Chris Pelletier Frontiers Poster Abstract

Vibration Characteristics of a Simulated Diamond Wafer

Abstract

All atoms are made up of protons and neutrons, which are in turn comprised of quarks. The particles “gluing” the quarks together are known as gluons. The interaction of quarks and gluons is still not entirely understood, specifically how they are confined in the nucleus such that lone quarks are never seen. The nuclear physics group at the University of Connecticut is part of the GlueX Experiment, which hopes to probe directly the gluon bond and understand its mechanical properties. The probe used by GlueX is a high energy, polarized photon (particle of light) generated by a technique known as coherent bremsstrahlung . This technique involves radiation of photons as a high energy electron beam passes through a carefully oriented diamond wafer suspended on thin tungsten wires. Proper orientation ensures a high degree of polarization, which requires stable mounting of the diamond. The goal of my research is to investigate the mechanical properties of the mount and eliminate the possibility of vibration of the crystal.

To measure the vibration of the diamond crystal, a high speed imaging technique is used. The surface of the crystal is illuminated with a green laser. Reflected light is redirected to an imaging device, taking advantage of the long path length of the beam to amplify the motion. The beam spot entering the lens of the camera creates an artifact known as a “lens flare”. As the crystal rocks, the position of this artifact changes relative to a fixed reference point. This change is recorded using the camera’s high speed (1200 frames per second) video mode. The videos are processed by programs that identify and record the spot locations as it evolves in time. This information is used to determine the angular displacement of the crystal surface about both the x and y axis. Using techniques of Fourier Analysis, the frequencies of the vibration can also be determined from the position data.

The next step in this process is the study of how different suspension wire materials, as well as differing wire tensions, impact both the vibration amplitude and frequency. It has been proposed that a change in material from tungsten to carbon wire would significantly stiffen the system, reducing vibration. The ultimate goal is to develop a suspension system which has a vibration amplitude 100 times smaller than that in the current configuration. Much work still needs to be done in optimizing the diamond mounting system to decrease vibration to tolerable levels.