Radiation Test Report Paul Scherrer Institute – Proton

CERN Div./Group
the
EN/STI
CERN
Large
Hadron
Collider
EDMS Document No.
CH-1211 Geneva 23
Switzerland
project
RadiationTestReport
PaulScherrerInstitute–ProtonIrradiationFacility
1. Responsibility
Tested by: Giovanni SPIEZIA / Paul PERONNARD/Julien MEKKI Group: EN‐STI‐ECE Date start: 02/09/2011 Date end: 05/09/2011 Equipment type concerned: Power Converter 2. DUTidentificationandoperatingconditions
DUT name DUT type Test type Samples tested Samples per board Manufacturer and Lot code CTR 8 4 TLP124 Optocoupler
Response time 3 3 Unknown SET 8 4 SET dV/dt 3 3 DUT name DUT type Test type Samples tested Samples per board under test Manufacturer and Lot code CTR 8 4 4N35 Optocoupler Response time 3 3 Unknown SET 4 4 SET dV/dt 3 3 DUT name DUT type Test type Samples tested Samples per board under test Manufacturer and Lot code HCNR Optocoupler CTR 8 4 Unknown EDMS number
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3. Schematicsanddescriptionofthetestsetup
TheschematicspresentedinthisreporthavebeenagreedwiththeTE/EPCteaminaccordancetothe
use of those components in the power converters. The input current is always ON and varies to
compensate the output current decreasing. Thus, annealing effects are induced, which should reduce
the radiation effects according to the literature. The schematics for the CTR measurements of the
TLP124,4N35andHCNR200optocouplersarepresentedinFigures1,2and3respectively.
CurrentTransfertRatio:
Schematics
Vd Figure1:BiasconditionsfortheTLP124optocouplers.
Vd Figure2:Biasconditionsforthe4N35optocouplers.
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Vd Figure3:BiasconditionsfortheHCNR200‐300eoptocouplers
The current crossing the LED (input current ‐ If) and currents crossing the phototransistor or
photodiodeincaseofHCNRtests(outputcurrent‐Ie)aremeasuredviatwovoltages(VdandVe):
If=(Vd‐Vf)/Rf
Ie=Ve/Re
where Vf is the voltage across the LED which is constant, Rf is the input resistance to measure the
current crossing the LED (R1 for TLP124/4N35 and R6 for HCNR on the schematics) and Re is the
resistance between the phototransistor emitter (TLP124/4N35) or photodiode (HCNR200) and the
GNDtomeasuretheoutputcurrent–Ie(R2ontheschematics).
FortheTLP124and4N35optocouplers,themeasurementofVdandVeareperformedontheOutput6
andOutput5respectively(ontheschematics).
For the HCNR200‐300e, the measurement of Vd and Ve are performed on the Output2 and Output1
respectively (on the schematics). In addition, since the photodiodes (IC2B and IC2C) are coupled
optically, made on the same wafer, and their respective cathodes are connected to the VCC, their
voltagesareidentical.
Foralltheconfigurationspresentedinthissection,theCTRdegradationduetothebeamirradiation
will be compensated by increasing the LED current (feedback loop). The output current Ie (via the
output voltage Ve) is fixed by the input reference voltage applied at the connection J1. This
configurationalsoimpliesthatVceisconstantduringirradiation.
Theoperationalamplifierstagewasoutofthebeamspot.Infact,a5cmcollimatorwasusedtoshoot
only on the optocouplers which are mounted in a 5 cm diameter on the PCB. This is valid for all the
referencesundertest.
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Thefollowingtableillustratesthedifferentconfigurationsforeachboard.Twoboardsperoptocoupler
havebeenirradiatedwithadifferentinitialbias.Oneachboardthereare4optocouplersofthesame
typeandbiasedinthesameconfigurations.
(V) Vcc (V) Rf (ohms) Re (ohms) Ie (mA) If Initial (mA) Vce (V) 4.7 +10 / ‐10 NA 470 4700 1 0.3 5 4.8 4.7 +8 / ‐8 NA 470 470 10 1.5 3 1.08 4.8 4.7 +15 / ‐15 NA 470 4700 1 1.3 10 1.15 4.8 4.7 +13 / ‐13 NA 156 470 10 8 8 470 5
5 1 NA 5
47 10 NA Board name Vf (V) TLP124_1 1.06 4.8 TLP124_2 1.05 4N35_1 4N35_2 HCNR_1 HCNR_2 1.45 1.53 Ve(V) Vref(V) 0.5 4.7 0.5 4.7 V+/V‐ +15 / ‐15 +15 / ‐15 15 15 470 1×10 1×10 Table1:ConfigurationsoftheTLP124and4N35optocouplersmeasuredbyfixingoutputcurrentat1and10mA.TheHCNR
optocouplerhavebeenmeasuredwithanoutputcurrentfixedat5and50μA.
