Trip-t testing
progress report
modifications to test setup - hardware and software
SiPM pulse height spectra
linearity measurements
discriminator measurements
Mark Raymond - [email protected] - 16/11/05
1
Test set-up
LabVIEW
VME
Programmable
Digital Pattern
Generator
prog.
attenuator
ADC now integrated into
system – software written
to perform automated
linearity measurements
(using prog. attenuator)
and get SiPM pulse height
spectra
ck and trig.
ADC
~12 control lines
preamp int./reset
pipeline, multiplexer,
programming
level shift
dECL ->
2.5V CMOS
Qinj
Trip-t
Mark Raymond - [email protected] - 16/11/05
Scope
2
SiPM connection
connection method
Vbias
trip-t
3p3
1 MW
thin coax
50W
LED
82p
SiPM
would need to feed in small
current here to tune Vbias for
individual SiPM’s
short length (~15 cm) coax between SiPM and tript (at the moment)
SiPM connected between core and coax sheath (core carries bias voltage)
50W provides some kind of termination for the cable
charge split between two tript channels using different capacitor values to get high/low gain
Mark Raymond - [email protected] - 16/11/05
3
SiPM/tript results
single p.e. spectra (200,000 events)
Russian SiPM (CPTA – 600 pixels)
signal counts
1500
3
60x10
1000
preamp integrate:reset ratio
350ns:50ns
get blue distribution when led
switched off (~ 1 or 2 p.e.)
40
led
noise only
500
20
0
0
8.5
9.0
9.5
3
10.0x10
ADC units
Mark Raymond - [email protected] - 16/11/05
4
noise counts
led pulsed (20 ns) during
preamp integrate period
(red distribution)
R1 (0509-023)
39.0 V bias
11/11/05
SiPM/tript results – signal vs led pulse amplitude
limit of
high chan.
linear range
(~ 2 pC in
this case)
600
single p.e.
spectrum
visible
500
counts
400
increasing led pulse amplitude
high gain
channel
300
200
100
0
8.5
9.0
9.5
10.0
3
10.5
11.0x10
each distribution shows
the spectrum obtained
for a fixed led pulse
amplitude
ADC units
5000
counts
4000
3000
expand
2000
led saturating?
5000
4000
3000
2000
1000
0
low gain
channel
8480
8500
8520
8540
8560
8580
8600
1000
0
8.5
9.0
9.5
10.0
ADC units
Mark Raymond - [email protected] - 16/11/05
10.5
~ 25 pC
3
11.0x10
5
linearity studies
3
12.0x10
test charge injected via
programmable attenuator
~ 2 pC
11.5
different curves for different
values of tript discriminator
threshold voltage Vth.
high gain channel
ADC units
11.0
linearity not expected to be
that good for this version of
the chip (see Fermilab tript
test docs.)
10.5
~ linear
range
10.0
discontinuities occur at
different points depending
on programmed disc.
threshold setting
9.5
low gain channel
9.0
discontinuities occur where
signal crosses Vth - could be
due to crosstalk on chip or
test board
needs further study – may
need careful strategy to
calibrate out in system
8.5
0
5
10
15
20
25
charge injected [pC]
Mark Raymond - [email protected] - 16/11/05
6
discriminator timing studies – early result
1 V / div.
charge injection edge
tript discriminator output
5 ns / div.
td
discriminators outputs constantly
enabled so appear immediately
at chip O/P when they fire
measure td (scope)for many triggers
for different signal sizes
note: td also includes fixed cable delays
Mark Raymond - [email protected] - 16/11/05
7
discriminator timing studies – early result
600
Qin~600 fC
500
distributions show value of td (delay between charge injection edge
and disc. firing) for different values of charge, but for fixed value of
discriminator threshold setting
counts
400
300
200
take distribution mean values and
plot dependence on Qin
Qin~100 fC
100
0
30
35
40
45
50
td [nsec.]
actual disc. threshold value (~ 100 fC here)
in our system will depend on:
programmed Vth value
programmed tript gain
SiPM gain
external gain ratio capacitors
42
40
td [nsec]
points to note:
charge injection edge also contributes here
(~ 5 nsec => should deconvolve out)
44
this plot shows timewalk
dependence on signal size
38
36
34
32
30
28
0
100
200
300
400
500
600
Qin [fC]
=> many more careful and systematic measurements required here
Mark Raymond - [email protected] - 16/11/05
8
summary
tript results with SiPM encouraging
single p.e. spectra visible and charge splitting to get high/low gain channels works
linearity shows results consistent with previous chip measurements
discontinuities occuring when discriminators fire need further study – try to reduce and/or
understand how to manage in system
discriminator timing studies begun – more systematic study needed
our next priority
investigate performance dependence on connection cable length between SiPM and tript
look for degradation with cable length (noise, timing performance) – important to understand
from detector design perspective (how far can front end boards be from SiPM’s)
propose to try and do this with scintillator/wavelength shifting fibre -> SiPM system using
cosmics and external scintillator trigger system to get reference timestamp to compare
with SiPM/tript value
system currently under construction
Mark Raymond - [email protected] - 16/11/05
9
Photos
Trip-t (1st version)
charge injection split
between 2 adjacent
channels
2.5 V CMOS
control lines
Mark Raymond - [email protected] - 16/11/05
10
Photos
Trip-t board
dECL -> 2.5 V CMOS
level shift
ADC
digital pattern generator
dECL outputs
Mark Raymond - [email protected] - 16/11/05
11