Magnets
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Abstract: Many different techniques have been investigated at Diamond for optimising sextupole strengths*. One method not previously studied is to exploit the null space of the chromaticity response matrix. By performing a singular value decomposition (SVD) of the chromaticity response matrix, combinations of sextupole strengths are identified which alter the nonlinear lattice whilst keeping the chromaticity unchanged. Applying these sextupole strength changes opens an avenue to improve the beam lifetime and the injection efficiency at fixed chromaticity, thereby preserving the instability thresholds from collective effects. The results of applying this technique are presented both for beam tracking simulations for the Diamond-II lattice, including machine errors, and for machine-based measurements on the present Diamond synchrotron.
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Jun 2025
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Accelerator Physics
Magnets
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Abstract: Superconducting undulators (SCUs) may be capable of
generating stronger magnetic fields at shorter periods than
can be achieved using permanent magnet or planar undulators.
Therefore, the range of x-ray wavelengths that an XFEL
facility can generate for users could be expanded by exploiting
SCU technology. Prototyping work is ongoing at STFC
to build a helical superconducting undulator (HSCU) of 1 m
length with 13 mm period and 5 mm magnetic gap designed
for future XFEL facilities. As part of this work, a test cryostat
has been built to cool 325 mm long prototype magnets
to 4 K and to measure the field profile of the HSCU using a
calibrated cryogenic Hall sensor. The magnetic field measurements
are necessary to confirm the peak-to-peak field
quality and trajectory wander of an electron beam through
the device in order to understand the impact of the HSCU
on the FEL radiation output. We present here a description
of the test cryostat and the results of the magnetic field
measurement regime performed on the prototype HSCU
coil.
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Jun 2025
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Accelerator Physics
Magnets
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Open Access
Abstract: Diamond Light Source has installed four 2 m long, 17.6 mm period Cryogenic Permanent Magnet Undulators (CPMUs) as upgrades for crystallography beamlines since 2020, with two more planned within the next year. The CPMUs provide 2 - 3 times more brightness and 2 - 4 times more flux than the pure permanent magnet (PPM) devices they are replacing. They have been designed, built, and measured in-house. All four have a 4 mm minimum operating gap and are almost identical in their construction: the main difference being an increase in the number of in-vacuum magnet beam support points from four to five, between CPMU-1 and CPMUs 2 - 4, to better facilitate shimming, particularly at cold temperatures. The ability to shim at cryogenic temperatures necessitated the development of an in-vacuum measurement system. The details of the measurement system will be presented alongside the mechanical and cryogenic design of the undulators; including issues with the magnet foils, and the shimming procedures and tools used to reach the tight magnetic specifications at room temperature and at 77 K.
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Feb 2024
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Magnets
Vacuum
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Open Access
Abstract: An in-vacuum Hall probe measurement system was designed, built, and used to measure four Cryogenic Permanent Magnet Undulators (CPMUs) at Diamond Light Source. The devices were tuned to correct the phase error at cold temperatures based on the measurements from the in-vacuum system. The in-vacuum system consists of a stretched wire system supplied by Danfysik and an in-house built Hall probe system. The Hall probe system has gone through two iterations: the first beam was prone to deforming with temperature changes; the second was made thicker following design changes to the magnet holders and girders of the CPMUs which allowed more space for the beam inside the vacuum vessel. The design and commissioning of the measurement system will be presented, along with some measurements of the CPMUs at room temperature and at 77 K. Details such as triggering of the Hall probe measurements, height compensation, and temperature compensation will be covered.
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Jan 2024
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Accelerator Physics
Magnets
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Open Access
Abstract: Beam-based alignment (BBA) is a standard tool at accelerators for aligning particle beams to the centre of quadrupole magnets. Traditional BBA measurements have been slow, potentially taking many hours for a whole machine. We have developed a tool, based on results previously reported at the ALBA synchrotron, that uses fast excitation of magnets to speed up measurements. We show the results of different measurement and analysis techniques in comparison to the currently used slow method.
