Background: A blog describing our team's adventures installing and commission the new South Pole Telescope third generation camera. This experiment is designed to measure the CMB B-mode polarization, exposing the signatures of gravitational lensing and, perhaps, evidence of gravitational waves from the early universe. The camera, like its predecessor, used readout electronics developed and built by our Lab at McGill. Joshua Montgomery and Matt Dobbs are representing McGill. We’re part of a much larger team that includes our partners from across the USA. Together, we’ll log more than 1100 days at the South Pole, bringing this project to fruition.
Photo: Flights to/from the South Pole have been cancelled for the past week. A gaggle of people has built up, all eager to get home to see their families for the holidays. Finally, on Dec 20, the first plane arrived. It brought McGill grad student Josh Montgomery, and took me out to McMurdo station for the first leg of my trip back North.
Photo: Summer solstice (00:01am Dec 21, 2016) at McMurdo station. Many inhabitants of the 700+ person McMurdo station chose the moment when the sun crests its highest point on the sky with a Dance Party. This was an odd scene for two reasons (1) it has held on the foundation of an abandoned Nuclear Reactor (**, the dance floor pictured here), looking out over the edge of the continuent, (2) each person brought their own music and headphones. Unlike a normal dance floor, it meant that everyone was moving erratically with respect to one another. When you took your headphones off, it was completely silent, other than the tap and shuffle of feet.
(**: The PM-3A nuclear power plant was erected in February 1962 by the Navy and turned on in March (wow, I wish we could commission a telescope that fast!). It produced 1.8 MWatts at 72% availability. It was shut down in 1972 (I think the Antarctic treaty forbids nuclear reactors), and the site was fully decommissioned and released for use in 1979.
The last week+ has been a whirlwind of activity. The camera cooled to its base temperature Monday morning, December 12, a little ahead of schedule. This was the fastest cooling to date, and caught us off guard by half a day (we were recovering and cleaning up after the Sunday evening open house telescope dance party that has become a tradition, once a year, at the telescope. It’s our way of thanking the station staff for their help and support this season -- more on that later). We scrambled to cable-up and turn on the various systems that control and tune the camera -- and started sleeping a whole lot less
Ready for blast-off! The SPT3g camera, pointed straight up, ready to be hoisted into the telescope cabin for a test fit. It took 11 people a full day to successfully lift and mechanically install the camera in the cabin. The camera is huge and the optics system makes use of all the space in the cabin - at some points, there’s an inch or less of clearance between the cabin wall and the instrumentation. Parking the camera on its mounting points is like trying to park a Winnebago in old Montreal. We did have to remove the cables to get the camera up, but once in place, we were able to cable it back up and it all fit.
Cables, cables, cables. There are always a lot of cables to connect. Cabling is a chore, usually undertaken from awkward positions. Everyone jumps in to cable - so no one has to suffer alone. Sometimes it’s a little humorous, with a dozen hands reaching in to try to do the work that is easier done with one.
We rarely get penguins all the way in-land at the South Pole, but sometimes it happens.
Photos: (left) Chicago Grad-student, Joshua Sobrin, opens the telescope control room roof to give the SPT3g camera it’s first glimpse of the sky. (right) Brad Benson uses his super-human strength to rotate the 2400 lbs camera up. Before mounting the camera in the telescope, we test its loading and performance looking out at the open sky.
After trudging back from the telescope after working late, despite being dead-tired, it’s not always easy to turn a switch and sleep. Fortunately, the South Pole Station is equiped with a Sauna. (what? The coldest establishment on earth has a sauna? - isn’t that wasteful? No, not really. The sauna is in the middle of the building. Sure, a lot of energy is spent to heat it up, but when that heat escapes, it escapes to the rest the building.).
Our crew will often head to the sauna late at night, to chill out before bed. But no sauna is complete without a pole run. A half-hour or so in the sauna, then straight outside (don’t forget your shoes), and a sprint to the geographic pole in your skimpy’s.
Photo: The pole run. This particular run was extra-cautious, because this year we have a more-adventurous-than-usual station doctor - “Doctor Dave”, who accompanied the run.
Photo: the SPT crew at the pole-marker, on a particularly windless and warm (-30C) day.
Photo: another crowd-pleaser at the South Pole is open-mic, where rag-tag bands assemble and normally play classics with lyrics adapted for the antarctic environment. Here Waste-Bill, IT-Ryan, and station manager Bill perform (I think they were playing Neil Young’s “everybody knows this is nowhere”).
