Search

This paper addresses the design of beam position monitor (BPM) devices suitable for fourth-generation diffraction-limited X-ray storage rings. Detailed investigations of the electromagnetic (EM) phenomena occurring inside the component under various working conditions are carried out by considering different BPM EM models defined by their geometry and materials. Moving from a theoretical characterization of the common round geometry, rhomboidal structures are studied through a careful numerical analysis relying on advanced computer-aided tools. Several critical elements, such as wakefields, pick-up signal extraction, and trapped and propagating modes, are explored from the simulation point of view and from the experimental one, by deploying a manufactured microwave test bench, which is employed to measure the radio frequency behavior of a BPM prototype built at Elettra Sincrotrone Trieste. The aim of the proposed study is to identify a satisfactory tradeoff between achievable performance and practical realizability for BPM devices operating in last-generation light sources. [ABSTRACT FROM AUTHOR]

The beam position is the most important reference basis for the operation of synchrotron radiation light sources, particularly for commissioning the first-turn injection of fourth-generation light sources. To improve the accuracy of the beam position measurement, we analyzed methods for calculating the beam position, and a finite element calculation and the stretched wire calibration system were used to demonstrate the procedure. We proved the relationship between the coverage range, fitting order, scanning step size, and accuracy both theoretically and experimentally, which can provide a basis for selecting the appropriate fitting order for different operation stages of the accelerator. It was proved that the accuracy of beam position calculations using simplified polynomial coefficients is comparable to those without a simplified one, which can save resources for reading electronic processing. The testing results of a batch of beam position monitors (BPMs) were in good agreement with the finite element calculation results, and the small difference between the manufactured BPMs also proved that quality control was performed well, and it benefited from button sorting. [ABSTRACT FROM AUTHOR]

The beam position is the most important reference basis for the operation of synchrotron radiation light sources, particularly for commissioning the first-turn injection of fourth-generation light sources. To improve the accuracy of the beam position measurement, we analyzed methods for calculating the beam position, and a finite element calculation and the stretched wire calibration system were used to demonstrate the procedure. We proved the relationship between the coverage range, fitting order, scanning step size, and accuracy both theoretically and experimentally, which can provide a basis for selecting the appropriate fitting order for different operation stages of the accelerator. It was proved that the accuracy of beam position calculations using simplified polynomial coefficients is comparable to those without a simplified one, which can save resources for reading electronic processing. The testing results of a batch of beam position monitors (BPMs) were in good agreement with the finite element calculation results, and the small difference between the manufactured BPMs also proved that quality control was performed well, and it benefited from button sorting.

BackgroundTo measure the beam positions of High Energy Photon Source (HEPS), different types of beam position monitors (BPMs) have been developed. The position sensitivity coefficient is an important parameter of BPMs by which the position of the beam can be calculated.PurposeThis study aims to establish a method for calculating the position sensitivity coefficient of BPMs.MethodsThe position sensitivity coefficients of various types of BPMs, such as round, elliptical, and octagonal pipes, were determined by using the boundary element method (BEM). The azimuth button angles in the elliptical BPM of the HEPS booster and the button distances in an octagonal BPM on the Beijing Electron Positron Collider II (BEPCII) storage ring were derivated by the application of BEM. Furthermore, the position sensitivity mappings of the BPMs was calculated.ResultsThe difference in sensitivity results of the round BPM calculated by the BEM and the analytical value is approximately 1%. The error between the calculated and experimental measurement results of the position sensitivity coefficients of the elliptical and octagonal sections is approximately 2%.ConclusionsThe BEM is a reliable method for calculating the position sensitivity coefficient of BPMs, which can be used in BPM design.

Beam diagnostics is one of the main tasks during the operation of charged particle accelerators. The work presents the concept of a beam instrumentation system that provides diagnostic procedures and allows measurement and adjustment of the key beam parameters in a linear resonant proton accelerator of the DARIA compact neutron source: current, position, profile, emittance, energy, and phase characteristics. An important requirement is to carry out measurements during the accelerator adjustment procedure, when the beam parameters can be changed in a wide range. It is proposed to include in the main structure of the system such types of diagnostic devices as beam current transformers, stripline beam position monitors, wire scanners, ionization beam cross-section monitor, slit emittance meter, bunch shape monitor, and a water-cooled Faraday cup. Particular attention is paid to nondestructive methods of diagnostics taking into account a high pulse and average beam intensity in conjunction with a relatively low beam energy to provide continuous operational control of the beam parameters. The main physical principles of operation, typical characteristics, as well as features of the practical implementation of the devices are included. The possible layout of diagnostic units in the accelerator is proposed, taking into account the peculiarities of using the proposed types of detectors in various parts of the accelerator. [ABSTRACT FROM AUTHOR]