TestSetup
The DUT is powered with 2 dual output DC power supplies (Agilent E3648A). One is used to supply the amplifier for the feedback control (V+,V‐) and the second one is used to apply an input reference voltage which fix the output voltage Ve (voltage applied via the connector J1 in Figure 1‐3). The measurement of the Vf variations and the monitoring of Ve are performed with the DAQ unit HP34970. The forward voltage of the diode is supposed to be constant. It was monitored during the irradiation with local measurements to verify this assumption. In addition, for the HCNR measurements, one of the power supplies is also used to supply the photodiode of the optocoupler. For the sake of completeness a Ve signal was connected to the Oscilloscope to register eventual SET. The details of the scope are given in the Section of the SET measurement. The following figure illustrates the test setup used for the CTR measurement: EDMS number
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HP34970
GPIB
Vf, Ve monitor
DUT
Optocouplers
Vref, V+/V‐
Vcc (only for HCNR)
GPIB
Agilent E3648A Figure4:TestsetuptoevaluatetheCTRvariationversusdose
Response time: Schematics
The Figures 5 and 6 show the schematics that have been used for characterizing the response time of the optocouplers. The idea is to measure the falling time of the optocoupler output and check its variation along the irradiation. Three samples are mounted on the board under test per each type of optocoupler. Figure5:BiasconditionsfortheTLP124optocouplers
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Figure6:Biasconditionsforthe4N35optocouplers
The current crossing the LED (input current ‐ If) and current crossing the phototransistor (output
current‐Io)aremeasuredviatwovoltages(V+andVo)whichareproportionaltothecurrents.
Thecalculationsofthecurrentsareperformedasthefollowing:
If=(V+‐Vf)/Rf
Io=(Vcc‐Vo)/Ro
WhereV+istheinputvoltageappliedviatheconnectorJ6ontheschematics,Vfisthevoltageacross
theLEDwhichisconstant,RfistheinputresistancetomeasurethecurrentcrossingtheLED(R5onthe
schematics) and Ro is the output resistance (R3 on the schematics) between the phototransistor
collectorandtheVcctomeasuretheoutputcurrent–Io.
ThemeasurementofVoisperformedontheOutput4ontheschematics.
Being a linear optocoupler, the HCNR response time is affected by the transient time of the feedback loop. This test is not presented. TestSetup
A square signal has been applied to the input of the optocoupler with the following characteristics: Frequency = 1 kHz, amplitude 0‐5V and Time ON = 100 μs. A Tektronix DPO7254 oscilloscope (2.5GHz, 40GS/s) was connected to the output of the Device Under Test via a 50 ohms coaxial cable to measure the response time and verify its variation as a function of TID. The input impedance of the scope was set to 1M Ohms. To avoid problems of contamination, the scope was located in the maze of the bunker. BNC cables of 10 meters were used to connect the instrument to the outputs of the DUTs. The polarizations for each board are given in the following table: Board name V+ VCC Vf(V) If (mA) Vo(V) Io (mA) TLP124 4 10 1.1 6 1 19 4N35 4 5 1.1 6 1 8 Table2:PolarizationoftheTLP124and4N35optocouplers.
The following figure illustrates the test setup for the time response measurement: EDMS number
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ETHERNET
Figure7:Testsetuptoevaluatethetimeresponsevariationversusdose
Single Event Transients evaluation: Schematics: The Figures 8 and 9 show the schematics that have been used for characterizing the SET sensitivity of the TLP124 and 4N35 optocouplers. HCNR was not tested. EDMS number
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Figure8:BiasconditionsfortheTLP124optocouplers
Figure9:Biasconditionsforthe4N35optocouplers
To evaluate the SET sensitivity of the optocoupler, the input LED has been short circuited to the ground. An induced transient will be read on the output of the optocoupler (in Figure 8‐9, connector J3). Test setup: All the devices share the same setup for the evaluation of the Single Event Transient sensitivity. A Tektronix DPO7254 oscilloscope (2.5GHz, 40GS/s) was connected to the output of the Device Under Test via a 50 ohms coaxial cable. The following figure illustrates the test setup for the time response measurement: ETHERNET
Figure10:Testsetuptoevaluatethetimeresponsevariationversusdose
For evaluating the SET sensitivity of the optocoupler, the oscilloscope was configured in trigger mode to detect a falling edge. The oscilloscope is remotely controlled by its Ethernet interface. The input impedance of the scope was set to 1M ohms. To avoid problems of contamination, the scope was located in the maze of the bunker. EDMS number
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Figure11:Triggerconfigurationpanel.
