Christmas and Free Time?

I have about a week and a half left at Pole and the tasks the Receiver Team set out to do are about done.  We installed the camera back in the telescope on December 23rd, just in time to start running auto-observing scripts on Christmas Eve.  We’ve been optimizing pixel yield since then and making sure everything looks nominal.  So far, it appears the camera is working better than ever, and should be considerably faster than last year, which was the goal.  (By faster I mean we can see fainter structures in less time observing the sky).

After upgrading the camera we needed to make sure everything was still in focus.  Here's a portion of a map made of a point source at 150 GHz (2 mm wavelength).  The source itself should be a point but the optics of our telescope and camera (the beam) smear it out.  If we're in focus,  at 150 GHz the beam should be about 1 arcminute (1/60 of a degree), and what we measured is bang on with expectations.

On Christmas Eve the annual Race Around the World took place.  This year it was 1.75 miles.  The course started at the geographic pole, headed past the ceremonial pole, and out towards SPT (which by then was in an attractive pose pointing at 45 degrees elevation to show off the fully completed side shields).  Once we got to SPT we took a left towards the Ice Cube Neutrino Lab and then back to the station and around the back side to the finish where we started.  My time this year was 19:38.  Pretty crappy but not too bad (at least for me) considering it was at 10,000 feet, -7 F, and we had to slog through rough patches of snow (but kudos to the station team who set the race up this year.  The course on the whole was in excellent condition).  After the race we all got brunch and were rewarded with nalgene bottles with a cool race logo on it.  Proof I ran around the world!

The map for this year's Race Around the World.  We start and end at the geographic pole, after running through all the longitudes of the world.

The water bottle we got for completing the race.  It might say 2013, but it's still a pretty cool bottle.

Later that evening was Christmas dinner.  The menu was basically the same as last year (beef wellington, lobster tails, a couple choices for mashed potatoes, etc) and as always the food was excellent.  We all have to give it up to the kitchen staff down here - they’re REALLY awesome.

Christmas Eve and Christmas day were the closest we’ve come to days off since coming down here (at that point 5 weeks in) - for me it was just a bit of coding and analysis and checking on some pixel yield issues.  Frankly we didn’t know what to do with ourselves with all of the spare time.  I took a nap, watched some Battlestar Galactica with my colleagues, played the BSG board game a few times and generally just hung out.  It was a nice break.  (And might I add... before coming down last year I bought the BSG board game but didn't get a chance to play it, though I noticed they had a copy at Pole.  I brought it up early this season when we started watching the show as a group.  Might have been a mistake...  I think we've played it 10 times now...  I have single-handedly made addicts out of seven or eight people in three different collaborations.  To friends and loved ones of certain people who will remain nameless in the SPT, SPUD/Keck/SPICE, and BICEP II groups, I humbly apologize for their new addiction when they come off the ice).

The annual SPT Ladies' Night was the Friday before Christmas.  Lots of wine, cheese, and chocolates.  And slow dancing with a cosmologist!  We managed to get our work done in time to share the telescope and the science we do with the support staff at the station that make all of this stuff possible.

A beauty shot of the fully upgraded SPT.  This shot was taken from the roof of our lab at the moment of solstice.  This is the highest the Sun gets at the South Pole (23.5 degrees) - effectively our noon.  From now on it will very slowly set, and go beneath the horizon in late March until it pops up again in late September.

Cool Pictures I didn't Take of Things I've Seen

There's a lot to see on the way down to Antarctica and at the South Pole.  I took a lot of photos last year so I'm not taking as many this year.  But other folks DO take photos, and a lot of them are really good.  Amy Bender gave me permission to share some of her photos (thanks, Amy!)  They're a great collection of some of the sights we all get to see during our deployment and I'm taking this opportunity to fill in some of the cracks and gaps in the coverage of my deployment this year.  Enjoy!

Canterbury Plains, South Island, New Zealand, on the approach to Christchurch from Sydney.

Sea ice while approaching the coast of Antarctica.

McMurdo Station.  It's like a mining town.  Or parts of Grayling in the winter...

Representing Boulder, CO:  An aged Mountain Sun Brewery sticker inside the transport to the airfield.

An LC-130 waiting on the Ice Runway at McMurdo.

Mountains on the flight from McMurdo to the South Pole.

More mountains on the McM-Pole flight.

Close-up. 

Yeah, Antarctica is pretty sweet.  Too bad we don't get to see this stuff while at the Pole. 

Snow, mountains, and sky.  Wow.

SPT early in the season before the side shields were installed. It looks like either morning or evening in this photo, but that's just because it was taken through a tinted window.  It's as bright as noon out... always.

And SPTer out at the PolCal source.

Another "Now that's Antarctica" shot.

Me blackening a new baffle that went into the camera this year.

Close-up of a 150 GHz module horn array (just over 2 inches across).  You can see the corrugations inside the horns.  They're only half a millimeter thick.  That's about 1/50th of an inch.  For more prospective: the larger cylinders in the bottom of the picture are about the diameter of AAA batteries.

