Living with a Star Space Experiment Testbeds · Space Experiment Testbeds Calibration of RADFET Dosimeters for SET-1 Part I: Co-60 Gamma Rays Michael Xapsos, Robert F. Stone, Kenneth

Calibration of RADFET Dosimeters for SET-1 Part I: Co-60 Gamma Rays G07APR_RADFET 462-RPT-XXXX Page 1 of 14

CHECK THE GSFC CONFIGURATION MANAGEMENT SYSTEM AT http://gdms.gsfc.nasa.gov to verify the latest version prior to use.

Living with a Star Space Experiment Testbeds

Calibration of RADFET Dosimeters for SET-1 Part I: Co-60 Gamma

Rays

Michael Xapsos, Robert F. Stone, Kenneth LaBel, Kenneth Li NASA Goddard Space Flight Center, Code 561, Greenbelt, MD

20771 Craig Stauffer, John Hoge, Susan Ritter and Scott Kniffin

Muniz Engineering, Inc., Seabrook, MD 20706

462-RPT-XXXX

REVISION -

ASSEMBLY REVISION ____________ ASSEMBLY SERIAL # ____________ Date Started ____________ Date Completed ____________

EFFECTIVE DATE: XX/XX/2007 EXPIRATION DATE: XX/XX/2012



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SIGNATURE PAGE

Prepared by: ________________________________ Date: ________________ Michael Xapsos, GSFC – Code 561 SET Project Scientist Approved by: Date: ________________

Chuck Naegeli, GSFC – Code 462 SET Project Manager

Approved by: Date: ______________

Ken LaBel, GSFC - Code 561 SET Project Technologist


Carolyn Mariano, GSFC – Code 462 SET Experiment Manager/Risk Management

Approved by: Date: ______________ Scott Appelbaum, Qwaltec - Code 462 SET Mission Ops/Project Support


Anne Koslosky, GSFC – Code 582 SET FSW Systems Engineer



This is a LWS SET Project Office Controlled Document. This document has been developed to report the results on an experiment that will be used on the SET carrier. Any revision to this basic plan after document CM release requires approval from the SET Project Office through the configuration control process.

REVISION HISTORY LOG

Rev Description/Sections Affected Approved: Document Effective

Date: - Released per CCR# 462-XX



Table of Contents 1 INTRODUCTION............................................................................................................................. 6

1.1 SCOPE ................................................................................ ERROR! BOOKMARK NOT DEFINED. 1.2 LIST OF ACRONYMS/ABBREVIATIONS/DEFINITIONS .................................................... 6 1.3 THEORY OF OPERATIONS.............................................. ERROR! BOOKMARK NOT DEFINED. 1.4 REFERENCES ........................................................................................................................... 6

1.4.1 Documents........................................................................................................................... 6 1.4.2 Drawings............................................................................................................................. 6

2 TEST REQUIREMENTS ............................................... ERROR! BOOKMARK NOT DEFINED.

2.1 SAFETY REQUIREMENTS ...................................................... ERROR! BOOKMARK NOT DEFINED. 2.2 DEFINITION OF FAILURE....................................................... ERROR! BOOKMARK NOT DEFINED. 2.3 REJECTION AND RE-TEST ..................................................... ERROR! BOOKMARK NOT DEFINED. 2.4 TEST RESPONSIBILITY.......................................................... ERROR! BOOKMARK NOT DEFINED. 2.5 TEST ORDER ........................................................................ ERROR! BOOKMARK NOT DEFINED. 2.6 ATMOSPHERIC CONDITIONS ................................................. ERROR! BOOKMARK NOT DEFINED. 2.7 QUALITY ASSURANCE.......................................................... ERROR! BOOKMARK NOT DEFINED. 2.8 PROCEDURAL CHANGES....................................................... ERROR! BOOKMARK NOT DEFINED. 2.9 TEST RECORDS .................................................................... ERROR! BOOKMARK NOT DEFINED. 2.10 ESD REQUIREMENTS ........................................................... ERROR! BOOKMARK NOT DEFINED. 2.11 HANDLING AND CLEANLINESS ............................................. ERROR! BOOKMARK NOT DEFINED.

3 TEST EQUIPMENT........................................................ ERROR! BOOKMARK NOT DEFINED.

3.1 EQUIPMENT LIST.................................................................. ERROR! BOOKMARK NOT DEFINED. 3.2 EQUIPMENT CALIBRATION ................................................... ERROR! BOOKMARK NOT DEFINED.

