An insulative assembly for a microwave vacuum tube comprising: an oil tank and at least one high temperature or high voltage component arranged in the oil tank. The oil tank has an internal groove. The at least one high temperature or high voltage component is spaced apart from the internal groove within the oil tank; wherein the internal groove is configured to separate gas bubbles from the at least one high temperature or high voltage component within the oil tank during operation.

An insulative assembly for a microwave vacuum tube comprising: an oil tank and at least one high temperature or high voltage component arranged in the oil tank. The oil tank has an internal groove. The at least one high temperature or high voltage component is spaced apart from the internal groove within the oil tank; wherein the internal groove is configured to separate gas bubbles from the at least one high temperature or high voltage component within the oil tank during operation.