Vacuum Chamber drawing


Vacuum Chamber Photo


Vacuum Chamber Lid drawings


Dummy card


dummy card and inserts


Potted dummy card(Lid shown transparent)








































Support Frame


The Burn-in System

The Vacuum and Support Structure of the VeLo module Burn-in System

Introduction

The burn-in of devices is only effective if their operational environment is recreated during testing. In the case of the VeLo modules this involves operating them under vacuum(1.0x10-6mbar). The hardware components required to achieve this are presented and described here.

Vacuum Pump System

The Vacuum pump system includes a rotary pump that is connected to a turbo pump (Pfieffer THP 300). Between the rotary pump and the turbo pump a a copper foreline trap has been connected to minimise any possible oil contamination of the chamber and hence the modules.( Missing the connection between the rotary pump and the turbo pump for a complete installation )

On the NW100 flange of the turbo pump a header vessel is attached. This header vessel has one NW25 input for the pressure gauge to be connected to and two of the three NW40 inputs will be used to attach to the vacuum chambers. For each chamber the connection is identical and contains the following components which are connected using centering rings and KF clamps of the correct sizes.

• One meter NW40 flexible steel hose.
• A ball valve
• One reducing Tee
• An Air inlet

Vacuum Chamber

The vacuum chamber employed during the burn-in of each module is a stainless steel cylinder 400mm in diamter and 600mm in length. It has a NW40 inlet for the vacuum to connect to and 500mm flange as its main entry point which is used to introduce the modules into it. A drawing can be found on the left (with the wrong inlet NW25 rather than NW40 and handles which do not exist) together with a photo.

Vacuum Chamber Lid

One of the components that will require the major modifications is the lid that is attached to the flange of the chamber. The modifications are warranted because the number of services required to operate and monitor the VeLo module under test.

Short Kapton Cable Feedthrough

The VeLo module possess a double sided kapton hybrid. On each side there are two 140 way AMP 177983-6 sockets (5mm height) which provides the means by which the electronics are read, controlled and powered. In the experiment the connection between the repeater card and the hybrid is achieved through a two stage kapton cable. In the Burn-in only one stage of the kapton cable will be used (referred to as the short kapton cable) and the feedthrough for the chamber lid is achieved by a custom made pcb circuit.(Sometimes referred to as the dummy card)

On the vacuum side, the feedthrough, has two 100 way AMP 1779983-4 sockets and on the air side it has two 50 way Canon connectors. Each hybrid requires two boards and thus in total the lids requires four holes to be machined. The current feedthrough is made leaked tight by the following method which is illustrated on the images on the left.

1. Solder the surface mount connectors (100 way socket).
2. The pcb is held in place by wrapping the section within the lid with teflon tape. This will keep the pcb in place while the glue dries.
3. Pot the pcb with an epoxy which does not outgass such as Varian Torr seal. Torr seal turned out to be opaque of white colour thus no additional treatment was required to keep the chamber light tight. .
4. If leaks are encountered when vacuum is first applied, plug the leaks with small amounts of epoxy.
5. Solder the 50way cannon connectors in place.
John carried out some tests with dummy pcbs and aluminium. The glue was easy to apply and the seal was strong.

Fluid Feedthrough

( This has undergone major changes since our last meeting. All details are almost worked out and expect to place an order on thursday 09/02/2006 )
The fluid feedthrough is for the coolant that will control the temperature of the VeLo module. A cryogenic feed-through has been chosen because of the temperature that the coolant will be circulated at (-40 - 30C-60C). Initially a single feedthrough was thought possible but in view that the external insulated hoses have an outer diameter of 42mm this was not possible. The maximum distance between the inlet and outlet is 22mm. The solution being pursued at the moment is one flange per inlet. The diameter of the pipe has also being reduced to 3/8inch pipe from 1/2inch pipe. The leadtime on this item is 2 weeks.

Sub D 50pin connector feedthrough

This D connector feedthrough that will be used to connect sensors that will monitor the coolant temperature and the physical distortion of the hybrid. The feedthrough will be welded into a NW100 flange. Originally the plan was to buy the two components and perform the welding in house but it requires plasma welding for which the physics workshop lacked the equipment· A company was located that does produce this kind of feedthroughs and will be obtained from them. Since this is not essential for module operation a blank NW100 flange will be used to cover the opening on the chamber lid while awaiting its arrival.

Vacuum chamber support

The vacuum chamber structure will be built out of 60mmx60mm aluminium extrusion. Apart from supporting the chamber it will support:

• The rail system on which the module (attached to the module) will be extracted from the chamber.(attached to a table on one half of the structure)
• The repeater board crate, attached to the front of the structure that keeping the length of the cables between the repeater board to the module of similar length to the experiment (~1m).
• On the second level of the support frame, power supplies will be placed.

The height of the structure has been set to around 1m which is deemed a comfortable height to work at either standing up or sitting on a high chair. Two companies have been approached to provide it. Waiting on one quote before making a decision.