Jacklyn M. Gates

Nuclear Science Division

Lawrence Berkeley National Laboratory

4th International Conference on the Chemistry

and Physics of the Transactinide Elements

5-11 September 2011, Sochi

Heavy Elements at LBNL

Recent Results Superheavy Elements

Heavy Element K-Isomers

New Stuff (in chronological order) CCC Detector Upgrade

GRETINA@BGS

Gas Catcher and Mass Analyzer

Laser Spectroscopy

Outline

118

117

116

288115 88 ms

287115 32 ms

115

114

282113 61 ms

284113 0.48 s

283113 0.10 s

278113 2 ms

113

277112 0.7 s

112

278111 4 ms

280111 3.59 s

279111 0.17 s

274111 15 ms

272111 3 ms

111

269110 130 s

110 270110 3 ms

271110 12 ms

273110 170 s

276109 0.72 s

275109 10 ms

274109 2.91 s

266109 2 ms

109 268109 25 ms

270109 3 ms

269108 14 s

268108 0.37 s

267108 68 ms

266108 4 ms

265108 2 ms

263108 23 ms

262108 260 s

108 270108 23 s

262107 0.10 s

261107 12 ms

260107 32 ms

107 266107

1 s

265107 0.94 s

264107 0.11 s

267107 17 s

270107 61 s

272107 9.79 s

106 259106 0.48 s

261106 0.23 s

263106 0.9 s

265106 21 s

264106 37 ms

262106 21 ms

260106 3.6 ms

259105 0.5 s

258105 4.4 s

105 260105 1.5 s

261105 1.8 s

262105 34 s

263105 27 s

267105 73.4 h

268105 15.9 h

266105 22 m

267104 77 m

258104 12 ms

257104 4.0 s

104 259104 3.0 s

260104 21 ms

261104 2 s, 78

s

285114 0.12 s

281112 97 ms

277110 5.7 ms

273108 0.25 s

269106 130 s

265104 105 s

277108 3 ms

103 256103 28 s

255102 3.1 m

254101 10 m

255101 27 m

256101 78 m

257101 5.52 h

253100 3 d

256100 158 m

259102 58 m

260103 180 s

259103 6.3 s

258102 1.2 ms

257103 0.65 s

258103 3.9 s

256102 2.91 s

257102 25 s

102

101

100 254100 3.2 h

255100 20 h

257100 100 d

258101 51.5 d

261103 39 m

262103 216 m

260102 0.11 s

259101 96 m

258100 370 s

259100 1.5 s

260101 31.8 d

290116 14 ms

271108 4 s

263104 8 s

294118 1 ms

293116 53 ms

292116 18 ms

291116 18 ms

287114 0.45 s

289114 2.70 s

288114 0.80 s

286114 0.12 s

282112 1 ms

284112 0.10 s

283112 3.83 s

285112 33.5 s

275108 0.19 s

271106 114 s

281110 9.6 s

279110 0.20 s

266106 0.32 s

267106 84 s

293117 14 ms

289115 0.22 s

285113 5.5 s

281111 26 s

294117 78 ms

290115 16 ms

286113 20 s

282111 0.51 s

278109 7.7 s

274107 0.9 m

270105 23 h

262104 0.19 s

Upper end of the chart of nuclides Since 1999, many reports of SHE formation

and decay from the DGFRS collaboration 48Ca + 238U, 237Np, 242,244Pu, 243Am, 245,248Cm, 249Bk, 249Cf

Until 2007, none were confirmed

238U(48Ca,3n)283112

SHIP @ GSI, (2007)

283112 chemistry after

Implied of 114

PSI @ Dubna, (2007)

MWAC

Focal PlaneDetector

PunchthroughDetector

RutherfordDetectors

QuadrupoleMagnet

Gradient-Field

Magnet

Flat-FieldDipoleMagnet

Target

EVRTrajectory

BeamTrajectoryBeam Gas-Filled

Chamber

Berkeley Gas-filled Separator

• Compound nucleus recoils are ejected from the target with the momentum of the beam

