Physics and Applications with Exotic Nuclei

A. Galindo-UribarriSenior Scientist, Oak Ridge National Laboratory

and

Adjunct Professor, University of Tennessee

UTK Phys. 599 Fall 2009

Scientists are people of very dissimilar temperaments doing

different things in very different ways.

Among scientists are collectors, classifiers and compulsive

tidiers-up; many are detectives by temperament and many are

explorers; some are artists and others artisans. There are poet-

scientist and philosopher-scientists and even a few mystics.

Common sense and an enquiring mind are essential to the

makeup of a scientist.

Peter B. Medawar

Nobel Laureate (Medicine)

Advice to a Young Scientist

n

a

p

Heavy Ions

g

e-

Selective and complementary ways to investigate the internal structure of the nucleus

p

t

neutrinos

RHIC

CEBAFFRIB

nucleonQCD

few-body systemsfree NN force

many-body systemseffective NN force

fewnucleons

heavynuclei

quarksgluons

quark-gluonplasmaQCD

DUSEL

n

e

Cu, Au

Pb

100’s

RIB

Excitation

energy

IsospinSpin

We learn of Nuclear Matter by Pushing the Limits

N/Z

High SpinsExample A~150 region

A few nucleons make enormous difference !!!

Future g-ray spectrometers

tracking

digital signalprocessing

Installation sites

July 2, 2009 EMFNVI 10

ANL FMA

NSCL S800

ORNL RMS

2012 – 2013

6 months at each site

2 months for moving

Increased stability : number of isotopes, mass,binding energy, one-neutron or two-neutronsseparation energy

Quadrupole Moments close to zeroindicating spherical charge density

Importance of Magicand Double-Magic Nuclei

208Pb

132Sn56Ni

48Ca

16O

4He

100Sn

40Ca

Relatively higher excitation energy of its first excited state

Small B(E2) value (measure collectivity)

78Ni

RIB production techniquesThick

target

Ion

Source

Electromagnetic

separatorPostaccelerator

Primary

beam

Secondary

beam

ISOL (Isotope Separation On-Line)

Thin

target

Electromagnetic

separator

Primary

beam

Secondary

beam

IF (In-flight fragment separator)

high beam intensity & quality

slow (diffusion and effusion)

lower beam intensity

worse beam quality

fast

Difficulties:

RIBs have low intensities (typically 4 to 7 orders of magnitude less than SIBs)

High b & g background due to the decay of RIBs

Isobaric beam contamination

How to cope with these problems?

Low intensity: Maximize detection efficiencies of all subsystems

High background: Require coincidences between two or more detectors.

g rays, charged particles, beam particles, recoils, recoil decays

Isobaric contamination: “Ion Sourcery,” identify Z

Charged particles, x-ray, Bragg detector, ionization chamber

What is required?

Develop detection systems that are:specialized, efficient, selective, and flexible.

Experimental Challenges With ISOL beams

Instrumentation and Techniques

We have developed at HRIBF many techniques

and detectors for in-beam gamma spectroscopy

and decay studies with RIBs.

Most of these detectors can be used individually

or in combination (e.g. to enhance the

performance of CLARION). Generally these

detector systems have very large efficiencies.

Charged-particle arrays (CsI(Tl), DSSD’s, etc.)

Timing, beam monitors, diagnostics (MCPs,

Braggs, X-rays)

Neutron detector array

BaF2 Array, Spin Spectrometer, Plunger

Large acceptance spectrometer (RMS)

July 2, 2009

EMFNVI

14

12C

78Ge

Inverse kinematics with RIBs

Detected by a g –ray spectrometer

gMonitored using isobar

separation techniques

Detected by charged particle detector

Nuclear Structure in n-rich A=80 nuclei Medium mass nuclei are complex systems where collective and single particle effectsstrongly compete.

62 6458 556 38 40 42 44 46 48 50 552 54 60 66 68 70 72 74 76 78 80 82 84

Ni

Ge

SeBr

Zr

Mo

T= 1.5 GK, N = 10 cm

T= 1.0 GK, N = 10 cmn

n

24 -3

28 -3

Neutron number

Pro

ton n

um

be

r

SM Calculations by B. A. Brown

HRIBF - Measurement of B(E2) values at the N=50 shell closure

E. Padilla-Rodal

Padilla-Rodal, PRL 94(2005) r-process path

We are interested in the characterization of the N=50 shell gap and the evolution of single-particle levels with large neutron excess.

