SAMURAI magnet Hiromi SATO SAMURAI Team, RIKEN Requirements Geometry Magnetic field Superconducting coil and cooling system Present status of construction

Outline of “SAMURAI” Superconducting magnet Heavy Ion detectors Proton detectors Neutron detectors Large vacuum chamber Rotatable base SAMURAI spectrometer is designed for kinematically complete measurements by detecting multiple particles in coincidence. RI beam from BigRIPS target Proton superconducting coil pole(2m dia.) Neutron Heavy Ion rotate vacuum chamber SAMURAI consists of …

Requirements –Large field integral --> for high precision momentum analysis –Large pole gap --> for large vertical acceptance for neutrons –No coil link --> for large acceptance in the horizontal direction –Small fringing field --> for detectors around the target region and tracking detectors –Flexibility --> for various experimental conditions –Large momentum acceptance --> for heavy fragments and protons in coincidence –High momentum resolution --> for deuteron-induced reactions Field Integral 7 Tm (R/dR ~ 2.3 GeV/c for A/Z=3) --> mass separation  A =0.2 for A=100 Large Gap (0.8 m --> vertical ±5 degrees) Large opening (3.4 m --> holizontal ± 10 degrees) Small Fringing Field (< 50 50cm from magnet) H-type magnet with cylinder poles (2m in diameter) Magnetic field … about 3T at center by ~1.9MAT Field clamp Build-in vacuum chamber Rotatable base (from -5 to 95 deg)

Specification

Geometry 4K cryocoolers cryocooler for power lead cryocoolers for thermal shields LHe vessel vacuum chamber coil (with cryostat; not shown) Weight: ~600 ton yoke: 567 ton coil with cryostat: 8x2 ton vacuum chamber: 14 ton

Large Acceptance Large angular acceptance for neutron, vertical ±5 degrees horizontal ±10 degrees (~100% coverage up to E rel ~ 3 MeV, ~ 50% coverage at E rel ~ 10 MeV) By T. Kobayashi Inner gap of chamber: 0.8 m Opening : 3.4 m

Versatile usage Magnet can rotate around it’s center. Flexibility of settings is one of the good properties of SAMURAI. ( , n) reaction: neutron-rich side( , p) reaction: proton-rich side (p,p’), (p,2p), (p,pn), … pol. d-induced reactionEOS measurement 0 90

Magnetic field 1.9 MAT/coil I=560 A (66 A/mm 2 )  =infinity calc. by TOSCA 3.1T excitation center 1.9M AT Integral BL=7.05 Tm Y Z X F y =625ton F r =1918ton pole diameter yoke width B y (center) =3.1T Magnetic field is calculated with TOSCA.

Field clamp (for reducing fringing field) Fringing field along z-axis was estimated by TOSCA. Y Z X 2000 edge of yoke(1500) edge of field clamp(1750) Fringing field should be as small as possible. Requirement < 50 Gauss We checked the dependence of the thickness of field clamp on fringing field. FC thickness dependence thickness field clamp field integral Optimum thickness = 250mm B=3.1T

Fringing field at detector position Thickness of FC = 250mm Y Z X 2000 edge of yoke(1500) edge of field clamp(1750) 26 Gauss Magnetic Field at center detectors Z [ mm ] Check the amount of fringing field under several magnetic-field condition. Requirement is fulfilled.

Maxwell stress F y =1350ton at surface of pole _center =3.1T) by TOSCA Stress and warp of yoke was estimated with ANSYS. Max. stress=8.2MPa Max. warp=0.15mm 1350ton (Yoke was assumed to be one bulk iron in the calculation.)

Superconducting coils Superconducting coil Nb/Ti wire (3mm  ) 3411 turns/coil Cooled by liquid-He No coil link Cross section: 180x160mm 2 Outer diameter: 2710mm Inner diameter: 2350mm Cryocooler systems UP and DOWN independent For 4.2K: GM-JT x4, For 20K: GM x4, For 80K: GM x4, For current lead: GM x2, Field cramp Side yoke 5.3mm Lorentz force (270kN = 27.5ton) B=3.1T In free space Cryostat (coil case) is designed to be strong against this force. 12 cryocoolers are used in total.

Cryostat for superconducting coils cryocoolers for shield 4000 TOP view SIDE view LHe cryostat 4K cryocoolers cryocooler for power lead cryocoolers for shield    610 yoke pole coil 160x180 thermal shield (80K) LHe/F RP cross sectional view cryocoolers for shield 20K upper coil

Photos ~coil~ Coil winding, cryostat manufacturing and casing have started in the factory of TOSHIBA. FRP coil covered with resin space for LHe

Photos ~pit~ Magnet construction have started in RIBF site Main frame of rotatable base (2/5)

Construction schedule Now rotatable base stage cryostat+coil cryocoolers vacuum chamber yoke Six months are left for the construction. After finishing the magnet construction, other parts (beam duct, detectors, etc…) will be set. Radiation shield blocks must be re-arranged.

Summary Superconducting Magnet –7 Tm –large acceptance –Rotatable base … versatile usage –Yoke design … H-type –Coil … cooled by LHe Construction.. going on Finish.. May 2011 TODAY

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Where is “SAMURAI” ? RRC RILAC RIPS RARF SAMURAI Here! (Ready in 2011) ZeroDegree BigRIPS SRC IRC RI Factory RI Beam Factory pit new walls

Effect of holes on field clamp Field clamp should have a hole for cryostat. Effect on fringing field was checked. B _center =3.1T clamp detectors BL _with_hole =-4.12x10 -3 Tm BL _without_hole =-4.93x10 -3 Tm There is no serious degrading influence on fringing field. Y Z [cm] a hole for cryostat. 46cm x 23cm field clamp

Y X Effect of beam path in return yoke beam path For this configuration, return yoke should have a path (hole). top view X Z Effect on fringing field was checked. with path without path Magnetic field on Z axis B _center =3.1T 26gauss 19gauss BL _with_hole =-4.12x10 -3 Tm BL _without_hole =-2.93x10 -3 Tm 36%

Influence of hole and path; summary B _center =3.1T Basic : without hole and path effect of path in return yoke effect of hole on field clamp Difference of BL between Basic and Final -3.80x10 -3 Tm -4.12x10 -3 Tm 8.4% (Z: ) bending angle=0.097deg for 0.73GeV/c proton