# Review of Liquid Argon Detector Technologies in the Neutrino Sector
## 2 Single-Phase Experiments
### DUNE (Single-Phase Far Detector)
The anticipated nominal cathode bias is \(-\)180 kV, provided through a dedicated HV feedthrough based on the venerable ICARUS T600 design, giving a drift field of 500 V/cm across each of the 3.6 m wide drift volumes. Figure 23: (**Left**) A section of one of the ProtoDUNE-SP CPAs, showing 6 of the 1.2 \(\times\) 2 m Kapton-laminated FR4 RP elements mounted in the FR4 supporting frame. Each complete DUNE-SP CPA will consist of 300 elements, i.e., 50 of these sections. (**Right**) One of the ProtoDUNE-SP field cage endwalls, using the same design that will be implemented in DUNE-SP. The individual rolled aluminium profiles can be seen, mounted on the FR4 structural framework and electrically interconnected. Similar assemblies are present on the top, bottom and other end of the TPC. Both taken from [47]. The wire-based APAs will follow the same three plane (two induction + one collection) design utilised in other single-phase LArTPCs, but due to the large area they are required to cover, each \"module-sized APA\" will in fact consist of 50 individual but electrically connected 6 \(\times\) 2.3 m APAs (with therefore a total of 150 such APAs in DUNE-SP) [47]. The schematic layout of one such APA is depicted in Figure 24, with Figure 25 showing a fully assembled device. In total, each APA contains 2560 readout wires, with wire spacings of 4.669 mm on the induction planes (denoted by U and V, each consisting of 800 wires) and 4.790 mm on the collection plane (denoted by X, with 960 wires), and plane spacings of 4.75 mm. While this is slightly wider wire spacing than the 3 mm employed by previously described detectors, and studies do show that a smaller spacing (therefore allowing more wires per plane) does result in a marginal improvement (\(\approx\)1%) in detector performance, it has been determined [47] that the cost of adding additional wires is not justified for such a small gain. The induction planes have wires orientated at \(\pm\)35.7\({}^{\circ}\) to vertical, and the wires of the collection plane are orientated vertically. Similarly to the LArIAT APA, a fourth plane of 960 vertical wires-denoted by G-is positioned inwards from the U induction plane, i.e., closer to the cathode. This plane is not read out, but acts as an electronic shield and improves the U plane signal quality [47]. Outside the collection plane is a fine mesh, which acts as a ground plane that shields the wire planes from outside interference and improves the wire signal quality by uniformly terminating the drift field. As seen on Figure 22, the middle APA is shared between two drift volumes, and therefore is required to be sensitive on both sides. To achieve this, the induction plane wires are wrapped around the APA frame, as depicted on Figure 24. This wrapping also necessitates the choice of the orientation angle: at 35.7\({}^{\circ}\), each induction plane wire only crosses each collection plane wire once across both sides of the APA [47]. This therefore removes any ambiguities that might otherwise occur if an angle of 60\({}^{\circ}\) is used, as in previously described detectors. Figure 24: A schematic view of one of the 6 \(\times\) 2.3 m APAs to be used in DUNE-SP. The four wire planes (U, V, X and G) are labelled, with the wrapping of the induction plane wires also indicated. Elements of the cold front-end electronics are depicted by the blue boxes on the right side. Note that when installed in the detector, the electronics boxes will be at the top—i.e., the APA will be rotated anticlockwise 90\({}^{\circ}\) from this drawing. Taken from [47]. The readout system to be implemented in DUNE-SP follows the same pattern of cold and warm electronics described previously for SBND-which, as previously mentioned, partly acts as a prototype and testing platform for many DUNE-SP designs and systems. Certain elements of the DUNE-SP wire readout-specifically, the front-end electronics with ASICs comprising amplifiers, pulse-shaping, ADCs and multiplexing-are located on the APA frames themselves, within the LAr environment [47].