The Straw Tube Tracking Chambers for Fermilab Experiment 831 (FOCUS)
Fermilab experiment E831 is a high
energy physics experiment designed to study the production and decay of
charm particles. The experiment will use a several hundred GeV photon
beam striking a dense target to produce these particles. The
interaction rate inside the target is expected to approach 15 MHz!
The vast majority of these interactions will be electron-positron pairs
produced by photon conversions. Studies show that most of these pairs
will pass within a 4 centimeter swath down the center of the FOCUS spectrometer. The Multiwire
Proportional Counters (MWPC'S) used for tracking particles downstream
of the first analysis magnet, were not designed to handle a 25 MHz
charged particle rate, and are being modified to reduce their
sensitivity in the region where pairs predominate. This reduced
sensitivity region will be recovered by the addition of central region
tracking chambers constructed with 5 mm Straw Tubes (ST).
The University of California at
Davis is designing and building the ST's. The design is based on
the Brookhaven Experiment 871 design, and uses the same front end
electronics and readout system. UCD has
built a total of five chambers, three for use during the run, and two
backup chambers in case of failure. The three chambers will be placed
in direct proximity to the currrent MWPC's located between the two
dipole magnets. Each chamber houses three views, one vertical and
two stereo (11.3° with respect to vertical). The first chamber,
ST-0, consists of 54 inch long straws, while the second and
third chambers, ST-1,2 were constructed from 95 inch long straws.
The total number of channels in all ST's is 1206.
Construction was completed in January 1996 and all chambers have been
shipped safly to Fermilab.
To look at the straw chamber's technical data click here
Last Edited 8 April, 1996
Jon Link, link@ucdhep.ucdavis.edu