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Jan 2024
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Insertion Devices
Magnets
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Open Access
Abstract: Over the last three years (2020-2022) Diamond Light Source has installed four in-house designed, built, and measured Cryogenic Permanent Magnet Undulators (CPMUs). All four are 2 m long with a 17.6 mm period and have a minimum operating gap of 4 mm. These have replaced existing 2 m long in-vacuum Pure Permanent Magnet (PPM) devices to improve the flux to several of Diamond's MX (Macromolecular Crystallography) beamlines by a factor of 2-4. In this paper we present the mechanical and cryogenic design considerations, and the shimming procedures and tools developed to produce these devices. The performance of the CPMUs compared to their PPM counterparts will also be reviewed.
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Jan 2024
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Accelerator Physics
Magnets
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Open Access
Abstract: Superconducting undulators provide a possible means of broadening the range of wavelengths that can be covered by an XFEL facility by generating larger magnetic fields at shorter periods than can be achieved using permanent magnet undulators. As part of ongoing prototyping work at STFC to develop a superconducting helical undulator with 13 mm period and 5 mm magnetic gap, a test cryostat has been designed and built to investigate the performance of 325 mm long prototype magnets. The test cryostat is used to cool prototypes to 4.2 K and to power them to a full operational current of 250 A. Cryogenic Hall sensors measure the field in the magnet bore during testing. Techniques to measure the field profile and the integrated field components inside the small, closed magnet bore have also been developed. These measurements are crucial for understanding the magnetic performance of the prototype magnets and identifying and implementing suitable corrections to the field integrals. We present here the first cooling and magnetic field measurement results of the prototype undulators.
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Sep 2023
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Magnets
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Abstract: Over the last three years (2020-2022) Diamond Light Source has installed four in-house designed, built, and measured Cryogenic Permanent Magnet Undulators (CPMUs). All four are 2 m long with a 17.6 mm period and have a minimum operating gap of 4 mm. These have replaced existing 2 m long in-vacuum pure permanent magnet (PPM) devices to improve the flux to several of Diamond’s MX (Macromolecular Crystallography) beamlines by a factor of 2-4. In this paper we present the mechanical and cryogenic design considerations, and the shimming procedures and tools developed to produce these devices. The performance of the CPMUs compared to their PPM counterparts will also be reviewed.
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Sep 2023
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Accelerator Physics
Magnets
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Open Access
Abstract: Electromagnets have traditionally been used in accelerators due to their wide range of tuneability with high accuracy, but are a major factor in power consumption due to resistive losses in the coils and inefficiencies in power and cooling systems. Use of permanent magnets can greatly reduce power consumption, but it has proved difficult to produce the same range of tuning with comparable field accuracy and stability. A tuneable permanent magnet quadrupole has been developed at STFC Daresbury Laboratory that moves permanent magnet blocks relative to fixed steel structures that define the field, allowing strength to be changed while suitable field homogeneity is maintained. This prototype magnet has been installed in the Diamond Light Source booster-to-storage ring transfer line, aiming to demonstrate the operation of ZEPTO (Zero-Power Tuneable Optics) technology on a real accelerator for the first time. We present results of beam-based measurements of gradient and magnetic centre and comparison with an existing electromagnet in the same transfer line, showing that it is capable of maintaining the same injection efficiency as a traditional resistive electromagnetic quadrupole during normal operation.
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Sep 2023
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Insertion Devices
Magnets
Mechanical Engineering
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Abstract: The main factors that cause the X-ray beam to drift are discussed in this chapter. Issues such as movement of the source or mechanical and thermal instabilities of the main optical elements of the beamline are translated into movement of the X-ray beam at the sample, intensity drifts and nonlinearities on the energy scale, affecting the quality of the data collected. The main steps that need to be taken to prevent and/or minimize the effects of these drifts are described, and approaches such as feedback systems are presented. The polarization of the beam delivered by the different types of X-ray sources used for synchrotron-based spectroscopy experiments is also presented. The on-axis and off-axis polarizations of the bending magnet and insertion devices such as wigglers and undulators are discussed.
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May 2023
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