STAR Heavy Flavor Tracker Upgrade --Status of PXL Detector

X,Sun

1

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

STAR Heavy Flavor Tracker Upgrade
--
Status of
PXL
Detector

Xiangming

Sun(
孙向明
)

Lawrence Berkeley National Lab

L. Greiner,

H.
Matis

T.
Stezelberger

M.
Szelezniak

C. Vu

H.
Wieman

… …


X,Sun

2

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Outline

•
Heavy Flavor Tracker
upgrade
in STAR
at RHIC

•
Fast Simulation of Detector Performance

•
Monolithic Active Pixel Sensor

•
PXL Readout Electronics

•
Power Consumption and Cooling test

•
Summary



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3

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

STAR Detector at RHIC

RHIC (Relativistic heavy ion
collider)

Brookhaven National Lab

http://www.bnl.gov/rhic/



STAR(the
solenoidal

tracker at RHIC )
is one of Detector at RHIC.

It specializes in tracking the thousands
of particles produced by each ion
collision

X,Sun

4

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Physics Goals

heavy ion collision generate a very hot and
dense medium


Charm particle is proposed to probe medium
property

Direct Topological reconstruction of Charm

Detect charm decays with small c

Ⱐ
楮捬畤楮朠⁄
0



䬠


(122.9 m
m
)

Method: Resolve displaced vertices
(100
-
150
microns)

X,Sun

5

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Inner Detector Upgrades

TPC
–

Time Projection Chamber

(main tracking detector in STAR)


HFT
–

Heavy Flavor Tracker


SSD
–

Silicon Strip Detector


r = 22 cm


IST
–

Inner Silicon Tracker


r = 14 cm


PXL
–

Pixel Detector


r = 2.5, 8 cm

We track inward from the TPC with graded resolution:

TPC

SSD

IST

PXL

~1mm

~300µm

~250µm

vertex

<30µm

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6

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

PXL Detector

Ladder with 10
MAPS sensors
(~ 2
×
2 cm each)

M
A
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a
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t
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a
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e
s
2
layers: 2.5,8 cm

10
sectors

1+3
ladders
/ sector

Mechanical support with
kinematic mounts

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7

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Some PXL Parameters

Layers

Layer 1 at 2.5 cm radius

Layer 2 at 8 cm radius

Pixel patch size

18.4
m
m X
18.4
m
m

Hit resolution

10
m
m
rms

Position stability

6
m
m
rms

(20
m
m envelope)

Radiation thickness per
layer

X/X0 = 0.37%

Integration time
(affects pileup)

200
m
s

Number of pixels

0.2 ms
436 M

Radiation tolerance

300
kRad

Rapid detector
replacement

< 8 Hours

critical

and

difficult

more than a factor of 2 better than other vertex detectors
(ATLAS, ALICE and PHENIX)

X,Sun

8

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Fast Simulation of Detector Performance

detector layer 1

detector layer 2

r
2

r
1

true vertex

perceived


vertex




x


x


v

Position resolution:


1, Effective pixel Size :


2, Multiple Coulomb Scattering

Line assumption:


using line created by two points in
two layers to calculate dispersion
from true vertex.


Consistent with full
Geant

simulation


Free parameters :


Pixel resolution


Detector thickness

X,Sun

9

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Position Resolution
vs

Significance

Significance=

signal

(
signal+background
)

1/2

______________

Effective pixel size=21.5um

It includes:


pixel patch size 18.4um


thermal distortion 4.5um


cooling vibration 10um

D0 momentum=1GeV/c

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10

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Detector Thickness
vs

Significance

X/X0=0.58%

It includes:


first layer thickness
0.37%


beam pipe thickness
0.21%

(Beryllium)



D0 momentum=1GeV/c

X,Sun

11

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Association
Rate
vs

Pointing Resolution and Hit Density

Nhits

per sensor=250 for 200us integration time

Pointing resolution=250um

Association
rate=
80
%

Association rate: associating hits to tracks from outer detector

X,Sun

12

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Monolithic Active Pixel Sensors

•
IPHC
-
DRS (former IRES/LEPSI) proposed using MAPS for high energy physics in
1999

•
Standard
commercial CMOS technology

•
Sensor
and signal processing are integrated in the same
silicon
wafer

•
Proven thinning to
50
micron

•
Signal is created in the low
-
doped epitaxial layer (typically ~
10
-
15
μm
) → MIP

•
signal is limited to <
1000
electrons

•
Charge
collection is mainly through thermal diffusion (~
100
ns), reflective
boundaries at
p
-
epi

and
substrate → cluster size is about ~
10
pixels (
20
-
30
μm

pitch)
‏

•
Room temperature operation





MAPS pixel cross
-
section (not to scale)
‏

X,Sun

13

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

From Analog to Binary Readout

V
R
E
F
1
P
W
R
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N
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O
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2
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1
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2
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E
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T

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P
A
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A
T
O
R

(
C
O
L
U
M
N

L
E
V
E
L

C
D
S
)
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O
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F
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l
a
t
c
h
Q
Q
_
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E
A
D
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E
A
D
+
+
+
+
+
+
-
-
-
-
L
A
T
C
H
C
A
L
I
B
R
E
A
D
Digital readout
–

offers increased speed but requires on
-
chip discriminators
or ADCs and increased S/N for on
-
chip signal processing

Analog readout
–

simpler architecture
but slower readout

X,Sun

14

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

MAPS Integration Time = Readout Time

•
Typical sensor readout

–
“rolling shutter” mode.