Me in front of a spectacular Sundog.

El Gato Negro: the Cryo Cat (the SPTpol camera cryostat).

The cable wrap inside the telescope.  The wrap includes readout wiring, thermometry, and refrigerator lines that keep the cryostat cold.  The wrap winds and unwinds as the telescope slews left-to-right (in azimuth).

The snow drift in front of the station.  It hardly ever snows here, but it does blow in from elsewhere on the continent.  Everything will get buried eventually... even the telescope and the station.  The station is propped up on those pillars, which can be jacked up.  So presumably the station can stay above the snow for quite some time.  The telescope, however, will be unusably buried within 20 years.

Mail, Side Shields, and Saunas

Sorry, folks.  A lot has been going on the past couple weeks and the internet has been really flakey so I haven't had a chance to write.  But I'm back and I'm excited to say I GOT MAIL!  Mail is great!  I promised to mention those who sent me something in a post, so here we go:

I received a Michigan themed post card from Brianna Woell.  (In case I haven't said it already I'm from Michigan and have always had a soft spot for it.  It's a great place if you've never been there!).  Brianna and I were in the University of Chicago Pep Band together.  Thanks for the post card, Brianna!  Expect one in the mail yourself!

Really Real Housewives of the UP.  Ahh, Michigan...
 

My parents also sent me a package full of goodies.  Holiday candies, an assortment of nuts (for whatever reason there aren't any nuts down here), some cookies, jerky, and chocolate magic shell (that stuff you put on ice cream that hardens after a few seconds).  I've been sharing with the SPT folk and everyone is very thankful.  Love you, Mom and Dad!

Goodies from the parents.

While we've been testing the camera on the ground, a lot of work has been going into the telescope itself.  To shield our camera from stray light bouncing off the ground, which could confuse the signals we're looking for, enormous side shields are being installed.  SPT used to have side shields, but early last season they were removed to install the guard ring around the primary mirror.  So the side shields are going back on this year.  They just happen to be bigger since they have to go around the guard ring now too.

A view of the station in the distance from the telescope.

The framework for the side shields starts going up.

Framework is complete.

Side shield panels being installed.

Finishing touches to the panels.  The white structure on the ground next to our black outhouse (called Solar 1) is a solid lead counterweight that will be installed in the next couple days to help rebalance the telescope.  Photo by Brad Benson.

Finally, about a week or so ago we did a sauna Pole run.  After taking obligatory photos of everyone with the geographic pole we decided to run a few hundred feet over to the ceremonial pole since it was such a warm day (-17 F) with almost no wind.  This was my first ceremonial pole sauna run.  The ceremonial pole is about halfway across the station from the exit we normally use to come from the sauna, so we all just jogged over to the main entrance and walked all the way through the station in our bathing suits back to the sauna.

CMB scientists at the South Pole... in bathing suits.  Photo by Liz George.

Reflections of me, Brad, and Tijmen in the ceremonial pole.   Photo by Brad Benson.

Closing Up

Last time I wrote about tearing apart the camera.  A couple days ago we finished putting it back together after making some small tweaks.  Instead of writing a bunch of text, let me just show you with pictures.  Many of these pictures were taken by Amy Bender, a post-doc on the project (and once a graduate student in Nils Halverson's group in Boulder just like me.)  Captions ending with AB denote pictures she took.  Thanks for sharing, Amy!

Liz and me inspecting the 150 GHz modules when we tore the camera apart.  (Credit: AB)

Tiny wire bonds connect the detectors on the new detector wafer to flexible readout cables.  The cables are taped down so that I can inspect all the bonds before and after wafer transfer.  (Credit: AB)

Me preparing a detector wafer sandwich for transfer onto a different horn array.  (Credit: AB)

Me assembling a 150 GHz module after installing a new detector wafer. (Credit: AB)

Successfully installed the new detector wafer.  Phew!  Now I just have to cover up those delicate wire bonds.  (Credit: AB)

A close-up shot of the feedhorns in the 150 GHz modules.  (Credit: AB)

The Receiver Team with the SPTpol camera before putting on the RF mylar and light filters.  (Credit: AB)

The 90 GHz band-defining filter covers the 90 GHz horns, leaving just the 150 GHz module horns visible.  Two more band-defining filters finish off the stack.  (Credit: AB)

Installing the aluminized mylar RF shielding.  (Credit: AB)

We moved the fourth and last filter directly installed on the camera to sit at a warmer temperature stage compared to last year.  It now covers the aluminized mylar RF shielding, which usually looks really cool.  But this looks pretty sweet, too.

