1. Introduction

Rohacell is susceptible to changes in the relative humidity of the surrounding environment. This note establishes the quality control and assembly procedures for the Rohacell. These procedures must be followed to minimize the changes in the Rohacell as the C-cages are being machined, the silicon detectors are being adhered to the C-cages, and when the MVD is being assembled. These procedures will ensure that the C-cages remain as close to the original dimensions as possible from the time of machining of the cages to the assembly of the detector.

2. Gluing the Rohacell Blocks

To make the correct size C-cages, two Rohacell blocks must be glued together and machined. A list of materials needed for gluing is listed below.

The instructions for gluing the blocks together follows.

• When gluing Rohacell blocks together, one needs to wear gloves at all times.

• Gluing of the blocks is done at room ambient conditions. There are no special environmental conditions.

• From the 2 inch thick Rohacell sheets, cut 100 blocks with dimensions 8 x 3 x 2 inch³. This will yield 50 C-cages of the dimensions 8 x 3 x 4 inch³. Breathing masks should be worn when cutting the Rohacell.

• On the table you will use to glue the blocks on, lay down some craft wrapping paper. This will protect the surface of the table from glue that might drip down the sides of the Rohacell blocks and avoid the blocks being stuck to the table.

• Using a paint brush, take a block of Rohacell and brush one of the 8 x 3 inch² surfaces of the block until excess flakes are removed. Repeat this procedure for each block, making sure you know which surfaces are brushed. The brushed surfaces will be glued together later.

• Araldit 106/953 [1] two part epoxy will be used to glue the blocks together. Make sure to wear gloves and mix the epoxy in a well ventilated room or under a fume hood.

• Mix, in a graduated coffee cup size plastic cup, a large amount of epoxy with a 1:1 ratio between part A and part B of the epoxy. Do not fill the plastic cup all the way to the top with epoxy. You will need to stir the two parts of the epoxy together.

• Stir the epoxy vigorously for 15 to 20 minutes using a wooden stick, scraping glue off the wall of the cup as one mixes. The final color of the epoxy will be a light yellow. You will have approximately an hour to use the epoxy before it becomes like taffy and unusable.

• Once done mixing, use the wood stick to spread a thick uniform layer of Araldit over one of the brushed surfaces of a block of Rohacell.

• Put another brushed surface Rohacell block on top of the one with the glue layer.

• Precaution: Be careful when using lead bricks. Put plastic gloves over the latex gloves you are wearing so that the latex glues do not get lead on them. Only use latex gloves when handling the glue and Rohacell blocks.

• Center a lead brick or other heavy object on top of the glued blocks and square the Rohacell blocks to one another. The weight of the lead bricks will ensure that the epoxy will work its way into the Rohacell and make a strong bond between the two pieces.

• Scrap away any excess glue that is dripping down the sides of the blocks.

• Repeat for other blocks.

• Let the blocks sit on the table with weight on them, and let them cure for at least 48 hours in a room at ambient room conditions.

• After 48 hours, remove the weight. Rohacell blocks are now ready to be machined.

3. Machining and Quality Control at UC Riverside

3.1 Machining Cages at UC Riverside

Machining of the C-cages will be done at the University of California, Riverside, Department of Physics, Machine Shop. The materials needed by the machine shop staff when the cages are being made are:

• The average relative humidity of the UCR Machine Shop is between 20 and 40%.

• During machining, latex gloves should be worn in order to keep oils from the hands from getting onto the Rohacell. The machinist should also wear a mask to protect themselves from breathing the Rohacell dust.

• A large environmental chamber will be supplied. The chamber will be preset to the conditions in which the MVD detector will be operating at, namely at 30% relative humidity (R.H.). The tolerances will be determined by the chamber itself, but should not fluctuate more than 5% R.H., or 1 ^o C.

• Before machining is to begin, make sure the chamber is working properly for a week, writing down twice a day, once in the morning and once in the afternoon in a log book, the temperature, relative humidity, the date and the time of measurment for the environments inside the chamber and outside the chamber. A temperature/humidity device (supplied by LANL) should be placed outside of the environmental control chamber. This is to make sure that the chamber is working within the tolerances specified by the company we purchased the chamber from.

