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 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

List of NSLS-II IDs

RMS Phase Errors Roger Dejus 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).

CPMU 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 Currently Installed Proposed

X-25 MGU Installed in the NSLS X-Ray Ring

Direct Gap Measurement by Keyence LS-7030 Measurement accuracy of ±2mm and repeatability of ±0.15mm Upper Array Detector Emitter Lower Array

Direct Gap Measurement at Micron Resolutions Keyence gap readings track with post temperatures 35C° 10 min Upstream Gap 10 mm Post temperatures Downstream Gap 30C°

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

EPUs 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 Apple-II HiSOR Tracking studies are needed to determine the effect of dynamic aperture reduction due to these roll-offs.

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 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) 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 Yoke: 1006 Steel Embedded He Gas Cooling Channel

Other Insertion Device R&Ds New (In-vacuum) Gap Separation Mechanism Superconducting EPU Inner cage S. Chouhan 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

Summary CPMU EPU DW SCW SCU Cold measurement and shimming are main remaining issues New material R&Ds for further enhancement of the performance 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 SCW OK for LTS Higher field version / HTS version will be investigated SCU Low temperature SCUs still require R&Ds HTS versions are promising candidates in the future