Large Cell Scope Pictures, Part II

1
Large Cell Scope Pictures, Part II
This is a follow-up on Richards measurement of
large cell signals. In addition to his test I
added a small, 7 cm z-strip under the LST. This
z-strip is made out of copper tape, about 7x15
cm2. It is connected via a BNC connector and a
50 Ohm coax cable to a scope (50 Ohm
termination) If have updated the two drawings
below taken from Richards presentation. Ground
plane above cathode and below tube (see picture
below) Please note that there is an asymmetry in
the chamber endcap the HV pins are not located
at the symmetry line but closer the the bottom of
the tube. According to the drawings of the large
cell tubes that are available on the web, this is
the closed side of the profile. If this is
correct, our phi signals come from the open side
of the profile, the z signals come from the
closed side.
phi strip
ggas fitting HV 0ground
g
g
0
z strip
S1
Phi Cathode signal
Gnd
Large Cell Tube
S1
1nF
scope
HV
S2
Z cathode signal
Anode signal
S2
2
Example 1 Anode at 20 mV, z at 10 mV and phi at
5 mV per division
3
Example 2 Anode at 20 mV, z at 10 mV and phi at
5 mV per division
4
Example 3 Anode at 20 mV, z at 10 mV and phi at
5 mV per division
5

• Conclusion
• We see signal in coincidence at both cathodes
  and the anode
• Anode signals are the largest.
• Followed by the z strip signals (which we
  believe come from the closed side of the profile)
  which are about ½ the size of the anode signals.
• The phi signals (which we believe come from the
  open side of the profile) are about ¼ the size of
  the anode signals.
• Clearly this is not a complete test. The next
  step is to measure pulse height spectra for each
  signal source, check the HV dependency etc.