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Insertable B
-
Layer




Technical Design Report

Addendum



Issue:

1

Revision:

6

Reference:

ATLAS TDR 19 Addendum, CERN/LHCC 2012
-
xxx

Created:

1 March 2012

Last modified:

10

May

201
2

Prepared By:

ATLAS IBL Community















































All trademarks, copyright names and products referred to in this document are acknowledged as such.



ATLAS TDR 19

Addendum

11

May 2012





ATLAS

Insertable

B
-
Layer

Technical

Design

Report
Addendum




ATLAS Collaboration





ABSTRACT:


This document is an addendum of the ATLAS IBL TDR of September 2010. This document describes
the most significant changes to the project since that time and provides an update on several
technology choices. In particular it discusses the “Mixed Scenario”

where staves are considered to be
populated in the centre with two
-
chip planar sensor modules and with single
-
chip 3D sensors at the
two extremities. Several related changes to the services design and a more detailed description of the
stave assembly pr
oc
edure are included. Finally,
the proposed diamond beam monitor is presented,
which uses the same FE
-
I4 ASIC together with diamond sensors originally developed a
s part of the IBL
R&D program
.









KEYWORDS
: ATLAS, LHC, HL
-
LHC

Phase 0
, Upgrade, Pixel Det
ector, Insertable B
-
Layer, IBL, CERN







Content

INTRODUCTION

................................
................................
................................
.....................

5

1

SENSOR QUALIFICATION

AND PRODUCTION STATU
S

................................
..............

5

2

MIXED SENSOR SCENARI
O

................................
................................
............................

7

2.1

Module Design.

................................
................................
................................
................................
................................
.
7

2.2

Stave Layout

................................
................................
................................
................................
................................
.....
9

2.3

Module Loading on Stave

................................
................................
................................
................................
...............
9

2.4

Electrical services
................................
................................
................................
................................
...........................

11

3

DIAMOND BEAM MONITOR

(DBM)

................................
................................
...............

12

ACKNOWLEDGEMENTS

................................
................................
................................
.....

14

REFERENCES

................................
................................
................................
......................

15



I
ntroduction

At the time the IBL TDR was submitted in September 2010

(see reference
[1]

Section 1.1
) the machine schedule
implied installation of this detector should target a long shutdown in 2016. Subsequent changes in schedule and
excellent progress with the prototyping have
led ATLAS to adopt a more aggressive schedule with installation now
targeting the first long shutdown in 2013/14. Section
1

of this document describes the changes
to the project planning,
with respect to those in reference
[1]

Section 11.3
, that make this possible.

In the IBL TDR

the sensor technology

choices were
not
yet
decided. Three technologies were considered: planar
sensors (n
-
on
-
n and n
-
on
-
p), 3D sensors (with active or slim edge) and diamond
sens
ors

(
[1]

Section 3
.
2
)
. A pro
gram
me

of extensive testing of detector assemblies irradiated to IBL fluence of 5x10
15

n
eq
/cm
2

and 250 Mrad was carried
out
through

the Spring of 2011.
Successful r
esults
with the main technologies suitable for an accelerated schedule (planar n
-
in
-
n and 3D

with slim edge)
were presented to
a

sensor technology review in July 2011. The review panel
recommendation was to investigate a “mixed scenario”, in which the 3D technology populates the
highest eta region of
the IBL

where the tracking could

benefit from

the electrode orientation
,

in terms of

better z
-
resolution
,

after heavy
irradiation. The implications of the IBL “mixed scenario”
are

presented in section
2

of th
is Addendum document with
emphasis on how this affects

the module, stave and services design.

This proposed technology choice implies a number of changes to the stave module loading (
[1]

Section 4.4
) and
electrical design (
[1]

Section 4.3
)
.

These are described in sections
2.3

and
2.4
, respectively, below. These sections also
present updates on these aspects with respect to the original document.

F
inally, t
he
newly proposed
Diamond Beam Monitor (DBM)
[5]

is presented in section
3
, which is a spin
-
off from the
IBL
sensor
technology

R&D studies

with prototype assemblies of FE
-
I4 and diamond sensors. The DBM is a detector
that is constructed by the IBL collaboration and will only be installed, if the existing ATLAS Pixel detector
is

brought
to
the
surface
in 2013 to replace

the Service Quarter Pa
nels (nSQP

)
[5]
.