–
Integration
time = array readout
time

•
Column parallel readout architecture

–
All columns readout in parallel and
then multiplexed to one output

–
Integration
time = column readout
time

–
Integration time =

200
us


X,Sun

15

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

PXL Readout Electronics

2 m (42 AWG TP)

6
m (
24
AWG TP)


100 m (fiber optic)



4 ladders per sector



1 Mass Termination Board (MTB) per sector



1 sector per RDO board



10 RDO boards in the
PXL
system

RDO motherboard + Xilinx Virtex
-
5 Dev Board

RDO PC with DDL link to RDO board

Mass termination board + latch up
protected power daughtercard

← Front Back ↓

X,Sun

16

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

RDO System Design
–

Physical Layout

1
-
2 m

Low mass twisted pair

6
m
-

twisted pair

Sensors / Ladders / Sectors

(interaction point)

LU Protected Regulators,

Mass cable termination

RDO Boards

DAQ PCs

(Low
Rad

Area)

DAQ Room

Power

Supplies

Platform

30 m

100 m
-

Fiber optic

30
m USB

Control


PCs

30
m

400MB/s

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17

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Firmware Structure

17

DDL/USB

PC

sensor

Xilinx Virtex
-
5 Dev Board

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18

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

I
O

D
elay for
D
igital
D
ata
A
lignment

800 channels, 160 MHz digital
signals pass
8 meters
and 3 buffering stages before
arriving FPGA
.


digital need to be aligned in FPGA end.


Solution: FPGA
iodelay

function

Status

•

Data Path Architecture Validated

•

Measured BER (bit error rate) of < 10
-
14

X,Sun

19

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

System Control

C
ommand
generator:


command.exe

Hex file

usb.exe

download_data_block_to_F
EE

0x0402fffd

0x1d82ff3f

0x1502ffcf

0x2642ffff

0x2642fdff

0x2202feff

0x0c03fff0

0x1547ffff

0x1547ffff

0x1547ffff

0x1547ffdf

0x0cc7ffff

0x0cc7ffff

………….

DAQ

PC

rorc_receive

getda
ta

Control

PC

X,Sun

20

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Power Consumption and Cooling Test Setup



•
Sensor: 170
mW
/cm
2


→ 270 W for PXL sensors

•
2 W/drivers/cable

→ 80 W for PXL drivers

Silicon heater put on ladder

X,Sun

21

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Cooling
Tests
at ~360 W
–

IR
Images

Air 13.8 m/s

Hot spots ~37
°
C

Air 10.1 m/s

Hot spots ~41
°
C

Air
4.7
m/s

Hot spots ~
48
°
C

Air temperature ~27
°
C

From infra
-
red camera

X,Sun

22

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

0
2
4
6
8
10
12
14
16
18
0
5
10
15
20
25
30
location on ladder (cm)
vibraitons RMS (um)
~4.7 m/s
~9.3 m/s
~12.8 m/s
~4.7 m/s (fixed end)
~9.3 m/s (fixed end)
~12.8 m/s (fixed end)
Vibrations
Caused
by
Airflow

Beginning of the driver
section

(Supported end)

End of sensor
section

(Unsupported end)

Using capacitance sensor to measure
vibration


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23

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Ionizing Radiation Tolerance

MIMOSA
-
22 Testing in 10
KeV

X
-
Rays in Lab

MIMOSA
-
22ter

Signal/noise ratio >=20 after 300
kRad

Ionizing radiation (300
e+e
-

pairs)

Non
-
ionizing radiation is under investigation


X,Sun

24

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

•
We have a well advanced mechanical design that is in the
process of being verified by simulation and prototyping.

•
The prototype RDO system is performing well.

•
Sensor development with IPHC is on schedule and we
expect the first prototype final sensor delivery in
2011
.

•
The ladder cable development is on schedule and we are
evaluating the ITB performance with the full compliment of
10
working sensors.

Summary

Our current status:

The PXL is expected to be


fully installed in 2013 for RHIC Run14

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25

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

X,Sun

26

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

X,Sun

27

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

X,Sun

28

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

Summary

Effective pixel size 21.5 um

Layer thickness X/X0=0.37%

Air speed 10.1m/s

Sensor max temperature 41

°
C

Vibration xx um(included in
Effective pixel size
)

The integration time 200 us

Hit density during
integration 250

Association rate 80%

Readout Electronics


match the requirement


Our current status:

The PXL is expected to be


fully installed in 2013 for RHIC Run14

Please give status

X,Sun

29

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

X,Sun

30

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

PXL Detector

Ladder with 10
MAPS sensors
(~ 2
×
2 cm each)

M
A
P
S
R
D
O
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/
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t
r
a
c
e
s
Mechanical support with kinematic
mounts

Cabling and cooling
infrastructure

New beryllium beam pipe
(
800
µ
m thick, r =
2.5
cm)


2 layers

10
sectors

3+1
ladders
/ sector

X,Sun

31

STAR Regional Meeting, Oct 23, 2010, SDU

STAR


Direct measurement has not been done so far.


