Beam Size Measurements Research Articles

6 MV X-band linear accelerator for stereotactic body radiation therapy

This paper presents the development process of a high-dose X-band linear accelerator (LINAC) for radiotherapy machines, specifically focusing on stereotactic body radiation therapy (SBRT). The development process includes a multi-physics design, approach for the radio frequency cavity in the LINAC, with an emphasis on minimizing beam size and maximizing shunt impedance of the LINAC. Commissioning tests were conducted to evaluate the performance of the LINAC, which involved measurements of beam energy, beam size, beam current, and X-ray dose rate.

40‐1: Development of the Auto Monitoring Method of Laser Beam Shape and Size by Employing the AI and Computer Vision Algorithm

The beam shape of the laser cut process to change the display shape is very important in the laser cutting quality, and the laser beam shape was measured by using the beam profiler as a measuring instrument. Since the beam profiler cannot be used due to damage caused by the high laser processing power used in mass production, the beam shape be managed that the sample was created by laser beam cross shot drawing on the material and it was manually measured by using a microscope. However, this method had problems with a long management period (measured once a month), a machine down for the measurement, the measurement deviation between engineers, and inability to manage history, so it was necessary to develop AI‐based shape automatic management technology. To solve this problem, an AI agent program with the AI technology to determine OK, NG of laser beam and the beam size measurement technology based on the image processing was developed and applied to the production line. Through this program, automatic management and history management of beam shape and size that was not possible with previous method have become possible. It was confirmed that the AI and image processing technologies developed through this study can be important technologies that can have a ripple effect on the development of other technologies.

Commissioning and first operation of East Japan Heavy Ion Center at Yamagata University

A world smallest carbon ion radiotherapy facility, East Japan Heavy Ion Center, Yamagata University, started treatment operations in February 2021. The treatment system consists of an ECR ion source, an RFQ and IH-type drift tube linac, a 430 MeV/u synchrotron and a spot-scanning irradiation system. It has two treatment rooms, one is a fixed horizontal beam port and the other is a rotating gantry beam port with superconducting magnets. The ECR ion source is the Kei2-type permanent magnet 10 GHz ECR ion source with a maximum field of 0.8 T. All the improvements of the previous facilities are applied to the ion source, such as helium gas-assisted operation and changes in the shape of an anode electrode and an extraction electrode to reduce the discharge. Owing to these improvements, the ion source has been operated stably during the commissioning and clinical operation. The irradiation system of Yamagata University eliminated the plastic block range shifter to realize a compact gantry, and has 600 energy levels to control the beam range in step of 0.5 mm. In order to optimize the beam transport parameters quickly, automation tools for orbit correction were developed. Machine commissioning and clinical commissioning were carried out in parallel to allow treatment to begin earlier. First, the horizontal fixed beam port was commissioned by verifying the dose distribution of the treatment planning system. Then, the gantry beam port was commissioned by full beam distribution measurement for representing beam angle of 90 degree, and other angles were sequentially released after the compatibility measurement of beam position, beam size, and two-dimensional uniformity. In September 2022, we were able to accept all treatment sites. By August 2023, 1151 cancer patients had been treated. Further improvements to increase available gantry angle and to increase beam efficiency are ongoing.

Development of a novel fibre optic beam profile and dose monitor for very high energy electron radiotherapy at ultrahigh dose rates

Objective. Very high energy electrons (VHEE) in the range of 50–250 MeV are of interest for treating deep-seated tumours with FLASH radiotherapy (RT). This approach offers favourable dose distributions and the ability to deliver ultra-high dose rates (UHDR) efficiently. To make VHEE-based FLASH treatment clinically viable, a novel beam monitoring technology is explored as an alternative to transmission ionisation monitor chambers, which have non-linear responses at UHDR. This study introduces the fibre optic flash monitor (FOFM), which consists of an array of silica optical fibre-based Cherenkov sensors with a photodetector for signal readout. Approach. Experiments were conducted at the CLEAR facility at CERN using 200 MeV and 160 MeV electrons to assess the FOFM’s response linearity to UHDR (characterised with radiochromic films) required for FLASH radiotherapy. Beam profile measurements made on the FOFM were compared to those using radiochromic film and scintillating yttrium aluminium garnet (YAG) screens. Main results. A range of photodetectors were evaluated, with a complementary-metal-oxide-semiconductor (CMOS) camera being the most suitable choice for this monitor. The FOFM demonstrated excellent response linearity from 0.9 Gy/pulse to 57.4 Gy/pulse (R 2 = 0.999). Furthermore, it did not exhibit any significant dependence on the energy between 160 MeV and 200 MeV nor the instantaneous dose rate. Gaussian fits applied to vertical beam profile measurements indicated that the FOFM could accurately provide pulse-by-pulse beam size measurements, agreeing within the error range of radiochromic film and YAG screen measurements, respectively. Significance. The FOFM proves to be a promising solution for real-time beam profile and dose monitoring for UHDR VHEE beams, with a linear response in the UHDR regime. Additionally it can perform pulse-by-pulse beam size measurements, a feature currently lacking in transmission ionisation monitor chambers, which may become crucial for implementing FLASH radiotherapy and its associated quality assurance requirements.

