2 The CDF Experiment at Fermilab Contents - Harvard University ...

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6 Section 2: CDF Hardware Au mylar sense wire support wire potential wire Figure 1: em COT cell geometry measurements, out of 84 total. This meant rst that the stereo view could not be completed without an externally supplied z 0 . In addition, at high luminosity the occupancy caused a signicant loss of eciency in the innermost superlayers, resulting in a decrease in the 3D track reconstruction eciency. Various dierences between the CTC and the COT are revealed in Table 2. The COT is segmented into 8 super-layers alternating stereo and axial, with a stereo angle of 2 . Both axial and stereo super-layers contain 12 sense wires alternated with 13 potential wires which provide the eld shaping within the cell as shown in Fig. 1. Whereas the CTC used wires between the cells to complete the eld regions, this is accomplished in the COT by gold-coated Mylar sheets. This gives a more uniform drift eld and reduces both the overall mass of the chamber and the tension on the endplates. Roughly 1500 eld sheets for the stereo super-layers were produced at Harvard, while some 1700 axial eld sheets were produced at Lawrence Berkeley National Laboratory. The sense wire planes were built at Fermilab. Field Sheet Construction The construction of the eld sheets was undertaken at Harvard by one professor, Melissa Franklin, one post-doc, Kevin Burkett, three graduate students, Carter Hall, Robyn Madrak and Melissa Wessels, 5 undergraduates, Tobias Jacoby, Sarah Demers, Caolionn O'Connell,
Section 2: Central Outer Tracker 7 CTC COT Max Drift Time 706 ns 100 ns Max Drift Distance 3.6 cm 0.88 cm Total Layers 84 96 Total Sense Wires 6156 30240 # Axial Layers 60 48 # Stereo Layers 24 48 Radiation Lengths 1.7% 1.3% Table 2: Comparison of mechanical design parameters of the CTC and COT. Carina Curto, Sarah Fung, one technician, one machinist and three temps. The eld sheets are 6.35 m Mylar coated with 450 A gold. The gold sheets are epoxied to aluminum endboards which latch onto the endplates of the chamber. To maintain the atness of the sheets, two 305 m (12 mil) stainless steel wires are epoxied along the edges of the sheets in a parabolic shape. When the sheets are placed under tension, a fraction of the longitudinal tension is transferred to lateral tension by the wires. We tried to make these eld sheets as at as possible, given gravity. To maintain uniform gain, local variations in the shape of the sheet, i.e. ripples, must be controlled. The sag of the sheet must also be controlled to avoid excessive displacement of the sense wires when the High Voltage is turned on. Studies of gain variation as a function of the amplitude of ripples in the sheet have shown that the latter must be less than 10 mils. The average position of the sheet must be good to 5 mils to minimize sense wire motion. Allowed variations in sheet length were kept small in order to allow for an error in predicted endplate deection under tension. The allowed variations in sheet length, as well as the number of sheets required in each stereo super-layer, are shown in Table 3. A test xture was built by Harvard that has been used to measure the length and the shape of sheets under the nominal 22 lbs. of tension that will be applied in the chamber. This same test xture was used at Berkeley. As it is dicult to dierentiate between sheet sag and ripples in the test station, a 5 mil window is allowed for the shape of the sheet in the test xture. All passing sheets fell within this window and had a measured length which was within the allowed range for the superlayer in which they are used. Fig. 2 shows distributions of the dierence between actual sheet length and desired length, in inches, for
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Page 3 and 4: Section 2: CDF 3 of Run I data. Rec
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Page 36 and 37: 36 Section 2: CDF 2.3 Run I Physics
Page 38 and 39: 38 Section 2: CDF Physics Analysis
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Section 2: CDF 97 multijet trigger
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Section 2: CDF 99 The Jet Pseudora
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Section 2: CDF 103 Talks at Confere
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Section 2: CDF 105 References [1] T
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