4 SYSTEM CONFIGURATION ....................................... ERROR! BOOKMARK NOT DEFINED.

4.1 GROUNDING......................................................................... ERROR! BOOKMARK NOT DEFINED. 4.2 BLOCK DIAGRAM................................................................. ERROR! BOOKMARK NOT DEFINED. 4.3 SETUP VERIFICATION ........................................................... ERROR! BOOKMARK NOT DEFINED.

5 TEST PROCEDURE....................................................... ERROR! BOOKMARK NOT DEFINED.

5.1 BACKPLANE CONTINUITY CHECKS .......................... ERROR! BOOKMARK NOT DEFINED. 5.2 BACKPLANE ISOLATION CHECKS ............................. ERROR! BOOKMARK NOT DEFINED. 5.3 CST CIRCUIT VERIFICATION ............................................... ERROR! BOOKMARK NOT DEFINED.

5.3.1 Resistance Checks................................................................Error! Bookmark not defined. 5.3.2 Zener Diode Checks.............................................................Error! Bookmark not defined.

6 TEST COMPLETION..................................................... ERROR! BOOKMARK NOT DEFINED.



1 INTRODUCTION This work dealt with calibration of RADFET dosimeter die manufactured by Tyndall, formerly known as National Microelectronics Research Center (NMRC), using Co-60 gamma rays. The dosimeter circuitry that was designed for this application was also evaluated for total ionizing dose tolerance. The dosimeters will be used to complement experiments flown on the Living With a Star (LWS) Space Environment Testbed-1 (SET-1) carrier. This is part of the payload for AFRL’s Demonstration and Science Experiments (DSX) mission, scheduled for launch in 2009. The purpose of this testing is two-fold:

1. Evaluate the circuitry used to read out the dosimeters for total ionizing dose tolerance. It is required to operate up to a dose of 100 krad(Si).

2. Calibrate the dosimeters at room temperature when the circuitry is both with and without power. Assess limitations that may occur due to lack of power for SET-1 during the mission.

1.1 LIST of ACRONYMS/ABBREVIATIONS/DEFINITIONS HSS Host Spacecraft Simulator Hz Hertz I&T Integration and Test I/F Interface I/O Input/Output ICD Interface Control

Document/Diagram IVP Integrated Verification Plan LAN Local Area Network LED Light Emitting Diode LWS Living with a Star MBPS Megabit per Second MIL-STD Military Standard MM Mission Manager NASA National Aeronautics and Space

Administration PR/PFR Problem Report/Problem Failure

Report

PI Principal Investigator POCC Payload Operations and Control

Center PWA Printed wiring assembly PWB Printed wiring board QA Quality Assurance S/C Spacecraft SCH Schematic S/W Software T&E Test and Evaluation TBD To Be Determined TC Test Conductor TCT Test Conductor Terminal TLM Telemetry UGSE Umbilical Ground Support

Equipment WOA Work Order Authorization

1.2 REFERENCES

1.2.1 Documents [1] Robert F. Stone, SET Dosimeter Radiation Test Procedure, 462-PROC-0076, NASA Goddard Space

Flight Center, Greenbelt, MD.

SET-1 Backplane Assembly #2087725 Safe to Mate Test Procedure LWSSET-PROC-0062 Revision (-) Page 7 of 14


2 TESTING

2.1 Test Devices The RADFET dosimeter die was manufactured by Tyndall/NMRC in Cork, Ireland and custom packaged by Chip Supply in Orlando, FL. RADFET die consists of 4 P-channel MOSFETs packaged in a 14-pin flat pack. Radiation test samples are marked as SR-ESAPMOS4/RAD, and are from the same lot as the flight devices, p/n SR-ESAPMOS4. Both radiation test samples and flight devices are from lot date code 0608, with die selected from Tyndall/NMRC wafer #2. The die MOSFET chosen for use on SET-1 has a channel width of 300 micrometers, channel length of 50 micrometers and gate oxide thickness of 400 nanometers. The pin numbers corresponding to the device terminals are: 1 – bulk substrate connection (common) 2 – drain for RADFET #1 3 – gate for RADFET #1 4 – source for RADFET #1

2.2 Test Procedure A test set-up consisted of 8 dosimeter cards, with each card containing a single RADFET device and associated SET-1 circuitry. The circuitry allowed RADFETs to be irradiated with all pins on a die grounded. The voltage of the drain and gate, which were tied together, relative to the source and substrate, which were grounded, was taken as the threshold voltage when a channel current of 13 microamperes flowed. The set-up could be remotely powered on or off to simulate the corresponding situations in the SET-1 carrier. After each incremental irradiation, the dosimeter cards were removed from the test facility and the RADFET threshold voltages measured as a function of dose. A detailed description of the testing procedure is given in [1].

