X-Ray Maps

Once the films have been developed from a JACEE flight, the first step is to obtain a catalog of all the high energy events visible in the x-ray films. Here is a sample piece of developed x-ray film near the bottom of the chamber:

This is basically a top view at a single height in the chamber. The black spots are left by electron-photon cascades from high-energy cosmic ray events. If we examine another x-ray film, in this case about 5 mm above the previous one

we see a similar pattern. Though it is hard to tell, the blobs' positions have shifted based on their individual trajectories through the chamber, and the sizes have changed based on the event's energy and how old the interaction is. We can see the individual shifts easier if we superimpose the layers on top of each other:

It is from this coincidence on multiple layers that we determine which spots are due to an actual cosmic ray, and which are background noise.

Mapping Procedure

First, every blob is circled for each x-ray film in the chamber. This is done by two people to check for missed events.

Then, the spot locations are transferred to graph paper, coded by layer. In this "working map", the actual cosmic ray events are reconstructed by joining coincident spots on a line between three or more layers. Once the scanners are satisfied all events have been found, they are catalogued by number.

The last step is to digitize the coordinates of each catalogued event. The zenith and azimuth angle, as well as entry point into the chamber can be determined from this data. More importantly, though, a cleaned-up version of the map can be plotted to aid in the densitometry and tracing analysis.

E.O.