Quadrupole Lenses Research Articles

Beam Dynamics in the Heavy Ion Injector LU2 for the Synchrotron Research Complex (SRC)

The project of the complex for studying ionizing radiation exposure from outer space based on the synchrotron accelerator of protons and various types of ions up to 209Bi is being developed at the Russian Federal Nuclear Center - All-Russian Research Institute ofExperimental Physics (FSUE RFNC - VNIIEF). The accelerator includes two injection complexes (one of which is the source of protons and light ions, the second - heavy ions), the booster accelerator and the main synchrotron. The pulsed type heavy ions linac is being developed at the NRC “Kurchatov Institute” - KCTEF (Kurchatov Complex for Theoretical and Experimental Physics). The ions with mass-to-charge ratio 4÷8 with current of 10 mA will be accelerated up to 4 MeV/u. The linac is proposed, including the RFQ and two DTL sections operating at multiple frequencies. Each DTL section is modular and consists of individually phased H-type resonators (IH-DTLs). Quadrupole lenses located between the resonators for the beam focusing. This DTL structure ensures the accelerator compactness and allows section-by-section configuration and sequential commissioning. 6D beam matching between all sections of the linac is carried out. The results ofbeam dynamics simulation in linear accelerator are presented.

Deciphering the uranium isotopic signature of coastal water and sediments from Tokyo Bay using a multi-collector inductively coupled plasma mass spectrometer

We have measured 236U/238U and 235U/238U values in JMS-1 (geochemical reference material of Tokyo Bay sediments) and coastal seawater using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) equipped with both the retarding potential quadrupole lens and desolvating nebuliser system. For the accurate measurement of 236U/238U values (e.g., in the range of 10−9), mass spectrometric interferences on 236U isotope from both the peak tailing of 238U and polyatomic ion of 235UH were carefully corrected. With the sequential extraction experiments for JMS-1, whose U isotopic signatures were characteristic of isotopically-depleted U with industrial uses, authigenic U was extracted into a soluble fraction, and lithogenic U and anthropogenic U were gathered in an insoluble fraction. The anthropogenic U is likely to have been provided in insoluble forms and have deposited on the bay floor. Absence in differences of 236U/238U and 235U/238U values for seawater observed between inside and outside Tokyo Bay implies the negligibly small contribution of the anthropogenic U to U in the seawater. The data obtained here demonstrate the effective reduction of the interferences on 236U and the versatility of the isotopic signatures of U as an effective tracer for environmental circulation of U in nature.

Simulation and Measurement of Carbon Ion Beam Emittance in the Channel of Radiobiological Research at the Accelerator Complex U-70

The technique for determining the emittance of carbon ion beams by measuring their transverse dimensions at the end of the air gap of the channel is described. The inverse transformation of phase ellipses is considered, taking into account multiple Coulomb scattering of particles and the presence of dispersion in the carbon ion beam. The values of betatron emittance before the first quadrupole lens are given and compared with data obtained by direct calculation starting from the inner target. Inaccuracies in the calculated and measured emittance values are discussed. Simulations and measurements were performed at beam energies of 200, 300, and 400 MeV/nucleon in front of the target.

Research of Quadrupole Lenses for Ions Transport Channel

In Budker Institute of Nuclear Physics SB RAS the magnetic elements of transfer channel for charged particle beams from SIS18 to SIS100 (FAIR, Germany) [1] were developed. The article presents a description of the quadrupole magnet Q2 and serial magnetic measurements results. Magnetic measurements with application of rotating harmonic coil and moving carriage with linear array of Hall sensors were taken. Quadrupole lenses provide magnetic field integral gradient with high quality (<5·10-3) and satisfy the requirements. High order harmonics are present in the magnetic field due to manufacturing and assembly errors and can imperfect on beam dynamics. Main attention was considered to the third (sextupole) harmonic amplitude, determinate the chromatic properties of the lens. It allows select manufactured magnets to distortion value and minimize imperfection of beam dynamics by optimal theirs arrangement.

