LHCb OT Module Components

Wire Locators & Straw Blocks


Injection Molded Pieces



The Outer Tracker Wire Locators and Straw Blocks will be produced by Philips High Tech Plastics.

Several prototypes have been already produced by Philips. They were surveyed at NIKHEF and found compliant to the technical specifications.


4-fold Injection Inj. Mold 3 Inj. Mold 1



Wire Locators

Anode wires longer than 1 metre are at intermediary positions supported by so-called "Wire Locators".

The chosen interval between wire locators guarantees that the sagitta due to electrostatic forces on a not perfectly centered anode wire remains small. Typically, these are spaced at intervals of 80 cm. The precise distance necessarily depends on the total wire length to be subdivided and thus varies slightly from module to module. The largest number of locators per wire section, i.e. between end-and middle-block, is two.

We experimented with locators of quite different shapes. The final choice is suitable for production by injection moulding and was designed by NIKHEF in cooperation with Philips High Tech Plastics.

The design was based on the following criteria:

The locator essentially consists of two disks from which V-shaped sections, with opposite orientations, have been cut out, the overlap of which leaves an opening of about 0.050mm diameter for the anode wire.

Wire Locator Wire Locator 3 Wire Locator 2

The geometrical dimensions and tolerances are specified in the sub-assembly drawings of the detector modules.

Locator Design

The Wire Locator design was validated through the following tests:

  1. ease of wire insertion through a series of locators with the aid of a combination of vacuum and pressurized air techniques (i.e. time needed for the operation and failure rate)
  2. dedicated study of the electrical properties of the locators

Straw Middle- & End-Blocks

At both ends, the straw tubes fir onto cylindrical protrusions of a gas distribution block. Centring of the sense wire ends requires wire-locator functions to be incorporated in these "Straw Blocks".

Straw View
Middle Block End Block


As for the Wire Locars, the Straw Blocks are suitable for production by injection moulding and were designed by NIKHEF in cooperation with Philips High Tech Plastics.



End Block 3 End Block 2 Middle Block 3

The geometrical dimensions and tolerances are specified in the sub-assembly drawings of the detector modules.

EndBlock Design MiddleBlock Design