B-1 Fragmentation – 0Introduction

• Generalities

• Isotopic distributions

• Neck emission

• Participant-spectator model

• Fragment separators

• LISE of GANIL

• FRS of GSI

• Fragment selection

• Fragment production

• Spin orientation

• Determination of polarization

• Influences on polarization

• Kinematical model

• Polarization vs target size

• Polarization vs Einc

B-1 Fragmentation – 1Generalities

projectile

target

abraded nucleons

evaporated nucleons

pre-fragment

fragment

Definition: Formation of a unique fragment from the peripheral collision of a projectile nucleus with a target nucleus. The impact results in the abrasion of few nucleons. The excited pre-fragment decays by emitting few other nucleons.

B-1 Fragmentation – 2Isotopic productions

32S 33S 34S 35S 36S

31P 32P 33P 34P 35P

30Si 31Si 32Si 33Si 34Si

29Al 30Al 31Al 32Al 33Al

28Mg 29Mg 30Mg 31Mg 32Mg

27Na 28Na 29Na 30Na 31Na

26Ne 27Ne 28Ne 29Ne 30Ne

25F 26F 27F 29F

37S

36P

35Si

34Al

33Mg

32Na

31Ne

31S

30P

29Si

28Al

27Mg

26Na

25Ne

24F

30S

29P

28Si

27Al

26Mg

25Na

24Ne

23F

29S

28P

27Si

26Al

25Mg

24Na

23Ne

22F

28S

27P

26Si

25Al

24Mg

23Na

22Ne

21F

24O 26O 28O23O22O21O20O

23N22N21N20N19N

193Pb 194Pb 195Pb 196Pb 197Pb 198Pb192Pb191Pb190Pb189Pb

192Tl 193Tl 194Tl 195Tl 196Tl 197Tl191Tl190Tl189Tl188Tl

191Hg 192Hg 193Hg 194Hg 195Hg 196Hg190Hg189Hg188Hg187Hg

190Au 191Au 192Au 193Au 194Au 195Au189Au188Au187Au186Au

189Pt 190Pt 191Pt 192Pt 193Pt 194Pt188Pt187Pt186Pt185Pt

188Pb

187Tl

186Hg

185Au

184Pt

188Ir 189Ir 190Ir 191Ir 192Ir 193Ir187Ir186Ir185Ir184Ir183Ir

187Pb

186Tl

185Hg

184Au

183Pt

182Ir

186Pb

185Tl

184Hg

183Au

182Pt

181Ir

187Os 188Os 189Os 190Os 191Os 192Os186Os185Os184Os183Os182Os181Os180Os

185Pb

184Tl

183Hg

182Au

181Pt

180Ir

179Os

186Re 187Re 188Re 189Re 190Re 191Re185Re184Re183Re182Re181Re180Re179Re178Re

184Pb

183Tl

182Hg

181Au

180Pt

179Ir

178Os

177Re

185W 186W 187W 188W 189W 190W184W183W182W181W180W179W178W177W176W

183Pb

182Tl

181Hg

180Au

179Pt

178Ir

177Os

176Re

175W

182Pb

181Tl

180Hg

179Au

178Pt

177Ir

176Os

175Re

174W

184Ta 185Ta 186Ta 187Ta 188Ta183Ta182Ta181Ta180Ta179Ta178Ta177Ta176Ta175Ta174Ta173Ta

181Pb

180Tl

179Hg

178Au

177Pt

176Ir

175Os

174Re

173W

180Pb

179Tl

178Hg

177Au

176Pt

175Ir

174Os

173Re

172W

172Ta171Ta

183Hf 184Hf 185Hf 186Hf182Hf181Hf180Hf179Hf178Hf177Hf176Hf175Hf174Hf173Hf172Hf171Hf170Hf

179Pb

178Tl

177Hg

176Au

175Pt

174Ir

173Os

172Re

171W

170Ta

169Hf

182Lu 183Lu 184Lu181Lu180Lu179Lu178Lu177Lu176Lu175Lu174Lu173Lu172Lu171Lu170Lu169Lu168Lu

178Pb

177Tl

176Hg

176Au

174Pt

173Ir

172Os

171Re

170W

169Ta

168Hf

176Tl

175Hg

174Au

173Pt

172Ir

171Os

170Re

169W

168Ta

167Hf

167Lu166Lu

181Yb180Yb179Yb178Yb177Yb176Yb175Yb174Yb173Yb172Yb171Yb170Yb169Yb168Yb167Yb166Yb165Yb

