A Model Superconducting Helical Undulator Wound Using a Wind and React ${\rm MgB}_{2}$ Multifilamentary Wire

Superconducting undulators (SCUs) with period >15 mm can offer much higher on-axis undulator field B0 than state-of-the-art cryogenic permanent magnet undulators (CPMUs) with the same period and vacuum gap. The commissioned NbTi planar SCUs for user operation in the Karlsruhe Institute of Technology (KIT) synchrotron and the Advanced Photon Source (APS) storage ring are operated stably without quenches, producing outperformed photon flux in the high energy part of the hard X-ray spectrum. Another potential advantage of deploying SCU is its radiation hardness, a crucial characteristic for being used in free electron lasers (FELs) driven by high repetition rate superconducting linear accelerators (LINACs) and diffraction limited storage rings (DLSRs) with small vacuum gap and large averaged beam current. Development of shorter period but high field SCU is an important mission in an EU founded CompactLight project as this technology would reduce both the length of undulators and the length of LINACs. This review paper first overviews the research and development of SCUs worldwide from late 1970s to 2021, then presents the SCU design requirements and compares the theory limits of different types of planar and helical SCUs, and finally reviews the technical challenges including the SCU cryostat, the magnetic field measurement, the integral/local field correction and the high-temperature superconductor (HTS) challenges and prospects the research needs for SCUs.

Section: Mgb 2 Helicalmentioning

confidence: 99%

Review and prospects of world-wide superconducting undulator development for synchrotrons and FELs

Zhang

Calvi²

2022

“…The cross section of the strand is shown in figure 1 and its parameters are reported in table 1. The present undulator design was the same as an earlier model wound with a MgB 2 strand and presented in [17].…”

Section: Strand Selection Undulator Design and Fem Based Field Modelingmentioning

confidence: 99%

“…As with our previous MgB 2 undulator model coil [17], this present coil was designed to be wound with one continuous piece of strand without the need for joints (see figures 5(a) and (b)). Type 316 stainless steel was used to fabricate the beam pipe and disk-and-pin assembly for the undulator ends.…”

Section: Fabricationmentioning

confidence: 99%

See 1 more Smart Citation

A model superconducting helical undulator fabricated using a small filament, tube-type, multifilamentary Nb₃Sn wire

Majoroš

Sumption

Susner

et al. 2012

A model helical undulator 250 mm in length, designed and fabricated with a period of 14 mm, was tested in a liquid helium bath. The helical coil was wound with a multifilamentary, tube-type Nb 3 Sn strand with 217 sub-elements. The coil I c and the magnetic field in the bore were measured at 4.2 K in a liquid helium bath using a Hall probe. I c was found to be 842 A, and the bore field reached the design specification of 0.8 T. The transverse bore field was also measured as a function of position along the length of the undulator axis and was seen to exhibit the expected sinusoidal behavior. The measured I c was compared with that obtained from a crossing of a load line (determined from FEM modeling) with the I c (B) curve of a short sample Nb 3 Sn strand. The coil exhibited the same critical current as the short sample.

“…On the other hand, MgB 2 has the advantage of a higher T c , enabling it to be operated using cryocoolers rather than direct liquid cooling. However, previous undulators developed with PIT (1 G) MgB 2 have not had sufficient in-field performance to make useful undulators [12]. However, with the performance available from 2 G MgB 2 , it is now possible to make a competitive, practical MgB 2 -based undulator.…”

Section: Introductionmentioning

confidence: 99%

Development and testing of a three-period, subsize 2G AIMI MgB₂ planar undulator

Garg,

Rochester,

Majoros

et al. 2023

Compared to Nb3Sn- and NbTi-wound superconducting undulators (SCUs), MgB2-wound SCUs are of interest for future electron synchrotron beam light sources owing to their higher temperature operating margin and associated stability. In this study, a three-period undulator consisting of twelve racetrack coils wound with 2nd generation (2 G) multifilamentary advanced-internal-magnesium-infiltration MgB2 strands were fabricated and tested in liquid and gaseous helium (He) over a temperature range of 4.2 K–20 K. The coil winding cross sections (in each coil) were 5 mm wide and 4.8 mm thick. At 4.2 K, a critical current (I c) of 325.7 Amps produced a maximum undulator bore field of 1.19 T. It should be noted that the short, 3-period nature of the coil led to an asymmetry in the field profile (the maximum positive field was 1.19 T, the maximum negative was −0.25 T), suggesting a peak field of 0.72 T in the absence of end effects. Finite element modeling (FEM) results of simulations for a one meter long undulator of otherwise identical design gave 0.85 T (larger because of higher currents enabled by the lower field). But in any case, the I c value coil reached is 94% of that of the short sample (dictated by the 1.19 T positive field for the coil as tested). FEM was performed to study the magnetic field profile, which was validated experimentally. The magnetic field was measured using a Hall probe which was translated along the beam axis during measurement to explore the spatial field variation along the beam travel direction. The spatially alternating field was asymmetric, and the maximum field was more prominent in the positive direction than in the negative direction, the difference being due to broken symmetry, that is, short coil end effects. In this work, we show useful fields are possible for MgB2 undulators; the use of such conductors can allow a larger thermal margin and enable conduction-cooled operation.