Fabrication of test coil for D1 2m model Michinaka SUGANO KEK WP3 meeting 08/10/2014

1 Purposes of test coil fabrication 1 To verify the following items -Toolings for winding (Mandrel, Forming block, …) -Operation test for winding machine, hydraulic press, heater,… -Design of end spacers, winding and measurement of coil end -Confirmation of curing cycle (temperature profile and homogeneity, pressure) -Practice for quality assurance electrical tests of coil (ground fault, cable resistance, turn-turn insulation,…) Once test coil fabrication is completed, it will be used for -Commissioning of coil size measurement -Practice for attaching voltage leads -200mm-long mechanical model

2 Purposes of test coil fabrication 2 - Radiation resistant GFRP end spacers and wedges End spacers and wedges made of BT resin + S2 glass fibre were used for the first time Can newly developed hard GFRP end spacers be accommodated to the cable by curing ? - Curing with radiation resistant cyanate ester adhesive Curing temperature around 200 o C is needed, while it should not influence on contact resistance between the strands (lower than melting point of Stabrite coating) To consider compromised heat treatment condition and check if bonding strength is strong enough even for single layer coil End spacers were machined in house

3 Coil structure Cable: NbTi MB cable with APICAL and PIXEO insulation supplied by CERN Coil configuration: - Single layer coil - 44 turns, 4 coil blocks - Coil length: 2020 mm (between the end saddles) - 2D cross-section for HX-hole of 50 mm (old version) Wedge(GFRP) MP shim(GFRP) Pole shim (GFRP) Ramp box Center post Mandrel Pushing bar

4 Coil end -Coil end shape was slightly modified based on the result of practice winding Lead endReturn end Practice winding The cable angle was inclined too much and large gap between the cable and end spacer remained End spacer was re-designed to accommodate to the inclined cable (but further modification for the 2m-model coils should be needed)

5 Layer jump 2D cross-sections of the layer jump Coil layer at the straight sectionCollar layer at the lead end Pole turn Ramp box was designed in such a way that the layer jump turn go out uprightly Ramp box ABC A B C

6 Tensioner Feeder Turn table Winding mandrel Coil winding Winding machine Measurement of cable positions and angles Winding tension: Started from 40.9 kgf, decreased by 0.25 kgf/turn

7 Fitting of end spacer to cable Gap between the end saddle and the cable remained  We checked if the gap can be closed after curing

8 Preparation for curing SUS liner + Midplane shim SUS protective liner Pushing bars Alignment pin

9 Transfer of coil into forming block Insertion tooling Pushing the coil into the groove by screwing the bolts Forming block The coil was successfully inserted to the forming block using the alignment pin and jigs

10 How much should coil be compressed in curing ? Final size of coil is determined by yoking Pressure applied to coil Curing: 50 MPa Yoking: 100 MPa (max)  80 MPa From the results of 10 stack measurement (22 cables), coil after curing should be larger by 0.9 mm than the final size Forming block Mandrel Pushing bar Curing pressure 0.9mm-thick shim 0.9 mm-thick shims were inserted and coil was compressed until the gap was closed Gap

11 Curing press Thickness gauge Vertical load was applied incrementally until the gap was closed Longitudinal load (5.2 tonf) 90 ton hydraulic rams x3x7 over the length of 2m-coil Hydraulic ram

12 Determination of curing pressure Mandrel Forming block Gap was closed at hydraulic pressure of 23 MPa Pressure in curing Pressure pattern by pushing bars Check by Fuji paper Gap Coil pressure: 50 MPa

13 Configuration of heater and thermometers Heaters in forming block Heaters in mandrel Mandrel Form-block Heater Thermocouples (Both sides) 1m-long cartridge heater 4 in forming block 2 in winding mandrel Thermocouples 10 in forming block 5 in winding mandrel 2 at cartridge heater for mandrel Used for heater control

