Prototype magnet for the splitter-polarizer design
nEDM Meeting, ASU, 2008-02-09
C. Crawford, W. Korsch
University of Kentucky
G. Greene
University of Tennessee
R. Redwine
Massachusetts Institute of Technology
Collab. Mtg., ASU, 2008-02-09 #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
Collab. Mtg., ASU, 2008-02-09 #3
(T)
Transmission / Reflectionpolarizer (T/R) Transmission
polarizer (T)
Reflectionpolarizer (R)
Options for neutron polarizer
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
12x14 cm2
20x30 cm2
3x4 in2
each
(T/R)
in out
(R)
Collab. Mtg., ASU, 2008-02-09 #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 thickness
of Si wafers (300 mm: 775 microns)
independent simulations using three software packages all consistent:• Geant4, McStas, and Neutrack
(R) Optimization (T/R) Optimization
Collab. Mtg., ASU, 2008-02-09 #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
Collab. Mtg., ASU, 2008-02-09 #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
300 G
N
S
S
N
Collab. Mtg., ASU, 2008-02-09 #7
Second design of polarizer splitter
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?
50 cm guide section
Si pol. sheet
Aluminum foil current
septum
Collab. Mtg., ASU, 2008-02-09 #8
Prototype and testing plans
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
Collab. Mtg., ASU, 2008-02-09 #9
New Bender Designs
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
design A
design B
old splitterdesign
expanderconverger
Collab. Mtg., ASU, 2008-02-09 #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