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Spectrometer design for diagnostics in a wide range of energy at a linear accelerator

A spectrometer design has been presented for the electron linear accelerator at Institute for Research in Fundamental Sciences (IPM), Tehran, Iran. The energy of the linac is 8 MeV (upgradable to 11 MeV) with a maximum current of 10 mA. The design and construction of the machine is nearly finished and it is in the commissioning stage. The linac consists of a thermionic electron gun followed by a pre-buncher and some travelling wave tubes connected together via appropriate flanges. The commissioning process is foreseen in stages of different energies. At each stage an RF cavity will be appended in order to investigate its performance. Therefore, the energy diagnostics is demanded in a wide range—from 50 keV to 8 MeV . A spectrometer based on a dipole magnet, a movable view screen and a focusing solenoid is proposed for this purpose. The challenge is to keep the resolution in the wide range of measurements. This paper first describes the beam dynamics design of the spectrometer with the focus on the measurement resolution. Then the magnetic design of the dipole is presented in details. Two and three dimensional simulations have been carried out in order to optimize the dipole parameters such as the magnetic flux density, multipole components, and the integrated field quality. Finally, magnetic design features of the solenoid have been discussed.