Transcript Document

Direct Reactions at Eurisol
In the light of the TIARA+MUST2
campaign at GANIL
B. Fernández-Domínguez
Physics Motivation
EURISOL FW5 report : SCIENTIFIC CASE (Appendix A):
Direct reactions are a unique tool to uncover and investigate new
manifestations of nuclear structure of exotic nuclei
 Elastic and inelastic scattering -> nuclear and transition densities
 Transfer, knock-out and break-up reactions -> microscopic shell-structure
-Inverse kinematics
Detection:
- light charged particles
- gamma-rays
- neutrons
- beam-like particles
B. Fernández-Domínguez
Instrumentation for Direct Reactions
EURISOL FW5 report : INSTRUMENTATION (Appendix E):
Array for light charged-particle and gamma-array measurements:
GRAPA (Gamma-Ray And Particle Array)
Updated version: http://ns.ph.liv.ac.uk/eurisol/spec_expts/M2.1_apparatus.pdf
• Charged Particles: (Particle Array )
Solid-angle of 4
x~0.1,0.5 mm and θ~ 1-5 mrad
Large dynamic range with PID to Z=10
• Gamma and fast charged particles : (Gamma Array)
Solid-angle of 4
Best efficiency and resolution
Integration of cryogenic and polarised targets.
B. Fernández-Domínguez
Preliminary design work required
- SIMULATIONS: Modelling of a number of potential key
experiments proposed, study different configurations etc…
- IN-BEAM TEST TO VALIDATE DESIGN CHOICES : To asses the
methodology and feasibility of the design concept.
SIMULATIONS:
3700 keV
Key experiments:
• 78Ni(d,p)79Ni @ 10 MeV/u
2004.6 keV
• 132Sn(d,p)133Sn @ 10 MeV/u
1655.7 keV
1560.9 keV
853.7 keV
133Sn
B. Fernández-Domínguez
Preliminary design work required: SIMULATIONS
Particle Array: (energy and angular resolution)
 Target Thickness
 Interaction Point
Gamma Array:
 Scintillating material : (CsI, LaBr3)
B. Fernández-Domínguez
Preliminary design work required: IN-BEAM TESTS
TIARA-MUST2 CAMPAIGN AT SPIRAL/GANIL
September – November 2007
-Si-array ->Array of silicon detectors
covering 90% of 4pi. MUST2 and TIARA
-Ge-array->EXOGAM
-Spectrometer ->VAMOS
Large step towards an integrated particle-gamma ray array.
Results can be used to validate the design choices of the new EURISOL array
(d,p) with 20O and 26Ne beams at SPIRAL : Study of the N=16 shell gap
20O->
Location of the d3/2 state in Oxygen neutron rich isotopes
26Ne->Reveal
isomeric f7/2 intruder that competes with sd ground state
B. Fernández-Domínguez
Preliminary design work required: IN-BEAM TESTS
EXOGAM
Gamma-ray array
VAMOS
spectrometer
MUST2
Si-CsI
GANIL radioactive beam
- 20O (SPIRAL) 10.9 A MeV
104 pps
TIARA
silicon array
Detectors
E, E, TOF
B, 
CD2 target
0.5 mg/cm2
Triple coincidences:
Target-like particles – TIARA/MUST2
Beam-like particles - VAMOS
Gammas - EXOGAM
Trigger: hit in Si-detector
B. Fernández-Domínguez
TIARA: Inner and Outer Barrel +Hyball
TIARA
– Two Barrels: 8 detectors, x 4
longitudinal strips each.
-Inner Barrel-> Energy, position.
(E~ 200 keV, θ~1-2 deg)
-Outer Barrel- identification.
(30-140 deg)
- Hyball, 6 wedges, x16 rings (radial),
x 8 sectors (azimutal)
(E~ 50 keV, θ~2 deg)
(150-175 deg)
B. Fernández-Domínguez
MUST2: 4 Telescopes of Si+CsI
MUST2
4 telescopes of Si-CsI placed
at forward angles. (0-30 deg)
Si-Strip – 4 modules x128x128
Energy, position.
