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).