1. CALIFES 2015 run preliminary results
Maris Tali (University of Jyväskylä)
Rubén García Alía
Matteo Brucoli
Wilfrid Farabolini
Salvatore Danzeca

2. Introduction – JUICE mission (ESA)
JUpiter ICy moons Explorer - planned for launch in 2022, expected to reach Jupiter by 2030
Scientific mission at Callisto and Ganymede 3.5 years
The radiation environment is dominated by the bound electrons in the Jupiter magnetosphere
The electron spectrum also has a high energy component, which extends to higher energies than the spectrum in geostationary orbit
JUICE Red Book, ESA (2014)
J. M. Trippe et al. (2015)

3. Introduction – Radiation Damage
Single Event Effects (SEEs) are caused by a single, energetic particle
Single Event Upsets (SEUs) are soft errors, and non-destructive, example a bit-flip in a memory
The rate of which these upsets occur is described with a cross-section
In addition to this the cumulative effects of radiation (TID) cause damage over time and lead to degradation of performance and failures
Due to the dominant electron component in the Jovian atmosphere the electron effect on components needs to be evaluated
E. Noordeh (2014)

4. Gold foil activation setup
Foil center
Beam center
Gold foil activation setup
Goal -> measure the electron intensity at the DUT position as no dedicated dosimetry system was installed
Dark current beam, 0.21nC, total time 3h
Beam position was confirmed with gafchrom film, beam center off 0.5 cm on x-axis and 1 cm on y-axis
Electron beam produces photons in copper which activate gold foils
Au197(gamma, n) -> Au196, well benchmarked in FLUKA due to detailed available reaction measurement data, good results were obtained with a similar experiment in Pohang with 2.5 GeV electrons (M. Brugger et al. (2011))
The gamma spectroscopy was performed 7 days after irradiation with a Germanium gamma detector

5. Gold foil activation results
Measurement results:
Activity (kBq)
Error (kBq)
1.030
0.044
2.270
0.096
3.210
0.136
FLUKA results:
Activity (kBq)
Error (kBq)
9.897
0.084
10.938
0.097
11.628
0.079

6. Gold foil activation conclusion
The difference between the measured gold foil activation and the FLUKA simulated activation is a factor 3.4
The probable reasons for this are the beam misalignment, also some losses along the beamline due to physical objects in the beamline (instrumentation)
Losses are expected to vary significantly with operation conditions, therefore it is essential to have a dosimetry system at the test location

7. RadFET measurements setup
RadFETs set up upstream of BTV, shifted 1 cm from the centre of BTV, which is not necessarily the center of the beam
Beam in dark current setting (0.34 nC)
0.8 Hz – 23rd November – total time 28h
5 Hz – 16th of November – total time 11h

8. RadFet measurements results (Matteo Brucoli)
For the 5Hz – 58 Gy/h was measured
For 0.8 Hz – 9.8 Gy/h
Theoretical difference in dose corresponds to the measured difference in dose rate
Both measurement show very good linearity with time

9. RadFet measurement conclusion
Theoretical difference in dose corresponds to the measured difference in dose rate
Both measurement show very good linearity with time
Due to the small beam size, the beam gradient is very high. Therefore, dose depends strongly on the exact position of the RadFETs
FLUKA simulation of dose in SiO2 for the 5 Hz case demonstrates the high gradient of the beam, hundreds of times difference in a few cm

10. ESA SEU Monitor tests and setup
ESA Monitor downstream BTV screen, aligned with its center “by eye”
Optimized dark current settings 9th – 10th November 16 h (beam current ~0.31nC per train)
Weak laser pulse 9th November (~0.16nC)
Dark current 13th – 16th November (~0.28nC)

11. ESA Monitor results (R. García)
Die 0
Die 1
Die 2
Die 3 9
142 2 70
Die 0
Die 1
Die 2
Die 3 53 63
105
309
Die 0
Die 1
Die 2
Die 3
436
787
762 x
Optimized dark current settings
0.31nC
Dark current
0.28nC
Weak laser pulse
0.16nC
Conclusion of the tests are that
- electrons are capable of inducing SEUs even in technology with a relatively high critical charge compared to modern technology
- dark current setting seems promising for radiation testing of electronics, given that the beam is homogenous
- currently the beam is not homogenous over one die, when the beam is homogenous a cross section can be calculated
During all of the runs single event effects were observed
The dark current mode looks most promising for irradiation campaigns, especially with improved beam homogeneity 1 3 2

12. ESA Monitor results conclusions
Electrons are capable of inducing SEUs even in technology with a relatively high critical charge compared to modern technology
For the optimized dark current run, the cross section could be calculated and corresponds for 309 SEUs and 4 Mbit a cross section of 1.6e-18 cm2/bit (with large uncertainty!)
This cross section is 5 orders of magnitude smaller than the proton cross section and about 4 times smaller than simulated value
Dark current setting seems promising for radiation testing of electronics, given that the beam is more homogenous
Current analysis is still preliminary and a more detailed cross section derivation will require further analysis/measurements

13. Future work
Increased beam size at DUT position, provide a homogenous beam for a standard chip sensitive area (2 x 2 cm), this would mean a FWHM of about 5 x 5 cm
Beam instrumentation at DUT position to monitor beam flux during irradiation
Extend SEE measurements to a broader set of components and energies
Possibility of moving experiments in and out of beam remotely
ESA is interested, after beam improvements, in conducting SEE/TID tests at the CALIFES facility

14. Extra slides