174Hg

173Au

172Pt

171Ir

170Os

169Re

168W

167Ta

166Hf

165Lu

164Yb

172Au

171Pt

172Ir

169Os

168Re

167W

166Ta

165Hf

164Lu

163Yb

179Tm178Tm177Tm176Tm175Tm174Tm173Tm172Tm171Tm170Tm169Tm168Tm167Tm166Tm165Tm164Tm163Tm162Tm

171Au

170Pt

171Ir

168Os

167Re

166W

165Ta

164Hf

163Lu

162Yb

161Tm

177Er176Er175Er174Er173Er172Er171Er170Er169Er168Er167Er166Er165Er164Er163Er162Er161Er160Er

175Ho174Ho173Ho172Ho171Ho170Ho169Ho168Ho167Ho166Ho165Ho164Ho163Ho162Ho161Ho160Ho159Ho

173Dy172Dy171Dy170Dy169Dy168Dy167Dy166Dy165Dy164Dy163Dy162Dy161Dy160Dy159Dy158Dy

171Tb170Tb169Tb168Tb167Tb166Tb165Tb164Tb163Tb162Tb161Tb160Tb159Tb158Tb157Tb

36S+9Be at 77.5 AMeV

simulations for the LISE

spectrometer

208Pb+9Be at 1 AGeV

simulations for the FRS

spectrometer

B-1 Fragmentation – 3Neck emission

projectile

target quasi-target

quasi-projectile

In peripheral collisions, at intermediate energies (Einc < 100 AMeV)

The neck emission favours the n-rich LCP’s.

LCP: Light Charged Particle = p, d, t, 3He, 4HeIMF: Intermediate Mass Fragment = 3 Z 30

enhancement of the emission of LCP’s and IMF’s from the intermediate velocity region

B-1 Fragmentation – 4Neck emission

CHIMERA predictions for Au+Au at 80 AMeV

J. Lukasik et al., Proceedings of INPC 2001

The rapidity of a particle corresponds to its velocity for non-relativistic energies

//

//

1ln

2

E py

E p

J. Lukasik et al., Phys. Lett. B 566 (2003) 76

Au+Au at 40, 60, 80, 100, 150 AMeVvery peripheral collisions

target projectile

B-1 Fragmentation – 5Participant - spectator model

projectile

target quasi-target(spectator)

quasi-projectile(spectator)

In peripheral collisions, at relativistic energies (Einc > 100 AMeV)

participant region

The participant region, very hot and dense, decays emitting only LCP’s, mainly nucleons.

B-1 Fragmentation – 6Fragment separators

Fragmentation production of exotic nuclei

LISE

FRSGANIL

Caen, France

GSIDarmstadt, Germany

B-1 Fragmentation – 7LISE of GANIL

LISE = Ligne d’Ions Super Epluchés (Super Stripped Ion Line)

secondary beam

dipole 1

dipole 2wedge

Wien filter

The primary beam (12C to 238U) have been accelerated in the two cyclotrons to energies from 5 to 95 AMeV

target

http://www.ganil.fr/lise/lise.html

B-1 Fragmentation – 8FRS of GSI

http://www-w2k.gsi.de/frs/index.asp

FRS = FRagment Separator

The primary beam (12C to 238U) have been accelerated in the synchrotron SIS to energies from 30 AMeV to 2 AGeV

B-1 Fragmentation – 9Fragment selection

Magnetic selection in mass, atomic number, and speed (A.v/Q).

The dipoles allow a deviation of the ions of the secondary beam according to their charge state, their speed, and mass. The determination of their magnetic rigidity B is a measure of this deviation.

Non-relativistic formula: Relativistic formula:

with

with B: magnetic rigidity (Tm) c: speed of light B: intensity of the magnetic field (T) A: nucleus mass (J) : curvature radius (m) Q: positive ion charge v: speed of the nucleus (ms-1) (Q Z, if fully stripped)

Magnetic dipoles

B-1 Fragmentation – 10Fragment selection

Selection in energy loss, on the atomic mass and number (i.e. in A3/Z2).

The degrader is located in an intermediate focal plane of the beam line. The secondary beam, still composed of several ions of diverse charge states, is slowed down and purified.

The energy loss in the material is characteristic of the beam particles (selection in v and Z).

The relative energy loss in the degrader is given by:

with K: constant typical of the degrader A: nucleus mass e: thickness of the degrader Z: atomic number

Degrader (wedge)

Selection in speed (v).

