RF technology for fundamental physics

11 Aug 2025, 09:00 → 15 Aug 2025, 17:00 Europe/Berlin

Geb. 600, ChyN, 3rd Floor, Room 301/303 (DESY, Luruper Chaussee 149, 22761 Hamburg)

Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay), Marc Wenskat (UHH / DESY)

MicroWaves (MW) and Radio Frequency (RF) Technology were the breakthrough of modern particle physics in the 20th century, by realising particle accelerators for direct discovery of new physics (quarks, leptons, vector bosons and the Higgs boson) and RF spectroscopy for precision tests of Quantum ElectroDynamics (QED; Lamb shift, g-2, etc). Until very recently, the MW/RF community have been somewhat decoupled from the other domains of particle physics due to its distinct technical requirement and infrastructure to pursue MW/RF experiments. However, emergence of the research fields in physics beyond the colliders has opened new opportunities in MW/RF technology for fundamental physics, such as Cosmic Microwave Background (CMB), Gravitational Waves (GW), and in particular, dark matter axion and dark photon physics. This school aims to provide basic knowledge and skills for the students and early-career researchers to be able to follow the language spoken in this new research field based on MW/RF engineering.

The school will cover practical aspects of solving Maxwell equations beyond what students in physics department typically learn in the bachelor education, including non-plain wave solutions, resonant cavities, numerical methods, calibration methods, mean to measure electromagnetic fields, engineering devices and convention to express MW/RF as complex fields. We will particularly focus on the applications of MW/RF technology for the fundamental physics, such as axion experiments and brief introduction to particle accelerators. The student will follow lectures, theoretical exercises, hands-on experiments, and playing with commercial codes typically used in the MW/RF community.

RF_lecture_UHamburg2025_ver2.pdf

Monday 11 August

09:00 → 09:30 Introduction

• New research field in the post-LHC era: particle physics with microwaves
• How can a researcher with particle physics background learn microwaves? Physics vs Engineering
• Narrative of Akira Miyazaki from quantum electrodynamics to superconducting radiofrequency

Speaker: Dr Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay)

09:30 → 11:00 Part 1: RF in free space (lecture)

• Maxwell equations and Helmholtz equation (30mins)
  -- Plane wave solution
  -- Gaussian beam
  -- Higher-order Gaussian beam
• Gaussian beam optics (30 mins)
  -- Gaussian lens formula
  -- Lens and mirrors
• Integral form: diffraction of waves (30 mins)
  -- Airy disk diffraction
  -- Fourier transform

Speaker: Dr Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay)

11:00 → 12:00 Part 1: RF in free space (exercise)

Gaussian optics with two lenses

14:00 → 16:00 Part 2: RF in confined space (lecture)

• Material and boundary conditions (40 mins)
  -- Normal conductor
  -- Superconductor
  -- Dielectric material
• Waveguide and coaxial lines (30 mins)
  -- Rectangular and cylindrical waveguide
  -- Cut-off frequency
  -- Coaxial lines
• Resonators (50 mins)
  -- General resonator
  -- RF cavity
  -- Fabry-Pérot resonator

Speaker: Dr Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay)

16:00 → 17:00 Part 2: RF in confined space (exercise)

• Coaxial to rectangular transition

Tuesday 12 August

09:00 → 10:30 Part 3: Equivalent circuit (lecture)

• From (E, B) to (V, I) (30 mins)
  -- Physics meaning of the equivalent circuit
  -- Various impedances
• Transmission line theory (30 mins)
  -- Generalized telegraphist’s equation
  -- Mode conversion in over-sized tapered waveguides
• Circuit representation of resonators (30 mins)
  -- RLC circuit model
  -- Coupling and impedance matching

Speaker: Dr Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay)

10:30 → 11:30 Part 3: Equivalent circuit (exercise)

Over / critical / under coupling

gsl.gmk

Makefile

simrf.cc

14:00 → 15:30 Part 4: Basic of RF measurement (lecture)

• Analog and digital circuits (30 mins)
  -- Analog circuit components
  -- Analog down-conversion with superheterodyne
  -- Analog-to-digital conversion
  -- Digital down-conversion with under sampling
• Our weapons (30 mins)
  -- Vector network analyzer
  -- Fast Fourier Transform
  -- Real-time spectrum analyzer
• RF noise (30 mins)
  -- Dicke’s radiometer formula
  -- Noise power, Noise temperature and noise figure
  -- Noise equivalent power

Speaker: Dr Akira Miyazaki (CNRS/IN2P3/IJCLab Université Paris-Saclay)

15:30 → 17:00 Part 4: Basic of RF measurement (exercise)

data processing with Fast Fourier Transform

ana.C

S-parameter.s2p

Wednesday 13 August

09:00 → 12:00 Hands-on 1: Microwave simulation (group A)

• RF cavity modeling
• Electromagnetic field distributions
• RF ports and S-parameters
• Antenna modling

09:00 → 12:00 Hands-on 2: Cavity measurement with VNA (group B)

• OLST calibration of VNA
• S21 to QL
• Coupling from S11
• Q0, Qext
• Time domain analysis

14:00 → 17:00 Hands-on 1: Microwave simulation (group B)

14:00 → 17:00 Hands-on 2: Cavity measurement with VNA (group A)

Thursday 14 August

09:00 → 12:00 Hands-on 3: Cavity field measurement with beads-pulling method (group A)

• Perturbation of resonant cavity
• Interference of beads and RF response in VNA

09:00 → 12:00 Hands-on 4: Noise measurement with SA (group B)

• Power Spectral Density
• Resolution bandwidth
• Low noise amplifier
• Y-factor method to calibrate noise temperature

14:00 → 17:00 Hands-on 3: Cavity field measurement with beads-pulling method (group B)

14:00 → 17:00 Hands-on 4: Noise measurement with SA (group A)

Friday 15 August

09:00 → 12:00 Visit to facilities

• ALPSII for Fabry-Pérot resonators
• Superconducting facility for RF cavities

14:00 → 16:00 Part 5: RF applications for various physics fields

• Particle Accelerator
• Axion experiments
• Gravitational waves

Speaker: Marc Wenskat (UHH / DESY)

16:00 → 17:00 Closing session

Comments from participants