Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC

C. Grah1, U. Harder1, H. Henschel1, E. Kouznetsova1, W. Lange1, W. Lohmann1, M. Ohlerich1,3, R. Schmidt1,3, K.

Afanaciev2, A. Ignatenko2

N18-6, Tuesday, Oct. 31st

1 Linear Collider, DESY, Zeuthen, Germany2 NCPHEP BSU, Minsk, Belarus3 BTU Cottbus, Germany

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Contents

Very forward region of the detectors for the International Linear Collider

BeamCal – requirementsTestbeam at CERN

Linearity of the response of CVD diamonds

Testbeam at the TU DarmstadtRadiation hardness of CVD diamonds

Conclusions

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Very Forward Region of the ILC Detectors

Interaction point

The purpose of the instrumentation of the very forward region is: Hermeticity: increase the coverage to polar angles > 5mrad Optimize Luminosity

EM calorimeter with sandwich structure: 30 layers of 1 X0

o3.5mm W and 0.3mm sensor Angular coverage from 5mrad to 28 mrad Moliére radius RM ≈ 1cm Segmentation between 0.5 and 0.8 x RM

BeamCal

LDC

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The Challenges for BeamCal

e+e- pairs from beamstrahlung are deflected into the BeamCal

15000 e+e- per BX

=> 10 – 20 TeV total energy dep.

~ 10 MGy per year strongly dependent on the beam and magnetic field configuration

=> radiation hard sensors

Detect the signature of single high energetic particles on top of the background.

=> high dynamic range/linearity

e- e+

Creation of beamstrahlung at the ILC

≈ 1 MGy/a

≈ 5 MGy/a

e-

e-

γ

e-

γ

e+e.g. Breit-Wheeler process

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Polycrystalline Chemical Vapour Deposited Diamonds

pCVD diamonds are an interesting material: radiation hardness (e.g.

LHC pixel detectors) advantageous properties

like: high mobility, low εR = 5.7, thermal conductivity

availability on wafer scale Samples from two

manufacturers are under investigation: Element SixTM Fraunhofer Institute for

Applied Solid-State Physics – IAF

1 x 1 cm2 200-900 μm thick

(typical thickness 300μm) Ti(/Pt)/Au metallization

(courtesy of IAF)

(courtesy of IAF)

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Linearity Test at CERN PSHadronic beam, 3 & 5 GeVFast extraction mode ~104-107 particles / ~10 ns

ADCsignal gate

10 ns

17 s

Diamond

Setup

Beam

Scint.+ PMTs.

Response of diamond sensor to beam particles (no preamplifier/attenuated)

Photomultiplier signals

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Response vs. Particle Fluence

30% deviation from a linear response for a particle fluence up to ~106 MIP/cm2

The deviation is at the level of the systematic error of the fluence calibration.

E64 FAP2

Fraunhofer IAFElement Six

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High Dose Irradiation

Irradiation up to several MGy using the injector line of the S-DALINAC:10 ± 0.015 MeV and beam currents from 10 to 100 nA corresponding to about 59 to 590 kGy/h

Superconducting DArmstadt LINear ACceleratorTechnical University of Darmstadt

Energy spectrum ofshower particles in BeamCal

V.Drugakov

2X0

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Preparations and Programme

GEANT4 simulation of the geometry

=> R = NFC/NSensor = 0.98

<Edep>/particle = 5.63 MeV/cm

Beam setup Sample Thickness, µm

Dose, MGy

E6_B2 (E6) 500 >1

DESY 8 (IAF) 300 >1

FAP 5 (IAF) 470 >5

E6_4p (E6) 470 >5

Apply HV to the DUT

Measure CCD ~20

min

Irradiate the sample~1 hour

CCD: Charge Collection Distance

collimator

preamp box

absorber

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Realization: Beam Setup

exit windowof beam line

collimator (IColl)

sensor box (IDia, TDia, HV) Faraday cup (IFC, TFC)

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CCD Setup

typical spectrum of an E6 sensor

Sr90 source

Preamplifier

Sensor box

Trigger box

&Gate

PA

discr

discr

delay

ADC

Sr90

diamond

Scint. PM1

PM2

Setups partly financed by EUDET.

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Results: CCD vs. Dose

100 nA (E6_4p) 100 nA (FAP5)

Silicon starts to degrade at 30 kGy.High leakage currents.Not recoverable.

CCD = Qmeas/Qinduced x thicknessBias voltage = 400V ≈> 1 V/μm

After absorbing 7MGy:

CVD diamonds still operational.

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Behaviour after Irradiation

Slight increase of currents forhigher doses.

No significant change of the current-voltage characteristics up to 1.5 MGy.

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CCD Behaviour after Irradiation

after 1.5 MGy

~ -30%

~ -80%

after 7 MGy

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After Irradiation: IAF Sample

strong „pumping“ behaviour.

before/after ~ 7MGy

signal recovery after 20 Gy

▪ FAP 5 irradiated, 1st measurement

▪ FAP 5 irradiated, additional 20 Gy

▪ before irradiation ▪ after irradiation

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Summary BeamCal is an important part of the instrumentation of

the very forward region of the ILC detectors. The requirements on the radiation hardness and linearity

of the sensors are challenging. PCVD diamonds are an interesting material for this task. The linearity of pCVD diamonds up to particle fluences of

106 particles/cm2/10ns is better than 30%. High dose irradiation using 10MeV electrons shows:

all CVD diamonds stay functional even after absorbing up to 7MGy.

degradation of the signal at high doses and dose rates. partial recovery of the signal after absorbing additional small

doses (~20 Gy). wide variation of the signal sizes as a function of the

absorbed dose is an issue for the use as a sensor for BeamCal.

http://www-zeuthen.desy.de/ILC/fcal/