Quadrupole Focusing Research Articles

Boosting the sensitivity of single photon ionization time-of-flight mass spectrometry using a segmented focus quadrupole-ion guide

Single photon ionization time-of-flight mass spectrometry (SPI-TOF-MS) is a powerful analytical technique for real-time detection of trace VOCs. However, efficient ion transmission within the ionization chamber has always been a challenging issue in SPI-TOF-MS. In this study, a novel ion guide termed the Segmented Focus Quadrupole Ion Guide (SFQ-IG) was introduced for SPI-TOF-MS. The SFQ-IG device consists of 12 printed circuit boards (PCB), each containing four quarter-ring electrodes with inner diameters progressively decreasing from 26 to 4 mm. The simulation results demonstrated that SFQ-IG exhibited superior ion transmission efficiency than both ion funnel (IF) field and direct current-only (DC-only) field. By integrating into a SPI-TOF-MS, this ion guide was optimized in terms of the ionization source pressure, direct current gradient, and radio frequency amplitude. Further comparative experiments demonstrated that the SPI-TOF-MS with the SFQ-IG exhibited higher sensitivity than both the IF field (1.3–7.4 times) and DC-only field (3.5–8.8 times) for the test VOCs. The improvements in limit of detection (LOD) with the SFQ-IG ranged from 1.6 to 5.3 times compared to the DC-only field for the test VOCs. Fabricated using PCB technology, the SFQ-IG is characterized by its cost-effectiveness, compact size, and high transmission efficiency, facilitating its integration into other mass spectrometers.

Earthquake Measurements and Those Analysis on IR Components and Belle II Detector in KEK

Earthquakes frequently occur in Japan. Even though countermeasures are thoroughly considered and well executed, earthquakes still impact facilities and experimental devices. The large relative displacements induced by an earthquake can damage beam pipe bellows and interfere with sub-detectors by causing the tolerance between them to disappear. Even magnet quenches have been triggered by induced voltages caused by the relative displacements between the superconducting solenoids (i.e., the detector solenoid and the compensating solenoids surrounding the final focus quadrupole magnets, or QCSs). In response, we installed acceleration sensors on the Belle II detector and mounted gap sensors on the QCSs to measure the relative displacements. These measurements enabled the characteristics of the earthquakes that have affected the Belle II detector to be analysed. Response spectrum analyses (RSAs) of the Belle II detector were conducted to evaluate the impact of earthquakes according to the ground motion measurements. We then compared the measurements to the RSA results, which led to an idea for a countermeasure.

Design of the Prototype of the Radio Frequency Quadrupole Sections for the Compact Neutron Source DARIA

The DARIA compact neutron source project based on a linear resonant proton accelerator is aimed at creating a serial facility capable of providing the Russian scientific community with pulsed neutron beams with intensities comparable to those of research nuclear reactors. The absence of fissile material makes it possible to significantly reduce the radiation safety requirements for such installations and, consequently, to place them at the site of leading scientific centers and universities that train specialists in the field of neutron physics. Under a grant from the Ministry of Science and Higher Education, key elements of the facility are being developed. The design and sequence of manufacturing for a full-scale model of an accelerator section with radio frequency quadrupole focusing and a resonator with drift tube linac are presented.

Phase Space Reconstruction from Accelerator Beam Measurements Using Neural Networks and Differentiable Simulations.

Characterizing the phase space distribution of particle beams in accelerators is a central part of understanding beam dynamics and improving accelerator performance. However, conventional analysis methods either use simplifying assumptions or require specialized diagnostics to infer high-dimensional (>2D) beam properties. In this Letter, we introduce a general-purpose algorithm that combines neural networks with differentiable particle tracking to efficiently reconstruct high-dimensional phase space distributions without using specialized beam diagnostics or beam manipulations. We demonstrate that our algorithm accurately reconstructs detailed 4D phase space distributions with corresponding confidence intervals in both simulation and experiment using a limited number of measurements from a single focusing quadrupole and diagnostic screen. This technique allows for the measurement of multiple correlated phase spaces simultaneously, which will enable simplified 6D phase space distribution reconstructions in the future.

