Superferric quadrupoles and multipoles at the NSCL Al Zeller NSCL/MSU

NSCL Coupled Cyclotron Facility Experimental Areas Cyclotrons – up to  =0.6 for A<100 ECR Operational – Study N=82 nuclei and nuclei along the neutron drip line up to mass 30. R. York, F. Marti, T. Grimm et al.

A1900 K500 Coupling line K1200 Target A1900

Low current operation: Quads – 100 A (except 450A Dipoles – 200 A Sextupoles – 40 A Octupoles – 20 A

Standard NSCL quad design used in the A1900.

Schematic of A1900 triplet

A1900

A1900 quad with sextupole and octupole inserts. All cold. Multipoles mounted on bore tube.

8 triplets – 4 unique ones 16 quads have multipole inserts Sextupole largest radius inside pole tips Octupole smallest radius

Multipole inserts in a quad From Carsten Muehle (April 2003)

Sextupole on

A1900 Multipole coils

Inserting multipoles into quad triplet.

A1900 Insert into the helium vessel

A1900 multipoles Typical multipole values: Sextupole – 280 turns of 0.66 mm wire 43 x 5 mm J eng = 52 A/mm 2 T Octupole – 280 turns (same wire) 35.6 x 5 mm J eng = 32 A/mm 2 T

A1900 Quad mapper Mapper tube to which 3 Hall probes attached at different radii

A1900

Octupole map note nice symmetry Sextupole map note dipole term

A1900 Quadrupoles change effective length with excitation!

Multipole inserts in a quad From Carsten Muehle (April 2003)

Forces on Carsten’s magnet

A1900 In operation since No magnet failures Heat load: Quad triplets ~ 2 W each Valves and transfer lines ~ 75 W 2 of the dipole have about 3 W One dipole has a nitrogen leak and about 30 W One dipole has high nitrogen shield temp and is about 20 W Total heat load = 150 W (Plant capacity ~ 2 kW)

All coils self-protecting All the large quads quenched multiple times in testing Multipole coils have never quenched unless quad quenched first

S800

S800 sextupole Checking S800 Q2 sextupole with go-no go gauge

Presently ~ 70 superferric quads Building a radiation resistant quad using metal oxide CICC and warm iron

Inserts versus stand-alone multipoles Coil winding very easy and fast Assembly onto bore tube very labor intensive Generally, putting magnets in cryostat is time consuming. More magnets in a single vessel is cheaper.