RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota1 Radiation hardness of the...
-
Upload
stuart-bruce -
Category
Documents
-
view
217 -
download
2
description
Transcript of RESMDD02 July 10-12 2002, Florence, A.Singovski, University of Minnesota1 Radiation hardness of the...
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
Ecb
GeVEa
EE
⊕⊕=)(
σ
σ σ σtotal parallel series= +2 2
( ) τσ qFMII dbdsparallel ⋅+= 2
⎟⎟⎠⎞
⎜⎜⎝⎛ +⋅⋅= Rg
CkTseries
7.02
4 2
τσ
M = APD gain F = excess noise factor τ=σhapingτim econστanτq=elecτronchargeIdσ=darkσurfacecurrenτIdb=darkbulkcurrenτR=σerieσreσiστanceC=capaciτanceofAPDandam plifierk=Bolτzm annconστanτT=abσoluτeτem peraτureg=τranσconducτanceofam plifierfirστστage
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 (
mA)
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-11xR2 = 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 [
mA]
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
30030061762802004514
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 14mA 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.