The overall project costs, cost sharing and cost breakdowns are all presented in reference

[5]
.

1

Sensor Qualification and Production Status

Between the end of 2010 and early 2011, the plans for construction of the IBL were substantially modified by two
events
: the change in
schedule for
the LHC long shutdown
s


(ne
eded

to install the IBL) and the very
successful

results
with

the FE
-
I4A front
-
end chip
. The latter

raised confidence that only minor changes would be needed for the
production version

of this chip
.

The LHC shutdown to install the IBL, assumed in the
IBL TDR, was for the end of 2015. The decision
to continue
running the LHC in 2012
(Chamonix 2011)
and
to have a long shutdown in 2013/14
offered

ATLAS the serious
possibility to install the IBL
two years earlier
. From all the sensor technologies under stu
dy for IBL the two that were
more advanced and
at
a

sufficiently

mature stage for possible production were: planar
thin edge
n
-
in
-
n and double
-
side
d

thin edge
3D sensors. It was therefore decided to restrict the qualification to these two technologies and
develop FE
-
I4
modules
from these two
to
be
fully qualif
ied

in test
-
beam
studies
and at

the

full IBL radiation dose. To fulfil this “spe
e
d
up schedule” it was decided, in January 2011, to launch a pre
-
production of planar sensors from CiS
1

and of double
side
d

3D sensors from CNM
2

and FBK
3
.
A further
idea behind

these production runs was to
already
have
between 30%
and

50% of the sensors
available
by the time of the qualification
deadline

and sensor review.

The path chosen to streamline the

sensor prototyping and decision, the success of version A of the FE
-
I4, with only
minor modification requirements, together with the high production yield, also streamlined the production of the FE
-
I4B by making engineering and production in an single run
. Together these saved over one year in the IBL schedule.
Further optimization and reduction of the originally generous contingency in the schedule gained the needed time to be
ready for the “Phase
-
0” LHC shutdown in 2013/14.
Figure
1

compares the IBL TDR schedule with the present schedule
for the major detector items. The FE
-
I4B and sensor production were almost completed as of March 31
st

2012, meeting
the new schedul
e for these critical items.

The recommendation from the
sensor
review panel
, in July 2011,

we
re that both
sensor
technologies fulfil
led

the IBL
requirements, and that there
wa
s an opportunity to populate the forward region with 3D where the tracking could
take
advantage of the
vertical
electrode orientation
which could offer

a better z
-
resolution after heavy irradiation.




1

CiS:
Forschungsinstitut fur Mikrosensorik und Photovoltaik GmbH, Konrad
-
Zus
e
-
Strasse 14, 99099 Erfurt, Ger
many

2

CNM:
Centro Nacional de Microelectronica (CNM
-
IMB
-
CSIC), Campus Universidad Autonoma de Barcelona, 08193
Bellaterra (Barcelona),

Spain. See
http://www.imbcnm.csic.es
.

3

FBK:
Fondazione Bruno Kessler (FBK), Via Sommarive 18, 38123 Povo di Trento, Italy. See
http://www.fbk.eu
.

The IBL collaboration, following th
at

recommendation from the review panel, decided to complete the production of
planar and 3D sensors a
nd endorsed the proposal to build enough modules for a mixed IBL sensor scenario where 25%
of 3D modules populate the forward and backward part of e
ach

stave.
The

production of planar sensors will also allow
coverage of 100% of

the

IBL
,

in case th
at option

was required.

The fractions of planar and 3D sensors that can be put in
the IBL are quantized by the granularity of the high voltage services, which individually bias a group of four FE
-
I4
equivalent area of sensors (i.e. 4 FE
-
I4 out of 32 in a stave).

Pr
eserving b
ackward/forward symmetry

of the IBL

restricts
to

multiple
s

of 25% the fraction of planar/3D that can populate each stave.



Figure
1
:

Comparison between the IBL TDR schedule (version v.3) and the version prepared for the IBL installation in the
2013/14 LHC shutdown. The comparison is made for the major production items going into the detector.



