Super Collider Research Articles

Extremum Seeking-Based Control System for Particle Accelerator Beam Loss Minimization

Particle accelerators throughout the world vary widely in terms of age and availability of advanced noninvasive diagnostics that provide varying levels of detail about the accelerated beams. Beam loss measurements and current monitors are ubiquitous in the accelerator community, they are noninvasive, and they are some of the most important metrics in terms of preventing damage or irradiation of beam pipes and equipment for high-energy machines. However, beam loss and current measurements are difficult to use for feedback tuning because of a lack of a known analytic relationship between scalar loss measurements throughout an accelerator and the hundreds of thousands of parameters that influence the beam and time variation of the beam source itself. In this work, we present a model-independent extremum seeking (ES) controller, which has been implemented for automated tuning and optimization of the Los Alamos Neutron Science Center (LANSCE) linear ion accelerator based only on scalar quantities, such as beam loss or flux measurements. We demonstrate the approach on various accelerator subsystems, including groups of radio frequency (RF) accelerating cavities, quadrupole magnets, bending magnets, and steering magnets. This tool is now available as a use graphical user interface (GUI) in the LANSCE control room, allowing beam physicists to choose arbitrary groups of parameters and beam loss or current monitors for adaptive tuning.

Research on automatic positioning technology for magnetic field measurement of multipole magnet harmonic coil in heavy ion accelerator

In the magnetic field measurement of accelerator magnets, efficient and accurate positioning of the magnetic field measurement system and the magnet is a critical process. By analyzing the mechanical structure and working principle of harmonic coil magnetic field measurement system, an automatic positioning technology is proposed in this research for the high-precision and fast positioning of multipole magnet and harmonic coil magnetic field measurement system. Through the special design and comprehensive application of multi-camera photogrammetry system, control system and six-degree-of-freedom (6DoF) attitude automatic adjustment system, fast non-contact measurement and automatic attitude adjustment of harmonic coil magnetic field measurement system and multipole magnet can be realized. The proposed automatic positioning system and operation scheme can not only save labor costs, but also improve the reliability of harmonic coils and the positioning efficiency of magnetic field measurement system. The proposed research can also monitor the position changes of the harmonic coil and the multipole magnet in the magnetic field measurement process in real time through the multi-camera photogrammetry system, and further control the accuracy of the magnetic field measurement of the harmonic coil.

Accelerating Earth-bound dark matter

A fraction of the dark matter may consist of a particle species that interacts much more strongly with the Standard Model than a typical weakly interacting massive particle (WIMP) of similar mass. Such a strongly interacting dark matter component could have avoided detection in searches for WIMP-like dark matter through its interactions with the material in the atmosphere and the Earth that slow it down significantly before reaching detectors underground. These same interactions can also enhance the density of a strongly interacting dark matter species near the Earth's surface to well above the local galactic dark matter density. In this work, we propose two new methods of detecting strongly interacting dark matter based on accelerating the enhanced population expected in the Earth through scattering. The first approach is to use underground nuclear accelerator beams to upscatter the ambient dark matter population into a WIMP-style detector located downstream. In the second technique, dark matter is upscattered with an intense thermal source and detected with a low-threshold dark matter detector. We also discuss potential candidates for strongly interacting dark matter, and we show that the scenario can be naturally realized with a hidden fermion coupled to a sub-GeV dark photon.

Accelerator mass spectrometry measurements of 93Zr for astrophysical and nuclear technology applications