Therefore, BNC cables of 10 meters were used to connect inputs of the instrument to the outputs of the DUTs. Figure 12 shows a laboratory test. The oscilloscope is connected to the pulse generator Standford DG535 with a 10 meter cable. A pulse with duration of 15ns and amplitude of 100mV was generated. . The oscilloscope response is in figure 12 where the horizontal scale is 20ns and the vertical one is 20mV. The observed response shown that the test setup is able to detect a SET similar to that pulse. Figure12:Observedpulsewith10metersofcable Single Event Transients with dV/dT evaluation: Schematics The Figures 13 and 14 show the schematics that have been used for characterizing the SET sensitivity of the TLP124 and 4N35 optocouplers by applying a signal with a high dV/dt between the cathode of the diode and the emitter of the output. The goal is to emulate the spikes at high dV/dt coming from the power switches that will be driven by the optocouplers in real applications. EDMS number
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Figure13:BiasconditionsfortheTLP124optocouplers
Figure14:Biasconditionsforthe4N35optocouplers
To evaluate the SET sensitivity of the optocoupler with dV/dt, a square signal with frequency equal to 100 kHz, a time rise of about 5ns and amplitude of 0‐10 V is applied via the connector J2 on the schematics. Therefore a square signal is applied between the cathode and the emitter of the phototransistor to simulate a dV/dt of 2 kV/μs. An eventual transient will be read on the output of the optocoupler (in Figure 13‐14 connector J3). Test setup: All the devices share the same setup for the evaluation of the Single Event Transient sensitivity. A Tektronix DPO7254 oscilloscope (2.5GHz, 40GS/s) was connected to the output of the Device Under Test via a 50 ohms coaxial cable. The instrument is configured as described in the previous section. The following figure illustrates the test setup for the SET sensitivity evaluation with dV/dt: EDMS number
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ETHERNET
Figure15:TestsetuptoevaluatetheSETsensitivitywithdV/dt
4. Beamconditions
The tests have been carried out at the Proton Irradiation Facility (PIF) of PSI. The initial proton beam for PIF is delivered from the PROSCAN accelerator with the help of the primary energy degrader, which allows setting a few discrete initial beam energies in the range from 250 MeV down to 30 MeV. The beam is subsequently guided to the Experimental Area where the PIF facility is located. A further set of collimators is placed before the DUT to set lower energy. For the above tests, the primary energy was set to 230 MeV. The beam flux is measured by means of two ionization chambers IC1 and IC2 which are placed upstream and downstream the collimators, respectively. The counting of the IC1 and IC2 are calibrated to measure the beam flux at the position of the DUT, which is 11 cm far away from the IC2 (downstream the collimator). That operation is done before the test by comparing the counting of the IC1 and IC2 with respect to the output of a scintillator detector which is mounted where the DUT will be placed (11 cm from the IC2). The TID is provided by the facility and is given in Gy (Si). The table reports the beam conditions, specifying the final total fluence and TID for each run. The dose rate is higher than the one expected for the LHC tunnel (tenths of Gy per year) which would be unpractical to test. Therefore, ELDR (Enhanced Low Dose Rate) effects might not be correctly evaluated. A TID, at least 2 times higher than the one fixed as a target (50 Gy) was reached in order to compensate for possible ELDR effect. Moreover, one has to consider that the proton beam at 230 MeV will induce also Displacement Damage effects. EDMS number
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Run # DUT id Samples Energy tested [MeV] 1 TLP124_1 4 2 TLP124_2 3 Fluence (p/cm2) TID (Gy) If initial Ie (mA) Vce(V)
(mA) 230 5.6E+11 306 0.3 1 5.1 4 230 2.08E11 112 1.5 10 4.9 4N35_1 4 230 4.38E+11 235 1.3 1 10.1 4 4N35_2 4 230 1.91E+11 103 8 10 8.1 5 HCNR_1a 4 230 9.35E+10 50 10 47×10‐3 NA 6 HCNR_1b 4 230 4.73 E+11 50‐304
1 5×10‐3 NA 7 HCNR_2 4 230 5.24 E+11 281 10 47×10‐3 NA Table3:BeamconditionsfortheevaluationoftheCTRvariationoverdose
Alltestpresentedinthistable areperformedwithafluxof 1.65×108p/cm2/s and a doserateof 8.8
rad/s(317Gy/h).
Table4reportsthebeamconditionsfortheresponsetimetests.
