Design of a Lamb-shift polarimeter for pulsed intense polarized H+/D+ ion sources

摘要: An intense spin polarized H^+/D^+ ion source (SPIS) based on the principle of atomic beam source and resonant plasma ionizer is under development at Institute of Modern Physics (IMP, CAS) for the future Electron-ion collider in China (EicC). In order to measure the polarization of the pulsed H^+/D^+ beam extracted from the SPIS at an energy of 25 keV, a Lamb-shift polarimeter (LSP) has been designed. Compared with the polarization measurement utilizing nuclear reactions that demands polarized ion beam accelerated to the MeV level, LSP operated at a low energy is evidently more convenient. Moreover, thanks to its principle, LSP can function normally even in the presence of a mixed H_2^+ component in the extracted polarized D^+ beam, which is inevitable for the polarized ion source utilizing resonant plasma ionizer. An ion beam transport system aiming at modifying the beam spin orientation and decelerating the beam from 25 keV to 2.5 keV is incorporated into the LSP, which enables the LSP to be used directly at downstream of the SPIS. In this work, all of the involved critical physical processes and components of the LSP have been modeled, analyzed and designed carefully to ensure high efficiency at each stage of its operation. Even for a low duty factor pulsed ion beam, the LSP is capable of measuring the polarization with a precision of 1% in a few seconds.