A barrel kapton hybrid with 12 "new
epi" ABCD3TA chips was irradiated in the
reactor
in Ljubljana in September 2001
The same setup was used as for the previous irradiation.
Results:
Trim DACs and thresholds spread:
No range setting problems observed after irradiation.
Trim DAC curves for all chips and
all ranges before
and after
irradiation.
The distribution of 50% points for all channels after
trimming is shown
here.
Evolution
of spread of 50% point with received fluence can be seen in this plot.
The chips were trimmed
(with 1fC pulse at Ipreamp=150 Ishaper=20) only before
irradiation and then the same trim DAC values were used for all measurements
in this plot.
Response curve:
Response curve is shown here.
Time walk:
Gain and Noise:
Gain and noise was measured from threshold scans done
with 4 charges , 1, 2, 3 and 4 fC
at shaper currents 20 and 30uA and preamp currents 100,
150, 200 and 250uA.
Here is the gain
and noise
evolution at Ipreamp = 100uA and Ishaper = 20uA.
Gain
and noise across the hybrid at Ipreamp = 100uA and Ishaper =
20uA.
Conclusions:
All chips were fully functional after irradiation.
Noise increased from 500 ENC before irradiation to 1000
ENC after irradiation (at
Ipreamp = 100uA and Ishaper = 20uA). This is for about
200 electrons more than
after irradiation with 3e14 protons/cm2 at PS (1.8e14
NIEL neutrons/cm2). But
this seems to be consistent with previous irradiation
where about the same difference
in noise increase was seen after irradiation at PS and
Ljubljana reactor.
