Characterizing a Solenoid Lens for an Electron Beam LINAC
Abstract
Electron beam technology is a growing field with applications in industrial processes, the medical field, and the physical sciences. To accelerate the electrons to the required energy, they are sent through a linear accelerator, which electric fields to accelerate the charges, and uses magnetic fields to channel them through the accelerator aperture. In order to effectively channel the electron beam in its transport, solenoid magnets are used. A solenoid is an asymmetric winding of insulated turns of copper foil strip, wound onto an insulating mandrel. When the current is driven through the winding, it produces an asymmetric distribution of field that threads through the aperture and returns it outside. The electrons are deflected in the gradient fields before and after the solenoid, and are alternately focused and defocused as they move along the axis. First a custom apparatus was constructed to measure the field flux and current pulse properties, were then analyzed to extract the central field strength for a given current and the spatial distribution of magnetic fields along the axis. Next a prior derivation of the magnetic field flux was adapted to fit the specifications of the solenoid, and compared to the data that was collected. A numerical simulation code, COMSOL, was used to simulate the magnetic field flux, and the results were compared to the measurements. Utilizing the principle of superposition, a beam line containing 14 identical solenoid lenses was simulated using the data gathered from one solenoid. The focal length of the solenoid was measured to be 1.31 m. Finally the path of an electron was simulated though the beam tube in order to establish the focal properties of the beam transport. Ensuring the exact output location of the electron from the input location is of paramount importance as it reduces the overall uncertainty in the final data.
Citation
Ratcliff, Christian T (2023). Characterizing a Solenoid Lens for an Electron Beam LINAC. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /200259.