DEPFET detectors for future colliders. Activities at IFIC, Valencia Terceras Jornadas sobre la...

C. Mariñas, IFIC, CSIC-UVEG

DEPFET detectors for future colliders. Activities at IFIC,

ValenciaTerceras Jornadas sobre la Participación Española en los Futuros

Aceleradores Lineales de Partículas

Universitat de Barcelona

Carlos Mariñas, IFIC, CSIC-UVEG


Outlook

DEPFET: Basics

• General requirements for future colliders• DEPFET: Fundamentals

DEPFET activities at IFIC

• Characterization:• Matrices: PXD4/PXD5/PXD6 production• Single Pixel

• Test Beam• Data analysis

• ILC simulation (see M. Vos talk)• Thermal studies ILC/SuperBelle

• DEPFET thermal mock-up• Simulation

Conclusions

• Pixel detectors for future colliders• IFIC in the DEPFET Collaboration

Vertexing in future collidersC. Mariñas, IFIC, CSIC-UVEG

This requirements impose unprecedented constraints on the detector:• High granularity• Fast read-out• Low material budget• Low power consumption

Vertexing in future colliders requires excellent vertex reconstruction and efficient heavy quark flavour tagging using low momentum tracks

DEPFET Measurements made on realistic DEPFET prototypes have demonstrated that the concept is one of the principal candidates to meet these challenging requirements


DEPFET principle

Each pixel is a p-channel FET on a completely depleted bulk

A deep n-implant creates a potential minimum for electrons under the gate (internal gate)

Signal electrons accumulate in the internal gate and modulate the transistor current (400pA/e-)

Accumulated charge can be removed by a clear contact

Fully depleted• Large signal• Fast signal collection

Low capacitance, internal amplification• Low noise

Transistor ON only during readout• Low power

Complete clear• No reset noise Fe

ature

s


Introducing the Valencia’s set up

Faraday cage PC for data acquisition Stack of power supplies Laser Motorstages XYZ Complete system for air and

liquid cooling◦ Cooling blocks◦ Aluminium coils

Pulse generator


Matrix characterization

Full electrical optimization of matrices: This implies scans over a wide range of the operating voltages to achieve the best signal-to-noise ratio.

• Clear High/Low• Gate ON/OFF• Back• Bulk• Cleargate• Source

Calibration of the system using radioactive sources• Gain of the system• ENC

Laser scans: Charge collection uniformity


Already tested at IFIC

CLGClocked CleargateNHE38x30μm2

CCGCommon CleargateLE32x24μm2

C3GCapacitive Coupled Cleargate24x24μm2

ILC design


DEPFET Single-pixel (under construction)

D1

D2

S

G1

G2Cl

Cl

Clg

Blk

Clg

Inner structure Set-up

Better understanding of new structures• Different geometries (L-

gate)• Implants

Direct access to the system’s parameters• Complete clear• Charge collection• Noise


Test Beam


Test Beam: Our role

Full electrical characterization of one DUTParticipate in the assembly and allignment of the

telescopeParallel set-up in control roomAnalysis of dataTest Beam Coordinators 2008 and 2009 (M.Vos)

BEAM120 GeV ∏

x

y

z


Test Beam: Measurements

Voltage scans: Cross-check optimal settings◦ VBias to the wafer 150-220V

◦ VEdge

◦ VClearHigh

Angular scan: Resolution vs. Cluster size◦ -5, -4, -3, -2, -1.5, -1, -0.5, 0, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 9, 12,

18, 36

Beam energy scan: Separation “multi-scattering-intrinsic resolution”◦ 20, 40, 60, 80, 120 GeV

Large statistics◦ Charge collection uniformity◦ 3 Mevents in nominal conditions

3.5 TB of data20 Million events


0 20 40 60 80 100 120 1400

2

4

6

8

10

12

T.B. Data analysis

d0 (32x24)

d1 (32x24) d2 (24x24) d3* (32x24)

d4 (32x24) d5 (32x24)

Sig3x3(ADU) 1339 1497 1704 1757 1508 1654

Noise (ADU) 12,7 13,4 12,7 13,4 12,8 13,2

SNR 105 112 134 131 118 125

SeedSignal(ADU)

69% 56% 59% 61% 63% 64%

ENC (e-) 345 326 286 277 309 290

gq (pA/e-) 283 316 360 372 319 350

Preliminary

Seed signa

l

Preliminary

Preliminary

Resi

du

al (s

MSÅ

s TelÅ

s Int,

mm

)Beam Energy (GeV)

Distance (mm)

En

trie

s

stotal=2,5mm


Thermal studies: Simulation and measurements

First DEPFET thermal mock-up

Thermal simulation


Thermal measurements Influence of conduction

T of cooling blocks Bump bonding

Influence of convection Air speed Air temperature

Study of new materials

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.2520

25

30

35

40

45

50

55

60

65

70 Conduction

Liquid 5ºCLiquid 10ºCLiquid 15ºCLiquid 20ºCLiquid 25ºC

Power (W)

Tem

pera

ture

(ºC

)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 727

28

29

30

31

32

33

34

35

36Convection

Chip's T. Liquid at 15ºC and Air at 22ºC

Chip's T. NO liquid. Air at 23.5ºC

Air speed (m/s)

Tem

pera

ture

(ºC

)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.5

1

1.5

2

2.5

3

3.5

4

4.5

f(x) = 0.233598089035393 x + 0.0810714543456788

f(x) = 4.24932494364119 x + 0.492739776470649f(x) = NaN x + NaN

Cu. 500 microns.

