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Description This section contains information about the progress of the mounting design and our testing procedures.

See top for progress navigation.

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mounting design The mechanical oscillator will be mounted outside of the actual XRS detector housing but inside another dewer that will keep its temperature between 1 and 4 Kelvin. To fit inside the dewer, our entire setup must be about the size of a two inch cube.

Mounting Assembly
Mounting Assembly

The ultimate design of the mounting was chosen for several reasons. It is made from 1018 steel, the same material as the casing of the voice coil, so that we would not need to be concerned about our attachments being compromised due to the varying expansion or contraction of different materials at 4 Kelvin. The mounting setup holds the voice coil horizontally, mainly because a vertical mount would have been much more difficult for us to machine at Olin. The voice coil is held in place by a tightening screw that goes through the top portion of the holder. The accelerometer is off of the main mounting platform so that it could be oriented such that the axes of the voice coil movement and the acceleration detection would coincide. There is also space on the platform for attaching the transformer. We used belleville washers to ensure proper attachments at cold temperatures.

testing When initially looking into liquid helium testing (4 Kelvin), we spoke with Dr. Tom Pochapsky and Dr. Iu Yam Chan at Brandeis University about using their facilities. It soon became apparent that it would not be feasible to test at Brandeis due to issues of time and cost-effectiveness. We opted to test at Olin at both room temperature and liquid nitrogen temperatures (about 77 Kelvin).

Oscillator Setup after Cold Testing

The performance of the voice coil was tested at various frequencies at room temperature (296 K). Frequencies below 60 Hz had unclear amplitudes and wave forms. The observed waveforms and amplitudes both with and without the transformer improved at colder temperatures due to decreased resistance in the voice coil. Therefore, more force will be exerted at 4K than at the room-temperature tests. At low frequencies, the force produced in the trial by the voice coil with the transformer has noticeably lower amplitudes than the trial without the transformer. This variation in amplitude is due to properties of the transformer at room temperature, and this discrepancy disappeared when the assembly was subjected to cold testing.

Data at Room Temperature with and without Transformer
Note: All Volt, Amp, and ā€˜Gā€™ data values are in the chart are ā€œ+/-ā€.

Two resonances are apparent at approximately 500 Hz and 2500 Hz. It is believed that these are due to properties of the oscillator and testing setup. Natural resonances of the oscillator itself may differ.

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