Radiation effects and experience with mitigation
measures
2015 Finemet Project Review
M. Paoluzzi
September 14th - 2015
Will the solid state amplifiers survive
radiation?
1.
2.
3.
4.
Expected behavior and mitigation measures
Doses measured in the PSB and PS
Amplifier in PS SS2
Conclusion
M. Paoluzzi
September 14th - 2015
Expected behavior and mitigation measures
Results from previous tests in J-PARC and at Fraunhofer Institute:
Modern L-type and old V-type devices tested
All devices have similar behavior: IDrain vs VGate characteristic shift
All devices survive kGy doses
MRFE6300 (L-Type) shows the lowest Vth change.
All devices have similar behavior and require compensation measures already with few tens of Gy.
VRF151 was retained because of superior drain breakdown voltage.
M. Paoluzzi
September 14th - 2015
Expected behavior and mitigation measures
•
•
Radiation effects-compensation circuit has been introduced.
Some improvement is obtained but this improvement may vary between
amplifiers because the threshold voltage shift for a given dose varies
between RF power MOS.
M. Paoluzzi
September 14th - 2015
Pre-irradiation and RF MOSFETs selection
• Pre-irradiation of the devices at a low dose level (≈100Gy) would identify
individual threshold voltage shift and allow device selection.
• Use of selected devices to improve radiation effects compensation results.
M. Paoluzzi
September 14th - 2015
Doses measured in the PS SS2
• Dose outside shielding in line with expectation.
• Shielding efficiency higher than expected (50 vs 10).
• Possible wall reduction from 10cm to 5cm for easier opening of side walls.
Measured radiation doses in PS SS2
90
80
2.5E+19
70
Outside Shielding
DOSE [GY]
60
2.0E+19
50
1.5E+19
Integrated Protons
40
30
1.0E+19
Ratio ≈ 50
20
5.0E+18
10
Inside Shielding
0
0.0E+00
16/09/2015
19/08/2015
22/07/2015
24/06/2015
27/05/2015
29/04/2015
01/04/2015
M. Paoluzzi
September 14th - 2015
INTEGRATED NUMBER OF PROTONS
3.0E+19
Doses measured in the PSB
• RadMon in 13L1 not working but RF mosfets • Dose in 6L1 lower than expected
installed for decades without radiation
(change due to machine realignment).
issues.
• Expected dose for testing the radiation
• Dose in 10L1 in line with expectations.
effects compensation not high enough.
• Dose in 7L1 lower than expected (probably
due to machine realignment).
10
5.0E+19
8
4.0E+19
Section 10L1
DOSE [GY]
6
Integrated Protons
4
2.0E+19
Section 6L1
2
1.0E+19
Section 7L1
0
0.0E+00
-2
-1.0E+19
16/09/2015
19/08/2015
22/07/2015
24/06/2015
27/05/2015
29/04/2015
01/04/2015
M. Paoluzzi
September 14th - 2015
3.0E+19
INTEGRATED NUMBER OF PROTONS
Measured radiation doses in PSB
Amplifier in PS SS2
•
•
•
One amplifier installed in PS SS2 outside the shielding. Operated in
continuous ON conditions.
During all the test no single events or other destructive process occurred.
Effect of position with respect to the beam line clearly visible:
• RF Mosfets closer to the beam line under compensated.
• Other RF Mosfets correctly or slightly over compensated.
• Device sensitivity to radiation seems equivalent among the devices.
Compensated MOS Currents vs Radiation
16 Mos Current Evolution
2.5
I [A]
MOS5
MOS4
MOS6
MOS3
MOS7
MOS2
MOS8
MOS1
I [A]
2.5
40Gy
2.0
2.0
30 Gy
DRIVER
1.5
1.0
20 Gy
MOS9
MOS16
MOS10
MOS15
MOS11
MOS14
MOS12
MOS13
1.5
10 Gy
1.0
0 Gy
0.5
0.5
0.0
0
0.0
0
M. Paoluzzi
September 14th - 2015
10
20
30
40
50
Dose [Gy]
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 MOS #
Conclusion
•
PS Damper
•
•
•
Radiation doses for the PS Damper inside the shielding evaluated to
≈5Gy/year.
With present design 5-10 years of operation seem possible before
bias readjustment will be required.
PSB
•
•
Radiation doses in 13L1 and 7L1 expected to be few Gy/year.
• With present design 5-10 years of operation before bias
readjustment will be required.
Radiation doses in 10L1 expected to be ≈20Gy/year.
• With present design 2-3 years of operation before bias
readjustment will be required.
• Moderate shielding (3 cm of steal) of amplifier side exposed to
the beam line might be required to achieve 5-10 years.
M. Paoluzzi
September 14th - 2015