Maarten Mooij, PhD at Nikhef, will defend his thesis Tuesday 3 June 2025 at 13.45 at th Vrije Universiteit Amsterdam.
“A cryogenic buffer gas beam source of BaF molecules”
The search for the electric dipole moment of the electron (eEDM) is a direct test of fundamental theories beyond the Standard Model. The NL-eEDM collaboration aims to perform a competitive measurement of the eEDM with a Stark decelerated and laser cooled beam of barium monofluoride (BaF) molecules.
My thesis “A cryogenic buffer gas beam source of BaF molecules” describes the design, construction, testing and understanding of the cryogenic buffer gas beam source of BaF molecules. Within the source, molecules are formed amidst cryogenic neon buffer gas, which makes the molecules cold and slow and allowing an intense beam to be efficiently formed.
The brightness, density and rotational temperature of the beam are measured with absorption and laser-induced fluorescence detection. A method is developed to directly measure the phase-space distribution – the number of molecules per position and velocity interval – in the longitudinal direction of the molecular beam, which provides the velocity and position of the BaF molecules uncorrelated from each other.
This method is used to determine the influence of various source parameters. Besides the expected dependence on temperature and pressure, the forward velocity of the molecules is strongly correlated with the time at which they exit the cell, revealing the dynamics of the gas inside the cell. The source produces about 1.2×1011 BaF molecules per steradian per pulse in a single rotational level with a forward velocity of 207 m/s.
“A cryogenic buffer gas beam source of BaF molecules” (pdf)
The PhD defense will take place at the main building of the Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081 HV, Amsterdam
More information and a link to the livestream on the website of the Vrije Universiteit Amsterdam.
Supervisors: prof. dr. H.L. Bethlem and prof. dr. W.M.G. Ubachs
Contact: Maarten Mooij