Designing a cryostat for Simons Observatory

A small number of us from the Simons Observatory (SO) cryogenics working group met at the University of Pennsylvania this week to dig into the beginnings of design requirements for the large-aperture telescope’s cryogenic receiver. The sheer size of this cryostat (~2.5 meters in diameter) makes it an exciting design challenge. It will house the optics and detector arrays for the large-aperture telescope of the Simons Observatory, enabling the pixels at millikelvin temperatures (that’s near absolute zero!) to detect photons from the Cosmic Microwave Background (CMB). You can read more about the science we’ll do with SO here.

Our work was fueled by the great eateries and food trucks that surround the UPenn campus, as well as numerous coffees in turquoise blue cups from Joe. You can spot one of mine in the group photo.


Simons Observatory Cryogenics face-to-face meeting. From left to right: Andrew Bazarko, Bob Thornton, Simon Dicker, Marius Lungu, Ningfeng Zhu, Michele Limon, Eve Vavagiakis, Nicholas Galitzki, Grant Teply, Logan Howe, Gabriele Coppi. Thanks to Gabriele for the neat GoPro shot.

I’m focused on spacing requirements for the optics tubes which will go into this large cryogenic receiver. These requirements include magnetic shielding which might be necessary for our sensitive superconducting detectors to function properly. I’m currently working on measurements of magnetic sensitivity of these devices to learn more about how much shielding we’ll need. Beyond this, I’ll be working with engineers here at Cornell to test vacuum window mechanical designs. These vacuum windows would be on the outside of the cryostat at room temperature, and the CMB photons will pass through them to get to the optics of the receiver (which get colder and colder as they go), until they finally hit the detector arrays, which we read out to record our signals.

Until next time, Philly!


My view from the DoubleTree Hotel