SCU1 Vertical Test Results

Matt Kasa9/16/2014

Vertical Cryostat Assembly

• Coil Training• Record the current decay and the terminal voltage

across the coils during a quench• Hot spot temperature estimate derived from the

current decay and MIITs

• Hall Probe field scans for preliminary magnetic measurements• Carbon fiber guide tube in the gap of the magnet• Cloth bellows attached to the vertical stage, ices up

during a scan• Field scans were performed after training the magnets

Period length mm 18

Periods N 59.5

Magnetic length m 1.07

Magnetic gap mm 9.5

Conductor Diameter mm 0.6

SCU1 Parameters

Coil Training

• Both main coils trained to 580 A, same Ic as the short prototypes

• Core 1 – 67 training quenches• Core 2 – 140 training quenches• MIITs hot spot temperature estimation with

cores wired in series was ~60 K• Maximum voltage at terminals with cores

wired in series was ~120 V

400 A Main, 0 A Correction

• Final 1st integral is ~-750 G-cm. Equivalent to a dipole field of -5.7 G• Final 2nd integral ~400 kG-cm^2• S-shaped trajectory due to no correction current

400 A Main, 24 A Correction

• Offset added to the field to compensate for apparent dipole, therefore 1st integral is 0• S-shaped trajectory is fixed by correction coils, but the offset cannot be fully corrected while keeping a straight trajectory

• Due to 1018 steel used for the core, 1006 will be used in the future

• Field integrals scale with main current• Absolute values are uncertain, will be measured

with rotating coil in horizontal measurement system

• Phase errors are low without shimming• Had a 500 A scan with ~3.2 deg. RMS

1st Integral Correction• Unclear what causes the dipole field• A pair of coils will be installed above the top core and below the bottom core to provide a means for

correction• 20 turns of superconductor with 20 A of current results in ~10 G dipole field

2nd Integral Correction• SCU1 needs to use external correctors – plan is to install

correction coils upstream and downstream of the device inside the cryostat• 130 turn racetrack coil, 22 AWG with a 25 mm iron core • 1340 G at 4 A• Tied to the 1st Stage cooling circuit

Magnetic Gap• Magnetic gap increases towards the ends of the device

• Magnetic measurements indicate that the gap is ~0.1 mm larger

• An attempt will be made to adjust the thickness of the gap spacers to create a more uniform gap

Summary• The two cores reached the same critical current as the short prototypes

• The SCU1 preliminary magnetic measurements are very encouraging

• Low phase errors appear to be achievable without the need for shimming

• The 1st and 2nd integrals can be corrected with external correction coils

• The uniformity of the magnetic gap will be improved

Extra Slides

Inductance and Stored Energy

Effect of the Cooling Channel and Low Carbon Steel

• 2d simulations of the magnet assembly in FEMM• 1018 LCS

• No channel• 19 mm• 25.4 mm

• 1006 LCS• No channel• 19 mm• 25.4 mm

• Only correction current, no main

Cooling channel

Cooling channel

Top Core

Bot Core

Gap

Effect of the Cooling Channel and Low Carbon Steel – Correction Field

Effect of the Cooling Channel and Low Carbon Steel – Correction Field Integral