CCD based Vertex Detector for GLC 1

CCD based Vertex Detector for GLC

Yasuhiro SugimotoKEK

KEK/Niigata/Tohoku/Toyama Collaboration

@VERTEX2003, Sep. 16, 2003

CCD based Vertex Detector for GLC 2

Contents

Project Overview of GLC Accelerator Detector

CCD Vertex Detector Merit/Demerit of CCD at GLC/TESLA

R&D Status Radiation Damage : Energy Dependence of Electron Damage

Dark Current, Flat-band Voltage Shift, Hot Pixels Charge Transfer Inefficiency

Summary

CCD based Vertex Detector for GLC 3

GLC Project

JLC has changed its name as GLC (Global Linear Collider) 500GeV – 1TeV LC based on X-band linac Future global organization is anticipated Start experiment at 2013

CCD based Vertex Detector for GLC 4

GLC Accelerator

CCD based Vertex Detector for GLC 5

GLC Acc. Parameters

500 GeV 1000 GeV

Luminosity 2.5x1033cm-2s-1 2.5x1033cm-2s-1

Rep. rate 150 Hz 100 Hz

Bunch population 0.75 x 1010 0.75 x 1010

# of bunch/train 192 192

Bunch separation 1.4 ns 1.4 ns

x/y at IP 243/3 nm 219/2.1 nm

z at IP 110 m 110 m

CCD based Vertex Detector for GLC 6

GLC Beam Structure

GLC/NLC: Readout between trains ( 1 frame/6.7ms )

TESLA: Readout during trains ( 1 frame/50s ) GLC/NLC is more favorable for vertex detectors

CCD based Vertex Detector for GLC 7

GLC Detector

CCD based Vertex Detector for GLC 8

GLC Detector

Baseline Design Possible Option

Vertex Detector CCD MT-CCD or CP-CCD

Intermediate Tracker Silicon Strip Det.

Central Tracker Jet Chamber TPC

Solenoid Field 3T 4T

Calorimeter Pb/Sci (Tile-Fiber) Digital Cal.

Beam X’ing Angle 7 mrad 20 mrad

CCD based Vertex Detector for GLC 9

CCD Vertex Detector Merits of CCD for Vertex Detectors

Very thin (~20m) sensitive region (=Epitaxial (p-type) layer) Small multiple scattering Diffusion of electrons in epitaxial layer

Key of excellent spatial resolution for CCD ( and CMOS ) Takes time to diffuse : d = sqrt(Dt) ~ 6m @ t=10ns OK for GLC/NLC (Fully depleted CCD at TESLA)

CCD has simple structure Large area sensor High yield

CCD based Vertex Detector for GLC 10

CCD Vertex Detector

Demerits of CCD for Vertex Detectors Long charge transfer path

Charge transfer inefficiency (CTI) by traps created by radiation damage

Long readout time Multi-port readout

CP-CCD

CCD based Vertex Detector for GLC 11

CCD Vertex Detector

Baseline Design of GLC Vertex Detector R=24, 36, 48, 60 mm |cos| < 0.9 = 4 m Wafer thickness = 300 m B = 3T

b = 7 + 20/(psin3/2m

This design is just a working assumption and the starting point of further R&D

CCD based Vertex Detector for GLC 12

R&D Issues

Design Criteria : “The Highest Vertex Resolution with Technical Feasibility”

High spatial resolution of the sensors Minimize multiple scattering Thin wafer Close to the IP Radiation Hardness Room temperature operation, if possible

Next milestone: b = 5 + 10/(psin3/2m

CCD based Vertex Detector for GLC 13

R&D Status

Spatial Resolution: < 3m has been demonstrated by beam tests

Thin Wafer: Partially thinned (honeycomb type) wafer is being

designed ( average thickness ~ 100 m ) Radiation Damage Study:

Neutron damage study by Cf-252 Electron damage study by Sr-90/150MeV beam

CCD based Vertex Detector for GLC 14

Electron Damage Study

Damage in CCDs Surface Damage

Due to dE/dx in SiO2

Cause surface dark current and flat-band voltage shift

Bulk Damage Due to lattice dislocatio

n in Si bulk Cause bulk dark current

and CTI

CCD based Vertex Detector for GLC 15

Electron Damage Study

Expected Beam Background at GLC

CCD based Vertex Detector for GLC 16

Electron Damage Study

Test Sample CCDs 256x256 pixcels Made by Hamamatsu Readout Freq : 250kHz Readout Cycle : 2 sec Irradiation:

Sr-90: 0.6, 1.0, 2.0 x 1011/cm2

150 MeV beam: 0.5, 1.0 x 1011/cm2

CCD based Vertex Detector for GLC 17

Electron Damage Study

NIEL Hypothesis Bulk damage is thought to b

e proportional to non-ionizing energy loss (NIEL)

NIEL of electrons has strong energy dependence

e+/e- pair background hitting the inner-most layer of VTX at LC peaks at ~20MeV

High energy electron beam irradiation test

CCD based Vertex Detector for GLC 18

Electron Damage Study

Dark Current Surface dark current is

very well suppressed by using MPP (multi pinned phase) mode (inverted mode)

In MPP mode, dark current is dominated by bulk current

CCD based Vertex Detector for GLC 19

Electron Damage Study

Dark Current Pedestal In MPP mode, however,

spurious dark current (dark current pedestal: DCP) which is generated during clocking is observed

This DCP is thought to be due to impact ionization by holes trapped in interface levels

CCD based Vertex Detector for GLC 20

Electron Damage Study

Flatband Voltage Shift Surface damage in SiO2

causes shift of operation voltage

FVS is observed as shift of MPP threshold

CCD based Vertex Detector for GLC 21

Electron Damage Study

Hot Pixels

CCD based Vertex Detector for GLC 22

Electron Damage Study

Hot pixels Average dark current of

150MeV beam irradiated CCD is x2~5 larger than Sr-90 irradiated CCD

But hot pixel generation rate is completely different

This could be due to threshold effect of cluster-defect generation

Recoil Energy

Electron Threshold Energy

Point Defect

~20 eV ~200 keV

Cluster Defect

~2 keV ~5 MeV

Tree-like defect

~20 keV ~16 MeV

CCD based Vertex Detector for GLC 23

Electron Damage Study

Charge Transfer Inefficiency (CTI)

CCD based Vertex Detector for GLC 24

Electron Damage Study

CTI Model Calculation

CCD based Vertex Detector for GLC 25

Electron Damage Study

Other CTI Improvements Notch Channel

CCD based Vertex Detector for GLC 26

Electron Damage Study

Other CTI Improvements (cont.) Reduction of number of transfer

Multi Thread CCD (MT-CCD)

CCD based Vertex Detector for GLC 27

Summary

CCD based Vertex Detector for GLC 28

Summary (cont.)