Axion helioscopes update: the status of CAST & IAXO

Almost 35 years since their suggestion as a good solution to the strong CP-problem, axions remainone of the few viable candidates for the Dark Matter, although still eluding detection. Mostof the methods for their detection are based on their coupling to photons, one of the most sensitiveones being the helioscope technique. We report on the current status of the CERN Axion SolarTelescope and the future International Axion Observatory (IAXO). Recent results from the secondpart of CAST phase II, where the magnet bores were filled with ³He gas at variable pressureachieving sensibilities on the axion mass up to 1.2 eV, are presented. Currently, CAST is expectingto improve its sensitivity to solar axions with rest mass below 0.02 eV/c² after the upgradeof the X-ray detectors and with the implementation of a second X-ray optic. At the same time,it is exploring other possibilities at the low energy physics frontier. On the other hand IAXO,the fourth generation axion helioscope, aims to improve CAST’s performance in terms of axionphotoncoupling by 1-1.5 orders of magnitude. The details of the project building a dedicatedmagnet, optics and X-ray detectors are given.