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Direct loading of a Sr magneto-optical trap from a thermal atomic beam

Naohiro Okamoto, Takumi Sato, Takatoshi Aoki, Yoshio Torii

TL;DR

The paper demonstrates direct loading of a strontium MOT from a thermal atomic beam in a single-chamber ultra-high-vacuum without a Zeeman slower, slowing laser, 2D MOT, or differential pumping. By thermally managing a compact Sr oven at $395\,^{\circ}\mathrm{C}$, they achieve up to $10^{7}$ ${}^{88}\mathrm{Sr}$ atoms with a loading rate of $10^{7}\ \mathrm{atoms\,s^{-1}}$ while maintaining a background pressure near $1\times10^{-9}$ Torr, and observe a MOT lifetime on the order of a few seconds dominated by collisions and two-body losses. The results are analyzed with a rate-equation framework showing the transition between background-gas- and two-body-limited regimes, and they confirm that the single-chamber design can support field- and space-deployable optical lattice clocks. This simple, compact loading scheme reduces SWaP while preserving high atom numbers, making it attractive for portable quantum sensors and clock systems.

Abstract

We demonstrate direct loading of a strontium (Sr) magneto-optical trap (MOT) from a thermal atomic beam in a single-chamber vacuum system. The MOT operates without a Zeeman slower, a slowing laser, a two-dimensional MOT, or differential pumping, while the entire system is maintained in the ultra-high-vacuum regime by a single ion pump. At an oven temperature of $395\,\mathrm{{}^\circ C}$, the MOT captures up to $10^{7}$ ${}^{88}\mathrm{Sr}$ atoms with a loading rate of $10^{7}\,\mathrm{atoms\,s^{-1}}$, while sustaining a background gas pressure of $1 \times 10^{-9} \,\mathrm{Torr}$. At this oven temperature, the MOT lifetime limited by collisions with background gas is $\sim 5 \,\mathrm{s}$, with the atom number primarily constrained by light-assisted two-body collisions. Eliminating differential pumping and precooling stages significantly reduces the system's size, weight, and power requirements, providing a robust and practical platform for field-deployable and spaceborne optical lattice clocks, as well as a variety of other applications requiring compact ultracold atom sources.

Direct loading of a Sr magneto-optical trap from a thermal atomic beam

TL;DR

The paper demonstrates direct loading of a strontium MOT from a thermal atomic beam in a single-chamber ultra-high-vacuum without a Zeeman slower, slowing laser, 2D MOT, or differential pumping. By thermally managing a compact Sr oven at , they achieve up to atoms with a loading rate of while maintaining a background pressure near Torr, and observe a MOT lifetime on the order of a few seconds dominated by collisions and two-body losses. The results are analyzed with a rate-equation framework showing the transition between background-gas- and two-body-limited regimes, and they confirm that the single-chamber design can support field- and space-deployable optical lattice clocks. This simple, compact loading scheme reduces SWaP while preserving high atom numbers, making it attractive for portable quantum sensors and clock systems.

Abstract

We demonstrate direct loading of a strontium (Sr) magneto-optical trap (MOT) from a thermal atomic beam in a single-chamber vacuum system. The MOT operates without a Zeeman slower, a slowing laser, a two-dimensional MOT, or differential pumping, while the entire system is maintained in the ultra-high-vacuum regime by a single ion pump. At an oven temperature of , the MOT captures up to atoms with a loading rate of , while sustaining a background gas pressure of . At this oven temperature, the MOT lifetime limited by collisions with background gas is , with the atom number primarily constrained by light-assisted two-body collisions. Eliminating differential pumping and precooling stages significantly reduces the system's size, weight, and power requirements, providing a robust and practical platform for field-deployable and spaceborne optical lattice clocks, as well as a variety of other applications requiring compact ultracold atom sources.

Paper Structure

This paper contains 10 sections, 22 equations, 9 figures.

Table of Contents

  1. Introduction
  2. Theory
  3. Experimental setup
  4. Results and Discussion
  5. Conclusion
  6. acknowledgments
  7. Dependence of the loss rate of trapped atoms on background gas pressure
  8. Atomic beam flux
  9. Loading rate of atoms into the MOT
  10. Dependence of the trapped atom number on the loading rate

Figures (9)

  • Figure 1: Theoretical curve of the MOT loading rate calculated for our vacuum system configuration and for various capture velocities.
  • Figure 2: (a) Schematic illustration of the oven. Alumina washers and bushes are used to thermally isolate the oven from the vacuum system. (b) Picture of the capillary tubes. (c) Picture of the oven with the stainless-steel reflector removed.
  • Figure 3: (a) Oven temperature as a function of power consumption. (b) Vacuum pressure as a function of oven temperature.
  • Figure 4: (a) Experimental setup for measuring the atomic beam flux and the number of trapped atoms. (b) Observed optical density (black dots) along the direction transverse to the atomic beam propagation at an oven temperature of $455\,\mathrm{{}^\circ C}$. The fit function (red line) is the sum of six Voigt functions [Eq. \ref{['eq:OD_element']}]. Each dashed line represents the contribution of the three bosonic isotopes $^{84}$Sr (0.56%), $^{86}$Sr (9.86%), and $^{88}$Sr (82.58%), and the three hyperfine components of the fermionic $^{87}$Sr (7.00% in natural abundance).
  • Figure 5: Measured atomic beam intensity as a function of the oven temperature, in comparison with the theoretical curve (Knudsen regime).
  • ...and 4 more figures