An Experiment and Detection Scheme for Cavity-Based Light Cold Dark Matter Particle Searches

Figure 7

(a) Raw voltages as a function of time measured with the setup corresponding to resonance from a 2.4 GHz signal injected (weakly coupled) into the cavity, as detected by the TD and HEMT detector-amplifier at 300 K and measured and displayed by our test Digital Storage Oscilloscope (DSO). The signal has roughly 8.5 mV magnitude as expected and is a raw signal without any kind of signal conditioning (except the amplification and filtering in the on-board postamplifier). One can observe a measured SNR of approximately 4.5 from this plot, which is encouraging at room temperature operation. (b) The measured voltages as obtained with the help of a data acquisition system (DAQ) scheme for identical experiments and an identical 2.45 GHz source signal as shown in Figure 7(a). A 12 mV signal was measured by the DAQ scheme corresponding to resonance. Although the signal amplitude is quite higher, a slightly lower SNR (around 3) is obtained with the DAQ scheme as compared to the DSOX (greater than 4), which is a result of the production of noise from the signal conditioning stages in the DAQ.

(a)

(b)