Irradiation Test of Optical Fibers
1. Goal
The goal of this test is to measure how gamma ray affects the optical fibers.
2. Test setup and process
Fig. 1 The test setup
The test process is summarized in Table 1.
Table 1. The irradiation test process
Run
#
1
2
3
Start time
4/10/08
12:42:49
PM
4/10/08
5:47:58
PM
4/11/08
5:52:14
PM
End time
4/10/08
5:08 PM
4/11/08
5:07:19
PM
4/12/08
12:57:10
PM
Time
(hr)
accumulated
time (hr)
Dose
rate
(krad/hr)
TID
(krad)
accumulated
TID (krad)
4:26:00
4:26:00
30
133
133
23:20:00
27:46:00
30
700
833
19:05:00
46:51:00
30
573
1405
Fibers manufacturer: Corning® Infinicor SX+ 50/125 Micron Optical Multimode 3
(OM3) Fiber
Fiber vendor: 10GB Aqua Fiber Cable - Duplex 50/125 LC/LC 2M Item# FDQ5LL-2
An optical transmitter made in Taiwan and used in the ATLAS liquid argon calorimeter
is used to generate a constant power. A 50-50 power splitter is used to split the power
into two fibers, one under test in the gamma radiation and the other shielded from the
gamma radiation. An optical power meter HP8163 is used to measure the optical power.
The fiber length under irradiation is 45 meters. Fig. 1 is a picture of the test setup.
3. Test results
Fig. 2 The optical power change as a function of irradiation time
Table 2. The optical power change
Run
#
1
2
3
Dose
(krad)
133.00
700.00
573.00
Accumulated
dose (krad)
133.00
833.00
1405.00
Delta P1
(dB)
-1.05
-0.79
-0.07
Accumulated
Delta P1
(dB)
-1.05
-1.84
-1.91
Delta P2
(dB)
-0.10
0.01
0.00
Accumulated
Delta P2
(dB)
-0.10
-0.09
-0.09
Fig. 2 is the optical power change as the function of irradiation time. The straight vertical
lines indicate the start and end of beam time (the start time of the first run is time zero).
The results are summarized in Table 2 (P1 and P2 are the optical powers of the fiber
under test and the reference fiber, respectively). Most of the data during the first run were
lost due to a broken instrument. The power change in the first run is estimated from the
power before the radiation starts and the end power (manually recorded, not shown in Fig.
2) during the pause between the first and the second run. During the pause between the
second run and the third run, the fibers were moved to take away some instruments for
other tests. This fiber movement may cause the rapid power change in both the fiber
under test and the reference fiber.
The power decreases 1.91 dB in total runs, including part of anneal in the beam pause
between the first run and the second run and not including the annealing in the beam
pauses during the second run and the third run. This gives the worst power change of the
attenuation rate of 42 dB/km at the TID 1.405 Mrad. A saturation trend can be seen in the
second run and the third run. The annealing process between two continuous runs is also
apparent.
The temperature and humidity monitoring in the
irradiation Test
1. Goal
The goal of this test is to see if the temperature and humidity change in the irradiation test.
2. Test setup and process
We use LabJack U12 data acquisition unit with LabJack EI-1050 temperature and
humidity probe. The temperature accuracy is specified as 0.9 C from 0 to 40 C. The
humidity accuracy is +/- 3.5%. The data acquisition unit and the probe are put in the leadbrick room in the radiation room. Fig. 1 is a picture of the setup.
Fig. 1 The test setup
Table 1. The irradiation test process
Run #
1
2
3
beginning time
4/10/08 12:42 PM
4/10/08 5:47 PM
4/11/08 5:52 PM
end time
4/10/08 5:08 PM
4/11/08 5:07 PM
4/12/08 12:57 PM
Time (hr)
4:26:00
23:20:00
19:05:00
3. Test results
Fig. 1 The temperature and humidity change during the irradiation test
Fig. 1 shows the temperature and humidity change during the irradiation test. During the
first and the second runs, the temperature increase from 21 C to 29 C and the humidity
decrease from 42.7% to 21.4%. Later it was found that the shielding room was small and
crowded. The heat generated by the instruments may be the major reason of the
temperature and humidity change. During the third run, the temperature decreases from
23.4 C to 22.9 C and the humidity increases from 30% to 37%.
During the third run, the temperature outside the room changed from 10 C to 20 C, but
the room temperature changed less than 1 C. The humidity changed little compared to the
humidity outside the room (before a thunder storm), indicating the temperature and
humidity is quite stable inside the room.