The invention relates to a particle radiation device comprising a particle source that is operated in an ultrahigh vacuum and a preparation chamber which can be operated using variable pressures of up to 1 hPa. The inventive particle radiation device has two intermediate pressure areas (7, 8) located between the ultrahigh vacuum area (6) and the preparation chamber (1). The two intermediate pressure areas (7, 8) are purged by means of a pump assembly consisting of a fore-pump (16) and two turbomolecular pumps (13, 14) connected in series, whereby one of the turbomolecular pumps (13) is purged first by the drag phase (24) of the other turbomolecular pump (14). In one example of the invention, the fore-pump (16) is also simultaneously used for evacuating the preparation chamber. In an alternative example, a second fore-pump (20) is provided for evacuating the preparation chamber (1). This assembly allows the ultrahigh vacuum in the ultrahigh vacuum area (6) to be maintained up to pressures of 100 hPa in the preparation chamber (1). The inventive particle radiation device is used in particular as a variable pressure scanning electron microscope (VP-SEM) or as an environmental scanning electron microscope (ESEM).