• In 0.5-Torr He, they experience many charge-changing collisions, giving 100% charge acceptance

• Average charge is (nearly) proportional to velocity, giving LARGE velocity acceptance

• Compound nucleus evaporation residues (EVRs) are focused on the detector array everything else has a

smaller magnetic rigidity, and takes a left turn

(2)

(3)

(1)

BGS upgrades for 242Pu(48Ca, 3-4n)287-286114

(1) 242PuO2 targets on 2.44- m Ti, 3.75” dia. wheel

(2) Radioactivity containment facility at BGS target

(3) Ge clover -ray detector behind BGS detectors

0.48 s

3.8 s

0.2 s

0.19 s

287114

283112

279Ds

275Hs

SF 90%

286114

282112

SF 50%

SF 100%

130 ms

0.82 ms

286114

282112

EVR, strip 14

7.73 MeV

13.0(2) mm

301 ms

3.6 ms

214.5 MeV

13.1(15)mm

287114

283112

279Ds

EVR, strip 7

11.55 MeV

-2.8(4) mm

176 MeV

-2.9(15)mm

0.815 s

1.921 s

0.185 s

Reported and observed decay properties

for 286114 and 287114

Decay modes, -energies, and lifetimes agree with published values.

Cross sections reported in 2009 were 1.4 pb each.

Small cross sections might be explained if B in He is > 2.3 Tm

Smaller than the 4.5 pb and 3.6 pb reported by the DGFRS group

Random rate analysis indicates fewer than 5 x 10-7

EVR- -SF and EVR- - -SF correlations should result from

random correlation of unrelated background events.

SHE are real and accessible at production rates of events/week.

With planned beam intensity upgrades at several accelerators: events/day!

B now known to be 2.29 Tm, B-field saturation in M2 . . . Our cross section is ~ 3.1 pb

First independent verification of

element 114 production

286114

282112

EVR, strip 16

14.4 MeV

-24.8(2) mm

76 ms

0.52 ms

205.4 MeV

-22.5(15)mm

286114

282112

SF 50%

SF 100%

130 ms

0.82 ms

Reported decay properties for 286114

One event seen from 242Pu(48Ca, 4n)286114

Observed

242Pu(48Ca,4-5n)286-285114 experiment (2010)

265Rf 30 s –

3.5 h

9.75 MeV

285114

13 ms

10.85 MeV

281Rg

200 ms

277Ds

41 ms

273Hs

100 ms

269Sg

30 s

10.13 MeV

10.15 MeV

8.68 MeV

Expected 285114 decay properties

based on extrapolation of

measured energies,

mass model predictions,

and t1/2 vs. Q

systematics 10.31 MeV

-1.1(15)mm

208 MeV, with one prompt and one delayed -ray

285114

181 ms

1.63 MeV (escape)

277Ds

8.2 ms

281Rg

140 ms

265Rf

152 s

273Hs

346 ms

269Sg

185 s

10.57 MeV

9.59 MeV

0.74 + 7.82

=8.56 MeV

EVR 16.1 MeV

-1.0(2) mm

1.2(17)mm

1.2(35) mm

-0.9(3)mm

-0.9(3) mm

-0.8(3) mm

Observed

decay chain

Comparison with

Q predictions of

Muntian, Patyk,

and Sobicziewski

Differences

(dotted lines)

show that a

revision of

calculated shell

effects may be

needed.

• SHE Z and A assignments are probably correct, but not proven.

• SHE Z and A assignments are based largely on mass models.

–Before using SHE Q to refine mass models,

–we better be sure the assignments are correct.

