Work Plan for the End Cap Thermal Enclosure – 27.09.05

The remaining items that are required for completing the production of the End Cap Thermal Enclosures are described here. The major items making up the thermal enclosure are being manufactured at (a) CERN, who are constructing the Rear Thermal Pad and Inner Thermal Enclosure (ITE) and (b) Valencia University, who are developing the construction method, prototyping and manufacture of the Outer Thermal Enclosures (OTE).

The work to be undertaken at RAL will involve close cooperation with the above institutes and careful observation of their production output. Other activities at RAL include the manufacturing of the front and rear membranes and the production of all the mechanical items required for the LMT cooling on the support cylinder.

1.Membranes

Information was obtained from GTS on methods of cutting the material and drilling of holes in the Cu-polyimide. However tests at RAL using a punch demonstrated very satisfactory results, and this method will be used to form the holes in the material. Cutting the sheets using a scalpel around a former produces satisfactory results and this method will be used for shaping the membranes.

To complete the construction of the membranes and the LMT cooling components the following activities need to be carried out:

1.1Displacement tests under pressure loads

Under normal operating conditions, the membranes are subject to an internal pressure of approximately 4 mbar. In this condition, the entire surface areas of both membranes are fully supported by each of the wing panels.

In the case of a possible and foreseen under-pressure, the front membrane will be unrestrained and will undergo a displacement toward disc 1, risking contact with the detectors mounted upon it. The magnitude of the under-pressure is expected to be of the same order, i.e. approximately 4 mbar.

This test is performed to investigate what deflections are likely under these circumstances and to determine if any stiffening of the film needs to be provided. The above figure shows a slightly exploded view of the components that can be used to carry out the test. It will use items that already exist for previous tests as well parts intended to be used as templates for cutting the films and forming the holes. The materials used throughout are machined MDF sheets.

1.2Machining Templates and performing pressure tests

To reduce costs and save on materials, the template for the holes for both front and rear membranes will be machined into the larger template used to cut the rear membrane. This means that only a single annular disc for cutting the front membrane is needed (with only a few holes required for fixing to the cutting board).

The following steps are foreseen:

  • Create solid models in ProE of the front and rear templates and the solid centre disc used for the test and convert them to DXF files for CNC machining information.
  • Contact manufacturers and supply drawings and DXF files (C&G Joinery, Wantage)
  • Procure essential materials including aluminised Kapton, pressure measuring devices (simple manometer), small pump (lungs may suffice), tubing, glue, tape, fixing screws etc.
  • Prepare test area (R12 surface table) and cut appropriate size Cu-polyimide film
  • After manufacture, assemble components according to above figure
  • Perform test and measure the deflection of the membrane using suitable depth gauge
  • If displacement is excessive try bonding radial stiffening strips onto the free membrane region and repeat test until satisfactory deflections are obtained.

1.3Production of Membranes

The membranes will be prepared and bonded in R12 on the steel surface tables. A suitably large piece of MDF sheet will be needed as base for cutting the membranes. For the front membrane the roll width is just sufficient to create a single piece, but the rear membrane must be made from two pieces since the diameter is larger.

For cutting the membranes the following procedures should be carried out:

Front Membrane:

  • Cut a suitable length of Cu-polyimide film and lay onto the MDF cutting board.
  • Place template over the film and fix to the cutting board using woodscrews through the holes in the template panel (these holes are to be lined with special inserts).
  • Cut around the template into the Cu-polyimide film on both inner and outer diameters to form the annulus.
  • Unscrew and remove the template from the cutting board
  • Repeat this process to cut the plain Kapton film (don’t use aluminised Kapton now) using the correct template.
  • The two films are then carefully aligned and bonded together according to drawing TD-1012-444.
  • Place the rear template over the bonded front membrane on top of the cutting board and carefully align the inner diameter of the annulus to the template.
  • Fix to the cutting board using woodscrews through the holes in the template panel (these holes are to be lined with special inserts).
  • Place the 8mm punch into each of the guide holes in the template and strike with a hammer to cut through the Cu-polyimide and Kapton films underneath.
  • Make slits to create tabs – more may be needed later.

Rear Membrane:

  • two sheets of the Cu-polyimide film must be cut and soldered together according to drawing TD-1012-535 (3/3).
  • The process of cutting the film should proceed as for the front membrane using the rear template.
  • Place the 8mm punch into each of the guide holes in the template and strike with a hammer to cut through the Cu-polyimide sheet underneath.
  • Make slits to create tabs – more may be needed later.

Boxes will be needed for storage and transport.

