Beamline Components Research Articles

Vacuum System Optimization for EAST Neutral Beam Injector

The neutral beam injector (NBI) generates a high-energy ion beam and neutralizes it, and then relies on drift transmission to inject the formed neutral beam into the fusion plasma to increase the plasma temperature and drive the plasma current. In order to better cooperate with the Experimental Advanced Superconductive Tokamak (EAST), part of the Chinese major national scientific and technological infrastructure, in carrying out long-pulse high-parameter physics experiments of 400 s and above, this paper considers the optimization of the current design and operation of the NBI beam line with a pulse width of 100 s. Based on an upgraded and optimized NBI vacuum chamber and the structure of the beam-line components, the gas-source characteristics under the layout design of the NBI system are analyzed and an NBI vacuum system that meets relevant needs is designed. Using Molflow software to simulate the transport process of gas molecules in the vacuum chamber, the pressure gradient in the vacuum chamber and the heat-load distribution of the low-temperature condensation surface are obtained. The results show that when the NBI system is dynamically balanced, the pressure of each vacuum chamber section is lower than the set value, thus meeting the performance requirements for the NBI vacuum system and providing a basis for subsequent implementation of the NBI vacuum system upgrade using engineering.

Investigation into activation of accelerators at various synchrotron radiation facilities in Japan

ABSTRACT To establish systematic guidelines for accelerator decommissioning, a large-scale activation survey was conducted at representative synchrotron radiation facilities in Japan. The neutron flux during accelerator operation was measured with various dosimeters. A Monte Carlo simulation was conducted for some facilities to verify the special neutron distribution and their spectra. Beam loss points, reflected as high-dose-rate areas, were identified by a whole-beamline survey with a survey meter, and the generated radionuclides and their activity were determined with a lanthanum bromide (LaBr3) scintillation spectrometer. In all facilities, the activation level was quite low. Whole-beamline tunnels made of concrete were not activated, and no radionuclides were detected except for natural nuclides. In addition, almost all beamline components were either not or minimally activated. Although the acceleration energy is very high for radiation synchrotron facilities, the generation of radioactive waste would be very low.

The design, construction, and commissioning of the KATRIN experiment

The KArlsruhe TRItium Neutrino (KATRIN) experiment, which aims to make a direct and model-independent determination of the absolute neutrino mass scale, is a complex experiment with many components.More than 15 years ago, we published a technical design report (TDR) [1] to describe the hardware design and requirements to achieve our sensitivity goal of 0.2 eV at 90% C.L. on the neutrino mass.Since then there has been considerable progress, culminating in the publication of first neutrino mass results with the entire beamline operating [2].In this paper, we document the current state of all completed beamline components (as of the first neutrino mass measurement campaign), demonstrate our ability to reliably and stably control them over long times, and present details on their respective commissioning campaigns.

A statistical reconstruction model for absorption CT with source uncertainty *

Reconstruction methods for computed tomography are often based on the assumption that the source intensity and the detector response are known and static. In practice, however, both are unknown and must be estimated. An estimate of the combined source intensity and detector response is typically obtained by acquiring a number of so-called flat-field measurements, but this approach is oblivious to intensity drift, e.g. due to source instabilities, vibrating beamline components, etc. Discrepancies between the estimated response and true response can lead to severe artifacts in the reconstruction, especially for dose- and/or time-limited experiments. We propose a new, extended reconstruction model that jointly estimates the reconstruction, the detector response, and the (possibly time-varying) source intensity. We demonstrate through simulated experiments that the proposed reconstruction model leads to reconstructions with significantly reduced artifacts.

Contrast - a lightweight Python framework for beamline orchestration and data acquisition.

The emergence of fourth-generation synchrotrons is prompting the development of new systems for experimental control and data acquisition. However, asgeneral control systems are designed to cover a wide set of instruments andtechniques, they tend to become large and complicated, at the cost of experimental flexibility. Here we present Contrast, a simple Python framework for interacting with beamline components, orchestrating experiments and managing data acquisition. The system is presented and demonstrated via its application at the NanoMAX beamline of the MAX IV Laboratory.