Multipoint-BAX: a new approach for efficiently tuning particle accelerator emittance via virtual objectives

Although beam emittance is critical for the performance of high-brightness accelerators, optimization is often time limited as emittance calculations, commonly done via quadrupole scans, are typically slow. Such calculations are a type of multipoint query, i.e. each query requires multiple secondary measurements. Traditional black-box optimizers such as Bayesian optimization are slow and inefficient when dealing with such objectives as they must acquire the full series of measurements, but return only the emittance, with each query. We propose a new information-theoretic algorithm, Multipoint-BAX, for black-box optimization on multipoint queries, which queries and models individual beam-size measurements using techniques from Bayesian Algorithm Execution (BAX). Our method avoids the slow multipoint query on the accelerator by acquiring points through a virtual objective, i.e. calculating the emittance objective from a fast learned model rather than directly from the accelerator. We use Multipoint-BAX to minimize emittance at the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests II (FACET-II). In simulation, our method is 20× faster and more robust to noise compared to existing methods. In live tests, it matched the hand-tuned emittance at FACET-II and achieved a 24% lower emittance than hand-tuning at LCLS. Our method represents a conceptual shift for optimizing multipoint queries, and we anticipate that it can be readily adapted to similar problems in particle accelerators and other scientific instruments.

Preface

The 12th International Beam Instrumentation Conference, IBIC’23, was hosted by the Canadian Light Source (CLS) in Saskatoon, Saskatchewan, Canada from Sunday, September 10th to September 14th, 2023. IBIC is dedicated to exploring the physics and engineering challenges of beam diagnostic and measurement techniques for particle accelerators. IBIC’23 was attended by 182 delegates from 18 countries. IBIC’23 included 18 invited talks, 18 contributed talks, 2 tutorials, 114 posters, and a 3-day vendor exhibition with 18 industrial exhibitors in attendance. Twenty-five young scientists from all over the globe attended the conference. Nine of these students received grants thanks to sponsorship from the City of Saskatoon, Tourism SK, Discover Saskatoon and Innovation SK and contribution from the industrial exhibitors. The organizers of IBIC’23 are grateful to all sponsors for their valued support.The conference venue was TCU Place, a 104,000-square-foot convention and arts centre situated in downtown Saskatoon. Welcome remarks were delivered by CLS CEO, Bill Matiko, Saskatoon Mayor, Charlie Clark and University of Saskatchewan President Peter Stoicheff and Tonia Batten (CLS), IBIC’23 Conference Chair, opened the conference.The scientific program was developed by a 23-member Scientific Program Committee (SPC). Oral and poster sessions were grouped according to the following nine IBIC classifications. Beam Charge and Current Monitors • Diagnostic systems measuring the average beam current, instantaneous total intensity or individual bunch intensity. Beam Loss Monitors and Machine Protection • Diagnostic systems measuring the average beam loss, instantaneous beam loss or individual bunch loss.• Machine protection architectures based on inputs from beam instrumentation systems, as well as machine protection apparatus such as scrapers, collimators, radiation shields, etc. Beam Position Monitors • Diagnostic systems used for the measurement of beam position: orbit measurement techniques, trajectory measurement techniques, and bunch-by-bunch position measurement systems.• This track includes the use of diagnostics associated with secondary beams, e.g. photon beamlines, to measure the position of the charged particle beam. Data Acquisition and Processing Platforms • Data acquisition systems or architectures of relevance for beam diagnostic systems. This includes acquisition platforms, data processing techniques, electronic component validation or characterization.• Computing platforms, control and acquisition software and operating systems of relevance for beam diagnostics. Feedback Systems and Beam Stability • Systems used to stabilize or control any beam or accelerator parameter either in a closed or open loop. This includes control of orbit, trajectory, longitudinal stability, bunch-by-bunch transverse stability, emittance, tune, chromaticity, etc.• This can include descriptions of the detectors, actuators, any specialized acquisition electronics used to acquire the signal, as well as related data processing techniques. The feedback or feedforward aspects should, however, form a major part of the submission, otherwise, the diagnostic description would be better suited to the track dealing with the primary measurement under discussion. Longitudinal Diagnostics and Synchronization • Diagnostic systems used for the measurement of longitudinal beam parameters such as bunch length, bunch profile, arrival time, energy spread, or longitudinal emittance.• Systems used for beam synchronization and timing distribution. Machine Parameter Measurements • Systems used to measure machine parameters such as betatron tune, chromaticity, higher-order multipoles, space charge, impedance, beam-beam, etc.• Techniques and algorithms used for such measurements.• Other diagnostic devices or techniques which do not clearly match any of the previous tracks. Overview and Commissioning • General description of beam instrumentation devices and systems at new facilities or machine upgrades.• Commissioning results and lessons learned.• Workshop reports related to beam diagnostics. Transverse Profile and Emittance Monitors • Diagnostic systems used for the measurement of transverse beam size, transverse beam profile, transverse emittance, and beam halos.• This track includes both interceptive and non-interceptive diagnostics.The distribution of talks by classification was 5% Beam Charge and Current Monitors, 8% Beam Loss Monitors and Machine Protection, 13% Beam Position Monitors, 16% Data Acquisition and Processing Platforms, 8% Feedback Systems and Beam Stability, 18% Longitudinal Diagnostics and Synchronization, 8% Machine Parameter Measurements, 16% Overview and Commissioning and 8% Transverse Profile and Emittance Monitors.The regional distribution for participation was 37% from the Americas, 18% from Asia and 45% from Europe. The regional distribution of talks was 32% from the Americas, 26% from Asia and 42% from Europe. The gender ratio for oral presentations was 82% male and 18% female. The oral presentations were 79% onsite talks and 21% remote talks.List of Industrial Exhibition, Peer Reviewed Proceedings, IBIC2023, Peer Review General Policies, IBIC 2023 Peer Review Acceptance Criteria, IBIC 2023 Questions posed to referee in SPMS review module and Committees are available in this Pdf.

