25 oct 2011 the silicon vertex detector of the belle ii experiment ieee nss 2011 thomas bergauer...

25 Oct 2011

The Silicon Vertex Detector of the Belle II Experiment

IEEE NSS 2011

Thomas Bergauer (HEPHY Vienna)

Valencia


2T. Bergauer (HEPHY Vienna)25 Oct 2011

Belle and Belle II SVD Double Sided SensorsReadout SystemChip-on-Sensor-ConceptSummary



Linac

Belle

KEKB

KEKB and Belle @ KEK (1999-2010)• Asymmetric machine:

8 GeV e- on 3.5 GeV e+

• Center of mass energy: Y(4S) (10.58 GeV)• High intensity beams (1.6 A & 1.3 A)• Integrated luminosity of 1 ab-1 recorded in total• Belle mentioned explicitly in Physics Nobel Prize

announcement to Kobayashi and Maskawa

~1 km in diameter

KEKBBelle

Linac

About 60km northeast of Tokyo



SuperKEKB and Belle II (2010–2014)

• Aim: super-high luminosity ~81035 cm-2s-1 11010 BB / year– Refurbishment of accelerator

and detector required

• Schedule:– LoI published in 2004– TDR was written in 2010

– Construction 2010-2014– Commissioning 2014-2015– Operation 2015 onwards

http://belle2.kek.jp



Belle Silicon Vertex Detector (SVD)

• Present SVD limitations are– occupancy (currently ~10% in

innermost layer) need faster shaping

– dead time (currently ~3%) need faster readout and pipeline

• Belle II needs detector with– high background tolerance– pipelined readout– robust tracking– low material budget in active

volumeCurrent SVD is not suitable for Belle II

10%

L1

L2 L3 L4



Previous SVD Layout (until 2010)

• 4 straight layers of 4" double-sided silicon detectors (DSSDs)• Outer radius of r~8.8 cm

• Up to three 4” sensors are daisy- chained and read out by one hybrid located outside of acceptance region

0

0

10

12

34

[cm]

layers

[cm]

20

-10-20-30 10 20 30 40



0

0

10

1+23

45

6[cm] layers

[cm]

20

-10-20-30 10 20 30 40

New Layout for Belle II SVD (2014-)

• New double-layer pixel detector using DEPFET technology

• Strip layers extend to r~14 cm– 6” sensors

• Every sensor is read out individually (no daisy-chaining) to maintain good S/N chip-on-sensor concept

Double-layer of DEPFET pixels

4 layers of double-sided strip sensors



Belle and Belle II SVDDouble Sided SensorsReadout SystemChip-on-Sensor-ConceptSummary


925 Oct 2011

Vendors of 6” DSSD

• Double sided strip silicon detectors with AC-coupled readout and poly-silicon resistor biasing from 6 inch wafers

• 6” prototypes ordered and delivered from – Hamamatsu (rectangular)– Micron (trapezoidal)

T. Bergauer (HEPHY Vienna)


Rectangular Sensors from Hamamatsu

• HPK re-started production of DSSDs on 6” wafers• Old 4” production line was

decommissioned

• We evaluated first three batches so far• Quality is constantly improving

• Technical details (layers 4,5,6):• Dimensions: 59.6 x 124.88 mm2

• p-side: 768 strips, pitch: 75 µm• n-side: 512 strips, pitch: 240 µm

25 Oct 2011 10T. Bergauer (HEPHY Vienna)



Trapezoidal Sensors from Micron

• Trapezoidal sensor for forward region

• Different p-stop layouts on test sensors

Atoll p-stop

Common p-stop

Combined p-stop


12T. Bergauer (HEPHY Vienna)

Modules for Beam Test

• Read out by APV25 (CMS)• Baby Module used to verify p-stop

geometries

25 Oct 2011

Baby Module

Trapezoidal Module



Signal-to-noise-ratios

• Dark colors: non-irradiated, Light colors: irradiated• Atoll pattern (half-wide) performs best, both irradiated and non-

irradiated • Charge accumulation in non-implanted regions after irradiation

narrow half-narrow half-wide wide

10

15

20

25

30

35

40

Atoll p-stop

Geometry

SN

R


10

15

20

25

30

35

40

Common p-stop

Geometry

SN

R


10

15

20

25

30

35

40

Combined p-stop

Geometry

SN

R

• Test sensors have been Gamma-irradiated with Co-60 (70 Mrad)• Tested before and after at CERN beam test (120 GeV hadrons)



Readout System Concept• Prototype readout system exists• Verified in several beam tests• Scheme shown below

1902APV25chips

Front-end hybrids Rad-hardvoltage

regulators

Analog level translation, data sparsification andhit time reconstruction

Unified Belle IIDAQ system

~2mcoppercable

J unctionbox

~10mcoppercable

FADC+PROC

CO

PP

ER

Unified opticaldata link (>20m)

Finesse Transmitter Board (FTB)



Readout Chip: APV25

• Developed for CMS (LHC) by Imperial College

London and Rutherford Appleton Lab – 70.000 chips installed

• 0.25 µm CMOS process (>100 MRad tolerant)

• 128 channels

• 192 cell analog pipeline

no dead time

• 50 ns shaping time low occupancy

• Noise: 250 e + 36 e/pF

must minimize capacitive load!!!

