Introduction

A full scale cooling test for the Multiplicity Vertex Detector (MVD) was recently performed [1-2]. In order to test the cooling system and do a vibrational analysis, one half of the MVD was assembled and the cooling components attached. This met that we also had to assemble the endplates of the MVD. This allowed us to study assembly and system integration issues as pertaining to the MVD endplates.

The challenge with assembling the endplates is that there cannot be any conduction between the inner and outer shields and the "D" rings of the endplates after they are adhered to one another. Thus, plastic was adhered between the inner and outer shields of the endplates to ensure that there would be no conduction after assembly.

Materials Used and Procedure

The materials used in assembling the endplates were:

The assembly procedure which we utilized is described below:

1. We washed rings and shields rubbing alcohol.

2. Using conductive epoxy (from TraBond), we adhered the Al shields onto their corresponding Aluminum D rings. (See Endplate Explosion) This was allowed to dry overnight.

3. Dry adhesive was adhered to the the inner and outer shields opposite the "D" rings in order to apply a plastic insulate between the shields. The adhesive was then cut to the size of the shield. We then rolled the adhesive to get rid of any bubbles that might have formed when adhering to the shields The adhesive was then cut out of the rectangular holes for the connectors and the round holes for the screws and air cooling systems.

4. We took 1/4 mil mylar (in stock), layed it flat and stretched it out on a table. We made sure the surface was clean, then layed the smaller, inner shield onto the mylar. This led to complications which are described below. We then cut the mylar to the size of the plate.

5. Using four screws (in the four screw holes in the shields), we easily aligned the inner and outer rings/shields and adhered them together.

Results of Assembly Procedure

After gluing the inner and outer rings/shields together to make one endplate, the plates were still able to conduct, even with the mylar in between them. We believe the plates became conductive when we tried to remove the unused dry adhesive that was left exposed on the outer ring. We believe that using the sandpaper to remove the unused adhesive was the problem. The sandpaper is made from graphite. The graphite was able to get in between the two plates along the very outer edge of the ring and form a conductive path between the two plates.

We also believe that while cutting the mylar out of the holes for the cooling system (no other holes were cut), that the sharp edge of the exato blade could have bent a small piece of the Al shield and made contact with the other shield, causing a conductive path to be formed between the two shields.

Needless to say, our first pass at assembling the endplates met with no success. We needed to change our procedure to better ensure that we would get a non-conductive endplate on our next try.

Changes in Assembly Procedure

On assembly of the next endplate, I changed the procedure to eliminate the possibility of any excess dry adhesive on the outer ring. Instead of adhering the mylar first to the inner shield, then to the outer shield, we first adhered the mylar to the outer shield, then adhered that to the inner shield. This would ensure that no dry adhesive was left exposed after assembly. Also, to ensure that no small Al pieces were bent and made a conductive path between the two shields, we cut the mylar out of the cooling system holes first before adhering the shields together. In addition, instead of cutting out the holes for the screws to go through and help align the two plates for adhering, I cut only slits ( + shaped slits). This still allowed the screws to go through the mylar so that we could use them for alignment of the two shields. This again was to make sure that no small pieces of Al would be able to form a conductive path between the two shields.

Following the revised procedure stated above allowed us to construct a non- conductive endplate assembly.

Revised Assembly Procedure

1. Wash rings and shields.

2. Used TraBond conductive epoxy to adhere the Al shields onto their corresponding Aluminum "D" rings and let dry overnight.

3. Adhere dry adhesive onto shields, opposite of the side with the "D" rings. Cut the adhesive to the size of the ring. Roll adhesive to remove any bubbles and then cut adhesive away from all holes in shields.

4. Take 1/4 mil mylar, lay flat and stretch onto a table and adhere to larger ring. Cut the mylar to the size of the ring and cut from the holes in the shields.

5. Using screws in the four screw holes in the shields, aligned the inner and outer shields and then adhere them together.

6. This gave a non-conductive endplate.

The endplates did not have the air cooling holes in them for the enclosure environment. These were drilled using our machine shop milling machine for future use when we test the enclosure air cooling system at a later time.

The screws holds in the shields did not have a non-conductive buffer between the screw and the shields. Even though the shields did not conduct after our revised assembly procedure, adding the screws to the holes did make them conduct. A non-conductive material must be placed between the screws and the endplates to ensure that there will be no conduction between the inner and outer shields. References

1. An Experimental Investigation of an Air Cooling Scheme for the Multi-Chip Modules of the Multiplicity and Vertex Detector
   John Bernardin, Eric Bosze, Jehanne Simon-Gillo, Jan Boissevain, Debbie Clark

2. An Experimental Investigation of Air Flow Induced Vibrations within the Multiplicity and Vertex Detector
   John Bernardin, Eric Bosze, Jehanne Simon-Gillo, Jan Boissevain