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Decay studies of exotic nuclei
Krzysztof P. RykaczewskiPhysics 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 Japanbut I had several joint publications with Japanese collaborators before:
“Beta decay of 20Mg”, Nucl. Phys. A 584, 509, 1995with 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 2004with 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”
many results on new and important s-isomers obtained afterwards at GANIL (LISE), GSI (FRS) , NSCL(A1900)
and more recently at RIKENsee, e.g., Kameda, Kubo,.. et al, PR C86, 054319, 2012
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-isomersR. 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, 1997R. Grzywacz et al., Phys. Lett. B355, 439, 1995
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 Facilitycapable to produce and study nuclei at the neutron-rich
and proton-rich limits of nuclear landscape
IRIS-1
IRIS-2
ORIC
lasers
isobarseparator
Tandem
RMS
OLTF
= Holifield Radioactive Ion Beam Facility at Oak Ridge (1996 - 2012)
proton-induced fission of 238Ucreates 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)
J.R. Beene et al., J. Phys. G: Nucl. Part. Phys. 38, 024002, 2010
Decay studies of fission products at the
Range outexperiment
LeRIBSSexperiment
+/-40 keV+/-160 keV
Isobar separator M/M ~ 10000
Mass separatorM/ΔM ~ 1000
54 MeV protons12- 18 A
2-3 MeV/u
200 keV
charge exchange cell
(removes Zn, Cd)0% - 40% efficiency
typically 5% efficiency
Positiveions
Positive or negative ions
Tandem accelerator
(negative ions only)
~ 10% efficiency
IRIS-1
ORIC : ~6 g 238U
fission fragments
~1011/s
~7 % ~70%
gas cell
IRIS-1 and IRIS-2, laser ionization
beam kicker En
erg
y l
os
sTotal ion energy
76Cu
76Ga
76Ge
no 76Zn !!!
Range out expgas cell spectra
C.J.Gross et al., EPJ A25,115,2005
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
A variety of beam purification methods
selectivelaser ionization
Detectors for beta decay studies CARDS β- at LeRIBSS VANDLE n-TOF array at LeRIBSS
Hybrid 3Hen-β- array at LeRIBSS
εn~30%
3Hen array after “ranging-out”
850 liters of 3He at 10 atm
εn~80%
Ed Zganjar, LSURobert Grzywacz, UTK
nearly 80% efficient and segmented 3Hen neutron counter
ORNL, UTK LSU , Mississippi
UNIRIB
850 liters of 3He at 10 atm
εn~80%
Detectors for beta decay studies 2200 pounds of NaI(Tl) - Modular Total Absorption Spectrometer
(MTAS)and its 12,000 pound shielding
Decays studied at HRIBF Tandem-OLTF-MTAS are marked by yellow squares.
Labels “1” and “2” indicate the priorityfor decay heat measurements established
by the Nuclear Energy Agency (NEA) in 2007
January 2012
Beta decay of very neutron-rich nuclei is very rich in interesting features
β and MTAS
neutron detection
3Hen, VANDLE
22 parent radioactivities in 78Ni region studied by means of β spectroscopy at the HRIBF 78Ni to 132Sn region (~ 10), + MTAS (22), + VANDLE (29)
80As
79Ge
78Ga
77Zn
76Cu
75Ni
81As
80Ge79Ga
78Zn
77Cu
76Ni
82As
81Ge
80Ga
79Zn
78Cu
77Ni
83As
82Ge81Ga
80Zn
79Cu
78Ni
84As
83Ge82Ga
81Zn
80Cu
79Ni
85As
84Ge
83Ga
86As
85Ge84Ga
87As
86Ge
85Ga
83Se 84Se 85Se 86Se 87Se 88Se
82Zn 83Zn
Z=28
N=50
79As
78Ge77Ga
76Zn
75Cu
74Ni
78As
77Ge
76Ga
75Zn
74Cu
73Ni
86Ga
88As
87Ge
89Se
77As
76Ge75Ga
74Zn
73Cu
72Ni
D. Miller, R Grzywacz et al., to be published
~ 2 days exp
detected 79Cu ions:NSCL 2005 (2010): 754HRIBF 2006: ~16 000RIKEN 2010: ~ 10 000HRIBF 2011: ~158 000
81Zn
81Ga
78Ni
79Cu
79Zn
initial yields : 79Zn ~ 105 pps 79Cu+ ~ 40 pps
after charge exchange : 79Zn 0.0 pps 79Cu- ~ 2 ppspure beam of 79Cu ions → single neutron-hole states in N=49 79Zn
78Zn
79Cu decay (HRIBF LeRIBSS) N=50
0.29(2) s
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- 730 keV)
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)
similar conclusions: P. Hosmer, H. Schatz et al., PR C82 , 025806, 2010
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
all βn-precursorsgiven in this plot
have T1/2 < 1 s
Delayed Neutron Yield following 235U fission
0.1 1 10 10010-6
10-5
10-4
10-3
10-2
Del
ayed
neu
tron
yie
ld (
n/s/
fissi
on)
Time after fission (s)
ORIGEN Keepin (IAEA 6 group)
Integral β,n measurementsused for reactor analysis
-n isotopic decay data
ORIGEN is missing data for very short-lived
fission products
from Ian C. Gauld, ORNL Reactor Science Group (2010)
Note log scales !
