mass measurements and nuclear structure

G. Bollen, INTC-NUPAC Meeting, CERN, Geneva, October 2005

Overview and Motivation

Mass Measurements at

ISOLDE …

… and elsewhere

Conclusions

Mass Measurements and Nuclear Structure

G. BollenNational Superconducting Cyclotron Laboratory NSCL

Michigan State University


Rare Isotope Physics - an expedition by far not completed!

Limit of neutron-rich nuclei?

Limit of proton-rich nuclei?

Known Nuclei

HeaviestElements?

Possible

Nuclei

Binding energies determine limits of existence


How do mass measurements contribute?

Magic Numbers Evolution of Shell Structure

Magic Numbers Evolution of Shell Structure

Halos and SkinsHalos and Skins

Isospin SymmetryPairingExotic decaysFundamental Interactions

Isospin SymmetryPairingExotic decaysFundamental Interactions

r-processr-process

rp-pro

cess

rp-pro

cess

Stability of SHEStability of SHE


Constraints for nuclear models

50 60 70 80 90 100 110 120 130 140

-10

-8

-6

-4

-2

0

2

4

6

8

10

Sp = 0 S

n = 0r-process

constraints for nuclear mass models

known masses

exp DusCZ Molal ComKZ SatNa Tachi SpaJo JaneMass MassJane Duflo LZe76 Pearson FRDM93 TF94 DuZu94m

odel

diff

eren

ce (

MeV

)

N (Z = 55)


Nuclear Structure and Masses

835

840

845

850

855

860

865

In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr

Z (A = 100 isobars)

BIN

DIN

G E

NE

RG

Y (

MeV

) total binding energies

shell closure subshell deformationFe

Cs

50 56

two-neutron separation energies

Systematic study of masses – first indicator of new nuclear structure effectsSystematic study of masses – first indicator of new nuclear structure effects


Tools for mass measurements on rare isotopes

Time-of-flight spectrometry

single turn: SPEG, TOFI

multi turn: cyclotrons CSS2, SARA,storage ring ESR

Conventional mass spectrometry

CERN-PS + ISOLDEChalk-RiverSt. Petersburg

Frequency measurements

storage ring ESR/GSI, future NESR, RIBF rings

RF transmission spectrometer MISTRAL/ISOLDE

Penning traps ISOLTRAP/ISOLDE, LEBIT/NSCL, JYFLTRAP/JYFL, CPT/ANLSHIPTRAP/GSI, TITAN/TRIUMF,

MAFFTRAP/Munich

c = q/m B

Out of Stock

Out of Stock

+ Q-values from reactions and decays


106

103

100

10-3

10-9

10-8

10-7

10-6

10-5

10-4

JYFL COOL

CPT

ESR SMS

ISOLTRAP

ESRIMS

MISTRAL

CSS2

SPEG

rela

tive

unce

rtai

nty

half life (seconds)

D. Lunney et al., Rev. Mod. Phys. 75, 1021 (2003). half life (seconds)

Time-of-Flight

TOF Schottky

RF-Spectrometer

Penning Trap

TOF Isochronous

LEBIT

Comparison of Methods


Mass measurements far from stability at CERN

- CERN pioneered direct mass measurements far from stability- Na isotopes (SPS) discovery of island of inversion

- 11Li (SPS) first loosely bound exotic nucleus discovered

- Rb isotopes (ISOLDE) first subshell closure observed in long isotopic

chains

- ISOLDE pioneered new techniques for short-lived isotopes- Penning trap mass spectrometry + many related techniques (ISOLTRAP)

- RF mass spectrometry (MISTRAL)


RF

B

reference beam

MISTRAL: Mass measurements at ISOLDE with a Transmission RAdiofrequency spectrometer on-Line

ion counter ISOLDE60 kV beam

RF

1 m

magnet

slit 0.4 mm

Resolving Power R= 100000Sensitivity: 500/sFAST: very short T1/2

fc fc

frequency (kHz)

505000 505100 505200

tran

smit

ted

ion

sign

al (

coun

ts)

f = (n + ½) fc

D. Lunney/Orsay D. Lunney/Orsay


Mass measurements of halo nuclei - 11Li

Graphics: I. Tanihata

100

150

200

250

300

350

400

450 MISTRAL2003

(preliminary)

AME95

Young93(reaction)

Wouters88(TOFI)

Kobayashi91(reaction)

Thibault75(mass spec.)

