Preparations for RHIC Run 25 are in full swing. In the past week(s), the superconducting magnets are all lowered to the temperatures where we can start to use liquid helium for the last step to 4K. In the status plot, below, you can see how each of the sectors sequentially sees its temperatures lowered to about 70-80K. Liquid helium will do the rest, and by March 23 we expect to see the full RHIC ring at 4K operating conditions.


Meanwhile, we are preparing the detectors of the STAR experiment. For starters, we make sure that we can ramp up the solenoidal magnet (the S in STAR) and flow the flammable gas in our tracker (the T in STAR), called the TPC. Without actual beam collisions we are able to set up our detectors to trigger for cosmic rays, i.e. the muons that are the decay products of energetic protons hitting the earth's atmosphere, leading to large particle showers that include many pions (the lightest mesons). These pions subsequently decay into muons (and neutrinos, which the STAR detector does not see). Even muons don't have eternal life, but thanks to special relativity (and their high velocity) we can still see them as they zap through our detector before turning into electrons. The video below shows our detector registring single muons. If you look carefully then you can see some of the tracks have some curvature. That's the magnetic field acting upon the charged particles! You also see that some tracks appear broken up in pieces. Well, that's why we start this testing well ahead of our operations using beam collisions: we are using these tracks to check each and every piece of our detectors!

Click on the picture below to see a ~45second GIF of incoming cosmic rays.