Batch #

1

2

3

4

5

6

Total

Received wafers

20

22

18

20

17

22

119

Good DC
sensors

69

76

64

70

62

83

424

Yield

86.3 %

86.4 %

89.9 %

87.5 %

91.2 %

94.3 %

89.1%

Table
1
:

Status of two
-
chip planar sensor production at the end of March 2012. The IBL in the 75% of planar
scenario has 168
sensors.

Table
1

and
Table
2

show a summary of the planar an
d 3D sensor production as of the 31
st

of March 2012. There are
enough sensors from both technologies to fulfil the mixed scenario, considering the expected overall yield for the
module production and stave loading.

In addition to the sensor qualification and production, thin modules have been developed with both sensor technologies,
making single and double
-
chip assemblies. The prototyping was carried out with 100 µm and 150 µm thin FE
-
I4A
chips. For the aggressive I
BL installation plan, it was decided to use the 150 µm thickness to avoid unexpected yields
issues.



Status

Produced
Wafers

Selected
Wafers

Yiel
d
on
selected

Good
sensors


FBK
-
A10

Completed

20

12

60 %

58


FBK
-
A11

Completed

12

4

44 %

14


FBK
-
A12

Completed

16

13

60 %

63


FBK
-
A13

In proc. (backup batch)

-

-

-


CNM
-
1

Completed

19

18

60 %

86


CNM
-
2

Completed

17

15

71 %

85


CNM
-
3

In proc.

-

-

-

-

Total



62

62 %

306

Table
2
:

Status of planar single
-
chip 3D sensor
production at the end of March 2012. The IBL, in the 25% of 3D scenario, has
112 sensors.

28.09.2011
16.09.2011
28.11.2011
26.10.2012
333


16.09.2011
09.12.2011
84


26.08.2011
24.02.2012
182


28.02.2011
03.02.2012
340


19.08.2011
17.08.2011
2
-






01.01.2011
03.02.2012
398


09.04.2012
25.06.2013
442


27.09.2011
17.10.2012
386


27.08.2012
16.09.2013
385


27.04.2012
18.01.2013
266


21.11.2011
24.08.2012
277


09.01.2012
22.11.2012
318


30.07.2013
21.03.2014
234


12.07.2012
20.03.2013
251


S
ch
e
du
l
e

v
3

(
r
e
a
dy

f
o
r

i
n
sta
l
l
a
ti
o
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i
n

2
0
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5
)
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f
o
r

i
n
sta
l
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ti
o
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(
1
8
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0
5
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2
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)
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v
5
.
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a

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r
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.
2
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)
B
a
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sta
v
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pr
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cti
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&

Q
A
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-
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a
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2
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2
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1
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2013
2014
2015
1
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1
2
3
T
as
k

N
am
e
S
t
ar
t
End
D
ay
s
2011
2012
4

Table
3

summarizes the production of thin modules. Several such modules have been dressed with the flex
hybrids and are ready

to be installed on “stave 0”.


FE
-
I4

Thickness

Planar (200µm)


S
ingle
Chip



D
ouble
C
hip

3D (230µm)

S
ingle
C
hip

Total

FE
-
I4


100 µm

4

22

7

55


150 µm

16

17

20

70

Total

20

39

27

125

Table
3
.

Modules bump
-
bonded at IZM
4

with thin FE
-
I4A chips to qualify the stave assembly procedure.


2


Mixed Sensor Scenario

This section describes the main changes from the IBL TDR
stave
design

of reference
[1]

Sections 3 and 4

to
execute

the
mixed sensor scenario. The impact of the mixed
sensor
scenario on the IBL construction
is

on the following items:



Module
design (IBL TDR
[1]

Section 3
).




Stave layout

(IBL TDR
[1]

Section 4.1
)
.



Module loading on stave

(IBL TDR
[1]

Section 4.4
)
.



Electrical services

(IBL TDR
[1]

Section 4.3
)
.


2.1

Modu
le Design.

The IBL module outlines for two
-
chip modules and one
-
chip modules are geometrical
ly

compatible; the physical size of
two single
-
chip 3D sensor assemblies
i
s the same width as a
single
planar two
-
chip module. The differences in r


between the two

sensor

technologie
s are compatible with the overall IBL envelopes.
In
Table
4

are listed the geometric
parameters for the sensors used in the IBL mixed scenario.


Table
4
:

Main geometrical parameters of the
IBL sensors used for planar and 3D sensor modules.


