Electrostatic lens for ThO molecules in the ACME III electron EDM search

Measurements of the electron electric dipole moment (eEDM) using atoms and molecules shed light on T-symmetry violating new physics beyond the Standard Model. The best upper limit on the eEDM was recently set by the ACME collaboration: |d_e|<1.1×10^-29 e·cm [1], using a cold beam of thorium monoxide (ThO) molecules. This result significantly constrains T-violating new physics in the 1~10 TeV range and above. The next generation of ACME aims to improve the sensitivity to d_e by another order of magnitude. A molecular lens will be used to focus, into the EDM measurement region, beams of ThO molecules that have been prepared in the highly polarizable Q state. We present several new features of our lens system: 1) a new, spatially compact rotational cooling scheme which is demonstrated to work with efficiency near its theoretical limit; 2) a STIRAP process to transfer molecules into and out of the Q state, demonstrated with 80% total efficiency [2]; and 3) an electrostatic hexapole lens operated at +/-23kV. Our analysis indicates the molecular lens system should improve the EDM signal by over one order of magnitude relative to an unfocused molecular beam. We present progress towards implementing the full system.