Zirconium-93 is a long-lived radionuclide with a half-life of (1.61 ± 0.05) × 106 yr. Production cross sections for 93Zr by neutron capture on stable 92Zr in the keV and thermal energy ranges are important input parameters for astrophysical network calculations and nuclear industry, respectively. Despite their importance, existing experimental data suffer from large uncertainties. Here, the combination of neutron activation and accelerator mass spectrometry (AMS) is presented as an alternative method to online time-of-flight measurements for the determination of these cross sections. The main challenges for AMS of 93Zr are the interference from the stable isobar 93Nb and the production of suitable reference material. At the Heavy Ion Accelerator Facility (HIAF) the first challenge is tackled with the available high particle energies and by investigating different Zr compounds and extracted molecular beams. Using ZrF5− beams extracted from ZrF4 sample material, it is shown that the Nb background can be reduced by up to two orders of magnitude relative to the extraction of ZrO− beams from ZrO2. Using the 13+ charge state and particle energies of ∼190 MeV, 93Zr/Zr background levels in the 10−12 range are regularly achieved at HIAF. The ZrF5− output from ZrF4 samples may be highly variable but can be stabilised using an intimate mixture of ZrF4 and PbF2 at a ratio of 1:10 that has been dried down from a concentrated hydrofluoric acid solution. An option to produce a well-characterised 93Zr reference material by utilising the well-known 235U-fission yield of 93Zr is discussed. Once this remaining challenge is resolved, accurate measurements of the astrophysically and technologically relevant neutron-capture cross sections of 92Zr using AMS will be possible at HIAF.

Responses of hematopoietic cells after ionizing-irradiation in anemic adult medaka (Oryzias latipes)

Purpose Hematopoietic tissues of vertebrates are highly radiation sensitive and the effects of ionizing radiation on the hematopoiesis have been studied in mammals and teleosts for decades. In this study, radiation responses in the kidney, the main hematopoietic organ in teleosts, were investigated in Japanese medaka (Oryzias latipes), which has been a model animal and a large body of knowledge has been accumulated in radiation biology. Methods Kidney, the main hematopoietic tissue of adult medaka fish, was locally irradiated using proton and carbon ion beams irradiation system of Takasaki Ion Accelerator for Advanced Radiation Application (TIARA), QST, and the effects on peripheral blood cells and histology of the kidney were investigated. Results When only kidneys were locally irradiated with proton or carbon ion beam (15 Gy), the hematopoietic cells in the irradiated kidney and cell density in the peripheral blood decreased 7 days after the irradiation in the same manner as after the whole-body irradiation with γ-rays (15 Gy). These results demonstrate that direct irradiation of the hematopoietic cells in the kidney induced cell death and/or cell cycle arrest and stopped the supply of erythroid cells. Then, the cell density in the peripheral blood recovered to the control level within 4 days and 7 days after the γ-ray and proton beam irradiation (15 Gy), respectively, while the cell density in the peripheral blood did not recover after the carbon ion beam irradiation (15 Gy). The hematopoietic cells in the irradiated kidneys temporarily decreased and recovered to the control level within 21 days after the γ-ray or proton beam irradiation (15 Gy), while it did not recover after the carbon ion beam irradiation (15 Gy). In contrast, the recovery of the cell density in the peripheral blood delayed when anemic medaka were irradiated 1 day after the administration of phenylhydrazine. With and without γ-ray irradiation, a large number of hematopoietic cells was still proliferating in the kidney 7 days after the anemia induction. Conclusions The results obtained strongly suggest that the hematopoietic stem cells in medaka kidney prioritize to proliferate and increase peripheral blood cells to eliminate anemia, even when they are damaged by high-dose irradiation.

Design and field measurement of dipole magnets for a 300-MeV proton and heavy ion synchrotron in SESRI

Space Environment Simulation and Research Infrastructure (SESRI) is a new national research infrastructure under construction at Harbin Institute of Technology (HIT) in China. Its 300-MeV proton and heavy ion accelerator is a major radiation source, and a compact synchrotron has been designed with a circumference of less than 44 m. The synchrotron dipoles are essential components of the accelerator, and they have been designed and tested carefully to meet the stringent physical requirements. The measured transverse field homogeneity is less than 2 × 10-4 from 0.2 T to 1.4 T and roughly agrees with the simulated results. With a modified linear programming algorithm, the integral magnetic field uniformity within 0.2–1.1 T is optimised from 6 × 10-4 to 1.5 × 10-4, and the corresponding multi-pole field-component errors are greatly reduced. By shortening the pole ends, the reproducibility of integral field among six magnets at 0.2 T is less than 3 × 10-4. In addition, the transient effect of the magnetic field is also evaluated and tested. Through analysis of the transient effect and structural strength, low-carbon steel and stainless steel are selected for the side plates and end plates, respectively. According to the transient measurement results, the feedforward compensation can be implemented to produce a more accurate current waveform. On 1 January 2022, the beam was successfully accumulated with the preset current waveform, and the beam intensity met the design requirements.

