For the last week or so my advisor, Nils Halverson, has been down at the Pole with the rest of the SPT crew. He brought down his slick Nikon camera and an incredible wide-angle lens and has been snapping some truly impressive photos of all the things going on down here. There’s a lot more happening than just putting the receiver together, (not to mention a huge crew doing all the work. We currently have 18 people at Pole for SPT). Nils’ pictures show that and he’s agreed to let me share some of his photography with you. Just pictures and captions in this post (and a few pictures of me actually working and not just standing or posing!). Enjoy! And please please please open up the full-sized pictures. It's worth the extra few moments to download them.
Dale Li (right) came down with Nils. Dale is the miracle worker that fabricated all of the NIST 150 GHz wafers. He worked 18-hour days for months to finish all the wafers we needed and they’re just awesome. I’m describing how we use a sheet metal reflector to do sky measurements without having the camera installed in the telescope. The roof in the control room is open and the telescope is looming in the background facing away from us.
A shot of SPT facing away from the station with the wide-angle lens. If all goes well in about a week we’ll be lifting the secondary and receiver cryostats into that boom on the far right to start on-sky testing using the telescope.
Another sundog behind SPT.
Abby and I opening up Black Cat after the first cooldown.
Obligatory shot of me in front of SPT with the new guard ring.
Brad working on the secondary cryostat. The spacey shiny stuff is aluminized mylar super-insulation. It acts as a radiation blanket, absorbing radiation and re-radiating it in two directions, chopping the intensity of the re-radiated light roughly in half. By having 20 or so layers of super-insulation you keep the hotter outer vacuum jackets from heating up the cooler inner jackets with their hot IR radiation.
Bill pointing out something screwy with the heat straps to the pulse tube refrigerator in the secondary cryostat. There is another refrigerator just like this in Black Cat that gets the camera down to 4K. Then we use another fridge that uses a combination of evaporating Helium 4 and Helium 3 to cool the camera to ~ 300 mK.
Bill and Brad working on fixing the heat strapping in the secondary cryostat.
Liz inspecting a metal mesh filter after being re-clamped. The filters chop off high frequency light to reduce the amount of power the detectors see. There are many filters in the system, each cutting off at a successively lower frequency. The last set of filters defines the upper edges of our observing bands (the colors we look at).
Me working on one of the 150 GHz modules. These are the modules I designed. I’d make a lot of changes to them if I knew what I knew now when I started, but I suppose that’s the learning process, isn’t it?
From left: Nils, Tijmen, Brad, and Kyle right before mating the two halves of the optics cryostat back together. Mating the halves is a tricky business. There are many layers at different temperatures that aren’t that far apart so alignment is crucial… and it’s all done with four chain hoists.
One of our IR shaders (6 micron thick plastic discs stretched taut) was loose and wrinkly. This is Bill holding up the shader after taking a heat gun to it like a hair dryer to winter window shrink wrap. Nice and tight again!
Abby installing the SPTpol camera into Black Cat for the second cooldown. She did the design work on the focal plane and all the heat sinking. It’s a truly impressive camera!
Liz, myself, and Abby tightening the camera into Black Cat for the second cooldown. It’s probably about 10:00 PM on Monday January 2
in this shot.
Liz and Abby installing readout striplines and clamping them down to various heat sinking points.
Nils wearing the “tiara,” an aluminum and aluminized mylar shield he made to block stray light from filters and IR shaders in the secondary cryostat.
4:15 AM, Tuesday January 3
. The whole crew prepares to mate Black Cat to the secondary cryostat for perhaps the last time.
Brad, myself, Dale, and Tijmen ride on a sled pulled by a snowmobile on our way out to DSL.
A breathtaking shot of the sky behind SPT beyond the new guard ring.
The photographer himself, Nils, working on the boom of the telescope.
Chris and Nils have been working this week to install a “snout” at the opening of the receiver cabin. When we raise the camera into the boom, the window of the secondary cryostat will be where Chris’ head is.
Nils looking down the snout towards Chris.
Dr. “Ill” with his two Berkeley grad students Liz and Nick.
Jay looking at the sky with the sun backlighting.
The other night Kyle climbed up onto boom and then the mirror was tipped to scoop him up so he could climb around on the primary. He then checked all the copper spacer tabs between each mirror panel to make sure none were popping out.
Liz in her winter gear.
Brad on top of the boom with the station a kilometer away in the far background. The building between Brad and the station is MAPO, the site of DASI, the experiment Nils worked on for his thesis. It was also the first experiment to measure the polarization of the CMB.
The SPT crew currently at Pole on the boom directly in front of the primary mirror. (Back) Left to right: Chris, Clarence, Tijmen, Brad, me, Bill, Erik. (Middle) Left to right: Abby, Tyler, Liz, Stephen, Ryan, Kyle, Dale. (Front) Left to right: Nils, Jay, Nick.
The same crew, but a shot farther back using the wide-angle lens getting more of the glory of SPT’s primary mirror.
John Kovac (the first author on the DASI paper that contained the first measurements of polarization in the CMB) took these group photos for us. Thanks, John!
Thanks for the use of your pictures, Nils!