Bare module assemblies are dressed by gluing a flex hybrid circuit
[8]

on the sensor side; there are two circuit
s, one for
single
-
chip 3D assembly and another for the planar double
-
chip assembly. Such circuits are shown in
Figure
2
. They are
mechanically different, but electrically very similar once the test pigtail is cut. Having two flex
-
circuits eases the
assembly procedure, but does not change the electrical connect
ions, which will basically remain separate for each

of the
two FE
-
I4 chips

in the double
-
chip version
. In the case of the double
-
chip module flex, there
are

two
separate

wire
-
bonding
fields

that bring the signals from the stave flex “wings” together. The c
onnection step, once the modules are on
the stave, is the same for
two
single and
one
double module. In this way the stave flex
connections are
compatible for
either single or double chip

modules.
A few special precautions have been used in the design of t
he module flex:



The back of the flex (which is glued on the module)
uses

a 25µm thick polyimide film based coverlay
5

which
is rated to stand 100V/µm to hold the 1000V needed by the planar modules once they have received their full



4

Fraunhofer IZM
-
Berlin, Gustav
-
Meyer
-
Allee 25, 1335
5 Berlin

5

SF302C
polyimide

film from
Shengyi

(
http://www.syst.com.cn/en/index.html
)

Structure

Planar

3D

Gap b/w modules

205 µm

205 µm

Sensor thickness

200 µm

230 µm

Module width (along z)

41 315 µm

20 450 µm

Bias tab / guard
-
ring extension (in r

)

630 µm

1 230 µm

integrated radiation dose
. It was sensible to
do

the same for the 3D modules, even if it is planned to have
between
160

and
180 V as the maximum operation voltage.
The extra

radiation length is
very small
.



The high voltage capacitors
are

encapsulated using an isolating resin.
The

prime

candidate is a Polyurethane
resin (PUR)
6

that was used for the ATLAS SCT.





Figure
2
:

Module Flex Hybrid for single chip (left) and double chip module (right). The flexes come with a pigtail and a test
connector,
which is cut away before loading on stave. The stave flex wing is glued on the module flex and then connections are
provided by wire bonding. The double chip flex is electrically equivalent to two single chip ones.


The clock and data signals, which are in
dividual lines on the stave flex, are routed separately on the double module flex
to the input of
each

FE
-
I4. Each line is terminated with a 160Ω resistance. This is acceptable
as

the two stubs only 4 cm
long and the frequency of the signals are 40/20 MHz
for the clock/data.



The two
FE
-
I4 chip
s on a single module are differentiated by having their

ID addresses
connected to

a pull
-
up
wire
-
bond connect
ed

to VDD.

For the double
-
chip module,
the

additional wire
-
bond is used for only one of the
two chips.
When
the
single
-
chip module
s are mounted on a stave
, the wire
-
bond of one of the two chips
making a logical module will have the

ID address

wire
-
bond
removed
.



The module flexes are produced with a surrounding frame having precision holes for positioning pins in

the
mounting jigs.
This frame eases the module assembl
y procedure (module flex gluing and
wire
-
bo
nding); the
handling of the devices during the qualification steps and the shipment to the stave loading
site
.
When the
pigtail is cut,
the

frames are remov
ed and the modules can then picked up by vacuum tools. This is done at the
last moment, before loading to the stave.

All tooling and jigs for assembling the modules are made such as to be compatible with both designs.

The module testing is done using the
USBPix
readout

system. Two USB
P
ix systems are connected in master/slave
configuration
and can be used to test either

double
-
chip

and single
-
chip modules through

a specific

adapter card. Both
single and double
-
chip modules use the same adapter cards; double

modules use
an
additional pin for the extra signal on
the test connector.





6

VU 4453 from Peters (
www.peters.de
).

2.2

Stave Layout

The mixed sensor scenario stave layout is shown
in
Figure
3
. The

3D sensors populate the 2 extremities. The area
covered with planar and 3D sensors is, respectively, 75 % (equivalent to 24 FE
-
I4 chips) and 25 % (equivalent to
4+4
FE
-
I4 chips). The mod
ules have a fixed gap of 205 µm.


Figure
3
:

Stave layout for the mixed sensor scenario. 3D sensor modules populate the two stave extremities. The gaps
betweenneighbouring modules is fixed at 0.205

mm.