Large shift in surface plasmon resonance wavelength with growth of embedded Au nanoparticles in fullerene C60 by Collision Cascades

We report a 220 keV Ag ion beam irradiation-induced modifications of thin films of fullerene C60 containing gold (Au) nanoparticles. Nanocomposite thin films of Au-C60 were synthesized using a thermal co-deposition technique on a glass substrate. The as-deposited (pristine) thin films were irradiated by 220 keV Ag ion beam at different fluences ranging from 1 × 1013 ions/cm2 to 3 × 1016 ions/cm2 utilizing a low energy ion accelerator. The optical properties of pristine and irradiated thin films of Au-C60 were investigated using UV–visible spectroscopy. A redshift in the Surface Plasmon Resonance (SPR) wavelength from ~ 598–775 nm was obtained with increasing fluence up to 1 × 1014 ions/cm2, which indicated the growth of Au nanoparticles in the fullerene matrix due to ion irradiation. It was further confirmed by High-Resolution Transmission Electron Microscopy (HRTEM). With further increase in fluence, a blue shift from ~ 775–570 nm was obtained at a fluence of 1 × 1016 ions/cm2. The transformation of fullerene C60 into amorphous carbon (a:C) with increasing fluence of Ag ion beam was the main cause of this blue shift which was further confirmed by Raman spectroscopy. An increase in surface grain size with ion fluence was observed by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM). The X-ray Photoelectron Spectroscopy (XPS) measurements were used for the chemical state analysis of the nanocomposite thin films before and after irradiation. The current-voltage measurements confirm the increase in the conductivity of the nanocomposite films with the fluence due to its transformation in carbon at higher fluences. The control on the size of Au nanoparticles and tuning of SPR wavelength by low energy ion irradiation may enhance the applicability of Au-C60 nanocomposite in organic solar cell.

Development of a beam energy adjustment system after a Radio-Frequency-Quadrupole

The Low Energy heavy-ion Accelerator Facility (LEAF) is a low-energy, high-intensity, heavy ion accelerator for multidisciplinary research developed at the Institute of Modern Physics (IMP). Beam commissioning of the facility began in 2018, but until recently, only a fixed beam energy of 0.5 MeV/u was available because the main accelerator structure is a Radio-Frequency Quadrupole (RFQ), which hinders LEAF to meet the requirements of the experimental terminals, for example, 12C+12C fusion reaction investigation at astrophysical energies requires beam energies adjustable from 0.3 MeV/u to 0.7 MeV/u. To expand the beam energy range, a “constant-beta” structure Drift Tube Linac (DTL) was developed providing an adjustable beam energy from 0.3 to 0.7 MeV/u. To control the beam quality, specifically the energy spread, two re-bunchers are employed, one upstream and one downstream of the DTL. Here we present the development of the key device: an Interdigital H-mode DTL (IH-DTL). First, we discuss the beam dynamics design for the beam energy adjustment system, then we present details of the test bench, and finally, we report measurements performed with the finished hardware. The measurements of energy adjustment and energy spread agree well with the simulations, demonstrating the feasibility of this design.

Design study of a single bunch selection method for neutron TOF experiment at RAON heavy ion accelerator

To enable neutron time-of-flight (TOF) experiments at the RAON heavy-ion accelerator facility, we propose a single bunch beam selection method by combining a fast chopper and double gap buncher in the low-energy beam transport (LEBT) section. The fast chopper operates with switching times of tens of ns to convert a CW beam into a pulsed beam.Then, the double gap buncher performs bunching to shorten the beam pulse duration to less than one radio frequency quadrupole (RFQ) cycle.Ideally, a single isolated bunch can be achieved after the RFQ.In this study, we discuss the system design of the proposed single bunch selection scheme and present detailed beam dynamics simulations.