E~ 50 keV, θ~0.22 deg (pitch
size 0.7mm at 180 mm)
CsI- 4 modules with 4x4
crystals
Identification E-E
B. Fernández-Domínguez
TIARA+MUST2 coupled to VAMOS
•Identification of the recoil
VAMOS:
Ionisation Chamber->E
Plastic ->E, TOF
Drift Chambers ->X,Y,θ,
B. Fernández-Domínguez
TIARA+MUST2 coupled to VAMOS
+EXOGAM
•Gamma detection with
EXOGAM
4 Clovers @ 90 deg
15% photopeak efficiency
@ 1.3 MeV
B. Fernández-Domínguez
SPIRAL: RADIOACTIVE BEAM of 20O: d(20O,p)21O  21O + 
Preliminary (on-line results)
E (MeV)
(d,p)
BOUND
STATES
g.s
1st 1.28 MeV
E (MeV)
θ (degrees)
SIMULATION
Geant4
g.s
θ (degrees)
B. Fernández-Domínguez
SPIRAL: RADIOACTIVE BEAM of 20O: d(20O,p)21O  20O + n
E (MeV)
Preliminary (on-line results)
(d,p)
UNBOUND
STATES
E (MeV)
θ (degrees)
E (keV)
SIMULATION
Geant4
θ (degrees)
B. Fernández-Domínguez
SUMMARY
 Simulations reproduce response of arrays and give insight into the main
parameters that contribute to performance
Online analysis of the experiment confirms we can study different reactions
channels, obtain level energies and l-values information
• transfer to bound and unbound states with full channel identification
• triple coincidences with excellent gamma energy resolution
• also have (d,d’) and (d,t) acquired simultaneously with TIARA and MUST2
• to include unbound states requires the large VAMOS angle/momentum bite
• type of experiments will be important to learn for the future array.
 The feasibility of the methodology is demonstrated.
FUTURE
 Increase efficiency of particle-gamma coincidences..
Gamma detection better efficiency, allow for fast-particle detection simultaneously
 Improve performance of particle array. (Energy resolution, low thresholds)
 Possibility to introduce cryogenic or polarised targets
No part of the talk
end
PARTICLE ARRAY: Simple Geometry
INPUT:
Y
 Distance to (0,0,0) = 5 cm
 Box of 4 Silicon detectors :
Z
 Area =10*10 cm2
 Detector Thickness =300um
 Source of protons with kinematics
from reaction placed at (0,0,0)
No target
X
 Energy Resolution
STUDY of the θ and Ex
Strip pitch size
Thickness detector (punch through)
Target thickness effect
PARTICLE ARRAY: INTERACTION POINT
 Assuming reaction can take place at any Z < Target
Thickness
 X and Y are defined by the beam spot size
1 mg/cm2
1 mg/cm2
+inter point
PARTICLE ARRAY: RANDOM INTERACTION POINT
3700 keV
2004.6 keV
1655.7 keV
1560.9 keV
853.7 keV
133Sn
E (keV)
FWHM
FWHM
FWHM
gs
174 keV
203 keV
362 keV
1560.9
181 keV
221 keV
406.5 keV
1561+1655
224 keV
280 keV
778 keV
2004.6
208 keV
315 keV
-----
3700
217 keV
418 keV
945 keV
The main source comes
from the uncertainty on
the z-coordinate
Beam spot size negligeable
EXPERIMENTAL DATA: 132Sn(d,p)133Sn at Oak Ridge
Courtesy K. JONES preliminary
160 um/cm2 target of CD2 at 4.7 MeV/u
Data will be an input for the event-generator ->Realistic implementation of the
cross sections
GAMMA ARRAY: RESOLUTION: DOPPLER BROADENING
E lab = f(θ,) -> E/E dop ~ f(θ)
E/E (%)
E  Elab (1   cos )
E/E ~ 0.5 %
E=1MeV -> 5 keV
θ~ 2o
D=8 cm
Crystal Size
θ
2.8 mm
2o
Θlab(degrees)
3mm for a detector size of 12cm ->40x40 =1600 ch detector
6 detectors ->6x 1600=9600 channels
GAMMA ARRAY: RESOLUTION: INTRINSIC
E/E int ~
2.35
A

εscint
g(material) Eγ
εph.
Eγ
 Eo 
E/E int ~ 13.4 % at
662 keV ~ 90keV
Other materials:
LaBr3(Ce),LaCl2
F. Notaristefani NIM A480 (2002) 423-430
To be studied
2.1 TRANSFER 24Ne(d,p)25Ne : Systematics of the 3/2+ in the N=15 isotones
+
23O
excitation energy (MeV)
4.5
25Ne
27Mg
4.0
1f7/2
3.5
• 23O from USD shell model
and M.Stanoiu et al., PRC
69 (2004) 034312.
• 25Ne preliminary result.
3.0
2.5
2.0
1.5
1d5/2
1.0
1d3/2
0.5
2s1/2
0.0
6
8
10
12
atomic number
The energy of the 1d3/2 neutron orbital rises when protons are
removed from its spin-orbit partner, the 1d5/2 orbital.