Polycrystalline CVD Diamonds for the Beam Calorimeter of the ILC

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Polycrystalline CVD Diamonds for the Beam
Calorimeter of the ILC
C.Grah ILC ECFA 2006 Valencia, 9th November 2006
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Contents

• Very forward region of the detectors for the
  International Linear Collider
• BeamCal requirements
• Testbeam at CERN
• Linearity of the response of CVD diamonds
• Testbeam at the TU Darmstadt
• Radiation hardness of CVD diamonds
• Conclusions

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Very Forward Region of the ILC Detectors
Interaction point
BeamCal

• EM calorimeter with sandwich structure
• 30 layers of 1 X0
• 3.5mm 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

LDC

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

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The Challenges for BeamCal
e.g. Breit-Wheeler process
Creation of beamstrahlung at the ILC

• ee- pairs from beamstrahlung are deflected into
  the BeamCal
• 15000 ee- per BX
• gt 10 20 TeV total energy dep.
• 10 MGy per year strongly dependent on the beam
  and magnetic field configuration
• gt radiation hard sensors
• Detect the signature of single high energetic
  particles on top of the background.
• gt high dynamic range/linearity

1 MGy/a
5 MGy/a
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Polycrystalline Chemical Vapour Deposited Diamonds
(courtesy of IAF)

• pCVD diamonds are an interesting material
• radiation hardness (e.g. LHC pixel detectors)
• advantageous properties like high mobility, low
  eR 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)
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Linearity Test at CERN PS
Hadronic beam, 3 5 GeV Fast extraction mode
104-107 particles / 10 ns
Setup
Beam
Scint. PMTs.
Diamond
gate
signal
ADC
Response of diamond sensor to beam particles
(no preamplifier/attenuated) Photomultiplier
signals
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Response vs. Particle Fluence
Fraunhofer IAF
Element Six
E64
FAP2
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.
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High Dose Irradiation
Superconducting DArmstadt LINear
ACcelerator Technical University of Darmstadt
V.Drugakov 2X0
Energy spectrum of shower particles in BeamCal

• 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

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Preparations and Programme
preamp box
Beam setup
Sample Thickness, µm Dose, MGy
E6_B2 (E6) 500 gt1
DESY 8 (IAF) 300 gt1
FAP 5 (IAF) 470 gt5
E6_4p (E6) 470 gt5
absorber
collimator
Apply HV to the DUT

• GEANT4 simulation of the geometry

Measure CCD 20 min
Irradiate the sample 1 hour
gt R NFC/NSensor 0.98 ltEdepgt/particle
5.63 MeV/cm
CCD Charge Collection Distance
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Realization Beam Setup
exit window of beam line
collimator (IColl)
Faraday cup (IFC, TFC)
sensor box (IDia, TDia, HV)
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CCD Setup
Sr90
ADC
diamond
delay
Sr90 source
Scint.
discr
PM1

Gate
discr
PM2
Preamplifier
Sensor box
Trigger box
Setups partly financed by EUDET.
typical spectrum of an E6 sensor
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Results CCD vs. Dose
Silicon starts to degrade at 30 kGy. High leakage
currents. Not recoverable.
CCD Qmeas/Qinduced x thickness Bias voltage
400V gt 1 V/µm
After absorbing 7MGy CVD diamonds still
operational.
100 nA (E6_4p)
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Behaviour after Irradiation
No significant change of the current-voltage
characteristics up to 1.5 MGy.
Slight increase of currents for higher doses.
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CCD Behaviour after Irradiation
-80
-30
after 1.5 MGy
after 7 MGy
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After Irradiation IAF Sample
before/after 7MGy
? before irradiation ? after irradiation
strong pumping behaviour.
signal recovery after 20 Gy
? FAP 5 irradiated, 1st measurement ? FAP 5
irradiated, additional 20 Gy
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Summary

• PCVD diamonds are an interesting material as
  sensors for the BeamCal.
• 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.
• Started to investigate also other materials
  (GaAs, SiC) as alternative.
• Successfull irradiation-testbeam at the
  S-DALINAC. We plan to repeat the irradiation with
  more and other types of sensors next year.
• http//www-zeuthen.desy.de/ILC/fcal/