Performance of the improved larger acceptance spectrometer: VAMOS++

M. Rejmund (1) , B. Lecornu (1) , A. Navin (1) , C. Schmitt (1) , S. Damoy (1) , O. Delaune (1) , J.M. Enguerrand (1) , G. Frémont (1) , P. Gangnant (1) , L. Gaudefroy (2) , B. Jacquot (1) , J. Pancin (1) , S. Pullanhiotan (3) , C. Spitaels (1)

1 GANIL - Grand Accélérateur National d'Ions Lourds
2 DAM/DIF - DAM Île-de-France
3 Inter University Accelerator Centre

Measurements and ion optic calculations showed that the large momentum acceptance of the VAMOS spectrometer at GANIL could be further increased from $\sim$ 11% to $\sim$ 30% by suitably enlarging the dimensions of the detectors used at the focal plane. Such a new detection system built for the focal plane of VAMOS is described. It consists of larger area detectors (1000 mm × 150 mm) namely, a Multi-Wire Parallel Plate Avalanche Counter (MWPPAC), two drift chambers, a segmented ionization chamber and an array of Si detectors. Compared to the earlier existing system (VAMOS), we show that the new system (VAMOS++) has a dispersion-independent momentum acceptance . Additionally a start detector (MWPPAC) has been introduced near the target to further improve the mass resolution to $\sim$ 1/220. The performance of the VAMOS++ spectrometer is demonstrated using measurements of residues formed in the collisions of 129Xe at 967 MeV on 197Au.

Domaines: Instrumentations et Détecteurs [physics.ins-det]

M. Rejmund, B. Lecornu, A. Navin, C. Schmitt, S. Damoy, et al.. Performance of the improved larger acceptance spectrometer: VAMOS++. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011, 646, pp.184-191. ⟨10.1016/j.nima.2011.05.007⟩. ⟨in2p3-00592318⟩