Photo: Out for a run - you need a little more gear than normal. I wear a wicking shirt, a wool shirt, a thin down sweather, and a wind layer on top. running socks, wool socks and regular running shoes on my feet. Thin long underwear and softshell pants. Goggles, balaclava, and mittens. In addition, I carry a lot more emergency gear than I would anywhere else: a radio to communicate with the station if need-be, an "In-reach" personal locator beacon that allows me to send text messages or SOS through the iridium satellite network in case the radio fails, and chemical hand-warmers in my pocket to keep my fingers and toes safe from frostbite if I have to stop and wait for help. Oh, and an ipod full of music, of course.
My run took me out past “The End of the World” - this is where the fuel is stored in train tanker-like vessels that are mounted on skis - well away from the station, just in case the unthinkable should happen. In an upcoming post I’ll take you on a tour of the South Pole Power Plant, which burns about 48 gallons per hour to keep the electricity (650 kW - about 1 CHIME!) flowing that is needed to power the Station’s science and operations. (pop-quiz for my former Energy and the Environment students - do you think the station needs to spend any energy at all to heat itself?)
About a hundred miles away the first South POle Traverse (SPOT) of the summer is making its way towards us. They are driving overland in Caterpillar trackers, equipped with large tank-like tracks and Piston-Bullys (the type of machine that grooms ski slopes). It’s a crew of 10 that has embarked on the ultimate road trip. Driving from the open ocean, where they have filled large plastic bladders with fuel, and dragging them across the continent to the station. It’s a month-long expedition one-way. It provides the Antarctic program with the efficient way to bring fuel to the South Pole that is needed to run the generators that power our science infrastructure (and keep us warm!). We expect them to arrive within a day or so. They usually show-up a little stir-crazy, taking in the wild luxuries of an equipped station.
It’s been a busy week - with all our cargo in hand since Monday, we’ve been scrambling to put it all together. We typically gather at 8am to outline the day’s tasks and divvy up responsibilities. We trek out to the telescope (about a km walk) and work three blocks (morning, afternoon and evening), jogging back to the station for our meals. We scoot back around 11 or 12 pm to catch a little communications time through the satellite (that’s how these blog posts get to you!), and check in with the rest of the team back north, before sleeping and starting over.
After 6 days of scrambling, we’ve reached the first milestone - the SPT3g camera is assembled! The next steps are to pump it down to a good vacuum (this takes about 2 days), and then begin cooling it, which takes another 5 days. This gives us some time to catch up on everything else and put our ducks in line for the first system tests that will start as soon as its cold.
Here are some photos of the instrument and team.
Amy Bender (Argonne National Lab, formerly a McGill postdoc) and Matt Dobbs (McGill) assembling the cryogenic wiring for the focal plane.
The team working on assembling the optics tube. The entire camera weighs about 2400 lbs - so it's a delicate mix of ultra-sensitive components that are assembled into huge mechanical structures that require chain hoists and cranes to manipulate.
The focal plane of the South Pole Telescope 3g camera. Presently we have installed 2 of its ten detector modules (the white arrays, with electronics sitting behind). Each of the white items, barely discernable in the photo, is a pixel. The white object is a small lens that focuses light down onto a small, micro-fabricated antenna. There is one antenna for each polarization of light. After the antenna, the electromagnetic wave travels down a trace and is filtered according to its wavelength. The energy from the a particular color, of a particular polarization is deposited on a small piece of metal - a superconductor held in its transition - which heats up. We measure the temperature change of the superconductor and use this to figure out how much light is coming from a particular region of the sky. The superconductors are kept at about half a degree above absolute zero and the temperature changes are small - micro-degrees.
Joshua Sobrin (Chicago Grad-student) in front of the fully assembled SPT3g cryostat that he co-designed. In many ways, this is kind-of the lamborghini of mm-wavelength cameras.
The crew at the South Pole (Adam Anderson, Brad Benson, Amy Bender, Matt Dobbs, Kyle Story, Jessica Avva, John Carlstrom, Joshua Sobrin, (Robert Guysler is not in this photo)) late night December 3 after closing the cryostat for its first cooldown. (Photo by Kyle Story).
The remaining essential components for the SPT3g camera arrived after many cancelled flights on Monday, so we’ve started working long days to put the camera together and catch up on the time we’ve lost. The team is enthusiastic and everyone is enjoyed the go-go-go attitude.
(left) Kyle, that’s a really big torque wrench. (middle) It’s like Christmas here, as we wrap key areas of the camera interior with aluminized mylar to make an radio-frequency shield that protects the most sensitive components from stray radio signals.