Demonstration of Autonomous Emittance Characterization at the Argonne Wakefield Accelerator

Transverse beam emittance plays a key role in the performance of high-brightness accelerators. Characterizing beam emittance is often carried out using a quadrupole scan, which fits beam matrix elements to experimental measurements using first-order beam dynamics. Despite its simplicity at face value, this procedure is difficult to automate due to practical limitations. Key issues that must be addressed include maintaining beam size measurement validity by keeping beams within the radius of diagnostic screens, ensuring that measurement fitting produces physically valid results, and accurately characterizing emittance uncertainty. We describe a demonstration of the Bayesian exploration technique towards solving this problem at the Argonne Wakefield Accelerator, enabling a turn-key, autonomous quadrupole scan tool that can be used to quickly measure beam emittances at various locations in accelerators with limited operator input.

Exploring beam size measurement based on the Talbot effect at BEPCII.

Vertical beam size measurements were carried out at Beijing Electron-Positron Collider II (BEPCII) using a phase grating and an absorption grating based on the Talbot effect. The transverse coherence of synchrotron radiation is closely related to beam size. Due to the partial coherence of the synchrotron radiation source, the coherence length can be calculated by measuring the visibility decay of interferograms recorded at different distances behind the gratings. A vertical beam size of 68.19 ± 2 µm was obtained based on the relationship between the coherence length and beam size at the 3W1 beamline of BEPCII. A comparison of the vertical emittance derived from the grating Talbot method and the synchrotron radiation visible light interferometer method was presented. The vertical emittances from the two methods are 1.41 nm rad and 1.40 nm rad, respectively. The 0.1% difference indicates that the grating Talbot method for beam size measurement is reliable. This technique has great potential for small beam size measurement of fourth-generation synchrotron radiation light sources, considering its small diffraction limitation and simple experimental setups.

