X-ray testing of CMS BPIX Phase I modules

Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
X-ray testing of CMS BPIX Phase I modules
Pirmin Berger
26.08.2015
Pirmin Berger
PhD Seminar
August 26, 2015
1 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
TABLE OF C ONTENTS
1
Introduction
2
Module Testing
3
Bump-Bond testing
4
Vcal calibration
5
High-rate Efficiency
6
Read-out stability tests
7
Summary
Pirmin Berger
PhD Seminar
August 26, 2015
2 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
T HE CMS BARREL PIXEL DETECTOR
CMS Barrel
now
Sensor
Phase I
upgrade
Read-out
chip (x16)
Module
Pirmin Berger
PhD Seminar
August 26, 2015
3 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
M ODULE T ESTING
each component is tested before assembly at manufacturer or PSI
assembled module is tested at ETH
E LECTRICAL TESTS
test of electrical properties of read-out chip
⇒ see Vittorios talk
S ENSOR TEST
properties of sensor
X- RAY TEST
connection between sensor and read-out
high-rate efficiency
calibration
readout stability
Pirmin Berger
PhD Seminar
August 26, 2015
4 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
B UMP -B ONDS
B UMP B ONDS
bump-bonds connect pixel cell on
sensor and pixel unit cell on read-out
chip
can be missing or damaged
use x-rays to test modules (easier to
handle than particles like protons,
electrons etc.)
Pirmin Berger
PhD Seminar
August 26, 2015
5 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
X- RAY - H ITMAP
x-ray hit-map shows large differences in number of hits per pixel
HDI (high density interconnect), cable and other electrical
components on top of the module absorb X-rays
Pirmin Berger
PhD Seminar
August 26, 2015
6 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
B UMP -B OND TESTING - H ITMAP
x-ray hit rate ≈ 100 MHz/cm2 for few minutes
pixels with no hits have missing/broken bump bonds (if they are
electrically good)
few missing bumps like shown here are still tolerable
Pirmin Berger
PhD Seminar
August 26, 2015
7 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
B UMP -B OND AND TEST- PULSES
read-out can also be tested
with test pulses instead of real
particles
voltage of test-pulses can be
controlled with VCal DAC
setting
want to calibrate:
VCal ⇔ electrons
how?
via pulse height information
calibration of VCal is important for electrical tests to convert
results or set parameters (eg. threshold) to physical units!
Pirmin Berger
PhD Seminar
August 26, 2015
8 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
V CAL CALIBRATION
need to know number of electrons ⇒
flourescence spectra
4 different metal targets with different
fluorescence lines
fit number of electrons vs pulse height
Pirmin Berger
PhD Seminar
August 26, 2015
9 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
V CAL CALIBRATION
# ROCs
Vcal calibration slope
102
10
1
30
35
40
45
50
55
60
e^-/Vcal[DAC]
result ≈ 47 e− /VCal
we now can use test-pulses to simulate particle hits!
eg. particle that creates 10,000 e− ⇒ VCal 213
Pirmin Berger
PhD Seminar
August 26, 2015
10 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
HR E FFICIENCY ANALYSIS
fiducial efficiency M2020 ROC 0
illuminate modules with X-rays
1
0.998
send test-pulses, check how
many are read out
0.996
0.994
0.992
Nreadout / Nsent ⇒ efficiency!
0.99
0.988
eff at 120Mhz/cm2: 0.990613 +/- 0.000429
0.986
cubic fit: 0.999248 - 4.996976e-09 *x^3
0.984
20
40
60
Pirmin Berger
80
100
120
140
target rate layer 2:
120 MHz/cm2 ⇒ ≈ 99.3%
PhD Seminar
August 26, 2015
11 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
R EAD - OUT STABILITY TESTS
Read. Unif. over Time 150: C7
30000
25000
Hits
20000
15000
10000
5000
0
0
×103
2000 4000 6000 8000 10000
Event
several more tests to detect problems with readout
eg. ≈ 30 minutes readout stability test (number of hits per time
unit) at hit rates comparable to Layer 2 expected rate
Pirmin Berger
PhD Seminar
August 26, 2015
12 / 13
Introduction
Module Testing
Bump-Bond testing
Vcal calibration
High-rate Efficiency
Read-out stability tests
Summary
S UMMARY
Reasons why X-ray tests are done:
connection of sensor to read-out chip can be verified (bump
bonds)
efficiency can be measured
test-pulses can be calibrated (Vcal calibration)
various read-out problems can be detected
Pirmin Berger
PhD Seminar
August 26, 2015
13 / 13