# Review of Liquid Argon Detector Technologies in the Neutrino Sector
## 2 Single-Phase Experiments
### Icarus T600  
Originally proposed in 1985 [13], the Imaging Cosmic And Rare Underground Signals (ICARUS) program has pioneered many of the techniques for single- and dual-phase LArTPC detector design, assembly and operation that are used by all other experiments operating today. Supported by a long-running research and development framework that included fully realised and operational 3 [14,15] and 14 tonne [16] prototypes, the culmination of the program-the ICARUS T600 single-phase detector was successfully assembled and operated at the Gran Sasso National Laboratories between 2004 and 2013 [17,18]. Following this, the detector was refurbished and moved to Fermilab in 2017 [19], to take its place as the far detector of the Short Baseline Neutrino (SBN) Program [20], with operation expected to begin in 2021. The layout of ICARUS T600 is shown in Figure 2. The detector consists of two identical LAr modules, each with dimensions of 17.95 \(\times\) 3 \(\times\) 3.16 m (giving a combined active LAr mass of 476 tonnes) [21], enclosed in a single cryostat. Each module is split into two drift volumes, arranged \"back to back\" and sharing a common cathode orientated vertically and running lengthwise along the module. A view inside one of the drift volumes is shown in Figure 3. The entire cryostat is surrounded by cosmic ray tagger panels that are used to correlate incident cosmic muons with their corresponding signals in the active LAr [19]. Figure 1: The general detection principle of single-phase Liquid Argon (LAr) detectors. This schematic depicts the assembly in the MicroBooNE detector, which uses a wire-based anode plane assembly for charge readout, but the same principle is broadly applicable to any single-phase design. A description of the operation is given in the main text. Taken from [12]. Figure 3: A view inside one of the four ICARUS T600 drift volumes, showing (1) the cathode, (2) the field-shaping electrodes, and (3) the photomultiplier tube (“PMT”) array for detection of scintillation light. The three wire planes which make up the anode plane assembly are positioned in front of the PMTs, but the individual wires are too thin to be seen on this image. Adapted from [23]. Figure 2: A schematic depiction of the ICARUS T600 detector, with major components labelled. Taken from [22]. Each cathode is made of nine punched stainless steel panels, and nominally biased to \(-75\) kV via a bespoke high voltage (\"HV\") feedthrough [21]. Between the cathode and anode planes, the drift field is created through the use of 29 \"race track\" field-shaping electrodes working in tandem with an attached resistor chain. The distance between the cathode and innermost anode plane-i.e., the drift length-is 1.5 m, and during normal operation the drift field is set at 500 V/cm, corresponding to a maximum drift time in ultra-pure LAr of 950 us [21]. A view of the HV components in situ is shown in Figure 4.  
Each of the ICARUS T600 drift volumes utilises three wire-based anode planes for charge readout. (For consistency with other detectors discussed in this paper, the entire three-plane anode structure is referred to as the \"anode plane assembly\" (APA).) Across all four APAs used in ICARUS T600, there are a total of 53,248 wires [21], with 3 mm spacing between wires and 3 mm spacing between the planes in a single APA. The wires are orientated at 0\({}^{\circ}\) (horizontal) on the innermost plane (i.e., the one closest to the cathode), +60\({}^{\circ}\) for the middle plane, and \(-60^{\circ}\) for the outermost plane. The two inner planes are nominally biased at \(-220\) and 0 V respectively, making them induction planes, and the outermost plane operates in collection mode, being biased at +280 V. Figure 5 shows a close-up view of the wire planes installed in one of the drift volumes. Wire signal acquisition and recording are performed using a system of dedicated ADCs and motherboards housed in custom-built electronics crates.