Sensitivity test of a blue-detuned dipole trap designed for parity non-conservation measurements in Fr

Abstract

A dynamic blue-detuned optical dipole trap with stable (87)Rb atoms produces a differential ac Stark shift of 18 Hz in the ground state hyperfine transition, and it preserves the ground state hyperfine superpositions for a long coherence time of 180 ms. The trapped atoms undergoing microwave Rabi oscillations are sensitive to a small signal, artificially generated with a second microwave source, phase locked to the first allowing a simple and effective method for determining signal-to-noise ratio limits through interference techniques. This provides an excellent means of calibrating sensitivity in experiments such as our ongoing Fr parity non-conservation measurement.

Atomic parity non-conservation: the francium anapole project of the FrPNC collaboration at TRIUMF

“…This makes the measurement most sensitive (linear section of the oscillation) to the change due to the interference with the nsd-PNC signal. The specific choice of n Rabi oscillations depends on the coherence time of the sample t c , but we have reached more than 100 ms in tests with Rb [40]. To illustrate the expected numbers, we consider the case of 209 Fr: if we have a field of 476 V/cm to drive the E1 transition and a coherent interaction time of 100 ms, then |A PNC / | = 0.01 rad/s and A PC / = (2n + 1) × 7.85 rad/s [38].…”

“…We extract the signal S (5) from the difference between the dashed and the dotted lines at a given time (in multiples or fractions of a period of the Rabi oscillation). Reference [40] describes in detail our successful test of this scheme to recover a very small artificial coherent signal with Rb atoms in an optical blue-detuned dipole trap. The continual application of both the A PNC and A PC driving fields throughout the Rabi process poses extra constraints on the performance of the trap and apparatus in general [38,41,42].…”

“…It is a large vacuum vessel with differential pumping and numerous windows and access ports. The development of the optical dipole trap and its characterization with Rb has shown that we can reach the sensitivity for the anapole measurement [40][41][42]. We are pursuing quasi-optic approaches for the microwave cavity and reached Q factors at the necessary frequencies of 46 GHz in excess of 3 × 10 4 .…”

The Francium facility at TRIUMF

“…[27] shows our recent sensitivity test for this technique with stable Rb atoms trapped in a bluedetuned dipole trap designed for parity nonconservation measurements in Fr.…”

Efficient, tightly-confined trapping of226Ra

“…Many such measurements, including beta-neutrino angular correlation and triple-correlation coefficients [1], neutral atom atomic parity violation, and permanent electric dipole moments (EDMs) [2,3] benefit when the species to be measured is confined in a tight, well-controlled, and environmentally-shielded trap. Optical dipole traps (ODTs) have been proposed as ideal traps for beta-decay asymmetry and neutral atom parity non-conservation experiments [4,5], as well as EDM searches [6], due to the compact volume, low spin relaxation rate, and high degree of control of external electric and magnetic fields possible in ODTs. However, due to the low abundance of the isotopes used, it is often important that any technique have low atom losses.…”