Figure
4
:

Stave cross sections at the position of a planar module (top) and a 3D module (bottom).



The planar and 3D
modules
differ slightly in
sensor
thickness:
from

200 µm
to

230 µm; and in r


where
the 3D
modules are
700 µm
wider
. The
3D design is compliant for the double and single sided design (active edge), having the
second one the high voltage connection being made on the same side as the bump
-
bonding. For this compliant reason
the sensor extends beyond the FE
-
I4.
Figure
4

shows a cross
-
section of the stave, (top) at the position of a planar
double
-
chip module and (bottom) at the position of a 3D

single
-
chip module
.


2.3

Module Loading o
n Stave

The module loading integrates the stave and stave
-
flex together with the planar and 3D detector modules while targeting
for the highest quality in term of working pixel and modules and the long term reliability. The 15 procedural steps,
followed by

the module loading and QA sites are:

1.

The reception of the completed stave with the stave
-
flex. This is part of the QA to validate that the stave with
the glued stave
-
flex has a conformal geometry after it has been thermally cycled 10 times from
-
40°C to
+40°C.

2.

The reception tests of modules. Detector modules qualified at the assembly sites pass visual inspection and
basic electrical readout tests at loading site, before the module
-
flex test pigtail is cut to load them on the stave.

3.

A “Guillotine tool” cut
s the module pigtail. The next operation consists in the
removing the wire bonds from
the pads that will be re
-
used to connect the stave
-
flex wings. These same pads were previously used to
electrically connect the module test pigtail before loading the mod
ule to the stave (see
Figure
2
).

4.

The modules are loaded on the first half of the stave (
Figure
5
). Six planar and four 3D modules are positioned
using precise mechanical references (dowel pins). Module placement accuracy is based on the sensor dicing
accuracy, which is +/
-

10 microns. Th
e gap between modules of 205 µm (see
Figure
3
) is fixed by polyimide
-
coated shims that have a thickness of 190 µm.

5.

The modules are loaded on the second half stave wit
h the same positioning technique.

6.

The 32 flex
-
wings
that are retracted during loading are then released and glued on the module flex with
Araldite 2011 (epoxy glue) (see
Figure
5
).

7.

Once the wings are glued, the electrical interconnection

between the module
-
flex and the stave
-
flex (wings) is
done by wire
-
bonding. Multiple wire
-
bonds are used for redundancy. The connections bring out FE
-
I4 power
and I/O LVDS signals, sen
sor bias and connections to NTC temperature sensors placed on the module
-
flexes.
Test wire
-
bonds are then pulled to control the quality of the wire
-
bonding process.

8.

The loaded stave is electrically connected through an adapter card to the readout system an
d cooled by a CO
2
system. This step qualifies the stave in near real operating conditions. Reworking is done in case as needed
before shipping to CERN for integration into the IBL.


9.

The module positions are surveyed with respect to stave references.

10.

The complete stave is thermally cycled. Ten thermal cycles from
-
40°C to +40°C are foreseen in the QC
procedure. Assembly weaknesses and infant mortality are detected and corrected in this way.



11.

The survey is repeated
and
the
results
are compared with t
hose

from step
9
. If displacement
s

or distortion
s are

seen
, rework will be considered. Such positions are recorded and will be used for initial alignment of the
detector modules in the IBL.

12.

A complete functional test with cooling and readout is performed.
This test checks integrity and full
functionality of all the modules. Bump integrity can be checked with pixel noise measurements. Pixels that
have lower noise without sensor bias and that have no difference with bias on/off have high probability to be
dis
connected from the sensor.

13.

Adherence to the IBL
envelope is
verified. This is particularly critical with respect the neighboring IBL staves
where the minimum distance is as small as 0.8 mm. Stave
-
flex wings will be the subjects of the highest
attention.

14.

Th
e last operations on the stave are to add an insulation spacer in the gap between module groups sharing the
same sensor bias and a spacer protecting wire
-
bonds from mechanical damage from touching another stave
during integration in IBL.

15.

The stave is fina
lly transported to CERN SR1 surface building for extensive QA test: burn
-
in, source scan and
cosmic tests.

