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