(right) Brad keeps receiving bulk shipments of 5lb candy bags from an anonymous sender for the team. Much of this work is fueled by Gummy-calories. Thanks, whoever you are! (Yes, Amazon delivers to the South Pole through the USAP postal service).
Photos: McGill designs and builds the detector readout electronics for SPT3g - top left is a crate of boards, capable of reading out about 8000 detectors (that’s a lot by 2016 standards!). Top right and bottom are circuit boards housing the cold superconducting readout hardware - these boards are co-designed by Argonne National lab and McGill. At McGill, engineers Adam Gilbert, J-F Cliche, and Graeme Smecher (who won the South Pole half-marathon a few years ago) are part of the behind-the-science special sauce that make these systems work so well.
Photos: (left) Brad Benson and Adam Anderson (Fermilab) hoist one for the SPT3g lens for installation in the camera. The lens is the white surface - it looks opaque to you, but is very transparent to millimetre-wave light. (right) The SPT3g camera, with one lens installed, and the first section of the optics tube.
The Antarctic Services Contract folks at the pole work 6 day weeks providing support (the fuelies, UTs, carps, sparkies, galley staff, etc.) [translation: the ones who fuel the planes/generators, utilities technicians who keep the power plant going, carpenters, electricians, restaurant staff…], but on American thanksgiving, they get saturday off. So, naturally, the whole station comes together to throw a big party.
It’s important to get dolled up for the party. Our South Pole Telescope crew definitely raised some eyebrows with our fine dress, scavenged from the SKUA (free stuff shack, named for the scavenger bird that is native to antarctica), and modified in the craft room by Berkeley grad student Jessica Avva.
The SPT crew at the South Pole, dolled up for formal thanksgiving dinner: Matt Dobbs (McGill), Kyle Story (Stanford), Amy Bender (Argonne), Adam Anderson (Fermilab), Joshua Sobin (Chicago), Erik Nichols (Chicago), Jessica Avva (Berkeley), Brad Benson (Fermilab), John Carlstrom (Chicago), Robert Guyser (Illinois).
Brad, Jessica, Erik, Joshua (Sweta is his wife, don’t worry), and Adam (yes, that’s a 1985 bottle of port, imported from Portugal to Cambridge to the USA to New Zealand to the South Pole - thanks for sharing Adam!).
The Galley, decked out for Thanksgiving and the evening’s menu, prepared by chef Big Country (yup, that’s what he's called).
After dinner, the SPT crew retired to the music room - where we had quite an eclectic mix of instruments and found that all ten of us could play (or fake) something.
Turns out Cream’s “Sunshine of Your Love” sounds pretty good on the tuba.
Sundog above the South Pole (left), and the trail (right) groomed to make a perfect 8 km out-and-back running track (-35C isn’t that bad for running if its dry and the wind is low).
(left) SPT team-member Dr. Amy Bender, from Argonne Labs (formerly a McGill Cosmo lab postdoc) with an SPT3g detector focal plane element. Ten such elements tile the camera's focal plane. Each element has about 1,600 detectors, making a single element as powerful as the previous SPTpol camera was.The white "lenslets" focus microwave light onto polarization sensitive antennas. The light received by the antennas are sorted into different frequency bands (or "colors"), and the power is absorbed in a bolometric detector. Behind the detectors sits the multiplexing electronics. All of this hardware is cooled to 270 mK in the SPT3g cryostat.
(right) Brad Benson (Fermilab) and John Carlstrom (Chicago) prepare an SPT3g lens. The lens is cooled to 4 kelvin.
The SPT team sets up the optics bench that will house the secondary and tertiary dishes of the telescope, with the help of a station digger. The bench is too big to bring into the telescope building, so the work is taking place outside and in the blue Jamesway tent. Handling metal objects at -40C is character-building.
Photos: there's usually an hour of so of downtime after dinner each night before the satellite comes up and we can start communicating with the north and looking up all those things that remind us how dependent we are on the internet. The climbing gym, hidden out in one of the shacks behind the station, or the music room, are favourites.
Photos: Kyle Story disassembles the superconducting detectors and quantum interference amplifiers from the old SPTpol camera, readying it for redeployment back to the USA. (right) Joshua Sobrin polishes the new SPT3g camera’s cryostat, to remove any residues that may jeopardize its vacuum. This cryostat will cool the SPT3g detectors to 280 mK (about - 273C). It’s cold outside here, but its really cold in that cryostat!
Friday November 18, 2016 - The South Pole