SQXF Mirror QXFSM1 Strain Gauges R. Bossert, G Chlachdize, S. Stoynev

Outline Strain gauge types and positions Values during construction Prior analysis of coil cross section Strain gauges during testing Azimuthal coil full bridge Axial coil full bridge End preload “bullets” Gauges bonded directly to coil Summary

SQXF Mirror Strain Gauge Positions Bolt on skin Coil Protective Shell Coil Midplane shim Yoke (EDM’d blocks) Aluminum Side Clamp Full bridges on titanium *Note: T stands for “transition” side and NT stands for “non-transition” side. The transition side is the side in which the cable transitions from the inner to the outer layer. Coil Midplane Gauges (side designated as T or NT)* Coil Pole Gauges (side designated as T or NT)*

Strain Gauges Strain gauge system, standard for short mirror: 1 set of full bridges on inner titanium pole, one azimuthal bridge, one longitudinal bridge. 4 quarter bridges bonded to inside surface of inner coil, used during construction only. Gauges bonded to coil

Strain Gauges Strain gauges bonded to end preload bolts. Array of gauges on skin at 60 and 90 degrees from midplane (HQ shell shown). Strain gauges bonded to end preload bolts.

Side View Bolt-on skin is 2 meters long, while coil is 1.6 meters long. Coil is placed with Lead End at one end of structure, allowing leads to be terminated in a conventional way. Remainder of structure to be filled with filler packs. End Load Similar to HQ mirrors. 2 preload bolts on each end, each applying 7 kN (1500 pounds) of force from the 50mm thick end plate, for a total of 14 kN (3000 pounds) at each end.

Assembly Steps – Planned and Actual Press to 80 Mpa azimuthal stress in press without skin or clamps. Actual – 79 MPa azimuthal 480 µS longitudinal Drive in side clamps, increasing azimuthal preload to 90 Mpa Actual – 89 MPa 530 µS longitudinal

Assembly Steps 3. Remove press pressure, clamps deflect, azimuthal preload is 50 MPa. Actual – 66 MPa azimuthal 460 µS longitudinal Install skin, return to press, press to azimuthal preload of 90 MPa. Actual – 89 MPa azimuthal 310 µS longitudinal Bolt skin and release press. Final average azimuthal coil preload of 70 MPa. Actual – 77 MPa azimuthal 270 µS longitudinal

FEA at 300K 300K Glued Saz, Pa Radial Shim=0.1mm

FEA at 4K 4K Glued Saz, Pa At quench current the azimuthal Lorentz force in the mirror is ~30% lower than in the quadrupole model => lower coil prestress needed.

FEA at 18kA 4K 11.9T 18kA Glued Saz, Pa Radial Shim=0.1mm

Azimuthal full bridge readings during cooldown Reading from azimuthal full bridge on titanium, (strain x MOE)

Azimuthal full bridge readings during excitation Reading from azimuthal full bridge on titanium, (strain x MOE)

Azimuthal full bridge readings during excitation Readings from azimuthal full bridge on titanium, (strain x MOE) At 290K before testing: -77 MPa At 4.5K before excitation: ----- At 1.9K before excitation: ----- Increase with current: +50MPa At 290K after testing: -114 MPa Azimuthal full bridge summary:

Axial full bridge readings during cooldown Reading from axial full bridge on titanium from 290K to 4.5K.

Axial Full Bridge readings during excitation Reading from axial full bridge on titanium.

Axial Full Bridge readings during excitation At 290K before testing: +270 uS At 4.5K before excitation: -300 uS At 1.9K before excitation: -350 uS Increase with current: +50 uS At 290K after testing: +500 uS Axial full bridge summary:

Strain gauge readings during cooldown – end preload The “cold” readings are at 4.5K

Strain gauge readings during excitation These readings are at 1.9K

Strain gauge readings during excitation These readings are at 1.9K

Bullet reading summary

Quarter bridges bonded to coil during cooldown.

Quarter bridges bonded to coil during cooldown.

Quarter bridges bonded to coil during cooldown.

Quarter bridges bonded to coil during cooldown.

Summary Azimuthal full bridges – large positive change in strain with cooldown. Typical of some other mirrors. Possibly due to bending of coil. Increase with current of about 50 MPa. Axial full bridges – strain from +250 µS to -250 µS with cooldown. Slight tensile strain increase with current, returning at quench. Typical of axial bridges. End load “bullets” - Value change with cooldown unclear. Increase in compressive load with current, between 2-7 kN, slightly higher values on Return End than Lead End. Coil gauges – Uncalibrated. Cooldown data shown only. Some sign of bending of coil? Shell gauges still not be analyzed Coil gauges with excitation not analyzed