This year has been an important one for our group. The new long-awaited “IAXO pathfinder” system has been finally (and successfully) installed in CAST. It consist of a newly built x-ray optics coupled to a low-background Micromegas detectors. The optics (telescope), built by our colleagues of LLNL, DTU and UC, is the first optics ever designed and built especifically for axion physics (i.e. optimized to focus photons with the solar axion spectral distribution), and it uses the same technique (slumped glass substrates) as proposed for IAXO. The optics arrived to CAST in August 2014 for installation in one of the sunrise ports of CAST.
This is a picture of the optics in place in CAST:
This system is also the first time an x-ray optics is coupled to a low background detector, joining in one system two of the strategies that CAST has used in the past (in different lines), so that this system has become the one with the best signal-to-noise so far. The following is a picture of the full line (previous to the installation of the shielding around the Micromegas) where the Micromegas detector at the focal point fo the optics is visible at the bottom of the picture: 
The installation in CAST was carried during september 2014. The telescope was aligned and the detector was calibrated both with a near source and a far (14 m away) source to test both the focalization and the detector. The pictures below are real Micromegas data from the near source (left), and the far source (right). The hitmap of the left shows the shape of the strongback of the entrance window of the detector, and the one of the right shows the 5 mm focal spot. To give an idea of the dimensions the drawn circle has 8.5 mm diameter and corresponds to the inner circular portion of the entrance window:
These exciting results are the summit of a long and large effort carried out by many people. This system will provide joint operational experience with two of the technologies proposed for IAXO, so it is a very important milestone for the project. It is now taking physics data in CAST (and will continue all of 2015), with an outstaningly low level of backgrtound (about 1 count is expected in 100 CAST trackings (!) in the Micromegas focal spot). Let’s see what the data will show: we may still see an axion there!
You can find more technical information on the installation of the IAXO Pathfinder system in the report of the CAST collaboration to the SPS committee of CERN here.
Here two members of the team (Juanan and Javier) working hard in the CAST area…
