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[REPM2025_O6-3_Tanabe.pdf](https://mdr.nims.go.jp/filesets/b8dc02fb-9ae3-4ddf-93f8-2b272773e332/download)

## Creator

Toshiya Tanabe, Dean Hidas, James Rank, Marco Musardo, Thomas Brookbank, Brian Eipper, Patrick N'Gotta

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Applications of Permanent Magnets at the National Synchrotron Light Source-II](https://mdr.nims.go.jp/datasets/03c63262-3756-48c0-b9d7-cd7cadb3f9ea)

## Fulltext

Presentation TitleApplications of Permanent Magnets at the National Synchrotron Light Source-IIJuly 31st , 2025REPM 2025Toshi Tanabe (NSLS-II Insertion Device Group Leader)Not Export Controlled2ID Group Staff• Sr. Physicist (Group Leader)• Toshi Tanabe Ph.D.• Sr. Physicist (Deputy)Dean Hidas Ph.D.(Spectral calc., Controls)• PhysicistMarco Musardo (Mag. Meas)• Mechanical Engineer    James Rank (Ring WCC, LOTO, Maintenance)4• Mechanical EngineerThomas Brookbank• Electrical Engineer   Brian Eipper• Electro-mechanical TechnicianDan Migliorino • Electro-mechanical TechnicianBryan HollandPatrick N’Gotta3OutlineSynchrotron Light Source oPrinciple of Synchrotron Radiationo NSLS-II and World Wide Exampleso Wigglers and Undulatorso Various Insertion DevicesPM Applications for SR sourceso In-Vacuum Undulator (IVU) and Cryogenic Permanent Magnet Undulator (CPMU)o PM based Lattice Magnetso Higher performance PM than Pr2Fe14B?54Principle of SRSR is electromagnetic radiation produced by a relativistic electron when its path is deflected by a magnetic field B.Non-relativistic (v << c) Ee ~ EREST = 0.511 MeVo EM radiation at f = fROTATION o Radiation pattern like a dipole antenna o Horizontally polarized in mid-planeo Elliptically polarized above/below orbitEHV << CeRelativistic (v  c) Ee = γ EREST (0.38 to 8 GeV typ.)VCEHeBψdθElectrons are accelerated by RF cavity at fRF = n fROT o Radiation is emitted tangential to orbito Observer sees Doppler-shifted frequencieso Spectrum extends from RF to X-rays, o Pattern is compressed vertically into angle  ψ = 1/γ    o Total Radiated Power:  ∝ B422044324 ρπεγβ ceP =5Synchrotron Light Sources (lightsources.org)6NSLS-II Storage Ring &Beamlineshttps://www.bnl.gov/nsls2/Bare Lattice 3DW Lattice All-ID w.o SCW All-ID with SCWEnergy (GeV) 3Circumference (m) 791.958Emittance ex (pm-rad) 2086 957 747 657Energy Spread sd (%) 0.0514 0.0818 0.0799 0.093Energy Loss per Turn U0 (keV) 286.4 649.1 831.8 958Length of Long Straight (m) 9.3Length of Short Straight (m) 6.6bx, by at Long Straight Center (m) 20.1, 3.4bx, by at Short Straight Center (m) 1.8, 1.1Betatron Tunes nx, ny 33.2, 16.26Natural Chromaticisty xx,  xy -98.5, -40.2 -98.4, -39.8 -98.4, -39.9 -98.2, -40.1Momentaum Compaction ac 0.000363Radiation Damping Time tx,ty, ts (ms) 55, 55, 28 24, 24, 12 19, 19, 9.5 16.6, 16.6, 8.3RF Frequency (MHz) 499.681Number of RF Buckets 1320Number of Bunches 1056Time between Bunches (ns) 2Total Beam Current  (mA) 400 (500)Average bunch current (mA) 0.47Average bunch charge (nC) 1.25Synchrotron Tune @ VRF = 3 MV 0.00871 0.00862 0.00856 0.0085RMS Bunch Length @ VRF = 3 MV (mm) 2.7 4.34 4.27 5.02NSLS-II Ring Parameters (as of Aug. 24)7Wigglers and UndulatorsHalbach Pure-PM UndulatorHorizontally magnetized blocks boost on-orbit field Halbach PM-hybrid UndulatorIron poles concentrate flux from larger magnet blocks B g• Put magnet arrays inside vacuum chamber• Minimum gap can be reduced to stay-clear required  by electron and photon beams (a few mm)• Reduce period  more periods  more photons!• Shorter period  higher photon energies • Must be UHV-compatible  Ni- or Ti-N-coated• PM must withstand baking to >100°C without demagnetizing  Use Hybrid car motor grades of PMIn-Vacuum Undulator(For hard x-rays)gWiggler Spectrum K>>1Undulator Spectrum K ~2mceBK uπλ20≡ where λu is period length 8Permanent Magnet Undulators| APPLEIII and Variable Period Undulators | Markus Tischer, 04.11.19, HZB BerlinVariable gap Adjustable phase DELTAAPPLE-II APPLE-XCourtesy of M. Tischer and P. Vasin9In-Vacuum Undulator (IVU)• PM must be coated with TiN, Ni or Al to be used in the ultra-high vacuum (UHV) environment• PM must have high enough coercivity to withstand baking >100 C°World’s 1st In-vacuum IDs at KEK In 199210Temperature characteristic of Remanence of Permanent Magnets for CPMU101.64T@80K1.61T@140K50 100 150 200 250 3001.401.451.501.551.601.65NdFeBPrFeBRemanence ( T )Temperature ( K )ⒸProterial, Ltd.F.J. Bögermann, et. al., Proc. of IPAC2014pp123811Demagnetization Curves11-7000 -6000 -5000 -4000 -3000 -2000 -1000 00.