Experiments to Control Atom Number and Phase-Space Density in ...
Experiments to Control Atom Number and Phase-Space Density in ...
Experiments to Control Atom Number and Phase-Space Density in ...
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heat s<strong>in</strong>k allow for the connection of current connec<strong>to</strong>rs <strong>to</strong> the coil without establish<strong>in</strong>g<br />
an electrical connection between the current supply <strong>and</strong> the heat s<strong>in</strong>k.<br />
(a) (b)<br />
Figure 7.20: Feshbach coil heat s<strong>in</strong>k. (a) A small gap <strong>in</strong> the heat s<strong>in</strong>k reduces eddy<br />
currents. The <strong>in</strong>side is hollow so that water can remove resistive heat from the coils. (b)<br />
The current connec<strong>to</strong>rs are attached <strong>to</strong> the Feshbach coil (orange), without establish<strong>in</strong>g<br />
an electric contact between the current supply <strong>and</strong> the heat sh<strong>in</strong>k.<br />
The current connec<strong>to</strong>rs are soldered <strong>to</strong> the coil with Indium solder (Indium Cor-<br />
poration of America, alloy 58Bi 42Sn). This epoxy has a lower electrical resistance than<br />
regular solder <strong>and</strong> a lower melt<strong>in</strong>g po<strong>in</strong>t (138 ◦ C). Both the coil <strong>and</strong> the copper current<br />
connec<strong>to</strong>rs have a large volume of copper that need <strong>to</strong> be heated, <strong>and</strong> it is impossible <strong>to</strong><br />
directly solder the current connec<strong>to</strong>r <strong>to</strong> the coil. St<strong>and</strong>ard solder<strong>in</strong>g irons are not able <strong>to</strong><br />
produce enough heat, even with the reduced melt<strong>in</strong>g po<strong>in</strong>t of the solder. The Feshbach<br />
coil with the heat s<strong>in</strong>k connected is therefore heated <strong>to</strong> 130 ◦ C us<strong>in</strong>g heater tape. The<br />
current connec<strong>to</strong>rs are heated separately <strong>in</strong> the oven typically used for cur<strong>in</strong>g of epoxy.<br />
With both coil <strong>and</strong> connec<strong>to</strong>r close <strong>to</strong> the melt<strong>in</strong>g po<strong>in</strong>t temperature of the solder the<br />
electrical connection can be made with a st<strong>and</strong>ard solder<strong>in</strong>g iron. Before attach<strong>in</strong>g the<br />
two pieces <strong>to</strong>gether, diamond filled epoxy is applied <strong>to</strong> the <strong>in</strong>dentation of the heat s<strong>in</strong>k.<br />
This stabilizes the current connec<strong>to</strong>r <strong>to</strong> the heat s<strong>in</strong>k <strong>and</strong> provides a large resistivity<br />
between the two parts. To further support the weight of the current connec<strong>to</strong>rs, epoxy<br />
putty (Loctite, Fixmaster underwater repair epoxy) is used <strong>to</strong> create another mechanical<br />
support between the current connec<strong>to</strong>rs <strong>and</strong> the heat s<strong>in</strong>k.<br />
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