Understanding the role of intruder levels is determinant to reach a good descriptionExperimental evidence support the coexistence of different shapes in a single nucleus

Safe CoulEx: a clean tool

Pinning down relevant interactions in the Shell Model description

Coulomb ExcitationSafe EnergiesFast beam energies

Few nucleon transfer reactions(p, t) , (t, p), and polarized probes(d, p), (p, d), and polarized probes

Deep inelastic reactions (multinucleon transfer)

Ge80129.5 s

b- 2.37,…g 265.3,…

E 2.67

Ge781.47 h

b- .70,…g 277,…

E .95

Ge824.6 s

b- 3.6,…g 1091.9,…

E 4.7

Te13442 m

b- .6, .7, …g 767.2, 210.5,

277.9, 79.5,…

E 1.51

Te13617.5 s

b- 2.5, …g 2078.0, 334.0,

578.8, …(n) .429, …

E 5.1E .517

Te1323.20 d

b- .239, …g 228.3, 49.7, …

Sn13239.7 m

b- 1.76g 85.6, 340.5,

246.9, 890.0992.7

E 3.11

Sn1286.5 s 59.1 m

IT 91.1 b- .63, …

e-

g 831.5, g 482.2,1168.8 75.1, …

E 1.27

(7-) Sn1301.7 m 3.72 m

b- 3.2, b- 1.1, …3.0,… g 192.5,

g 144.9, 779.8,… 69.7, …

E 2.15

(7-) Sn1341.04 m

b- 2.5, …g 2078.0, 334.0,

578.8, …(n) .429, …

E 1.51

Ge831.9 s

b-

g 306.5,…

E 4.7

(5/+) Ge840.96 s

b-

g 242.4, 100.9(n)

E 7.7

Ge850.54 s

b-

(n)

E 10.

Ge86

E 9

Cu770.47 s

b-

E 10.

Cu780.34 s

b-

E 13

Cu790.19 s

b-

(n)

E 12

Pioneering Studies on Nuclear Spectroscopy of neutron-rich nuclei

- B(E2) for RIBs and SIBs along isotopic chains.

- A novel method for measure masses

- Quadrupole moments

- g factors

- Transfer reactions

79 SIBs

175 RIBs

7 x 104 pps of “pure” 132Sn

107pps on

target

Resonant Reactions: Thick Target Technique

A. Galindo-Uribarri et al.

NIM B172(2000)647

•Method: Thick target, DSSD arrays, timing,

good quality pure beams, inverse kinematics

50

150

250

350

450

550

650

d /d

(m

b/sr)

E (17O)=33 MeV

50

150

250

350

450

550

d /d

(m

b/sr)

E (17O)=20 MeV

50

150

250

350

450

550

d /d

(m

b/sr)

E (17O)=14 MeV

cm = 178o

cm = 178o

cm = 178o

50

150

250

350

450

550

650

d /d

(m

b/sr)

Sens et al

cm = 162o

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

cm ( MeV)

14 MeV

20 MeV

33 MeV

> 200 E’s

Excitation Functions 17O + p

17F, 18F, 11C

Good quality excitation functions obtained

at SINGLE bombarding energies

LAYMAN ARTICLESBY OTHERS:

New Scientist. - Short articleon the News section of theNovember 4 2000.

Science News Vol 158, p. 261October 21, 2000 by P. Weiss

AIP Bulletin of Physics News- Number 518, December 28,2000 by Phillip F. Schrewe.Ben Stein, and James Riordan

Physics World, Jan 2001article by Bertram Blank

Science, Feb 2001 article byPhil Woods

Physics Today, Sept 2002article by Barbara Goss Levi

2p decay from excited state in 18Ne

PAPERS

Phys. Rev. Lett. 86(2001)43 Decay of a

Resonance in 18Ne by the Simultaneous

Emission of Two Protons, J. Gomez del

Campo, et al.

Nucl. Phys. A682 (2001)363c Study of

resonant reactions with radioactive ion

beams and observation of simultaneous

2p emission, A. Galindo-Uribarri, et al.

Nucl. Instrum. And Methods Phys.

Res., Sect. B 172(2000)647 Study of

resonant reactions with radioactive ion

beams, A. Galindo-Uribarri, et al.

Simplified level schemes to

illustrate how the decay proceeds

2p

Polarization in Nuclear Physics

EMFNVI

“The production of a beam of

polarized elementary particles

might provide a useful tool for

the study of the spin-dependent

interactions of these particles.” Lincoln Wolfenstein

jijiijjiji

ij

r

ijij

ji

ij

r

NNOPE

ij rrr

e

rrr

emfv

ijij

ˆˆ333

134

2

2

A polarized target for RIB

As we increase our knowledge of nuclear properties to extreme values of Z/N,

new observables, more sophisticated experiments, and more efficient

techniques are required.