Frequency scanning interferometry based deformation monitoring system for the alignment of the FCC-ee machine detector interface

In a particle accelerator, two particle beams are accelerated and collided at one or several physics detectors. The machine detector interface (MDI) is the place where the accelerator ring is linked to the physics detector. It is the area where the alignment requirements are the most stringent, and the MDI of the lepton version of the future circular collider (FCC-ee) is no exception. It will implement a complex design and alignment requirement for typical components in the MDI are of the order of 30 μm. Until now, no working solutions have been proposed for the alignment of such MDI. In this contribution, two different systems are studied: the Surveillance d’Ouvrages par Fibre Optique (Structural Monitoring by Optical Fibers, SOFO) and the in-lined multiplexed and distributed frequency scanning interferometry (FSI). Both systems allow individual and simultaneous distance measurements of multiple portions along a fiber, and a new system using the FSI technology is proposed for the alignment monitoring. Using a network of helical shaped fiber allows the measurement of deformations if a sufficient amount of fibers is placed on the cylinder. With a sensor measurement accuracy of 1 μm, 3D coordinates of points at the end of a 4 m long and 0.25 m radius cylinder (FCC-ee MDI dimensions) can be determined at an accuracy under 5 μm. This system will provide a link between the alignment of the final focusing quadrupoles and the rest of the machine.

Acceleration and crossing of transition energy investigation using an RF structure of the barrier bucket type in the NICA accelerator complex

The dynamic of longitudinal motion in Barrier Bucket RF structure is considered. To preserve the stability of the proton beam during the acceleration to the experiment energy it is necessary to cross the transition energy and a rapid jump of transition energy is possible. The influence of the second-order slip factor is taking into account. The dynamic aperture is investigated for various gradients of focusing quadrupoles and corresponding working points which is necessary for transition crossing.

Increased Sensitivity in Proton Transfer Reaction Mass Spectrometry by Using a Novel Focusing Quadrupole Ion Funnel.

Sensitivity enhancement in proton transfer reaction mass spectrometry (PTR-MS) is an important development direction. We developed a novel drift tube called a focusing quadrupole ion funnel (FQ-IF) for use in PTR-MS to improve the sensitivity. The FQ-IF consists of 20 layers of stainless steel electrodes, and each layer has 4 quarter rings. The first 6 layers have a constant inner hole diameter of 22 mm; the latter 14 layers taper the inner diameter down to 8 mm. The FQ-IF drift tube can also operate in the direct current (DC) mode (similar to a conventional drift tube) and ion funnel (IF) mode (similar to a conventional ion funnel drift tube) by changing the voltage loading method. The simulation results show that the transmission efficiency of the FQ-IF is significantly improved compared to that of the other two modes. Further experiments show that the product ions of limonene tend to convert into smaller m/z fragment ions at higher voltages for the DC and IF modes. However, unlike the DC and IF modes, the distribution of product ions is stable at higher voltages for the FQ-IF. In other words, a higher RF voltage for the FQ-IF will not increase the collision energy of ions. In addition, the improvements in sensitivity for the FQ-IF range from 13.8 to 87.9 times compared to the DC mode and from 1.7 to 4.8 times compared to the IF mode for the 12 test compounds. The improvements in the limit of detection (LOD) for the FQ-IF range from 2.7 to 35.7 times compared to the DC mode. The FQ-IF provides a valuable reference for improving the sensitivity of PTR-MS and other mass spectrometers.

APFRFQ – A SIMULATION ENVIRONMENT FOR THE DEVELOPMENT OF HIGH-CURRENT LINEAR ION ACCELERATORS WITH RF FOCUSING

Presented is an interactive environment, APFRFQ, for calculating linear accelerators based on rf field focusing of different types, namely, alternating phase focusing (APF), rf quadrupole focusing (RFQ) and a combination of previous two methods (APF&RFQ). The APFRFQ environment is capable of performing the following tasks in the interactive mode: setting the parameters of the accelerating gaps, calculating the accelerating-focusing channels of linear accelerators taking into account the real geometry of the electrodes, performing numerical simulation of particle dynamics in the calculated channels with the space charge forces taking into account, matching the input parameters of the beam with the given six-dimensional phase distribution and the accelerating structure.

