X-ray tube with cooled shield between target and rotor

An X-ray tube comprising:

• an evacuated envelope including first and second end portions made of glass and an intermediate portion made of metal, said first end portion having a smaller diameter than said intermediate portion;
• a cathode unit disposed in said evacuated envelope;
• an anode unit disposed in said evacuated envelope and including a target received in said intermediate portion and facing the cathode unit, a rotor disposed in said first end portion and a shaft interconnecting said target and said rotor;
• a shielding ring made of a heat conductive material and connected to said intermediate portion at its outer peripheral portion and to said first end portion at its inner peripheral portion, thereby constituting a part of said envelope, the inner periphery of said shielding ring extending between said target and said rotor, thereby protecting said first end portion against electrons emitted from said target;
• and
• an insulation cylinder including a first section surrounding said first end portion and a second section adjacent to at least a portion of said shielding ring, said first and second sections, said shielding ring and said first end portion defining a region through which a cooling medium may flow to cool said shielding ring and first end portion.