• Once satisfied that the chamber is working properly, place all 50 glued Rohacell blocks in the chamber. Leave them in the chamber for 1 week before machining is to begin. This will help to bring the moisture content of the Rohacell into equilibrium with the chamber environment. After sitting in the chamber for a week, blocks are now ready to be machined.

• When cages are not being machined, they need to stay inside the environmental control chamber. This will ensure that the cages are always in equilibrium with the operating conditions of the MVD.

• The machinist should once a day write down the temperature and relative humidity inside and outside of the chamber in the log book. This needs to be done in order to make sure the chamber is working correctly, and note any large deviations from 30% relative humidity.

3.2 After Machining

Cages are now sensitive to changes in humidity. Cages should not be touched with bare hands. So, precautions must be taken after the C-cages are machined from the Rohacell blocks. The one precaution that should always be take is:

• Once all cages are finished, they need to be brushed down to remove excess Rohacell dust. A breathing mask should be worn for this procedure.

• Taking one cage out of the environmental chamber at a time, take a small, teflon paint brush, and carefully but vigorously, brush all surfaces, inside and out, until little to no flakes are seen coming off.

• Place cages back in chamber until ready to weigh and measure the various dimensions according to the steps in the next section.

3.3 Before Shipping to be Coated

Before shipping the cages for Parylene coating, measurements must be taken. The materials needed are:

• Go to this web site to download and print the template that you will need to record the measurements of the cages: Click Here Print the template in landscape.
  Once you have printed this template, follow the directions below.

• You will need one template for each cage. On the template, mark down the cage #, the date you are taking the measurements, and your name.

• Next, write down the temperature and relative humidity inside the environmental control chamber as such, 20 C at 30% R.H., in the space provided. Do the same for the outside environment. You are now ready to take out a cage, and begin measurements.

• With a glove on, take a cage out of the environmental control chamber and number the cage with a black pen, making the mark as dark as possible. See figure 1 on where to make the mark. Number the cages 1 thru 50.

• After marking the cage, you need to weigh it and measure the various dimensions. Using a scale with 0.001g accuracy, weigh the cage and write the weight in the space provided on the template.

• Using the 10 inch calipers, start measuring the various dimensions. It is not necessary to wear a glove on the hand holding the calipers. Just be careful not to touch the cage with the bare hand. Measure the dimensions in the order listed on the template. See figure 1 for where the various dimensions are located.

• Measure each dimension 5 times, except for Length 2 and the Mass. To do this, measure the dimension once, remove the calipers from the dimension you are measuring, opening them up a little bit, and then measure the dimension again until you have 5 measurements.

• Write down the five measurements you made for each dimension on the template, being very careful to write down the correct measurements for the correct dimension.

• Measure Length 2 only once with a ruler that has millimeter markings. Measure the distance between the holes on one side of the cage using the ruler and write down the measurement.

• Once done, write down the time you were done measuring the cage, then put the cage back into the environmental control chamber.

• Calculate the Average for each dimension for that cage to 0.1 mil accuracy.

• Put the template for that cage into the binder. Repeat the above steps until all cages have been measured, weighed, and the template for each cage put into the binder.

• Put the data from each cage into the database. Instructions on how to do this will come later.

• Once all cages have been measured and their dimensions recorded, they are ready to be shipped to the Parylening company.

• Leave cages in environmental control chamber for about 1 week before going on to section 4 of this note on shipping to the Parylene company.

• Make a copy of the binder with the C-cage measurements. Make another binder for these copies and leave them at UC Riverside. Send the original binder and the log book that was used to write down the temperature and humidity measurements of the UCR environmental control chamber to Los Alamos. Send them to this address:

3.4 What to do with Bad Cages

Rohacell foam is hard to machine. Cages that are not made to the right dimensions, should not be shipped to be Parylene coated. Here is how to determine which cages should not be shipped.

• The width of the cage is 53.2 mm (2094.5 mil). The tolerace on this dimension is +/- 0.025 mm. If the cage does not meet this spec, do not ship it to be coated.

