configuration, the uncertainty related to the reactors is reduced to 5% of the uncorrelated uncertainty of a single core (0.8%), which is totally insignificant.

Experience and lessons learned in CHOOZ [@chooz], Palo Verde [@paloverde], and KamLAND [@kamland] were taken into account in designing the Daya Bay detectors. Some unique features of the Daya Bay design significantly improve the detector performance; indeed, the built-in redundancy is crucial for precision measurements. Details of the Daya Bay detector design and fabrication can be found in Ref. [@longdet]. In the following we will briefly describe the experimental design highlighting the concept of multiple muon taggers, multiple antineutrino detectors, a remote-controlled calibration system, photon reflectors and shields, as well as the optimization of the detector dimensions.

Each AD has three nested cylindrical volumes separated by concentric acrylic vessels as shown in Fig. \[fig:det\]. Serving as the target for the inverse beta-decay reaction, the innermost volume holds 20 t of gadolinium-doped liquid scintillator (Gd-LS) with 0.1% Gd by weight [@ding; @ding2; @yeh; @lsproduction]. The middle volume is called the gamma catcher and is filled with 20 t of undoped liquid scintillator (LS) for detecting gamma-rays that escape the target volume. The outer volume contains 37 t 