Design and Experimental Validation of High-Resolution Single-Shot Emittance Diagnostics for Heavy-Ion Beams

Abstract

A pepper-pot diagnostic device was developed to accurately and robustly retrieve particle distribution in horizontal and vertical phase spaces by single-shot emittance measurements. Two masks that differ in both composition and manufacturing method were fabricated: one made of phosphor bronze by an optical lithography process, and another made of stainless steel (SUS) by laser cutting. Scanning electron microscope measurements of the two masks revealed that the former is superior in terms of regularity and shape of the mask holes and is therefore more suitable to use. A new image-processing algorithm, namely the cluster noise removal method, was developed which improves the resolution of the phase-space distribution measurements over traditional methods. The device was tested in experiments with low-energy argon beams generated by an ECR ion source at KFE. Results show that the diagnostics can robustly and reliably retrieve the four-dimensional phase-space distribution of ion beams with a single-shot measurement.

Ion beam intensity and phase space measurement techniques for ion sources

“…In most cases, an important part of the phase space measurement is the data analysis and the removal of unidealities such as background noise, ghost images, and amplifier bias. Several studies on this subject have been made with different recommendations for data processing, [51][52][53] and even if the details vary, the basic recipe is the same. In here, an example of such a process is described for a 2D phase space measurement using an artificially generated dataset of 100 × 100 pixels with a bi-Gaussian phase space distribution with emittance εrms = 100 mm mrad, Gaussian noise with an rms amplitude of 1% of the peak beam signal, and a bias of 0.5%.…”

“…6(b) identifying the non-zero pixels to avoid contributions even from very weak looking ghost signals. Such ghost signals may have a strong contribution to the emittance value if they are far away from the main distribution and may require manual removal or the use of cluster analysis 53 for automation.…”