  During the shutdown of the CERN Large Hadron Collider in 2013-2014, an
additional pixel layer was installed between the existing Pixel detector of the
ATLAS experiment and a new, smaller radius beam pipe. The motivation for this
new pixel layer, the Insertable B-Layer (IBL), was to maintain or improve the
robustness and performance of the ATLAS tracking system, given the higher
instantaneous and integrated luminosities realised following the shutdown.
Because of the extreme radiation and collision rate environment, several new
radiation-tolerant sensor and electronic technologies were utilised for this
layer. This paper reports on the IBL construction and integration prior to its
operation in the ATLAS detector.