2.3 Irradiations Three set-ups containing 8 dosimeter cards each were irradiated at a dose rate of 0.1 rad(Si)/sec using the low intensity Co-60 source at NASA Goddard Space Flight Center. The first set-up was powered on at all times during irradiation. The second set-up was powered on during most irradiations but was powered off during several irradiations to simulate the possibility that the SET-1 carrier would not have power at times. The third set-up was powered off at all times during irradiation. In addition there were 2 cards with dosimeters that were used as control samples. Table 1 gives the irradiation details, including whether the second set-up was powered on or off during irradiation.



Table 1. Co-60 Irradiation Details for LWS SET-1 RADFET Tests

These irradiations were followed by a 1-week room temperature annealing period while all RADFET pins were grounded.

3 ANALYSIS AND RESULTS As long as power was applied to the circuitry during irradiation, the dosimeters and circuitry remained fully functional to doses of about 116 krad(Si) and after the 1-week room temperature anneal. However, difficulties were encountered when the dosimeters were irradiated without power applied. These results are described below followed by recommendations for use on SET-1 and for further testing. Threshold voltages were read out as a digitized value, N, ranging from 0 to 4095. The conversion to a voltage value is given by

5.40910

NVt −= (1)

where Vt is the threshold voltage in units of volts. Figure 1 shows threshold voltage shifts of the 8 RADFETs in setup 1 as a function of dose. This setup always had power during irradiation. The response of one of the dosimeters was well outside of the other 7 and was not considered in the subsequent calibration analysis.

Run#

Date / TimeIn

Date / TimeOut

# HoursIn Co-60Chamber

# DaysIn Co-60Chamber

DoseReceived(krad-Si)

AccumulatedDose

(krad-Si)

AverageDose Rate(Rad-Si/s)

Comments

1 4/16/07 2:55 PM 4/17/07 7:00 AM 16.08 0.670 5.5 5.5 0.09 Setup2 Power Off2 4/17/07 7:33 AM 4/17/07 3:30 PM 7.95 0.331 2.9 8.4 0.10 Setup2 Power On3 4/17/07 3:52 PM 4/18/07 7:00 AM 15.13 0.631 5.3 13.7 0.10 Setup2 Power On4 4/18/07 7:30 AM 4/18/07 3:30 PM 8.00 0.333 2.9 16.6 0.10 Setup2 Power On5 4/18/07 3:44 PM 4/19/07 7:00 AM 15.27 0.636 5.4 22 0.10 Setup2 Power On6 4/19/07 7:30 AM 4/19/07 3:24 PM 7.90 0.329 2.9 24.9 0.10 Setup2 Power Off7 4/19/07 3:35 PM 4/20/07 7:10 AM 15.58 0.649 5.8 30.7 0.10 Setup2 Power On8 4/20/07 7:30 AM 4/20/07 3:30 PM 8.00 0.333 2.9 33.6 0.10 Setup2 Power On9 4/20/07 4:10 PM 4/23/07 7:00 AM 62.83 2.618 22.8 56.4 0.10 Setup2 Power On

10 4/23/07 7:50 AM 4/24/07 7:00 AM 23.17 0.965 8.4 64.8 0.10 Setup2 Power On11 4/24/07 7:50 AM 4/25/07 7:00 AM 23.17 0.965 8.5 73.3 0.10 Setup2 Power On12 4/25/07 7:50 AM 4/26/07 9:15 AM 25.42 1.059 9.1 82.4 0.10 Setup2 Power Off13 4/26/07 10:05 AM 4/27/07 3:30 PM 29.42 1.226 10.5 92.9 0.10 Setup2 Power On14 4/27/07 3:50 PM 4/30/07 7:30 AM 63.67 2.653 23 115.9 0.10 Setup2 Power On

Totals 321.58 13.40 115.9



0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90 100 110 120Dose (krad-Si)

Thre

shol

d V

olta

ge S

hift

(Vol

ts)

Figure 1. Threshold voltage shifts for the 8 RADFETs in setup 1 as a function of Co-60 gamma ray dose. This setup was always powered on during irradiation. The points in Figure 2 are the average threshold voltage shifts of the 7 similar measurement results shown in Figure 1. The error bars represent plus and minus one standard deviation. The RADFET dose calibration is given by

bt aDV =∆ (2)

where ∆Vt is the radiation-induced change in threshold voltage, D is the dose, and a and b are fitting parameters. The units used in this equation are volts for threshold voltage change and rad(Si) for dose. The best fit of the data to equation (2) is shown by the line in Figure 2. The corresponding parameters are shown in Table 2. This gives the calibration of the RADFET dosimeters when the circuitry is powered on.



