Physics Lab Equipment

LEAI-15 Microwave Electron Spin Resonance Apparatus

LEAI-15 Microwave Electron Spin Resonance Apparatus

Note: oscilloscope not included


  • Simple structure

  • Ample experimental examples

  • Stable performance


Electron spin resonance, also known as electron paramagnetic resonance (EPR), refers to the phenomenon that a resonance transition between magnetic energy levels occurs when the electron spin magnetic moment is impacted by an electromagnetic wave of specified frequency in a magnetic field. This phenomenon can be observed in paramagnetic substances with unpaired spin magnetic moment (i.e. compounds containing unpaired electrons). Thus, electron spin resonance is an important method to reveal the microstructure of a substance by probing the unpaired electrons in the material and analyzing how they interact with surrounding atoms. This method has high sensitivity and resolution, and it is a nondestructive detection technique for analyzing the internal structure of materials. This technique has been widely used in physics, chemistry, biology and medicine, and other fields of study.


This apparatus of electron spin resonance in microwave band is specially designed for teaching advanced physics at universities and colleges. The instruction manual contains comprehensive materials including experimental configurations, principles and step-by-step instructions. Please click Experiment Theory and Contents to find more information about this apparatus.Using this apparatus, the following experiments can be conducted:


1. Study and acknowledge electron spin resonance phenomenon.

2. Measure Lande's g-factor of DPPH specimen.

3. Learn how to use microwave devices in EPR system.

4. Understand standing wave by changing resonant cavity length and determine waveguide wavelength.

5. Measure standing wave field distribution in resonant cavity and determine waveguide wavelength.


Microwave System
Short-circuit pistonadjustment range: 30 mm
SpecimenDPPH powder in tube (dimensions: Φ2×6 mm)
Microwave frequency metermeasurement range: 8.6 GHz ~ 9.6 GHz
Waveguide dimensionsinner: 22.86 mm × 10.16 mm (EIA: WR90 or IEC: R100)
Input voltage and accuracyMax: ≥ 20 V, 1% ± 1 digit
Input current range and accuracy0 ~ 2.5 A, 1% ± 1 digit
Stability≤ 1x10-3+5 mA
Strength of magnetic field0 ~ 450 mT
Sweep Field
Output voltage ≥ 6 V
Output current range0.2 ~ 0.7 A
Phase adjustment range≥ 180°
Scan output
BNC connector, saw-tooth wave output 1~10 V
Solid State Microwave Signal Source
8.6 ~ 9.6 GHz
Frequency drift
≤ ± 5×10-4/15 min
Working voltage
~ 12 VDC
Output power
> 20 mW under equal amplitude mode

Operation mode & parameters

Equal amplitude

Internal square-wave modulation

Repetition frequency: 1000 Hz

Accuracy:   ± 15%

Skewness: < ± 20%

Voltage standing wave ratio
< 1.2
Waveguide dimensions
inner: 22.86 mm × 10.16 mm (EIA: WR90 or IEC: R100)

Parts List

Main Controller1
Support Base3
Microwave System1 set (including various microwave components, source, detector, etc)
DPPH Sample1
Instructional Manual1

      Apparatus of Microwave Electron Spin Resonance.png

Diagram of apparatus

(Click figure to enlarge)

         LEAI-15 Microwave Electron Spin Resonance Apparatus.png

  LEAI-15 Microwave Electron Spin Resonance.jpg


Waveform of EPR signal

(Click photo to enlarge)

     LEAI-15 Microwave Electron Spin Resonance Apparatus.png

Standing wave distribution in cavity

(Click figure to enlarge)

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