Mass Mass measurements on measurements on

neutron-rich nuclei neutron-rich nuclei with the CPT mass with the CPT mass

spectrometer @ spectrometer @ CARIBUCARIBUKumar S. SharmaKumar S. Sharma

Department of Physics and Department of Physics and AstronomyAstronomy

Winnipeg MBWinnipeg MB

OutlineOutline

IntroductionIntroduction Past work with the CPT at ANLPast work with the CPT at ANL CARIBU – opportunities for the CPTCARIBU – opportunities for the CPT Current status of the apparatusCurrent status of the apparatus ConclusionConclusion

Synthesis of the Synthesis of the elementselements

from : http://www.jinaweb.org/html/pprocess.html

The r-process plays an The r-process plays an important role in the important role in the synthesis of the heavier synthesis of the heavier elementselements

Possible sites for the Possible sites for the r-processr-process

Why these sources:Why these sources: high density of neutronshigh density of neutrons high temperature high temperature

environmentsenvironments

Supernovae??? Merging neutron stars???

r-process basicsr-process basics

Nuclear reactions compete until a balance is reached

Abundance maxima along each chain occurs with the neutron separation energy, Sn ~ 3 MeV

N

Z

(n,γ)

(γ,n)

β-

Seed Waiting-point

…

The Saha EquationThe Saha Equation

The relative abundances of the elements The relative abundances of the elements synthesized in the r-process are determined by synthesized in the r-process are determined by the Saha Equation:the Saha Equation:

determines the equilibrium between neutron capture determines the equilibrium between neutron capture and photodisintegration in a very hot environment.and photodisintegration in a very hot environment.

outcome is outcome is exponentiallyexponentially dependent on the neutron dependent on the neutron separation energy.separation energy.

Atomic masses of the nuclides along the reaction Atomic masses of the nuclides along the reaction paths are needed to determine the neutron separation paths are needed to determine the neutron separation energy: Senergy: Snn

3 32 2 2 , 1 , 1( , 1) 2 1

exp( , ) ,

nn

G Z A S Z AY Z A An

Y Z A kT A G Z A kT

Neutron separation Neutron separation energiesenergies

Single neutron separation energies:Single neutron separation energies:

SSnn values: [n – (M(Z,N) – M(Z, N-1))]c values: [n – (M(Z,N) – M(Z, N-1))]c22

Double neutron separation energiesDouble neutron separation energies

SS2n2n values: [2n – (M(Z,N) – M(Z, N-2))]c values: [2n – (M(Z,N) – M(Z, N-2))]c22

Converted to appropriate energy units

Fission Yields from a Fission Yields from a 252252Cf Cf sourcesource

1 Ci source strength

Previous configuration of Previous configuration of the CPTthe CPT

New CPT /

Previous CPT measurements

CPT Fission Fragment CPT Fission Fragment MeasurementsMeasurements

Ongoing program of measurements since March 2008, target 15 keV Ongoing program of measurements since March 2008, target 15 keV uncertaintyuncertainty

40 species, 5 have never been previously measured by any means, most 40 species, 5 have never been previously measured by any means, most others improved by a typical factor of 5others improved by a typical factor of 5

Adds to 30 measurements taken at CPT in past years with small gas catcherAdds to 30 measurements taken at CPT in past years with small gas catcher

Comparisons with the Comparisons with the AME03AME03

CPT

U. Hager et al., Phys. Rev. Lett. 96, 042504 (2006).

JYFLTRAP

-500-300-100100300500700900

110013001500

84 85 86 87 88 89 90 91 92 93 94Neutron Number

ME

(Exp

t.)-

AM

E20

03)

[keV

] AME2003

CPT La

-500-300-100100300500700900

110013001500

84 85 86 87 88 89 90 91 92 93 94Neutron Number

ME

(Ex

pt.

) -

(AM

E2

00

3)

[ke

V]

AME2003

CPT Ba

Deviations from 2003 atomic Deviations from 2003 atomic mass evaluation increase with mass evaluation increase with neutron numberneutron number

Trends suggest r-process path is Trends suggest r-process path is closer to stabilitycloser to stability

SS2n2n values: [2n – (M(Z,N) – M(Z, N- values: [2n – (M(Z,N) – M(Z, N-2))]c2))]c22

More recent work

New CPT /

Previous CPT measurements

Grander PlansGrander Plans

What’s moving?What’s moving? CPT TowerCPT Tower Associated electronics and vacuum controlAssociated electronics and vacuum control

Overview of CARIBUOverview of CARIBU

CPT at CARIBUCPT at CARIBU

CARIBU

CPT

Stable ion source

Buncher

Elevator

Low energy beamlineLow energy beamline

Requirements at CARIBURequirements at CARIBU Desired precision: ~ 10 – 100 keVDesired precision: ~ 10 – 100 keV Required yield: 3000-30000 ions for a Required yield: 3000-30000 ions for a

measurementmeasurement Considerations:Considerations:

‘ ‘Production’ yield (2-80 mCi)Production’ yield (2-80 mCi) Efficiency (~ 1%)Efficiency (~ 1%) Half-life ~ 1 secondHalf-life ~ 1 second

Plan for measurementsPlan for measurements

Jon’sDan’s

Vastly superior to 238U fission

Get online ASAPGet online ASAP Gas catcher/RFQ Gas catcher/RFQ

operationaloperational Buncher RFQ built Buncher RFQ built

and being and being commisionedcommisioned

CPT assembled and CPT assembled and operationaloperational

Low energy beam Low energy beam line installedline installed

Spend 6 to 18 months Spend 6 to 18 months measuring 100+ measuring 100+ masses to < 10masses to < 10-7-7

Goals include r-Goals include r-process and nuclear process and nuclear structure structure

ConclusionConclusion

Previous results among neutron-rich Previous results among neutron-rich nuclei approaching the r-process nuclei approaching the r-process pathpath

Some interesting systematic effects Some interesting systematic effects observedobserved

Higher yields of these nuclei at Higher yields of these nuclei at CARIBU will allow us to push even CARIBU will allow us to push even further away from stabilityfurther away from stability

The CPT CollaborationThe CPT Collaboration

A. Chaudhuri, G. Gwinner , K.S. Sharma

J.A. Clark, A.F. Levand, G. Savard, T. Sun,

F. Buchinger, J.E. Crawford, S. Gulick, G. Li

D. Lascar, R. Segel

S. Caldwell, M. Sternberg, J. Van Schelt

C.M. Deibel

Efficiencies at CARIBUEfficiencies at CARIBUEfficiency:

• Yield (2-80 mCi 252Cf; 3% fission branch)

• Enter gas catcher (~ 50%)

• Stopped in gas catcher (~ 80%)

• Extracted from gas catcher (~ 33%)

• RFQ (~ 80%)

• Transfer through mass separator (~90%)

• Buncher (~ 60%)

• Transfer to Penning trap (~ 33%)

• Detection (~ 50%)

Total: ~ 1% efficiency (excluding 3% fission branch)