Transcript Test_results_2_8oct

2 SEMs & 2 SICs closed to the Dumps
4th – 8th October 2004 tests
1 SIC, 1 Faraday cup & 1 SEM
SEM
SIC
F. cup
SEM
SIC
SIC
SEM
4 similar set-ups : Girder 6,7,11 and 13
RAW signal
53
52
(no amplifier or electronics
– just cable to digitizer)
51
49
Voltage Dependence on SIC
visible:
48
47
46
Signal on the decay side for the SIC
at different voltages, give correct
sign dependence.
No polarization
+ 180 volts
- 180 volts
45
44
43
42
2200
2400
2600
2800
3000
3200
-4
time (ns)
-3
•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)
SIC signal isolated (mV)
SIC amplitude (mV)
50
+180 volts
+140 volts
+100 volts
+40 volts
+20 volts
-20 volts
-40 volts
-100 volts
-140 volts
-180 volts
-2
-1
0
1
2
3
4
2200
2400
2600
2800
Time (ns)
3000
3200
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.
200
Signal (mV)
0
-200
-400
SIC : Girder 7
0 Volt
+150 Volts
-150 Volts
-600
-800
2600
2800
3000
Time (ns)
3200
3400
The SEM gives the same result as the SIC
2. SEM voltage scan
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
200
Signal (mV)
0
-200
-400
SEM
0 Volt
+150 Volts
-150 Volts
-600
-800
2600
2800
3000
Time (ns)
3200
3400
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
70
60
50
40
Signal (mV)
30
Case 1
Fcup
SIC
SEM
Case 2
Fcup
SIC
SEM
20
10
0
-10
-20
-30
-40
2200
2400
2600
2800
Time (ns)
3000
3200
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