Installing the Tower

Installing the tower generally takes 3-4 hours, and most of this is due to the care required with inserting the screws by hand. Many of the screws are steel and we are inserting them into threaded copper, so we have to be careful not to strip the holes by forcing them in with drivers. There are 4 stages to be installed: 30 mK (with tower), 100 mK, 600 mK, and 4 K. To be properly equipped for the installation, bring the blue tool box, the clear screws box, and the clear box containing stage components into the mini clean room. Also bring the three-prong stand with the tower attached to it and the bag that has the components to attach the stand to the IVC flange properly. When you reach the 4 K stage, you can bring that stage from the anteroom (wrapped in its ziploc bag).

Clean the flange again using the same method described earlier. There will be some indium residue left from the plate that was attached to the IVC flange to install the tower, and this needs to be removed.

This first stage involves attaching the tower to the 30 mK stage via the adapter plate and connecting the thermometer.

1. Attach the aluminum plate to the bottom of the upper IVC flange. There are screws in the bag to do so. Make sure that the large holes in the plate align with the holes in the top of the mini clean room because, in order for the stand to be lifted properly, the prongs must go through the holes in the aluminum plate and the clean tent.
2. Insert the threaded rods down through the holes in the aluminum plates. Make sure the larger side of the knob is not flush with the aluminum plate. These rods, once screwed in, prevent the stand from falling.
3. You will now lift the stand-tower combination. Before doing so, you have to be careful and mindful of several things:
   1. The orientation of the tower as you guide it into the IVC is important. Before actually raising the stand, rotate it on the ground such that the side coaxes, when lifted, won’t be completely parallel to the direction of the striplines. Connecting the SQUET cards with striplines is more difficult in this orientation. You also need to make note of the orientation so that you know where to plug in the appropriate SQUET cards into the tower. Lastly, you want to be sure that when you fasten the tower inside of the IVC that the 600 mK rod will connect with an ear on the 600 mK stage of the tower. If any of the things mentioned above are not noted or prepared for, you will have to take out the tower and re-do this step properly.
   2. Be careful of the tower hitting the 600 mK rod. Gently push the rod away from the tower as you push up the stand.
   3. Keep an eye on the thermometer wires to make sure they don’t get accidentally caught in the tower or crushed. Lift the stand and guide it so that the prongs move through the holes in the plate and thread in the threaded rods to the holes in the stand.
   4. If you’ve secured all of the threaded rods properly, the stand should now be supported by the upper IVC flange. Now insert by hand the M3x25 stainless steel screws to fasten the adapter plate to the 30 mK can. Only tighten them finger-tight.
4. Use the torque driver to tighten the screws to finish tightening them. The torque driver ensures that we don’t over-tighten the screws. You don’t need to adjust any settings on the driver, which should always be at 5 (f)lb inches, but you might have to change the tip. Make sure it’s the balldriver tip.
5. Now that the tower has been appropriately fastened, you can begin the removal process of the stand structure. First, unscrew the screw that attaches the cylindrical rod within the tower to the stand.
6. The stand is no longer attached to the tower. Start loosening the threaded rods that are holding the stand against the bottom of the IVC. You can either pull out the threaded rods completely or just rotate the knobs counter-clockwise to lower the stand gradually.
7. Once the stand is out, remove the threaded rods from the aluminum plate.
8. Remove the aluminum plate.
9. Gently unscrew the cylindrical rod from the tower.
10. Now you need to connect the mixing chamber thermometer. If the connection is okay, the resistance should read 1 kΩ at room temperature.
11. The thermometer is hanging freely which can create problems if left this way during the run. Thermal shorts can occur if the thermometer touches a stage that it shouldn’t. Thus, you need to tape it down to the 30 mK can.
    1. Wrap a small piece of kapton tape around the thermometer connection so that it circles the joint 1-2 times. We don’t want this connection to separate during the run!
    2. Wrap the thermometer wire around the 30 mK can and secure it down with pieces of kapton tape in different places. Make sure that the thermometer and/or the wire won’t touch the 100 mK stage. Note that in the uninstallation process these pieces of tape have to be removed, so try to not place them in really high, awkward positions within the IVC.
    3. Once you’re satisfied with the positioning of the thermometer, place strips of copper tape over the kapton tape you’ve placed on the wire to make the positions held more secure (kapton tends to fall off during the run). Ensure that the copper tape is in contact with the 30 mK can as well or else it will fall off when the kapton tape does. Don’t put copper tape on the thermometer connection, though.

This stage consists of attaching halved copper rings and heat sinks to the 100 mK can and the tower. On the tower a few of the ears where the rings and heat sinks could possibly connect to are stripped, so you will need to be aware of them before you try to screw anything in there. There will be one hole in which a screw cannot be inserted at all.

