Prototype Testing

Prototype construction and testing is to be initiated in fall 1991. Chambers S2 and S3 are similar to straw tube arrays documented in the literature. The prototype R&D includes testing various options for gas flow, high voltage connections, signal connections, and mechanical integrity. The feasibility of using fast gases (CF mixtures) in E864 will be studied in a test beam, where the tubes must meet the E864 efficiency and stability requirements while minimizing pile-up.

The R&D work is planned so that chambers S2 and S3 will be ready for operation for phase 1 running in 1994. Chamber S1, which has the added complication of operating inside the vacuum enclosure, is planned to be available for phase 2 running.

Specific development tasks include the following:

• Determine how to keep a large number of straws in position to an accuracy of 100 to 200 microns.
• Build several sections of 500 straws with 6 mutually-supporting planes.
• Construct frame/gas structure, and equip a few straws with real plugs and wires to check operation.
• Work out logistics of electronics and connector placement, wire stringing, methods for replacing wires in the field, and support and alignment of planes.
• For S1, develop vacuum components such as seals and feed throughs.
• Investigate minimum tube wall thickness which can be used in S1 and S2 to minimize background from interactions in these chambers.

Prototype evaluation tasks include the following, using both cosmic rays and beam tests:

• Construct planes of 6.4 cm width, to have a reasonable cosmic ray rate, and to have enough samples to assess variations.
• Measure the efficiency of the X,X' combination, to demonstrate a reasonable high voltage plateau.
• Use TDC's to check that the single plane inefficiency is purely geometrical, associated with the straw walls, and evaluate the effect.
• Study the uniformity of the chambers to check for variations caused by sagitta or gas circulation effects (particularly in S1).

The prototypes to be constructed are as follows:

• S1: 16 X straws, 16 X' straws, 4 mm diameter, 22.5 cm length, in vacuum.
• S2: 16 X straws, 16 X' straws, 4 mm diameter, 40. cm length.

The costs for the development and prototypes are listed in Table .

  
Table: Costs of Development and Prototypes.