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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.
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SEM
SIC
SEM
SIC
2 SEMs & 2 SICs closed to the Dumps
1 SIC, 1 Faraday cup & 1 SEM
SEM
SICF. cup
4 similar set-ups : Girder 6,7,11 and 13
4th – 8th October 2004 tests
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No polarization + 180 volts - 180 volts
S
IC a
mpl
itude
(mV
)
time (ns)
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3
2
1
0
-1
-2
-3
-4
+180 volts +140 volts +100 volts +40 volts +20 volts -20 volts -40 volts -100 volts -140 volts -180 voltsS
IC s
igna
l iso
late
d (m
V)
Time (ns)
RAW signal
(no amplifier or electronics – just cable to digitizer)
Voltage Dependence on SICSIC 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)
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-800
-600
-400
-200
0
200
SIC : Girder 7 0 Volt +150 Volts -150 Volts
Sig
nal (
mV
)
Time (ns)
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/cm2 of current from the beam going through the chambers. This is a high beam loss region.
2600 2800 3000 3200 3400
-800
-600
-400
-200
0
200
SEM 0 Volt +150 Volts -150 Volts
Sig
nal (
mV
)
Time (ns)
2. SEM voltage scanThe 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
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-40
-30
-20
-10
0
10
20
30
40
50
60
70
Case 1 Fcup SIC SEM
Case 2 Fcup SIC SEM
Sig
nal (
mV
)
Time (ns)
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 2cm2 and the Faraday cup 16 cm2
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
