A team of specialists conducts a new round of radar scans, ramping up scientific rigor to test the theory that hidden chambers exist behind the tomb walls.

【翻译】一个专家小组进行了新一轮的雷达扫描，这次提高了科学的严谨程度，以检测神秘墓室就存在于墓墙后的这个推测。

【分析】ramping 的逻辑主语是A team of specialists。 that hidden chambers exist behind the tomb walls 是theory 的同位语从句。