1. Vamos + Exogam Spectrometer

2. Goals VAMOS was designed for spectroscopy studies
using different reaction types
in particular induced by low intensity radioactive beams
Advantages
large acceptance
variable mode
Coupling with
EXOGAM
TIARA, DIAMANT
INDRA
(Neutron Wall)
Main working modes
magnetic spectrometer
separator

3. VAMOS Spectrometer Schematic View
QUADRUPOLES
EXOGAM
BEAM
Focal Plane detection
DIPOLE
Velocity Filter

4. VAMOS in reality

5. Specifications Quadrupoles (850 A) Q1 Q2 Magnetic length [m] 0.6 0.9
Field gradient [T/m]
Bρ full(reduced) Ω [Tm] (2.2)
Dipole (850 A)
Magnetic field [T] 1.2
Magnetic length [m] 1.57
Deflection radius [m] 1.5
Bρ at 60° [Tm] 1.8
Wien Filter
Length [m] 1
Gap [m] 0.15
E [kV] 300
B [T] 0.2

6. Specifications Path length 7.3 m Rotation 0°-90°
Solid angle 100 msr Translation m
Momentum ±7 % Focal Plane
Dispersion 2.5 cm/% Angle 0°-60°
Example:
Θ : -100, +100 [mrad]
Bρ : (0.97,1,1.03)BNc

7. Light/Fast Ion Detection Dispersive Plane
Drift Chamber
X: charge distribution
2 x 64 pads (6.3x50) mm
XFWHM ~200 μm
Y: drift time
YFWHM ~ 500 μm
Ionisation Chamber
2 x 7 pads (50x50) mm
1 x 7 pads (50x 170)mm
ΔEFWHM ~ 3%
Plastic Detector
EFWHM ~ 4%
Silicon Wall

8. Heavy/Slow Ion Detection
Ionisation Chamber
Secondary electron Detector
Se-D
XFWHM ~ 1 mm
YFWHM ~ 2 mm
TFWHM ~ 300 ps
Mylar emissive foil

9. VAMOS Measurement Resolution Θ 0.1° Φ 0.3° Bρ 0.5% M/q 0.5% q 1/30
Θ 0.1°
Φ 0.3°
Bρ 0.5%
M/q 0.5%
q 1/30
M 1/200
Z 1/30 φf θf V Bρ
M/q M q Z φ θ Yf Xf
TOF ΔE E
M/q ~ Bρ x TOF
M ~ E x TOF2
Z2 ~ E x ΔE ~ ΔE/TOF2

10. EXOGAM 12 closely packed Compton suppressed Ge segmented clover
detectors
Efficiency ~ 12% at 1.33 MeV

12. Deep Inelastic Collisions measured with VAMOS
dE vs E

13. Deep Inelastic Collisions measured with VAMOS
M vs M/Q

14. Search for 2+ in 54Ca magicity at N=34
-10 -5
f5/2
p1/2
p3/2
f7/2
48Ca
54Ca
Large experimental effort to
estimate this gap from
studies of nearby nuclei.
Direct information on this gap
is the 2+ energy.
Pronounced shell gap
in 54Ca

15. Identification spectra
dE vs E
dE vs E
M vs M/Q

16. Spectra of 50Ca
γ-γ projection
γ-γ projection
γ-γ gate

17. Spectra of 52Ca

18. Recoil (Decay) Tagging
Reaction: + 208Pb -> 222Th + 4n
Time stamping:
Time correlations measured
using the universal clock CENTRUM
SetUp:
EXOGAM
VAMOS
at 0º with focal plane at 10º using WIEN filter
focal plane detection: SeD, SiWall

19. Recoil Decay Tagging