11Li

S2n

(ke

V)

MISTRAL:S2n=376(5) keV 20% higher than currently used to adjust models...

C. Bachelet, Ph.D. thesis (2004), EPJ A direct DOI: 10.1140/epjad/i2005-06-005-5

MIS RAL


New Paul-trapBeam cooler

Test run (Sept. 2005) :new mass for 12Be (T1/2 = 21 ms)

Test run (Sept. 2005) :new mass for 12Be (T1/2 = 21 ms)

11Be, 12Be, towards 14Be

MIS RAL


How magic are magic numbers?

H. Savajols et al., Eur. Phys. J. A direct (2005)

DOI: 10.1140/epjad/i2005-06-189-6

Island of Inversion

SPEG/GANILSPEG/GANIL

MISTRAL: n-rich Na and Mg isotopes with high precision


ISOLTRAP – triple trap spectrometer

G. Bollen et al., NIM A 368 (1996) 675H. Raimbault-Hartmann, NIM B 126 (1997) 378F. Herfurth et al., NIM A 469 (2001) 254

accumulation & bunching of ISOLDE

60 keV beam

coolingisobar separation

Rm

m

1 105

determination of cyclotron frequency

Rm

m

5 106

1m

B unc hes,3 keV ene rgy

60keV ISOLDE-

ion beam

1 cm

5 c

m

6 0 0 0 0 V

B = 4.7 T

B = 6 T

Linear RFQ trap

Mass measurement via determination of cyclotron frequency

c = (q/m)B

PRINCIPLE

0 1 2 3 4 5 6 7 8 9240

270

300

330

360

390

63Ga T1/2 = 32.4 s

Mea

n tim

e of

flig

ht /

s

Excitation frequency RF

- 1445125 / Hz

A. Herlert, K. Blaum A. Herlert, K. Blaum


32Ar32Ar

17Ne17Ne

74Rb74Rb

72Kr72Kr

216Bi216Bi

147Cs147Cs

232Ra232Ra

In 2002-2004

131 masses measured ()

rel. accuracy m/m 1·10-7

mean improvement: factor 40

33,34Ar33,34Ar

70Cu70Cu

~1000 / s

Highlights 2003 / 2004

Nuclide Half-life Uncertainty Yield

17Ne

32Ar

72Kr

74Rb

109 ms

98 ms

17.2 s

65 ms

~300 eV

1.8 keV

8.0 keV

4.5 keV

~1000 / s

~100 / s

~500 / s

22Na 2.6 y 160 eV ~106 / s

22Mg22Mg

ISOLTRAP harvest


0 10 20 30 40 50 60-60

-40

-20

0

20

40

60

A

1

-1

0

0 10 20 30 40 50 60-60

-40

-20

0

20

40

60

A

1

-1

0

0 10 20 30 40 50 60-60

-40

-20

0

20

40

60 Ground state quartets Excited state quartets Ground state quintets

x10

d /

ke

V

A

d /

ke

V

A = 33, T = 3/2 quartet:

A = 32, T = 2 quintet:

d = -0.13(45) keV

d = -0.11(30) keV

33Ar m = 0.44 keV32Ar m = 1.8 keV

33Ar m = 0.44 keV32Ar m = 1.8 keV

32,33Ar - most stringent test of IMME M = a + bTz + cTz

2 (+ dTz3)?

K. Blaum et al., PRL 91, 260801 (2003)

-40 -30 -20 -10 0 10 20 3080

100

120

140

160

180

200

220 32Ar T1/2 = 98 ms Y=100/s

Me

an

TO

F

(s)

RF - 2842679 (Hz)

Search for Scalar Currents from -delayed p-decay of 32Ar

E. G. Adelberger, A. Garcia et al., PRL 83 (1999) 1299 and 3101

Motivated by: Limits for Scalar Currents from -delayed p-decay of 32Ar can now be put on purely experimental ground

a = 1.0050 ± 0.0052(stat) ± (syst)

Limits for Scalar Currents from -delayed p-decay of 32Ar can now be put on purely experimental ground

a = 1.0050 ± 0.0052(stat) ± (syst)

ISOLTRAPISOLTRAP


35 40 45 50

10

12

14

16

18

Mn

SeAs

GeGaZn

FeCo

CuNi

S2n

(M

eV

)

NIs N = 40 magic? More measurements are required!

