Confirming X-ray Parametric Down Conversion by Time-Energy Correlation

TL;DR

This paper demonstrates X-ray parametric down conversion at a synchrotron source, confirming the process through time-energy correlation measurements and quantifying the conversion efficiency.

Contribution

First experimental confirmation of X-ray parametric down conversion using time-energy correlations at a synchrotron.

Findings

Observed photon pairs within 10-12 keV energy window at short time differences

Maximum pair rate of 130 per hour with a conversion efficiency of approximately 5.3 x 10^{-13}

Results consistent across different crystal alignments and detector positions

Abstract

We present measurements of X-ray Parametric Down Conversion at the Advanced Photon Source synchrotron facility. Using an incoming pump beam at 22 keV, we observe the simultaneous, elastic emission of down-converted photon pairs generated in a diamond crystal. The pairs are detected using high count rate silicon drift detectors with low noise. Production by down-conversion is confirmed by measuring time-energy correlations in the detector signal, where photon pairs within an energy window ranging from 10 to 12 keV are only observed at short time differences. By systematically varying the crystal misalignment and detector positions, we obtain results that are consistent with the constant total of the down-converted signal. Our maximum rate of observed pairs was 130 /hour, corresponding to a conversion efficiency for the down-conversion process of $5.3 \pm 0.5 \times 10^{-13}$.