Optimization-oriented modelling of neutral beam injection for EU pulsed DEMO

Neutral beam injection (NBI) is one of the auxiliary power systems considered for the EU DEMO pulsed plasma (‘DEMO1’). In this paper, we discuss the characteristics of optimized NBI in terms of the DEMO1 requirements, relating physics and engineering contexts in a novel parameter range compared to current NBI systems and in a larger plasma volume than ITER. Different injection options are investigated to account for various concepts discussed in the literature. The investigation is carried out using a wide range of sensitivity studies by means of the METIS 0.5D transport code and ASCOT Monte Carlo simulations of injected neutral-beam particles. This investigation has generated a series of recommendations for the NBI design, contributing to the system optimization process. We show how tangential injection aimed at the plasma core, with an energy 800 keV, is recommended to maintain high fusion power performance and fulfill the requirements for bulk heating. Compliance with engineering constraints on the NBI design, e.g., the least interference with breeding blanket modules or compatibility with solutions for the beamline components, imposes some restrictions when discussing the beam geometry. The minimum density at which an NBI can be safely operated without harmful shine-through losses is investigated for different injection energies and compared to the ITER case. The NBI operational window for DEMO is shown to be significantly extended to transient, low-density phases, also highlighting the importance of NBI systems designed for modular energy and power output. NBI can therefore sustain the plasma during a considerable portion of the transient phases, i.e., the current ramp-up and ramp-down phases. The final decision on the DEMO heating mix will be made on the basis of system operability and performance: the optimized NBI is shown to be a suitable and effective option for the EU DEMO inductive scenario.

The beamline for the ITER heating neutral beam injectors: A case study for development and procurement of high heat flux components

The ITER Neutral Beam Test Facility includes development, testing, and optimization of the full prototype of the ITER Heating Neutral Beam injectors (HNBs), named MITICA. A 40 MW precursor D−/H− beam will be produced and then neutralised and filtered along the beamline, aiming to obtain 18 MW D0/H0 beam at the calorimeter and 16.5 MW during operation into the plasma. A gas neutraliser and an electrostatic residual ion dump will process the beam together with a calorimeter, necessary for commissioning and conditioning in HNBs, and for beam dumping in MITICA.The three beamline components are formed by in-vacuum actively cooled panels made of seamless CuCrZr drilled bars and swirl tubes without armour directly exposed to beam particles. Heat fluxes up to 20 MW/m2 will be exhausted through water-cooled channels operating up to 1 h in subcooled boiling. Critical heat flux and fully developed boiling were verified using semi-empirical correlations validated for divertor fingers and limiter plates. These correlations were implemented in 1D–3D customised codes simulating local nucleate boiling heat transfer conditions. Moreover, the panels were verified against creep-fatigue by simulating plastic strains under the expected cyclic thermal loads. During beam operation, the beamline components performance will be monitored using 700 embedded thermo-mechanical sensors for protection and for ITER HNBs requirement verification.The design solutions were developed consistently with intermediate inspections during assembly to limit repairs, modification of compensation members for tolerance control in dimensional chains, remote handling operations, and nuclear radiation level at ITER. The design of coolant-vacuum barriers was adapted to implement corrosion, welding, and inspection requirements.Prototypes implementing different manufacturing solutions were produced by three potential suppliers of MITICA beamline components. This strategy led to an early assessment of production reliability and cost-effective manufacturing techniques based on proven industrial expertise. Then, the supplier selected for the procurement of the beamline components will be supported with addressed performances during the follow up.