Development of a novel beam profiling prototype with laser self-mixing via the knife-edge approach

Laser is widely used in industry, biomedical and other kinds of fields. Beam size is the most important parameter among the laser variables. Typical state-of-the-art profiling techniques employ either a scanning-based or camera-based system, using photodiodes or image sensors as the signal receiver. Despite their profiling capabilities, these systems do not tend to be budget-friendly and easy to operate. In this paper, a novel cost-effective beam profiling prototype based on self-mixing interference was developed to measure the Full Width Half Maximum (FWHM) of a range of laser diodes by the knife-edge approach. The difference between our prototype and other systems is that the photodiode is placed behind the laser source, and beam size is calculated by analyzing the feedback signal. A commercial camera beam profiler was used to benchmark our prototype. Results show that though there is a variation of 45.29 % and 65.44 % between the measured beam size and the integrated beam size in the x and y directions due to diffuse and specular reflection, our USD 200 prototype has an accuracy ranging from 89.59 % to 98.74 % on the prediction of laser beam sizes. Our prototype could provide accurate predicted beam size both for Gaussian-alike beam and top-hat-alike beam. This is the very first study to explore the application of self-mixing interference in laser beam profiling. It is believed that our proposed approach has contributed to the on-going development of laser beam profiling methodology.

Noninvasive beam-size measurements for linear induction accelerators

Diamagnetic loops (DML) can be used as a noninvasive method for the measurement of beam size in electron beam accelerators that use solenoidal magnetic transport. The loop fundamentally measures the magnetic flux excluded by a diamagnetic object. A comprehensive theory relates the rms beam radius to the excluded flux measured by the DML. We have built and calibrated a DML apparatus. Recently, this DML has been used to measure the size of the electron beam near the final focus of a flash-radiography linear induction accelerator. The results are in agreement with predictions from transport code simulations. In this article, we review and summarize the construction, calibration, and electron-beam testing of this DML.

Synchrotron radiation interferometry for beam size measurement at low current and in large dynamic range

The Synchrotron Radiation Interferometry (SRI) has become a widely used technique to measure the small transverse size of the electron beam in the storage ring. In a typical SRI system for the routine storage ring operation, synchrotron radiation from a dipole magnet is used to illuminate a double slit with a small slit opening and a relatively large slit separation to form a large number of interference fringes on the observation plane. However, a different type of SRI is needed for intrabeam scattering (IBS) research to measure the beam size at ultralow currents and in a wide dynamic range. Such a system requires a double slit with a large slit opening to increase the light input while having the capability of accurately measuring the beam size with a range of visibility. By examining the impact of the nonuniform wave amplitude of synchrotron radiation and that of the varying visibility (due to a changing beam size) on the beam size measurement, we propose a new physics model for this type of SRI. This new model is validated using simulation, showing significantly improved results when compared with the conventional model. Based on this new model, we have developed and tested an SRI system dedicated to the IBS study on the Duke storage ring. This system has been used successfully to measure electron beams with about $10\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$ of current and with a higher current but a variable size. This new physics model can also improve the measurement accuracy and consistency of the conventional SRIs, especially at low visibility.

Two-dimensional electron beam size measurements with x-ray heterodyne near field speckles

In this paper we report on recent two-dimensional (2D) electron beam size measurements with a nonconventional synchrotron radiation interferometric technique based on x-ray heterodyne near field speckles (HNFS). The method relies on Fourier analysis of the random speckle patterns generated by a water suspension of nanospheres to assess the full 2D transverse coherence of the incoming x rays. The horizontal and vertical electron beam sizes are then retrieved by means of statistical optics approaches. The manuscript thoroughly describes the HNFS technique, and shows experimental results obtained at the ALBA Synchrotron Light Source. By changing the machine coupling, beam sizes as small as $5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ are measured, thus improving on past measurements reported in the literature and proving the HNFS diagnostics suitable for low-emittance particle beams.

Proceedings to the 7th Annual Conference of the Particle Therapy Cooperative Group North America (PTCOG-NA)

Proceedings to the 7th Annual Conference of the Particle Therapy Cooperative Group North America (PTCOG-NA)

Two-Dimensional Beam Size Measurements with X-Ray Heterodyne Near Field Speckles

Two-Dimensional Beam Size Measurements with X-Ray Heterodyne Near Field Speckles

Design and simulation of interferometer for synchrotron radiation beam size measurement

The interferometric measurement of the transverse beam size based on synchrotron radiation is a non-intercepting high precision measurement method. Compared with the imaging method, the interferometric method can measure smaller beam size and get better resolution. It is expected to obtain submicron resolution at shorter measurement wavelength, so it is widely used in synchrotron radiation sources. The upgraded scheme of current interference device in Hefei Light Source HLS-II is presented in this paper. It is proposed to replace the first focusing lens in the original interference light path with an RC structure focusing mirror, and the second single lens with a doublet lens. The design goal of this paper is to reduce dispersion and geometric aberration without changing the optical axis of the optical path, so as to improve the imaging quality of the optical path. The geometrical optical path design is used to evaluate the imaging quality of the optical path, and physical optical simulation is performed to obtain the interference fringes of the measurement system. The simulation results show that the radius of Airy spot is reduced by about 35%, the root mean square radius of dot array is reduced by about 99%, the wavefront difference is reduced by about 75%, and the cutoff frequency of MTF function is increased by about 65%, using a focusing mirror to replace the original focusing lens can greatly improve the image quality of the optical path.

