SEM SIC SEM SIC 2 SEMs & 2 SICs closed to the Dumps 1 SIC, 1 Faraday cup & 1 SEM SEM SIC F. cup 4 similar set-ups : Girder 6,7,11 and 13 4 th – 8 th October 2004 tests

RAW signal (no amplifier or electronics – just cable to digitizer) SIC Voltage Dependence on SIC visible: Signal on the decay side for the SIC at different voltages, give correct sign dependence. Keeping the beam loss constant, the signal increases with applied voltage average of 5 measurements at each voltage We can see the rise time (~30ns) and the decay time (~120ns) (to be checked with a fit)

Voltage Scan of Chambers at Girder 7 with the electronics (50ohm resistor to an amplifier) 1. SIC voltage scan Dominated by a signal that is not ionization, since when changing the voltage, the signal does not move in the correct direction. Estimate 1 mA/cm 2 of current from the beam going through the chambers. This is a high beam loss region.

2. SEM voltage scan The SEM gives the same result as the SIC Data taken at the same time, same beam conditions. Same z position. Just the mounting position in x different Thibaut please check – is this in x? Hence the SEM seems to be collecting noise, by a mechanism similar to the SIC

Intensity Scan for Faraday cup, SIC and SEM: The signal of the faraday cup and the chambers are correlated The faraday cup seems to give a signal more than the SIC and the SEM, and proportional to the difference between the area of the signal collectors: Area of collectors: SIC 2cm 2 and the Faraday cup 16 cm 2

Conclusions: SIC is functioning as an ion ionization chamber – since we see the voltage dependence SIC and SEM are dominated by noise There is noise both when the Chambers are connected to the resistor and Amplifier, and when they are connected directly to the digitizer Intensity scan – the chambers increase in signal, proportional to the faraday cup, but full intensity scan must still be completed. TO DO –Find the source of the noise (cable pick-up to the amplifier, or to the digitizer) –Only then we can study the timing response, to see if it is suitable for a few nanosecond real time response