ACR ON LNDG ROLL AT DTW RECEIVED ATC ASDE-X ALERT; INDICATING TFC ON THE RWY; FLT CREW ACCELERATED LNDG STOP; ATC ADVISED LIKELY FALSE TARGET EVENT.

Narrative

AFTER LNDG AND DURING ROLLOUT ON RWY 22L; WHILE THRUST REVERSERS WERE DEPLOYED AT DETENT 2 (APPROX SPD 120 IAS DECELERATING); ATC INFORMED US IN A SHAKY VOICE; 'COMPANY NUMBER...I AM (IN APPARENT DISBELIEF) GETTING AN INDICATION THERE IS ANOTHER ACFT ON YOUR RWY!' THE PM (FO) IMMEDIATELY ACKNOWLEDGED THE CALL; AND I AS PF (CAPT); BEGAN EVASIVE ACTION OF BRINGING THE ACFT TO A COMPLETE STOP WHILE VISUALLY SEARCHING THE RWY ENVIRONMENT FOR AN INTRUDING ACFT. ONCE MY ACFT WAS STOPPED ON THE RWY (JUST PRIOR TO INTERSECTING RWY 9L); WE INFORMED THE TWR CTLR OF OUR POS; AND HE REPLIED; 'THE TARGET IS IDENTED TO BE BEHIND YOU NOW.' EVENT OVER. TAXIED TO GATE. TERMINATING FLT. THE RPTING OF THIS EVENT IS SOLELY AS A RESULT OF ATC ASDE-X MALFUNCTION. THE FLT CREW WAS NOT ATTRIBUTABLE TO THIS INCIDENT. THE DTW ASDE-X TFC MGMNT SYS SURFACE MOVEMENT RADAR AND XPONDER MULTI-LATERATION SENSORS DISPLAYED A GHOST ACFT POS ON AN ATC TWR DISPLAY. THESE SENSORS MALFUNCTIONED AND WERE NOT ACCURATE OR RELIABLE FOR IMPROVING FLT SAFETY IN MY CASE. ALTHOUGH A FALSE SIGNAL; WE TREATED THE INFO AS A POSSIBLE RWY INCURSION AT THE TIME. THE QUALITY OF THE ASDE-X DATA RESULTED IN THE TWR CTLR RECEIVING HIS DECISION SUPPORT. IN OUR CASE; IF THE ASDE-X DATA WAS ACCURATE; I WOULD NOT BE HERE TO DESCRIBE THE EVENT; HOWEVER. PERHAPS FIXING THIS MALFUNCTION COULD AVOID THIS OCCURRENCE FROM HAPPENING IN THE FUTURE.