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As usual, members of the CMBeam team participated in the European Science Night. Here in Iceland this is called Vísindavaka. As before, our booth was equipped with our 2.4-m gravity simulator which is always a big hit. We find that the most effective demonstration by far involves splitting the kids into two groups and then asking the groups to toss marbles into opposite directions. We subsequently get a lot of collisions and marbles falling into the center of the gravity well. The marbles that survive are typically all rotating in the same direction, just like the planets in our solar system :)

It has been 2 months since we started working on assembly and leak checking of the cryostat vacuum vessel at Héðinn. During this time, we discovered some issues with welds that needed to be fixed. As you would expect, we also discovered some aspects of the design that would be done differently if we were to repeat this exercise.

We were really lucky to have excellent support from Héðinn during this time. They kindly agreed to house and feed us while we went through the process and give us access to their excellent infrastructure. This led to a really fast repair and testing turnaround. In the end, we pumped down the vacuum vessel 10 times and spent a minimum of 12 work days during this period. The last of these visits happened on May 22 when we could not reliably detect any leaks in the vacuum vessel. The cryostat was shipped to the University of Iceland on May 26 :)

P.S: One of the most surprising discoveries from this effort was how reliably we could localize leaks in welds through the use of butyl rubber. We simply pressed the rubber firmly against the suspect area and found that pressure and/or leak rate would drop significantly.

These last few days, our group has been busily assembling the vacuum vessel for our new cryostat that Héðinn manufactured. All the parts fit together nicely, but of course we had to tackle a few challenges. This included making minor modifications to the hermetic plate so that it would mate with the cryostat and cutting out small sections of the welds so that some bolts could be tightented properly. The cryostat was pumped down for the first time on the 13th of March. As expected we found some leaks in the aluminum welds. The photos below document some of the work that took place in the period from March 11 to March 16.

PhD students Ashesh Khatua and Rustam Balafendiev are visiting Kavli IPMU in Japan as part of the CMB Inflate program. During the visit, they get an opportunity to work with some of the excellent researchers working on CMB research in Tokyo metropolitan area.

We had the privilege of welcoming Professor Jeffrey Mcmahon to our lab last week. Jeff is a pioneer in microwave optics who has made major contributions to some of the most advanced telescopes on the planet. During his visit, Jeff gave a talk for the public with the title: From Curiosity to the Cosmos: A Tale of Humanity’s Progress. Just before the talk was about to start, strong northern lights turned on above Reykjavik.

Members of the CMBeam team went on a site visit to Hedinn hf to track progress on the construction of our new cryostat. This cylindrical structure, approximately 1.5 m in diameter and 1.0 m in length, consists of three thermal stages: a 300-K vacuum vessel, a 40-K radiation shield, and a 4-K cold stage. The two cryogenic stages are cooled by a Bluefors PT420 pulse-tube cryocooler and are mechanically supported by six thermally isolating G10 flexures positioned near the mid-plane of the system. The cryostat provides sufficient volume to perform holographic measurements of the full three-lens refractor optical systems designed for the Taurus experiment as well as other refracting telescopes and optical tubes for the cosmic microwave background. This system represents the first cryostat ever built in Iceland.