  A real-time Data Acquisition (DAQ) system for the CULTASK axion haloscope
experiment was constructed and tested. The CULTASK is an experiment to search
for cosmic axions using resonant cavities, to detect photons from axion
conversion through the inverse Primakoff effect in a few GHz frequency range in
a very high magnetic field and at an ultra low temperature. The constructed DAQ
system utilizes a Field Programmable Gate Array (FPGA) for data processing and
Fast Fourier Transformation. This design along with a custom Ethernet packet
designed for real-time data transfer enables 100% DAQ efficiency, which is the
key feature compared with a commercial spectrum analyzer. This DAQ system is
optimally designed for RF signal detection in the axion experiment, with 100 Hz
frequency resolution and 500 kHz analysis window. The noise level of the DAQ
system averaged over 100,000 measurements is around -111.7 dBm. From a
pseudo-data analysis, an improvement of the signal-to-noise ratio due to
repeating and averaging the measurements using this real-time DAQ system was
confirmed.
