Laboratori Nazionali del Sud

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Equipment

Magnex

MAGNEX is a large acceptance magnetic spectrometer installed at the INFN-LNS laboratory in Catania [1]. It is a high-performance device merging the advantages of the traditional magnetic spectrometry with those of a large angular (50 msr) and momentum (-14%, +10.3%) acceptance detector. The spectrometer is composed of two large aperture magnets, namely a quadrupole followed by a 55° dipole and a Focal Plane Detector (FPD) for the detection of the emitted ions. The apparatus is shown in Figure 1.1 and Figure 1.2.

Figure 1.1 MAGNEX at the INFN-LNS. From the left to the right the scattering chamber, the quadrupole (red) and the dipole (blue) magnets, and the FPD chamber are visible.

 

The quadrupole magnet focuses in the non-dispersive (vertical) direction, while the dipole magnet provides the dispersion and the focusing strength in the dispersive direction (horizontal). The horizontal focus is obtained by the inclination of both the entrance and exit dipole boundaries by an angle of -18°. Two sets of surface coils are inserted between the dipole poles and the vacuum vessel. These coils generate a tunable quadrupole (α coil) and sextupole (β coil) strength. The accepted magnetic rigidities range from  ~ 0.2 Tm to ~ 1.8 Tm, corresponding to energies of the detected ions ranging from E ~ 0.2 AMeV to E ~ 40 AMeV, depending on their mass and charge. The characteristics of the magnets and the main optical parameters are listed in Table 1.1 and Table 1.2, respectively.

 

Figure 1.2 Schematic view of MAGNEX.

 

Table 1.1: Parameters of the dipole and the quadrupole

Dipole
Maximum field 1.15 T
Bending angle 55°
Bending radius ρ 1.60 m
ρmin, ρmax 0.95, 2.35 m
Pole gap 18 cm
Entrance and exit pole face rotation -18°
Surface coils
Maximum value for α (at 1.15 T) 0.03
Maximum value for β (at 1.15 T) 0.03
Quadrupole
Maximum field strength 5 T m-1
Radius of aperture 20 cm
Effective length 58 cm

 

Table 1.2: Main optical characteristics of MAGNEX spectrometer.

Optical characteristics Actual values
Maximum magnetic rigidity (Tm) 1.8
Solid angle (msr) 50
Horizontal angular acceptance (mr) -90,+110
Vertical angular acceptance (mr) ±125
Momentum acceptance (%) -0.14,+0.1
Central path length (cm) -596
Momentum dispersion (cm/%) 3.68
First order momentum resolution 5400
Focal plane rotation angle (degrees)59.2 0.03
Focal plane length (cm) 92
Focal plane height (cm) 20

 

[1] F. Cappuzzello, C. Agodi, D. Carbone and M. Cavallaro “The MAGNEX spectrometer: Results and perspectives”, Eur. Phys. J. A (2016) 52: 167. DOI 10.1140/epja/i2016-16167-1

 

 

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