Templates are needed for:

  • Holes (Front & Rear) Rear ID/OD
  • Front ID/OD
  • Front membrane gas seal ID/OD

2.LMT COOling

The baseboard for the LMT clip tests (including potential proposed tests for cooling trials) is now completed and the LMTs have been added to this assembly. The support posts for the cooling tubes were included and they seemed to do the job perfectly, by providing a rigid restraining action and setting the tube position at the correct distance above the baseboard. It was noticed that the thickness of the LMTs obtained from Glasgow were greater than those originally proposed and previously tested at RAL and there was concern that this may cause damage to the Cu-Be clips through over-stressing.

There was also concern that the polycarbonate LMT retaining clips did not make the tapes at the top of the largest tape stack easy to engage and there was worry that a significant amount of forcing of the tape into position may cause damage.

The Cu-Be clips arrived on 27.09.05 and they were mounted initially on an earlier test-board supporting just the two cooling tubes to check that the springs were going to flex as expected. These clips were supplied in both fully hard and half hard condition which allowed some adjustment of the clips to be made if required. It became necessary to make some minor dimensional changes to these clips and when tried out on the large baseboard containing the LMTs they worked very satisfactorily, providing an even and distributed load over the top of the LMT stack.

2.1Cu-Be clip tests

The clips that were supplied for the assembly trials will undergo a further set of rigorous tests to prove their satisfactory performance, even though they already demonstrate high strength and resilience. The softer (half-hard) specimens will be dimensionally altered to the shape that gives the optimum performance. The drawings for these clips will be modified accordingly and the manufacture of the production items will be commenced once their performance has been proven. Specifically:

  • The strain relief will be lowered to avoid damaging the OTE.
  • The length of the clip will be adjusted to accommodate the expected Pipe separation.

Once it has been established what is the correct LMT thickness used for the End Caps, the base board will be set up to support both the minimum and maximum the LMT stack heights so that the clips are tested in both their extreme situations.

The LMTs have been prepared with soldered power supply wires so that should any thermal tests be required, it would be a simple matter to go ahead with and the cooling tubes could be very simply connected to a re-circulating water chiller.

2.2Preparation of heat Al foil spreaders

Rectangular aluminium foils (50 microns thickness) should be prepared to slide under the slip-sheets and wrap around the cooling tubes (this is discussed in more detail in document “LMT Cooling – Guidelines for the assembly of cooling components - Peter Ford: Draft 2 - 21.07.05”

The length should be sufficient to completely envelope the LMTs with an extra overlap of ~5mm-10mm on the exposed surface of the LMTs.

Unfortunately the distance between the cooling tube pairs is different from one location to another, which suggests that there may be a varying amount of excess length in the foils. The distance between the tube centres was measured at Liverpool and varied between 81.0mm to 82.5mm (however this is less than would be expected from the size of the polycarbonate LMT clips). The minimum foil length required to ensure complete wrap-around with 5mm overlap for the worst location is ~220mm. After wrapping the foils around the tubes and LMTs it may be more desirable to trim off any unnecessary excess at this juncture to ensure that the overlap is minimised.

This could be done by carefully snipping off an appropriate quantity of foil from one or other of the ends of the sheets. It is felt however that the tubes are so compliant that they will move under the spring clip force to adopt a position where they rest up against the LMT guide clips.

Widths of 49mm will allow optimum coverage from one slot to the next as far as the LMT guide clips will allow. Any remaining uncovered regions after fitting the 49mm wide foils can be tailor fitted with the necessary widths cut to suit.

A standard office paper guillotine with a single downward-action cutting blade was purchased for cutting the foils. Early tests demonstrated that this produced an excellent cut edge and the base-table was equipped with a ruler, a clamp and a guiding edge to ensure the cuts were both straight and perpendicular.

To minimise the time required to form each of the aluminium foil sheets, careful thought at their initial cutting will be required. Firstly, they have to be cut to a size that will optimise the deposition of the alochrome coating and at the same time make full use of the capacity of the guillotine.

Before the aluminium foils are wrapped, the cut edges of the aluminium foil should be permanently covered with Kapton sticky tape along each edge, as shown in the photograph above. This is needed to protect the LMTs and other fragile components from whatever damage may occur if any unnoticed sharp protrusions are formed during the cutting of the foils.

The tape is cut over-length and stuck down half on one side, then folded over the edge to cover a similar size area on the other side with the remaining half-width. Care should be taken to ensure there are no kinks or bubbles under the tape. The aluminium sheets should remain flat during the preparation process above. Finally, the excess Kapton can be trimmed off with scissors.