The trap dewar needs to be filled roughly every two weeks. It is important that it not run dry while the refrigerator is at base temperature. Otherwise, gasses from the trap will be allowed to boil out and contaminate the system, clogging the dilution unit, and requiring the 4K trap to be cleaned.
You can check the nitrogen level in the trap dewar by raising the trap out of the dewar briefly and looking for a line in the condensation, there will be no condensation below this line initially, but will quickly form as it pulls moisture out of the air.
To refill the trap dewar, simply connect the LN line from the liquid out phase of a storage dewar to the flange on top of the trap dewar.
Fill until liquid begins to overflow out of the vent. It will take roughly