NMAC IN CLASS B AIRSPACE. NON DETECTION OF NORAC TFC BY APCH CTL RADAR.

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AS CAPT AND PF; WE HAD JUST RECEIVED DSCNT CLRNC FROM CLT APCH CTL TO DSND TO 7000 FT (FROM 9000 FT) AND TURN TO A HDG OF 110 DEGS. OUR POS WAS RWY 26 NM NW OF CLT INBOUND ON THE SHINE 5 ARR AND THE VECTOR WAS TO POS OUR FLT IN SEQUENCE WITH TFC TO LAND ON CLT RWY 18R. PASSING 8400 FT DSNDING; OUR TCASII ISSUED A TA OF AN INTRUDER AT 12 O'CLOCK AND 600 FT BELOW US. BOTH MY FO AND I SCANNED OUTSIDE BUT NO CONTACT. IMMEDIATELY THE TCASII ISSUED A RA TO CLB -- CLB -- CLB; AND THE TCASII IVSI CALLED FOR A POS CLB TO MORE THAN 1500 FPM. I IMMEDIATELY COMPLIED AND CLBED UNTIL THE IVSI WAS 'IN THE GREEN' OF THE TCASII. AT THAT MOMENT; THE FO SAW THE INTRUDER ACFT AND SAID THE CLB THAT I HAD INITIATED WAS SUFFICIENT TO MISS THE ACFT BUT NOT 'TO DSND -- HE'S RIGHT UNDER US.' I TOLD THE FO TO NOTIFY ATC THAT WE WERE COMPLYING WITH A TCASII RA AND HAD CLBED BACK TO 9000 FT. ATC ADVISED THAT HE NOW OBSERVED THE 'POP UP' TFC AT 8500 FT AND IN VIOLATION OF CLASS B AIRSPACE. ATC FURTHER ADVISED THAT ZTL WOULD BE NOTIFIED AND TRY TO TRACK THE INTRUDER ACFT TO IT'S LNDG TO TRY TO IDENT THE PLT. I WAS ALSO ASKED TO CALL CLT RADAR ROOM WITH FOLLOW-UP DETAILS. AS PF AND CAPT; I NEVER SAW THE ACFT IN QUESTION; BUT MY FO (VISIBLY SHAKEN) ADVISED THAT THE TCASII ADVISORY 'SAVED US.' HE TOLD ME THAT HAD I NOT REACTED TO THE TCASII AND CONTINUED ALONG THE FLT PATH WE WERE FLYING; A COLLISION WAS CERTAIN. I CALLED CLT RADAR ROOM AND SPOKE WITH A SUPVR WHO TOLD ME THAT HE WAS FILING A RPT (I HAVE DONE THE SAME WITH MY CARRIER) AND THAT ATC SEPARATION WAS NEVER LOST DUE TO OUR FOLLOWING THE TCASII TA/RA ADVISORY. HE FURTHER ADVISED THAT HE HAD NO PROB WITH THE ENTIRE EPISODE EXCEPT THAT THE INTRUDER ACFT WAS IN VIOLATION OF HIS AIRSPACE WITHOUT CLRNC. AS I TOLD MY CHIEF PLT; PLEASE PASS ALONG TO THE TCASII MANUFACTURER COMMUNITY THAT THEIR PRODUCTS ARE SAVING LIVES; AND THANK YOU!