A high power (900 mJ, 35 fs) laser pulse is focused into a gas jet (length 2 mm) and a monoenergetic electron beam is emitted from the laser-induced plasma density wake behind the laser pulse. High quality monoenergetic electron beams with central energy up to 183 MeV are generated. The beam is fully characterised in terms of the charge, transverse emittance, energy spread and bunch length. In particular, the energy spectrum (with less than 1% measured energy spread) is obtained using a high resolution magnetic dipole imaging spectrometer
