Electron Paramagnetic Resonance (EPR) Facility

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  • A commercial continuous wave (CW) X-band (9 - 10 GHz) EPR spectrometer ESP-300 E from Bruker.
     
  • A homebuilt S/C band (2 - 8 GHz) pulsed EPR spectrometer that features two independent mw channels, each including a mw switch, 0/90/180/270-degree phase modulator, attenuator and phase shifter. The channels can be configured to have the same mw source (in usual ESEEM experiments) or separate mw sources (for pulsed ELDOR experiments). The power amplifier is a 1 kW TWTA from Applied Systems Engineering, Inc..
     
  • A homebuilt X/Ku band (8 - 18 GHz) pulsed EPR spectrometer that features two independent mw channels, each including a mw switch, 0/180-degree phase modulator, attenuator and phase shifter. The channels can be configured to have the same mw source (in usual ESEEM experiments) or separate mw sources (for pulsed ELDOR experiments). The power amplifier is a 1 kW TWTA from Applied Systems Engineering, Inc..
     
  • A homebuilt Ka band (26 - 40 GHz) pulsed EPR spectrometer that effectively features two independent mw channels, each including a mw switch, attenuator and phase shifter. A 0/180-degree phase modulator is common for both channels. The channels can be configured to have the same mw source (in usual ESEEM experiments) or separate mw sources (for pulsed ELDOR experiments). This spectrometer actually takes the mw pulses formed by the S/C- or X/Ku-band spectrometer, and runs them through the frequency quadrupler. The same is done for the reference frequency. The phase of the mw pulses is modulated already in Ka band by a 0/180-degree phase modulator. Signal detection is also performed in Ka band. The power amplifier is a TWTA from Applied Systems Engineering, Inc. that gives out about 100 W at 26 and 40 GHz and reaches up to about 260 W in the middle of the range.

 

Our ENDOR equipment includes two RF synthesizers (PTS-310 and HP8657A) and a power amplifier AR 250L from Amplifier Research. The pulsed ENDOR experiments are currently possible in X/Ku- and Ka bands, which is determined by the fact that only for these bands the ENDOR resonators are currently available in this Facility. Currently we are not equipped for CW ENDOR experiments.

Resonators:

Our CW EPR resonators are those from Bruker, and they are not equipped for ENDOR. The pulsed EPR resonators are all homemade, and those for the frequencies higher than 8 GHz have an RF coil for ENDOR. The low-frequency (2 - 8 GHz) resonators are loop-gaps, and they are not equipped for ENDOR.

Timing:

Timing for pulsed EPR spectrometers is provided by AWG1000-DOUT board from Chase Scientific. This board has 12 digital (TTL) outputs with 1 ns time resolution, and it directly controls most of switchable devices (mw switches, phase modulators) in the pulsed spectrometers.

Temperature control equipment:

The temperature control equipment includes two cryostats, ESR-900 and CF-935 from Oxford Instruments, coolant (liquid helium or nitrogen) transfer tube, temperature controllers and pumps. With this equipment we can perform CW EPR experiments at temperatures from ~ 4 K to ~ 600 K, and pulsed EPR experiments at temperatures from ~ 3.7 K to ~ 300 K.

 

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