The axial velocity spread was measured using a pin-hole and phosphor screen and the result was compared with the theoretical estimation. The theoretical calculations had been performed by using a new single-cusp gun theory that considered the discrepancy of the electron beam line and the magnetic flux line in the area of the cathode and anode. The specific thing of the new theory is the possibility of a fairly low velocity spreads just by controlling the distance between the cathode and the magnetic cusp, under well optimized another parameters. In this experiment, to verify the validity the theory, a 30 kV, 1.0 A Pierce-type electron gun was used with a peak magnetic flux density of 4.38 kG. The magnetic field has an asymmetric magnetic cusp by which the electron beam can be made to be an axis-encircling electron beam. And the position of the cathode can be changed using a micrometer to control the distance between the cathode and the magnetic cusp. To measure the axial velocity spread, a small amount of the electron beam was sampled using a pin-hole and the image of it on the phosphor screen was analyzed to calculate the axial velocity spread. The velocity ratio of the electron beam denned as the transverse velocity over axial velocity was also measured using the capacitive probe. The velocity ratio should be obtained before calculating the axial velocity spread because it has to be used in the analysis of the electron beam image on the phosphor screen. The result of the measurement of the axial velocity spread followed closely the theoretically estimated values. The minimum value of the axial velocity spread was about 2%.
|Number of pages||1|
|Journal||IEEE International Conference on Plasma Science|
|Publication status||Published - 2003|
|Event||2003 IEEE International Conference on Plasma Science - Jeju, Korea, Republic of|
Duration: 2003 Jun 2 → 2003 Jun 5