Magnetic Trapping of Hydrogen after Multistage Zeeman Deceleration

We report the first experimental realization of magnetic trapping of a sample of cold radicals following multistage Zeeman deceleration of a pulsed supersonic beam. H atoms seeded in a supersonic expansion of Kr have been decelerated from an initial velocity of $520\mathrm{m}/\mathrm{s}$ to $100\mathrm{m}/\mathrm{s}$ in a 12-stage Zeeman decelerator and loaded into a magnetic quadrupole trap by rapidly switching the fields of the trap solenoids.

Figure 1

(a) Schematic diagram of the quadrupole trap. The H atom beam propagates from left to right and after exiting the 12-stage decelerator enters the two solenoids (labeled A and B) which form the trap. Atoms in the trap volume are detected by $\mathrm{VUV}+\mathrm{UV}$ two-photon excitation to Rydberg states followed by pulsed electric field ionization. ${\mathrm{H}}^{+}$ ions are then extracted through solenoid B to the MCP detector (not pictured). (b) Distribution of magnetic field strength in the plane containing the axis of symmetry of the quadrupole trap for currents of 200 A applied to each solenoid. The contours of constant magnetic field strength are drawn in steps of 0.1 T.

Figure 2

Schematic diagram outlining the switching sequence employed when loading the quadrupole trap. The arrows indicate the direction of the magnetic field on axis at the center of the solenoid.

Figure 3

TOF profiles of the H atom beam (a) with the decelerator off, (b) with the 12-stage decelerator on but with the trap solenoids off, (c) after deceleration with the decelerator and the first trap solenoid. (d) Detection of trapped atoms after switching on the trap. (e) Simulation of the experimental results. The inset is an expanded view of part of trace (d) along with the signal measured when the trap is switched off at 1.98 ms (dashed curve).