The Solution of Dwell Time of Ion-beam Figuring Based on the Clean Algorithm

To solve the dwell time is the key step in the ion-beam figuring.Usually, the solution is derived through deconvolution.Such a solution is achieveable in principle.Nevertheless, when tiny(or even no)amount is to be polished away, the so-derived time becomes infinite.The deconvolution thus becomes ill-defined, so that it is difficult to determine the dwell time.The figuring cannot continue if such singular values appear.Based on the Clean algorithm, we discuss a new method to solve the dwell time in the ion-beam figuring of mirrors for astronomical telescopes.By fitting the data of mirror any precision of the solution of dwell time can be achieved with the new method.The method is also convenient for computer controlling in the figuring with ion beam.Certain simulation results demonstrate that the solutions of the new method can meet the practical need of such mirror figuring.