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Last updated: 19 October 2004 by Michael Kelsey


The BaBar Prototype II Drift Chamber (Proto II) was built by SLAC's Experimental Group C in 1996, to implement and validate the cell design and gas mixture for the real BaBar Drift Chamber. It is installed in the main laboratory of SLAC's Experimental Group C, in Central Lab Annex B273. Proto II uses production BaBar electronics and data acquisition components, and a three-counter scintillator telescope (with range stack) for triggering.

Hazards and Safety Procedures

History and Operation

("Prototype I" was an electronic mock-up to validate the electronics design, by providing a base on which to mount the front-end assemblies, supply artificial pulses to the readout systems and monitor their output.)

Proto II was last operated in late 1998 and early 1999, during the final commissioning of the full BaBar Drift Chamber. Once PEP-II began delivering colliding beams (May 1999), operation and support of Proto II was suspended, as manpower and resources were redirected to detector operations and physics analysis.

Since July 2001, a small group is working to restore Proto II to operation using the current BaBar detector control and data acquisition systems. This will provide a functional test stand for a variety of purposes, which up to now have required the full detector, including

  • Validating changes to the drift chamber DAQ software;
  • Testing repairs to front end electronics modules;
  • Testing different gas mixtures for aging and stability.
In Jan 2002, Broken wires were discovered in Proto II. This document describes how the broken wires were discovered.

In June 2002 we mapped the Sense and Guard wires on Proto II to discover how many and which were broken. We have completed the first pass of sense and guard wire testing. Examine the results of:

In Short - There are no broken Sense wires and only one Sense wire shows any contact with ground. There are no broken Guard wires though two show contact with ground.

Thanks to Swagato Banerjee and Jignesh Parikh for making these measurements.

New drawings are available that show the position of the broken wire and the Sense and Guard wires contacting ground..

Operating Instructions

Design and Engineering

A large number of the engineering drawings and schematics for Proto II are available in PostScript format in the drawings/ directory.

Block diagrams showing the layout and interconnections of the whole Prototype II system were produced by Lisa Manning during her July-August 2001 project to revive Proto II.

Photographs of the detector setup and electronics racks were produced by Karl Bouldin in August 2001.

The geometry of the chamber wires is defined in an ASCII file containing wire locations, stereo angles, twist angles.

Lisa Manning prepared a report and presentation on her restoration work during July and August 2001 for the SLAC Summer Science Program. This report will be expanded into TNDC Note 01-100.

Archived Information

Old performance reviews and presenations

Results from 1997

For comments, questions or changes to this page contact Michael Kelsey mailb2.gif (2499 bytes)
Information Expires: 31 December 2001