Superconducting Cryogen Free Splittable Quadrupole for Linear Accelerators

Superconducting Cryogen Free Splittable Quadrupole for Linear Accelerators Progress Report V. Kashikhin for the FNAL Superconducting Magnet Team (presented by J. Kerby)

Outline • • Quadrupole design Quadrupole fabrication First test results Future test program 2

Responsibilities • • • N. Solyak, J. Kerby, A. Yamamoto - Specification N. Andreev, V. Kashikhin – Quadrupole design, fabrication D. Smith – Quadrupole yoke assembly T. Wokas – Coil fabrication, quadrupole assembly C. Hess – Quadrupole mounting to the top head, splices F. Lewis – electrical wiring, tests, and electronics D. Orrys – test coordination, DAQ, quench detection and protection M. Tartaglia – test leader, magnet training and Hall measurements G. Velev – rotational coil measurements 3

Quadrupole Specification & Superconductor Integrated gradient, T 36 Aperture, mm 78 Effective length, mm 666 Peak gradient, T/m 54 Peak current, A 100 Field non-linearity at 5 mm radius, % 0. 05 Quadrupole strength adjustment for BBA, % -20 Magnetic center stability at BBA, um Liquid Helium temperature, K Quantity required Nb. Ti wire diameter, mm Number of filaments 0. 5 7242 Filament diameter, um 3. 7 Copper : Superconductor 1. 5 Insulated wire diameter, mm 0. 54 Insulation Formva r Twist pitch, mm 25 5 RRR of copper matrix 100 2 Critical current Ic @ 4. 2 K, at 5 T 560 204 A 4

Quadrupole in Cryomodule (1) 5

Quadrupole in Cryomodule (2) 6

Quadrupole in Cryomodule (3) 7

Quadrupole Cold Mass Assembly 8

Two Halves of the Quadrupole 9

Half of Iron Yoke Assembly Laminated MI steel yoke Fixing weld Calibrated steel rod Base surfaces for assembly Lamination AISI 1010 steel end plate The yoke laminations are laser cut from MI low carbon 1. 5 mm thick steel. The half core is assembled in the FNAL IB 2 horizontal press. Calibrated rods and base surfaces provide package straightness. Final mechanical rigidity provided by fixing welds. 10

Half Yoke with Al End Plate Half yoke Coils Al end plate mechanically and thermally connected to the coil and outer shell Al collars providing better thermal conductivity between coils and cooling tube. Steel end plate 11

Coil Winding (January 21, 2011] 12

Quadrupole Coil Vacuum Impregnation 13

Quadrupole Coils & Tooling 14

Fabricated Quadrupole Coils Four coils were initially fabricated. Coil N 3 lead was damaged during test setup preparations. One more coil was fabricated to replace the damaged coil. 15

Quadrupole Yoke Parts 16

Laminated Yoke Assembly 1 3 1. Half yoke assembly in the press. 2. Half yoke final assembly 3. Yoke control assembly Yoke material – MI low carbon steel, 1. 5 mm thick. 2 17

Quadrupole with Top Head Assembly Top head Current leads Quadrupole yoke Yoke halves clamping rings 18

MTF Stand 3 for Quadrupole Test Stand 3 used for the initial quadrupole test and training in a bath cooling mode. It has 500 A current leads and the room temperature warm finger. The field measurements were made with 3 D Hall probe and rotational coil measurement system. 19

Quadrupole Electrical Scheme All coils connected in series. 4 RTD’s to monitor the temperature. 5 voltage taps to detect the quench. 4 coil heaters connected in series and fired when the quench event is detected. Quadrupole is protected with 9 Ohm dump resistor. The peak voltage is < 1 k. V. 20

Quench History Quench history for two thermal cycles Quench history for each coil Peak operating current 100 A. Magnet trained up to 110 A – limit for the Stand 3 peak safe pressure during uncontrollable quench. 21

Critical Current & Load Line Peak operating current 100 A. Magnet trained up to 110 A ( green line). Critical current (short sample limit) for this magnet is 185 A at the coil field 5. 4 T. 22

Quadrupole Gradient vs. Current At 90 A current the quadrupole reached the specified peak gradient 54 T/m. 23

Quadrupole Current during Tests 24

Magnetic Center Measurements (8 A-20 A) Quadrupole magnetic center shift at -20% current change dx<3 um, dy<0. 1 um. 25

Magnetic Center Measurements (40 A-60 A) Quadrupole magnetic center shift at -20% current change dx<6 um, dy<0. 1 um. 26

Magnetic Center Measurements (80 A-100 A) Quadrupole magnetic center shift at -20% current change dx<6 um, dy<0. 1 um. 27

Quadrupole Training Results • Quadrupole was initially trained to the 95 A during first thermal cycle (interrupted by the cryo system maintenance), and to 110 A during the second thermal cycle. • There were observed large voltage spikes up to 5 V, and after several power supply trip offs, was used 5 V QD threshold. • Each coil has 900 turns and all quenches had mechanical nature. • For the magnet protection were used strip heaters in each coil and an external dump resistor. 28

Quadrupole Measurement Results • During magnetic center position measurements was observed the time dependent effect. At -20% current change from the investigated maximum value, the magnetic center shift was less than 6 um. But when the current went up with several stops for measurements the value of magnetic center shift was 2 times larger. • Nevertheless, the first obtained results are very promising and close to the specified value 5 um. • The main center shift was observed for dx in the X-direction, and about zero for Y. It is suspected this is due to the effect of gap fluctuations between two halves of the magnet, in the next test this gap will be modified to ensure closure. 29

Future Tests The full set of goals for future tests includes: • thermal study of conduction cooling • quench performance (at 2 K) • protection heater performance (at 2 K) • integral field gradient and magnetic field quality at small (~1 cm) radius • quad center stability (measure to ~1 micron) over -20% variation in current. • The most critical design and fabrication issue for ILC quadrupoles is the micron level of magnetic center stability which only could be verified by very high precision magnetic measurements. 30