Production of intense pulsed beams of highly charged ions from a superconducting electron cyclotron resonance ion source

An experimental study of the afterglow mode was performed with a third generation electron cyclotron resonance ion source, SECRAL-II (Superconducting ECR ion source with Advanced design in Lanzhou No. II), under double frequency heating. The experimental results show that intense pulsed beams of highly charged ions (e.g., $266\text{ }\text{ }\mathrm{e}\ensuremath{\mu}\mathrm{A}$ of ${^{129}\mathrm{Xe}}^{34+}$ and $169\text{ }\text{ }\mathrm{e}\ensuremath{\mu}\mathrm{A}$ of ${^{129}\mathrm{Xe}}^{38+}$) could be produced at high frequency ($24+18\text{ }\text{ }\mathrm{GHz}$) and high power ($\ensuremath{\sim}8\text{ }\text{ }\mathrm{kW}$), even compared with the beam intensity records of SECRAL-II obtained in continuous wave (cw) mode at higher microwave frequency ($28+18\text{ }\text{ }\mathrm{GHz}$) and higher power ($\ensuremath{\sim}10\text{ }\text{ }\mathrm{kW}$), the gain factor is also up to $\ensuremath{\sim}3$. Meanwhile, it is found that the afterglow decay time in our study is much longer than that obtained with the second generation ECR ion sources typically operating at 10--18 GHz, and the corresponding peak duration is greater than 2 ms. This study provides a viable solution for heavy ion synchrotron accelerator complex such as High Intensity Heavy Ion Accelerator Facility project that requires intense pulsed beams of highly charged ions with long peak duration.

Rapid estimation of the isotopic composition and total mass fraction of boron in enriched B4C samples for Indian fast reactor technology using external (in air) particle induced Gamma-ray emission technique

Enriched boron carbide of nuclear grade is being used for the fabrication of control and poison rod materials in the Indian nuclear fast reactor program. Hence, a stringent quality control protocol becomes necessary to ensure the quality of enriched B4C powder as well as its finished products. In the present work, the external Proton Induced Gamma-ray Emission (PIGE), a non destructive technique, was applied for the rapid estimation of the isotopic composition of boron (10B/11B) and the total boron mass fraction in various enriched B4C samples with less turnaround time of analysis at FOlded Tandem Ion Accelerator (FOTIA), BARC. The isotopic composition and total boron concentrations obtained by PIGE were compared with the values obtained from Thermal Ionization Mass Spectrometry (TIMS) and classical Titrimetry methods respectively and found to be in good agreement. The statistical evaluation like students’ t-test was also performed to ascertain the reliability of the results obtained by PIGE, TIMS and Titrimetry.