Final design of electrostatic probes for MITICA beam line components

MITICA is the full-scale prototype of ITER Neutral Beam Injector (NBI), currently under construction in Padova, Italy. In this facility, a 40 A beam of negative deuterium ions will be accelerated to 1 MeV and then neutralized. The emerging beam, after the removal of residual ions, will be dumped onto the calorimeter (up to 17 MW are expected). In each component of the beam-line, monitoring of the presence of plasma and its parameters is crucial: with this aim, various types of electrostatic probes will be installed along the MITICA beam-line.The Neutralizer and the Electric Residual Ion Dump (ERID) panels will be equipped with pairs of Langmuir probes at different vertical and axial positions, with the possibility to be set in single or double probe configurations and to provide local floating potential, ion density and electron temperature measurements. In the neutralizer, the probes will provide information about the beam collisional processes, in view of a neutral fraction optimization. In the ERID, the objective of the probes is to confirm the absence of plasma, which otherwise might invalidate the deflection properties of the device. In the calorimeter, biased electrodes will collect the secondary emission electrons produced by the beam collisions with the cooling tube surfaces. The electrodes will provide vertical and horizontal profiles of the beam at the calorimeter, to study its horizontal steering, divergence and uniformity.Four different probe designs have been developed to fulfill specific scientific and mechanical constrains at the different positions. In this contribution, the realization of the four prototypes, one for each probe, together with a mock-up of the relative housing panel, is described. Problems or difficulties emerged during the manufacturing of specific elements or during the assembly of the probes have been identified and fixed and the prototypes tested. The final design is, thus, presented.

Survey Methodology for the Activation of Beamline Components in an Electrostatic Proton Accelerator

Survey Methodology for the Activation of Beamline Components in an Electrostatic Proton Accelerator

Parasitic neutron beam monitoring: Proof of concept on gamma monitoring of neutron chopper phases

Neutron beam monitors are an essential diagnostic component of neutron scattering facilities. They are used to measure neutron flux, calibrating experiments performed on the instruments, allowing measurement of facility performance, understanding of the effect on the neutrons of beam-line components (such as choppers), calibration of detectors and tracking of beam stability. Ideally beam monitors should not perturb the beam. Previous work shows commercial beam monitors attenuate the beam by a few percent in the worst case due to the 1–2 mm thick aluminium entrance and exit windows and the material inside. Parasitic methods of neutron beam diagnostics, where there is no beam monitor directly in the beam, would be preferable. This paper presents the concept of a parasitic method of monitoring the beam which can be used for neutron chopper phasing. This is achieved by placing a gamma detector close to a rotating chopper and measuring a signal proportional to the flux absorbed by the chopper. Neutrons interact with the boron absorber on the chopper disc leading to gamma emission at 480 keV. Detection of these gamma rays is used to determine the chopper phasing and timing. Potentially information on the flux of the beamline can be extracted. Results from a proof of concept implementation show that diagnosis of neutron chopper phases is feasible.

A ray-tracing algorithm for ab initio calculation of thermal load in undulator-based synchrotron beamlines.

The OASYS suite and its powerful integration features are used to implement a ray-tracing algorithm to accurately calculate the thermal load in any component of an undulator-based synchrotron beamline. This is achieved by sampling and converting the SRW source of a given energy into a Shadow source and using the latter code to ray trace the full beamline. The accuracy of the algorithm is proved by reconstructing the full undulator radiation distribution through an aperture and comparing the result with direct calculaton of the total power usingSRW. The algorithm is particularly suited to analyze cases with complex beamline layouts and optical elements, such as crystals, multilayers, and compound refractive lenses. Examples of its use to calculate the power load on elements of two of the feature beamlines at the Advanced Photon Source Upgrade Project and a comparison of the results with analytical calculations arepresented.

A passive hutch-cooling system for achieving high thermal-stability operation at the Nanoprobe beamline, Diamond Light Source.