• Another important dimension is the length. Length 2 is suppose to be 140 mm long. The tolerance on this dimension is +/- 0.05mm. If this is not met, do not send the cage to be coated.

• The tolerances on the ribs of the cage are pretty loose. Please refer to the drawings for this tolerance.

3.5 Calculating the other Measurements (Optional)

If you are bored, you can calculate the other measurements that you left blank on the templates, namely the standard deviation, the deviation², the % change, and the % error. You can either use a calculator, or input the data into Excel.

Here are the equations to calculate these other measurements:

• To calculate the Dev², subtract each measurement from the average, square each subtraction, and then add the squares. To calculate the Standard Deviation, take the Sqrt(Dev²/n-1).

• To calculate the % Change, do this like you normally would, (Final Measurement - Initial Measurement)/(Initial Measurement). Make sure to round this number to the nearest hundredth of a percent. You should get 0% change for these numbers.

• To calculate the % Error, follow this example:
  (Final Average)/(Initial Average)*[{(Standard Dev.)/(Initial Average)}² + {(Initial Standard Dev.)/(Initial Average)}²]^0.5.

• Record these numbers onto the template for each cage.

• These templates will then need to be put into a database via the web. Follow instructions once this has been established.

4. Shipping to Parylene Company

The cages are now ready to be sent to the Parylene company. Below are instructions on how to prepare the cages for shipping. The materials needed are:

• Take a cardboard box and put a layer of packing material on the bottom. About 2 inches will do.

• Wearing gloves, take only one cage at a time out of the environmental chamber, and follow the instructions below.
  • Place the cage into a large ziplock plastic bag and seal the bag.

  • Put the sealed cage into the box, the open face facing down. Do not put cages close to the ends of the box. Leave about 3 to 4 inches. Then, put cardboard sheets on either side of the cage.

  • Take the next cage out, put it into a plastic bag, seal, and put into the box next to the last one. Put a cardboard sheet next to the cage.

  • When box is full of cages, place more packing material on top of the cages and around the sides. Make sure that there is about 3 to 4 inches from the top of the box to the top of the cages. This will be adequate for protecting the cages during transport.

  • Repeat again until all cages are placed in plastic bags and packed into the boxes.

  • In each box, place a list of the cages that are in the individual box. Click here to download and print a template for the list you should put in the each box.

  • Seal boxes with packing tape. Try to cover all openings in the box with tape, as to help prevent moisture from seeping into the boxes while during transport.

  • Send to the Parylene company via UPS. Insure each box for $300. The parylening company's address is:

5. Quality Control at Parylene Company

This is a separate document that will be presented to the Parylening company.

6. Quality Control at Los Alamos National Labs

Once cages are coated, they will be shipped to LANL. Below are instructions on how to handle cages when they come back from Paratronix. The materials needed are:

• While cages are being coated, make sure the environmental chamber is working properly, making measurements twice a day, once in the morning, and once in the afternoon. If chamber is working within the manufactures specs, it is then ready for the cages. Put measurements in the log book that was shipped from UC Riverside.

• Once cages arrive, leave them in the boxes until ready to unpack them.

• With gloves on, start taking cages out of the boxes and put them into the environmental chamber. While unloading, check the list of broken cages against the cage themselves.

• Leave cages in the environmental chamber for 300 hours, and then measure the various dimensions and weight. Do this the same way as stated in section 3 of this note.

• Once all cages are re-measured, calculate the other measurements as stated in section 3.5 of this note.

• Once this is done for all cages, compare each cage to accepted tolerances. Mark down on each template for each cage whether or not it is a good or a bad cage.

• Since it is reasonable to assume that cages will be left in the environmental chamber for quite a while before putting the detectors on them, once a week check that environmental controls are working properly, and take a random selection of about 5 cages, and weigh and measure them. Input data as always and mark down any large changes.

• The cages should be in the environmental control chamber for at least 300 hours before gluing can begin.

• Periodicly, one should input the data from the cages into the database. Follow the instructions on how to do this when this procedure is established.

7. Adhering Silicon to Cages

This will be a separate document.