"Table below provides timestamps ordered achronologically and represents the sequence of events that occurred in the analyzed circuit: PIC_RQD, PIC_RQF, iQPS, nQPS, FGC_RQD, FGC_RQF, EE_RQD, EE_RQF and optionally LEADS_RQD and LEADS_RQF, provided they exist. Note that for iQPS and nQPS only the first timestamp is reported. Tables with all iQPS and NQPS timestamps are presented in the section dedicated to magnet and quench protection analysis. The table also contains time difference in milliseconds from the first event and from the FGC event.\n",
"\n",
"In short, the following criteria should be kept:\n",
"- The PC timestamp (51_self) is QPS time stamp +/-20 ms.\n",
"- Time stamp difference between FGC and EE: 100±15 ms \n",
"- The PC timestamp (51_self) is QPS time stamp +/-40 ms.\n",
"- Time stamp delay between PIC and EE: 100±15 ms \n",
"\n",
"If one or more of these conditions are not fulfilled, then an in-depth analysis has to be performed by the QPS team."
source: Test Procedure and Acceptance Criteria for the 13 kA Quadrupole (RQD-RQF) Circuits, MP3 Procedure, <ahref="https://edms.cern.ch/document/874714">https://edms.cern.ch/document/874714</a> (Please follow this link for the latest version)
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# Analysis Assumptions
- We consider standard analysis scenarios, i.e., all signals can be queried. If a signal is missing, an analysis can raise a warning and continue or an error and abort the analysis.
- It is recommended to execute each cell one after another. However, since the signals are queried prior to analysis, any order of execution is allowed. In case an analysis cell is aborted, the following ones may not be executed (e.g. I\_MEAS not present).
# Plot Convention
- Scales are labeled with signal name followed by a comma and a unit in square brackets, e.g., I_MEAS, [A].
- If a reference signal is present, it is represented with a dashed line.
- If the main current is present, its axis is on the left. Remaining signals are attached to the axis on the right. The legend of these signals is located on the lower left and upper right, respectively.
- The grid comes from the left axis.
- The title contains timestamp, circuit name, and signal name allowing to re-access the signal.
- The plots assigned to the left scale have colors: blue (C0) and orange (C1). Plots presented on the right have colors red (C2) and green (C3).
- Each plot has an individual time-synchronization mentioned explicitly in the description.
- If an axis has a single signal, then the color of the label matches the signal's color. Otherwise, the label color is black.
Table below provides timestamps ordered achronologically and represents the sequence of events that occurred in the analyzed circuit: PIC_RQD, PIC_RQF, iQPS, nQPS, FGC_RQD, FGC_RQF, EE_RQD, EE_RQF and optionally LEADS_RQD and LEADS_RQF, provided they exist. Note that for iQPS and nQPS only the first timestamp is reported. Tables with all iQPS and NQPS timestamps are presented in the section dedicated to magnet and quench protection analysis. The table also contains time difference in milliseconds from the first event and from the FGC event.
In short, the following criteria should be kept:
- The PC timestamp (51_self) is QPS time stamp +/-20 ms.
- Time stamp difference between FGC and EE: 100±15 ms
- The PC timestamp (51_self) is QPS time stamp +/-40 ms.
- Time stamp delay between PIC and EE: 100±15 ms
If one or more of these conditions are not fulfilled, then an in-depth analysis has to be performed by the QPS team.
Table below contains reference timestamps of signals used for comparison to the analyzed FPA. The reference comes as the last PNO.b3 HWC test with activation of EE systems and no magnets quenching.
Naturally, this formula only applies to exponential decayed characterised by a time constant. Nonetheless, for pseudo-exponential decays, this formula gives a notion of the change of the characteristic time $\tilde{\tau}$. For a circuit we compute the time-varying characteristic time as
- Check if the characteristic time of the pseudo-exponential I_MEAS decay from t=1 to 100 s is 25 s< Tau < 35 s
*GRAPHS* (one for each circuit):
- The main power converter current (reference and actual) on the left axis, I_MEAS
- The characteristic pseudo time constant calculated for the main current (reference and actual) on the right axis, -I_MEAS/dI_MEAS
The actual characteristic pseudo time constant contains discrete steps, which indicate a quenching magnet (decreasing L, increasing R); note that for the reference one the steps are not present (no quench).
- Timing of PIC abort, FGC timestamps, the maximum currents, and the characteristic times are reported next to the graph.
- t = 0 s corresponds to the respective (actual and reference) FGC timestamps.
source: Test Procedure and Acceptance Criteria for the 13 kA Quadrupole (RQD-RQF) Circuits, MP3 Procedure, <ahref="https://edms.cern.ch/document/874714/5.1">https://edms.cern.ch/document/874714/5.1</a>
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## 8.1. Plot of Voltage Across All Magnets (U_DIODE_RQx)
*GRAPHS* (one for each circuit):
t = 0 s corresponds to the PM timestamp of the FGC
First plot (global)
- the power converter current on the left axis, I_MEAS
- diode voltage on the right axis, U_DIODE_RQx
Second plot (zoom)
- the power converter current on the left axis, I_MEAS
- PM for quench detection signals for 1 s before and 400 s after the FGC PM timestamp; if a quench detection signal is present, it means that a magnet quenched. Since there are two QPS boards (so called boards A and B), there are twice as many PM entries as quenched magnets.
