Ongeveer 22 uur geleden - Rijksuniversiteit Groningen (RUG) - Groningen
- you will design and perform laboratory experiments with marine micro-algal cultures - you will explore new techniques to measure carbon uptake and photosynth…
Project description The goal is to measure the fine structure constant α (α ≈ 1/137) as accurately as possible using ultracold helium-4 atoms. In an atom …
The goal is to measure the fine structure constant α (α ≈ 1/137) as accurately as possible using ultracold helium-4 atoms. In an atom interferometer experiment the recoil velocity that a helium atom gets after absorption of one photon at 1083 nm will be measured with high accuracy. From that measurement α can be determined using only fundamental constants that are known with even higher accuracy. Confrontation with a value for α calculated from electron g-factor measurements and Quantum Electrodynamics theory will provide one of the most stringent tests of the Standard Model of physics.
In the project you work with advanced laser technology in an ultrahigh vacuum environment to manipulate helium atoms that have been cooled to a temperature of 0.2 μK and trapped in an optical dipole trap (two crossed and focused laser beams). The experimental setup is for a large part already available, see Appl. Phys. B 122, 289 (2016), and uses a source of metastable helium (He*) atoms, collimated and slowed in a Zeeman slower by laser light. Atoms, trapped in a magneto-optical trap, are further cooled to Bose-Einstein condensation, transferred to an optical dipole trap and then launched for measurement of the recoil velocity using atom interferometry techniques. Light pulses will be applied to the ultracold atoms and the atomic wave packet, launched in the vertical direction with a momentum p, is split by Bragg scattering in two parts, moving with momentum p and p + 2nℏk (n is the number of photon recoils 2ℏk that is imparted to the atom). A second Bragg pulse creates two coherent wave packets which are accelerated in a moving optical lattice (= two counterpropagating laser beams with a small and time-varying frequency difference). A second pair of two Bragg pulses then recombines the wave packets closing the interferometer. The accelerated velocity is then very sensitively measured from the number of atoms in each output port of the atom interferometer, see Science 360, 191 (2018) for a similar experiment using Cs atoms. The He* atoms are detected with high time resolution on a microchannel plate detector allowing well-separated output ports of the interferometer.
One PhD student already works on the experimental setup and we also have a postdoc position on the same project. The project involves collaboration with local, national, and international scientists and the candidate is expected to publish his/her results in international peer-reviewed journals and present the work on national and international conferences.
You have an MSc in (technical) physics or equivalent. You enjoy experimental physics and you are interested in precision measurements and tests of fundamental physics. Experience with experimental cold atoms research is a big advantage.
Start is September 1, 2018, or earlier. The appointment will be initially for 1 year. After satisfactory evaluation of the initial appointment, it will be extended for a total duration of 4 years. You become a junior scientist at NWO with a contract for four years. You are supposed to have a thesis finished at the end of your four year term.
The salary will be in accordance with NWO regulations for academic personnel, and amounts € 2222,- gross per month in the first year up to € 2840,- in the fourth year (salary scale) based on a full-time employment. Teaching (up to 10% of your time) at the joint physics and astronomy education programme of Vrije Universiteit and University of Amsterdam is part of the appointment.
For additional information please contact dr. Wim Vassen