Run Samples Energy TID DUT id Fluence (p/cm2) # tested [MeV] (Gy) 1 TLP124 3 230 4.65E11 250 2 4N35 3 230 2.03E11 125 Table4:Beamconditionsfortheevaluationofthetimeresponsevariationoverdose
5. Cumulativeeffectresults:CTR
Although, the CTR degradation is reported as a function of the TID, one has to note that the proton beam at 230 MeV will also cause Displacement Damage. Thus, the results cannot be compared directly with Co60 irradiation. Table 5 gives the cumulative TID for each tested device. DUT id TLP124_1 TLP124_2 4N35_1 4N35_2 HCNR_1a Cumulative TID (Gy) 305 112 235 103 50 EDMS number
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HCNR_1b HCNR_2 254 281 Table5:CumulativeTIDforeachDUT
Figures 16 to 22 and Tables 6 to 12 show the variation of the CTR and normalized CTR as a function of the cumulated TID for the three optocouplers tested at two values of the output current Ie. Normalized CTR is also considered and is equal to: CTR _ Norm 
CTR
CTR0
where CTR0 is the initial current transfer ratio of the optocoupler and CTR is the current transfer ratio of the optocoupler during irradiation given by the following equation: CTR 
Ie
If
where Ie and If are the output and input current, respectively. The following results are presented: (i) plot of the CTR and normalized CTR; (ii) table with the CTR values as a function of the TID; two tables are given for each case. The values of table a refers to the sample which exhibited the worst CTR degradation; the values of Table b refers to the sample which exhibited the worst degradation of the normalized CTR in order to take into account the influence of the initial CTR. The plots and the tables are given for each optocoupler and for each bias condition. Results for the TLP124 CTR variation versus dose: (a) (b) Figure16:VariationsoftheTLP124CTR(a)andCTRnormalized(b)versuscumulateddoseforthe4optocouplers
testedatIe=1mA.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
EDMS number
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(a) (b) Figure17:VariationsoftheTLP124CTR(a)andCTRnormalized(b)versuscumulateddoseforthe4optocouplers
testedatIe=10mA.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
Table 6 shows the values of the CTR and normalized CTR variation versus the cumulated TID for the TLP124 optocoupler measured at Ie = 1 mA. The values refer to the sample with the worst CTR degradation (a‐
sample 2) and to the sample with the worst normalized CTR (b‐sample 1), although the spread among the 4 samples is not that high. For each test configuration, the TID range where the device response is within specifications is highlighted in red. The specifications have been taken from the datasheets. As the device manufacturer is not known, the datasheets have been taken from Toshiba and Hewlett Packard for the TLP124/4N35 and HCNR200 respectively. TID (Gy) CTR CTR_Norm TID (Gy) CTR CTR_Norm 0 3.8 1 0 5.37 1 10 2.4 0.64 10 3.36 0.62 20 1.7 0.46 20 2.32 0.43 30 1.3 0.35 30 1.73 0.32 40 1 0.27 40 1.35 0.25 50 0.85 0.22 50 1.1 0.2 75 0.57 0.15 75 0.72 0.13 100 0.41 0.1 100 0.51 0.095 150 0.25 0.065 150 0.3 0.057 EDMS number
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200 0.17 0.044 200 0.2 0.038 250 0.12 0.032 250 0.14 0.027 306 0.009 0.024 306 0.11 0.02 (a) (b) Table 6: Maximum observed degradation of the TLP124 CTR (a) and Normalized CTR (b) at different doses
measuredatIe=1mA.
The datasheet of the device indicates that the minimum current transfer ratio is 100 % (CTR = 1). This allows stating that the degradation of the CTR versus TID is not included within the device specifications. The device goes out of specification at a TID higher than 40 Gy. Table 7 shows the values of the CTR variation as a function of the TID for the TLP124 measured at Ie = 10 mA. The values refer to the sample with the worst CTR degradation (a‐sample 2) and to the sample with the worst normalized CTR (b‐sample 1), although the spread among the 4 samples is not that high. For each test configuration, the TID range where the device response is within specifications is highlighted in red. TID (Gy) CTR CTR_Norm TID (Gy) CTR CTR_Norm 0 5.8 1 0 6.87 1 10 4.1 0.71 10 4.84 0.7 20 3.2 0.55 20 3.7 0.54 30 2.6 0.44 30 2.95 0.43 40 2.1 0.36 40 2.43 0.35 50 1.8 0.3 50 2.06 0.3 75 1.2 0.22 75 1.43 0.21 93 1 0.16 93 1.13 0.17 100 0.9 0.16 100 1.05 0.15 105 0.87 0.15 112 0.92 0.13 (a) (b) Table 7: Maximum observed degradation of the TLP124 CTR (a) and normalized CTR (b) at different doses
measuredatIe=10mA.
