Accelerator Physics
Vacuum
|
Open Access
Abstract: Vacuum vessels of many existing and planned synchrotron light sources feature metallic coatings. In some combinations, they might cause a resonator-like peak in the longitudinal impedance. In this simulation study, we demonstrate how different parameters of non-evaporable getter (NEG) can increase momentum-spread growth and, hence, reduce microwave-instability thresholds. The first key insight of this study: The spread of the coating-layer thickness amongst vacuum vessels results in significantly reduced momentum-spread growth. Therefore, we recommend including randomised coating when designing vacuum components and modelling the impedance for a synchrotron light source. The second key insight of this study: Insertion devices featuring rectangular geometry and NEG coating might cause a multi-peak structure of the longitudinal impedance which can drive additional momentum-spread growth.
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Dec 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
Vacuum
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Open Access
Abstract: Ion instabilities are a major concern in diffraction-limited storage rings. ELEGANT offers a `strong-strong' model for ion simulations that describes both the beam and ions using multi-particles. To balance accuracy and computing resources, a simplified model using ILMATRIX and one IONEFFECTS element per turn is employed to study the ion effects of the Diamond-II storage ring. After benchmarking, it was found that the simplified model overestimates the ion instability compared with element-by-element tracking by a small amount. A preliminary vacuum conditioning process has been studied, and ion instabilities have been analysed at different stages for various filling patterns. This paper outlines the simulation settings and presents preliminary results, including the filling patterns to be used at each stage of vacuum conditioning. The ion instability for hybrid filling patterns at the expected operational vacuum condition is also studied.
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Sep 2023
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Vacuum
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Abstract: An in-vacuum Hall probe measurement bench was designed, built, and used to measure four Cryogenic Permanent Magnet Undulators (CPMUs) at 77 K at Diamond Light Source. The devices were tuned to correct the phase error at cold temperatures based on the measurements from the in-vacuum bench. The in-vacuum bench consists of a stretched wire system supplied by Danfysik and the in-house Hall probe bench. The Hall probe bench has gone through two iterations: the first 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 bench inside the vacuum vessel. The design and commissioning of the bench will be presented, along with some measurements of the CPMUs at room temperature and at 77 K. Details such as height compensation, temperature compensation, and triggering of the Hall probe measurements will be covered.
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Sep 2023
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Vacuum
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Open Access
Abstract: The conceptual design of the vacuum system for the Diamond-II storage ring upgrade is described. Due to the small vessel cross section, typically 20 mm inside diameter (ID), and the consequent conductance limitation, distributed pumping is provided by non-evaporable getter (NEG) coating supplemented by ion pumps at high gas load locations. In-situ bakeout is incorporated to allow rapid recovery from both planned vacuum interventions and unplanned vacuum events. The vacuum vessels are constructed mainly from copper alloy while stainless steel is used in regions of AC magnets requiring low electrical conductivity. The proposed layout, engineering and build sequence of the vacuum system are described along with gas flow simulations confirming the vacuum performance advantages of NEG-coated vessels compared with uncoated vessels.
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Jun 2019
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Diagnostics
Magnets
Mechanical Engineering
Optics
Vacuum
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R.
Bartolini
,
C.
Abraham
,
M.
Apollonio
,
C. P.
Bailey
,
M. P.
Cox
,
A.
Day
,
R. T.
Fielder
,
N. P.
Hammond
,
M. T.
Heron
,
R.
Holdsworth
,
J.
Kay
,
I. P. S.
Martin
,
S.
Mhaskar
,
A.
Miller
,
T.
Pulampong
,
G.
Rehm
,
E. C. M.
Rial
,
A.
Rose
,
A.
Shahveh
,
B.
Singh
,
A.
Thomson
,
R. P.
Walker
Open Access
Abstract: Diamond has recently successfully commissioned a major change in the lattice consisting of the substitution of a standard double-bend achromat (DBA) cell with a modified four-bend achromat (4BA) cell called “double-double bend achromat” (DDBA). This work stems from the original studies initiated in 2012 towards a Diamond upgrade and provides the benefit of an additional straight section in the ring available for insertion devices. This paper reviews the DDBA design and layout, the implications for technical subsystems, the associated engineering challenges and the main results of the commissioning completed in April 2017.