• Multi-peak mode (read out several

samples along shaping curve)

• Thinning to 100µm successful

25 Oct 2011



Prototypes

Repeater BoxLevel translation, buffering

FADC+PROC (9U VME)Digitization, zero-suppression,

hit time reconstruction



APV25 – Hit Time Reconstruction

• Possibility of recording multiple samples (x) along shaped waveform (feature of APV25)

• Reconstruction of peak time (and amplitude)by waveform fit– Offline now– Hardware later

• Is used toremove off-timebackground hits

0 50 100 150 200 250 300

0

5000

10000

15000

20000

25000

30000

S peak

tpeak

Measurement


19

Occupancy Reduction

Threshold

Threshold

Tim e over threshold ~ 2000ns (m easured)

Tim e over threshold ~ 160ns (measured)

Sensitive tim e window ~ 20ns

VA1TATp~800ns

APV25Tp~50ns

Pulse shapeprocessingRM S(tm ax)~3ns

Gain ~12.5

Gain ~8

Total gain ~100

25 Oct 2011 T. Bergauer (HEPHY Vienna)


2125 Oct 2011

Chip-on-Sensor Concept• Chip-on-sensor concept for double-sided readout• Flex fan-out pieces wrapped to opposite side (hence “Origami“)• All chips aligned on one side single cooling pipe

Side View (below)


APV25 chips(thinned to 100µm)

3-layer kapton hybrid

fanout for n-side (z)DSSD

double-layer flex wrapped to p-side (r-phi)

cooling pipeCF sandwich ribs

APV25(thinned to 100µm)

support ribs

cooling pipe

SensorAirex

Kaptonwrappedflex fanout


2225 Oct 2011

Origami Module with 6” HPK DSSD




Origami Module Assembly

Ingredients:

• DSSD sensors

• Kapton PCB and pitch-adapters

• APV Readout chips

Followed by complicated assembly

procedure

• currently verified by all groups

interested in ladder assembly

25 Oct 2011


2425 Oct 2011

Sketch of the Outermost Ladder (Layer 6)

• Composed of 5 x 6” double-sided sensors• Center sensors have Origami structure• Averaged material budget over the full module: 0.55% X0

ca. 60cm



2525 Oct 2011

Ladder Mechanics

• Carried by ribs made of carbon fiber and Airex foam

• Very stiff, yet lightweight thanks to the sandwich construction

Cooling Pipe Sensor

Support Ribs




CO2 Cooling

• Closed CO2 cooling plant under development

• Collaboration with CERN• First step is to gain experience

with open (blow) system

25 Oct 2011

Control cabinet with touch screen Accumulator

Liquid pumps

1.3 m

1.6

m1.

2 m



Summary• KEKB is the highest luminosity machine in the world

• Upgrade of KEKB and Belle (2010-2014)– 40-fold increase in luminosity– Needs upgrades of all sub-detectors

• New, enlarged Silicon Vertex Detector– DEPFET pixel double-layer– Four double-sided strip layers

• Strip Detector R&D– 6 inch Double Sided Strip Detectors by HPK and Micron

• Optimal p-stop geometry identified by SNR measurements before and after irradiation

– Readout with hit time reconstruction for improved background tolerance– Origami chip-on-sensor concept for low-mass DSSD readout


29

Backup Slides follow


The End.

Beam Parameters

KEKB Design

KEKB Achieved: with crab

SuperKEKBHigh-Current

SuperKEKB Nano-Beam

Energy (GeV) (LER/HER) 3.5/8.0 3.5/8.0 3.5/8.0 4.0/7.0

by* (mm) 10/10 5.9/5.9 3/6 0.27/0.42

ex (nm) 18/18 18/24 24/18 3.2/2.4

sy(mm) 1.9 0.94 0.85/0.73 0.059

xy 0.052 0.129/0.090 0.3/0.51 0.09/0.09

sz (mm) 4 ~ 6 5/3 6/5

Ibeam (A) 2.6/1.1 1.64/1.19 9.4/4.1 3.6/2.6

Nbunches 5000 1584 5000 2503

Luminosity (1034 cm-2 s-1) 1 2.11 53 80

25 Oct 2011



KEKB accelerator upgrade

25 Oct 2011

Crab cavity

3.5GeV e+

8GeV e-

New beam-pipeswith ante-chamber

Dampingring for e+

New IR with crabcrossing and

smaller by*

More RF for higherbeam current

SRbeam


32

New dead-time-free pipelined readout and

high speed computing systems

Faster calorimeter with waveform sampling and pure CsI (endcap)

New particle identifier with precise Cherenkov device:

(i)TOP or fDIRC.Endcap: Aerogel RICH

Si vertex detector withhigh background tolerance

(+2 layers, pixels)

Background tolerant super small celltracking detector

KL/m detectionwith scintillator

and next generationphoton sensors

Belle-II




Sensor Types and Vendors

Rect (122.8 x 38.4 mm , 160 / 50 um pitch)2

Rect (122.8 x 57.6 mm , 240 / 75 um pitch)2

W e dge (122.8 x 57 .6-3 8.4 m m , 240 / 75..50 um p itch)2

0

0

10

3

45

6[cm] layers

[cm]

20

-10-20-30 10 20 30 40

6

z APVs

z APVs

z APVs

64

4

4 4

46

6

6

rphi APVs

rphi APVs

rphi APVs

6

64

4

4 4

4

4

46

666 6

6 6 6

6

Layer # of Ladders

Rect. Sensors[narrow]

Rect. Sensors[wide]

Wedge Sensors

APVs

6 17 0 68 17 850

5 14 0 42 14 560

4 10 0 20 10 300

3 8 16 0 0 192

Sum: 49 16 130 41 1902



Micron Wafer Layout

Teststructuresfor p-side

Teststructuresfor n-side(no GCD)

Baby sensor 1p-side: 512 strips 50 µm pitch 1 interm. stripn-side: 512 strips 100 µm pitch 1 interm. strip atoll p-stop

3 different GCDsfor the n-side

Main sensorp-side: 768 strips 75-50 µm pitch 1 interm. stripn-side: 512 strips 240 µm pitch 1 interm. strip combined p-stop

Quadratic baby sensors 2,3,4p-side: 512 strips 50 µm pitch 1 interm. stripn-side: 256 strips 100 µm pitch 0 interm. strip different p-stop patterns

1) atoll p-stopvarying distance from strip

2) conventional p-stopvarying width

3) combined p-stopvarying distance from strip

1)

2)

3)

25 Oct 2011


narrowhalf-

narrowhalf-wide wide

Common

Combined

Atoll35T. Bergauer (HEPHY Vienna)25 Oct 2011

p-stop layouts of the test sensors

• Three different p-stop patterns• Per pattern, four zones with different geometry• Green: strip implant (n), Red: p-stop



eta distribution for atoll p-stop

Charge accumulation in unimplanted region


37

Current Barrel Layout

Slanted Sensors

Origami

Cooling Tubes

Hybrid Boards

Layer Sensors/Ladder

Origamis/Ladder Ladders Length [mm] Radius [mm] Slant Angle [°]

3 2 0 7/8 262 38 0

4 3 1 10 390 80 11.9

5 4 2 14 515 115 17.2

6 5 3 17 645 140 21.1



38

Comparison VA1TA – APV25

VA1TA (SVD)• Commercial product (IDEAS)

• Tp = 800ns (300 ns – 1000 ns)• no pipeline• <10 MHz readout• 20 Mrad radiation tolerance• noise: ENC = 180 e + 7.5 e/pF• time over threshold: ~2000 ns• single sample per trigger

APV25 (Belle-II SVD)• Developed for CMS by IC

London and RAL• Tp = 50 ns (30 ns – 200 ns)• 192 cells analog pipeline• 40 MHz readout• >100 Mrad radiation tolerance• noise: ENC = 250 e + 36 e/pF• time over threshold: ~160 ns• multiple samples per trigger

possible (Multi-Peak-Mode)




Measured Hit Time Precision

• Results achieved in beam tests with several different types of Belle DSSD prototype modules (covering a broad range of SNR)

• 2...3 ns RMSaccuracy at typical cluster SNR(15...25)

• Working onimplementationin FPGA (using lookup tables) – simulationsuccessful

Time Resolution vs. Cluster SNR

0

1

2

3

4

5

6

7

5 10 15 20 25 30

Cluster SNR [1]

trm

s [n

s]

Previous beam tests

SPS 09 beam test

Log-Log Fit

(TDC error subtracted)

Origami Module


40

Maximum Radiation Length Distribution

Kapton

0 10 20 30 40 50 600

0.5

1

1.5

2

2.5

3

3.5

Profile [mm]

Radi

atio

nLe

ngth

[%]

Rib Design

CFRP Rohacell

Pipe APVCoolant

Sensor



Cooling Boundary Conditions

• Power dissipation per APV: 0.35 W• 1 Origami sensor features 10 APVs

• Total Origami power dissipation: 312 W• 354 W dissipated at the hybrid boards • Total SVD power dissipation: 666 W

Origamis/Ladder

Ladders APVs Origami

APVs Hybrid

Layer 6 3 17 510 340

Layer 5 2 14 280 280

Layer 4 1 10 100 200

Layer 3 0 8 0 192

25 Oct 2011 41T. Bergauer (HEPHY Vienna)

25 oct 2011 the silicon vertex detector of the belle ii experiment ieee nss 2011 thomas bergauer...

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