It is indicated in the datasheet of the device that the minimum current transfer ratio is 100 % (CTR = 1). This allows stating that the degradation of the gain versus TID is not within the device specifications. The device EDMS number
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goes out of specification at a dose higher than 93 Gy. Thus, the CTR degradation is less pronounced at high output current. It was not possible to continue the test beyond 110 Gy, since the feedback amplifer reached its maximum output current. Results for the 4N35 CTR variation versus dose: (b) (a) Figure18:Variationsofthe4N35CTR(a)andCTRnormalized(b)versuscumulateddoseforeach4optocouplers
testedatIe=1mA.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
(a) (b) Figure19:Variationsofthe4N35CTR(a)andCTRnormalized(b)versuscumulateddoseforeach4optocouplers
testedatIe=10mA.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
Table 8 shows values of the CTR variation as a function of the TID for the 4N35 optocoupler measured at Ie = 1 mA. The values refer to the sample with the worst CTR degradation (a‐sample 3) and to the sample with the worst degradation of the normalized CTR (b‐sample 2), although the spread among the 4 samples is not EDMS number
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that high. For each test configuration, the TID range where the device response is within specifications is highlighted in red. TID (Gy) CTR CTR_Norm TID (Gy) CTR CTR_Norm 0 0.73 1 0 0.78 1 10 0.57 0.78 10 0.6 0.77 16 0.5 0.69 18 0.5 0.66 20 0.46 0.64 20 0.49 0.62 30 0.39 0.53 30 0.4 0.52 40 0.33 0.45 40 0.34 0.44 50 0.28 0.39 50 0.29 0.38 75 0.21 0.29 75 0.21 0.27 100 0.16 0.22 100 0.16 0.2 150 0.1 0.14 150 0.1 0.12 200 0.07 0.098 200 0.07 0.088 235 0.05 0.079 235 0.05 0.071 (a) (b) Table8:Maximumobserveddegradationofthe4N35CTR(a)andnormalizedCTR(b)atdifferentdosesmeasured
atIe=1mA
It is indicated in the datasheet of the device that the minimum current transfer ratio at If = 1mA is 50 % (CTR = 0.5). This allows to state that the degradation of the gain versus TID is not within the device specifications. The device goes out of specification at a TID higher than 15 Gy. Table 9 shows values of the CTR variation as a function of the cumulated TID for the 4N35 optocoupler measured at Ie = 10 mA. The values refer to the sample with the worst CTR degradation (b‐sample 2) and to the sample with the worst normalized CTR (a‐sample 1), although the spread among the 4 samples is not that high. For each test configuration, the TID range where the device response is within specifications is highlighted in red. The test was stopped at about 96 Gy due to saturation of the feedback amplifier which reached its maximum output current. The last values in the table are from the samples 4 whose amplifier saturated at 103 Gy. TID (Gy) CTR CTR_Norm TID (Gy) CTR CTR_Norm 0 1.2 1 0 1.3 1 EDMS number
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10 0.99 0.82 10 1.1 0.8 20 0.84 0.69 20 0.92 0.68 30 0.73 0.6 30 0.79 0.59 40 0.64 0.53 40 0.69 0.51 50 0.57 0.47 50 0.61 0.45 75 0.43 0.36 75 0.46 0.34 90 0.38 0.31 96 0.38 0.28 103 0.39 0.27 103 0.39 0.27 (a)
(b)
Table9:Maximumobserveddegradationofthe4N35CTR(a)andCTRNormalized(b)atdifferentdosesmeasured
atIe=10mA
It is indicated in the datasheet of the device that the minimum current transfer ratio at If = 8 mA is 100 % (CTR = 1). This allows stating that the degradation of the gain versus dose is not within the device specifications. The device goes out of specification at a dose higher than 10 Gy. Results for the HCNR CTR variation versus dose: (a) (b) Figure 20: Variations of the HCNR CTR (a) and normalized CTR (b) as a function of the cumulated TID for the 4
optocouplers tested at Ie = 47 μA up to 50 Gy. The test was interrupted at 50 Gy because of a problem on the
sample1oftheboard.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
After 50 Gy, the radiation test has been stopped to measure manually the LED voltage for checking if it changes versus radiation level. The LED voltage remains constant during the radiation test. Once this EDMS number
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verification has been performed, during the warm up test, it appears that the optocoupler 1 did not work anymore. Therefore, the board has been changed by the HCNR_2, which was initially foreseen to operate with an initial If of about 1 mA, to continue the test. For this reason the HCNR_2 board was biased to have an initial If of about 10 mA. The results are presented in the following figures. (a) (b) Figure21:VariationsoftheHCNRCTR(a)andnormalizedCTRnormalized(b)versuscumulateddoseforthe4optocouplers
testedatIe=47μAfrom0Gyto280Gy.Thecorrespondingproton230MeVfluenceisindicatedonthesecondaryx‐axis. It was not possible to repair the sample 1 of the board HCNR_1. It was nevertheless used for the test of the CTR, cumulating a TID from 50 to 300 Gy fixing the output current at about 5 μA. (a) (b) Figure22:VariationsoftheHCNRCTR(a)andCTRnormalized(b)versuscumulateddoseforeach4optocouplers
tested at Ie = 5 μA from 50 Gy to 300 Gy. The initial TID is 50 Gy. This was cumulated in a previous run. The
correspondingproton230MeVfluenceisindicatedonthesecondaryx‐axis.
