direct reactions at eurisol

Direct Reactions at Eurisol

In the light of the TIARA+MUST2 campaign at

GANIL

B. Fernández-Domínguez

Physics Motivation

Direct reactions are a unique tool to uncover and investigate new manifestations of nuclear structure of exotic nuclei


-Inverse kinematics Detection:

- light charged particles - gamma-rays - neutrons - beam-like particles

Elastic and inelastic scattering -> nuclear and transition densities

Transfer, knock-out and break-up reactions -> microscopic shell-structure

EURISOL FW5 report : SCIENTIFIC CASE (Appendix A):

Array for light charged-particle and gamma-array

measurements: GRAPA (Gamma-Ray And Particle Array)

Instrumentation for Direct Reactions


• 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

EURISOL FW5 report : INSTRUMENTATION (Appendix E):

Updated version: http://ns.ph.liv.ac.uk/eurisol/spec_expts/M2.1_apparatus.pdf

Integration of cryogenic and polarised targets.

RIB

- 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.


Preliminary design work required

SIMULATIONS:

Key experiments:

• 78Ni(d,p)79Ni @ 10 MeV/u

• 132Sn(d,p)133Sn @ 10 MeV/u

133Sn

853.7 keV

1560.9 keV1655.7 keV

2004.6 keV

3700 keV

Preliminary design work required: SIMULATIONS

Target Thickness

Particle Array: (energy and angular resolution)

Gamma Array:

Interaction Point


Scintillating material : (CsI, LaBr3)

(d,p) with 20O and 26Ne beams at SPIRAL : Study of the N=16 shell gap


Large step towards an integrated particle-gamma ray array.

TIARA-MUST2 CAMPAIGN AT SPIRAL/GANILSeptember – November 2007

-Si-array ->Array of silicon detectors covering 90% of 4pi. MUST2 and TIARA

-Ge-array->EXOGAM

-Spectrometer ->VAMOS

Results can be used to validate the design choices of the new EURISOL array

Preliminary design work required: IN-BEAM TESTS

20O-> Location of the d3/2 state in Oxygen neutron rich isotopes

26Ne->Reveal isomeric f7/2 intruder that competes with sd ground state

Triple coincidences:Target-like particles – TIARA/MUST2Beam-like particles - VAMOSGammas - EXOGAMTrigger: hit in Si-detector


Preliminary design work required: IN-BEAM TESTS

TIARAsilicon array

VAMOSspectrometer

GANIL radioactive beam - 20O (SPIRAL) 10.9 A MeV

CD2 target0.5 mg/cm2Detectors

E, E, TOFB,

EXOGAMGamma-ray array

104 pps

MUST2Si-CsI

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)

MUST2: 4 Telescopes of Si+CsI


MUST2 4 telescopes of Si-CsI placed at forward angles. (0-30 deg)

Si-Strip – 4 modules x128x128Energy, position.E~ 50 keV, θ~0.22 deg (pitch size 0.7mm at 180 mm)

CsI- 4 modules with 4x4 crystalsIdentification E-E

TIARA+MUST2 coupled to VAMOS


•Identification of the recoil VAMOS:Ionisation Chamber->EPlastic ->E, TOF Drift Chambers ->X,Y,θ,

TIARA+MUST2 coupled to VAMOS +EXOGAM


•Gamma detection with EXOGAM4 Clovers @ 90 deg

15% photopeak efficiency @ 1.3 MeV

SPIRAL: RADIOACTIVE BEAM of 20O: d(20O,p)21O 21O +


Preliminary (on-line results)

BOUNDSTATES

(d,p)

E (

MeV

)

θ (degrees)

g.s

1st 1.28 MeV

SIMULATIONGeant4

θ (degrees)

E (

MeV

)

g.s


SPIRAL: RADIOACTIVE BEAM of 20O: d(20O,p)21O 20O + n

θ (degrees)

E (

MeV

)

UNBOUNDSTATES

(d,p)

SIMULATIONGeant4

E (

MeV

)

θ (degrees)

E (keV)

Preliminary (on-line results)

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

The feasibility of the methodology is demonstrated.

SUMMARY

• 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.

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

Distance to (0,0,0) = 5 cm

Box of 4 Silicon detectors :

Area =10*10 cm2

Detector Thickness =300um

Source of protons with kinematics from reaction placed at (0,0,0)

No target

X

Z

YINPUT:

Energy Resolution

Strip pitch size

Thickness detector (punch through)

Target thickness effect

STUDY of the θ and Ex

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

The main source comes from the uncertainty on the z-coordinate

Beam spot size negligeable

FWHM

203 keV

221 keV

280 keV

315 keV

418 keV

E (keV) FWHM

gs 174 keV

1560.9 181 keV

1561+1655

224 keV

2004.6 208 keV

3700 217 keV

133Sn

853.7 keV

1560.9 keV1655.7 keV

2004.6 keV

3700 keV

FWHM

362 keV

406.5 keV

778 keV

-----

945 keV

EXPERIMENTAL DATA: 132Sn(d,p)133Sn at Oak RidgeCourtesy K. JONES preliminary

Data will be an input for the event-generator ->Realistic implementation of the cross sections

160 um/cm2 target of CD2 at 4.7 MeV/u

GAMMA ARRAY: RESOLUTION: DOPPLER

BROADENING

Θlab(degrees)

E/

E

(%)

E lab = f(θ,) -> E/E dop ~ f(θ)

)cos1( labEE

E/E ~ 0.5 %

E=1MeV -> 5 keV

θ~ 2o

D=8 cm

Crystal Size θ

2.8 mm 2o

3mm for a detector size of 12cm ->40x40 =1600 ch detector

6 detectors ->6x 1600=9600 channels

GAMMA ARRAY: RESOLUTION: INTRINSIC

E/E int ~ Eγ)g(material

A

EγEo

εscintεph.

2.35

F. Notaristefani NIM A480 (2002) 423-430

Other materials:

LaBr3(Ce),LaCl2

To be studied

E/E int ~ 13.4 % at 662 keV ~ 90keV

• 23O from USD shell model and M.Stanoiu et al., PRC 69 (2004) 034312.• 25Ne preliminary result.

The energy of the 1d3/2 neutron orbital rises when protons are removed from its spin-orbit partner, the

1d5/2 orbital.

4.5

1.5

1.0

0.5

0.0

3.0

2.5

2.0

4.0

3.5

exci

tati

on e

nerg

y (M

eV)

6 8 10 12

atomic number

1d3/2

1d5/2

1f7/2

2s1/2

27Mg23O 25Ne+2.1 TRANSFER 24Ne(d,p)25Ne : Systematics of the 3/2+ in the N=15 isotones

direct reactions at eurisol

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