VEPP-4M linear optics correction using orbit response matrices

This paper presents procedures and techniques for correcting the linear optics of the VEPP-4M collider. The accelerator structure investigation is based on the measurement and analysis of orbit response matrices (ORM) and optical functions reconstructed from turn-by-turn (TbT) data. Having no technical description of quadrupole lenses and corrector magnets, we have calibrated their current dependencies of magnetic strengths and fields, respectively. Corresponding to the reference orbit, quadrupole shifts in each plane have been obtained by using the beam-based alignment (BBA) technique. The accelerator optics has been corrected and calibrated at the injection energy of 1.9 GeV. The software combining automated optical functions measurement and correction has been developed and successfully implemented at VEPP-4M.

Beam Dynamics Studies for a Proposed H – type DTL Using in Eye Therapy

Abstract: In this study, we explore the KONUS (Kombinierte Null Grad Struktur) beam dynamic studies using a 3D–PIC LORASR simulation code for a specialized medical drift tube linac designed for eye therapy. A total acceleration voltage of 70.89 MV is applied through 6 CH–DTL (3 coupled and 3 non-coupled) cavities within a total of 140 gaps, spanning a length of 20 m. This setup is designed to accelerate protons from an initial energy of 3 MeV to 70 MeV, tailored for application in eye therapy. Each cavity operates at a frequency of 325.244 MHz. To maintain transverse matching of the beam, 11 triplet quadrupole lenses are distributed along the linac structure, including one in the transport section. The beam dynamics analysis provides actual values for the lengths of drift tubes and gaps. To ensure linac stability, simulations are conducted to assess machine errors. The obtained lengths of drift tubes, gaps, and periods serve as the foundation for constructing the RF model for each cavity using the CST Studio Suite. The overall results are quite promising, indicating the viability of proceeding to the next phase, which includes RF simulations and mechanical modeling. Keywords: LORASR code, KONUS, Beam dynamics, DTL, CST, Eye therapy.

High demagnification probe-forming systems with spherical aberration correction for a nuclear microprobe

Probe-forming systems with high demagnification (up to 900) based on a separated orthomorphic quadruplet of magnetic quadrupole lenses are considered. Spherical aberrations are corrected using an octupole lens system. Three, two, and one lens correctors are used. The calculation of the octupoles parameters was carried out using the Matrizant method. The focusing properties of the systems are determined by optimizing the process of probe formation based on the value of the maximum reduced collimated acceptance in the range of beam spot sizes on the target from 10 to 100 nm. The possibility of implementing the considered systems in experimental setups for various applications is demonstrated by the results of the numerical analysis performed.

Hybrid Quadrupole Lens for the Focusing Channel of the DARIA Complex

Hybrid Quadrupole Lens for the Focusing Channel of the DARIA Complex

A quantum logic gate for free electrons

The topological charge m of vortex electrons spans an infinite-dimensional Hilbert space. Selecting a two-dimensional subspace spanned by m=±1, a beam electron in a transmission electron microscope (TEM) can be considered as a quantum bit (qubit) freely propagating in the column. A combination of electron optical quadrupole lenses can serve as a universal device to manipulate such qubits at the experimenter's discretion. We set up a TEM probe forming lens system as a quantum gate and demonstrate its action numerically and experimentally. High-end TEMs with aberration correctors are a promising platform for such experiments, opening the way to study quantum logic gates in the electron microscope.

Hybrid Quadrupole Lens for the Focusing Channel of the DARIA Complex

The results of synthesis and electromagnetic calculation of a hybrid quadrupole lens for a proton linear accelerator of a compact neutron source DARIA are presented. The lens includes a permanent magnet quadrupole with a fixed magnetic field gradient and an auxiliary electromagnetic quadrupole excited by a pulsed current. The permanent magnet quadrupole is made of radiation-resistant rare-earth magnet, and the electromagnetic quadrupole is designed to compensate for permanent magnet magnetization losses resulting from radiation degradation as neutron fluence accumulates during accelerator operation. A hybrid quadrupole lens can be applied for fast adjustment of the focusing channel when accelerating ion beams with different ion mass-to-charge ratios.

