Our skillful technical team has developed a variety of electronic modules, systems and probes for NMR and ESR. We are open to disseminate these projects and share our designs either in a collaborative or a service mode of action. Major recent instrumentation projects include:
- 6-18 GHz pulsed ESR microwave bridge:This bridge is constructed from a variety of home-made and commercially available coaxial modules. Bridge specifications:
- Freq. Range: 6-18 GHz
- Output Power: ~5 W
- Output type: CW (supports cavity tune mode) and pulse (2 ns min pulse width).
- IF Bandwidth: 200 MHz
- Output phases: 5 bit phase resolution
- 33-36 GHz pulsed ESR microwave bridge: This bridge is constructed from a variety of home-made and commercially available WR-28 modules. It operates with the 6-18 GHz. Bridge specifications:
- Freq. Range:33-36 GHz
- Output Power: ~6 W
- Output type:CW (supports cavity tune mode) and pulse (2 ns min pulse width).
- IF Bandwidth:200 MHz
- Output phases: 5 bit phase resolution
- 6-18GHz CW ESR microwave bridge:This bridge is constructed from a variety of home-made and commercially available coaxial modules. Bridge specifications:
- Freq. Range: 6-18 GHz
- Output Power: ~0.2 W
- Output type: CW Bridge includes AFC module and reference arm.
- Pulsed gradient drivers for ESR and NMR:A variety of pulsed gradient drivers for ESR and NMR imaging were developed in our lab. These drivers provide a half-sin current drive.Typical current drive system specifications are:
- Max current: 100 A
- Pulse width: 150-2000 ns (up to 100 ms for NMR)
- Voltage of operation: -500V, +600V
- Repetition rate: 20-40 kHz (~1 kHz for long gradient pulses in NMR)
- Retrofitted Lakeshore Magnetic Field controller: The field of instrumental ESR suffers from the lack of good magnet field controller. The Lakeshore 475 seems to be a good affordable solution to this problem, however it suffers from poor 16-bit resolution. For example for fields above 3.5 kG one must use the 35 kG range, where display resolution is 0.1 G and control resolution is ~1 G . These specifications are not good enough for most ESR applications. To solve these problem we implemented a retrofit for the Lakeshore 475 which provides both display and control resolution of 10 mG at high fields above 3.5 kG. Better resolution can be obtained, but at such levels the Hall probe noise becomes dominant.
- Retrofitted Walker electro-magnet power supply: Walker high power supplies for electromagnets have relatively good long term stability (that can be improved by closed loop magnetic field controller) but poor short term stability (that can not be compensated by the field controller). We have measured short term variations at frequencies of 10-1000 Hz that can reach 10-100 ppm and are very problematic when measuring radicals with long relaxation times. To correct for these problems we have developed a retrofit kit for the walker power supply that provides short term stability that is an order of magnitude better than the factory supplied systems.
Other instrumentation projects include the development of miniature ESR imaging probes, NMR self contained probes, complete pulsed and CW ESR spectrometers and low frequency (2-12 MHz) NMR imaging spectrometer.