Once a physicist …

I appreciated Charles Day’s introduction to Physics Today’s most recent careers issue (October 2021, page 8). I am always delighted to see attention drawn to the wide range of satisfying careers that can be entered with a physics degree.The “Spotlight on Hidden Physicists” series in Sigma Pi Sigma’s Radiations magazine is very special to me as a matter of inclusion and personal perspective. I vividly recall reading letters in Physics Today around the time of the cancellation of the Superconducting Super Collider in 1993. Much was made of how the cancellation was (or wasn’t) the demise of US physics and how difficult it was for new PhD physicists to find proper jobs at the time. Industrial and other “hidden” physics jobs were not given much respect, and I don’t recall many letters that discussed the struggles of those with bachelor’s degrees in physics during that time.A few years later, I had the privilege of being elected to the National Council for the Society of Physics Students and Sigma Pi Sigma. Under the leadership of Gary White, the director from 2001 to 2012, I participated in developing the broad outline of the Hidden Physicists program. One of our goals was to combat the prevalent misconception that the only thing a physics degree was useful for was a career in academic or government research.That attitude is a great insult to the majority of physics degree holders, because only a relative few wind up in the business of publishing physics articles. Every year the country produces many more students with bachelor’s degrees in physics than with PhDs. For example, data from the 2019–20 academic year show that 9296 students received bachelor’s degrees in physics, while 1830 earned PhDs in the subject.11. S. Nicholson, P. J. Mulvey, Roster of Physics Departments with Enrollment and Degree Data, 2020: Results from the 2020 Survey of Enrollments and Degrees, AIP Statistical Research Center (September 2021). For the classes of 2019 and 2020, only about a third of physics bachelors pursued graduate degrees in physics or astronomy, and not all PhD graduates in those years ended up in “publish or perish” jobs.22. AIP Statistical Research Center, Initial Employment—Physics Bachelors and PhDs: Classes of 2019 and 2020 (March 2022).I espouse the view that completing any degree in physics alters a person’s worldview and influences them for the rest of their life, whether they wind up with a PhD in physics or a PhD in medieval literature (a path one of my students followed).Yes, it is a viewpoint akin to that of Aslan’s in The Lion, the Witch and the Wardrobe by C. S. Lewis: “Once a king or queen in Narnia, always a king or queen.” I concede that not everyone will be so inclusive. I strongly contend that someone who regularly uses their physics background is still a physicist, even if they are not publishing physics papers. That includes someone like the editor-in-chief of Physics Today, who must rely on a strong background in physics to be effective. So Charles, I recognize you as a physicist, and in your role at Physics Today, you were perhaps the most visible “hidden” physicist that I could imagine!ReferencesSection:ChooseTop of pageReferences <<1. S. Nicholson, P. J. Mulvey, Roster of Physics Departments with Enrollment and Degree Data, 2020: Results from the 2020 Survey of Enrollments and Degrees, AIP Statistical Research Center (September 2021). Google Scholar2. AIP Statistical Research Center, Initial Employment—Physics Bachelors and PhDs: Classes of 2019 and 2020 (March 2022). Google Scholar© 2022 American Institute of Physics.

A new digital beam position and phase measurement implementation based on a field programmable gate array for the high intensity heavy-ion accelerator iLinac.

A new digital beam position and phase measurement (BPM) system was designed for the ion-Linac accelerator at the high intensity heavy ion accelerator facility. The fundamental and second harmonic signals are retrieved from the BPM electrodes to simultaneously calculate their respective beam positions and phases. All data acquisition and digital signal processing algorithm routines are performed in a field programmable gate array (FPGA). The position and phase information are obtained by using the in-phase and quadrature demodulation method. A practical and straightforward method is used to generate the second harmonic reference signal for processing the second harmonic beam signal. The reconfigurable filters are integrated into the FPGA to allow the measurement of short beam pulse length. The laboratory test results show that the achieved phase resolution is better than 0.2° and 0.03° when the input signal is -60 and -45 dBm, respectively. A position resolution better than 30 μm was achieved for an input power level of approximately -60 dBm, and it can reach 7 μm with the input power higher than -45 dBm. The entire execution time of the algorithm is accomplished within 3.4 µs, which provides a sufficient reaction time for the fast beam interlock signal to the machine protection system. The performance of this newly designed prototype BPM electronics was evaluated with the online proton beam.

Experimental Demonstration of the Thin-Film Liquid-Metal Jet as a Charge Stripper.

For high-power heavy ion accelerators, the development of a suitable charge stripper, which can handle intense beams, is essential. This Letter describes the first experimental demonstration of a heavy ion liquid lithium charge stripper. A 10-20 μm thick liquid lithium jet flowing at >50 m/s was formed and confirmed stable when bombarded by various heavy ion beams, while increasing the charge state of the incoming beams to the desired charge state range. This demonstration proved the existing power limitation with the conventional strippers can be overcome by the liquid-metal stripper, opening completely new possibilities in high-power accelerator development.

