Here are some comments on HQV810 x-talk.

1. Input test pulse: 200 fc (20 mV on 10 pf). This replicates full charge
amplitude with 6kV x-rays (correspnds to 1.25 Me-, i.e. a detector gain
of about 5000, as expected).

2. This produces an output pulse (end of the line) of ~330 mV. Keep this
in mind when comparing with x-talk signals.

3. Our HQV810 16 channel circuit is made up of 2 x 8 channels chips. I do
not observe any signals in the channels of one chip when pulse is injected
into the other. An exception is some propagation between the last channel
of chip 1 and the first of chip 2. There a small (fast) blip of 1 mV
(.3%) is found. On the whole there is no chip-chip cross talk. Hence
Ernie's setup seems OK and x-talk is internal to the HQV810.

On single chips then the following 3 types of signal "propagation is
observed"

A. "Far away channels": for channels beyond the first neighbour of the
channel which receives the test pulse, a fast spike, sometimes with a fast
positive overshoot is observed. The time scale for those pulses is same as
induced pulses. They are usually of the order of 2 mV (+ and -), i.e. .6%
of main pulse.

B. "First neighbour": first neighbours get a unipolar negative pulse which
looks like induced pulses but are only 5 mV (1.5% of main pulse)

C. "Real x-talk": some first neighbours, in addition to signal described
in B get a long time constant +ve overshoot which resembles the main pulse
with an amplitude of 4 to 5.5 mV (1.3 to 1.7 %).

Comments: Signals type "A" can be neglected. Signals type "B" would appear
to present problems because they could represent a sizable fraction of an
induced pulse, which themselves varied in amplitude from 0 to 20 or 30
mV. However, in our runs, first neighbours in the HQV810 modules were
never 1st neighbours on the readout hex pattern but they are oftwn
2nd neighbours. Only pads pairs (2,4) and (6,8) are actually 1st
neighbours inside the HQV810 modules.

The cross-talk described in "C" was found between the following HQV810
channel pairs (also given in terms of pad number pairs and Dean's
analysis numbers):
 

HQV810#	Hex readout#	Dean's #
16,15	32,31	N.A.
12,11	28,27	N.A.
11,10	27,26	(6,8)
10,9	26,25	N.A.
8,7	24,23	N.A.
7,6	23,22	N.A.
6,5	22,21	(2,4)
4,3	20,19	N.A.
3,2	19,18	N.A.
2,1	18,17	N.A.

Note that x-talk between 1st neighbour HQV810 channels appears to be the
rule rather than the exception. Dean only saw some x-talk between 1 or 2
pairs because our group of 7 pads include pad numbers: 19, 21, 22, 24, 26,
27, 29. BAsically, we were usually only looking at one half of the
x-talking pairs.