I carried the camera down the stairs without dropping it!  I am relieved.  (Credit: AB)

The camera back in Black Cat ready for us to hook up thermometry, heat sinking, and internal readout cabling.  (Credit: AB)

A group photo after Black Cat was successfully mated to the secondary cryostat again.  (Credit: AB)

Opening Black Cat

Now that the PolCal team has finished measuring detector polarization angles, it’s the Receiver Team’s job to take apart the camera, fix it up a little, and re-install it.  There’s quite a bit of work involved, and the first step was taking the camera out of the telescope.  Black Cat, the name we affectionately gave the black cryostat that contains the camera, is attached to a massive “optics” cryostat that keeps the ~ 1 meter secondary mirror of the telescope at a cool 10 K.  The entire double-cryostat structure has to be lowered out of the telescope boom and back into the telescope control room so we can get to work on it.

The first thing to do is to detach all of the readout cabling that took oh-so-long to plug in and secure at the end of the last deployment season.  With the cabling out of the way we hook up some chain hoists to the giant cryostat, disconnect the helium refrigerator lines, unbolt the cryostat from the bench in which it sits in the telescope boom, and then slowly and carefully lower it down onto a rolling cart in the control room so we can move it out of the way.

Black Cat still in the telescope boom and readout electronics plugged in.  Time to disconnect all of those cables.

Ready to be dropped out of the telescope!

The cryostat is down!  JT coming down the manlift after grabbing some tools.

All of those electronics have to come down too.  The crates are really heavy so we use the manlift to help out.

Black cat on the ground and warming up.

The readout electronics set up in a rack on the ground so we can monitor the cryostat as it warms up.

The evening we dropped the cryostats into the control room we were walking back for dinner and a plane was landing, which meant we were stuck behind the crossing beacon (we have to walk across the end of the runway to get back to the station so naturally that’s dangerous when a plane is landing or taking off).  We stopped at MAPO, a laboratory where another CMB polarization telescope is operating.  During the winter a huge drift of snow lovingly called MAPO Mountain built clear up to the second floor of the building, leaving a sharp “cliff” edge facing the building.  As we waited for the plane we climbed to the top of of the cliff and slid 20 feet or so on our stomachs down to the bottom.  Lots of fun.

Another CMB scientist at the top of "MAPO Mountain."  Sliding down this winter snowdrift was a lot of fun.

Anyway, back to work!  With the cryostat on the ground we had to let it warm back up to room temperature and bring the pressure up to atmospheric (the cryostat holds a vacuum so air can’t conduct heat from the warmer portions of the cryostat to the cooler portions).  This takes about a day and a half.  By this past Friday we were ready to detach the camera cryostat from the optics cryostat.  The two are held together by some screws and a couple quarter-inch alignment pins.  It’s easiest to pull the cryostats apart when the pins are perpendicular to the ground, and this requires hoisting up the back side of the cryostat a few feet off the ground.  This thing literally ways a ton and is about the size of a VW beetle so it’s an exciting procedure.  Once everything is aligned, we literally pull the camera cryostat off and set it down on a cart of it’s own.

Now the fun really began.  We took off the various radiation shields and exposed the SPTpol camera.  This thing has been sitting at a fraction of a degree above absolute zero since mid-January and now it’s all cozy warm and open for us to look at, which is kind of fun to think about.  The back of the camera is a complicated mess of readout cabling and heat sinking to get each part of the camera successively cooler.  After an hour or so of inspection, cable and thermometry removing, and unscrewing we lifted the camera out of the cryostat and I carried it up the stairs to the clean room where we usually work on it.

A couple of days after starting to warm up, the cryostat is open and we start disconnecting all the readout cabling inside the camera.

The SPTpol camera out of the cryostat and upstairs where Liz and I dismantled it.  First we take off the spider web-like structure on the back side.

The rest of the day was spent methodically dismantling the camera to get to the detector modules at its heart, where we’ll be doing a lot of rework.  One of the 150 GHz modules was acting funny this year and we want to replace it with a spare module.  If you remember we had to install several structures to keep the back of the camera from shaking as the telescope moved and unfortunately we had to remove all of these anti-shaking structures to get to the module we wanted to replace.  Not really difficult work, but it did mean tearing the camera completely apart.  In just a few short hours the camera went from happily installed in Black Cat to being in a hundred pieces in the upstairs clean room.  It’s a little crazy to think that we have this big complicated machine and there’s no instruction manual besides our notes and pictures to refer to when pulling it apart and putting it back together.  A little scary, especially when we want to make sure it works better than last time.  But we designed it and assembled it (multiple times now) so we know exactly how it works and exactly what to do.  Just another day at the office!...

The camera flipped over to the side that accepts light.  We first have to take this filter off.

Next we remove the aluminized mylar blanket that shields the back side of the camera from nasty radio frequency interference.

  

All that's left on the front are a few more filters that define what colors of light the camera accepts.

With the filters off you can finally see the feedhorns.  The seven 150 GHz modules  are in the center.  Surrounding them are 180 individual 90 GHz feedhorns.

Flipping the camera back over we take off the "wedding cake" support structure surrounding it and can start removing the aluminum anti-shaking supports.

The focal plane almost totally dismantled.  We wanted to do work on two of the central modules, but it meant tearing out two more to get to them.