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Design and performance of the APPLE-Knot undulator.

Ji F, Chang R, Zhou Q, Zhang W, Ye M, Sasaki S, Qiao S - J Synchrotron Radiat (2015)

Bottom Line: Along with the development of accelerator technology, synchrotron emittance has continuously decreased.This results in increased brightness, but also causes a heavy heat load on beamline optics.Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University, 2005 Songhu Road, Shanghai 200438, People's Republic of China.

ABSTRACT
Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

No MeSH data available.


Related in: MedlinePlus

Performance of the APPLE-Knot undulator with Fig. 2(a) ▸ structure in horizontal (red), circular (green) and vertical (blue) modes. (a) Magnetic fields along the x (solid lines) and y (broken lines) directions. (b) Intensities (left axes) and polarizations (right axes) of photons at different energies. (c), (d), (e) Electron orbits and (f), (g), (h) electron velocities in the horizontal, circular and vertical modes, respectively.
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fig3: Performance of the APPLE-Knot undulator with Fig. 2(a) ▸ structure in horizontal (red), circular (green) and vertical (blue) modes. (a) Magnetic fields along the x (solid lines) and y (broken lines) directions. (b) Intensities (left axes) and polarizations (right axes) of photons at different energies. (c), (d), (e) Electron orbits and (f), (g), (h) electron velocities in the horizontal, circular and vertical modes, respectively.

Mentions: A simple and direct method to construct an APPLE-Knot undulator is to change the one to two period ratio of the APPLE-8 to two to three by combining two standard APPLE undulators (Fig. 2a ▸). The inner APPLE undulator with four magnet rows is responsible for the generation of photons with arbitrary polarization and the outer four rows are used to deflect the electron beam to move in a knot orbit. The geometry parameters of magnets in Fig. 2(a) ▸ are a = b = 35 mm, a′ = 22 mm and d = 65 mm. The clearances along the x direction are 3.5 mm between adjacent APPLE rows and 2 mm between adjacent APPLE and Knot rows. The clearance along the z direction is 10 mm between all adjacent magnets. The related magnetic fields in different modes are shown in Fig. 3(a) ▸. All the magnetic fields shown in this paper were calculated using the RADIA magnetostatics program (Chubar et al., 1998 ▸). To generate horizontal (vertical) polarized photons, the phases between different rows are adjusted so that the inner and outer APPLE rows generate magnetic fields along the vertical (horizontal) and horizontal (vertical) directions only. To generate circularly polarized photons, the phases are adjusted so that both the inner and outer APPLE undulators are in circular mode with different periods. The performance is shown in Fig. 3 ▸. The horizontal, vertical and circular polarizations are defined as , − and from Stoke parameters , and . For both horizontal (Fig. 3f ▸) and vertical (Fig. 3h ▸) modes, the velocities of electrons deviate from the undulator axis with a larger than 0.3 mrad angle and only small heat load remains inside the 0.6 mrad acceptance angle. However, part of the velocity locates in the 0.6 mrad acceptance angle for circularly polarized mode. Satisfactory performance can be achieved with heat loads of 31, 55 and 37 W for horizontal, circular and vertical modes inside the 0.6 mrad × 0.6 mrad acceptance solid angle, respectively, compared with 1106 W for a pure linear undulator. The only problem with this type of APPLE-Knot structure is the requirement for relative movement between all the magnet rows, which is not easy to implement.


Design and performance of the APPLE-Knot undulator.

Ji F, Chang R, Zhou Q, Zhang W, Ye M, Sasaki S, Qiao S - J Synchrotron Radiat (2015)

Performance of the APPLE-Knot undulator with Fig. 2(a) ▸ structure in horizontal (red), circular (green) and vertical (blue) modes. (a) Magnetic fields along the x (solid lines) and y (broken lines) directions. (b) Intensities (left axes) and polarizations (right axes) of photons at different energies. (c), (d), (e) Electron orbits and (f), (g), (h) electron velocities in the horizontal, circular and vertical modes, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4489533&req=5

fig3: Performance of the APPLE-Knot undulator with Fig. 2(a) ▸ structure in horizontal (red), circular (green) and vertical (blue) modes. (a) Magnetic fields along the x (solid lines) and y (broken lines) directions. (b) Intensities (left axes) and polarizations (right axes) of photons at different energies. (c), (d), (e) Electron orbits and (f), (g), (h) electron velocities in the horizontal, circular and vertical modes, respectively.
Mentions: A simple and direct method to construct an APPLE-Knot undulator is to change the one to two period ratio of the APPLE-8 to two to three by combining two standard APPLE undulators (Fig. 2a ▸). The inner APPLE undulator with four magnet rows is responsible for the generation of photons with arbitrary polarization and the outer four rows are used to deflect the electron beam to move in a knot orbit. The geometry parameters of magnets in Fig. 2(a) ▸ are a = b = 35 mm, a′ = 22 mm and d = 65 mm. The clearances along the x direction are 3.5 mm between adjacent APPLE rows and 2 mm between adjacent APPLE and Knot rows. The clearance along the z direction is 10 mm between all adjacent magnets. The related magnetic fields in different modes are shown in Fig. 3(a) ▸. All the magnetic fields shown in this paper were calculated using the RADIA magnetostatics program (Chubar et al., 1998 ▸). To generate horizontal (vertical) polarized photons, the phases between different rows are adjusted so that the inner and outer APPLE rows generate magnetic fields along the vertical (horizontal) and horizontal (vertical) directions only. To generate circularly polarized photons, the phases are adjusted so that both the inner and outer APPLE undulators are in circular mode with different periods. The performance is shown in Fig. 3 ▸. The horizontal, vertical and circular polarizations are defined as , − and from Stoke parameters , and . For both horizontal (Fig. 3f ▸) and vertical (Fig. 3h ▸) modes, the velocities of electrons deviate from the undulator axis with a larger than 0.3 mrad angle and only small heat load remains inside the 0.6 mrad acceptance angle. However, part of the velocity locates in the 0.6 mrad acceptance angle for circularly polarized mode. Satisfactory performance can be achieved with heat loads of 31, 55 and 37 W for horizontal, circular and vertical modes inside the 0.6 mrad × 0.6 mrad acceptance solid angle, respectively, compared with 1106 W for a pure linear undulator. The only problem with this type of APPLE-Knot structure is the requirement for relative movement between all the magnet rows, which is not easy to implement.

Bottom Line: Along with the development of accelerator technology, synchrotron emittance has continuously decreased.This results in increased brightness, but also causes a heavy heat load on beamline optics.Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, State Key Laboratory of Surface Physics, and Laboratory of Advanced Materials, Fudan University, 2005 Songhu Road, Shanghai 200438, People's Republic of China.

ABSTRACT
Along with the development of accelerator technology, synchrotron emittance has continuously decreased. This results in increased brightness, but also causes a heavy heat load on beamline optics. Recently, optical surfaces with 0.1 nm micro-roughness and 0.05 µrad slope error (r.m.s.) have become commercially available and surface distortions due to heat load have become a key factor in determining beamline performance, and heat load has become a serious problem at modern synchrotron radiation facilities. Here, APPLE-Knot undulators which can generate photons with arbitrary polarization, with low on-axis heat load, are reported.

No MeSH data available.


Related in: MedlinePlus