SIS 100 main magnetsSIS 100 main magnets

G. Moritz, GSI Darmstadt

(for E. Fischer, MT-20 4V07))

Cryogenic Expert Meeting, GSI,

September 19/20 2007

Main sc magnets of the synchrotron SIS 100

3334 W

7623 W

533 W

2078 W

1361 W

static load @ 4K

beam induced loss

dynamic load @ 4K

liquefaction

static load @ 50-80K(4K equivalent)

Example: Cryogenic load distribution of the Synchrotrons SIS 100/200 (maximum load)

AC loss contributions (dynamic heat load)

• Magnet iron yoke (hysteresis loss)• Structural elements (hysteresis and eddy current loss) • Beam pipe (eddy current loss)• Conductor (hysteresis and eddy current loss )

Mechanical structure / lifetime of the magnets

• SIS100 : 200 millions cycles within 20 years

• SIS 300: 1 million cycles within 20 years

minimization of movement of any part

R&D on material fatigue, crack propagation

Main R&D Topics for rapidly-cycling magnets (Hz-range)

Eddy and persistent currents • affect field quality

• produce large steady-state AC-losses in coil, yoke, structural elements, beam pipe

minimization of these effects

good heat removal

SIS 100 superferric dipole

• iron-dominated superferric design (window frame type)

• cold iron• maximum field: 1.9 T• ramp rate: 4 T/s• 3 m long, 16 turns

based on Nuclotron dipoleCollaboration: JINR (Dubna)

1- cooling tube, 3 - Superconducting wire, 3 - NiCr wire, 4 - Kapton tape, 5 – adhesive Kapton tape

• hollow-tube superconducting cable

with low hydraulic resistance

• two-phase helium cooling

• strands indirectly cooled

compact, low cost design

example: calculation of hysteresis loss in the brackets

AC loss reduction (model magnets / FEM-calculations)

70% of the Nuclotron dipole losses are in the yoke!!!

Experimental studies on model magnets Theoretical ANSYS calculations

example: loss reduction by slitting the pole and reduce brackets material

Heat release in test dipoles

0

10

20

30

40

50

Nuclotron stainlesssteel (SS)end plates

SMP endblock

insertions(z=5cm)

no SMP but6 slits

(z=20cm),reducedbrackets

reducedcoil end

loop

improvedsc-wire

(EAS) forNuclotron

cable

bracketsand end

plates fromSS, no slits

additional 6slits

(z=20cm)modifications =>

Qcy

cle,

J

totalyokecoil

Modifications: removed brackets laser cut lamination slits minimized coil ends

R & D Results: AC loss reduction @ 4 K

assumption for 20years operation costs comparison study:

nc version: 26M€

sc version: 2.6 M€

Loss (J) per cycle (0-2T, 4T/s), 1.4 m long test dipoles

SIS100 dipole coil design

Goal:

• accurate positioning

• reduction of point load

Result: tube will survive 20 years of operation!

Status:

• mockups were produced

• mechanical properties tested at 77K

Coil support structure Fatigue /crack propagation of the Cu-Ni- tube

detailed ANSYS model of the coil / conductor (Courtesy of E. Bobrov)

3 full length dipoles / 1 quadrupole under construction

• 2.1 T dipole, straight at BNG• 2.1 T dipole, straight at JINR• 1.9 T dipole, curved at BINP• 27 T/m quad, 1. 3 m at JINR

Cooling

• magnet– coil and yoke in series, coil first, determines the

flow resistance

• vacuum chamber (reinforced by rips)– by insulated pipes soldered to the rips

from BINP

operating cycles / loads

magnet designed for cycle 2c: 800 msec Injection, 1 sec Pulse (0-2 T, 4 T/s)

design limited by hydraulic resistance!!

new requirement: triangular cycle, 1 sec → load almost doubled!!!

→ Consequences for the refrigerator

pressure drop

Reduction of hydraulic resistance

• increase tube diameter → filling of aperture, double layer

• reduce number of turns → high current, single layer

Possible redesign of the magnet

→ increase iron outlet temperature !

Cooling system

• Magnets cooled in parallel

• Dipole defines the highest hydraulic resistance

– → some magnets (quadrupole, correctors) cryogenically in series

• Adaptation by orifices

• question: how much is the variation of flow resistance?