Control and setting of the Splitter magnet

Since this magnet will effect the exit beam trajectory toward the beam dump, this magnet can only be operated by MCC.

The nominal field setting for the Splitter is 1.546 Tesla. The corresponding power supply current setpoint is 842.83 A. The Splitter field is monitored by a fixed Hall probe glued to the wall of target vacuum chamber. Between the field range of 1.4 Tesla and 1.65 Tesla, the Splitter B (in Tesla)-I (in Ampere) curve can be expressed as a 6-order polynomial:

$$\begin{multline} B= 2.33427E-18\times I^6-6.12490E-15\times I^5+5.66717E-12\tim... ...I^3\\ +5.76159E-7\times I^2+1.87247E-3\times I+1.89685E-3 \notag \end{multline}$$

Before setting the splitter, the magnet must be degaussed. The degauss procedure is ramping up and down the magnet in two full cycles: 0A-1000A-0A-1000A-0A, THe ramping speed is 100A/min with 2 minute staying time at each minimum and maximum current. After that, the ramping up speed to the desired field value is 25A/min.

To set the magnet

1. Beam must be off during setting or any field change (even it may be small).
2. Call MCC to request on and setting up the Splitter magnet.
3. MCC will confirm the setting value in terms of current.
4. MCC will set the magnet following the specified ramping procedure.
5. MCC will call back to confirm the field reading by hall probe monitored by Hall C.
6. Small current correction (directly increase or decrease) can be done if the. field is not set to the desired value within an accuracy of $10^{-4}$.