EDMS number
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Table 10 shows the values of the CTR variation as a function of the cumulated TID for the HCNR optocoupler measured at Ie = 47 A from 0 to 50 Gy (before optocoupler 1 did not work anymore). The values refer to the worst case of the degradation of the CTR (a‐sample 1) and normalized CTR (b‐sample 4). TID (Gy) CTR CTR_Norm TID (Gy) CTR CTR_Norm 0 4.2×10‐3 1 0 4.4×10‐3 1 10 3.9×10‐3 0.96 10 4.1×10‐3 0.95 20 3.8×10‐3 0.92 20 3.9×10‐3 0.91 30 3.7×10‐3 0.89 30 3.8×10‐3 0.88 40 3.6×10‐3 0.86 40 3.7×10‐3 0.85 50 3.4×10‐3 0.83 50 3.6×10‐3 0.82 (a) (b) Table 10: Maximum observed degradation of the HCNR CTR (a) and normalized CTR (b) at different doses
measuredatIe=47μA(upto50Gy).
It is indicated in the datasheet of the device that the minimum current transfert ratio at If = 10 mA is 0.25 % (CTR = 2.5×10‐3). This allows to state that the degradation of the CTR versus dose is within the device specifications up to about 50 Gy at least. Table 11 shows the values of the CTR variation as a function of the cumulated TID for the HCNR optocoupler measured at Ie = 47 uA from 0 to 280 Gy. The values refer to the worst case of the degradation of the CTR (a‐sample 2) and normalized CTR (b‐sample 1). TID (Gy) CTR CTR_Norm TID (Gy)
CTR CTR_Norm 0 4.2×10‐3 1 0 4.4×10‐3 1 10 4×10‐3 0.95 10 4.3×10‐3 0.96 20 3.8×10‐3 0.92 20 4.1×10‐3 0.92 30 3.7×10‐3 0.89 30 3.9×10‐3 0.88 40 3.6×10‐3 0.86 40 3.8×10‐3 0.85 50 3.5×10‐3 0.83 50 3.7×10‐3 0.82 75 3.2×10‐3 0.77 75 3.4×10‐3 0.76 EDMS number
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100 3×10‐3 0.72 100 3.1×10‐3 0.71 150 2.6×10‐3 0.63 150 2.7×10‐3 0.61 175 2.5×10‐3 0.6 175 2.6×10‐3 0.58 200 2.3×10‐3 0.57 200 2.4×10‐3 0.55 250 2.1×10‐3 0.51 250 2.2×10‐3 0.5 262 2×10‐3 0.5 280 2×10‐3 0.46 (a) (b) Table 11: Maximum observed degradation of the HCNR CTR (a) and normalized CTR (b) at different doses
measuredatIe=47μA(measuredupto280Gy).
It is indicated in the datasheet of the device that the minimum current transfer ratio at If = 10 mA is 0.25 % (CTR = 2.5×10‐3). This allows to state that the degradation of the gain versus dose is not within the device specifications. The device goes out of specification at a TID higher than 175 Gy. Table 12 shows values of the CTR variation as a function of the cumulated TID for the HCNR optocoupler measured at Ie = 5 A from 50 Gy to about 250 Gy. The values refer to the worst case of the degradation of the CTR and normalized CTR (sample 4). TID (Gy) CTR CTR_Norm 50 3.6×10‐3 0.72 60 3.4×10‐3 0.68 70 3.3×10‐3 0.66 80 3.2×10‐3 0.63 90 3×10‐3 0.61 100 2.9×10‐3 0.58 125 2.7×10‐3 0.53 150 2.5×10‐3 0.49 175 2.3×10‐3 0.45 200 2.1×10‐3 0.42 250 1.9×10‐3 0.38 EDMS number
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1.7×10‐3 305 0.33 Table 12: Maximum observed degradation of the HCNR transistor gain at different doses measured at Ie = 5 μA
measuredfrom50to305Gy
It is indicated in the datasheet of the device that the minimum current transfert ratio at If = 1 mA is 0.25 % (CTR = 2.5×10‐3). The device goes out of specification at a dose higher than 150 Gy. The maximum TID value at which the device is still within specifications will depend on the initial CTR value of the optocoupler in the real application. A possible strategy to evaluate the TID, at which the device will be out of specifications, is the following. One can measure the initial CTR and then can consider the worst CTR_Norm degradation which has been given on each Tables b. As a matter of fact, the 4 samples under test for each bias configuration showed similar response. Thus, in simpler way, one can consider the maximum TID value indicated for each optocoupler. 6. Cumulativeeffectresults:Responsetime
This test aims at evaluating the variation of the response time as a function of the TID. The optocoupler output is at Vcc level. The falling time of the optocoupler output is measured at different TID by applying a pulse on the LED input. Thus, the LED current is null during the irradiation. The following table shows the results for the response time of the TLP124 optocouplers. Ch1 is the input pulse on the LEDs. Ch2, ch3, Ch4 are the optocouplers outputs. 3 samples have been measured. The table a) presents the fall time of the outputs and the table b) represent the turn‐on time which is the delay of the output (Ch2 or ch3 or ch4) with respect to the input (Ch1) ch1 Rise Time[s] ch2 ch3 ch4 Fall time [s] TID[Gy] 0 1E‐09
6.52 6.26
6.02
1E‐09
14 13
14
1E‐09
17 17
17
1E‐09
14 14
14
1E‐09
12 13
14
1E‐09
10 10
12
20 40 60 100 178 250 a).Falltime
Delay2‐1 [s] 3.1 Delay3‐1[s] 3.1
Delay4‐1[s] 3.1
3.54 3.52
3.48
TID 0 20 EDMS number
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4.98 5
5.14
5.35 5.6
5.6
5.35 5.6
5.6
5.55 5.45
5.8
6.35 6.3
6.25
40 60 100 175 250 b). Turn –on time. Table13:VariationoftheTLP124optocouplerresponsetimeversusTID.
