Transcript Program of tests

Program of tests (I)
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The most urgent is to do measurements to allow to select the
best candidate among the "modified HCAL design" and the
mixed "ECAL-HCAL design". This should then be followed by
a test on a line for the best candidate with about 20 PMTs
The designs should include the series 5.6K and the extra ground
wire to decrease the CW pick up noise.
Most important is to have a detailed understanding of the
behaviour and therefore scope pictures at different points on the
CW circuit : OP AMP output, base and emitter and collector of
T1, collector of T2
August 28th 2008
1
Jacques Lefrancois
Some explanations HCAL-type design Operation
When T3 is on and T2
off the CW pumping
voltage is at max
(medium voltage) since
transistorT2 is off T1
saturates completely,
then T3 is off and T2
and T1 are on T1 goes
out of saturation and
gives a current spike
but the collector of
T2,T3 goes to a lower
voltage determined by
the current in T1
C3=100pfd,
R3=62K(?)
August 28th 2008
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Jacques Lefrancois
Some explanations Mixed-type design Operation
There are two
feedback loops: the
fast feedback R3C3
limits the gain of the
OPAM at about 1.1
at 60KHz, so the
OPAMP does not
saturates from
switching swing on
C2 caryed by C1 to
the input. Because
of the C1 feedback
the OPAMP
presents a huge
equivalent capacity
at the input and the
OPAMP this
stabilize low
frequency instability
mixedECAL-HCAL C2=47nfd ,C1=410pfd C3=800pfd R3=50K
August 28th 2008
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Jacques Lefrancois
Program of tests- stability
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Verify in both design the voltages on critical points and how far
we are from OPAMP saturation.
Verify the insensitivity to +-6v variation
Verify insensitivity to medium voltage variation
Measure the noise induced on the M V input when the MV
power supply is insulated by 100 ohms
Inject 60KHz noise on the MV line thru an oscillator verify the
effect at various points.
Inject low frequency noise on control line (10Hz?) verify the
effect.
The problem of medium voltage current in absence of voltage
has to be understood.
August 28th 2008
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Jacques Lefrancois
Program of tests: safety at turn-on turn-off
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Measure behaviour at turn-on and turn-off on various points;
check spikes at OPAMP input or output.
August 28th 2008
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Jacques Lefrancois
Program of tests: CW noise
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CW noise can be checked with the scope but should be
measured with a FEB in various conditions of control voltage
and medium voltage.
It might be preferable to have CW boards with PMT for the
noise test because of extra stray capacity (is it possible?)
August 28th 2008
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Jacques Lefrancois