Support and Cooling Status

OCTOBER, 2003

Our previous design of the cooling and support structure has a large number of cooling joints. There are serious concerns on the potential leaks and their impact on the operation of the Tevatron. To address these problems, we will use a joint-free design. Our new baseline will use thermal pyrolytic graphite (TPG) which has excellent thermal conductivity.

The cryo panels introduced for vacuum purposes will be cooled by liquid nitrogen. A liquid nitrogen cooled heat sink will also be used to remove the heat generated by the pixel readout chips. By varying the thickness and width of a Thermal Pyrolytic Graphite (TPG) support, we have demonstrated by Finite Element Analysis that the operating temperature of the detector can be kept quite uniform and below 0 degree C everywhere. Prototyping work has also started on actual pieces of TPG and on flexible joints for connecting the TPG to outer supports using Pyrolytic Graphite Sheet (PGS). A number of dummy silicon modules are being assembled for placement on a TPG substrate. Thermal profiles and mechanical displacements will be measured, and compared to finite element analysis.

APRIL, 2002

Prototype support and cooling structures have been built in aluminum, in steel, and in a fuzzy-carbon technology. Two fuzzy-carbon devices based on a year 2000 design have been delivered. Beryllium supports have also been ordered for testing. The baseline fuzzy-carbon devices have been fragile, but sufficiently attractive to encourage us to plan on two full-size half-planes as the next step in our testing. Pocofoam(TM) devices are also being designed.

Tests of cooling performance, stress, deflections and other mechanical properties have been done and continue. Similarly, a one-third-size prototype of the outer structure assembly and an air-actuated positioning drive system have been built and tested.

The progress and the remaining technical challenges have been such that a full technical review of the conceptual design has been held. The results of that review have led to increased emphasis on these issues, including step-by-step construction procedures as well as the basic assembled design. As part of the ongoing tests, a 10%-scale system of the full-sized mock-ups is being put together. This is helping to demonstrate multi-chip module assembly techniques and placement accuracy.

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