Verification and experimental validation of neutral atom beam source produced by L-PBF

TL;DR

The paper addresses generating a calcium atomic beam for trapped-ion experiments while minimizing trap heating and maximizing proximity by using Laser Powder Bed Fusion (L-PBF) to fabricate a compact, vacuum-compatible oven. It combines SEM/EDS surface/composition analysis, finite-element thermal modeling, and atomic fluorescence imaging to validate both the mechanical and functional performance, including beam delivery to the trap center. Key findings include a crack density of approximately $7 imes10^{-3}$ μm$^{-2}$ at 200×, operation at $T$ near $680$ K with careful current ramps, and direct confirmation of beam delivery via Doppler-broadened fluorescence signals. The work demonstrates that additive manufacturing is a viable and practical approach for producing integrated neutral-atom sources compatible with ultra-high vacuum and precision quantum experiments.

Abstract

We report validation tests of a calcium atomic beam source manufactured by Laser Powder Bed Fusion (L-PBF). We quantitatively evaluated the surface quality and elemental composition of the printed part and defined reference parameters for reliable operation in ultra-high vacuum. Safe operating conditions of the atomic oven were derived from simulations and experimental measurements. The ability of the device to deliver an atomic beam to the main experimental region, the electron/ion trap, was verified via atomic fluorescence imaging.

Figures (5)

• Figure 1: Illustration of the 3D-printed atomic oven assembly and its placement. (i) The view at uncovered oven assembly showing the oven tube (OT) fixed by a pair of metallic screws (MS) and supported by ceramic screws (CS). Copper ring terminals (OE) providing the electrical connection are isolated from the rest by ceramic washers (CW). (ii) Front view with the stainless-steel heat shield (HS) and orifice in place. (iii) Isometric view depicting the installation of the oven and the trap on the bottom DN150CF blank flange of the vacuum chamber. The x-axis of the reference frame used for the FEM simulation extends from the centre of the atomic oven aperture (O) to the centre of the coaxial trap. LW (Left Wall) and RW (Right Wall) denote the inner surfaces of the left and right walls, respectively. (iv) Top view into the vacuum chamber illustrating the orientation of lasers inducing fluorescence of evaporated atoms. The camera for recording the fluorescence is either positioned above the viewport situated on the top flange to face the oven aperture or in front of viewport A.
• Figure 2: SEM images of surface of print-out and their analyses. (a) and (b) show micrometre and millimetre field views, respectively, coupled with binarized images of cracks. The analyzed pictures had dimensions of $663 \times 666$ pixels.
• Figure 3: EDS spectrum of the 3D-printed piece (upper panel), illustrating the elemental composition. The lower panel presents a comparison of the composition percentages between the 3D-printed alloy and stainless steel 316L.
• Figure 4: Computational and experimental analysis of thermal behaviour of the oven setup. (a) Computed heat distribution map with heat shield at the heating power of 17.8 W for $t_{\text{oh}}=30$ min. (b) Calculated temperature profile as a function of distance for different heating durations at the same oven power of 17.8 W, referenced to the chamber maintained at the laboratory temperature $T_{\text{lab}} \approx \qty{293}{K}$. Here, $x_\text{a}$ ($x_\text{b}$) denotes the position of the assembly backside (heat shield front). (c) Oven temperature as a function of current for different holding times ($t_\text{hd} = 1, 4, 7, 10 \,\text{min}$). Experimental data points are shown as dots, while smooth spline curves represent fitted trends. The upper axis indicates the corresponding electrical power, mapped directly to the current values. The experiments were performed at the pressures on the order of E-6Pa.
• Figure 5: Images taken during fluorescence imaging of Ca atom beam. (a) View at the oven aperture through a viewport at top flange. The laser beam partially strikes the heat shield, producing stray light (SL) enclosed within the dashed circular region. (b) The same view as (a) but with atomic fluorescence (AF) spot, clearly confined to the atomic beam region. The spatial distribution and background intensity of the SL remain essentially unchanged between the two images. (c) Atomic fluorescence image near the trap aperture, visible as an O-shaped structure. For orientation, the image was superimposed with one taken at the same angle under ambient lighting.