Solenoid Performances in Different Situations

Outline The request of double polarity arose a study to evaluate the effect of hysteresis on the magnetic field has been performed The request of running at lower field with respect to the design one arose the field has been calculated at different currents “Curiosity” about the possibility of running the magnet without the iron yoke is in the air the field of the bare solenoid has been calculated

Polarity Reversal The effect of hysteresis has been simulated changing the magnetisation curve In fact, this is a conservative assumption, since it is equivalent to complete magnetisation in all the iron yoke We expect complete magnetisation in a large part of the iron yoke but not necessarily everywhere The hysteresis curve has been designed on the basis of literature values for low carbon steel the net change is a proper translation to the left or the right of the magnetisation curve

Reference Field

After the Second Energisation

After Polarity Change

Summary This analysis of the effect of polarity change shows that a minor effect is expected in the central tracker region the change in B is few parts ‰ A larger effect is foreseen inside the iron yoke this is partially due to the assumptions I made to perform this calculations anyhow, this could affect the muon chambers tracking capability

Lower Field Operations The magnet behaviour has been evaluated at 20%, 40%, 60%, 80% of the nominal current For each configuration the uniformity and the radial field integral have been evaluated in the outer tracker region The effect of saturation in the downstream door is evident even if small The quality of the field is almost in the requirements for each configuration

20% of the Nominal Current

40% of the Nominal Current

60% of the Nominal Current

80% of the Nominal Current

Reference Field

Summary The magnet can be operated at every current, lower with respect to the design one The field quality is very similar at every current The little variations in the radial field integral distributions is probably due to the saturation in the downstream door

No Iron Solenoid

Summary of the Summaries The magnet can be operated in both polarities without significant effect can the field variation in the iron affect the muons tracking? to be investigated The magnet can be operated at every current lower than the design one the field quality is almost unaffected and the central field is reasonably linear with the current density The magnet cannot be operated without the iron the disperse field is too large the magnetic forces acting on the coils are too large