Improvement of Magnet and Cavities cooling at Heavy Ion or Rare Isotopes Accelerators due to Application of sub-cooled Superfluid Helium

Several modern Heavy Ion or Rare Iosotopes Accelerator uses superconducting (sc) cavities for an acceleration of the beam particles. Operation of sc magnets with higher magnetic fields and improved field gradients also leads to a better beam focusing (also called “beam optics”) and improves the overall accelerator compactness. In many accelerators, like XFEL, SNS, LCLS-II, HIE-ISOLDE, ATLAS, ISAC-II/ARIEL, SPIRAL-2, FLASH, Jlab-FEL/ERL, the operation is limited either by cooling capability of sc cavities or refrigeration capacities. In most of the cases, increasing of refrigerator capacities is a challenging task due to available free space or investments, and, therefore, improvement of cavity cooling due to increasing of a quality factor (Q 0) or heat transfer at cavity surfaces is considered. Application of a sub-cooled superfluid (sf) helium gives several advantages, like higher heat flux densities, longer time for onset of a film boiling regime and shorter recovery time, reduced Kapitza resistances, etc. In the present paper, application of sub-cooled superfluid helium for cooling of cavities with half and quarter-wave resonators, which are typically applied at Heavy Ion and Rare Isotopes Accelerators or sometimes at electron and proton ones, is considered. In order to limit the present discussion, its application to FRIB-style cryomodules is discussed in details.

GUARDARE IL MONDO CON I NEUTRINI: IL SOLE, LA TERRA E L’UNIVERSO

Neutrinos are the most elusive and ubiquitous known building blocks in the Universe. Predicted by Wolfgang Pauli in 1930 and then theoretically elaborated by Enrico Fermi and Ettore Majorana in the following years, they were discovered experimentally in 1956 and since then they have never ceased to surprise us with their, sometimes disconcerting, properties. There are three different types that can transform into each other, devoid of electric charge, very light but with a very small mass, at least a million times lower than that of the electron. Although we know that they have a mass, we still do not know how much they weigh. In nature they are abundantly emitted by the Sun and stars, from the nucleus of the most active galaxies and from our planet they were produced in such abundance in the first moments of the Big Bang to the point of permeating the entire Universe with neutrinos. They are also produced in large numbers by nuclear reactors and particle accelerators, which allow us accurate and controlled studies. The neutrinos emitted by natural sources are unique messengers about the sources themselves and about the physical mechanisms that generate them. This note summarizes the main steps in the history of neutrinos, their most conspicuous properties and above all how much it has been possible to learn about the stars, the Earth, and the Sun thanks to them. Particular attention will be given to the recent results at the Gran Sasso National Laboratories obtained from the Borexino experiment which, by means of neutrinos, completed for the first time in 2020 the study of all nuclear fusion reactions that take place in the Sun, including that, minority but very important, catalyzed by the presence of Carbon, Nitrogen and Oxygen in the Sun’s core.

Ion beam tools for nondestructive in-situ and in-operando composition analysis and modification of materials at the Tandem Laboratory in Uppsala

Ion accelerators have demonstrated tremendous versatility in their research applications throughout several decades. Starting predominantly as nuclear physics tools, they subsequently provided novel insights into fundamental atomic physics. Nowadays small and medium size accelerators are routinely employed in several branches of materials science. As research questions increasingly drive the need for analyses and material modification experiments performed in-situ and/or in-operando, facilities must adapt to service such a need. In this work, we highlight capabilities for in-situ and in-operando composition depth profiling and materials modification, developed with instrumentation at the Tandem Laboratory at Uppsala University. An overview of available ion sources and accelerators is given. We then exemplify the specific capabilities of the available end stations for materials synthesis, sample modification and device operation either during simultaneous ion beam based characterization or with such characterization performed in-situ before and after the application of various modification steps. Describing specific recent examples and potential future applications, we illustrate the impact of the present national research infrastructure.