The development of low-emittance storage rings and the rapid developments in nano-optics and imaging techniques are leading to decreasing X-ray spot sizes and increasing requirements on the environmental and mechanical stability of beamline components. In particular, temperature stability in the experimental hutches is critical to minimize uncontrolled displacements caused by thermal expansion and ensure consistent performance. Here, the design and thermal performance of the experimental hutches of the Nanoprobe beamline at Diamond Light Source are described, where a standard deviation of the room temperature down to 0.017°C over extended periods is demonstrated. The rooms are kept at constant temperature using water-cooled radiant panels which line the ceiling and walls. Radiant panels are relatively common in high-end electron microscopy rooms, but this is the first demonstration of their use for fine temperature control in an X-ray hutch and may provide a useful basis for future upgrades at upcoming low-emittance sources.

The Liquid Argon In A Testbeam (LArIAT) experiment

The LArIAT liquid argon time projection chamber, placed in a tertiary beam of charged particles at the Fermilab Test Beam Facility, has collected large samples of pions, muons, electrons, protons, and kaons in the momentum range 0∼30–0140 MeV/c. This paper describes the main aspects of the detector and beamline, and also reports on calibrations performed for the detector and beamline components.

The current status of time-resolved XAS beamline at SLRI and application on in situ experiments

Time-resolved X-ray absorption spectroscopy (TRXAS) beamline (BL2.2) was constructed to utilize a synchrotron radiation produced by a 1.2 T bending magnet from a 1.2 GeV storage ring at the Synchrotron Light Research Institute (SLRI), Thailand. The main optical component of the TRXAS beamline is an energy dispersive monochromator (EDM) which was donated by the University of Bonn, Germany. Using the energy-dispersive scheme with a position-sensitive detector, the beam size at the sample position can be small and have a fast detection speed in the XAS spectrum. At BL2.2, XAS measurement can be performed in the transmission mode using a 1024-pixel position-sensitive detector (PSD) and x-ray scintillator. Currently, the maximum measurable x-ray energy has been extended to 12 keV for the Pt L3-edge EXAS measurement. Due to the advantages of the energy-dispersive setup, this beamline has focused on in-situ XAS experiments. In this review, the researchers summarize the developments of experimental tools to characterize catalysts, Li-ion batteries, and thin film using TRXAS to determine their electronic properties and structure under applied conditions.

A five-axis parallel kinematic mirror unit for soft X-ray beamlines at MAX IV

With the introduction of the multi-bend achromats in the new fourth-generation storage rings the emittance has decreased by an order of magnitude resulting in increased brightness. However, the higher brightness comes with smaller beam sizes and narrower radiation cones. As a consequence, the requirements on mechanical stability regarding the beamline components increases. Here an innovative five-axis parallel kinematic mirror unit for use with soft X-ray beamlines using off-axis grazing-incidence optics is presented. Using simulations and measurements from the HIPPIE beamline at the MAX IV Laboratory it is shown that it has no Eigen frequencies below 90 Hz. Its positioning accuracy is better than 25 nm linearly and 17-35 µrad angularly depending on the mirror chamber dimensions.

IMAGINE: The neutron protein crystallography beamline at the high flux isotope reactor.

IMAGINE is a high intensity, quasi-Laue neutron crystallography beamline developed at the 85MW High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). This state-of-the-art facility for neutron-diffraction enables neutron protein structures to be determined at or near atomic resolutions from crystals with volumes of <1mm3 and unit cell edges of <150Å. The beamline features include elliptical focusing mirrors that deliver neutrons into a 2.0×3.2mm2 focal spot at the sample position, and variable short and long wavelength cutoff optics that provide automated exchange between multiple wavelength configurations. The beamline is equipped with a single-axis goniometer, neutron-sensitive cylindrical image plate detector and room temperature and cryogenic sample environments. This article describes the beamline components, the diffractometer and the data collection and data analysis protocols that are used, and outlines the protein deuteration, crystallization and conventional crystallography capabilities that are available to users at ORNL's neutron facilities. We also present examples of the scientific questions being addressed at this beamline and highlight important findings in enzyme chemistry that have been made possible by IMAGINE.

