In this work we present a search for (solar) chameleons with the CERN Axion Solar Telescope (CAST). This novel experimental technique, in the field of dark energy research, exploits both the chameleon coupling to matter ($beta_{rm m}$) and to photons
($beta_{gamma}$) via the Primakoff effect. By reducing the X-ray detection energy threshold used for axions from 1$,$keV to 400$,$eV CAST became sensitive to the converted solar chameleon spectrum which peaks around 600$,$eV. Even though we have not observed any excess above background, we can provide a 95% C.L. limit for the coupling strength of chameleons to photons of $beta_{gamma}!lesssim!10^{11}$ for $1<beta_{rm m}<10^6$.
We present the results of a novel Mossbauer experiment in a rotating system, implemented recently in Istanbul University, which yields the coefficient k=0.69+/-0.02 within the frame of the expression for the relative energy shift between emission and
absorption lines dE/E=ku2/c2. This result turned out to be in a quantitative agreement with an experiment achieved earlier on the subject matter (A.L. Kholmetskii et al. 2009 Phys. Scr. 79 065007), and once again strongly pointed to the inequality k>0.5, revealed originally in (A.L. Kholmetskii et al. 2008 Phys. Scr. 77, 035302 (2008)) via the re-analysis of Kundig experiment (W. Kundig. Phys. Rev. 129, 2371 (1963)). A possible explanation of the deviation of the coefficient k from the relativistic prediction k=0.5 is discussed.
The CERN Axion Solar Telescope (CAST) searches for $atogamma$ conversion in the 9 T magnetic field of a refurbished LHC test magnet that can be directed toward the Sun. Two parallel magnet bores can be filled with helium of adjustable pressure to mat
ch the X-ray refractive mass $m_gamma$ to the axion search mass $m_a$. After the vacuum phase (2003--2004), which is optimal for $m_alesssim0.02$ eV, we used $^4$He in 2005--2007 to cover the mass range of 0.02--0.39 eV and $^3$He in 2009--2011 to scan from 0.39--1.17 eV. After improving the detectors and shielding, we returned to $^4$He in 2012 to investigate a narrow $m_a$ range around 0.2 eV (candidate setting of our earlier search) and 0.39--0.42 eV, the upper axion mass range reachable with $^4$He, to cross the axion line for the KSVZ model. We have improved the limit on the axion-photon coupling to $g_{agamma}< 1.47times10^{-10} {rm GeV}^{-1}$ (95% C.L.), depending on the pressure settings. Since 2013, we have returned to vacuum and aim for a significant increase in sensitivity.
The CERN Axion Solar Telescope (CAST) has finished its search for solar axions with 3^He buffer gas, covering the search range 0.64 eV < m_a <1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From t
he absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g_ag < 3.3 x 10^{-10} GeV^{-1} at 95% CL, with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of g_a, for example by the currently discussed next generation helioscope IAXO.
The status of the solar axion search with the CERN Axion Solar Telescope (CAST) will be presented. Recent results obtained by the use of $^3$He as a buffer gas has allowed us to extend our sensitivity to higher axion masses than our previous measurem
ents with $^4$He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV$ le m_{a} le $ 0.64 eV. From the absence of an excess of x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g$_{agamma} le 2.3times 10^{-10}$ GeV$^{-1}$ at 95% C.L., the exact value depending on the pressure setting. CAST published results represent the best experimental limit on the photon couplings to axions and other similar exotic particles dubbed WISPs (Weakly Interacting Slim Particles) in the considered mass range and for the first time the limit enters the region favored by QCD axion models. Preliminary sensitivities for axion masses up to 1.16 eV will also be shown reaching mean upper limits on the axion-photon coupling of g$_{agamma} le 3.5times 10^{-10}$ GeV$^{-1}$ at 95% C.L. Expected sensibilities for the extension of the CAST program up to 2014 will be presented. Moreover long term options for a new helioscope experiment will be evoked.
The Turkic Accelerator Complex (TAC) project has been developed with the support of the Turkish State Planning Organization by the collaboration of 10 Turkish universities. The complex is planned to have four main facilities, namely: SASE FEL Facilit
y Based on 1 GeV Electron Linac, Third Generation Synchrotron Radiation Facility (SR) Based on 3.56 GeV Positron Synchrotron, Super-Charm Factory ($sqrt{s} = 3.77$ GeV) by colliding the electron beam coming from the linac with an energy of 1 GeV and positron beam coming through the positron ring with an energy of 3.56 GeV, GeV scale proton accelerator. Later has two-fold goal: Neutron Spallation Source (NSS) and ADS. The proton accelerator construction will have 3 MeV, 100 MeV, and 1 GeV phases. The technical design report is planned to be finished in 2013. Since Turkey has essential Thorium reserves the ADS becomes very attractive for our country as emerging energy technology.
The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using 3He as a buffer gas. At T=1.8 K this allows for larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with 4He. Wit
h about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV < m_a < 0.64 eV. From the absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g_ag < 2.3 x 10^{-10} GeV^{-1} at 95% CL, the exact value depending on the pressure setting. KSVZ axions are excluded at the upper end of our mass range, the first time ever for any solar axion search. In future we will extend our search to m_a < 1.15 eV, comfortably overlapping with cosmological hot dark matter bounds.
