A versatile and modular quasi optics-based 200 GHz dual dynamic nuclear polarization and electron paramagnetic resonance instrument

Abstract

Solid-state dynamic nuclear polarization (DNP) at higher magnetic fields (>3 T) and cryogenic temperatures (~2–90 K) has gained enormous interest and seen major technological advances as an NMR signal enhancing technique. Still, the current state of the art DNP operation is not at a state at which sample and freezing conditions can be rationally chosen and the DNP performance predicted a priori, but relies on purely empirical approaches. An important step towards rational optimization of DNP conditions is to have access to DNP instrumental capabilities to diagnose DNP performance and elucidate DNP mechanisms. The desired diagnoses include the measurement of the “DNP power curve”, i.e. the microwave (MW) power dependence of DNP enhancement, the “DNP spectrum”, i.e. the MW frequency dependence of DNP enhancement, the electron paramagnetic resonance (EPR) spectrum and the saturation and spectral diffusion properties of the EPR spectrum upon prolonged MW irradiation typical of continuous wave (CW) DNP, as well as various electron and nuclear spin relaxation parameters. Even basic measurements of these DNP parameters require versatile instrumentation at high magnetic fields not commercially available to date. In this article, we describe the detailed design of such a DNP instrument, powered by a solid-state MW source that is tunable between 193 – 201 GHz and outputs up to 140 mW of MW power. The quality and pathway of the transmitted and reflected MWs is controlled by a quasi-optics (QO) bridge and a corrugated waveguide, where the latter couples the MW from an open-space QO bridge to the sample located inside the superconducting magnet and vice versa. Crucially, the versatility of the solid-state MW source enables the automated acquisition of frequency swept DNP spectra, DNP power curves, the diagnosis of MW power and transmission, and frequency swept continuous wave (CW) and pulsed EPR experiments. The flexibility of the DNP instrument centered around the QO MW bridge will provide an efficient means to collect DNP data that is crucial for understanding the relationship between experimental and sample conditions, and the DNP performance. The modularity of this instrumental platform is suitable for future upgrades and extensions to include new experimental capabilities to meet contemporary DNP needs, including the simultaneous operation of two or more MW sources, time domain DNP, electron double resonance measurements, pulsed EPR operation, or simply the implementation of higher power MW amplifiers.

Universal Dynamics of Molecular Reorientation in Hybrid Lead Iodide Perovskites

“…85,86 The powdered sample was packed in a Kel-F (CTFE) sample cup with inner and outer diameters of 5.3 mm and 7 mm, respectively, and height of 8 mm. After packing the sample cup, the sample cup was covered using a Kel-F cap, and immediately placed into the NMR probe for cryogenic there was no amiguity in assigning the two T 1 features to the pertinent polymorphs.…”

Arbitrary waveform modulated pulse EPR at 200 GHz

“…[15] The system utilizes three digitally programmable, continuous wave (CW) ∼12GHz synthesizers to operate (i) the main microwave transmitter channel source for pulsed and CW EPR and (ii) the second transmitter channel for pump-probe Electron Double – Resonance (ELDOR) experiments, as well as (iii) to generate the LO (local oscillator) reference for the 200GHz sub-band mixer in the heterodyne receiver system. The microwave output of the main ∼12 GHz CW transmitter source (i) is sliced, and if desired mixed, with coherent AWG waveforms produced with a fast (1 GHz) DAC board for phase and amplitude modulation.…”

“…For the latter the ω 1 intensity was estimated from a nutation experiment that was published previously. [15] Notably for both BDPA and diamond samples we had to use T 2 > T m in the simulations to arrive at a good agreement with the experimental data. This is not surprising since the T m measurement provides only a lower limit for T 2 .…”

“…To this end we integrate a homebuilt AWG system with 1GHz bandwidth into a 200GHz microwave bridge with dual EPR and Dynamic Nuclear Polarization (DNP) capabilities for the purpose of confronting the pulse bandwidth limitation [15]. We implement the AWG into the 12 GHz pulse forming network of the microwave bridge.…”

Annulled van der Waals interaction and fast Rydberg quantum gates

“…In this case 2π/B determines the quantum gate operation time, and as shown below, leads to C Z gate operation times of tens of ns. Accessing this regime with high fidelity requires high-frequency microwave sources in the range 100 to 200 GHz, such as those employed in studies of electron paramagnetic resonance [26][27][28][29][30]. Stabilization of the qubit to radiative decay may be performed by mapping |1 to an electronic ground state |1 by a laser pulse.…”