RADAR COMMON DIGITIZER FAILS CAUSING GHOST TARGETS TO OFFSET ACTUAL TARGETS. CTLR ISSUED DSCNT BASED UPON FALSE TARGETS TOWARDS OPPOSITE DIRECTION TFC BELOW. CTLR INSTRUCTOR STOPPED THE DSCNT BEFORE LOSS OF SEPARATION.

Narrative

I WAS CONDUCTING OUT AT THE FFO SH SECTOR; AND AT APPROX XA10Z ACR X RPTED TURB AT FL370 AND REQUESTED RIDE RPTS. SHORTLY THEREAFTER; THE IND RADAR CD (COMMON DIGITIZER) FAILED CAUSING MANY OF OUR RADAR TARGETS TO DISAPPEAR; AND NEW 'GHOST' TARGETS TO APPEAR TRACKING APPROX 90 DEGS L OF THE ACTUAL TARGET. NOT RECOGNIZING ACR Y AS TFC; THE TRAINEE DSNDED ACR X TO FL330. ACR X'S REAL TARGET HAD DISAPPEARED AND IT APPEARED AS IF AN IMMINENT SIT WAS DEVELOPING BTWN ACR X AND ACR Z. HOWEVER; ACR X WAS TRACKING ON A GHOST TARGET AND WAS NOWHERE NEAR ACR Z. ACR X WAS 'NOSE TO NOSE' WITH ACR Y. WHEN I REALIZED THAT SOMETHING WAS WRONG; I IMMEDIATELY TOLD ACR X TO STAY AT FL370. IT TOOK SEVERAL MINS FOR ALL TARGETS TO CORRELATE ON THEIR ORIGINAL; 'TRUE' TARGETS. AT ONE INSTANT; A MODE C INTRUDER APPEARED AT FL370. IT TURNED OUT TO BE ANOTHER ACR; WHO WAS STILL ABEAM INDIANAPOLIS 80 MI W. THIS WAS A VERY SCARY SIT ESPECIALLY SINCE CONFLICT ALERT ACTIVATED BTWN ACR Z AND ACR X WHO WERE REALLY NOT TFC. THE NATURAL REACTION WOULD HAVE BEEN TO DSND ACR X; BUT THAT WOULD HAVE BEEN DISASTROUS WITH ACR Y.