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.7100K60KNMX-U52SH200K250K300K140K  J, B (T)H (kA/m)-7000 -6000 -5000 -4000 -3000 -2000 -1000 00.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.61.7100K60KNMX-68UH200K 250K 300K140K  J, B (T)H (kA/m)Nd2Fe14B Pr2Fe14BⒸProterial, Ltd.12Cryogenic PM Undulator (CPMU) at Bessy-II and at TPSCPMU17CPMU15• No need to bake the PMs as cryo-pumping is expected• Higher coercivity due to lower temperature for better radiation hardness13PM use for other accelerator magnetsPM dipole magnets for ESRF-EBS (Extremely Brilliant Source) PM quadrupole magnets for the Swiss Light Source –II14NSLS-IIU Complex Bend LatticeHistory of Complex Bend developmentComplex Bend concept (Interleaved dipoles and quadrupoles)G. Wang et al., PRAB 21,(2018)Superconducting magnet design (B=1.05T, G=500T/m)Decoupled Dipole-Quadrupole magnets (B=0.25-0.5 T, G=±250T/m)G. Wang et al., PRAB 22,(2019)Combined Function Dipole-Quadrupole PMQs (B=0.25-0.5T, G=±130T/m)Halbach type Hybrid typeS. Brooks et al., PRAB,(2020) P. N’Gotta et al., PRAB,(2016)T. Shaftan et al., Complex Bend II, BNL-211223-2019-TECH, Oct 2018T. Shaftan, Methodology for designing Complex Bend lattice, BNL-223858-2023-TECH, Jan 202215NSLS-II Rotating Coil Bench for PM Quads12 mm diameter rotating coil with 1.8 mm thick printed circuit board, wiring, and ceramic bearings.Small PMQuadrupole for complex bend 16 wedges (SmCo) in a Halbach configuration housed in an aluminum keeper L =46.7 mm , G= 146.6 T/m, ir= 6.35 mm, or= 15.875 mm; 12.7 mm bore diameter. 16Halbach Magnet Development- Prototypes, TestCB concept successfully tested at NSLS-II linac diagnostic beamline 100-200 MeV electron beam energy  S. Sharma et al.Vacuumscmelze magnet prototypeIn-house magnet prototype In-house PMQ prototype measurement 1 defocusing magnet assembly successful 1 focusing assembly foreseen 9 defocusing magnets assembly procured 6 focusing magnets assembly procuredNormalized Absolute High sextupole component (b3) Assembly error (800 um error for vgap) Modification of the aperture spacer 17Future ProspectTheoretical BHmax varies among different articles….Q: Is there any magnet which can theoretically outperform Nd2Fe14B Magnet?Complied by ChatGPT O3Rank Material system Status BHmax (MGOe)Comment1α″-Fe₁₆N₂ (iron nitride)late-stage R&D (Niron, academic)135 (theoretical)Rare-earth-free, record-high M_s; synthesis & stability hurdles.2Nd₂Fe₁₄B (Nd-Fe-B, sintered; N48–N56) widely commercialized 52–56Current industrial benchmark; Dy/Tb diffusion boosts coercivity.3Sm₂Fe₁₇N₃ (Sm-Fe-N) pilot-scale R&D≤62 (theoretical)Heavy-rare-earth-free; experimental values still <20 MGOe.4(Nd,Ce)₂Fe₁₄B (Ce-rich Nd-Fe-B) pre-production ≈43Lower-cost Ce replaces part of Nd; slight strength drop.5L1₀-FeNi (tetrataenite) lab synthesis42~110? (theoretical)Abundant Fe, Ni; ordering kinetics & scaling under study.6Sm₂Co₁₇ (“2-17” Sm-Co) commercial 29–33 Excellent stability to 350 °C; Co cost.7SmCo₅ (“1-5” Sm-Co) commercial 15–25Great temp stability; lower energy density than 2-17.18Summary• Insertion devices for modern accelerators require state-of-the-art permanent magnets to achieve the highest magnetic performance necessary for generating ultra-bright X-ray beams.o A higher Br is desirable; however, moderate to high coercivity is also essential to withstand demagnetization during assembly and the baking requirement of IVU.o Nd₂Fe₁₄B magnets exhibit a spin reorientation transition at low temperatures.o Pr2Fe14B or (NdxPr1-x)2Fe14B magnet is used for CPMU.o More potent magnet (α″-Fe₁₆N₂ or L1₀FeNi?) is highly anticipated.• Permanent magnets are increasingly replacing conventional lattice magnets in modern accelerators, driven by the need for high magnetic field gradients and energy-efficient operation.o For next-generation storage rings, Sm₂Co₁₇ magnets are the preferred choice for lattice applications owing to their low temperature coefficient and enhanced resistance to radiation-induced degradation. Applications of Permanent Magnets at the National Synchrotron Light Source-II ID Group Staff Outline Principle of SR Synchrotron Light Sources (lightsources.org) NSLS-II Storage Ring &Beamlines Wigglers and Undulators Permanent Magnet Undulators In-Vacuum Undulator (IVU) Temperature characteristic of Remanence of Permanent Magnets for CPMU Demagnetization Curves Cryogenic PM Undulator (CPMU) at Bessy-II and at TPS PM use for other accelerator magnets NSLS-IIU Complex Bend Lattice NSLS-II Rotating Coil Bench for PM Quads Halbach Magnet Development- Prototypes, Test Future Prospect Summary