DeepCentering: fully automated crystal centering using deep learning for macromolecular crystallography.

High-throughput protein crystallography using a synchrotron light source is an important method used in drug discovery. Beamline components for automated experiments including automatic sample changers have been utilized to accelerate the measurement of a number of macromolecular crystals. However, unlike cryo-loop centering, crystal centering involving automated crystal detection is a difficult process to automate fully. Here, DeepCentering, a new automated crystal centering system, is presented. DeepCentering works using a convolutional neural network, which is a deep learning operation. This system achieves fully automated accurate crystal centering without using X-ray irradiation of crystals, and can be used for fully automated data collection in high-throughput macromolecular crystallography.

Exact solution of multi-bunch instabilities for ultra-relativistic constant energy bunches in particle accelerators

In particle accelerators the multi-bunch beams of charged particles excite electromagnetic wakefields in the accelerating cavities and other beam-line components. These wakefields may cause instability in the longitudinal and transverse motion of these bunches leading to the beam loss. Thus, the analysis of such multi-bunch effects is critical in any accelerator design. Here, we present a new analytical method to exactly describe the multi-bunch transverse instabilities for ultra-relativistic electron bunches coasting at a constant energy through a uniform beam-focusing system. We discuss two cases: same bunch energy for all bunches and different energy from bunch to bunch. For the first case the solution is based on a special class of polynomials, while for the second case the solution is a finite sum of sinusoidal functions. We demonstrate the use of this approach with examples and compare the results of a numerical differential equation solver against our rigorous results. Our method could also be applied to the analysis of beam breakup within a single bunch. This approach can be extended beyond accelerator physics to study other many-body systems where an body is affected by only the preceding bodies.

Stitching techniques for measuring X-ray synchrotron mirror topography.

Optical metrology and polishing techniques are continuously evolving to satisfy the increasingly stringent specifications required for X-ray optical components for synchrotron and free-electron laser light source beamlines. For both spherical and aspherical geometries, the most demanding applications may have target residual figure errors close to 1 nm. To achieve such specifications and maintain them in the optomechanical mount, it is critical to develop methods capable of measuring the topography of the optical surface over the clear aperture of the mirror. The European Synchrotron Radiation Facility optical metrology laboratory has developed a stitching tool initially aimed at measuring long flat mirrors up to 1 m long with a Fizeau interferometer. The system is routinely used providing 2D maps of the optical surface. The instrument capabilities have been extended to characterize moderately curved optics using a transmission flat element, and results obtained on a high quality spherical mirror with 120 m of radius of curvature are presented. As a novel approach of stitching application, the technique has been used to improve the measurement accuracy of the Fizeau interferometer when measuring short plane mirrors. Acquisition of 2D topographies on a short plane mirror by micro-stitching interferometry is also presented and discussed.

A conceptual system design study for an NBI beamline for the European DEMO

Neutral Beam Injection (NBI) as a robust, established heating and current drive (CD) method is considered for the European DEMO. Like on ITER, an NBI system for DEMO will have to use negative ions as the neutralisation efficiency of positive ions vanishes at the required ≥800 keV beam energy. The required specifications of an NBI on DEMO go significantly beyond those on ITER, particularly when NBI is chosen to provide bulk current drive for a steady-state tokamak DEMO. The NBI beamline's power efficiency, on ITER only about 27%, needs to be significantly increased to arrive at a tolerable recirculating power fraction. Envisaged solutions are the addition of energy recovery for the residual ions to a gas neutraliser or the replacement of the gas neutraliser by a photoneutraliser or a beam-driven plasma neutraliser. None of these concepts has been demonstrated on a relevant scale. In this article we outline our approach to a comprehensive system design study in order to explore a broad range of options for each beamline component and their mutual dependences, and we focus on the central role that the choice of the neutraliser concept – where needed in combination with energy recovery – plays for the layout of the whole beamline.