A sensitivity leap for X-band EPR using a probehead with a cryogenic preamplifier

• Published in: Journal of magnetic resonance (1997) Vol. 322; p. 106876
• Main Authors: Šimėnas, Mantas, O’Sullivan, James, Zollitsch, Christoph W., Kennedy, Oscar, Seif-Eddine, Maryam, Ritsch, Irina, Hülsmann, Miriam, Qi, Mian, Godt, Adelheid, Roessler, Maxie M., Jeschke, Gunnar, Morton, John J.L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2021
• Subjects: DEER; EPR; HYSCORE; Preamplifier; Probehead; SNR enhancement; HYSCORE; SNR enhancement; Preamplifier; DEER; EPR; Probehead
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2020.106876

[Display omitted] •We equipped an X-band EPR probehead with an ultra low-noise cryogenic microwave preamplifier.•Our setup shortens the measurement time by about 50× at low temperature.•At the expense of excitation bandwidth, above 200× reduction in the measurement time is obtained.•The probehead performance is demonstrated using hyperfine and dipolar spectroscopy experiments. Inspired by the considerable success of cryogenically cooled NMR cryoprobes, we present an upgraded X-band EPR probehead, equipped with a cryogenic low-noise preamplifier. Our setup suppresses source noise, can handle the high microwave powers typical in X-band pulsed EPR, and is compatible with the convenient resonator coupling and sample access found on commercially available spectrometers. Our approach allows standard pulsed and continuous-wave EPR experiments to be performed at X-band frequency with significantly increased sensitivity compared to the unmodified setup. The probehead demonstrates a voltage signal-to-noise ratio (SNR) enhancement by a factor close to 8× at a temperature of 6 K, and remains close to 2× at room temperature. By further suppressing room-temperature noise at the expense of reduced microwave power (and thus minimum π-pulse length), the factor of SNR improvement approaches 15 at 6 K, corresponding to an impressive 200-fold reduction in EPR measurement time. We reveal the full potential of this probehead by demonstrating such SNR improvements using a suite of typical hyperfine and dipolar spectroscopy experiments on exemplary samples.