1. Noise Studies on APD and Crystals
We connected to a CV meter and to the test board for FPPA:
APD
APD+CRYSTALS
Capacitors
The goal is to see how different from a pure capacitors the APD or
APD+CRYSTALS systems are.

2. SET-UP

3. Capacitance measurements
The APD and APD+CRYSTAL
systems are identical,
with a capacitance
at full depletion of pF

4. Noise Measurements We studied the noise induced by the APD
or APD+CRYSTALS
as a function of the
bias voltage.
This noise is due to their
capacitance plus some
extra component...
Values for a pure capacitor:
598pF --> 1.2 mV
168pF --> 0.9 mV
0 pF --> 0.5 mV
550pF
168 pF

5. Comments - The noise generated by an APD is almost identical
to what is induced by an equivalent capacitor.
- The noise induced by the APD+CRYSTAL is very dependent
upon the conditions used (wrapping, no wrapping, ground, shields..)
In the best case it was a 20-30% higher than a pure APD.
- We need to study more realistics set-ups. ALVEOLA+....