Troubleshooting

This chapter ties common symptoms to the v0.1 operating procedures. Use it alongside Operation Manual, Control System, and Maintenance.

MOE stage issues

Symptom	Likely cause	Corrective action (reference)
Fe sump fails to accumulate	Cathodic overpotential too high or insufficient settling time	Return to the Fe window parameters (low current density ~0.2–0.4 A cm⁻²) and hold until OES Fe lines stabilize. Allow extra dwell before tapping.
Silicon alloying with iron	Fe sump temperature too high or Si stage ramp too aggressive	Lower sump temperature, reduce potential step to 10 %, and pause feeding until LIBS/OES indicates separation (Section 4.3).
Excessive bubbling or spatter	Rapid feed rate or trapped gas pathways	Reduce feed rate, verify gas ports are clear, and ensure the argon blanket is within the 50–150 mbar range.

Symptom

Likely cause

Corrective action (reference)

Fe sump fails to accumulate

Cathodic overpotential too high or insufficient settling time

Return to the Fe window parameters (low current density ~0.2–0.4 A cm⁻²) and hold until OES Fe lines stabilize. Allow extra dwell before tapping.

Silicon alloying with iron

Fe sump temperature too high or Si stage ramp too aggressive

Lower sump temperature, reduce potential step to 10 %, and pause feeding until LIBS/OES indicates separation (Section 4.3).

Excessive bubbling or spatter

Rapid feed rate or trapped gas pathways

Reduce feed rate, verify gas ports are clear, and ensure the argon blanket is within the 50–150 mbar range.

Symptom	Likely cause	Corrective action
RGA shows rising phosphorous despite hold	Insufficient temperature or pressure not reaching ≤10 Pa	Increase refining temperature toward 1800 °C and verify vacuum integrity using the dry-run leak criteria.
RGA spike at m/z ~44 (SiO)	Over-evaporation or cold-trap warming	Tighten cold-trap cooling, lower refining temperature slightly, and inspect trap fill level between runs (Section 4.4).

Symptom

Likely cause

Corrective action

RGA shows rising phosphorous despite hold

Insufficient temperature or pressure not reaching ≤10 Pa

Increase refining temperature toward 1800 °C and verify vacuum integrity using the dry-run leak criteria.

RGA spike at m/z ~44 (SiO)

Over-evaporation or cold-trap warming

Tighten cold-trap cooling, lower refining temperature slightly, and inspect trap fill level between runs (Section 4.4).

Symptom	Likely cause	Corrective action
Impurity bands through ingot	Cooling rate too fast or directional cooling disrupted	Reset casting ramp to 1–5 K min⁻¹ from bottom to top. Confirm mold coating is intact (Section 4.5).
Surface oxidation on poured ingot	Transfer exposure to air	Use a covered transfer crucible and minimize transit time from refining pot to mold.

Symptom

Likely cause

Corrective action

Impurity bands through ingot

Cooling rate too fast or directional cooling disrupted

Reset casting ramp to 1–5 K min⁻¹ from bottom to top. Confirm mold coating is intact (Section 4.5).

Surface oxidation on poured ingot

Transfer exposure to air

Use a covered transfer crucible and minimize transit time from refining pot to mold.

Pyrometers drifting: Recalibrate against reference per the testing chapter and check purge gas cleanliness.
LIBS/OES noise: Inspect optical windows for condensate buildup and realign fibers after cleaning.
Vacuum gauge disagreement: Re-zero Pirani and capacitance manometer, confirm gauge placement is per the utilities chapter.

Document troubleshooting steps alongside batch records so recurring patterns can be addressed during scheduled maintenance.