Patent Number: 
Section: claims

1. A radiation source assembly, comprising a source capsule enclosing a radiation source, a female connector connected to a male connector, and a pigtail connecting the source capsule and the female connector together, wherein a cap connector of said source capsule has first internal threads on its pigtail fitting hole, with said first internal threads having a profile corresponding to a large-diameter coil of said pigtail and engaging with the large-diameter coil of a first end of the pigtail through a thread engagement. 2. The radiation source assembly according to  claim 1 , wherein said female connector has second internal threads on its pigtail fitting hole, with said second internal threads having a profile corresponding to said large-diameter coil of the pigtail and engaging with the large-diameter coil of a second end of the pigtail through a thread engagement. claim 1 3. The radiation source assembly according to  claim 2 , wherein the number of each of said first and second internal threads is four or more. claim 2 4. The radiation source assembly according to  claim 1 , wherein the number of said first internal threads is four or more. claim 1 5. A radiation source assembly, comprising: a capsule body receiving stacked radiation source disc targets;  a capsule lid fitted into an open end of said capsule body and welded to said capsule body, thus sealing the capsule body; and  a coil spring set within a spring seat hole of said capsule lid and adapted to normally bias the radiation source disc targets within the capsule body in a direction after the capsule lid is welded to the capsule body.