Into the cave

Well I finally got to do something that I've wanted to do for some time: I went down into the ALICE cavern and saw the detector itself. For those who don't remember previous posts, ALICE is about 60 meters underground and is accessible for people via a small elevator that is on the other side of an iris scan.

I had to get a dosimeter to make sure I don't absorb too much radiation (I absorbed none, everything is off) and permission from the safety officer for ALICE who coordinates who goes down and when, but overall it was much easier than I expected. Ostensibly the reason I was going down was to help Bjorn with some measurements. In reality this merely made things easier for him, and the real reason I went down is because it's really really neat. I got pictures! Enjoy!

This is the main hall of ALICE, above ground. On either side of this picture you can see the massive concrete blocks that were covering the top of the pit to make sure no stray radiation got out during the last run. There are a lot of them and they have to be removed one by one.

Here is a picture strait down into the pit. I posted a similar picture earlier when it was covered where the rim is about halfway down the shaft. This is where new equipment that is too big to go in the elevator is lowered by an absolutely massive crane.

This is how everything that isn't a large detector part gets down to see ALICE. All I had to do was scan my dosimeter, go into the yellow doors and scan my eye on the blue box you can see inside. It then let me into the room behind it (there are two sets of doors though that's hard to see from the picture. When things are running and they have to access the cavern (the "pit" seems to refer to the shaft, the cavern is the area underneath. Or they're not consistent in their naming) it requires calling the GLIMOS (group leader in matters of safety) who will release a key into the slots between the yellow doors and the blue where the intercom is, you then take the key and show it to the camera (behind me when I was taking the picture), then you put it in, scan your dosimeter, turn it, put it in your pocket, then do the eye scan. Rather involved and takes way more training than I have.

While down in the cavern there is a danger of things being dropped by people working and residual radiation since the whole area is a hazard area during running. So we wear a hard hat! In the picture is also my dosimeter.

We also wear steel toed shoes that, as I mentioned in the last post, are hideously uncomfortable. I decided that this little setup was adorable so I took a picture.

Here is Bjorn! We are past the access point and about to go into the cavern via the elevator.

We went down a series of stairs until we were roughly level with the ALICE detector itself. The large red thing is the magnet that, during operation, carries 30,000 amps of current to keep the enclosed area at half a Tesla (which is a rather large magnetic field). By comparison, house current in the US is around 15-20 amps.

Here is the thing that we were taking measurements of. It is a new part of the electromagnetic calorimeter, the detector that Creighton helps manage. We had to measure each of the panels sticking up so that we know where they are in relation to each-other.

This massive door is the end cap of ALICE. It is part of the magnet casing and part of the overall shielding for the experiment, though it does less than the 40 meters of concrete and earth above the detector. It is closed when we aren't inserting new components. The yellow rack there is installing another part of the EMCal.

This is the far side of the ALICE experiment. The big panels are for muon detection.

Here is a better view of the interior of the detector. Everything is crammed in there and I haven't the faintest clue exactly which bundle of wires is what detector... Oh well, you can probably find it online if you really want to know. Everything there is mounted to the entrance rather than attached to anything inside. This is because the magnet gets quite hot when it is on for months at a time and it could damage the detectors. There are reflective panels between the central area and the magnet that help protect the detectors as well.

This is a rack of a bunch of electronics that has to do with the inner tracking system (I believe). people can walk there, but as with any work in here you have to be careful since there is delicate equipment everywhere.

Here are the main power supplies for the EMCal! They have their own water cooling system, a miniature of the monster that runs through the entire experiment.

Here is below where the last few pictures were taken. This is the main coolant plant for the detector. Water is pumped from here to all the places it is needed to help keep things from burning up with all the power being drawn.

This is a little hole in the magnet door. About three feet across (if that) it is the only way to access anything once the doors are shut. People must go through here if they have to come in during a run.

A vertical view of the magnet door. This place is very large. Also the lights made for some cool effects.

And now for similar scale, this is the whole detector as seen from the floor of the cave.

Bjorn decided to show me the inside of the detector as well (or as much of it as a person can reach, which reminded me of pictures of the space shuttle for how much room one has to breathe). This is the underside of the detector. As you can see everything is mounted on central beams with vents for wires and, in this case, air for cooling (and breathing). Air has to be pumped down from above so we can breathe.

These last pictures are inside the detector itself. The clear wires are water coolant for the detector, and everything else... I'm not sure what it does. The massive silver cone in this picture is what can be seen of the muon absorber which, ironically, absorbs everything except muons so that the big panels I showed you earlier contend with only one kind of particle.

What you see is all the space that there is with lots of coolant tubes and wiring. It's cramped and hard to get to: we went up a couple of ladders and along passageways where we had to bend almost double to get through. It was a seriously cool experience and I don't know if I'll be able to repeat it since the EMCal group is almost done with their work and I need a reason to go down. If I come back during a long shutdown they give tours of the LHC, so maybe I can do that.

One more thing before I sign off: My friend Polly has commissioned me to write a poem that ALICE matters (the internal newsletter for those who don't remember) will do a podcast of me reciting it. That's right, someone actually ASKED me to write a poem! Here it is below!

The Cavern
By James Falconer Ross

Through metal doors and iris scans lies high technology
Under the ground behold the sound sets quarks and gluons free
Though for today the giant ring lies dormant in its dreams
Before too long we'll hear its song upon electric streams
Alloys gleam and scintillate in shadows cast through steel
As silence flares and blinded glares crash screaming 'round the wheel
At energies that ne'er before has man attained in flight
It's in this place the silence breaks and blindness turns to sight

Though powerful this monster is that gnaws at quarks with teeth
We're here to mend as we descend into the earth beneath
Yes powerful though fragile too: the year can take its toll
There's work to do and it's our crew that's ticking off the roll
Once in this place all that you see was filled with earth and stone
'Twas hand of man that moved the land, worked fingers to the bone
And now beneath the rolling hills a techno-forest creeps
Trees of metal without a petal stand vigil in the deeps

They start like vines winding down the walls twisting as they fall
Then to ALICE they blow a kiss and power through the hall
And branching off they wend their way into the myriad plans
For waiting there, no room to spare, they find their woven stands
The EMCal, the TPC, but species in a zoo
Their banishment, their nourishment is this symphonic stew
A symphony of blinking lights and gently roaring fans
The clustered cells like iron wells laid gently by our hands

We hurry now, there's much to do before we call it quits
We navigate the complex state and keep about our wits
Replace that card! Connect that wire! Our time is running short
But careful too 'lest through and through you overload the port!
Now input here! Now output there! Now tie these off with strings!
Our grove we tend and signals send to test a thousand things
We have a week or maybe two to ready for the run
In all that time we're quite sublime, we do this for the fun

Now all is patched and we're released, last cables have been laid
We never rested, ALICE is tested, the lights begin to fade
Once we are gone and dark returns the monster slowly wakes
Forest stirring and cavern purring all the time it takes.
Slowly stretching and reaching forth it tentatively grasps
The power threads that make its beds until its final gasps
When beam returns its senses seethe, straining like a beast
When ions fly then gleams its eye and gluts itself in feast

Hope all is well with everyone!
Ciao!