The electrostatic tank of the filter is divided in 2 subsections which are , each of them, inside a large magnetic dipolar gap. The beam goes then through a region with cross electric and magnetic fields (the direction of the electric field is vertical and the magnetic field’s is horizontal) with intensities such that the selected nucleus can continue its trajectory without being slowed down neither deviated of the incident direction of the secondary beam (the forces due to the two fields compensate each other). The other ions are deviated.

Wien filter

B-1 Fragmentation – 11Fragment production

LISE

Beam purity: 93%

FRS

at the end of the beam line

intermediate

focus

final focus

M.Pfützner et al., Phys. Rev. C 65(2002)064604

31Al

177Ta

B-1 Fragmentation – 12Spin orientation

q

yieldtarget

selected fragments in-flight separation

31

-1-3

Principle: transfer of momentum via nucleon removal in the projectile

symmetric selection (~ 0°): alignment

asymmetric selection (~ 2°): polarization

rather low orientation (5-30%)

In the early 90’s, it was discovered the possibility to create spin orientation in exotic nuclei via projectile fragmentation.

the participant spectator model: peripheral collisions

projectile

fragment or “spectator”

abraded part or “participant”

pproj

pfrag

pnucl

target

B-1 Fragmentation – 13Spin orientation

Po

pu

lati

on

-2 -1 0 1 2 m -2 -1 0 1 2 m -2 -1 0 1 2 m

ZOR ZORZOR

isotropic aligned polarized

p(m) equal m p(m) = p(-m) p(m) p(-m)

The direction in which the radiation is emitted by a radioactive nucleus, depends on the direction of its nuclear spin.This is formally described by the ‘angular distribution’ function:

W(, ,t) = Ak Bkn(t) Yk

n(,)

xy

z

or

I

k,n

4

2k+1

radiation parameter

orientation tensor

spherical tensors

An isotropic ensemble has B0 = 1, all other components are zero.

An aligned ensemble has Bk0 components for k=even, n0 components and odd

tensors are zero. radiation

A polarized ensemble has Bk0 components for k=odd, k=even and n0 components

are zero. radiation

for study of isomers: aligned beamfor study of ground states: polarized beam

B-1 Fragmentation – 14Spin orientation

32Al 33Al

asymm

etry The amount of polarization is determined from the asymmetry of the emissions:

radiation parameter experimental loss

Nup/Ndown = (3I/I+1) v/c A1Q1P

-NMR measurement Bhigh/B0 measurement

Experiment E347 of July 2003P. Himpe, private communication

asymm

etry

31Al

B-1 Fragmentation – 15Determination of the polarization

G.Neyens, Rep. Prog. Phys. 66 (2003) 633

Al isotopes

36S + 9Be at 77.5 AMeV

• the structure of the studied fragment? 32Al ground-state: 1+ 31,33Al ground-states: 5/2+

Influence of • the crystal host

B-1 Fragmentation – 16Influences on polarization

Experiment E347 of July 2003P. Himpe, private communication

(pf-p0)/p0

(pf-p0)/p0

0

po

lari

zati

on +

-

yiel

dK. Asahi et al., Phys. Lett. B 251(1990)488, H. Okuno et al., Phys. Lett. B 335(1994)29

rot

light target

rot

heavy target

(pf-p0)/p0

alig

nm

ent

+

-

R

k

Rk

Polarization

P = Jz / |J|

Alignment

A = ( 2Jy2 - J2 ) / J2

with the angular momentum

J = R x k

B-1 Fragmentation – 17Kinematical model

Coulomb repulsion > nuclear attraction far-side trajectory

Nuclear attraction > Coulomb repulsion near-side trajectory

H. Okuno et al., Phys. Lett. B 335(1994)29

rot = -50ºf = 0.05

rot = 60ºf = 0.1

rot = 150ºf = 0.1

15N+27Al15N+93Nb15N+197Au

Polarization of 12,13B from the reaction at 68 AMeV of…

data

model

scaling factor

B-1 Fragmentation – 18Polarization vs target size

rot = 10ºf = 0.15

rot = 10ºf = 0.07

rot = 10ºf = 0.025

100 AMeV 230 AMeV 400 AMeV

Polarization of 12B from the reaction 13C+9Be at…

K.Matsuta et al., Hyp. Int. 120/121(1999)713

data

model

Increase of the incident energy decrease of the amount of polarization (and increase of the amount of alignment)

B-1 Fragmentation – 19Polarization vs Einc