Design, simulation and construction of the magnetic angle changer (MAC) device for electron spectrometers

Atomic collision experiments are important to investigate the structure of atomic and molecular systems, which have biological importance, and to test the accuracy of theoretical models. Electron spectrometers that are designed to make these kinds of experiments have angular limitations caused by the electron gun and Faraday Cup (FC). So, in these experiments, the angular limit usually is between 45°-135° and 125°-185°. The aim of this work is to remove any angular limitation by moving electrons to measurable angles by generated uniform magnetic field using Magnetic Angle Changer (MAC).Electron optical properties of MAC device are investigated using charged particle optics simulation program (CPO-3D) and the optimum geometry is determined for a MAC device.By investigating magnetic fields generated by two or three solenoids systems that satisfy the dipole and octupole conditions as a function of radial distance, the positions that deflected beam has a radial direction are calculated.It is found that MAC device has a focusing and dispersing effect on deflected electrons. Calculating deflection angles of the deflected electrons by MAC it is shown that MAC device causes further angular dispersion in electron trajectories.To evaluate the focusing and dispersion effects on electron trajectories, magnification ratios (?) corresponding to the values of current that apply to solenoids are calculated. ? parameter for a ideal deflection is determined. To improve the angular resolution, the optimum MAC geometry and solenoids current pairs are determined.To anticipate the production problems that can occur during manufacturing process, 3D modeling of the device is carried out using SolidWorks and AutoCAD programs. The components of MAC device are produced in the eCOL Workshop in Physics Department at Afyon Kocatepe University. After mounting and maintenance of the MAC device are finished, it is tested using a magnetometer.Since the MAC device will work inside the spectrometer continuously and eventually overheating, the maximum current limit and its performance are tested. After these test measurements, the MAC device is installed in the electron collision experimental setup to use for collision experiments.Cross section measurements for the helium autoionization resonance states were carried out in order to determine the deflection angle of the MAC device and to test the working performance of the system. It was found that the measurements taken at 30° with the MAC-ON case was in good agreement with that of taken at 48° with the MAC-OFF case. So, it is possible to take some measurements above 135°.Key Words: Electron-atom collisions, electron spectrometer, cross section, charged particle optics, the magnetic angle changer device (MAC), CPO-3D charged particle optics simulation programs