1. From the clear box with fridge stage components, pull out the ziploc bags that contain the halved copper rings. Pull out the two larger rings. You will connect these to the 100 mK can first.
2. First attach the copper ring with the rectangular hole in it. That hole is to allow the ring to surround the 600 mK rod without touching it. Maneuver the copper ring so that the hole surrounds the rod, and screw in by hand the small M3x5 steel screws. Once that ring is positioned in place by several screws, attach the other copper half ring.
3. You will now put on the inner copper rings. Three of the holes through these copper rings are going to have heat sinks attached. Thus, you need to identify which of the ears on the tower at the 100 mK stage are stripped. One of the stripped holes can be used since it’s not entirely damaged. Two heat sinks can be positioned next to each other, but the third heat sink needs to be at least one space away. Use a steel screw to test each threaded hole to identify which are stripped and to what degree. DO NOT force the screw in - the moment you feel resistance bring the screw back out.
4. With the inner copper rings positioned in place properly, in three of the tower ears you’ve found acceptable install the three heat sinks using the M3x8 or M3x12 screws. You will need the M3x8 for the partially stripped hole. BE VERY CAREFUL that the screw enters vertically or you WILL strip that hole. Also, make sure that the heat sink on the tower doesn’t touch the face of the tower at all or you will short thermal stages together.
5. Attach the other end of the heat sinks to the 100 mK can using the M3x8 or M3x12 screws. If you already put all the screws in the perimeter of the can, remove three so that you can attach the heat sinks. Make sure that these ends of the heat sinks are oriented such that they don’t hit the IVC.
6. Now that you’ve attached all the heat sinks, finish fastening the smaller copper rings with screws into the tower ears.
7. Torque all of the screws on the 100 mK stage. Be warned that torquing the screws in the heat sinks on the tower are going to be a difficult, so you might have to push hard into the screw head and turn.
8. Notice the thin line gaps between the halved copper rings. Place copper tape on the thin line gaps. In placing the copper tape over these gaps, be careful not to create any thermal shorts by accidentally touching the IVC with the copper tape.

The 600 mK stage consists of a copper rod that’s attached to the still plate on the fridge, then fastened to the 600 mK stage of the tower.

1. Screw in a M3x8 brass Phillips head screw in the short leg of the copper rod and attach that to the nearest ear of the tower. Torque this screw.
2. Notice the gaps in the 100 mK shield around the 600 mK rod. Place copper tape over the gaps around the 600 mK rod without touching the rod itself. If you do, you will be creating thermal shorts and that is a huge problem!

The 4 K stage is the last one in the installation process. During this stage’s installation, you will need to do a quick check once you connect the SQUET cards to make sure things are okay. Depending on how many DIBs are being utilized in the run, you may need to use all three striplines. It’s important to be aware of the orientation of the side coaxes so that you can plug in the SQUET cards into the appropriate spot. You should decide ahead of time which SQUET cards will be associated with which DIBs and striplines. Note that all of the screws used in this stage are brass!

1. Bring the 4 K stage from the anteroom into the little clean room and unpack it from the ziploc bag.
2. Screw in the spool cap (goes into the center of the tower) with a 0-80 flat head screw. One of the holes is blocked. You only need one screw to keep the spool cap in place.
3. Attach the 4 K stage to the IVC by inserting the brass M3x5 phillps head screws into the outer perimeter of the stage.
4. Pull out the SQUET cards from the clear plastic box. Identify the SQUET cards properly by looking for the engraved number on the upper right hand corner (23, 28, or 70).
5. Attach the correct stripline to the SQUET card. Note that the striplines will have numbers engraved on them as well (19, 20, or 21). Be very careful to make sure that all the pins are positioned within the sockets before squeezing the boards together or you’ll bend a pin. You can use the two pins at the top of the SQUET card to guide the orientation of connection.
6. Now insert the top of the SQUET card into the tower in to the appropriate position (determined by which sidecoax you want to connect to). If you’ve inserted the SQUET card correctly, the card should stay in place without the support of a screw.
7. Secure the SQUET card to the tower with brass screws. You will need one phillips screw and one socket head screw, both M3x8. The M3 screw goes above the flyover cable (if you are inserting more than 2 SQUET cards, you should torque these screws right away. Make sure to change the torque driver tip so that it acts as a balldriver).
8. After inserting all the SQUET cards, at the breakout box, do a quick resistance check to make sure that connections, cards, and striplines are okay.
9. Screw in the SQUID components of the SQUET card with the M3x5 screw. Ensure that the SQUIDs are flush against the tower. You may have to loosen the spool cap to achieve this.
10. Attach the copper shield plates with M3x5 or 8 screws. Use copper tape to further press the shields to the 4 K stage.
11. Screw in the heat sinks using the M3x8 screws. There is ONE heat sink hole that is stripped so if you feel resistance be careful with that hole and test it thoroughly to make sure if it is fine or stripped. Be aware that it is not hard to strip the holes that the heat sinks go into because the heat sinks tend to twist and angle the screws as they get entered.
12. Torque all the screws with the torque driver using the Phillips head. If you haven’t torqued the M3x8 screw above the flyover cable yet, then change the head on the torque driver and torque it.

Before finishing the 4 K stage, an electrical should be conducted at the breakout box to make sure all of the SQUET cards and striplines are behaving as expected (i.e. no open connections in unexpected places). This will be recorded until the 300 K column on the checkout sheet. See Appendix A for instructions on how to conduct the electrical check from the breakout box.