Development of Non-Invasive Calibration Software for Front End X-Ray Beam Position Monitors at Diamond Light Source, Oxfordshire, UK
59
C.E. Houghton, C. Bloomer, L. Bobb
DLS, Oxfordshire, United Kingdom
Tungsten blade based photoemission X-ray Beam Position Monitors (XBPMs) are widely used as white beam diagnostics at synchrotrons. Traditionally, the scale factors are determined by stepper motor movements of the XBPM, or by controlled electron beam displacements, and measuring the response. These measurements must be repeated for each ID gap to produce a complete set of scale factors for all operational conditions. This calibration procedure takes time and cannot be done while users are acquiring data. In addition, the scale factors can vary over time due to changes to the storage ring. It is possible for these scale factors to become inaccurate, reducing the accuracy of the beam position measured by the XBPMs. By using the intrinsic kHz electron beam movements and correlating the signals from electron beam position monitors and XBPMs it is possible to have a real-time calculation of the scale factors without the need to disturb user operation. Presented in this paper is a method to non-invasively calculate scale factors during normal user operation. A comparison of the precision of this method versus the traditional stepper motor method is presented.
X-Ray Pinhole Camera Spatial Resolution Using High Aspect Ratio LIGA Pinhole Apertures
71
N. Vitoratou, L. Bobb
DLS, Oxfordshire, United Kingdom
A. Last
KIT, Eggenstein-Leopoldshafen, Germany
G. Rehm
HZB, Berlin, Germany
X-ray pinhole cameras are employed to provide the transverse profile of the electron beam from which the emittance, coupling and energy spread are calculated in the storage ring of Diamond Light Source. Tungsten blades separated by shims are commonly used to form the pinhole aperture. However, this approach introduces uncertainties regarding the aperture size. X-ray lithography, electroplating and moulding, known as LIGA, has been used to provide thin screens with well-defined and high aspect ratio pinhole apertures. Thus, the optimal aperture size given the beam spectrum can be used to improve the spatial resolution of the pinhole camera. Experimental results using a LIGA screen of different aperture sizes have been compared to SRW-Python simulations over the 15-35 keV photon energy range. Good agreement has been demonstrated between the experimental and the simulation data. Challenges and considerations for this method are also presented.
Diamond-II Electron Beam Position Monitor Development
168
L.T. Stant, M.G. Abbott, L. Bobb, G. Cook, L. Hudson, A.F.D. Morgan, E.P.J. Perez Juarez, A.J. Rose, A. Tipper
DLS, Harwell, United Kingdom
The UK national synchrotron facility, Diamond Light Source, is preparing for a major upgrade to the accelerator complex. Improved beam stability requirements necessitate the fast orbit feedback system be driven from beam position monitors with lower noise and drift performance than the existing solution. Short-term beam motion must be less than 2 nm/sqrt(Hz) over a period of one second with a data rate of 100 kHz, and long-term peak-to-peak beam motion must be less than 1 µm. A new beam position monitor is under development which utilises the pilot-tone correction method to reduce front-end and cabling perturbations to the button signal; and a MicroTCA platform for digital signal processing to provide the required data streams. This paper discusses the challenges faced during the design of the new system and presents experimental results from testing on the existing machine.
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XFEL Photon Pulse Measurement Using an All-Carbon Diamond Detector
416
C. Bloomer, L. Bobb
DLS, Oxfordshire, United Kingdom
W. Freund, J. Grünert, J. Liu
EuXFEL, Schenefeld, Germany
M.E. Newton
University of Warwick, Coventry, United Kingdom
The European XFEL can generate extremely intense, ultra-short X-ray pulses at MHz repetition rates. Single-crystal CVD diamond detectors have been used to transparently measure the photon beam position and pulse intensity. The diamond itself can withstand the power of the beam, but the surface electrodes can be damaged since a single pulse can already exceed the damage threshold of the electrode material. Presented in this work are pulse intensity and position measurements obtained at the European XFEL using a new type of all-carbon single-crystal diamond detector developed at Diamond Light Source. Instead of traditional surface metallisation, the detector uses laser-written graphitic electrodes buried within the bulk diamond. There is no metallisation in the XFEL X-ray beam path that could be damaged by the beam. The results obtained from a prototype detector are presented, capable of measuring the intensity and 1-dimensional X-ray beam position of individual XFEL pulses. These successful measurements demonstrate the feasibility of all-carbon diagnostic detectors for XFEL use.
Measurements for Emittance Feedback based on Resonant Excitation at Diamond Light Source
492
S. Preston, L. Bobb, A.F.D. Morgan, T. Olsson
DLS, Oxfordshire, United Kingdom
In the Diamond storage ring, the vertical emittance is kept at 8 pm rad by an emittance feedback which modifies the strengths of skew quadrupoles. A new feedback using a stripline kicker to control the vertical emittance by exciting the beam resonantly at a synchrotron sideband is planned to avoid modification of the optics. This is crucial for the anticipated Diamond-II upgrade of the storage ring, which will have a much smaller equilibrium emittance than the existing machine. A larger coupling is therefore needed to keep the vertical emittance at the same level, potentially reducing the off-axis injection efficiency and lifetime. Measurements of the beam oscillation and emittance have been performed at the existing storage ring to characterise the effects of chromaticity and impedance on the optimal excitation frequency, where the emittance is increased significantly while the beam oscillation is kept low. The implications for simulating the emittance feedback for the Diamond-II storage ring are also discussed.