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 -energy release from highly excited states in current data base !
MTAS-revised decay of 139Xeaverage -energy release
increased from 935 keV to 1146 keV (23%)
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.
http://www.ornl.gov/sci/casl/
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)
79Cu, 81,82,83Zn, 85,86Ga, 86Ge, 86,87As .....
β spectroscopy - new beta decays
83Ge
81Zn
83Ga
84Ge
81Ga
78Ni
82Zn
84Ga
85Ge
85Ga
79Cu
83Zn
86Ga
86Ge
82Ga
117 ms228 ms304 ms
93 ms85 ms
226 ms
87As86As484 ms
494 ms
290 ms
molecular beams GeS, AsS
~ 3 ions/s, April 2012 pure Ga beams from
laser ion sourceand hybrid 3Hen array
861ms
Departing from 78Ni into a deformed region β-half-lives of 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)
experiment
FRDM Moeller 2003
DF3a+CQRPA Borzov 2011
M. Madurga et al., Phys. Rev. Letters, 109, 112501, 2012
+ post r-process abundances
simulations with Moeller’sT1/2’s
simulations with Borzov’s T1/2’s
R. Surman 2012
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
Emerging N=58 d5/2-s1/2 subshell ? (energy of s1/2 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
-200
0
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
28 30 32 34 36 38 40 42 44 46 48 50 52
Z
E (
ke
V)
1g7/2
3s1/2
2d5/2
Darby, Grzywacz et al.,PRL 105, 162502,2010 101Sn-103Sn-105Sn ...
Padgett , Madurga, Grzywacz et al., 81Zn decay,PR C82, 064314, 2010
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 ...)
82Cu
Qβ~ 17 MeVT1/2 ~ 60 ms
82Zn
81ZnN=51
Sn~ 5 MeVs1/2
d5/2
0+
(4-,5-)
βn
~ 0.6 MeV
with 100 part*nA of relativistic 238U beam (RIKEN, FRIB ?) we can go for more ambitious study of
80Co βn-decay to the s1/2 excited state in N=51 79Ni
T.Ohnishi,T.Kubo .. JPSJ 2010
0.2 pnA 238U
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
SummaryDecay 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 + n-branching ratio
2. Measurements with Modular Total Absorption Spectrometer MTASMTAS energy spectra in segmented array → beta strength within -window (decay heat)
3. Measurements involving 3Hen and VANDLE → -delayed neutronsβn-intensities and βn-energy spectra /Robert Grzywacz/ → beta strength above neutron separation energy
Combining high-res -data, 3Hen, MTAS, VANDLE → determination of a full -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. StracenerUT 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-CichockaMississippi : J. A. Winger, S. Ilyushkin Louisiana : Ed Zganjar, B.C. Rasco UNIRIB : J.C. Batchelder , S. H. LiuVanderbilt : N. Brewer, J.H. Hamilton, J.K. Hwang, A. Ramayya, C. GoodinWarszawa : 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 FactoryCollege Station, TX, 12-13th March 2013
about 12 mg to 15 mg of actinide material is needed for one SHE target
Fm
E s
F m 254 F m 255 F m 256
SF
F m 257
Es 254 Es 255
- EC -
CfC f 249
, (n ,f)
C f 250 C f 251 C f 253 C f 254
, ,
, (n ,f) ,
B k 249B k
Bk 250 Bk 251
-
C m 242
A m
Cm
Pu 246
C m 243
Pu 239
, (n ,f)
, (n ,f)
C m 244 C m 245
, (n ,f)
C m 246
, (n ,f)
C m 247
, SF
C m 248
SF
C m 249 C m 250
Pu 240
N p 237
Pu 238 Pu 241 Pu 242 Pu 243
N p 238
Pu 244 Pu 245
-, (n ,f)
, (n ,f)-
Am 241
, EC-
Am 242 Am 243 Am 244 Am 245 Am 246
94
93
95
96
N
Z
98
97
100
99
SF
--
-
---
- - -P u
Np
Es 253
C f 252
, SF
243Am/244Cm/248Cm seed material and its n-capture/decay path
to 249Bk, 252Cf,253,254Es and 257Fm
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
(+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, 2013and submitted to PR C.
(+1 TASCA)
(+1 TASCA)
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
dead time~ 11 s
dead time~ 0.3 s
UTK Digital Signal Processing Laboratory
SHIP analog data acquisition
recoil
recoil
GSI Annual Report 2011 (2012)
New ORNL-UTK detectors and digital data acquisition system
MICRON detectors
128 x48 mm,1 mm strips 300m DSSD
500 m single Si-vetomatching DSSD design
six 120 x 65 mm single Si300 m Si-box
MESYTEClin-log preampsISEG NIM HV
XIA Pixie16 rev D(208 channels)
Dell Power Edge
(similar DAQ at SHIP Z=120 exp was serving PSSD+Si-box+MCPs)
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, 2013Spontaneous fission modes and lifetimes of superheavy nuclei
in the nuclear density functional theory
284Fl (4n,240Pu)
296118 (3n,251Cf)
only even-even nuclei plotted here
?
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.