Search for Two-Photon Interaction with Axionlike Particles Using High-Repetition Pulsed Magnets and Synchrotron X Rays

We report on new results of a search for a two-photon interaction with axionlike particles (ALPs). The experiment is carried out at a synchrotron radiation facility using a “light shining through a wall (LSW)” technique. For this purpose, we develop a novel pulsed-magnet system, composed of multiple racetrack magnets and a transportable power supply. It produces fields of about 10 T over 0.8 m with a high repetition rate of 0.2 Hz and yields a new method of probing a vacuum with high intensity fields. The data obtained with a total of 27 676 pulses provide a limit on the ALP-two-photon coupling constant that is more stringent by a factor of 5.2 compared to a previous x-ray LSW limit for the ALP mass $\lesssim 0.1\mathrm{eV}$.

Figure 1

Schematic of the experimental setup. (a) A layout of components in the optics hutch and in the two experimental hutches. Retractable components are shown with a vertical arrow. (b) A side view of the magnet system. The magnets are placed so as to produce parallel fields with respect to the horizontal polarization of the x-ray beam. Two identical discharge sections (DS1 and DS2) that are contained in the same hutch supply pulsed currents to the magnets by $LC$-discharge circuits.

Figure 2

(a) Field shape of a shot with a charged voltage of 4.0 kV at the magnet center ($B_0$). The first pulse has a peak field of 9.5 T, while the second one reduces to 7.0 T due to the heat loss of coil resistance. (b) Peak-field distribution of all 27 676 pulses during the run.

Figure 3

(Top panel) Time-energy distribution of x rays measured with the germanium detector. Each circle represents an event. The horizontal axis is the time from the beginning of the first pulse. The energy threshold was set at around 3 keV. (Bottom panel) Events around the field duration of 2.1 ms. The signal region is shown around the beam energy $\pm 2\sigma$ within the time window.

Figure 4

Upper limit on the ALP-two-photon coupling constant $g_{a\gamma \gamma }$ at 95% C.L. as a function of the ALP mass. The previous x-ray LSW limit obtained at the ESRF [46] is shown for comparison. (Inset) A large-scale view. Previous laser LSW searches [37, 38] and solar axion searches (CAST [47, 48, 49, 50]) are shown along with the band of invisible axion models [39, 40, 41, 42].