| 摘要 |
PROBLEM TO BE SOLVED: To provide a small standing wave linear accelerator capable of keeping axial symmetry in the distribution of accelerated electron beams and obtaining the uniformity of intensity distribution of X-rays. SOLUTION: In a first accelerating stage at which electron velocity strongly influenced by accelerated microwave electric field is relatively slow, an additional anode 12, a re-entrant cavity 13, a beam opening 14, an opening 15, a first accelerating cavity 16, and a cavity 17 are constituted in axial symmetry, and thereby, since a accelerated electric field having axial symmetry in a region where the velocity of an electron is not relatively high is generated, electron distribution having axial symmetry can be obtained, and the intensity distribution of X-rays is made uniform. By appropriately setting the voltage, bunching width in the axial direction of an electron group becomes very small, the width of energy spectrum of X-ray becomes small, and characteristics are improved. Since almost all the focused electrons are injected into the first accelerator 16, breakage of a cathode of an electron gun caused by back bombardment of electrons can be prevented. As a result, characteristics of a high electric field small standing wave linear accelerator are substantially enhanced.
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