TPC Memo

By modifying the TPC wire chamber we were able to we were able to both make a more uniform potential field and have the E-field tracks be more uniform. This was accomplished by adding two wires to the top corners and one wire to the bottom corners, for a total of 6 wires. However, since these wires will wrap around the wire chamber, the two top corners are utilizing the same two wires and likewise the bottom corners are utilizing the same wire. So in essence we are really only adding three additional wires and tweaking the potential of one more wire. In order to do this the top wire of the original wire chamber's voltage was changed slightly higher than normal and the two added wires are placed at higher potential also. The top wire, A, as we will call it has the potential 34K, this was changed from the potential of 32K that it originally had. The first added wire, X, is another step up from the front row of wires and in the plane with the high-potential wires, its potential is at 42K. The second wire added was inserted directly halfway between X and the end of the high-potential plane. It is sitting at the potential of 38K. The rest of the wires are left the same, the second wire down, B, is at 28K and the voltages decrease linearly from there with no change from the original design. (See Fig 1 and Fig 2) By looking at the contour plots one can see that the new contours are much improved over that of the original cell.
An additional improvement is that of the E-field tracks. In Fig 3 one can see that the E-field throughout the cell is quite uniform. In this plot we are looking at 5 different tracks with varying values of Z. The first, Z=9.2 is track just outside of the cell while the second Z=10 is just inside of the cell. The third, Z=24.35 is located in the middle of the chamber while the fourth, Z=39, and fifth, Z=39.6 are just inside and just outside the back of the chamber, respectively. Finally, Fig 4 compares the tracks from the original cell and the modified cell on the outside, Z-9.2. We can see that the original track varies extensively from the middle track while the modified track is quite uniform.