed for one SHE target
243Am/244Cm/248Cm
seed material
and its n-capture/decay path
to 249Bk, 252Cf,253,254Es and 257Fm
100
Fm 254
Fm
Fm 255
Fm 256
SF
99
98
Cf 249
Cf
Es 253
Es
, -, EC
Cf 250
, (n,f)
97
96
Cm
Cm 242
Cm 243
Cm 244
, (n,f)
95
94
Pu
Pu 238
Am
Pu 239
, (n,f)
Z
93
Np
N
Np 237
Np 238
Am 241
Am 242
Pu 241
-, (n,f)
Cm 245
Cm 246
, (n,f)
Am 243
-, EC
Pu 240
Bk 249
Bk
Am 244
-
Pu 242
Pu 243
-
Am 245
Pu 244
Cm 247
Cm 248
, (n,f)
, SF
Am 246
Pu 245
-
Es 254
Pu 246
-
Cf 251
Cf 252
, (n,f)
,, SF
Bk 250
Bk 251
Cm 249
-
Cm 250
SF
Cf 253
-, (n,f)
Es 255
Cf 254
SF
Fm 257
2012 – a very good year for SHE studies !
see 278113 among the “Inventions of the year 2012” according to Time magazine
(most experiments were performed with ORNL-made actinide target materials)
16
(+1 TASCA)
(+1 TASCA)
(+25 TASCA)
(+1 TASCA)
Yu.Ts. Oganessian et al.,
PRL 104, 142501, 2010; PRL 108, 022502, 2012; PRL 109, 162501, 2012; PR C 87, 014302, 2013
and submitted to PR C.
new experiments at SHIP (GSI Darmstadt)
•
248Cm+54Cr, 33 out of 140 days, April-May 2011 (also 2012), beam dose ~5*1018
-
search for isotopes of new element Z=120, 298,299(120)178,179 (T1/2 ~ 3 s)
-
expected short -decay half-life required ORNL/UTK fast digital electronics
-
cross section limit of about 560 femtobarn reached at ~ 400 pnA beam current
GSI Annual Report 2011 (2012)
SHIP analog data acquisition

dead time
~ 11 s
recoil
UTK Digital Signal Processing Laboratory
recoil
dead time
~ 0.3 s
New ORNL-UTK detectors and digital data acquisition system
(similar DAQ at SHIP Z=120 exp was serving PSSD+Si-box+MCPs)
MICRON detectors
128 x48 mm,1 mm strips
300m DSSD
500 m single Si-veto
matching DSSD design
six 120 x 65 mm single Si
300 m Si-box
MESYTEC
lin-log preamps
ISEG NIM HV
XIA Pixie16 rev D
(208 channels)
Dell Power Edge
LF 250 flange
Preparations for experiment searching for 293(118), 295(118) and 296(118)
isotopes with ORNL’s mixed-Cf target , new ORNL/UTK detection system
and 48Ca beam at Dubna.
(50% of 249Cf, 35% of 251Cf and 15% of 250Cf and very low content of 252Cf)
Experiment with 48Ca beam and 240Pu ORNL target material at Dubna
TSF ~10-100 s ?
Staszczak, Baran, Nazarewicz; Phys. Rev. C 87, 024320, 2013
Spontaneous fission modes and lifetimes of superheavy nuclei
in the nuclear density functional theory
only even-even nuclei plotted here
284Fl
(4n,240Pu)
?
296118
(3n,251Cf)
Summary for the SHE section:
1. Impressive SHE harvest in 2012 at JINR , GSI and RIKEN !
2. ORNL-made actinide materials are used to make “SHE targets”.
New mixed-Cf target can help to reach the heaviest atomic nuclei,
the isotopes of element 118
3. Digital data acquisition system, initially developed
for the studies of s- proton emitters at the HRIBF RMS
(R. Grzywacz et al., UTK Digital Pulse Processing Laboratory),
continues to be a system of choice in other experiments including
the synthesis of super-heavy nuclei and fragmentation-based
spectroscopy.
4. Experiment s on new short-lived super heavy nuclei
with 48Ca beam (44Ca, 40Ca) and 240Pu (239Pu, 245Cm, 248Cm..)
can help to connect nuclear mainland to the “Hot Fusion Island”
and provide important data on fission/alpha competition.