Projects: Enhanced Capabilities vs. New Vistas.

Over the last few years we have been working towards establishing proof-of-

principle for the development of a polarized target to be used in reactions with

RIBs.

With such a tool, we intend to pioneer the study of spin dependent

observables in nuclei far from stability. We propose a stepwise approach

towards establishing a research program on reaction spectroscopy using a

polarized target.

Recently we have assembled a group of scientists with a common and

complementary interest in the field of polarization from about 10 institutions

that include national labs and universities from USA/FRANCE/MEXICO AND

SWITZERLAND

Resonance parameters for the Ecm=1.56 MeV state

Analysis of d/d

and Ay

Skill et al. (1995)

Analysis of

d/d only

McCray (1963)

ER [MeV] 1.56±0.1 1.57

G [MeV] 0.4 ±0.05 0.84

Gp [MeV] 0.19±0.05 0.8

Elastic resonance scatteringStudy of isolated resonances of interest in astrophysics

M. Skill et al.

NPA 581(1995)93

Excitation functions and angular

distributions of cross sections and

analyzing powers are required in

order to unambiguously extract

resonance parameters.

1E-3

0.01

0.1

-0.4

0.0

0.4

0.8

1E-4

1E-3

0.01

0.1

-0.4

0.0

0.4

0.8

0 60 120 1801E-5

1E-4

1E-3

0.01

0 60 120 180

-0.4

0.0

0.4

0.8

Ex=0.16MeV

I=3/2

+

I=5/2

+

Exp. 6MeV/A

Ex=1.02MeV

(

fm2/s

r)

iT11

118Sn(d,t)

117Sn

Ex=1.18MeV

CM

(deg)

CM

(deg)

LippLi66

,

SntdSn117118

,

Transfer reactions

• Spectroscopic tool for the j-assignment of

SP states.

• Information on the spin-orbit interaction.

• Sensitivity of the analyzing power

increases at low energies.

Some Applications of Polarized Probes

M. Skill et al.,

Nucl. Phys. A581(1995)930.4MeV<Ep<2.2MeV

S. E. Vigdor and W. Haeberli,

Nucl. Phys. A253 (1975) 55.

A UTK Graduate Student at Work

4 5 6 7 8 9 10 11

0

100

200

300

400

500

4 5 6 7 8 9 10 11

0

100

200

300

400

500

Yie

ld

Ep [MeV]

Right Detector

Yie

ld

Ep [MeV]

Spin Down

Spin Up

Left Detector

The Polarized Targets• Dynamic Nuclear Polarization Technique

• Pp ~30%

• Thickness ~0.1-20mg/cm2 Polystyrene

• T=225mK, B=2.5T

• P relaxation times: ~10h at 225mK and B=0.8T (off-line)

Target is contained in

a superfluid helium

leak tight cell with

500nm thick Si3N4

windows. Polarization

is sampled in real time

with an NMR coil

attached to the target.

0 6 12 18 24 30 36 42

-25

-20

-15

-10

-5

0

5

10

15

20

25

Pola

riza

tio

n [%

]

Time [h]

Beam Off

Beam On

p Target Polarization History

References

J. P. Urrego-Blanco,

PhD Thesis, University of Tennesse.

J. P. Urrego-Blanco et al.,

NIM B261 (2007) 1112.

A. Galindo-Uribarri and J. P. Urrego,

Rev. Mex. Fís. S53 (2007) 35

Proof of Principle @PSI

38MeV @ ,1212

pCCp

effects of excess neutrons on spin-orbit potential?

proton elastic scatterings on helium isotopes

4He 6He 8He

N/Z=1 N/Z=2 N/Z=3

rm =1.49 fm rm=2.30 fm rm=2.45 fm

S2n=28.3 MeV S2n=1.86 MeV S2n=2.58 MeV

First experiments

Accelerators and AMS pioneers

HRIBF Upgrade

November 13, 2009

LBNL 60” cyclotron

Luis

Alvarez

Mueller

CHALK RIVER EN-1

ROCHESTER MP

MCMASTER FN

Litherland Gove

AMS (14C) Direct Atom Counting

•14C - 14N mass difference 1 in 105

•12CH2 - 14C mass difference 1 in 103

•14N does not form negative ions

Mass Spectrometry

AMS

AMS Ion Sources

Villahermosa 08

A typical AMS sputter source

consists of a heated Cs

reservoir, an ionizer producing a

focused Cs+ beam at the

sample, and an extraction

electrode to accelerate and

focus secondary negative ions

from the sample into the

injection beamline.

mg samples

Important issues

for AMS:

Memory effects

Multiple samples

High currents

Study of 12CH22+ and other doubly charged molecules

Nuclear Instruments and Methods in Physics Research B5 (1984) 208

Beams of doubly ionized molecules from a tandem

accelerator, A. Galindo-Uribarri et al. J. Chem. Phys.

