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Investigation of radiation hard sensors for the ILC forward calorimeter. K. Afanaciev, Ch. Grah, A. Ignatenko, W. Lange, W. Lohmann, M. Ohlerich. International school-seminar Actual problems of microworld Physics Gomel 2007. Very Forward Region of the ILC Detector. BeamCal. - PowerPoint PPT Presentation
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Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
. Investigation of radiation hard sensors for the ILC forward calorimeter
K. Afanaciev, Ch. Grah, A. Ignatenko, W. Lange, W. Lohmann, M. Ohlerich
International school-seminar Actual problems of microworld Physics
Gomel 2007
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Very Forward Region of the ILC Detector
Interaction point
• The purpose of the instrumentation of the very forward region is:
– Hermeticity: increase the coverage to polar angles > 5mrad
– Fast beam diagnostics
EM calorimeter with sandwich structure:
30 layers of 1 X0
3.5mm W and 0.3mm sensor Angular coverage from 5 mrad to 28 mrad Moliére radius RM ≈ 1cm Segmentation between 0.5 and 0.8 x RM
BeamCal
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
The Challenges for BeamCal
e+e- pairs from beamstrahlung are deflected into the BeamCal
15000 e+e- per BX => Edep 10 – 20 TeV
~ 5 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/y
≈ 5 MGy/y
For 1 layer, per cell
Bethe-Heitler process
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Irradiation facility
Energy spectrum ofshower particles in BeamCal
V.Drugakov
2X0
Superconducting DArmstadt LINear ACceleratorTechnical University of Darmstadt
Irradiation up to several MGy using the injector line of the S-DALINAC:10 ± 0.015 MeV and beam currents from 2 to 100 nA corresponding to doses about 10 to 600 kGy/h
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Irradiation facility
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
.
Investigated materials
Gallium arsenide (GaAs), Polycristalline CVD Diamond (pCVD) Silicon (radiaton-hard and common detector-grade for comparison)
GaAs Si DiamondDensity 5.32 g/cm3 2.33 3.51
Pair creation E 4.3 eV/pair 3.6 13 Band gap 1.42 eV 1.14 5.47 Electron mobility 8500 cm2/Vs 1350 1800
Hole mobility 400 cm2/Vs 450 1200 Dielectric const. 12.85 11.9 5.7 Radiation length 2.3 cm 9.4 18.8
Ave. Edep/100 m(by 10 MeV e-) 69.7 keV 53.3 34.3
Ave. pairs/100 m 13000 9200 3600Structure p-n or insul. p-n insul.
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Methodology. Irradiation
exit windowof beam line
collimator (IColl)
sensor box (IDia, TDia, HV) Faraday cup (IFC, TFC)
•Irradiation under bias voltage•Monitoring of beam and sample currents, sample temperature
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Methodology. CCD Setup
typical spectrum of an E6 sensor
Sr90 source
Preamplifier
Sensor box
Trigger box
& Gate
PA
discr
discr
delay
ADC
Sr90
sample
Scint.
PM1
PM2
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
pCVD Diamond Detector
• pCVD diamonds are an interesting material:– radiation hardness– advantageous properties like: high
mobility, low εR = 5.7, thermal conductivity
– availability on wafer scale– Solid-state ionisation chamber (no p-
n junction)
• Samples from two manufacturers were investigated: – Element SixTM (ex-DeBeers)– Fraunhofer Institute for Applied
Solid-State Physics – IAF • 1 x 1 cm2 • 200-500 μm thick
(typical thickness 300μm)• Ti(/Pt)/Au metallization
(courtesy of IAF)
(courtesy of IAF)
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
>5470E6_4p (E6)
>5470FAP 5 (IAF)
>1300DESY 8 (IAF)
>1500E6_B2 (E6)
Dose, MGy
Thickness, µm
Sample
100 nA (E6_4p)
100 nA (FAP5)
After absorbing 7MGy: CVD diamonds still operational.
CVD Diamond. Irradiation
E6_4p
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
~ -80%
Signal decreased by 80 % after absorbed dose of about 7 GyBut signal is still visible.Slight increase in current, but still in pA range
CVD Diamond. Irradiation results
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
CVD Diamond. Irradiation results
Signal from sample decreases with time after irradiationfurther decrease after ‘purging’ trapping levels with UV light
Signal increases back after irradiation with small dose - ‘pumping’
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
GaAs Detector
Supplied by FCAL group at JINRProduced by Siberian Institute of Technology, Tomsk
Sample is semi-insulating GaAs doped by Sn(shallow donor) and compensated by Cr (deep acceptor). This is done to compensate electron trapping centers EL2+ and provide i-type conductivity.
Sample works as a solid state ionisation chamberStructure provided by metallisation (similar to diamond)
500 m thick detector is divided into 87 5x5 mm padsand mounted on a 0.5mm PCB with fanout
Metallisation is V (30 nm) + Au (1 m)
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Rpad 500 MOhm
I-V and C-V
-500 -400 -300 -200 -100 0 100 200 300 400 500
-0.0000016
-0.0000014
-0.0000012
-0.0000010
-0.0000008
-0.0000006
-0.0000004
-0.0000002
0.0000000
0.0000002
0.0000004
0.0000006
0.0000008
0.0000010
0.0000012
Guardring nicht angeschlossen
current-voltage-curve: Ring 6
curr
en
t [A
]
Voltage [V]
Pad-Nummer 1 3 5 7
0 20 40 60 80 100
1.20E-011
1.30E-011
cap
aci
tan
ce [F
]
Stepnummer [Dealy = 2000ms]
r8p5 r6p4 r3p3 r11p6
Zeitkonstante Spannung
Constant pad capacityno dependence on V =>no structure
Pad capacity about 12 pF
Almost linear IV characteristics => resistor
Currents in the order of 0.2 A @ 100V
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
GaAs. Signal
Clear separation of peaks from Sr90 source
S8 pad4ring 4
S8 pad4ring 6
Quite homogeneous response over different pads
Saturation of signal @ about 200V bias
Collection efficiency 60%
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
GaAs. Irradiation
Samples 7&8, pad4, ring6 @ 200V
Preliminary
Sample 7 Sample 8
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
GaAs. Irradiation results
Sample 8 pad4 ring6
Results: CCE dropped to about 6% from 60% (by ~ 90%)but signal is visible for absorbed dose of about 1 MGy
Dark current increased 2 times (from 0.4 to 1 A @ 200V)
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Silicon. Comparison
For comparison purposes two silicon detectors were irradiated(detector grade by Micron)
Degradation of signal starts at doses 40 kGyAt higher doses dark current and noise levelincreases dramatically (from 10 nA to A).No clear signal visible
Tested this year Radiation hard silicon - no final results yetbut general behavior similar => high currents after about 70 kGy
Apr 21, 2023 Actual problems of microworld physics. Gomel 2007
Conclusion
New results - two more diamond samples from E6 irradiated this yearSingle crystal CVD diamond sample irradiated Radiation-hard silicon sample irradiated
Analysis in progress
Further work is planned for CVD diamond and GaAsPossible new material - SiC
At the moment CVD diamond and GaAs prove to be sufficientlyradiation hard for application in BeamCal
Inconsistent results from different diamond samples could be a problemPumping behavior could be a problem for calorimetry
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