HIGH RESOLUTION PROBE-FORMING SYSTEM WITH SPHERICAL ABERRATION CORRECTION FOR NUCLEAR MICROPROBE

A probe-forming system based on a separate orthomorphic quadruplet of magnetic quadrupole lenses with a short working distance is considered, allowing the system demagnification to be significantly increased. Three magnetic octupole lenses are used to correct spherical aberrations. The parameters of the octupole corrector are calculated using the matricant method. The focusing properties of the system are determined by means of a probe formation optimization process based on the value of the maximum reduced collimated acceptance. The calculations performed showed the feasibility of such a probe forming system for microanalysis and proton beam writing technique.

Current status of the Tohoku microbeam system at Tohoku University and other facilities

We developed two microbeam lines, MB-I and MB-II, which both have quadrupole lenses and slits on heavy, rigid, anti-vibration tables. The MB-I beam diameter of 400 nm was achieved by reducing the parasitic magnetic field. MB-II is a simpler version of MB-I; both beamlines have various applications, and both are controlled by LabVIEW-based software and a programable logic controller (PLC). The beam scanners are downstream of the quadrupole lenses and controlled by a CompactRIO system. An automatic beam-focusing and focal guidance system reduces the time required for experimental configuration; this system is in routine use by researchers at Tohoku University. Microbeam experiments can easily be performed using this system. To further expand the applications, we developed MB-II-AQUA, which is based on MB-II but has advanced modularization and packaging. MB-II-AQUA is commercially available and retains the performance of MB-II, but is easier to use. A control system for the quadrupole lens and slit has been installed at the Takasaki Advanced Radiation Research Institute, which is a leading microbeam research facility in Japan.

The parameters of radio frequency quadrupole linear accelerator for DARIA project

The new proton linear accelerator (linac) with output energy 13 MeV and 100 mA current is under development at NRC “Kurchatov Institute” - ITEP for DARIA project. The linac consists of Radio-Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) with operating frequency 162.5 MHz. The RFQ is based on 4-vanes structure with shifted coupling windows. DTL has a modular structure and consists of separated individually phased cavities with focusing magnetic quadrupoles located between the cavities. The DTL is based on interdigital H-mode (IHDTL) 5-gaps cavities. The 6D beam matching between RFQ and DTL is provided by magnetic quadrupole lenses and RF-bunchers. The paper presents results of the radio-frequency (RF) design, thermal analyses and RF tuning of RFQ linac accelerating structure.

Reduce spherical aberration of doublet of combined quadrupole lenses (rectangular model)

The optimization calculations are made to find the optimum properties of doublet of combined quadrupole lens consist of electrostatic and magnetic lenses to produce reduce spherical aberration lens. The rectangular model is used and finds the properties of lens as the magnification and aberration coefficient. To find the optimum value of spherical aberration coefficient, the effect of both the excitation parameter of the lens, distance between of lenses and the effective wave length of the lens as active parameter to get the optimization.

Investigation of spin rotators in CEPC at the Z-pole

PurposeLongitudinal polarization is an important design aspect of the future 100 km-scale Circular Electron Position Collider (CEPC). Spin rotators are needed in the CEPC collider rings to make the beam polarization along the longitudinal direction at the interaction points (IPs). This paper focuses on the design of spin rotators for CEPC at the Z-pole (45.6 GeV).MethodsThe design of spin rotators in the CEPC at the Z-pole is based on solenoid magnets and horizontal bending magnets sections. The coupling of transverse motion introduced by solenoids is compensated with quadrupole lenses. Adjustments have been made to the layout to implement the spin rotators into the collider rings.ResultsLongitudinal polarized beam can be achieved at the IPs with the spin rotators. High degree of polarization is attainable, while the effect of spin rotators on orbital motion is acceptable. The detailed simulation results will be presented.ConclusionA solenoid-based spin rotator configuration is designed and integrated into the CEPC collider ring lattice. According to the simulation results, the polarization requirements can be satisfied.