Based on estimates (http://rnc.lbl.gov/~wieman/radiation dose
straus

oct

2007 HW.ppt) and TLD projection.


•
For the radius of 2.5 cm:

–
Ionizing radiation:

•
Total dose: 155
kRad

•
TLD projection: 300
kRad


–
Non
-
ionizing radiation

•
average
pion

count for 1 Yr: 3x1012 cm
-
2

•
TLD projection (
pion

assumption): 12x1012 cm
-
2



Radiation Environment

X,Sun

32

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

Ionizing Radiation Tolerance

MIMOSA
-
22 Testing in 10
KeV

X
-
Rays in Lab

MIMOSA
-
22ter

Signal/noise ratio >=20 after 300
kRad

Ionizing radiation (300
e+e
-

pairs)

Non
-
ionizing radiation is under investigation


X,Sun

33

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

•
The Heavy Flavor Tracker (HFT) is an upgrade project for the STAR
detector at RHIC, It will allow the topological reconstructions of the heavy
flavor hadrons via their
hadronic

decays . The HFT consists of three coaxial
detectors: SSD(Silicon Strip Detector), IST(Intermediate Si
-
Tracker)
and


PXL(a pixel detector). The PXL is the inner
-
most and highest precision
detector in HFT. The sensor chip we use to build PXL is developed in
Monolithic Active Pixel Sensor(MAPS) technology. Each sensor has
1024X1188 pixels with 18.4 micron pitch and 50 micron thickness. The
integration time is 200 us. Correlated double sampling (CDS) and
digitization are performed on the sensor chip. The readout electronics is
designed to handle 400 sensors which are grouped in 10 sectors. In this
talk, we discuss the relation between the physics goals and sensor
characteristics, such as pixel size, sensor thickness, integration time,
radiation tolerance and power consumption. We introduce the on
-
chip
electronics design to perform CDS and digitization. We also show the
readout electronics designed to handle R&D tests and physics data
acquisition. The PXL is expected to be


fully installed in 2014 for RHIC
Run14

X,Sun

34

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

Initial testing with ~75
μ
m
travel past touchdown

30
μ
m additional
lowering of probe pins

Phase
-
1 discriminator transfer
functions ƒ(threshold voltage)
observed on two of the probed
sensors :


Sensors designed with dedicated probe pads in the sensor pad ring.


13 full
-
thickness, diced sensors probe tested.


Up to 3 probe tests on a sensor.


We will begin testing thinned sensors within the next few days

Status

•
Automated and scripted system
for sensor testing is in place.

•
Vacuum chuck for handling up to
twenty 50
μm

thick sensors is
being tested

•
Ongoing sensor testing

Probe Tests

X,Sun

35

STAR Regional Meeting, Oct
23
,
2010
, SDU

STAR

Cooling tests at ~360 W

•
Initially: 100 mW/cm
2


→ 160 W for PXL sensors

•
Updated: x1.7


→ 270 W for PXL sensor

•
2 W/drivers/cable


→ 80 W for PXL drivers

Ladder
section

Measured
resistance


(Ω)

Current

(A)

Voltge

(V)

Power
(I∙V)

(W)

sensors

Sector 1

(Pt heaters)

6.6

2.06

6.97 + 7.96

30.7

Sectors 2
-
10

4.6 || 3.7

10.6

23.1

244.8

drivers

Sectors 1
-
5

1.4

5.3

8.23

43.6

Sectors 6
-
10

1.4

5.3

8.03

42.5

Total
Power

~361

X,Sun

36

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

MAPS @ Institut Pluridisciplinaire Hubert Curien

•
IPHC
-
DRS (former IRES/LEPSI) proposed using MAPS for high energy
physics in 1999


•
CMOS & ILC group today

–
6
physists

–
9 microcircuit designers

–
6 test engineers

–
7 PhD students






CNRS
-

IPHC, Strasbourg
-
Cronenbourg



More than 30 prototypes developed

–
several pixel sizes and architectures (simple
3
-
transistor cells, pixels with in
-
pixel amplifiers
and CDS processing)

–
different readout strategies (sensors operated
in current and voltage mode, analog and
digital output)

–
Large variety of prototype sizes (from several
hundreds of pixels up to 1M pixel prototype
with full
-
reticule size)


MIMOSA (Minimum Ionizing particle MOS Active sensor)

X,Sun

37

STAR Regional Meeting, Oct 23, 2010, SDU

STAR

PXL Hardware Architecture

8
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RDO motherboard

Mass Termination Board

Ladder