The following Figure shows the response time of the optocoupler TLP124 at different TID levels. (a) (b) (c) (d) EDMS number
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(f) (e) Figure23:ResponsetimeoftheOptocouplerTLP124at(a)0,(b)20,(c)40,(d)60,(e)100and(f)250Gy.
The following table shows the time response for the 3 4N35 optocouplers. . Ch1 is the input pulse on the LEDs. Ch2, ch3, Ch4 are the optocouplers outputs. 3 samples have been measured. The table a) represents the fall time of the outputs and the table b) represents the delay of the output with respect (Ch2 or ch3 or ch4) to the input (Ch1): ch1 Rise Time 1E‐09
ch2 ch3 ch4 Fall time [s] 5.3 5.3
5.3
1E‐09
4.7 5.0
5
1E‐09
5.3 5.2
5.2
1E‐09
5.7 6.0
5.7
1E‐09
6.6 6.6
6.7
1E‐09
8.2 8.3
8.4
1E‐09
9.9 9.6
9.5
0 20 50 75 100 125 150 a)
Delay2‐1 [s] 3.5 Delay3‐1 [s] 3.5
3.9 3.9
Delay4‐1 TID [Gy]
[s] 3.4
0 3.9
TID[Gy] 20 EDMS number
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4.95 5.0
4.9
6.2 6.1
6.1
7.8 7.8
7.8
10 9.8
9.6
12 12
11
50 75 100 125 150 b) Table14:Variationofthe4N35optocouplerresponsetimeversusdose
The following Figure shows the response time of the optocoupler 4N35 at different TID. (a) (b) (c) (d) EDMS number
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(f) (e) Figure24:ResponsetimeoftheOptocouplerTLP124at(a) 0,(b)20,(c)40,(d)60,(e)100and(f)250 Gy.The
amplitudescaleis1V/div,thetimescaleis10s/Div.
It is difficult to evaluate the degradation of the time response. The CTR degradation is very sharp; having fixed the input current If, the output current Ie decreases, and the output signal is not a proper square ranging from Vcc to Vsat. This could explain the fact the fall time of the optocouplers TLP124 is not increasing. The delay time, which is the time difference between input signal (at 50% level) and the output signal (at 50% signal) show a continuous increase. The CTR variation as a function of TID has been evaluated too. The initial bias conditions are in Table 2. Although the bias conditions are not the same, the test allows comparing the CTR variation in two cases: a) the output current is kept constant by varying the If (previous section); b) the If is kept constant and the output current varies. TID (Gy) CTR CTR_Norm 0 3.1 1 20 2.8 0.89 40 2.3 0.73 60 1.7 0.55 100 0.91 0.29 150 0.45 0.14 200 0.38 0.12 250 0.21 0.07 Table15:MaximumobserveddegradationoftheTLP124CTRandCTRnormalizedatdifferentTIDmeasuredatIf=
6.1mA.
EDMS number
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The minimum current transfer ratio is 100 % (CTR = 1). The device goes out of specification at a dose lower than 100 Gy. TID (Gy) CTR CTR_Norm 0 1.44 1 20 0.92 0.63 50 0.49 0.34 75 0.32 0.22 100 0.21 0.15 125 0.14 0.1 150 0.11 0.07 Table16:Maximumobserveddegradationofthe4N35CTRandCTRnormalizedatdifferentdosesmeasuredatIf=
6.1mA
It is indicated in the datasheet of the device that the minimum current transfer ratio at If = 6 mA is 100 % (CTR = 1). The device goes out of specification at a dose lower than 20 Gy. The following Table shows the TID value at which the CTR goes out of specification for each case and bias condition: Bias conditions CTR_Min Dose (Gy)
Ie (mA) Initial If (mA) Ie If Bias 1 0.3 Constant Vary Always ON 1 40 10 1.5 Constant Vary Always ON 1 93 Vary 6.1 Vary 1 ≈ 100 fixed‐Pulsed OFF during the irradiation
Table17:SummaryoftheCTR_MinvaluefortheTLP124whentheCTRisoutofthespecifications.
