As we know, there are several weird symptoms related to LHRS since Jan 15, ~13:00. There is a summary of the problem and their time frame:
Lost Edtpl: -------------------------------------------------------- It's shown 10% edtpl pulse is missed in LHRS TDC. It's Normal in run#5192 ; Little sign in run#5195; Stable Loss since run#5196
L1a over counting -------------------------------------------------------- It appears LHRS scalar is constantly over counting in L1a signal. Old dead time algorithm basing on this value would result an apparent negative dead time. (Discussed in Entry thread of #256271) It's normal in 5178; 17% over counting in 5179; 0% for 5180; 21% for 5185; 28% for 5187;
Helicity Signal -------------------------------------------------------- Helicity ADC signal do not consist with the G0 helicity. Shown in Halog # 256270 Normal in 5178; Stable Diff between ADC helicity and G0 signal. Since 5179
Extra peak in Left Gas Cerenkov ADC -------------------------------------------------------- As discussed in Entry # 256402 It's Normal in 5178; Little worse in 5179; Noise peak stays since 5187
Conclusion -------------------------------------------------------- It's shown that the problem comes after run #5179 and gets stable after run #5196. However between these two runs, there are two major down: Coda crashes and Target Ladder Problem. So most run in between are small test runs.
One preliminary guess to be tested is that, LHRS DAQs could have chance to receive multiple L1a at single events. As a result, ADC might have larger pedestal by having a longer ADC gate (due to L1a pile up) and TDC might lost correct stop.