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Measurements of US stave using ESPI and capacitive sensors
30th August 2012
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• Three main tests carried out:
1. Vibrational modes (ESPI)2. Cool down measurements Z direction (Capacitive sensors)3. Cool down measurements X direction (Capacitive sensors)
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US stave mounted in environmental chamber.
Invar panelCapacitive sensors
Cooling pipes
Markers showing positions of mounting brackets
End mount brackets
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Isotropic View of the US stave on the Invar Panel
US stave
US Brackets
Fully Fixed Mounting fixture
2 Dimensional Fixed Mounting Fixture
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End View
Fully Fixed Mounting2 Dimensional Fixed Mounting
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Fixed in 2 planes
L-Spacer
V groove spacer
The idea of constraining the 2nd fixed point which constrain in x and z directions only
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Fixed point at x, y and z planes Fixed point at 2 planes
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Constraint –ve X and Z planes
Constraint +ve X plane only
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Vibrational modes (60 Hz)
Position of central bracket
Measurements of vibrational modes using ESPI (Room temperature)
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Vibrational modes (119Hz)
Position of central bracket
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Position of central bracket
Vibrational modes (185 Hz)
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Cool down test measurements in Z direction using capacitive sensors
Schematic of US stave showing locations of capacitive sensors
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0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100105110115120125130135
-20.0
0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
160.0
180.0
200.0
Graph of Z plane data 20/8/2012 Sensor positions G,H and I
Sensor GSensor HSensor I
Time (Minutes)
Dist
ance
Mov
ed (u
m)
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Conclusion: In the Z direction during cool down the whole stave is moving away from the sensors and it is also tilting more along the top edge. It is tending to tilt more along the right hand side than the left hand side.
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In order to counteract the movement of the right hand side of the stave in Z direction, blocks were used to minimise the amount of movement allowed, free movement in X direction maintained.
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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210
-40.0-30.0-20.0-10.0
0.010.020.030.040.050.060.070.080.090.0
100.0110.0120.0130.0140.0150.0160.0170.0180.0
Cool down test US stave 22 Aug 2012 (Right hand side of stave restricted in Z direction movement)
Sensor 1
Sensor 2
Sensor 3
Sensor 4
Sensor 5
Sensor 6
Time (Minutes)
Dis
tanc
e m
oved
(um
)
Sensor 1 = ASensor 2 = CSensor 3 = DSensor 4 = FSensor 5 = GSensor 6 = I
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Schematic diagram of US stave showing capacitive sensor positions for x plane movement.
Bracket
Cooling pipe
Capacitive sensor
Sensor XSensor YSensor Z
Cool down test measurements in X direction using capacitive sensors
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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
-250.0-240.0-230.0-220.0-210.0-200.0-190.0-180.0-170.0-160.0-150.0-140.0-130.0-120.0-110.0-100.0
-90.0-80.0-70.0-60.0-50.0-40.0-30.0-20.0-10.0
0.010.020.030.0
Cool down test US stave 28 Aug 2012. X direction movement.
Sensor XSensor YSensor Z
Time (Minutes)
Dist
ance
mov
ed (u
m)
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Provisional Conclusions
1. Normal modes don’t exhibit nodes at bracket locations.
2. Stave movement highly dependent on end supports.