This paper addresses the design of beam position monitor (BPM) devices suitable for fourth-generation diffraction-limited X-ray storage rings. Detailed investigations of the electromagnetic (EM) phenomena occurring inside the component under various working conditions are carried out by considering different BPM EM models defined by their geometry and materials. Moving from a theoretical characterization of the common round geometry, rhomboidal structures are studied through a careful numerical analysis relying on advanced computer-aided tools. Several critical elements, such as wakefields, pick-up signal extraction, and trapped and propagating modes, are explored from the simulation point of view and from the experimental one, by deploying a manufactured microwave test bench, which is employed to measure the radio frequency behavior of a BPM prototype built at Elettra Sincrotrone Trieste. The aim of the proposed study is to identify a satisfactory tradeoff between achievable performance and practical realizability for BPM devices operating in last-generation light sources.

Beam position monitor (BPM) characterization has been widely studied at the synchrotron. The characteristic impedance of a stripline BPM was designed using a simulation and measured using the time-domain reflectometer method. The mechanical and electrical parameters of the feedthroughs with the buttons used for the BPMs were measured. Special care was taken in the analysis of the consistency of the four channels of the BPM. The feedthroughs were sorted based on their capacitance values. This paper presents the characterization results of the feedthroughs and BPMs. The electro-mechanical offsets were measured using the Lambertson method, and the calibration coefficients were measured using a stretched wire. The BPM differences introduced during mass production were determined by a statistical analysis of the measurement results. [ABSTRACT FROM AUTHOR]

Beam position monitor (BPM) characterization has been widely studied at the synchrotron. The characteristic impedance of a stripline BPM was designed using a simulation and measured using the time-domain reflectometer method. The mechanical and electrical parameters of the feedthroughs with the buttons used for the BPMs were measured. Special care was taken in the analysis of the consistency of the four channels of the BPM. The feedthroughs were sorted based on their capacitance values. This paper presents the characterization results of the feedthroughs and BPMs. The electro-mechanical offsets were measured using the Lambertson method, and the calibration coefficients were measured using a stretched wire. The BPM differences introduced during mass production were determined by a statistical analysis of the measurement results.

BackgroundBeam position monitor (BPM) is an important beam measurement component of accelerators, and it generally needs to be calibrated before online operating. High energy photon source (HEPS) and upgrade of Beijing electron positron collider (BEPCII) will need a large amount of BPM, which brings challenges to the calibration work.PurposeThis study aims to design and implement an automatic BPM calibration system for raising calibration efficiency and improving the accuracy of BPM measurement after calibration.MethodsFirst of all, an analog beam generating device, precision motion and support device, signal processing electronics and industrial computer were employed to compose the hardware of the calibration system. Then, the control software was programmed by Python to realize automation of the calibration, and the binary polynomial regression algorithm was used to determine the probe calibration coefficient. Finally, the appropriate calibration parameters were optimized by the combination experiments with sufficient raw data, and the influence of calibration range, number of calibration points and fitting order on calibration accuracy were analyzed.ResultsThe calibration system can automatically complete the BPM probe calibration. The BPM accuracy can reach 40 μm over the entire calibration range, and 7 μm in the local linear region.ConclusionsThe calibration system of this study meets application requirements and achieves the expected function. The measurement accuracy of the calibrated BPM is related to factors such as the order of the polynomial, the calibration range and the selection of calibration points.

Considered is the diffraction radiation of a flat modulated beam of electrons flowing between two identical circular nanotubes made of silver. The electromagnetic field of such a beam is a two-dimensional H-polarized surface wave, which propagates in the same direction as the beam, with the phase velocity equal to the beam velocity. This field excites the currents on the nanotubes that radiate even if the beam does not touch the scatterers. For numerical solution, we use the method of partial separation of variables and the addition theorems for cylindrical functions that reduces the diffraction radiation problem to a matrix equation. On casting this equation to the Fredholm second-kind form, we compute far-field scattering cross-sections and field patterns with controlled accuracy. The obtained results show that a shift of the beam trajectory from the central-symmetric position triggers the excitation of certain resonances, which are absent otherwise. This may serve as a basis for the design of novel optical-range beam position monitors of nanoscale dimensions. [ABSTRACT FROM AUTHOR]

A compact beam-position monitor was constructed using a linear contact image sensor attached to a plastic scintillator and tested using a 230 MeV proton beam. The results indicate that the beam position can be obtained in real-time, and the beam position with a precision of up to 0.03 mm. The compactness and high precision of the device hold considerable potential for it to be used as a beam-position monitor and offline, daily quality assurance monitor in hadron therapy. • The method can provide a high precision and high resolution beam position for flash irradiation in particle therapy in real-time. • The method using contact image sensor with scintillator does not require a long focal length for camera and it is free of image distortion. • The method can be integrated into medical particle accelerator for feedback control and daily quality assurance.

