Spark Chamber Setup

One the major components in the AESOP instrument is the spark chamber. The AESOP chambers contain 5 parallel aluminum plates connected, in alternate order, to ground and a high voltage pulser. The medium between plates is a slow moving noble gas mixture of neon and helium. As a charged particle transverses a chamber it leaves behind an ion trail in the gas. If the scintillator detectors, mounted above and below the chamber, detect coincidence light pulses from the resulting ionization track, a 10,000 volt pulser is triggered. In the presence of a high electric field, the ions in the gas are accelerated toward the plate surface producing more ions with each ion-atom collision. These multiple collisions form an ion cascade which ultimately results in a high voltage breakdown very near the original ion trail. This breakdown in each gap produces a bright red verticle spark which is digitized and recorded using a linear CCD camera. As shown below, the AESOP chambers have two mirrors mounted in the back walls resulting in two additional reflected images (1 direct and 2 reflections). The spark position in each gap can then be determined from triangulation of the direct and reflected images.


AESOP Spark Chamber Drawing  

Shown below are photographs of 3 different particle events in one of the AESOP spark chambers. These photos were taken in the Bartol Research Institute laboratory using a standard analog camera with a manual shutter control. The CCD camera platform was removed from the chamber to provide a clear viewing perspective of the sparks. Roughly 80% of ground level charged particles are muons while the remaining components are electrons, protons or pions.