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TPC Wire/MWC Information
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  Last modified: 11:50 Thursday 08-JUN-2000

See the TPC wire plane diagram (Postscript) for the wire layout; or the calculated capacitances for the anode, ground and gating-grid wire capacitances. Note that there is also some "lumped" capacitance due to the wire terminations.

HV is fed to the TPC anode wires from either an "Anode Bias Distribution Board" (ABDB) in groups of 20, or from a "Little Orphaned Anode Board" (LOAB, sometimes also referred to as a "Little Orphan Annie Board") in smaller groups.

There are three distinct types of LOAB:

The pad plane geometry in the region of the OSOR anode wires is shown here as an example:

Within each subsector, 160 anode wires connect to ABDB's; the signals go to 16 MWC card sockets on each sector. (Two subsectors per sector, with 160 instrumented wires/subsector and 20 channels/MWC socket, works out to 16 sockets/sector.)

Special MWC boards - resembling the FEE cards for the pads - can plug into these sockets. For the engineering run in late 1999, Sockets #2-16 held unpowered MWC cards, while, at this point, Socket #1 will only hold a grounding card. It is expected that Socket #1 will eventually be fitted with a modified MWC board. Therefore, one expects gain calibration bias when comparing different pad rows with the ground-wire pulser.

Finally, a dedicated MWC readout board - resembling the main RDO boards for the pads - in mounted on each sector to aquire and transmit data from as many as 16 MWC cards.

Inner sector anode-wire information and MWC-socket connections:
Wire range
Radius to
first wire
(cm)
Radius to
last wire
(cm)
ABDB
LOAB
MWC
socket
Notes
1 - 20
53.200
60.800
X
 
1
1, 2
21 - 40
61.200
68.800
X
 
2
 
41 - 60
69.200
76.800
X
 
3
 
61 - 80
77.200
84.800
X
 
4
 
81 - 100
85.200
92.800
X
 
5
 
101 - 120
93.200
100.800
X
 
6
 
121 - 140
101.200
108.800
X
 
7
 
141 - 160
109.200
116.800
X
 
8
 
161 - 170
117.200
120.800
 
ISOR
 
1

Outer sector anode-wire information and MWC-socket connections:
Wire range
Radius to
first wire
(cm)
Radius to
last wire
(cm)
ABDB
LOAB
MWC
socket
Notes
1 - 7
122.795
125.195
 
OSIR
 
3
8 - 27
125.595
133.195
X
 
9
 
28 - 47
133.595
141.195
X
 
10
 
48 - 67
141.595
149.195
X
 
11
 
68 - 87
149.595
157.195
X
 
12
 
88 - 107
157.595
165.195
X
 
13
 
108 - 127
165.595
173.195
X
 
14
 
128-147
173.595
181.195
X
 
15
 
148 - 167
181.595
189.195
X
 
16
 
168 - 172
189.595
191.195
 
OSOR
 
3

Notes:

  1. Inner sector Wires 1 (R=53.20 cm) and 170 (R=120.80 cm) have 125-um (rather than 20-um) diameter; their gain is very low.

  2. MWC socket 1 was unfilled during Summer 1999 running. In Fall 1999, a grounding card (modified FEE grounding card) will be installed, but it is hoped that the socket will be instrumented eventually.

  3. Outer sector Wires 1 (R=122.795 cm) and 172 (R=125.195 cm) have 125-um (rather than 20-um) diameter; their gain is very low.

  4. MWC's were not powered until Spring 2000 running, so the input impedance was not well-defined before then; the inputs were, effectively, partway between floating and ground.

  5. All ABDB and LOAB resistors are 10 megohm; all capacitors are 0.001 uF. HV goes through a resistor to the group of 20 anode wires, then through another resistor to each anode wire. Anode is AC coupled through a capacitor.

  6. On ABDB's, a connection to the MWC socket and a resistor follows the capacitor; on LOAB's, the capactor connects directly to ground.

  7. See ABDB and LOAB figures for more information.

  8. Through September 1999, the positions of the MWC wires in the GSTAR Monte Carlo were slightly offset radially. The offset was +1.669 cm in the inner subsector and +0.093 cm in the outer subsector.

Thanks to Jim Hunter, Eric Hjort and Jon Wirth for information and prints on the ABDB's, LOAB's and their connections; and to Spencer Klein and Joakim Nystrand for information on the MWC cards.