radiation hardness of the avalanche photodiodes for ecal cms detector at cern
DESCRIPTION
Radiation hardness of the Avalanche Photodiodes for ECAL CMS detector at CERN. A. Singovski The University of Minnesota. APD’s in the CMS detector. PbWO 4 crystal. Radiation doses are in red, 10 4 Gy. Neutron fluence in green 10 13 neutrons/cm 2 with E > 100 keV. - PowerPoint PPT PresentationTRANSCRIPT
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 1
Radiation hardness of the Avalanche Photodiodes for ECAL CMS detector
at CERN
A. Singovski The University of Minnesota
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 2
APD’s in the CMS detector
PbWO4 crystal
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 3
Radiation level after 10 years
Radiation doses are in red, 104 Gy. Neutron fluence in green 1013 neutrons/cm 2 with E > 100 keV.
Levels outside of the detector are down by a factor of 100 or more.
Crystal calorimeter
100
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 4
APD’s for CMS
Manufacturer:•Hamamatsu Photonics, Japan.
Quantity:•Two APD’s per crystal– 124,000 APD’s with spares.
Accessibility during operation:•None.
Radiation levels:•Maximum expected dose 200 kGy and 2 1013 neutrons/cm2.
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 5
Basic APD Structure:
APD is grown epitaxially on an n++ wafer.
Junction
Si2N4 AR coating
Groove to minimize
surface leakage current.
5 5 mm2
active area
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 6
APD radiation damage
Radiation damage of APD can influence ECAL performance by essentially two effects:
-rise of the bulk current increase APD noise contribution to the energy resolution
-early breakdown breakdown happens before APD can reach operation point at Gain=50
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 7
APD contribution to the ECAL resolution
Resolution:
where, a : due to intrinsic shower fluctuations & photo statistics
b : related to stability and reproducibility c : noise contributions CMS design goal : a ~3%, b~0.5%, c~200 MeV APD contributions: a - photo statistics (area, QE) & excess noise factor b - gain variation with bias voltage and temperature c - capacitance as series noise and dark current as parallel noise
E
cb
GeVE
a
E
E⊕⊕=
)(σ
σ σ σtotal parallel series= +2 2
( ) τσ qFMII dbdsparallel ⋅+= 2
⎟⎟⎠
⎞⎜⎜⎝
⎛+⋅
⋅= R
gCkT
series
7.02
4 2
τσ
M = APD gain F = excess noise factor τ=shapingtimeconstantq=electronchargeIds=darksurfacecurrentIdb=darkbulkcurrentR=seriesresistanceC=capacitanceofAPDandamplifierk=BoltzmannconstantT=absolutetemperatureg=transconductanceofamplifierfirststage
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 8
Irradiation Tests.
Irradiation with protons:•70 MeV protons beam at PSI – Switzerland.
•11013 hadrons/cm2 in ~ 2 hours.
Irradiation with gammas.•All irradiation with 60C0 source.
Irradiation with neutrons.•Californium source (252Cf) for irradiation at the University of Minnesota.
•2 1013 neutrons/cm2 in ~ 2 days.
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 9
Device failure
0
5
10
15
20
25
30
35
0 1000 2000 3000 4000 5000 6000 7000 8000Time (s)
Dark Current (
μ)A
Irradiation in a 70 MeV proton beam.
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 10
Neutron irradiation facility
Draws for irradiation
Use old tandem laboratory facility in Minneapolis to store and operate two 7 mg sources for irradiation samples.
•High and low flux areas 1013 and 1011
n/cm2 in 2 – 4 days.
•Must provide biases to components during irradiation.
•Return sources after 4 years of operation.
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 11
Neutron irradiation results
705 APD's Irradiated - Includes Source Decay
y = 1.3954E-11x
R2 = 8.6333E-01
0
50
100
150
200
250
300
0.0E+00 5.0E+12 1.0E+13 1.5E+13 2.0E+13
Integrated Neutron Flux (neutrons cm-2)
Id/M (nA) at Gain 50
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 12
Durk current
Total Current (dark current + ionisation current)
02468
101214161820
0.00E+00 5.00E+12 1.00E+13 1.50E+13 2.00E+13
total Neutron Flux / cm2
Current [
μ]A
Current vs Flux
0
5
10
15
20
25
0 2E+12 4E+12 6E+12 8E+12 1E+13 1.2E+13 1.4E+13
Total neutron flux
Current at M=50, mkA
3003006176
2802004514
70 MeV protons
1 MeV neutrons from 252Cf
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 13
Neutron irradiation summary
1.All APD tested so far survived -> no significant shift in breakdown voltage.
2.The mean bulk current after 2x1013 neutrons/cm2 is Id280nA (non-amplified value).
3.It corresponds to 14μA at Gain=50 and ~ 80MeV noise contribution (no-recovery case, CMS TDR).
Acceptable for CMS ECAL detector
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 14
Gamma irradiation
APDs
32 wires containing 60Co surround the probe and give a very uniform irradiation field.
Present activity is 2.5 kGy/h
60Co irradiation facility at PSI
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 15
Gamma irradiation results
Lot 34 Breakdown Voltage Comparison
-30
-25
-20
-15
-10
-5
0
5
8900 9000 9100 9200 9300 9400 9500 9600
APD #
VB(irradiated)-V
B(Hamamatsu) [V]
Rejected
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 16
Gamma irradiation results 2
APD with a significant shift of Vb after 60Co
irradiation
(vs. good one)
Id/Gain
Noise
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 17
Screening
Method:
- irradiate 100% of APD`s (0.5 Mrad) with Co-60 gamma source (at PSI);
- measure VB and Id(V) of all irradiated APD`s 1 day after irradiation (at PSI);
- measure noise at M=1, 50, 150, 300 before annealing (at CERN APD Lab)
- anneal all APD`s in the oven (for 4 weeks at T=80C, at CERN APD Lab);
- measure VB, Id(V) after annealing/ageing (at CERN APD Lab);
-reject potentially non-reliable APD`s: ones showing
-Shift of Vb more than 5V
-high Id
-high noise
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 18
APD rejection
High dark current High noise
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 19
Screening efficiency
Double irradiation (225 APDs from lot##33,34)
-5
-4
-3
-2
-1
0
1
2
3
0 50 100 150 200 250
APD #
Change of VB [V]dVB(after first Co-irr.)
dVB(after annealing)
dVB(after second Co-irr.)
225 APD`s which passed 1st irradiation and annealing were irradiated the 2nd time. No change of VB>2V was
found for all APD`s !!!
RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota 20
Gamma irradiation summary
1.APDs are sensitive to the gamma irradiation.
2.Several percents “die” after irradiation -> get a breakdown close to the operation point.
3.Screening, applied to 100% of APDs make them 99.9% rad. Hard.