SMA HIT TURBULENCE ENROUTE TO IAF FOR APCH AND HAD LESS THAN STANDARD SEPARATION WITH ANOTHER ACFT ON APCH.

Narrative

ZSE CTLR ISSUED PLT NOTIFICATION TO ME BECAUSE IFR SEP WAS NOT MAINTAINED AND QUALITY ASSURANCE ALARM WENT OFF IN CONTROL ROOM. ON AN IFR TRNING FLT; MY STUDENT AND I WERE EXPERIENCING MODERATE TURB WHEN THE CTLR DSNDED US FROM 4000' TO 3000' TO BEGIN APCH. WE PROCEEDED DIRECT TO THE IAF TO BEGIN APCH THERE WE EXPERIENCED A SEVERE DOWNDRAFT WE LOST 200' AND BROKE IFR SEP BECAUSE THEIR WAS A PLANE BELOW US. AT THE TIME OF THIS INCIDENT A NON CONVECTIVE SIGMET NAME ALPHA 2 WAS IN EFFECT FOR MODERATE TO OCCASIONALLY SEVERE TURB FROM THE SURFACE TO 12000' FOR WA AND OR AND COASTAL WATERS. ME ACTING AS PIC SHOULD NOT BE HELD RESPONSIBLE FOR THIS ACT. 1) I WAS IN THE CAPACITY AS FLT INSTR AND DID NOT HAVE HANDS ON WHEN THE INCIDENT OCCURRED. 2) DUE TO THE SIGMET THAT WAS IN EFFECT AT THE TIME THE DOWNDRAFT WE EXPERIENCED IS AN ACT OF NATURE AND NO MATTER HOW GOOD THE PLT IS; THE SAME CIRCUMSTANCE THE SAME RESULT THERE IS ONLY ONE POSSIBLE SOLUTION I CAN THINK OF THAT WOULD HAVE AVOIDED THIS INCIDENT. WITH THE GIVEN WX CONDITIONS SIGMET ALPHA 2 IN EFFECT FOR TURB; WHY DID THE CTLR DSND US FROM 4000 TO 3000' GIVING US A 1000' SEP BTWN ANOTHER ACFT WHEN SHE COULD HAVE HELD US AT 4000' AND AVOIDED THIS WHOLE THING.