0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90 100 110 120Dose (krad-Si)

Thre

shol

d V

olta

ge S

hift

(Vol

ts)

Figure 2. Dose calibration of RADFET dosimeters when the circuitry is powered on (line) compared to the average threshold voltage shifts of 7 dosimeters. Error bars represent plus and minus one standard deviation.

Table 2. Calibration Parameters for RADFET Dosimeters

Figure 3 shows threshold voltage shifts of the 8 RADFETs in setup 3 as a function of dose. This setup always had power off during irradiation. All 8 RADFETs failed to function beyond a dose of 33.6 krad(Si). This indicates that the circuitry should not be without power for an extended time during the mission. Figure 4 shows the averaged data, its uncertainty and corresponding best-fit line to equation (2). The fitted parameters a and b are shown in Table 2. This gives the calibration of the dosimeters when the circuitry is powered off.

3.1.1.1 Condition: a: b:

Power On 0.01747 0.5072 Power Off 0.005893 0.6470



0

1

2

3

4

5

6

0 10 20 30 40Dose (krad-Si)

Thr

esho

ld V

olta

ge S

hift

(Vo

lts)

Figure 3. Threshold voltage shifts for the 8 RADFETs in setup 3 as a function of Co-60 gamma ray dose. This setup was always powered off during irradiation. The dosimeters failed to function beyond the doses shown.



0

1

2

3

4

5

6

0 10 20 30 40Dose (krad-Si)

Thre

shol

d V

olta

ge S

hift

(Vol

ts)

Figure 4. Dose calibration of RADFET dosimeters when the circuitry is powered off (line) compared to the average threshold voltage shifts of 8 dosimeters. Error bars represent plus and minus one standard deviation. Figure 5 shows threshold voltage shifts of the 8 RADFETs in setup 2 as a function of dose. This setup had power on during most irradiations but was powered off during the 3 irradiations shown in Table 1. Seven of the 8 RADFETs failed to function beyond a dose of 73.3 krad(Si). In addition, the RADFET operation for this situation appeared to be more erratic, i.e., there was a larger spread in the dosimeter responses. The purpose of switching the power on and off for this set-up was to see how well the threshold voltage shift could be predicted as a function of dose using the calibrations from the other two set-ups. Figure 6 shows the data and its uncertainty compared to the prediction, which is shown by the green line. The prediction is systematically lower than the average values. However it is nonetheless within the data uncertainty, indicating that reasonable predictions can be made as long as the circuitry is not without power for too long a time period during irradiation.



0

1

2

3

4

5

6

7

8

0 10 20 30 40 50 60 70 80 90 100 110 120Dose (krad-Si)

Thre

shol

d V

olta

ge S

hift

(Vol

ts)

Figure 5. Threshold voltage shifts for the 8 RADFETs in setup 2 as a function of Co-60 gamma ray dose. This setup was powered on or off during irradiation as shown in Table 1. Seven of the 8 dosimeters failed to function beyond a dose of 73.3 krad(Si).



0

1

2

3

4

5

6

0 10 20 30 40 50 60 70 80Dose (krad-Si)

Th

resh

old

Vo

ltag

e S

hift

(Vo

lts)

Figure 6. Predicted dosimeter response using the calibrations given in Table 2 (green line) compared to measurements for setup 2. Error bars represent plus and minus one standard deviation. The 1-week room temperature anneal following irradiation showed a minimal change in threshold voltage (~ 7% for set-up 1 while powered), indicating that the dosimetry uncertainty due to annealing during a 1-year mission should be small.

4 RECOMMENDATIONS Due to the increased dosimetry uncertainty and potential dosimetry failure when the circuitry is powered off during irradiation, it is recommended that the SET-1 carrier be unpowered for no more than 1 month after launch and no more than a total of 1.5 months during the entire mission. This should keep the total dose to less than 10 krad(Si) during the mission time period when the circuitry is without power. It is also recommended that further ground testing be done. Additional Co-60 gamma ray tests would be useful to acquire better calibration statistics. The trapped proton radiation environment for the SET-1 experiments is significant. Therefore, proton testing is recommended to measure the dosimeter response to protons. Finally, the RADFET threshold voltage is known to be dependent on temperature. It is therefore recommended that dosimeter threshold voltages be characterized over the range of temperatures expected for the SET-1 experiments