Final design of the cryostat for the high luminosity LHC magnets

The high luminosity LHC project (HL-LHC) aims at increasing proton collisions by a factor of ten whilst extending physics exploitation until 2035. Its performance will rely on new focusing quadrupoles, beam separation dipoles and corrector magnets with large apertures to be installed on both sides of the ATLAS and CMS experiments. A dedicated cryostat design of about 1 m in diameter was developed for operation of these magnets at 1.9 K, comprising the required cryogenic circuits, interconnects, supports, insulation, and instrumentation systems. Six cryostats with various lengths in the range of 8 to 11 m are required on each side of the interaction points to house the triplet magnets, correctors and the first separation dipole. These cryostats will be linked through flexible interconnects to form a continuous vacuum insulation and cryogenic system of about 60 m in length. The second rearmost separation dipole requires a stand-alone cryostat of 15 m in length but nevertheless features common design principles. We present the design of these cryostats, from a conceptual stage towards the final design. Assembly aspects are also addressed, including a modular approach affording flexibility and simplification of the manufacturing and assembly processes.

Tapered helical undulator system for high efficiency energy extraction from a high brightness electron beam

In this paper we discuss the design choices and construction strategy of the tapered undulator system designed for a high energy extraction efficiency experiment in the ultraviolet region of the electromagnetic spectrum planned for installation at the Argonne National Laboratory Linac Extension Area (LEA) beamline. The undulator is comprised of 4 sections pure permanent magnet Halbach array separated by short break sections, each one of them housing a focusing quadrupole doublet and a phase shifter. The quadrupoles use a novel hybrid design which allows one to vary the gradient and match the beam transversely. The undulator tapering profile is optimized to maximize the energy conversion efficiency from a 343 MeV 1 kA beam into coherent 257.5 nm radiation taking into account the longitudinal current profile generated by the linac.

Beam-dynamics design of a 2 MeV/u heavy-ion IH-DTL with electromagnetic quadrupole structure

The interdigital H-mode (IH) drift tube linac (DTL) with an electromagnetic quadrupole (EMQ) structure combines an IH-DTL acceleration structure with a quadrupole focusing–defocusing (FD) lattice and can achieve a high acceptance when high shunt impedance is ensured. Between the radio frequency quadrupole (RFQ) and IH-DTL, the IH-EMQ dynamics allows only one quadrupole magnet to match the two structures directly, which is different from KONUS (Kombinierte Null Grad Struktur, combined zero-degree structure) and alternating-phase focusing (APF) dynamics. To match KONUS or APF DTL with the RFQ, at least three quadrupole magnets are required. This paper describes the design process of the IH-EMQ beam dynamics and applies and verifies the method by applying it to design a 2MeV/u heavy-ion IH-DTL with the help of detailed simulation and analysis. With the input energy of 400keV/u, the DTL accelerates particles with a charge-to-mass ratio as low as 1/6.5. The normalized root mean square emittance increases by 7%. The IH-DTL with the IH-EMQ dynamics design offers a normalized transverse acceptance (99% particles) of 3.89(x)/3.56(y)πmm⋅mrad while preserving an effective shunt impedance of 87MΩ/m.

3D Magnetic Field Analysis of LHC Final Focus Quadrupoles with Beam Screen

3D Magnetic Field Analysis of LHC Final Focus Quadrupoles with Beam Screen

Magnetic Measurements at Warm of the First FCC-ee Final Focus Quadrupole Prototype

The first FCC-ee final focus quadrupole prototype has been designed, manufactured, assembled and tested at warm. The prototype is a single aperture quadrupole magnet of the CCT type. One edge of the magnet was designed with local multipole cancellation, whereas the other was left with the conventional design. An optimized rotating induction-coil sensor was used. A technique was developed to take into account field distortions due to the environment of the test and distinguish them from magnet effects, demonstrating an excellent field quality for the prototype.