Towards exotic doubly magic nuclei - 78Ni

Evolution of nuclear binding towards doubly-magic 78Ni is not known nuclear structure – r-process

ISOLTRAPISOLTRAP

C. Guenaut PhD 2005EPJA direct 2005

81Zn

BRAND NEWBRAND NEW

+ n-rich tin isotopes up to 135Sn


270

300

330

360

390

Mea

n T

OF

/

s

270

300

330

360

390

Mea

n T

OF

/

s

0 2 4 6 8 10 12

270

300

330

360

390

Mea

n T

OF

/

s

c - 1300610 / Hz

16%

4%

80%

Intensity ratio:

with cleaning of 6– state

Unambiguous state

assignment!

Unambiguous state

assignment!

(6–) state = gs

(3–) state = 1.is

1+ state = 2.is

101(3) keV101(3) keV

242(3) keV242(3) keV

Identification of triple isomerism in 70CuISOLTRAPISOLTRAP

J. Van Roosbroeck et al., PRL 92, 112501 (2004)

c=q/m·B

RILISRILIS


Mass measurement programs outside ISOLDE

TRAPS LEBIT NSCLat MSU

Fragmentation,

In-flight fission

Short-lived, non-ISOL elements

SHIPTRAP GSI Fusion-Evaporation Superheavies

p-rich

CPT ANL Fusion-Evaporation

Fission

p-rich and n-rich (selected regions)

JYFLTRAP JYFL IGISOL, Spallation, Fission

Non-ISOL elements

Storage Ring ESR GSI Fragmentation

In-flight fission

Schottky (large surveys T1/2>10s)TOF: short-lived

Spectrometer TOF

SPEG GANIL Fragmentation Short-lived, very exotic

Cyclotron TOF CSS2 GANIL Fragmentation Short-lived

+ reactions (unbound states, beyond the dripline) and decays

New projects: TITAN at ISAC (highly-charged ions), MAFFTRAP (n-rich)


SHIPTRAP – Towards SHE

precision measurements with heavy ions produced at SHIP/GSI

Fusion-evaporation reactionsFusion-evaporation reactions

M. Block/GSIM. Block/GSI

146Ho(#), 147Ho, 147Er(#), 148Er(#), 147Tb, 147,148Dy, 148Tm(#)

732216 732220 732224 732228 732232

120

122

124

126

128

130

me

an

TO

F /

us

excitation freq. / Hz

147Ho600ms exc. timeBRAND NEWBRAND NEW 147Ho


beam from A1900

9.4 T Penningtrap system

Low Energy Beam and Ion Trap Facility at NSCL/MSU

1 cm1 cm

~ 100 MeV/u~ 1 eV

Low-energyexperiments

1 cm

Gas stopping

LEBIT

Mass measurementsLaser spectroscopyPost Acceleration

Mass measurementsLaser spectroscopyPost Acceleration

Gas stopperBeam Buncher

Precision experiments at low-energies with rare isotopes from fast-beam fragmentation


Secondary Beam 38Ca (92 MeV/u)

Statistical uncertainty m 80 eV

Expected final uncertainty m < 300 eV

• First successful nuclear physics

experiment with a thermalized beam

from fast beam fragmentation.

• 38Ca is a 0+ 0+ beta emitter: new

candidate for CVC tests.

• First successful nuclear physics

experiment with a thermalized beam

from fast beam fragmentation.

• 38Ca is a 0+ 0+ beta emitter: new

candidate for CVC tests.

Precision Mass Measurement of Fast Beam Fragments

m(38Ca++)/m(H30+)

37Ca++

T1/2 = 181 ms

67As+

… and more to come&


Conclusions

Mass measurements are key to a better understanding of nuclear structure and important to other fields of research with radioactive isotopes

ISOLDE has a very strong mass measurement program- Experiments related to key topics: halos, evolution of shell structure, nuclear astrophysics, fundamental interaction tests- Two excellent experimental devices with significant development potential

Complementary programs exist worldwide– different techniques (PTMS, TOF, ESR) – different production methods

… still a lot to be done!


Mass Measurements at RIA

Known masses

PTMS m < 50 keV

TOFMS m > 300 keV

RIA-TRAPwith 21 TeslaRIA-TRAPwith 21 Tesla


Masses close to Z=82

Discussion within IBM & microscopic-macrosopic modelR. Fossion et al., NPA 697 (2002) 703

S. Schwarz et al., NPA 693 (2001) 533

ISOLTRAPISOLTRAP

Region of shape-coexistence with

interesting nuclear structure effects

mass measurements and nuclear structure

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