Editing Super-Kamiokande (section)

===SK-IV upgrade===
In the previous phases, the ID-PMTs processed signals by custom electronics modules called analog timing modules (ATMs). Charge-to-analog converters (QAC) and time-to-analog converters (TAC) are contained in these modules that had dynamic range from 0 to 450 picocoulombs (pC) with 0.2&nbsp;pC resolution for charge and from −300 to 1000&nbsp;ns with 0.4&nbsp;ns resolution for time. There were two pairs of QAC/TAC for each PMT input signal, this prevented dead time and allowed the readout of multiple sequential hits that may arise, ''e.g.'', from electrons that are decay products of stopping muons.<ref name="auto" />

The SK system was upgraded in September 2008 in order to maintain the stability in the next decade and improve the throughput of the data acquisition systems, QTC-based electronics with Ethernet (QBEE).<ref>{{cite journal |title=Commissioning of the New Electronics and Online System for the Super-Kamiokande Experiment |journal=IEEE Transactions on Nuclear Science |volume=57 |issue=2 |pages=428–432 |year=2010 |last1=Yamada |first1=S. |last2=Awai |first2=K. |last3=Hayato |first3=Y. |last4=Kaneyuki |first4=K. |last5=Kouzuma |first5=Y. |last6=Nakayama |first6=S. |last7=Nishino |first7=H. |last8=Okumura |first8=K. |last9=Obayashi |first9=Y. |last10=Shimizu |first10=Y. |last11=Shiozawa |first11=M. |last12=Takeda |first12=A. |last13=Heng |first13=Y. |last14=Yang |first14=B. |last15=Chen |first15=S. |last16=Tanaka |first16=T. |last17=Yokozawa |first17=T. |last18=Koshio |first18=Y. |last19=Moriyama |first19=S. |last20=Arai |first20=Y. |last21=Ishikawa |first21=K. |last22=Minegishi |first22=A. |last23=Uchida |first23=T. |bibcode=2010ITNS...57..428Y |doi=10.1109/TNS.2009.2034854 |s2cid=5714133}}</ref> The QBEE provides high-speed signal processing by combining pipelined components. These components are a newly developed custom charge-to-time converter (QTC) in the form of an application-specific integrated circuit (ASIC), a multi-hit time-to-digital converter (TDC), and field-programmable gate array (FPGA).<ref>{{citation |author1=H. Nishino |title=High-speed charge-to-time converter ASIC for the Super-Kamiokande detector |journal=Nuclear Instruments and Methods in Physics Research A |volume=610 |issue=3 |date=2009 |pages=710–717 |arxiv=0911.0986 |bibcode=2009NIMPA.610..710N |display-authors=etal |doi=10.1016/j.nima.2009.09.026 |s2cid=110431759}}</ref> Each QTC input has three gain ranges "Small", "Medium", and "Large" – the resolutions for each are shown in Table.<ref name="auto" />

{| class="wikitable"
|+
Summary of QTC ranges for charge acquisition
|-
! Range !! Measuring region !! Resolution
|-
| Small || 0–51 pC || 0.1 pC/count (0.04 pe/count)
|-
| Medium || 0–357 pC || 0.7 pC/count (0.26 pe/count)
|-
| Large || 0–2500 pC || 4.9 pC/count (1.8 pe/count)
|}

For each range, analog-to-digital conversion is conducted separately, but the only range used is that with the highest resolution that is not being saturated. The overall charge dynamic range of the QTC is 0.2–2500&nbsp;pC, five times larger than the old . The charge and timing resolution of the QBEE at the single photoelectron level is 0.1 photoelectrons and 0.3&nbsp;ns respectively, both are better than the intrinsic resolution of the 20-in. PMTs used in SK. The QBEE achieves good charge linearity over a wide dynamic range. The integrated charge linearity of the electronics is better than 1%. The thresholds of the discriminators in the QTC are set to −0.69&nbsp;mV (equivalent to 0.25 photoelectron, which is the same as for SK-III). This threshold was chosen to replicate the behavior of the detector during its previous ATM-based phases.<ref name="auto" />