Title :
Emittance measurement of space charge dominated electron beam confined by a longitudinal magnetic field
Author :
Hayashi, Y. ; Okino, A. ; Hotta, E.
Author_Institution :
Dept. of Energy, Tokyo Inst. of Technol., Japan
Abstract :
Summary form only given, as follows. In microwave devices, the quality of electron beam is of considerable importance. For an axisymmetric beam in a uniform focusing channel, the emittance of the beam is related with the transverse electron temperature and the beam radius. While, the transverse electron temperature can be uniquely defined as a function of the electron density profile. Therefore, measuring the radial distribution of the electron density allows us a determination of the transverse electron temperature and thus the beam emittance. We present a method of measuring the beam emittance using a multi-layer Faraday cup. The experiment is done by directly measuring the beam current that flows into each layer of the Faraday cup, and these currents are then converted to the radial profile of the current density. The transverse temperature and emittance of the beam are calculated by fitting the current profile obtained from the measurement and that from the calculation. This method enables us to measure the emittance of a space charge dominated electron beam confined by a longitudinal magnetic field. The measurement is straightforward and it is possible to avoid the electron deflection and plasma generation due to the electron hitting the slits in a slit-slit method. The proposed method has been used to measure the emittance of a matched beam in a uniform compressing channel. The details of the method and experimental results are presented.
Keywords :
current density; electron beam focusing; electron beams; electron density; particle beam diagnostics; space charge; Faraday cup; axisymmetric beam; beam current; beam emittance; beam radius; current density; current profile; electron beam; electron deflection; electron density; electron density profile; emittance measurement; longitudinal magnetic field; matched beam; microwave devices; multi-layer Faraday cup; plasma generation; radial distribution; radial profile; slit-slit method; space charge dominated electron beam; transverse electron temperature; transverse temperature; uniform compressing channel; uniform focusing channel; Charge measurement; Current measurement; Density measurement; Electron beams; Electron emission; Magnetic field measurement; Plasma confinement; Plasma measurements; Plasma temperature; Space charge;
Conference_Titel :
Pulsed Power Plasma Science, 2001. IEEE Conference Record - Abstracts
Conference_Location :
Las Vegas, NV, USA
Print_ISBN :
0-7803-7141-0
DOI :
10.1109/PPPS.2001.961143