An Alternating Phase Focusing injector for heavy ion acceleration

The new heavy ion superconducting continuous wave HElmholtz LInear ACcelerator (HELIAC) is under construction at GSI. A normal conducting injector, comprising an ECR ion source, an RFQ and a DTL, is recently in development. The new Interdigital H-mode DTL, presented in this paper, accelerates the heavy ion beam from 300 to 1400keV/u, applying an Alternating Phase Focusing (APF) beam dynamics scheme. This APF section, consisting of two separately controlled tanks, has to provide for stable routine operation with assistance of dedicated beam diagnostics devices in the Intertank section. The installed quadrupole lenses and beam steerers installed there ensure full transmission in a wide range of input beam parameters.

Beamline design with weak-focusing magnetic field for applications of laser-driven proton beams

<sec>With the development of high-power laser technology, laser plasma acceleration has developed rapidly due to its excellent acceleration structure. Nearly one-hundred-MeV proton beams and several GeV electron outputs are obtained. The laser-driven proton beams have excellent quality of μm-scale sizes and ps-scale pulse lengths. Owing to the existence of the accelerating laser field, direct application is difficult, so the proton beams need to be transmitted to the application terminal through the beamline. However, the wide energy spectrum and large divergence angle bring difficulties in transmitting the beam. The weak focusing in the constant gradient magnetic field is neglected in the transmission of laser-driven particle beams because of the relatively weak focusing force. But weak focusing has special advantages: simultaneous focusing in the horizontal direction and the vertical direction, energy analysis in the horizontal direction, focusing force in the horizontal and vertical direction distributed by the field index <i>n</i>, and smaller influence of chromatic aberration effect.</sec><sec>In this paper, we propose the beam transmission with weak-focusing magnet. The requirements for the focusing of proton beams with the same energy and different divergence angles in the <i>X</i> direction and <i>Y</i> direction in the weak-focusing magnetic field are explored by studying the linear beam dynamics of the beams. Then the conditions of precise energy analysis for particle beams with large divergence angle can be determined. For beams with 2% energy spread, the lengths of the drift space before and after the weak-focusing magnet and deflection radius are scanned to find out the minimum beam size and the shortest pulse length after transmission. It is found that a certain combination of drift space and deflection radius can minimize the beam size or the pulse length. Focusing and energy selection can be achieved while compressing the pulse length and effectively reducing the size of the beamline, which has significant advantages. When the deflection radius is 0.65 m, the proton beam with 20 MeV energy, 2% energy spread, and an initial divergence angle of ±50 mrad has the root-mean-square size of 108 μm in both the <i>X</i> direction and the <i>Y</i> direction, and a pulse length of 154 ps at the application terminal.</sec><sec>Comparing with common beam transmission elements such as quadrupole lenses and deflection magnets, the laser-accelerated ion beam benefits from the integration of focusing and energy analysis of weak-focusing magnetic fields (focusing and energy analysis exist at the same time and continuously change with deflection angle), as well as the horizontal and vertical focusing forces can be distributed by the magnetic field index <i>n</i> (the larger the <i>n</i>, the stronger the focusing force in the vertical direction is and the weaker the focusing force in the horizontal direction). When the proton beam is transmitted in a weak-focusing magnetic field, the advantages of the focusing element and the energy selection element are combined, so the influence of the chromatic aberration effect can be reduced, the pulse length can be compressed, and the beamline size can be effectively reduced.</sec>

