1. Design study for a Helios-like spectrometer at LNS
D. Santonocito – LNS User Meeting – 9/5/2017

2. Design study for a Helios-like spectrometer at LNS
Study of nuclear structure direct reactions
Elastic Scattering (sensitive to the density distribution of p,n)
Inelastic Scattering (collectivity, B(E2),B(E3))
Single nucleon transfer reactions (single particle states, astrophysical process)
Transfer of nucleons pair (pair correlations)
Inverse kinematics:
measurement of the light reaction partner
Typical experimental problems:
Low energy particles - identification
Strong angular dependence
Kinematical compression at large angles
Low intensity beams (detection efficiency)

3. Helical orbit Spectrometer (HELIOS- Argonne ) : how it works ?
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Helical orbit Spectrometer (HELIOS- Argonne ) : how it works ?
Target inside the solenoid along the magnetic axis
Light charged particles emitted from the target follow, in the magnetic field, helicoidal
trajectories and are focused back on the magnetic axis: Tcyc = 2m/Bqe z = vparTcyc
Detection through a position sensitive Si array.
What we need to measure:
Impact point z (Dx = 1 mm)
Elab
ToF (~ 1 ns)
In an homogeneous field ToF = Tcycl
Derived quantities:
Particle identification m/q
Ecm
Qcm 2
m/q = (eB/2p) Tflight
Ecm = Elab + 1/2mVcm –VcmeqBz/2p
Qcm = arccos(qeBz-2pmVcm/(2p√2mElab +m2Vcm –mVcmqeBz/p)
Schema HELIOS

4. Features of an helical orbit spectrometer
From (Elab- Qlab) to (Elab – z)
Particles identification
Tcycl = * A/qB (ns)
(con A in amu, B in Tesla)
B= 2 Tesla B = 3 Tesla
Protoni (ns) (ns)
d, Alfa (ns) (ns)
trizio (ns) (ns)
Dimensions of the Solenoid
Homogeneity of the field in the volume
Size and shape of the detection array

5. Solenoid main features
Parameters influencing the spectrometer acceptance :
Magnetic field intensity (up to 5 Tesla)
homogeneity (10-4)
Radius (R)
Lenght (L)
Homogeneous field in the solenoid tipically restricted to a region with L ≈ 2R
Max distance from the solenoid axis (cm) - protons
Zimp of protons on solenoid axis ( B= 2T )
Max distance from the
solenoid axis (cm)
Zimp of protons on solenoid
axis (cm)
Emission Angle (deg)
Emission angle (deg)
LNS Solenoid dimensions: Radius=30 cm – Lenght = 200 cm

6. Shape of SOLE solenoid magnetic field
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Shape of SOLE solenoid magnetic field
Sole in OPERA
Field shape B=3T
Z = 0 cross-section
Shape of the field B=3T
z (cm)
1 104
2 104
3 104
A. Calanna

7. Trajectories simulations in SOLE using OPERA
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Trajectories simulations in SOLE using OPERA
E= 2 MeV
E= 6 MeV
E= 2 MeV
A. Calanna

8. Detector Array Effects: simulations
HELIOS setup
Si 1000 mm – 20 x 50 mm
source posit.(0.5; 0; 0) cm
A. Calanna

9. Preliminary results on spectrometer performances: simulations
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Preliminary results on spectrometer performances: simulations
Protons:
E = 4 MeV, Q= 70°
E = 4 MeV, Q= 70.5°
Angolo ricostruito
vs dimensione del beam spot
A. Calanna

10. New Fragment separator
Degrader
Target where fragmentation occurs
2 - triplets
2 – doublets
2 - 70° dipoles
2 - 40° dipole
courtesy A. Russo

11. Repositioning of SOLE solenoid in the CICLOPE area
To build this line it is necessary to add
Output Slit
2 – triplets
1- doublet
1 - 45° dipole
CICLOPE
Degrader
Improvement in intensity:
factor ≈ 4-5 with 100W
factor ≈ 80 with 2 kW
Target where fragmentation occurs
courtesy A. Russo

12. Design study : next step
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Design study : next step
Detailed map of the magnetic field
Simulations with the new map
Test with a TANDEM beam and
a limited detector array – elastic scattering
Definition of the Silicon array (size – shape)

13. LNS Collaboration LNL Rosa Alba Giorgio Bellia Antonio Del Zoppo
Alessia Di Pietro
Pierpaolo Figuera
Marcello Lattuada
Concettina Maiolino
Domenico Santonocito
LNL
Interest in this activity for the development of a new HELIOS-like spectrometer at LNL