Ph.D. Thesis - Physics
Ph.D. Thesis - Physics
Ph.D. Thesis - Physics
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(a)<br />
Lattice Trap Schematic<br />
TOP PLATE<br />
(GND or +DC)<br />
RF PLATE<br />
1.4 mm<br />
1.5 cm<br />
BOTTOM PLATE (GND)<br />
(b)<br />
Figure 5-10: Experimental setup for the macroion experiment. (a) 3-D schematic of lattice<br />
trap setup. (b) The lattice rf plate, as mounted for the microsphere experiment. The hole<br />
diameter is 1.14 mm and the hole spacing is 1.67 mm. The trap is supported by a printed<br />
circuit board.<br />
5.5 Measuring interactions between macroscopic ions<br />
Another important test of the applicability of this lattice design to quantum simulations<br />
is the strength of interactions between ions in different wells. This section deals with the<br />
measurement of repulsion between charged particles in different wells of a lattice ion trap.<br />
For this work, we used aminopolystyrene microspheres with diameter 0.44 µm (Spherotech<br />
Part No. AP-05-10). This is because the charge to mass ratio of the strontium ions is<br />
unsuitable for this measurement in a lattice of this (d = 1.64 mm) spacing. The charge-to-<br />
mass ratio Q/m of macroions used in the experiment leads to observable repulsions between<br />
ions in neighboring wells, although it takes on a relatively wide range of values due to the fact<br />
that Q/m is not the same for every macroion. The use of macroions is also experimentally<br />
much less demanding than atomic ion trapping, because UHV pressures and laser cooling<br />
are not required. In fact, ions can be trapped in atmospheric pressure more easily than<br />
under vacuum, since air damping of ion motion increases the range of parameters suitable<br />
for stable trapping [PLB + 06, WO91, Pea06].<br />
While the measurements of interaction strengths between macroions does not translate<br />
directly into interaction strengths expected between atomic ions, the analysis methods in-<br />
volved, particularly with regard to screening effects, is likely to share common points. The<br />
measurements made in this section were conducted by Tongyan Lin and Kenneth Brown.<br />
The author was involved, along with them, in the analysis of the data.<br />
Fig. 5-11 is a diagram of the experiment, which is an adaptation of the experiment in<br />
Ref. [PLB + 06]. The main components of our apparatus are the electrospray system and the<br />
4-rod loading trap. To load the ions in the lattice trap, we perform a modification of the<br />
method in [CPK + 02], skipping the washing step. We prepared a buffer solution of 5 mL<br />
pure acetic acid, 26 mL 1M NaOH, and 5% suspension microsphere solution. The buffer<br />
solution reduces spread in macroion charge. We sonicated the solution for 10 minutes to<br />
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