Each stave, before loading with modules, is mounted onto a “handling frame”
support jig (see
Figure
6
). The stave stays
on the handling frame for all of its life, until it is integrated as a long (7 m) object (stave + internal services) around t
he
beam
-
pipe in the IBL. This minimizes mechanical stress in handling
staves. The handling frame is made of carbon fibre
reinforced plastic (CFRP). Its CTE is about zero and very close to that of the stave. In this way thermal excursions
during the thermal cycles do not induce mechanical stresses.

Module thermal contact to
the stave is guaranteed by thermal grease, which has been qualified for IBL radiation
requirements. Two drops of araldite are added to mechanically stabilize the module attachment to stave.

The loading tools consist of almost 80 mechanical parts that are
linked to the cradles for the various operations
. A few
of them are specific to the module geometry like: the grease mask, the alignment ruler and guides, the loading weight.
The basic tooling set is therefore compatible for a scenario with different fract
ions of 3D and planar sensor modules:
25/75 mixed scenario or, in case is needed, full planar scenario.


2.4

Electrical services

Electrical services have been designed maintaining compatibility between planar and 3D sensors. In particular the high
voltage
maximum rating of all the component
s

is

designed for 1000 V
,

needed
to bias the

planar sensor
s

when they
reach the
ir full radiation dose.









Figure
5
:
Tooling to load modules on stave. On the right side are visible four 3D

single
-
chip modules, while another six double
-
chip planar modules are shown toward the centre of the stave. Modules are positioned with respect to the cut edge of the
sensors. In the 200µm gap between modules a PEEK spacer is inserted to electrically isol
ate neighbouring sensors. Bottom left
illustration shows a planar module loaded with ~40g. The bottom right illustration shows the wing to module flex gluing
operation with a jig defining the wing shape during the polymerization.


The modularity in the
sensor bias voltage was decided as best compromise between having every single sensor tile
controlled individually and the constraints from service routing. This modularity was defined in the IBL TDR (
[1]

Section 4.5
) being a sensor area equivalent to four FE
-
I4 chips. This is maintained in the mixed scenario. The planar and
3D sensors will see quite different operating voltages before and after irradiation. For this

reason they need to be
connected to separate HV supplies. This constraint, together with the modularity in the sensor power distribution,
requires a minimum modularity of four FE
-
I4 chips equivalent in area for each sensor flavour. The additional
backward
-
forward symmetry in the stave limits to multiples of 25% (8 out of 32 FE
-
I4 chip area per stave) the coverage
with either of the technologies. The 25% (3D) / 75% (planar) scenario will use two bias lines for the 3D and six lines
for the planar sensors in
each stave. For the 3D it is planned to use sensors from both CNM and FBK. They are similar
in operational voltage, but for optimal control of the operational settings each HV channel will be connected to only one
of the 3D sensor flavours.

The bias curre
nt requirement for the HV power supply is defined by the sensor leakage current after the integrated dose
at the operation temperature. From measurements made during the sensor qualification phase it is found that the planar
and 3D sensor have similar curr
ents, between 300 and 400 µA for the area of a single FE
-
I4 chip at
-
15ºC and after a
dose of
5x10
15

n
eq
/cm
2

[2]
. The difference in the range of operating voltages between planar and 3D suggests the
selection of different models of HV power supplies. The two models of power supplies from iseg
7
:



Mod.
EH
S F205n_R51
: V
outnom

= 500 V / I
outnom

= 10 mA per channe
l



Mod.
EHS F210n_R51
: V
outnom

=
1000

V / I
outnom

= 10 mA per channe
l



is an optimal solution to fulfil the sensor requirements. The exisiting ATLAS pixel detector uses HV power
supply from the same se
ries. This will simplify the control and monitor software in the experiment.





Figure
6
:
CFRP Handling Frame holding a real stave with mechanical fixation at the two end
-
blocks and at the middle of the
stave (mounted as
integrated around the beam pipe). One handling frame is dedicated per loaded stave for all loading, QA and
integration operations.


3

Diamond Beam Monitor (DBM)

Beam monitoring, luminosity measurement and tracking in ATLAS, in the future, must continue to op
erate in radiation
environments at least an order of magnitude harsher than experienced by the current detectors. It is observed that, as the
environment becomes harsher, it becomes very challenging for detectors lacking fine spatial or timing granularity
to
separate signal from background. To remedy this problem, detectors close to the interaction region are becoming ever
more highly spatially segmented. It is proposed to add a Diamond Beam Monitor (DBM)
[5]

to ATLAS, which is a
spatially segmented upgrade to complement the timing granularity of the existing Beam Crossing Monitor (BCM).

