Post on 05-Jan-2016
description
1
Production #291HV
HV
12
3 7 12
Before After
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Production # 503HV
HV
Before After
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Diode scan (no HV) from damaged tube fromCERN HPD #291
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Setup and readout
HV =10 kV
Ortec Preamp
A~0.5 mv/pe
Keithly 80 V BIAS and ampmeter
80.00 V 05.956 nA
B
LED pulser
5
Noise seen with ortec QI amplifier in Pixel10
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
-1.00E-03 -8.00E-04 -6.00E-04 -4.00E-04 -2.00E-04 0.00E+00
(s)
(V)
We see the same noise at CERN in B-field (Ortec amplifier is a QI, fast rise time and slow decay)
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HPD 291 no Angle
0
10
20
30
40
50
60
70
80
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
B (T)
Bia
s cu
rren
t (n
A)
Bias Curr
Big Pulses
We can see the small pulses with keithly bias supplyWithout amplifier we see also large pulses in bursts
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HPD 503 at 0.7 Tesla
05
101520253035404550
0 20 40 60 80 100 120 140
Angle (deg)
Bia
s C
urr
ent
(nA
)
bias curr
Big Pulses
When getting on an angle small pulses increase but large ones disappear
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Tube 291
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
-4.E-06 1.E-06 6.E-06
(s)
(V)
pixel 5
pixel 10
Pulse shape of large pulses seen in the two pixels (smaller ones are later in time)At 10 V bias pulse becomes very wide(10 micro seconds) > so it looks like a real photo current
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Tube 291
-0.5
0
0.5
1
1.5
2
2.5
3
-4.00E-06 1.00E-06 6.00E-06
(s)
(V)
pixel 19 (x 50)
pixel 1
Two pulses seen in two opposite side pixelsHere PIXEL 1 is the biggest(smaller ones are later in time)
10
Tube 291
-0.2
0
0.2
0.4
0.6
0.8
1
-4.00E-06 1.00E-06 6.00E-06
(s)
(V)
pixel 19
pixel 1 (x 10)
Two pulses pulses seen in two opposite side pixelsHere PIXEL 19 is the biggest(smaller ones are always later in time)
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Tube 291 using QI-preamp on pixel 10 while triggered on pixel5
-0.40
-0.30
-0.20
-0.10
0.00
0.10
0.20
-2.00E-03 -1.00E-03 0.00E+00 1.00E-03 2.00E-03
(s)
(V)
pixel 5 triggered
pixel10 through Amplifier
Relation between Large and small noise signalsWe triggered on the big pulse in channel 5 and look at the amplified signal from Pixel 10 (small pulses disappear for some time after a big pulse )
AC coupling to scope
Total 4 ms
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Tube 291 using QI-preamp
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
-2.00E-02 0.00E+00 2.00E-02
(s)
(V)
pixel5 triggered
pixel10 amplified
Relation between Large and small noise signalsWe triggered on the big pulse in channel 5 and look at the amplified signal from Pixel 10 (small pulses disappear for some time after a big pulse )
Total 40 ms
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We also took data where we KNOW that we triggered on the pixel which was EARLIER in time and had the Amplifier on the one that “reacted” later.
(sorry, but the data on the file was corrupted and Brian is trying to recover it now…)
In this case, the later one did NOT have the small pulses either before or after the big pulse.
Thus, pixels with small pulses are the ones which start the “cascade” and the other pixels which follow have been quiet just before (and after).
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HV
10 M Voltmeter20 Mohm
OR
HPD HV gnd
RBX gnd
PC
diode
1G
VB
Scope on 50 ohm
Setup to look at the HV current on side walls of HPD (diode is isolated from this current path)
Cable capacitance
??
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HV vs current (B=0) HPD =~10Tohm
-1.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0 2 4 6 8 10 12
HV (kV)
Cu
rre
nt
(nA
)HV current to Ground through ~5Mohm Previous measured at CERN
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DC measured current to ground and noise counts measured in pedestal vs B ( B, E = 20 degree, HV=6 kV)
-1.4
-1.35
-1.3
-1.25
-1.2
-1.15
-1.1
-1.05
-1
0.0 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.4
B (Tesla)
Cu
rre
nt
in n
A
0
10
20
30
40
50
60
No
ise
ev
en
ts a
bo
ve
10
fC
DC current[nA]
noise counts
Correlation between DC measured current through the side-walls of HPD and Noise
17
-1
-0.5
0
0.5
1
1.5
-5.00E-07 5.00E-07(s)
(V)
current to ground (offset 1V and x10)
Pixel 1 (triggered)
Correlation between AC measured current through the side-walls of HPD and Large noise pulses(Pulse in the HV current is first) (negative so it is opposite from photo current)
18
-1
-0.5
0
0.5
1
1.5
-5.00E-07 5.00E-07(s)
(V)
current to ground (offset 1V and x10)
Pixel 1 (triggered)
Correlation between AC measured current through the side-walls of HPD and Large noise pulses(Pulse in the HV current is first) (negative so it is opposite from photo current)
19
-3
-2
-1
0
1
2
3
4
-2.00E-06 -1.00E-06 0.00E+00 1.00E-06 2.00E-06 3.00E-06 4.00E-06(s)
(V)
current to ground (offset 1V and x10)
Pixel 1 (triggered)
Correlation between AC measured current through the side-walls of HPD and Large noise pulses(Pulse in the HV current is first) (negative so it is opposite from photo current)
20
NO Angle
0
20
40
60
80
100
120
140
0 1 2 3 4 5
B (Tesla)
Bia
s C
urr
en
t(n
A)
HPD 291
HPD 503
HPD 193
The worst HPD has his noise completelyreduced at 4 Tesla(we did 18 hour test at 4 Tesla with no increase)(We are currently running the best one at 1.3 Tesla for a 1 day)