Development of a Penning Trap Demonstration Apparatus

Penning traps, consisting of a strong uniform magnetic field, and a quadrupole electric field, have been used since the 1950's to trap charged particles and ions and measure their properties. These devices are used in mass spectrometry with applications in diverse fields such as atomic and nuclear physics, astrophysics, and analytical chemistry. While destructive measurement techniques are commonly used at nuclear Penning trap facilities that deal with short-lived isotopes, non-destructive techniques are used in Fourier Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometry and in high-precision mass measurements of long-lived and stable isotopes. These techniques determine the frequency of ions via Fourier analysis of the image charges they induce in the trap electrodes during their cyclotron orbit in the Penning trap. We have developed a miniature Penning trap that utilizes as 0.55 T permanent Nd magnet. This device can be used as a demonstration apparatus in an advanced lab class. Ions are created inside the trap via electron impact ionization of background gas and the image charge signal is detected on the trap electrodes, amplified and digitized for further analysis. In addition, to demonstrate the principles of image charge detection and to provide a simple tool for investigating Fourier analysis, we have developed an FT-ICR analog apparatus. This device uses a microphone moving in a circular orbit to represent the charged ion, and a speaker to represent the image charge detection electrode. LabView software is used for data acquisition and analysis giving students access to Fourier analysis techniques.