X-ray streak camera tube with two photocathodes

<sec>The time-resolved X-ray spectroscopy measurement system based on X-ray streak camera technology is indispensable diagnostic equipment in the study of laser inertial fusion research and high-energy-density physics. However, limited by the effective photocathode length of the X-ray streak tube, the time-resolved spectral measurement system usually used has the shortcomings of narrow spectrum range and poor spectral resolution.</sec><sec>In order to overcome the shortcomings, a novel dual-channel streak tube is developed, which consists of a photocathode, a prefocusing electrode group in temporal direction, an electric quadrupole lens electrode group, a main focusing electrode group in temporal direction, a deflector plate, and a phosphor screen. The photocathode has two slits. When X-rays are incident, two electron beams can be emitted simultaneously. The electric quadrupole lens electrode group is composed of 8 arc electrodes. Two electric quadrupole lenses are formed by the 8 arc electrodes in the spatial direction. Two electron beams emitted from the cathode of the streak tube are first accelerated and prefocused by the prefocusing electrode group in the time direction, and then compressed by the main focusing electrode group in the time direction. In the spatial direction, two electron beams are focused by the two electric quadrupole lenses independently. This novel streak tube structure can focus two electron beams at the same time, thereby increasing the effective photocathode length and maintaining the compact structure of streak tube without increasing the aberration.</sec><sec>The cathode voltage of the designed streak tube is –12 kV, the distance from cathode to grid is 5 mm, and the cathode-grid field strength is 2.4 kV/mm. The cathode is divided into two sections, the spacing between sections is about 13 mm, the length of each section is more than 20 mm, the magnification of the image converter tube is about 1.56 times, the distance between the cathode and the phosphor screen is 300 mm, and the longest size along the cathode direction is 90 mm. The test results of the performance of the streak tube show that the actual effective cathode length of the developed tube reaches 44 mm, the spatial resolution is better than 15 lp/mm, and the deflection sensitivity is better than 40 mm/kV. The effective cathode and spatial resolution of the tube can be increased to 50 mm and 25 lp/mm by further optimizing the structure of the tube and removing the image intensifier with a high sensitivity image recording system, respectively.</sec>

Wave-optical study of the Einstein cross formed by a quadrupole gravitational lens

We study imaging of point sources with a quadrupole gravitational lens while focusing on the formation and evolution of the Einstein cross formed on the image sensor of an imaging telescope. We use a new type of a diffraction integral that we developed to study generic, opaque, weakly aspherical gravitational lenses. To evaluate this integral, we use the method of stationary phase that yields a quartic equation with respect to a Cartesian projection of the observer's position vector with respect to the vector of the impact parameter. The resulting quartic equation can be solved analytically using the method first published by Cardano in 1545. We find that the resulting solution provides a good approximation of the electromagnetic (EM) field almost everywhere in the image plane, yielding the well-known astroid caustic of the quadrupole lens. The sole exception is the immediate vicinity of the caustic boundary, where a numerical treatment of the diffraction integral yields better results. We also convolve the quartic solution for the EM field on the image plane with the point-spread function of a thin lens imaging telescope. By doing so, we are able to explore the direct relationship between the algebraic properties of the quartic solution for the EM field, the geometry of the astroid caustic, and the geometry and shape of the resulting Einstein-cross that appear on the image plane of the thin lens telescope. The new quartic solution leads to significant improvements in numerical modeling as evaluation of this solution is computationally far less expensive than a direct numerical treatment of the new diffraction integral. In the case of the solar gravitational lens (SGL), the new results drastically improve the speed of numerical simulations related to sensitivity analysis performed in the context of high-resolution imaging of exoplanets.

IMPROVEMENT OF HELIUM IONS BEAM FORMATION AND TRANSPORT SYSTEM

Works on improvement of a beam formation and transport system from an accelerating section output to the target complex on NSC KIPT helium ions linear accelerator with output energy of 4 MeV, used for carrying out of radiating researches are continued. Results of researches spent with electromagnetic quadrupole lenses, forming a triplet are presented. Experiments with injected (120 keV) and accelerated (4 MeV) helium ions beams by means of advanced beam formation and transport system to a target are continued. The proposal on decrease in thermal loading of a triplet is formulated.