Z and A assignments techniques:

1) Decay to isotopes with well-established Z and A

2) Z-assignment by observation of characteristic x-rays

3) Direct measurement of mass

Positive Z and A Identification for SHE

118

117

116

288115 88 ms

287115 32 ms

115

114

282113 61 ms

284113 0.48 s

283113 0.10 s

278113 2 ms

113

277112 0.7 s

112

278111 4 ms

280111 3.59 s

279111 0.17 s

274111 15 ms

272111 3 ms

111

269110 130 s

110 270110 3 ms

271110 12 ms

273110 170 s

276109 0.72 s

275109 10 ms

274109 2.91 s

266109 2 ms

109 268109 25 ms

270109 3 ms

269108 14 s

268108 0.37 s

267108 68 ms

266108 4 ms

265108 2 ms

263108 23 ms

262108 260 s

108 270108 23 s

262107 0.10 s

261107 12 ms

260107 32 ms

107 266107

1 s

265107 0.94 s

264107 0.11 s

267107 17 s

270107 61 s

272107 9.79 s

106 259106 0.48 s

261106 0.23 s

263106 0.9 s

265106 21 s

264106 37 ms

262106 21 ms

260106 3.6 ms

259105 0.5 s

258105 4.4 s

105 260105 1.5 s

261105 1.8 s

262105 34 s

263105 27 s

267105 73.4 h

268105 15.9 h

266105 22 m

267104 77 m

258104 12 ms

257104 4.0 s

104 259104 3.0 s

260104 21 ms

261104 2 s, 78

s

285114 0.12 s

281112 97 ms

277110 5.7 ms

273108 0.25 s

269106 130 s

265104 105 s

277108 3 ms

103 256103 28 s

255102 3.1 m

254101 10 m

255101 27 m

256101 78 m

257101 5.52 h

253100 3 d

256100 158 m

259102 58 m

260103 180 s

259103 6.3 s

258102 1.2 ms

257103 0.65 s

258103 3.9 s

256102 2.91 s

257102 25 s

102

101

100 254100 3.2 h

255100 20 h

257100 100 d

258101 51.5 d

261103 39 m

262103 216 m

260102 0.11 s

259101 96 m

258100 370 s

259100 1.5 s

260101 31.8 d

290116 14 ms

271108 4 s

263104 8 s

294118 1 ms

293116 53 ms

292116 18 ms

291116 18 ms

287114 0.45 s

289114 2.70 s

288114 0.80 s

286114 0.12 s

282112 1 ms

284112 0.10 s

283112 3.83 s

285112 33.5 s

275108 0.19 s

271106 114 s

281110 9.6 s

279110 0.20 s

266106 0.32 s

267106 84 s

293117 14 ms

289115 0.22 s

285113 5.5 s

281111 26 s

294117 78 ms

290115 16 ms

286113 20 s

282111 0.51 s

278109 7.7 s

274107 0.9 m

270105 23 h

262104 0.19 s

Method 1) Connect to nuclides with well-established

Z and A: 232Th(48Ca,3-5n)275,276,277Ds (Z=110)

3n exit channel

produces 277Ds,

observed in recent 242Pu(48Ca,5n)285114

decay chain.

5n exit channel produces 275Ds,

which should decay to previously

known isotopes of Hs, Sg, and

Rf, linking the SHE to the rest of

the chart of nuclides.

Method 2) Z-assignment by observation

of characteristic x-rays

• -decay of odd or odd-odd nuclides could lead to K x-ray coincidences

• Simulations show that only 3 – K x-ray coincidences are needed for Z

identification at 95% confidence level

GSI-Lund: 243Am(48Ca,3n)288115

• Recent results from Dubna-LLNL-ORNL suggest that K x-rays may be

produced in decay to Mt

LBNL: 237Np(48Ca,3n)282113

• We prefer this reaction because it should result in positive assignments by

–method 1) - decay through well-established isotopes 262Lr and 262No

–method 2) - k x-ray coincidences in 282113, 278Rg, 274Mt, 270Bh, 266Db

–method 2) – EC decay of 262Lr followed by SF of 5-ms 262No

Coming up in a few minutes

Method 3) Direct measurement of mass

Isomer spectroscopy Z>100

254No

255Lr

256Rf

2000

100

12

PLB 690 19 (2010)

PRC 80 034324 (2009)

PRC 79 031303 (2009)

Studying the decay of isomers at BGS focal

plane

Determining properties for Z>100 nuclei such as

- single quasi-particle structure

- pairing strength

- deformation

- excitation modes

Testing the same models that predict properties

of super-heavy nuclei near Z=114, N=184.

