The present invention relates generally to undulators, and more particularly, relates to a magnetic undulator shim used for tuning any compact hybrid permanent magnet.
Undulators are also known as wigglers and insertion devices. The majority of synchrotron radiation sources, including free electron lasers, utilize insertion devices with a vertically oriented magnetic field that must be adjusted and tuned before use. Modern undulators, though machining of the pieces is more precise than ever before, still require tuning prior to use. An undulator can have the mechanical alignment of the magnetic poles to be machined, assembled, and fine-tuned to within 10 microns. The state of the art currently aligns undulators down to approximately 3 microns (0.003 mm). The errors that subsist after the mechanical alignment of the undulator are mainly caused by the local magnetic moment imperfections of the magnets. Therefore, even after mechanical alignment of the magnetic poles, the magnetic performance of undulators are still substantially out of the required specifications for alignment and further tuning must take place.
Traditional magnetic surface shimming techniques developed 30 years ago are still used today. These tuning techniques range from using a shim, which presented problems that had to be overcome. The prior art shim was magnetically unstable at the smallest undulator gap settings, or when the magnetic field was at its strongest. The prior art shim would flip up into the direction of the electron beam and stand on the surfaces of the poles. Once flipped up, it would interfere with the vacuum chamber surrounding the electron beam, even potentially puncturing the thin walls of the chambers. If the prior art shim flipped up or damages the vacuum chamber, the facility would be shut down for weeks at a time to fix and recalibrate the machine. Initially, to solve the flipping problem, the shim was glued to the surface of the magnet after tuning. However, even the best glues that can be used are damaged by radiation produced within the undulator, eventually ending with the same result of loose shims with flipping problems.
The prior art shim was inconvenient and imprecise to use and so undulators evolved by designing and machining the poles and magnets to be adjustable height. That is, every single pole and magnet height was designed and machined to be to manually height adjustable and permanently tune the magnetic field of the undulator. That not only significantly increases the costs of fabrication of the device, making manual adjustments to every single magnet and pole, but increases the costs of operation as well. Therefore, there is a need for an efficient, a cost-effective, a magnetically stable, and a mechanically stable way to tune an undulator.
Embodiments of the invention relate to a magnetic undulator shim for tuning any compact hybrid permanent magnet.
Embodiments of the present invention are illustrated in the accompanying figures where:
The following detailed description provides illustrations for embodiments of the present invention. Each example is provided by way of explanation of the present invention, not in limitation of the present invention. Those skilled in the art will recognize that other embodiments for carrying out or practicing the present invention are also possible. Therefore, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
The choice of the placement of the magnetic undulator shim 100 is defined by where the magnetic field of the undulator needs to be tuned. But, in any embodiment, the magnetic undulator shim 100 is placed across both a magnet and a pole. One magnetic undulator shim 100 can be used as shown in
Returning to
In accordance with the invention, the magnetic undulator shim 100 is made from any material capable of magnetically engaging the magnet 110 and the pole 112a and provide acceptable results of tuning the undulator. The material can be low carbon steel. The magnetic undulator shim 100 is thin enough to fit between the space between the top surface 120a of the pole 112a and the top surface 118 of the magnet 110, as seen in
As shown in
Referring to
In a simulation of the prior art shim and the present invention, it was shown that the prior art shim has a very small torque and if the shim angle mismatches the magnet chamfer, then the prior art shim will flip into the beam path at a minimum undulator gap of 8.5 mm. The simulation showed that the present invention, the magnetic undulator shim 100, has an increased torque by a factor of 10 thereby eliminating the issue of the shim being able to flip into the beam path. The present invention corrects the magnetic performance of the undulator.
The present invention is magnetically stable at even the smallest undulator gap settings, settings for which the prior art shims would be unstable and cause the shim to become displaced, or flip into the particle beam path. When the prior art shims flip into the beam path, the movement of the shim risks damaging the thin wall of the particle beam vacuum chambers. Instead, by using the present invention, the shim is magnetically stable and unable to become dislodged at even the smallest gap settings in an undulator; therefore, glue is unnecessary to keep the magnetic undulator shim 100 in place and from damaging the particle beam vacuum chambers. When the present invention is used within a traditional undulator, a cost-effective traditional undulator design and fabrication can be used. Additionally, when the present invention is used within a traditional undulator, tuning becomes more efficient and cost-effective.
It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements.
Any element in a claim that does not explicitly state “means for” performing a specified function, or “step for” performing a specific function, is not to be interpreted as a “means” or “step” clause as specified in 35 U.S.C. § 112, ¶ 6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C. § 112, ¶ 6.
The United States Government has rights in this invention pursuant to Contract No. DE-AC02-06CH11357 between the U.S. Department of Energy (DOE) and UChicago Argonne, LLC.
Number | Date | Country |
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06188096 | Jul 1994 | JP |