Bias conditions CTR_Min Dose (Gy) Ie (mA) Initial If (mA) Ie If Bias 1 1.3 Constant Vary Always ON 0.5 15 10 8 Constant Vary Always ON 1 10 EDMS number
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Vary 6.1 Vary Pulsed OFF during the irradiation
1 ≈ 20 Table18:SummaryoftheCTR_Minvalueforthe4N35whentheCTRisoutofthespecifications.
Thetwotests(IeconstantandIevary)cannotbedirectlycompared.InthecaseIevary,theLEDcurrent
isnotnullonlyatthemomentofthemeasurement,theIfisconstantandtheIevaries,whereasinthe
testIeconstant(Section5),theLEDwasalwaysON,theIfvariesandtheIewasconstant.Moreover,the
initialbiasconditionsaredifferent.Despitethat,onecannotethatthe4N35isoutofspecificationsat
lowTID(~20Gy).TheTLP124remainswithinthespecificationsuptoabout100GyonlyifahighIfis
considered.
7. SETresults
No Single Event Transients (SET) longer than 15ns and larger than 100mV (minimum values of the SET shape that can be measured with the setup) were triggered for any of the tested components. The following table shows the beam conditions for the SET tests: DUT name Beam energy (MeV) Incidence Final Fluence (p/cm2) 230 Normal 2×1011 60 Grazing 6.4×1010 30 Grazing 4.2×1010 230 Normal 1×1011 60 Normal 4.9×1010 TLP124 4N35 Table19:BeamconditionsfortheSETsensitivityevaluation.
8. SETwithdV/dtresults
No single event transients above 15ns and 100mV (minimum values of the SET shape that can be measured with the setup) were triggered for any of the tested components. The following table shows the beam conditions for the SET tests with dV/dt: DUT name Beam energy (MeV) Incidence Final Fluence (p/cm2) 30 Grazing 3.5×1010 60 Grazing 6×1010 60 Grazing 6.1×1011 230 Grazing 9×1010 TLP124 4N35 Table20:BeamconditionsfortheSETsensitivityevaluationwithdV/dt
EDMS number
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9. Conclusions
During this test campaign, 3 types of optocouplers, TLP124, HCNR, 4N35 have been irradiated by a 230 MeV proton beam. No single event transients above 15ns and 100mV (minimum values of the SET shape that can be measured with the setup) were triggered for any of the tested components. The CTR degradation and the evolution of the response time were evaluated as a function of the TID. The CTR shows a degradation which is quite important for all the three optocoupler references and in particular for the TLP124 and the 4N35. The tests permitted to evaluate the TID at which the CTR is out of the specifications. In particular, the CTR of the TLP124 with an output current of 1 and 10 mA is out of the datasheet specifications at 50 Gy and 100 Gy respectively; the CTR of the 4N35 is out of the datasheet specifications at about 20 Gy regardless the output current. The HCNR optocoupler remains within the specifications up to a TID of 150‐175 Gy. The CTR test was done by considering the real application. The input current is always ON and varies to compensate the output current decreasing. Thus, annealing effects are induced, which should reduce the radiation effects according to the literature. The test of the response time for the TLP124 and the 4N35 allowed measuring the CTR with the device OFF during the irradiation. Although the conditions during the 2 tests are not comparable, the CTR degradation has been confirmed by irradiating the devices in two different modes: (a) at constant Ie with a continuous If current and (b) at a constant If with the device OFF during the irradiation. The Total Ionizing Dose was delivered at a dose rate of about 300 Gy/h. The dose rate in the LHC tunnel is much lower than the one at which the test was done. Therefore, should the devices be sensitive to the ELDR (Enhanced Low Dose Rate) effects, the degradation could be worse. Thus, a margin factor 2‐3 should be considered. However, the degradation is also due to Displacement Damage. The results are not directly comparable with Co60 irradiation test. Proton beam at 230 MeV represents a more severe test. For the response time test, it is difficult to evaluate the degradation of the time response. The CTR degradation is very sharp; having fixed the If, the Ie decreases, and the output signal is not a proper square ranging from Vcc to the saturation voltage of the phototransistor. The falling time of the optocoupler outputs, and the turn‐on time have been evaluated. The falling time is not increasing monotonically, whereas the turn‐on time does. The turn‐on time shows a light degradation but remains within the specifications up to the total fluence/TID that the DUTs received. Finally, destructive events have not been registered.