2 x Heterodyne Measurement f RF 260 GHz

2 x Heterodyne Measurement f. RF ~260 GHz Down-mixing CTR-signal by f. IF ~10 GHz known reference: fref~270 GHz Mixer / f. IF = f. RF – fref Schottky • Measurement of signal diode f. IF ~ 10 -20 GHz on fast oscilloscope (20 -40 GHz bandwidth) Expected signal (f. IF=10 GHz) • Beamline at 15 m distance from oscilloscope (shielding) •

Heterodyne Measurement VDI • Reference signal by frequency-multiplied tunable local oscillater. Transmission of RF over 15 m • Only over less than one waveguide-bandwidth • Better signal efficiency VDI heterodyne receiver from EPFL ~10 -15 GHz out RF in Reference

CTR-measurement with VDI heterodyne receiver • Seems to be Clear, strong CTRsignal • Visible even when not visible on Streak camera • Consistent with modulation-events • Principle: f. IF = f. RF +/- n*f. LO 10 -12 GHz Different harmonics (n’s) possible Difficult to find correct frequency if signal is not completely steady (to be improved) • Correlate with rest of CTR and OTRmeasurements!

Additional slides

Heterodyne Measurement 2 Mixing of reference with CTR close to oscilloscope CTR-transmission line WR 90 rectangular waveguide (23 x 10 mm) with ‘tall’ TE 10 -mode: Best compromise between - Ohmic losses - Miter bend losses - Taper losses - Alignment sensitivity E-field polarization

Heterodyne Measurement 1 • Mixing of reference with CTR close to beamline • Reference signal by mixing slightly detuned lasers • Transmission of f. IF~10 -20 GHz in lowloss coaxial cables • Tunable over entire CTR frequency-range ~10 -15 GHz out Detuned Lasers, CTR-signal including fref=100300 GHz fiber 191. 0 THz (~1550 nm) tunable laser 191. 27 THz (~1550 nm) tunable laser