Linear (Cu. 500 microns.)

TPG: k a a-1=4,3 W·mm2/K

Cu: k a a-1=1,1 W·mm2/K

Al: k a a-1=0,2W·mm2/K

DT n

orm

aliz

ed (

K/m

m2)

Power (W)

New materials


Thermal simulation Model implemented in

SolidWorks for future mechanical studies

ANSYS studies calibrated with real data


A couple of movies…

Switching mechanism is introduced

Influence of air and liquid cooling studies


Conclusions

Vertexing in Future Colliders◦ Very hard conditions

Radiation (10MRad for SuperBelle) Background Reduced material budget Unprecedented granularity Power consumption and heat dissipation

◦ Improvement of the detector’s performance is needed

New generation of pixel detectors try to cope with this requirements

DEPFET: One of the most promising technologies for vertexing and tracking


Conclusions: DEPFET in Valencia

Matrix characterization◦ 2 different generations characterized◦ Full electrical optimization◦ Calibration◦ Charge collection uniformity◦ Working on Single Pixel set-up

Test Beam◦ Optimization of DUT◦ Instalation and alignment of the telescope◦ Data analysis

Thermal studies◦ DEPFET thermal mock-up◦ Study of new materials for better cooling◦ Influence of air/liquid cooling◦ Simulation


Backup slides


Mechanics

1. Support structures:

◦ FEA models of mechanical properties

Natural frequencies Rigidity Stability Deformations

◦ Validation with mock-up

2. Module:

◦ Simulations using FEA: (Finite

Element Analysis) Mechanical effects: Strenght of

module Thermal effects: Cooling

◦ Validation with prototypes


Competitors for SuperBelle

Strip detecto

rs (DSSD)

•Shorter strips•Fast readout (higher noise)•Cannot be thinned

Hybrid pixel

detectors (ATLAS type)

•Good readout speed and granularity•Too much materialPixel

detectors with

frame readout

•High granularity•Low mass (50 microns)•Slow frame readout (rolling shutter)

DEPFET

Discarded

• Material

• Granularity


Competitors for ILC

CCD•Small signal•Cryogenic operation•Radiation damage (trapping)

CMOS sensors: MAPS/CAPS•Only small chips possible•Dead material in periphery

Silicon On Insulator (3D integration)•Thick depleted sensor (large signal, fast charge collection)•Only small chips possible•Back-gate effect (depletion voltage couples to FET gate)


Double pixel structure


Gain and noise

•Ba-133 (30keV g-ray) → 310.4 ADC Units

•Cd-109 (22keV g-ray) → 209.9 ADC Units

E (keV)

ADU

22 30

310.4

209.9

FITy=a+bx

Slope=Gain

b=12.5 ADC/keV

ekeV

he

ADC

keVADC 330

106.3

1

5.12

115

3

Noise Gain Energy to

create e-h


S/N for a MIP

keVpair

eVpairs 80

1

62.322300

keVm

keVm 127285

80450

25.4)133(30

)(127

BakeV

MIPkeV

1.- ATLAS supposition: 1 MIP→22300 pairs e-h in 285μm of Si

2.- Our DEPFET has 450μm of Si

3.- The scale factor between Ba-133 30keV g and a MIP is:

)(8625.433.20)133(33.20 MIPNSBaNS

4.- The S/N of 30keV Ba-133 g ray scaled to a MIP:


Noise in current

ADCcountmVVLSB /12.016384

12

ADCcountnAuA /1.616384

1100

nA100~

1.- ADC dynamic range: 2 V – 14 bits ->

2.- trans-impedance amplifier gain = 1 V / 50 mA

3.- 15 ADC counts of noise


Introducing the device

Switchers A (Gate) and B (Clear) for CLG

A-GATE B-CLEAR

CURO


CLG vs CCG

VCleargate-Low

VCleargate-High

Amp/mV

Time/ms

VClear-High

VClear-Low

Clock

ed-

Clear

gate

VCommon-Cleargate

VClear-High

VClear-Low

Comm

on-

Clear

gate


Effect on spectrum

#E

ntr

ies

ADU

Signal peak

Incomplete

clear

Noise peak

Leackage Current

Background


Amplifiers

OUTIN

-5V

1.8V 1.3V

-3.2V

-8.2VVsubstr

39kΩ

Iin

AD8015

AD8129

5V 14V

+IN

-IN

REF

FB

>2V

2kΩ 18kΩ

6mV

R10

R10

R50

R501

50

pF

7V

-7V


10V


drainq Ig


Double pixel structure

Actual size of two pixels

Double pixel cell 33 x 47 µm2


VDRAIN

VGATE

GND

55Fe

Light

Pulsers Sequencer

Shaper ADC

PC


CDS

Correlated Double Sampling Scheme

DEPFET detectors for future colliders. Activities at IFIC, Valencia Terceras Jornadas sobre la...

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