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2.2.2 Outer Tracker and TOF System

A prototype Low-Mass Drift Chamber has been tested at CERN with a 5 GeV/c pion beam using a (70%-30%) gas mixture[11]. The space resolution was measured better than along the whole drift cell, with 98% average efficiency. The coordinate along the wire is measured by charge division with a resolution of the 0.61% of the wire length. The large chambers will be assembled at TRIUMF while the small chambers will be assembled in Turin (for a total of 16 chambers plus 4 spares), from May 1995 to December 1995. All readout electronics is defined and characterized, delivery will start in October 1995.

A 8-channel Straw Tubes prototype was tested at CERN with m.i.p.'s in May 94 using DME, attaining a space resolution [12]. A 160-channel prototype with axial and stereo superlayers was tested at TRIUMF in December 1994 with a 300MeV/c pion beam to investigate the use of alternate gases ()[13]. Test beam results show that space resolution is attained with the alternate gas mixtures studied. Assembly and quality control of about 2700 straw tubes will start at LNF in October 1995, with assembly inside the detector frame starting by March 1996.

Two scintillators (NE102A and Bicron BC408) have been tested and proved to meet both the attenuation and light output specifications of the outer TOF array (TOFONE). Geometry of the counters is defined (255 cm length, 10 cm height, 10.7 cm and 11.6 cm bases). A 80% efficiency light transmission to the photomultiplier was found by using conical deflector prisms. Extensive testing brought to characterize photomultipliers able to provide the required time resolution: Philips XP2020, XP2262B and Hamamatsu R5686 all met specifications, tender open to select the less costly option. A 700 ps time resolution was obtained with a prototype bar. Delivery is expected to be complete by November 95 for all components (scintillators, light guides, and PMT).


next up previous
Next: 2.2.3 The Superconducting Solenoid Up: 2.2 Status of Subdetectors Previous: 2.2.1 Interaction/target Region



Carlos E.Piedrafita