14 Consideration for heat treatment profile Recommended curing pattern given by the company: 150 o C x 4h o C x 4h o C x 4h Heat treatment condition for PIXEO T > 190 o C is necessary, but maximum temperature should be limited lower than 220 o C (melting point of SnAg coating) Adopted pattern: 150 o C x 4h o C x 8h Heat treatment condition for cyanate ester Heat treatment condition for curing 150 o C x 4h o C x 8h + >190 o C x 0.5h #3: Adopted pattern, thinly painted #1: Adopted pattern, thickly painted #2: Shortened pattern (no plateau), thinly painted Temperature ( o C) Elapsed time (hr) #3 #1 #2 Leakage of adhesive after HT in thickly painted sample “Adopted pattern + thinly painted” was selected Test with short sample cable and GFRP plate #1 #3

15 Heat treatment profile for curing 0.5h 190 ℃ 180 ℃ 150 ℃ 90 ℃ 8h4h4h 100 ℃ Pressure Temperature Longitudinal press - Maximum temperature was selected to be 190 o C - Vertical pressure was unloaded/reloaded during heat treatment - Longitudinal pressure was applied from the both ends of the coil Time Temperature

16 Actual temperature trend in curing Max. temperature could be controlled at o C (< 220 o C) 150 o C 180 o C 190 o C Expected temperature profile was realized F-E M F-W NNNMSSS Temperature profile to harden cyanate ester (150 o C x 4h o C x 8h) was obtained as expected Bonding of polyimide insulation

17 Coil after curing The gap between the end saddle and the cable was closed after curing  Hard BT resin + S2 glass GFRP can be accomodated to the cable Bonding between the cable and the wedges is sufficiently strong  Effectiveness of heat treatment profile is verified

18 Electrical tests after curing -No ground fault throughout winding and curing -No change of cable resistance (for 44 turn) -No damage of cable insulation checked by a bundle of fine Nb-Ti filaments -No turn-turn insulation failure at least up to 1 kV (Surge test) -Coil inductance: 2.3 mH Electrical soundness of the coil was confirmed After winding m  Under curing pressure, before curing m  After curing m  Surge test

19 Issues to be modified 1 The protective liner was plastically deformed after curing Additional support is needed for the layer jump Slit for the layer jump Protective liner Groove for the layer jump Protective liner Width of the groove should be made smaller Bottom surface of the ramp box Ramp box is slightly popping up Forming block

20 Issues to be modified 2 There is a gap at the boundary of the end spacer and the cable To make the cable more upright by elongating the length of coil end The leads for the QPH could be damaged Approach 1: Modification of coil end shape Approach 2: Filling the gap with shoe

21 Preparation for coil size measurement 50 ton loading test for checking the support structure and calibration of load-strain relationship for pushing bars have been completed Measurement using the test coil will be carried out soon Pushing bars with strain gauges -50 ton hydraulic press -Coil pressure up to 130 MPa -Continuous measurement using the 5.4 m-long bench -Two pushing bars each having 5 x 20mm-wide fingers Same system as CERN (Thanks to G. Kirby)

22 Future plan Test coil fabrication -Coil size measurement: Oct Mechanical short model: Dec m-model magnet development -Coil winding: Dec 2014 ~ Jan Delivery of collar and yoke plates: end of Jan Instrumentation: Feb Collaring: ~ end of Feb Yoking: Mar ~ April 2015 Test station -Delivery of 15kA current leads: ~end of March Inspection by local government: May Commissioning: Jun Cold test of 1st model magnet: Sep 2015

23 Summary -2m-long test coil for D1 was wound and cured. -Radiation resistant BT resin + S2 glass GFRP spacers and wedges were used for winding for the first time. Fairly good fitting was confirmed between the spacers and the cable after curing. -Heat treatment up to 190 o C for cyanate ester was tried and sufficiently strong bonding was confirmed. -Coil size measurement will be carried out soon. -Mechanical short model will be assembled using straight section cut out from the test coil. -We found some issued to be solved such as support of the ramp box and gap between the top of the cable and end spacer. Modification would be applied to the future 2m-long model coils.