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May 2018
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Diagnostics
Vacuum
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Open Access
Abstract: In recent years, there has been an increasing demand for noninvasive beam size monitoring on particle accelerators. Ideally, these monitors should be cost effective and require little or no maintenance. These monitors should also be suitable for both linear and circular machines. Here, the experimental setup is described in detail, and the results from a diffraction radiation beam size monitor are presented. This monitor has been tested on the Cornell Electron Storage Ring using a 1 mA (
1.6
×
10
10
particles per bunch) single bunch electron beam at 2.1 GeV energy. Images of the target surface and the angular distribution of the emitted diffraction radiation were acquired at wavelengths of 400 and 600 nm. These measurements are compared to two analytical models.
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Mar 2018
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Mechanical Engineering
Optics
Vacuum
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Abstract: An overview of the double branch 185m I14 Nanoprobe
beam-line under construction at DLS will be presented
together with the end-station design in further
detail. The end station consists of a split vacuum vessel
containing a KB mirror configuration (at UHV) and the
sample environment (at HV) which is just 50mm from the
end of the final KB optic. An in-vacuum detector is
mounted between the KB and the sample whilst two externally
mounted detectors will operate between 0.25m &
3m from the sample. Four cryogenic samples can be
brought into the vessel at a time and transferred remotely
to the sample position with cooling provided by a Helium
pulse tube cooler. With an initial 50nm size beam, stability
is absolutely critical and careful attention has been
paid in the design to mitigate any thermal and structural
sources of vibration. An array of interferometers reference
the KB mirrors and sample position and will be used to
actively correct for any drifts. The very tight space constraints
involved have greatly increased the complexity
and duration of the design but testing of prototypes is now
underway. The system is scheduled for build and test
through the Autumn 2016.
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Jun 2017
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Detectors
Vacuum
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Open Access
Abstract: The purpose of the project was to design and simulate
a window assembly to be used in GISAX/GIWAX1 experiments.
The window lies between the sample and theWAXS2
detector, a modified, in-vacuum detector, with modules removed
to allow scattered radiation to pass through to a
SAXS3 detector positioned downstream. The window uses
75 μm thick Kapton® HN film and given the size, pressure
and the short distance to the sensors, it was necessary to
support it on a frame.
To avoid any information loss from shadowing of the
detector, a frame was designed so that shadows will be projected
into the gaps between the detector modules. The
geometry was such that DMLS4 was an effective way of producing
the item. Given the slenderness of the structure and
the forces it supports, the material approaches or exceeds its
yield point, so a bilinear, isotropic, hardening material model
was chosen; moreover, large deflections were enabled. Also,
the contacts were modelled with augmented Lagrange frictional
formulation. All these assumptions made the analysis
strongly non-linear.
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Jun 2017
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Mechanical Engineering
Vacuum
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Open Access
Abstract: The project required a sample environment to deliver experiments
in vacuum or helium, with high humidity, including
capacity to use aggressive solvents. The compact, transportable
system incorporates a high precision in-vacuum
manipulator/ positioning stage (with repeatability better than
1 μm/ 1 mdeg) allowing for multiple sample configurations.
Current sample mounts include in-situ film formation (Doctor
Blade), thermal annealing/drying heater stage, sample
cooling and multiple sample stages; the system has been
designed to accommodate many sample substrate formats.
The existing end station camera system has been upgraded
to include two, in-vacuum, WAXS and SAXS area detectors,
which are custom builds based on the Pilatus 6M. The
SAX detector module includes three in vacuum, independent
,configurable SAXS beam stop manipulators to block
GISAXS transmitted, reflected and specular flare as well as
isotropic and anisotropic SAX, a photon sensitive detector
shutter plate is included. The 4mm diameter tungsten beam
stops each include a miniature photodiode to measure beam
intensity and can be positioned to within 10 μm precision in
X and Y over 300mm x 250mm motion range.
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Jun 2017
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