MESA+ Institute for Nanotechnology

Decay and Snapback in Superconducting Accelerator Magnets

Strict control of temporal and spatial magnetic field uniformity is essential for maintaining particle beams in accelerators. In practice, magnets for high field superconducting particle accelerators, such as the Large Hadron Collider, exhibit “decay” of the magnetic field and its components during long periods of constant current. This “decay” is particularly important during the injection of particles into the machine. As soon as the particles are accelerated and the current in the magnets is ramped up, the field rapidly recovers from the “decay”. This phenomenon is generally referred to as “snapback”. Both “decay” and “snapback” heavily influence the beam in the machine and have to be compensated precisely in order to avoid particle loss or even a complete loss of the beam.

This thesis presents the results of an in-depth study of both effects and describes a novel detector suitable for detailed analysis of the effects in magnets. In contrast to other systems, the detector has sufficient time resolution during “snapback” and can be used to conduct systematic measurements on accelerator magnets or compensate “decay” and “snapback” in the machine online.