Magnetic field analysis and achievable on-axis field for helical undulators.
The on- and off-axis magnetic fields for infinitely long, helical undulators were analyzed for linear and nonlinear poles. An analytical expression of the on-axis field for linear poles was derived in terms of coil current density, undulator period length, and coil dimensions. The derived expression showed that, when the undulator dimensions were scaled according to the period ratios, the on-axis fields were proportional to the periods, which is in agreement with calculations of model undulators. For undulators with nonlinear steel poles, when the undulator dimensions were scaled, the field distributions remained unchanged for a constant value of (current density x period). It was also shown that, for two scaled undulators, one with linear and one with nonlinear poles, the off-axis field components, normalized to the respective on-axis fields, had the same field distributions near the axis within the calculation errors. This implies that the derived normalized off-axis field for linear poles may be used for beam dynamic analysis in the fields of undulators with nonlinear poles within the beam chamber. Achievable on-axis fields were calculated for short-period undulators with parameters close to those for the proposed International Linear Collider (ILC) positron production undulators. The required undulator parameters for the ILC appear to be achievable depending on the Nb{sub 3}Sn superconductor packing factor in the coil and on how close the chosen operating current is to the critical current.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 969909
- Report Number(s):
- ANL/ASD/JA-60315; NIMAER; TRN: US1000655
- Journal Information:
- Nucl. Instrum. Methods Phys. Res. A, Vol. 584, Issue 2008; ISSN 0168-9002
- Country of Publication:
- United States
- Language:
- ENGLISH
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