May 13, 2022 - On April 8th, the LSST Camera team at SLAC National Accelerator Laboratory successfully attached the Cryostat to the Camera Body in the IR2 clean room, bringing the camera’s three primary structures—the Cryostat, the Utility Trunk, and the Camera Body—together for the first time. The Cryostat contains the camera’s 201 sensors (each one 16 megapixels), and the 28" entrance lens (L3), with the ancillary electronics and vacuum systems installed on the outside. The Camera Body will ultimately provide support for the camera shutter, filter exchange system, and the two primary lenses (L1 and L2).
In fact, there were four lifts involved in achieving this exciting milestone, all completed in one very busy week. The lifts involved a combination of six custom-built lift and support fixtures, two off-the-shelf spreader beams, and a considerable amount of rigging equipment. All of the custom equipment was designed, assembled, and tested by Camera engineers and technicians at SLAC. The crane lift operations were performed by 3 mechanical engineers and 2 mechanical technicians, all of whom have been involved with the camera project for many years: Andy Hau, Travis Lange, Martin Nordby, Hannah Pollek, and Mike Silva.
The first lift removed the Cryostat and Utility Trunk assembly from its position on the Bench for Optical Testing (BOT). The Cryostat and Utility Trunk were integrated together nine months ago, and then tested as a complete unit on the BOT to verify key requirements for the focal plane sensors and electronics. The assembly was oriented vertically in the BOT and facing down (as it will be when the telescope is zenith-pointed) and the full vertical height of the lift to remove it used all of the available height in the clean room.
Next, the assembly was lowered onto the Cryostat Support Stand, which is a temporary support fixture. The team re-rigged the assembly and tipped it to a horizontal position, using a built-in pivot mechanism in the support stand and the crane to control the motion.
Then, the team moved the Camera Body from the Camera Integration Stand (CIS), where it had been mounted for testing of the filter exchange system, to the Saddle Stand, another temporary support fixture.
The final crane lift involved picking up the Cryostat and Utility Trunk assembly with a C-Hook to balance the load, and then inserting it into the Camera Body. This could be described as the most critical lift of the four, since it involved moving the exposed L3 lens past camera hardware with very tight clearances. In fact, all four of these lifts were considered Category 1 Critical Lifts, meaning they involve high-value, nearly irreplaceable equipment. Beyond the actual hardware to make this possible, and the experienced team of people who carried them out, these operations required considerable advanced planning. This included writing and reviewing lift plans and procedures, then dry-running them, testing them on hardware, and revising them based on the tests. Another key aspect of the process development work was getting review and feedback from SLAC and DOE safety personnel and subject matter experts, to ensure the team had captured lessons learned from other such critical lifts, and were fully prepared for possible problems along the way.
Connecting the Cryostat and the Camera body is the first step in completing integration of the camera. Now the team will work in integrating the power, controls, and purge air systems of the two main assemblies that are now together. Then they’ll lift the entire Camera Assembly back onto the Camera Integration Stand and run final tests on the filter exchange system and camera shutter. The final step in the integration process will be to mount the L1-L2 lens assembly to the front of the Camera. This will mark the completion of the integration process, but the start of a full suite of verification test activities to ensure that the completed camera performs as required.
There may still be a lot of work to do, but it’s important to celebrate success along the way!
Image: The LSST team successfully completed the lift of the cryostat and installation into the camera body on April 8. From left, Andy Hau, Mike Silva, Martin Nordby, Ramsey Razik, Travis Lange and Hannah Pollek. Behind the clean room window is Jeff Tice and Tim Bond. (Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory)