| 主权项 |
1. A charged particle beam instrument comprising:
a specimen chamber maintained at a vacuum; a specimen pre-evacuation chamber connected with the specimen chamber via a gate valve; a vacuum pump for evacuating the specimen pre-evacuation chamber; an outflow flow rate adjusting valve for adjusting the flow rate of gas exhausted from the specimen pre-evacuation chamber by the vacuum pump; a pressure gauge for measuring the pressure inside the specimen pre-evacuation chamber; and a controller for controlling the outflow flow rate adjusting valve, wherein said controller performs an operation for controlling the outflow flow rate adjusting valve to a first degree of opening, an operation for making a decision as to whether the difference between a first pressure inside the specimen pre-evacuation chamber measured by the pressure gauge before the outflow flow rate adjusting valve is controlled to the first degree of opening and a second pressure inside the specimen pre-evacuation chamber measured by the pressure gauge after the outflow flow rate adjusting valve has been controlled to the first degree of opening is greater than a first reference value, and an operation for controlling the outflow flow rate adjusting valve to a second degree of opening smaller than the first degree of opening if the decision is affirmative to indicate that the difference between the first and second pressures is greater than the first reference value. |