A stable, reliable and well-calibrated beam position monitor (BPM) system is essential for a safe and reproducible operation of accelerators. The BPM system enables the measurement of important machine and beam parameters, such as the Twiss parameters, and helps to avoid damage to accelerator components by high-energy particle beams or radiation. In this paper, we discuss a new BPM calibration scheme tested at the Taiwan Photon Source (TPS). By altering the current in a single horizontal or vertical corrector magnet, we generate an orbit distortion with respect to the nominal reference orbit. The difference orbit is measured by observing the change of the beam position at each BPM pickup location as a function of the corrector current. The analog BPM signals are digitized by analog-to-digital converters (ADC), giving raw, non-calibrated beam position data for each BPM. By comparison of the beam orbit response in terms of raw ADC data from each BPM with the expected beam displacement we can calibrate the beam position monitors. Moreover, because of limited setup time available after a long shutdown, this new procedure acts as a fast, easy way to calibrate the BPM system. [ABSTRACT FROM AUTHOR]

Fourth-generation synchrotron radiation sources demand new quality for the electron beam diagnostic systems. Some of diagnostic system elements have to be accurately developed or redeveloped due to match the new requirements. Beam position monitor (BPM) is a most used detector and tens (even hundreds) BPMs are installed in numerous positions along beam transfer lines, booster and storage rings. Modern approach to this device development assumes such features as short transient time, wide bandwidth, high sampling rate, low noise architecture and reasonable production and maintenance price. As a part of the system, the BPM electrodes should meet all those requirements. In this article we describe a development procedure for high quality capacitive electrodes for the BPM. 3D electromagnetic model allows estimation of the sensitivity, frequency response and tolerance requirements for the manufacturing of hundreds of monitors. Presented here equivalent scheme for the electrodes is a basis for the BPM electronics design. [ABSTRACT FROM AUTHOR]

Abstract The Rare-isotope Accelerator complex for ON-line experiments (RAON) is an accelerator for heavy ions, such as uranium and oxygen. To correct the beam trajectory in the post-linac with low- β , we developed a beam position monitor. In the post-linac, the beam is accelerated from 0.5 MeV/u to 18.5 MeV/u, and each bunch has an electric charge of less than 10 pC. To achieve higher signal strength and better linearity, we investigated stripline- and button-type beam position monitor (BPM) and designed the BPMs with CST Particle Studio. We have fabricated a button-type BPM. We tested 10 BPMs by using a wire test stand to achieve the characterization of each BPM, including the calibration factor with single-pass H electronics of I-Tech. The developed wire test stand has a stretched wire and is movable in the 2D plane with servomotors. In this paper, we present the results of the design, fabrication, and off-line test of a button-type BPM for a low- β , heavy-ion beam. [ABSTRACT FROM AUTHOR]

Diamond X‐ray detectors with conducting nitrogen‐incorporated ultra‐nanocrystalline diamond (N‐UNCD) films as electrodes were fabricated to measure X‐ray beam flux and position. Structural characterization and functionality tests were performed for these devices. The N‐UNCD films grown on unseeded diamond substrates were compared with N‐UNCD films grown on a seeded silicon substrate. The feasibility of the N‐UNCD films acting as electrodes for X‐ray detectors was confirmed by the stable performance in a monochromatic X‐ray beam. The fabrication process is able to change the surface status which may influence the signal uniformity under low bias, but this effect can be neglected under full collection bias. [ABSTRACT FROM AUTHOR]

In the framework of the future linear collider collaboration (CLIC, ILC), non-intercepting beam monitoring instruments are under development for very low emittance and high charge density beams. Optical diffraction radiation (ODR) was studied and developed during the last years focussing on beam size measurements. We propose in the paper to consider the use of diffraction radiation for ultra relativistic beams as position monitors with applications for the centering of scrapers, collimators and targets with high resolution. We present the experimental results obtained using small aperture slits on the ATF2 extraction beam line at KEK and on the Cornell Electron Storage Ring with 1.2 GeV and 2.1 GeV electrons respectively. [ABSTRACT FROM AUTHOR]

The beam position monitor (BPM) is an essential component for the PEFP 100-MeV linac's commissioning. A prototype stripline-type linac BPM was designed for this purpose. The electrode aperture is 20 mm in diameter, and the electrode is 25 mm long, so it can be installed between Drift Tube Linac (DTL)101 and DTL102, which is the shortest distance. One end of the electrode is connected to the Sub Miniature Type A (SMA) feed through for signal measurement, and the other end is terminated as a short. The signal amplitude of the fundamental component was calculated and compared with that of the second harmonic component. The designed BPM was fabricated and a low-power RF test was conducted. In this paper, the design, fabrication and low power test of the BPM for the PEFP linac are presented.