Pixel Support Tube (PST)

Introduction

The pixel support tube (PST) consists of three parts: 2 forwards and 1 barrel. It delivers the pixel package to its installed position in the ID and serves as both an electrical and thermal environmental barrier.

Models

The following CAD models (STP files) contain the current pixel support tube geometry.

Barrel

Forwards

• Forward A
• Forward C

Heater Panels

The PST shell is covered with heater panels. They are used to keep the dew point above 15C when there is a failure of the dry gas system.

Wiring

The heater panels are wired in pairs. Each panel is also equiped with an NTC mounted in the middle. This means that, for every pair of heater panels, there are:

• 2 Supply wires, 24AWG
• 1 Drain wire, 24 AWG
• 4 NTC wires, 28 AWG (these are grouped into two distinct pairs)

These 7 wires go into 1 JST 8-pin connector. This is called a cable. Groups of 3-4 cables are grouped together to form a bundle. Each bundle goes to 1 distinct heater patch panel. The numerology is as follows:

• 100 heater panels (28 barrel, 36 per forward)
• 50 cables of 7 wires
• 14 bundles of 3-4 cables (6 with only three cables)
• 14 patch panels

The heater panel details are described in this presentation.

Extensions

Due to some errors in routing and length determination, several heater wires are too short. The lengths of all wires have been measured, and the numbers and lengths of extensions have been calculated. Please note the following:

• NTC wires are in identical length pairs. Every NTC length measurement is in fact for a pair of wires.
• 400 mm of excess length has been added for safety. For this reason, there is no need to fabricate extensions if they are below 50 mm in length.
• All wires in a given cable should be of the same length, to make termination to the connector easier.
• Cables of a given bundle should be the same length, as they go to the same patch panel.

The Heater QA Sheet can be found here. It includes the lengths of cables and the extension cables needed.

-- NealHartman - 19 Sep 2006