20 30 40 50 60 70

Time ( s) C

ounts

/ 5

s

Electron energy (keV)

Counts

/ 1

0 k

eV

1

10

100 200 300 500 400 600 700

1

2

3

4

5

t1/2=9.6 ± 1.7 s

J.S. Berryman et al., PRC 81 064325 (2010)

261Sg

Seaborgium is at the current limit for spectroscopy measurements

261Sg Single Particle Isomer

• A new generation of experiments is underway addressing the

fundamental issue of the maximum limit of nuclear mass and charge.

254No

255Lr

256Rf 257Rf

255No 253No 252No 250No

250Fm

Z=101

102

103

104

105

106 261Sg

251Md

257Db

Known excited isomeric states in elements with Z>100

LBNL K-isomer(s)

K-isomer(s), other labs

245Fm 246Fm LBNL isomer(s) not observed

LBNL single-particle isomer

N=152

Summary

Recent Results Superheavy Elements

Heavy Element K-Isomers

New Stuff (in chronological order) CCC Detector Upgrade

GRETINA@BGS

Gas Catcher and Mass Analyzer

Laser Spectroscopy

Outline

New detector for increased sensitivity in

K-isomer and SHE experiments

CCC Clover Detector Positioning

event

type

eff.

1 DSSD

1 clover

C3 eff.

3 DSSDs

3 clovers

eff.

gain

recoil 50% 87% 1.74

50% 92% 1.84

122 keV Kx

900 keV

16%

4.0%

30%

7.5% 1.88

recoil- 900-

(K-isomer) 1.0% 6.0% 6.0

Recoil- -Kx

(SHE Z id.) 4.0% 24.% 6.0

Efficiency gains with

new DSSD configuration

GRETINA@BGS Project

• Gamma-ray energy tracking array

• Covering ¼ of 4 solid angle with

28 segmented Ge crystals

• Mechanical support structure

• Acquisition system

In-beam spectroscopy exp: 208Pb(48Ca,2n)254No,

•10x statistics improvement 208Pb(50Ti,1-2n)257,256Rf,

•highest-Z for in beam spect.

seven 4-crystal modules

efficiency similar to GS

-ray track reconstruction

6-month campaign

GRETINA@BGS Expeiments, Fall 2011

GRETINA@BGS installation

Mass Analysis and Detector Facility

Mass selection

Detector system

• Provides means of mass identification of superheavy nuclei behind

gas-filled spectrometer

• remove recoils from focal plane

• deliver small beam spot to detector

• Contracted with Guy Savard at ANL to provide gas catcher and RFQs

• Currently designing two different mass analyzers

Trochoid Separator

+ +

+ +

+ +

+ +

+

- - - - - - - -

-

Trochoid Separator

RF

catcher

RFQ

trap

60

beamline

Trochoid

mass

separator

re-configured

cave wall

C3 detector

station

BGS

det. box

Mass Analysis Detector Facility Layout

Technique 1) Stop ions in a buffer gas cell.

2) Collect charged ions on Ta filament.

3) Re-evaporate as neutral atoms.

4) Two- or three-step laser ionization.

5) Collect ions on -detector & watch decay.

Science a) Ionization energies

b) Isotope shifts

c) Nuclear magnetic moments

d) Quadrupole moments

No excitation scheme comparison w/ atomic theory

[Xe]4f146s2 1S0 [Rn]5f147s2 1S0

Heavy Element Laser Spectroscopy

Summary and Conclusions

What we have done:

• Confirmation of element 114

• New isotope of 114 and its daughters

• Isomer studies on 11 nuclides

In the near future:

• New CCC focal plane detector currently being commissioned

• GRETINA@BGS beginning September 2011

• Building and commissioning new mass analysis and detector

facility beginning in Summer 2012

• Laser spectroscopy beginning in 2014