Abstract: A charged particle beam instrument is offered which has a specimen pre-evacuation chamber. An outflow flow rate adjusting valve (70) adjusts the flow rate of gas exhausted from the specimen pre-evacuation chamber (20) under control of controller (82). The controller (82) for making a decision as to whether the difference between a first pressure in the pre-evacuation chamber (20) before the adjusting valve (70) is controlled to the first degree of opening and a second pressure in the pre-evacuation chamber (20) after the adjusting valve (70) has been controlled to the first degree of opening is greater than a first reference value.

Abstract: An electron microscope which permits an operator to perform astigmatic correction and beam alignment. A field of view capable of clearly displaying astigmatism or beam misalignment in terms of a Ronchigram is placed on the optical axis. Then, the operator selects a Ronchigram display mode. A first or second TV camera such as a CCD camera is selected and placed on the optical axis while maintaining the electron optics in the STEM imaging mode. Under this condition, a Ronchigram signal is obtained from the TV camera and supplied to a computer via a TV power supply and an interface. As a result, a Ronchigram of appropriate size and brightness is displayed in an image display region on a display device. The operator corrects astigmatism or adjusts the alignment while observing the Ronchigram.

Abstract: An electron microscope which permits an operator to perform astigmatic correction and beam alignment. A field of view capable of clearly displaying astigmatism or beam misalignment in terms of a Ronchigram is placed on the optical axis. Then, the operator selects a Ronchigram display mode. A first or second TV camera such as a CCD camera is selected and placed on the optical axis while maintaining the electron optics in the STEM imaging mode. Under this condition, a Ronchigram signal is obtained from the TV camera and supplied to a computer via a TV power supply and an interface. As a result, a Ronchigram of appropriate size and brightness is displayed in an image display region on a display device. The operator corrects astigmatism or adjusts the alignment while observing the Ronchigram.