The configuration of superconducting coils in mark II Ioffe trap is shown. Four racetrack shaped coils form a radial quadrupole. Two sets of solenoids with the same current sense pinch off the magnetic trap along the axis.
(a) Magnetic field magnitude on a line passing through a racetrack coil of mark II trap. The field at the racetrack is the maximum field exerted on the coil, and determines the maximum current it can carry. The racetrack coil extends from . (b) Magnetic field magnitude on a line passing along the wall of mark II trap. This field determines the trap depth.
On the left: a cross-section sketch of mark I magnet assembly, showing the titanium form (A), aluminum compression pieces (B), and Kevlar fiber (C). On the right: a cross-section sketch of mark II magnet assembly, showing the titanium form (D), two kinds of titanium compression pieces [(E) and (F)] and aluminum compression tube (G).
Schematic design of a racetrack coil in mark II trap.
Schematics of the active quench protection system for both mark II and III traps. During normal operation, the run SCR, , is conducting while the dump SCR, , is nonconducting. After a quench is detected, the run SCR is disabled and current flows through the dump resistor, . The circuit is based on a design given in Ref. 20.
The training behavior of the four quadrupole coils used to build mark II magnetic trap.
Fraction of mark II trap’s stored energy dissipated in the external dump resistor.
The training profile of mark II trap. Based upon this training curve, a maximum operating current of was selected.
A cross-section view of the KEK quadrupole magnet (Ref. 22).
The top view and cross section view of the solenoid form design for mark III trap. The arrows indicate the direction of the magnetic field from the KEK magnet.
The graph shows the measured quench protection efficiency at various currents of the KEK quadrupole magnet. On average, the protection circuit has an efficiency of 95%.
Design and operation parameters of the Ioffe traps (the operating parameters of mark III trap are design values, initial test values can be found in Table II).
Parameters of two quenches observed during mark III trap test.
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