RF Pick-Up Measurements in the 2004 SPS Testbeam Before installation of silicon detector assemblies in the Roman Pot: Antenna insertions for measurement of RF background 1 wire loop in the pot (  B-field) 1 pin in the pot (  E-field) For comparison: 1 open coax cable outside near the beam pipe 1 terminated coax cable outside near the beam pipe Read-out with spectrum analyser sometimes replaced by a 2 nd antenna insertion lying on the ground

Antenna Measurements: Examples CNGS (Gran Sasso) beam: 200 MHz bunch frequency during spill Higher harmonics visible: 400, 600, 800 MHz 80, 120, 160, 200, 240, 280, 320, 520, 680 MHz Spectra measured from 0 to 3 GHz. 25 ns beam: 40 MHz bunch frequency during spill

Spectrum Evolution during an SPS Cycle 1 st half ring filling 2 nd half ring filling, after acceleration after extraction time 200 MHz

Analysis Status Spectra give us pick-up in mW at the end of the coax cable (surface building). Problem: Where was the signal picked up? Solution: Compare with the signal induced in the cables ending blind outside the beam pipe. Different cable lengths and types  correct each spectrum for cable attenuation (data from pool catalogue).

25ns Beam: Comparison inside/outside Pot Natel = 956 MHz Typical error bar: ~ 2 dB

Loops Pins inside outside inside outside 25ns Beam: Comparison inside/outside Pot (low frequencies) No clear quantitative conclusion about inside/outside comparison. Similar situations for Gran Sasso beam and for 400 GeV beam.

A Hint at Pick-Up by VFAT ? 25ns Beam: big fraction of VFAT signals 1.6  s too late TOTEM Beam: ~ ~ ~ 0.8  s ~ ~ Cannot be: Cable length difference (Would need 400 m! In-time signals also exist.) Delay in chip or motherboard (  Walter) What is it ???

Future RF Tests in the Lab Suggestions from F. Caspers: Remount the antenna pieces on the Roman Pot, add pieces of beam pipe on both arms (planned for end of this week) Inject pulse with network analyser Generate spark with a spark pistol (or even just a bricolage solution)