In late April, the first of three parts of the contstruction was undertaken. This involved the preparation of two pairs of a scintillator and an acrylic triangle. Two physicisits from the University of Birmingham, kindly came down for the day to help the construction teams prepare these key components of the detector correctly. To maximise the efficiency of this task, two teams were performing the same task simultaneously. Before all of this could be strarted however, the tables being used had to be thoroughly cleaned so that the amount of dust and other particles settling onto the scintillators and triangles was kept to a minimum (see left). This was a simple task that then enabled the scintillators to be carefully placed in the center ready for preparation (see right).
With the scintillators laid out, the first task was to clean the top and sides of the material as best as possible. This was acheived by removing the plastic covering off the exposed sides and cleaning them in circular motions using paper towels dipped in propanol. This removed, as much as possible, all of the dust and other impurities off the surfaces of the scintillator. Aluminium foil was then laid down onto the table under the scintillator and the cleaned side placed on it. This had to be done, however without touching the side of the scintillator that would be faced down onto the aluminium foil, making the process a lot harder to control than imagined. IF the side was touched, it had to be quickly cleaned again so that there were no smudges left on the surface to interfere with the results that would come once the detector has been completely constructed. This action had three primary purposes. The first was to keep the sub-atomic particles in the scintillator travelling in a more transverse (vertical) movement as well as through the scintillator material horizontally. The aluminium foil also stops dirt and other particles from resting on the surface of the scintillator and damaging the results. The final purpose was that it also stops a portion of light entering the scintillator and sending photons through it which will also cause inaccuracies withing the results. With the scintillator now 'up-side down' on the aluminium foil, the sides and main surface were all thoroughly cleaned in the same process as with the original cleaning before being completely wrapped in foil. The 'package' was then taped down so that the aluminium foil does not work its way loose with black insulation tape. One end of the scintillator however was not taped down as this part of the foil will ultimately be removed when the scintillator is glued to the acrylic tile. For now, however, it serves only to protect the scintillator itself from dust and other particles whilst it will remain in storage. The pictures orderd below clearly show the order in which the scintiallator was initially prepared and wrapped and in aluminium foil.
With the scintillators covered in the aluminium foil, the focus turned to covering them in a black rubber lining. The reason for this is to protect the scintillator from any scratches, as aluminium foil is very thin and so easily broken exposing the scintillator surface, whilst also stopping all light from reaching the scintillator plate. The dimensions of the scintillator were measured out and a slightly large peice of the lining was cut out and placed underneath each scintillator. Then, as with the aluminium foil, the scintillators were packaged up in the black lining and secured with black duct tape instead of insulation tape. The same end of the scintillator was left 'exposed so that the arcrylic triangle can be attached at a later date. With the scintillators carefully packaged up, they were stored with the loose end facing upwards until they are needed later on in the year for the rest of the assembly of the detector. Again this sequence of events can be seen below, in order.
With the scintillators prepared and placed into storage, the focus of the construction teams moved to the acrylic triangles that would be meticulously glued onto the scintillators themselves. The process however remained unchanged. First the coverings were removed and side of the acrylic was cleaned with propanol. Aluminium foil was then placed under the cleaned side of the triangle, and the rest of the acrylic sides were also cleaned. The triangle itself was then carefully wrapped in aluminum foil with one end not fully sealed so that it can be uncovered in the future when it is required. The aluminium wrapped triangle was then wrapped again in the black rubber lining for security and complete light protection and stored with the scintillators. This process has again been summarised into the sequence of pictures below;
Late May saw the second set of visits from the University of Birmingham, to help with the installation of the detector. The first visit saw the two scintillators being attached to their respective acrylic triangles. This involved using some very expensive glue and a special stand to help clamp the detector peices in place. The stand was designed so that the detecor plates would be clamped vertically and away from all surfaces. The benefit of this is that it stops the plate from also being glued to the surface on which it is being rested upon. This is crucial as if the plate gets stuck to the surface, this could damage the material itself when prising the plate from the attached surface. The other benefit of having the detector plate placed away from all surfaces is that whilst the glue is setting, part of the scintillator and acrylic will be exposed and if it is rested upon the table, the extensive cleaning that take place during the University's first visit will have to be re-done on the exposed areas which will delay the project and waste time.