*ANALYSIS*:
- calculates the current at which a quench occured by finding the timestamp of the current dataframe (i_meas_df) closest to the quench time and the curresponding value of current
- compute the time difference (in seconds) from the first quench - dt_quench
## 8.3. Analysis of Quench Detection Voltage and Logic Signals for Quenched Magnets
If a quadrupole magnet naturally quenches the QPS system (old or iQPS) records a PM file. This file containts the data from the two quench detectors for RQD and RQF (called INT and EXT). The aperture which quenches first defines the common PM time stamp. The PM data is however recorded by two individual boards. Since there is only one common heater circuit for both apertures, the non-quenching aperture will also be warmed up by the heaters and will quench. This heater induced quench which comes some time after the primary quench which triggered the PM is recorded by its quench detector when it is reaching the 100mV. Since the system has only one absolute time stamp (the one of the primary quench) the secondary, heater induced, quench appears in the PM at the same time as the primary quench despite the fact that it happens later in time. This behaviour is a feature of the system which is foreseen to be fixed in LS2 with the new quadrupole quench detection system.
In the following analysis one can see the typical shape of U_QS0 signals (up to LS2). Both reach 100 mV at the same time due to the synchronisation of the data. The non-quenching aperture typically has a spike some 40 ms earlier (due to QH firing) and a faster voltage rise (due to QH induced quench). The quenching aperture has a typical 5-6 V/s slope at nominal current.
*ANALYSIS*:
Determine aperture with a quenched magnet
1. Find a diode signal which is the first to reach 1 V
2. Take a circuit name (RQD/RQF) from the diode signal name
3. With the circuit name and the magnet name, get the aperture (INT/EXT)
4. With the aperture name, choose an appropriate U_QS0 signal and use for du_dt calculation
- if |U_QS0| $\geq$ 100 mV, then find the start time of a quench, t_start_quench, as the moment at which |U_QS0| is 10 mV greater than its initial value. Otherwise, the start time of a quench is set to 0 s
- Find U_QS0 value, u_start_quench, at the moment of quench start as u_start_quench = U_QS0(t=t_start_quench)
- The slope of the quench detection signals is calculated as du_dt = (u_ST_NQD0 - u_start_quench) / (t_st_nqd0 - t_start_quench)
*GRAPHS*:
t = 0 s corresponds to the PM timestamp of the QDS
Upper left (iQPS analog signals)
- the quench detection voltage on the left axis, U_QS0_INT, U_QS0_EXT
- the green box denotes an envelope of the +/- 100 mV quench detection threshold
- the orange box denotes an envelope of the rise of the quench signal from its start until reaching the threshold
Lower left (iQPS digital signals)
- the quench detection voltage on the left axis, ST_MAGNET_OK, ST_MAGNET_OK_INT, ST_NQD0_INT, ST_NQD0_EXT
Upper right (nQPS analog signals)
For PM signals (raw view)
- the diode voltages used by the nQPS crate for quench detection on the left axis, U_DIODE_RQx and U_REF_N1
Lower right (nQPS analog signals)
For PM signals (zoomed view)
- the diode voltages used by the nQPS crate for quench detection on the left axis, U_DIODE_RQx and U_REF_N1
- Check if the maximum resistance is above 50 uOhm. If yes, then raise a warning.
- Check if the maximum resistance is above 150 uOhm. If yes, then raise an alarm.
*GRAPHS*:
t = 0 s corresponds to the PM timestamp of the FGC
Upper PM (Input view)
- the main power converter current on the left axis, IAB.I_A
- quenched magnet voltage from two boards, U_DIODE_A, U_DIODE_B. The difference between both signals is the diode lead voltage.
- reference nQPS board voltage on the right axis, U_REF
- diplayed on the left only if a quench occured no later than 2 seconds after the FGC PM timestamp
Lower PM (Output view)
- the main power converter current on the left axis, IAB.I_A
- the calculated diode lead resistance on the right axis, R_DIODE_LEADS
- diplayed on the left only if a quench occured no later than 2 seconds after the FGC PM timestamp
Upper CALS (Input view)
- the main power converter current on the left axis, I_MEAS
- quenched magnet voltage from two boards is saved as a single signal, U_DIODE_RQx. The two signals are stored by means of value toggling between board A and board B. The difference between both sub-signals is the diode lead voltage.
Lower CALS (Output view)
- the main power converter current on the left axis, I_MEAS
- the calculated diode lead resistance on the right axis, R_DIODE_LEADS
rq_analysis.results_table[['Circuit Name','Position','Date (FGC)','Time (FGC)','I_Q_MQD','I_Q_MQF','R_DL_max_RQD','R_DL_max_RQF','I_RQD at R_DL_max_RQD','I_RQF at R_DL_max_RQF']]
```
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## 8.6. Plot of Voltage Feelers
*ANALYSIS*:
- Check if the voltage of a voltage feeler is equal to 0 V. If yes, then it means that the corresponding card is disabled.
- Check if the voltage of a voltage feeler is equal to -2000 V. If yes, then it means that the corresponding card is not communicating.
*GRAPHS* (one for each circuit):
- t = 0 s corresponds to the PM timestamp of the FGC
rq_analysis.results_table['FPA Reason']=get_expert_decision('Reason for FPA: ',['Heater provoked','QPS trip','Converter trip','EE spurious opening','Spurious heater firing','Busbar quench','Magnet quench','HTS current lead quench','RES current lead overvoltage','No quench','Unknown'])
rq_analysis.results_table['QDS trigger origin']=get_expert_decision('QDS trigger origin: ',['QPS','HTS current lead','RES current lead','Busbar','No quench'])
