This invention provides a charged particle source, which comprises an emitter and means fo generating a magnetic field distribution. The magnetic field distribution is minimum, about zero, or preferred zero at the tip of the emitter, and along the optical axis is maximum away from the tip immediately. In a preferred embodiment, the magnetic field distribution is provided by dual magnetic lens which provides an anti-symmetric magnetic field at the tip, such that magnetic field at the tip is zero.

A detection system includes a first electron source configured to generate a first electron beam and to cause the first electron beam to impinge on a sample, a second electron source configured to generate a second electron beam and to cause the second electron beam to impinge on the sample, a detector, and a control system. The control system is configured to control the first electron source to cause the first electron beam to scan an area of the sample, control a charge state of the sample by varying at least one of a landing energy and a beam current of the second electron beam, control the detector to detect electrons emitted by the sample, receive a detector signal from the detector, and generate a voltage contrast image from the detector signal.

Apparatus provide plasma to a processing volume of a chamber. The Apparatus may comprise a plurality of plasma sources, each with at least a dielectric tube inlet which is at least partially surrounded by a conductive tube which is configured to be connected to RF power to generate plasma and a gas inlet positioned opposite the dielectric tube inlet for a process gas and a dielectric tube directly connected to each of the plurality of plasma sources where the dielectric tube is configured to at least partially contain plasma generated by the plurality of plasma sources and to release radicals generated in the plasma via holes in the dielectric tube.