Prototype magnet for the splitter-polarizer design nEDM Meeting, ASU, 2008-02-09

1. Prototype magnet for the splitter-polarizer designnEDM Meeting, ASU, 2008-02-09 C. Crawford, W. Korsch University of Kentucky G. Greene University of Tennessee R. Redwine Massachusetts Institute of Technology

2. Outline • review of options for neutron guide • different polarizer/splitter designs • issues determining feasibility of T/R guide • T/R magnet prototypes – design, pros/cons • external quadrupole septum • internal foil septum • schedule and budget request • pretests at UKy • common SM tests at FP12 • magnet prototypes • bender/splitter revisited • more efficient design

3. Options for neutron polarizer (T/R) qin qout • all 3 designs rely on supermirror polarizers • high polarization • neutron phase space • R asymmetric bender • R, T lose 50% of flux • T/R higher divergence • construction • R standard technology • T/R, T involve R&D • T/R complicated B-field Transmission / Reflection polarizer (T/R) Transmission polarizer (T) 12x14 cm2 20x30 cm2 Reflection polarizer (R) 3x4 in2 each (R) (T)

4. Monte Carlo simulations • optimized figure-of-merit for R and T/R geometries • neutrons traced to center of 4He cell (30% loss after the end of guide) • T/R flux depends on thicknessof Si wafers (300 mm: 775 microns) • independent simulations using three software packages all consistent: • Geant4, McStas, and Neutrack (R) Optimization (T/R) Optimization

5. Cost projections • Decision decoupled from FnPB guide (first 8 m + 10 m) • bender more efficient downstream, new design in progress • if needed could insert bender upstream of 10m guide • Cost estimates for 15 m of beam guide (neutronics only) • T/R requires extra R&D, ~ $100k • Costs are comparable

6. Design of the T/R polarizer splitter • magnetization near vertex • effectively a quadrupole field • current bus along top/bottom • properties of thin films – need to be measured • magnetization only along surface of film • remanent magnetization after < 1ms pulse • extension of magnetization along multilayer N S 300 G S N

7. Second design of polarizer splitter 50 cm guide section Si pol. sheet Aluminum foil current septum • current septum in guide • must be thin Al foil • wrapped around guide sections • each segment magnetized separately • pros: closer to SM • cons: closer to SM • neutron absorption • mechanical stability?

8. SCHEDULE Spring 2008 – UKy test polarization reflectometry build current pulser Summer 2008 – LANSCE FP12 calibrate reflectometry measure needed pulse duration test extension of magnetization Fall 2008 – Spring 2009 – UKy test maximum current in foils design and build prototypes measure DC field gradient measure mechanical stability during current pulses Summer 2009 – LANSCE FP12 test neutron polarization in prototype, pulsed magnetization BUDGET REQUEST $10k – SM polarizers 1 batch m=2 glass substrate 1 batch m=2 Si (10x10 cm2) $10k – magnet prototype quadrupole, Al foils glass SMpol support Si wafer alignment holding field magnets structural support $8k – electronics power supply switches control / readout Student support at LANSCE Prototype and testing plans

9. New Bender Designs design A old splitterdesign design B • double up the bender and splitter • preserve the maximum efficiencyof Liouville’s theorem rationale • 25% loss of phase space in splitter • attempt to smooth out transition • use thin channels of bender polarizer • still need to do MC simulations • endorsed by Peter Böni expander converger

10. Summary • two prototypes for T/R designs • depend on unmeasured properties of SMpol coatings • test feasibility of each design at UKy and FP12 • improvement of R bender polarizer in parallel • low-risk plan B • future R&D with Si wafers • design and test support structure, materials • minimization of Si thickness