Lifetime analysis of Te128,130 via the Doppler-shift attenuation method

Background: The $Z=52$ nuclei $^{128}\mathrm{Te}$ and $^{130}\mathrm{Te}$ are interesting candidates to study nuclear-structure properties close to the $Z=50$ shell. The knowledge of lifetimes of low-lying states in those nuclei is still scarce.Purpose: The goal of the present work is to extend the experimental database of nuclear level lifetimes of low-spin states in $^{128}\mathrm{Te}$ and $^{130}\mathrm{Te}$.Methods: Nuclear level lifetimes were determined by means of the Doppler-shift attenuation method (DSAM) using $p\ensuremath{-}\ensuremath{\gamma}$ coincidences measured at the SONIC@HORUS setup located at the FN-Tandem ion accelerator of the University of Cologne.Results: For $^{128}\mathrm{Te}$, lifetimes of eleven excited states could be determined, one of these for the first time. For the case of $^{130}\mathrm{Te}$, 18 nuclear level lifetimes were obtained, 15 for the first time. In both experiments, upper limits for lifetimes of several additional levels were determined. Moreover, the nuclear level scheme of $^{130}\mathrm{Te}$ could be extended. One additional level and 13 new transitions for levels above 2.7 MeV have been added. A standard shell-model calculation was performed and compared with the experimental results, showing an overall agreement.Conclusions: DSAM using $p\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences is a powerful tool to determine lifetimes in the subpicosecond range free of feeding contributions. Although both experiments yielded low statistics, numerous lifetimes could be obtained. The use of $p\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences furthermore enables the extension of level schemes.

A novel positioning method for Hall magnetic field measurement of heavy ion accelerator

In the magnetic field measurement of accelerator magnets, the precise positioning of the magnetic field measurement system and the magnet is a basic and very important part. By analyzing the mechanical structure and working principle of Hall magnetic field measurement system, a novel positioning method is proposed in this research for the high-precision and fast positioning of magnet and Hall magnetic field measurement system. By measuring the geometric elements of the magnetic field measurement system and the calibration benchmark of the magnet, the geometric relationship between the magnetic field measurement system and the magnet is established, so as to quickly locate the magnet to the position and attitude required by the magnetic field measurement. The mechanical structure of the Hall probe of the magnetic field measurement system is optimized. Two special ceramic reflectors are installed on the vertical and horizontal axes corresponding to the center of the Hall sensor, and the two ceramic reflectors installed on the Hall probe is monitored with a laser tracker. In this way the Hall sensor can be intuitively positioned at the geometric center of the magnet with an accuracy better than 0.05 mm. In the measurement process, the magnetic field measurement trajectory of Hall sensor in the magnet can also be detected by monitoring the coordinates of ceramic reflector in real time. The practical application in Space Environment Simulation and Research Infrastructure (SESRI) magnet magnetic field measurement show that, compared with the traditional positioning method, the proposed positioning method not only improves the repeatability of Hall magnetic field measurement integral field by nearly 10 times, but also improves the positioning efficiency of magnetic field measurement. These results have verified the practicability and effectiveness of the proposed positioning method.

Optimization design and test of the Booster Ring dipole magnet in HIAF

The High-Intensity Heavy Ion Accelerator Facility (HIAF), proposed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP), is being designed to provide primary and radioactive intense beams for nuclear and related research. As an important part of HIAF, the Booster Ring (BRing) is a fast ramping synchrotron and is used to obtain high intensity (238U35+, 1 × 1011 ppp) and high energy (0.835 GeV/u) heavy-ion beam. Moreover, the beam rigidity of the Booster Ring varies widely from 1 Tm to 34 Tm. These require the dipole of Booster Ring to have a large-good field region, a high magnetic field homogeneity, and a wide range of magnetic field variation from 0.047 T to 1.58 T. Aiming at the properties of the dipole magnet, we adopt some new methods to improve magnetic field precision and optimize efficiency. Double symmetrical air holes in the magnet pole are used to guarantee the magnetic field homogeneity under a wide magnetic field range. At the same time, the linear programming algorithm is adopted to optimize the integral magnetic field uniformity of the iron-dominated dipole magnet, which improves the integral magnetic field precision and optimization efficiency. So far, the prototype dipole magnet has been fabricated and tested. Through magnetic field optimization, measurement, and secondary trimming, the measurement results satisfy the physical requirements.