BAF Thin Septum Magnet at D3

2D-Simulation

The transient magnetic field in the D3 septum magnet was studied by W. Meng using Opera2d/Tr (Low Frequency Transient). The magnet model used the following parameters:

Back Coil: Material Cu, Electrical Resistivity 1.7 mW-cm

I = 1500 A

Septum Coil:

Part I – Material Cu; Electrical Resistivity 1.7 mW-cm;

I = 1452 A;

Part II – Material Monel 400; Electrical Resistivity 58 mW-cm;

I = 48 A.

Yoke Steel: Material Plain Carbon 1020, Electrical Resistivity 10 mW-cm

Driving Function Rise Time: 0.05 Second.

Geometry: See magnet model.

Snapshots of the flux pattern and eddy current distribution at 0.03 seconds after the start of the ramp, i.e. at 60% of full field, show that the return yoke is much thicker than required. The thickness of the yoke is driven by the need to mount the brackets that hold the septum coil.

The field in the septum magnet and in the Booster beam pipe during a typical cycle with a 0.05 sec rise time, a 0.5 sec flattop and a 0.05 sec fall time at various (x,y) positions (see magnet model) is shown here (this file has 7 pages). With BAF running, the Booster beam center is 37mm from the septum current sheet, i.e. at (x,y)=(6.1,0) in the magnet model coordinate system.

Magnet measurements

The magnetic field measurements done at a current of 1498A gave a field of about 725 Gauss on the flattop, at (x,y)»(1,0) in the 2D-simulation coordinate system. This is in good agreement with the simulations. The current readout is distorted due to signal filtering. Since the field quality of this magnet is not critical, the quality of the data was regarded satisfactory.