Untargeted lipidomics analysis of Mori Fructus polysaccharide on acute alcoholic liver injury in mice using ultra performance liquid chromatography-quadrupole-orbitrap-high resolution mass spectrometry

Ethnopharmacological relevanceMori Fructus (MF) is a traditional Chinese medicine with long application history, which has protective effects on liver diseases. Mori Fructus polysaccharide (MFP) is one of the active ingredients of MF and possesses therapeutic effects against acute alcoholic liver injury. Recent researches have reported that the therapeutic effects of MFP might be related to the regulation of several lipid metabolic pathways. However, the mechanism of lipid metabolism was still unclear. Aim of the studyThis study aimed to investigate the regulatory effect of MFP on lipid metabolism in mice with acute alcoholic liver injury, and to enrich the application of its hepatoprotective effect. Materials and methodsFifty Specific Pathogen Free (SPF) Kunming (KM) male mice were divided into five groups randomly, including normal control group, model group, bifendate positive group (220 mg/ kg), MFPA1 group (50 mg/ kg) and MFPB1 group (50 mg/ kg). A model of acute alcoholic liver injury was established by treating the mice with ethanol. The liver sections were processed and histopathological changes was observed with hematoxylin and eosin staining. The secretion levels of biochemical indexes in the liver and serum were assayed by ELISA. The untargeted lipidomics analysis was performed on a Q Exactive Focus quadrupole orbitrap high resolution mass spectrometry coupled with a Dionex Ultimate 3000 RSLC (HPG) ultra-performance liquid chromatography (UPLC-Q-Orbitrap-HRMS) system (Thermo Fisher Scientific), with a HESI ionization source. ResultsIt was observed that abnormal glutamic-pyruvic transaminase enzyme (ALT), glutamic-oxaloacetic aminotransferase (AST), triglyceride (TG), superoxide dismutase (SOD), and malondialdehyde (MDA) concentrations were ameliorated after irrigation of MFP or bifendate. Histopathology examination showed that intragastric infusion of MFP can be helpful in the repair of damaged liver in mice. The multivariate analysis of hepatic lipids showed segregation of ethanol-fed groups from the normal controls. After the comparison of mass spectra, 10 lipids were found to have different content in the normal control group and the model group. Differential lipids that were increased by ethanol exposure included fatty acids, phosphatidylcholine, and lyso-phosphatidylethanolamine, whereas lyso-phosphatidylcholine decreased. Among them, 4 lipids almost returned to the level of normal mice after MFP treatment. ConclusionThe therapeutic effect of MFP on acute alcoholic liver injury may be achieved by regulating a variety of metabolic pathways, including linoleic acid metabolism, α - linolenic acid metabolism, and glycerolphospholipid metabolism.These results revealed that MFP efficiently exerted hepatoprotective benefits, and its potential effect was associated with the amelioration of lipid metabolism.

Beam optics in nuclear microprobe: A review

The beam optics in a nuclear microprobe is considered on the basis of quality criteria for focusing systems. In this consideration, empirical criteria with dominant chromatic or intrinsic spherical aberrations are used. In a more general criterion, where all aberrations can be taken into account, the maximum acceptance for a fixed beam spot size on the target is used. Another criterion, that is closest to an experiment, is based on the condition of the minimum spot size at a fixed beam current and takes into account the nonuniform distribution of ions in the phase volume. This review summarizes the studies of various types of quadrupole focusing systems and implies the need for further development of the nuclear microprobe by using aberration correctors and a compact system. The analysis of the influence of various aberrations on the resolution of a nuclear microprobe is conducted with special attention paid to the positioning aberrations in separated quadrupole probe-forming systems. It is demonstrated why integrated multiplets of quadrupole lenses are preferred in such systems. Methods to process experimental results for an adequate determination of the spot size on the target are considered.