Chemical Vapour Deposition (CVD) diamond has a number of properties that make i
t an attractive alternative for high
-
energy physics detector applications. Its large band
-
gap (5.5 eV) and large displacement energy (42 eV/atom) make it a
material that is inherently radiation tolerant in terms of the very low leakage currents, even at ex
treme fluences. It also
offers a very high thermal conductivity. ATLAS already uses this material in its highly time
-
segmented (sub
-
ns) BCM



7

iseg GmbH, Bautzner Landstr. 23, D
-
01454 Radeberg / OT Rossendorf

that provides stable luminosity measurements and detailed background characterisations in both during stable beams
a
nd while the LHC machine is setting up for collisions.

The DBM capitalises on R&D undertaken for the proposal to use diamond as the IBL sensor technology. Twenty
single
-
chip FE
-
I4 modules with diamond sensors in 2011 have been produced. When the IBL inser
tion schedule was
advanced to 2013 it was proposed to install 24, single
-
chip IBL modules, with diamond sensors in the forward region of
ATLAS, at r = 65 mm from the beam line and |z| ~ 1m, at rapidities from 3.0 to 3.4.
Figure
7

shows two views of the
DBM telescopes (on one side of ATLAS


the full system has similar arrangements on both sides of ATLAS). Each

telescope consists of three single
-
chip sensors, spread over

a 10 cm lever arm. Parametric tracking simulations show
this arrangement gives impact parameter resolution of better than 1 mm for tracks from the interaction point (IP) which
allows them to be readily distinguished from charged particles originating in t
he up/down
-
stream collimators.





Figure
7
:

CAD view of the DBM telescopes inside the new Service Quarter Panels (nSQP
). Left: An isometric view of the four
telescopes, with their type
-
0 cables (orange) and PP0 patch panels (green) mounted on the innermost nSQP cruciform. Right:
Details of the DBM cooling channel (blue) and it’s connection to the from SQP cooling channel
(red) between the quarter panel
(brown) that will be in place when the DBM telescopes are mounted in July 2013.


-
crossing) an average of 4 tracks per telescope from the IP are
expected. Initial pattern reco
gnition studies show that the DBM modules will have the granularity to un
-
ambiguously
reconstruct 10 or more tracks per telescope arm with low fake
-
rates. A full GEANT model of the DBM is being
implemented in the ALTAS/IBL/Pixel simulation and will allow p
erformance studies for proton collisions, detector
albedo/afterglow and representative beam loss and beam
-
one expects to acquire 10,000 tracks per bunch
-
crossing over a period of one minute, allowing

a 1% precision on the
bunch
-
by
-
bunch luminosity on a time
-
scale comparable to the basic ATLAS luminosity block. This should not only
preserve the precision of the current BCM luminosity measurements, as the LHC rates continue to increase, but also
make it

more robust for higher doses with correspondingly higher albedo and background rates.

Beyond the DBM patch
-
panel 0 (the green quarter
-
circle boards
in
Figure
7
) the
signals are bundled into cables that are
identical to the IBL half
-
staves. These, in turn, will feed standard IBL type
-
2 services and IBL RODs. The DBM event
fragments will appear as two additional IBL half
-
stave. The DBM channels will have twelve FE
-
I4 ch
ips’ worth of data
instead of the sixteen in a real IBL half
-
stave. The DBM modules will be powered with standard IBL low
-
voltage (LV)
and high
-
voltage (HV) power supply modules controlled through the standard pixel/IBL control and monitoring system.
The o
nly DBM
-
specific piece of the readout under development is an LVDS hit
-
bus chip that will allow accumulation
of telescope track multiplicities independently of the ATLAS data acquisition system, as a monitor of backgrounds and
luminosity even when ATLAS is

not taking data.

