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NSLS-II Insertion Devices. Toshi Tanabe George Rakowsky, John Skaritka, Steve Hulbert, Susila Ramamoothy NSLS/BNL NSLS-II Accelerator Systems Advisory Committee 2006/10/9-11. Outline. List of NSLS-II insertion devices (baseline + options) Comment on Phase Errors

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Nsls ii insertion devices

NSLS-II Insertion Devices

Toshi Tanabe

George Rakowsky, John Skaritka,

Steve Hulbert, Susila Ramamoothy


NSLS-II Accelerator Systems Advisory Committee



  • List of NSLS-II insertion devices (baseline + options)

  • Comment on Phase Errors

  • Cryo-Permanent Magnet Undulator (CPMU) for hard X-rays

    • Cold Measurement Issues

    • New magnet and pole materials

  • Elliptically Polarized Undulator (EPU)

    • Apple-II v.s. HiSOR (SPring-8) Design

  • Permanent Magnet Damping Wiggler

  • Superconducting Wiggler (SCW)

  • Superconducting Undulator (SCU)

    • Conventional, VPU and HTS versions

  • No QPU, Figure-8, Revolver options are discussed

Rms phase errors
RMS Phase Errors

  • Improving the rms phase error from 3.0° to 2.0° changes the relative intensities by 86% -> 98% for harmonic 7 (D = 12% points), 81% -> 96% for harmonic 9 (D = 15% points), and 75% -> 93% for harmonic 11 (D = 18% points).

Roger Dejus

Nsls ii insertion devices

  • Cryo-Permanent Magnet Undulator (Hara, et. al., 2004)

    • Simple Concept: NdFeB has a negative thermal coefficient of remanent field (Br) [-0.1 % / K@20ºC], and of intrinsic coercivity (Hcj) [-0.5% / K@20ºC ]

    • Higher field and higher radiation damage resistance simply by cooling the magnet array in lower temperature (~150K)

  • Remaining Issues

    • Cold measurement system

    • Cold shimming technique if required

  • New Material R&D

    • PrFeB magnet and Dy pole combination for operation at lower temperature than 150K

History of mini gap undulators at the nsls
History of Mini-Gap Undulators at the NSLS

Currently Installed


Direct gap measurement by keyence ls 7030
Direct Gap Measurement by Keyence LS-7030

Measurement accuracy of ±2mm and repeatability of ±0.15mm

Upper Array



Lower Array

Direct gap measurement at micron resolutions
Direct Gap Measurement at Micron Resolutions

Keyence gap readings track with post temperatures


10 min

Upstream Gap

10 mm

Post temperatures

Downstream Gap


Cold measurement system
Cold Measurement System

Cold In-Situ Field Measurement

In-vacuum mapper with Hall probe. The postion accuracy is maintained by laser tracker and piezo controller.

  • In-vacuum streched / pulsed wire systems are

    also in consideration

Nsls ii insertion devices

  • Apple-II v.s. HiSOR EPU (eventually in-vacuum)

    • Apple-II : bigger tuning range, simpler structure

    • HiSOR EPU: easier shimming and more benign field profile

    • Better vacuum chamber design to reduce the radiation damage of permanent magnets maybe needed

Peak field profile comparison
Peak Field Profile Comparison

  • HiSOR

  • Apple-II

Tracking studies are needed to determine the effect

of dynamic aperture reduction due to these roll-offs.

Mpw 1 8t 15mm gap
MPW (1.8T / 15mm Gap)

  • Conventional Hybrid Design with Permendur Poles

    • Close to the limit with simple block structures

    • Reducing the gap with soft-iron poles will certainly reduce the cost

Superconducting wiggler
Superconducting Wiggler

  • NSLS-I Three Mode SCW by Oxford

    • 11 pole @ 3.0T (lu=17.6cm, gvac=19.5mm)

    • 5 pole @ 4.7T

    • 1 pole @ 5.5T

  • HTS version will be investigated

Superconducting undulator nsls proto type
Superconducting Undulator (NSLS proto type)

Bifilar SC winding APC-type NbTi with integral He gas cooling @ 4K

  • APC-type NbTi expected to run at Je=2000A/mm2

  • Cooling channel underneath the coils to ensure maximum cooling

(Ceramic) isolating spacer

Beam tube with integral cooling by He gas > 4K

Low carbon steel yoke


1006 Steel

Embedded He Gas Cooling Channel

Other insertion device r ds
Other Insertion Device R&Ds

  • New (In-vacuum) Gap Separation Mechanism

  • Superconducting EPU

  • High-Temperature Superconducting Undulator

    • Cryocooler capacity increases drastically with higher temperature (ex. 300W@40K, 600W@77K by Cryomech, Inc.)

    • Splices do not create quench problem if cooled sufficiently

    • Quench propagation is on order of magnitude slower than LTS

       Simpler and cheaper protection scheme


S. Chouhan


  • CPMU

    • Cold measurement and shimming are main remaining issues

    • New material R&Ds for further enhancement of the performance

  • SCW

    • OK for LTS

    • Higher field version / HTS version will be investigated

  • EPU

    • Apple-II or other structure to be determined after tracking study

    • Better vacuum chamber design to minimize radiation damage on magnets

    • In-vacuum EPU design will be a R&D subject

  • DW

    • Design and cost issues only

    • Possible candidate for new gap separation mechanism

  • SCU

    • Low temperature SCUs still require R&Ds

    • HTS versions are promising candidates in the future