Headpiece has non-magnetic weight with central main non-magnetic weight and concentrated auxiliary non-magnetic weight, where weight proportion of main non-magnetic weight is greater than auxiliary non-magnetic weight

摘要

The headpiece (1) has a non-magnetic weight with a central main non-magnetic weight (2) and a concentrated auxiliary non-magnetic weight. The density of the central main non-magnetic weight and a concentrated auxiliary non-magnetic weight (4) is greater than 2.6 gram per cubic centimeters. A weight proportion of the main non-magnetic weight is greater than the auxiliary non-magnetic weight.