Experimental study of velocity spread in a cycloiding electron beam

The paper describes briefly the effect of electron velocity spread on the principal operating parameters of a gyrotron. A method of reducing velocity spread is discussed, and a new method of measuring electron velocity spread in a cycloiding electron beam is presented. By use of a high precision radial-gauge and multilobe collector, the distribution of the beam transverse velocity of a gyrotron is accurately measured. Compared with other methods conventionally used in this country and abroad such as those using retarding-field, pin-hole collector, this method is characterized by the fact that the space charge effect would not modify the experimental results, and the beam velocity spread of a gyrotron under real operating conditions can be measured. In order to characterize the beam in an overall manner, a new concept of relative density velocity spread is introduced in this paper. The experimental work has been performed on a special electron beam analyser with advanced design.