83(1985)1

Beams ~ 4 MeV of small doubly charged molecules: 10B11B, 10B2,

11B12C, 9Be14N, 12C13C, 12C13CH, 12CN, 12C2H, 12CH2,

9Be16O,10B16O

Exponential destruction of molecules

in the gas stripper at the HV terminal

Atomic

AMS-3

14C+2

ORNL HRIBF 25-MV Tandem

HRIBF Upgrade

November 13, 2009

Highest operating voltage

in the world

ETH 0.25-MV Tandem

14C+1

14C+6

AMS and Radioactive Ion Beams (RIB)

Common problems/needs:

Good detection tools:

Most interesting RIBs are short-lived17F (t1/2 = 65 s)

methodology; pilot experiments; proof-of-principle tests; detection systems; ion optics

In AMS: long-lived species36Cl (t1/2 = 3.01 x 106 a)

We have concentrated in:

•Production

•Isobar removal

•Stable machine operation

•Low intensity beam diagnostics

•Bragg Detector

•Projectile X-ray

•TOF

•Gas filled magnet

•Beam monitors

Research-operations tied

RIBs

1) Intrinsic magnetic

analyzer (180 deg. magnet)

2) Early molecular

destruction followed

by reacceleration

3) Source and

detection system at

ground potential

AMS10

Pushing the Limits of

AMS - Measurement

of 36Cl in seawater

samples

AMS 9

Opportunistic mass

measurements at the

HRIBF 77–79Cu and 83–86Ge

AMS Setup at HRIBF

Pushing the AMS sensitivity for 36Cl by an order of magnitude

Seawater samples

Reference

Blank

36Cl Bragg detector spectra

Importance of

extra sensitivity:

A. G-U et al. NIM B 259(2007) 123

•Oceanographic tracer

•Waste Disposal

•Nuclear Safeguards

•Rock Erosion

36Cl/Cl = 3 x10-16 !!

Villahermosa 08

http://meetings.aps.org/link/BAPS.2007.DNP.BC.8

Photodetachment Cl-S for AMS - Suppresion ~ 104

Tom Lewis (Science Alliance UTK) and Yuan Liu (ORNL)

Faraday

Cup

Laser

Laser Power Meter

Ion

Beam

Experimental Setup - Photodetachment

Suitability of an isotopic pair to be utilized as a forensic indicator

Tritium beams and targets at HRIBF

Implementing a tritium-beam capability at ORNL

Considerable interest in the fusion, reactions and

structure community in tritium beams, as well as tritium

target.•Reactions with long lived radioactive targets

•Development of tritium targets

•t - scattering experiments

•( t,3He ) Charge Exchange

•( t, pg ) as a surrogate reaction for ( n, g )

•t ( t, 2n )4He reaction studies for the NIF

•Transfer reactions ( t , p) compared with ( p, t )

•t + dpol

Discrepancy needs to be resolved: results from an old t(t,n)na

experiment, which seem to fit well with theory analysis do not agree

with observations of recent t+t fusion experiments at Omega

(Rochester) Solution: perform a t+t experiment with tritium

beam and tritiated target.

Crystal-blocking lifetime studies of heavy-ion induced fission at HRIBF

The measured lifetimes of 1-2 attoseconds are

surprisingly long and are inconsistent with the

Bohr-Wheeler model. They support a picture of

strongly damped quasi-fission: the nucleus

behaves like a drop of syrup

Get involved in cutting-edge research in:

Nuclear Structure of very neutron

rich nuclei through the measurement

of: transition probabilities,

deformation, gyromagnetic ratios,

etc.

Reaction mechanisms using exotic

probes.

Opportunities

Hands on experience using multi-detector arrays

Development of new instrumentation

Interdisciplinary research

Participate in international collaborations: e.g.

Paul Scherrer Institute (Switzerland), GANIL

(France)

Strong research group at HRIBF