beam bunching

in secondary-ion mass spectrometry
https://doi.org/10.1351/goldbook.09393
Reduction in the spread of arrival times of an ion pulse by reduction in the speed of the leading ions or acceleration of those at the trailing edge of the pulse.
Note: This procedure can degrade the optimum focus of the ion beam, since different ions experience different fields.
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1837 (https://doi.org/10.1515/pac-2019-0404)