The adjustable phase planar helical undulator
- Stanford Linear Accelerator Center, Menlo Park, CA (United States)
- Lawrence Berkeley Lab., CA (United States)
The study of magnetic and biological materials which exhibit magnetic circular dichroism has created a demand for circularly polarized x-rays whose helicity may be switched between the right and left hand senses. At present, circularly polarized x-rays are obtained from storage ring bending magnets by accepting radiation from above and below the axis, but insertion device sources are desired for greater intensity. Planar helical undulators are magnetic insertion devices that generate helical magnetic fields. The charged particle beam executes a helical trajectory in the device, and produces elliptically polarized x-rays. The special case of circularly polarized x-rays is most in demand. We present here the design description of a new type of planar helical undulator, which we are constructing for the SPEAR storage ring at the Stanford Synchrotron Radiation Laboratory (SSRL). It comprises four rows of pure permanent magnet blocks, one row in each quadrant about the axis defined by the electron beam. Rows may be translated longitudinally with respect to each other to change the helicity of the magnetic field they create at the position of the beam. They may also be translated longitudinally to vary the energy of the x-rays emitted, unlike designs where this function is performed by varying the gap between the rows. This work includes numerical calculations of the fields, electron trajectories, x-ray spectra, off-axis effects, and mechanical design considerations.
- Research Organization:
- Stanford Linear Accelerator Center, Menlo Park, CA (United States); Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00515; AC03-76SF00098
- OSTI ID:
- 10105317
- Report Number(s):
- SLAC-PUB-6337; SLAC/SSRL-0052; LBL-34542; CONF-930511-494; ON: DE94003434; TRN: 94:000820
- Resource Relation:
- Conference: PAC `93: international particle accelerator conference,Washington, DC (United States),17-20 May 1993; Other Information: PBD: Aug 1993
- Country of Publication:
- United States
- Language:
- English
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