Ten DBM modules have been assembled and tested. Work is on going with IZM to finalise the metallisation and bump
-
bonding procedures. The performance of four modules have been studied in test beams a
t CERN and DESY, with the
scope

of learn
ing on how to calibrate the charge gain for the FE
-
I4 chip and set the single
-
channel thresholds to
optimise the hit efficiencies for our diamond devices. Over the la
st year, the Collaboration has
been actively working
with a second diamond sensor supplier

to complement the erstwhile single source of diamond sensor material. Four
sensors have been received from this new company that show comparable, or better, signal sizes and an order for ten
additional DBM sensors has been placed with this new vendor. Ten

additional sensors are expected in July 2012.
Finally, extensive thermal and mechanical modelling of the support structure design have been performed to ensure that
the DBM will be thermally neutral in ATLAS
. The process of manufacturing the mechanical pa
rts has started in order
to deliver it at CERN by the end of 2012
.
Table
5

p
rovides

details of the remaining DBM construction and installation
milestones. More details can be found in
[5]
.



DBM Milestones


Date

Test

beam results from Module 0

June 1, 2012

Sensors 1
-
20 at IZM for module production

July 1, 2012

Modules 1
-
15 ready for Q/A

September 1, 2012

Sensors 21
-
40 at IZM for module production

November 1, 2012

Support Mechanics ready at CERN

December 1, 2012

Modules 16
-
32 ready for Q/A

January 1, 2013

DBM telescopes 1
-
5 ready for mounting

May 1, 2013

DBM telescopes 6
-
9 ready for mounting

June 15, 2013

Mount DBM telescopes in nSQP

July 1, 2013

Table
5
:

Milestones for DBM construction, assembly, testing and installation in ATLAS nSQP.



Acknowledgements

The IBL Technical Design Report Addendum has been prepared by an editorial team consisting of
G. Darbo, D. Ferrere,
C. Gemme

and

W. Trischuk
.

We offer our sincere appreciation to
P. Allport,
B. Di
Girolamo, C. Gößling, M. Nessi, and
H. Pernegger
for
careful
revi
ew and constructive suggestions.

We acknowledge the support of IBL institutes and funding agencies.




References

[1]

ATLA
S Collaboration,
ATLAS Insertable B
-
Layer Technical Design Report
,
ATLAS TDR 19, CERN/LHCC
2010
-
013
, 15 September 2010.

[2]

IBL Collaboration,
Prototype ATLAS IBL Modules using the FE
-
I4A Front
-
End Readout Chip
, to be
published on JINST.

[3]

R. Klingenberg, D. Mue
nstermann and

T. Wittig
,
Sensor Specifications and Acceptance Criteria for Planar
Pixel Sensors of the IBL at ATLAS
,
ATL
-
IP
-
QA
-
0030
,
https://edms.cern.ch/document/1212891/1


[4]


C. Da i , M. Boscardin
, G. Pellegrini, G
-
F. Dalla Betta,
Technical Specifications and Acceptance Criteria
for the 3D Sensors of the ATLAS IBL
,
ATU
-
SYS
-
QC
-
0004
,
https://edms.cern.ch/document/1162203/
1

[5]

H.

Kagan, M
.
Mikuž

and

W
.

Trischuk
, ATLAS Diamond Beam Monitor (DBM), A
TL
-
IP
-
ES
-
0187
,
https://edms.cern.ch/document/1211792/1
.

[6]

Share Point Site of the
ATLAS Pixel Service Quarter Panel Reproduction
,
https://espace.cern.ch/atl
-
pix
-
sqp
-
ero/Pages/Default.aspx

[7]

ATLAS Collaboration,
Addendum No. 01 to the Memorandum of Understanding for Collaboration in the
Construction of the ATLAS Detector
:


Construction o
f the ATLAS Insertable B
-
Layer (IBL) Sub
-
Detector
”,
CERN
-
RRB
-
2012
-
028
-
Appendix 1
.


[8]

Didier Ferrere, Maurice Garcia
-
Sciveres
,
Claudia Gemme,

Fabian Huegging,

Daniel Muenstermann, Ole
Rohne and

Ettore Ruscino, Module Flex design FEI4B
,
ATU
-
SYS
-
EP
-
0006
,
https://edms.cern.ch/file/1183059/1/ATU
-
SYS
-
EP
-
0006_V1.pdf
.

EDMS Document page:
https://edms.cern.ch/nav/1349898803/1225588775%26expand_open=Y
.