Simulation study of the long range wakefield induced multi-bunch instability in the China X-ray free electron laser

A 1.3GHz superconducting accelerator (SC) which can generate 32 bunches (0.2nC/bunch) with an interval of 2.3ns has been designed for the China free electron laser (CXFEL), the effects of the long range wakefield in the superconducting cavities are analyzed in this paper. In our simulation results, the fundamental mode of the longitudinal wakefield (beam loading) may result in an energy droop of 844eV/cavity to the bunch train, and may also disturb the bunch compression process by altering the energy chirp. The effects of the transverse wakefield are studied by injecting all bunches with an initial position error of 200µm, and also by applying a random misalignment of σΔx,y=100µm (in Gaussian distribution) to the cavities and the focusing quadrupoles, then the trajectory of the bunch train is corrected with horizontal and vertical correctors. In both cases the transverse wakefield induced bunch to bunch variation are negligible, whereas the misalignment may result in emittance degradation to all bunches.

Fabrication and cold test of prototype of spatially periodic radio frequency quadrupole focusing linac

A 325 MHz aluminum prototype of a spatially periodic RF quadrupole focusing linac was developed at the Institute of Modern Physics, Chinese Academy of Sciences, as a promising candidate for the front end of a high-current linac. It consists of an alternating series of crossbar H-type drift tubes and RF quadrupole sections. Owing to its special geometry, cavity fabrication is a major hurdle for its engineering development and application. In this paper, we report the detailed mechanical design of this structure and describe its fabrication process, including machining, assembly, and inspection. The field distribution was measured by the bead-pull technique. The results show that the field errors of both the accelerating and focusing fields are within an acceptable range. A tuning scheme for this new structure is proposed and verified. The cold test process and results are presented in detail. The development of this prototype provides valuable guidance for the application of the spatially periodic RF quadrupole structure.

High dimensional characterization of the longitudinal phase space formed in a radio frequency quadrupole

Modern accelerator front ends almost exclusively include radio-frequency quadrupoles for initial capture and focusing of the low-energy beam. Dynamics in the RFQ define the longitudinal bunch parameters. Simulation of the SNS RFQ with PARMTEQ seeded with a realistic LEBT distribution produces a 2.5 MeV, 40 mA H- beam with root-mean-square emittance of 130 deg-keV. In measurement, a detailed characterization of the longitudinal phase space is made, including a novel study of the dependence of longitudinal emittance on transverse coordinates. This work introduces a new virtual slit technique that provides sub-slit resolution in an energy spectrometer as well as an approach for visualizing 4D phase space data. Through simulation and measurement, the RFQ-formed bunch is confirmed to have significant internal correlated structure. The high-dimensional features are shown to be in qualitative agreement. However, the measured rms emittances are up to 30% lower than predicted, closer to the design value of 95 deg-keV.

Harmonic Suppression Study on Twin Aperture CCT Type Superconducting Quadrupole for CEPC Interaction Region

Iron-free twin-aperture superconducting quadrupole in the interaction region is a key technology to increase the luminosity of high-energy future colliders, such as the circular electron-positron collider that China will build in the next ten years with a center-of-mass energy of 240 GeV and a small crossing angle of 33 mrad in the interaction region. The final focusing quadrupole QD0, which is 2.2 m away from the interaction point, only has a 72 mm beam separation distance at the front end of the magnet. Because of the tight space, canted cosine theta coil type is the best selection, where the coil can be wound directly on the coil former in a fixed inclination angle. For QD0, the superconducting quadrupole coils for the two apertures are nearly in contact; high-order harmonics will be produced by magnetic field crosstalk and should be canceled out at the design stage. This article will present the design study for a pair of 400 mm long QD0 prototype, where we deliberately introduce some opposite harmonics to optimize the coil configuration so as to cancel out the unwanted harmonics.

Computation of beam based quantities with 3D final focus quadrupoles field in circular hadronic accelerators

The computation of analytic and numerical beam based quantities are derived for full 3D representation of the quadrupoles magnetic field, which can be computed by finite element code or measured. The impact of this more accurate description of the non homogeneity of the field is estimated on beam based observables and non linear correctors strengths, and compared with the less accurate models in the case of HL-LHC.