# Review of Liquid Argon Detector Technologies in the Neutrino Sector
## 2 Single-Phase Experiments
### MicroBooNE
Readout of the wire signals is accomplished through the use of \"application-specific integrated circuits\" (ASICs) that combine pre-amplifiers, digitisers, signal shaping and multiplexing into front-end assemblies arranged in a system broadly similar in function to that used in ICARUS T600 [12]. However, one key difference is that MicroBooNE's front-end electronics are mounted directly on the APA support frames--i.e., within the LAr environment. This has necessitated the development of \"cold electronics\" with low noise and power consumption (thereby minimising heat output), but in return, the short distance and cryogenic environment between the wires and electronics significantly reduces the readout noise, therefore increasing the signal-to-noise ratio [12] (additional general advantages of using cold front-end electronics over off-detector systems are presented in [30]). Custom \"cold cables\" carry signals from the front-end electronics out of the cryostat via the signal feedthrough chimneys. On the external side of these chimneys are mounted the intermediate electronics, which include amplifiers that allow the signals to be carried to the off-detector readout and DAQ systems situated 20 m away from the cryostat [12]. A stopping muon and associated Michel electron candidate, as recorded by the MicroBooNE collection plane, is pictured in Figure 11.  
The light collection system in MicroBooNE serves three separate purposes [12]. The first is, as in ICARUS T600, to provide an event start time by observing prompt scintillation light. The second use is to act as part of the detector's dedicated triggering mechanism for beam neutrino interactions that produce protons with kinetic energy of \(\geq\)40 MeV. (Such interactions also produce a distinct pulse of scintillation light that will be correlated with the known time of a beam spill passing through the detector.) The final purpose of the system is to directly observe the light emitted by lower energy (5-10 MeV) electrons produced in interactions between LAr and supernova neutrinos. The complete light collection system is shown in Figure 12, and comprises two subsystems [12]. The first is an array of 32 8-inch diameter Hamamatsu R5912-02 MOD PMTs, with a TPB-coated acrylic disk individually mounted in front of each one. This separation of the wavelength shifter from the PMT differs from the direct coating method demonstrated at ICARUS T600 (and used in a number of other detectors), but has been done at MicroBooNE for purposes of  
Figure 11: A stopping muon and associated Michel electron candidate as recorded by the MicroBooNE collection plane. ease-of-installation and improving the quality of the TPB in the cryogenic environment [12]. Electromagnetic isolation is achieved by housing each PMT in a cryogenic mu metal shield. The second light collection subsystem consists of 4 50.8 cm long lightguide paddles, built up of six bent acrylic bars (coated with wavelength shifter) that guide incident light to a coupled PMT. This secondary system has been installed in MicroBooNE primarily for R&D purposes: each paddle has a larger coverage than a single PMT, while occupying significantly less space due to their thin shape, making such devices important for future large-scale detectors, as they could allow a correspondingly large-scale light collection system to be realised for reduced complexity, cost and installation time. Alongside development, characterisation and operation of the detector hardware, MicroBooNE's half-decade of operation has allowed for a strong analysis program to be undertaken, covering a wide range of topics including (but by no means limited to) single particle and EM shower reconstruction, energy response calibration and resolution measurements, background identification and rejection techniques, vertex identification and reconstruction, and the use of neural networks for event reconstruction. A comprehensive list of published results can be found in [32].