Information recording apparatus having a vacuum system

An information recording apparatus having a vacuum system, comprising:

• a vacuum chamber connected with a first evacuator means;
• an electronic beam producing means partially enclosed in the vacuum chamber for emitting an electronic beam for recording information on a recording medium;
• a moving stage provided in the vacuum chamber for linearly moving the recording medium in a vacuum atmosphere within the vacuum chamber;
• a spindle disposed in the vacuum chamber for rotating the recording medium, said spindle being rotatably driven by a spindle motor;
• a magnetic fluid seal producing means provided around the spindle on the vacuum chamber side;
• a pressure differential chamber provided around the spindle, said pressure differential chamber being connected with a second evacuator means;
• a protection circuit responsive to a pressure within the vacuum chamber and a pressure within the pressure differential chamber, and the protection circuit controlling a first valve means connected between the vacuum chamber and the pressure differential chamber in order that a pressure difference between the vacuum chamber and the pressure differential chamber is constantly under a predetermined threshold value;
• and
• a control circuit responsive to a pressure within the vacuum chamber and a pressure within the pressure differential chamber, the control circuit controlling second and third valve means connected respectively with the vacuum chamber and the pressure differential chamber, such that a pressure difference between the vacuum chamber and the pressure differential chamber does not exceed a predetermined value.