The CDF Baylor HEP group has played a significant role in the design, installation, commissioning, operation, and maintenance of the eXtremely Fast Tracker (XFT), the the Level 1 tracking trigger at CDF. The performance of the XFT has been excellent over the years, functioning better than the design specification at low instantaneous luminosity. As the performance of the Tevatron improved over time, an upgrade to the original XFT system was needed to accommodate the high-luminosity running environment. The Run 2B XFT upgrade is now completeand fully operational. Baylor was one of six university groups that participated on the Run 2B XFT upgrade project, and today our group provides primary operational and maintenance support for the entire system.

Overview of the Run 2 XFT System

CDF employs a three-tier trigger system to identify interesting physics events that are written to mass storage for further offline analysis. Each successive level of the trigger applies more stringent selection criteria, reducing the raw collision rate of 2.5 MHz at the input of Level 1 to about 140 Hz at the output of Level 3—a rate at which event data can be recorded to disk. The XFT is a crucial component of the Level 1 trigger. Consisting of custom-built hardware, the XFT identifies charged particle tracks in the Central Outer Tracker (COT). It is an essential part of nearly all CDF measurements. A schematic diagram of the complete XFT system is shown in the following Figure. Elements of the original Run 2A XFT are depicted in green. The XTC mezzanine cards, which reside on the Time to Digital Converters (TDCs) in the CDF collision hall, classify hits on the axial COT wires as “prompt” or “delayed” and pass that information to COT transition modules at the rear of the TDC crates. The COT transition modules drive the data at 45.5 MHz, with Low Voltage Differential Signal (LVDS) technology, onto Level 1 trigger cables (“Ansley cables”) that carry the COT wire data 220 feet to the Finder transition modules, which are located in the CDF first-floor counting room. The Finder transition modules pass the COT wire data to the Axial Finder modules, which identify valid track segments in each of four axial “superlayers” of wire planes in the COT. The Finder then passes these track segments to the Linker modules, which seek valid tracks that cross all four axial superlayers. The elements of the Run 2B XFT upgrade are colored orange and blue in Figure 3. The upgrade preserved many components of the original system, but it incorporated new modules to process information from the outer three stereo superlayers of the COT (SL3, SL5, and SL7). The TDCs that process stereo hit information for these superlayers are outfitted with new Run 2B XTC mezzanine cards (XTC2 cards) that digitize information in six time bins rather than two, significantly improving the hit time resolution. Data from the new XTC2 cards are serialized by new TDC transition modules and sent by optical fiber cable to new Stereo Finder modules, located in the CDF first floor counting room. The Stereo Finder modules identify track segments in the stereo superlayers, and these are passed to new SLAMs (Stereo Linker Association Modules) that merge the new stereo segment information together with the Linker tracks identified in data from the axial superlayers. The upgraded system also passes track segment information directly to the Level 2 trigger. Baylor ’s Contributions to the Run 2B XFT Upgrade.

Baylor’s Contributions to the Run 2B XFT Upgrade

Baylor joined the CDF Run 2B XFT upgrade effort in June 2004. Since that time, our group has been active in several crucial areas. This work, performed with support from DOE grant funding, gave our group tremendous expertise. We continue to draw upon this expertise for the current operation and maintenance of the XFT system.

XFT Infrastructure Specification, Installation, and Testing

The Baylor group handled several aspects of the overall XFT system infrastructure: (1) establishing the specification for the optical fiber cabling from the TDC transition modules to the Stereo Finder modules and from the Stereo Finder modules to the SLAM modules, (2) creating the map for all optical fiber connections, (3) dressing fibers in the TDC crates and Stereo Finder crates, (4) debugging installed system modules using Baylor- written software, and (5) testing and debugging the XTC2 → Stereo Finder data chain.

XFT Software Development and Implementation

Baylor took on a leading role in developing software in the CDFVME paradigm for the Run 2B XFT system. CDFVME software was crucial for the successful commissioning of the Run 2A XFT system, and it became the bedrock for important commissioning and integration tests during the Run 2B XFT upgrade. This software has been used extensively and will continue to be used for the duration of Run 2 at CDF. Baylor students were primarily responsible for this work.

XTC2 Development, Testing, Installation, and Commissioning

The design, layout, and production of the Run 2B XTC mezzanine card (XTC2) was the responsibility of the University of Illinois group. Nevertheless, Baylor worked very closely with Illinois in several areas. Many members of our group were heavily involved in the following: (1) developing a specification for the XTC2 mezzanine card that was backward-compatible with the original Run 2A XTC cards, (2) testing preproduction versions of the XTC2, (3) performing checkout tests of the XTC2 with TDCs prior to their installation at CDF, and (4) writing CDFVME software for integration tests involving the XTC2 cards.

Baylor ’s Current Contributions to the XFT System

From June 2008 to June 2009, Baylor was primarily responsible for the operation and maintenance of the XFT system. After Krumnack’s departure from Baylor in June 2009, Homer Wolfe (The Ohio State University) worked with our graduate students to provide on-call support for XFT operations in an interim capacity. Kasmi, who joined our group as a postdoc in May 2010, now provides primary support for the XFT system and plans to continue this support for a few years. We currently perform the following activities:

• Ensuring the proper operation of the XFT system crates

The Baylor group has taken over the primary responsibility for the stable and reliable operation of all Finder crates (both Run 2A and Run 2B) and the XFT part of the COT crates, i.e. all the installed XTCs, XTC2 cards, TDC transition boards (both for Ansley cables and fibers), Finder modules, and Stereo Finder modules.

• Providing on-call XFT system expertise

Bland, Frank, Hewamanage, Kasmi, Krumnack, and Wu have served as pager carriers to provide support for XFT operations. This work is currently performed by Kasmi and Wu. The Baylor group also created and continues to maintain the XFT online documentation (web pages).

• Providing XFT monitoring expertise

Frank has written software that analyzes pp collision data to produce efficiency plots for XFT track segments and tracks. Frank’s tool provides tremendous diagnostic information, and these new histograms have been implemented in OB J E CT MON, one of CDF’s consumer monitoring programs. They provide immediate feedback to the shift crew regarding the status and performance of the complete XFT system. Our group continues to provide expert support for this monitoring software.

• Maintaining spare XFT modules and the dead wire list

Kasmi (together with H. Wolfe) keeps an organized inventory of spare modules that are on hand in case of hardware failures in the present system. Kasmi also maintains a list of dead COT wires used by the XFT Finder modules to maximize the segment-finding efficiency.