Measurements of US stave using ESPI and capacitive sensors

30th August 2012

• 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)

US stave mounted in environmental chamber.

Invar panelCapacitive sensors

Cooling pipes

Markers showing positions of mounting brackets

End mount brackets

Isotropic View of the US stave on the Invar Panel

US stave

US Brackets

Fully Fixed Mounting fixture

2 Dimensional Fixed Mounting Fixture

End View

Fully Fixed Mounting2 Dimensional Fixed Mounting

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

Fixed point at x, y and z planes Fixed point at 2 planes

Constraint –ve X and Z planes

Constraint +ve X plane only

Vibrational modes (60 Hz)

Position of central bracket

Measurements of vibrational modes using ESPI (Room temperature)

Vibrational modes (119Hz)

Position of central bracket

Position of central bracket

Vibrational modes (185 Hz)

Cool down test measurements in Z direction using capacitive sensors

Schematic of US stave showing locations of capacitive sensors

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)

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.

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.

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

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

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)

Provisional Conclusions

1. Normal modes don’t exhibit nodes at bracket locations.

2. Stave movement highly dependent on end supports.