Design Study on Beam Size Measurement System Using SR Interferometry for Low Beam Current

Design Study on Beam Size Measurement System Using SR Interferometry for Low Beam Current

A sub-micron resolution, bunch-by-bunch beam trajectory feedback system and its application to reducing wakefield effects in single-pass beamlines

A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested in the ATF2 beamline of the Accelerator Test Facility at the High Energy Accelerator Research Organization in Japan. The system uses the vertical position of the bunch measured at two beam position monitors (BPMs) to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6 ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350 nm, yielding a local trajectory angle correction to within 250 nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected beam jitter of c. 1 nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of c. 1.6.

Evaluation of GATE-RTion (GATE/Geant4) Monte Carlo simulation settings for proton pencil beam scanning quality assurance.

Geant4 is a multi-purpose Monte Carlo simulation tool for modeling particle transport in matter. It provides a wide range of settings, which the user may optimize for their specific application. This study investigates GATE/Geant4 parameter settings for proton pencil beam scanning therapy. GATE8.1/Geant4.10.3.p03 (matching the versions used in GATE-RTion1.0) simulations were performed with a set of prebuilt Geant4 physics lists (QGSP_BIC, QGSP_BIC_EMY, QGSP_BIC_EMZ, QGSP_BIC_HP_EMZ), using 0.1mm-10mm as production cuts on secondary particles (electrons, photons, positrons) and varying the maximum step size of protons (0.1mm, 1mm, none). The results of the simulations were compared to measurement data taken during clinical patient specific quality assurance at The Christie NHS Foundation Trust pencil beam scanning proton therapy facility. Additionally, the influence of simulation settings was quantified in a realistic patient anatomy based on computer tomography (CT) scans. When comparing the different physics lists, only the results (ranges in water) obtained with QGSP_BIC (G4EMStandardPhysics_Option0) depend on the maximum step size. There is clinically negligible difference in the target region when using High Precision neutron models (HP) for dose calculations. The EMZ electromagnetic constructor provides a closer agreement (within 0.35mm) to measured beam sizes in air, but yields up to 20% longer execution times compared to the EMY electromagnetic constructor (maximum beam size difference 0.79mm). The impact of this on patient-specific quality assurance simulations is clinically negligible, with a 97% average 2%/2mm gamma pass rate for both physics lists. However, when considering the CT-based patient model, dose deviations up to 2.4% are observed. Production cuts do not substantially influence dosimetric results in solid water, but lead to dose differences of up to 4.1% in the patient CT. Small (compared to voxel size) production cuts increase execution times by factors of 5 (solid water) and 2 (patient CT). Taking both efficiency and dose accuracy into account and considering voxel sizes with 2mm linear size, the authors recommend the following Geant4 settings to simulate patient specific quality assurance measurements: No step limiter on proton tracks; production cuts of 1mm for electrons, photons and positrons (in the phantom and range-shifter) and 10mm (world); best agreement to measurement data was found for QGSP_BIC_EMZ reference physics list at the cost of 20% increased execution times compared to QGSP_BIC_EMY. For simulations considering the patient CT model, the following settings are recommended: No step limiter on proton tracks; production cuts of 1mm for electrons, photons and positrons (phantom/range-shifter) and 10mm (world) if the goal is to achieve sufficient dosimetric accuracy to ensure that a plan is clinically safe; or 0.1mm (phantom/range-shifter) and 1mm (world) if higher dosimetric accuracy is needed (increasing execution times by a factor of 2); most accurate results expected for QGSP_BIC_EMZ reference physics list, at the cost of 10-20% increased execution times compared to QGSP_BIC_EMY.

Measuring the Emittance of a Charged-Particle Beam in a Small Linear Accelerator

A “non-contact” method for measuring the emittance of a corpuscular flow extracted from the Penning ion source of a small linear charged-particle accelerator has been developed and tested. The emittance is calculated by minimizing the difference between the theoretically calculated and experimentally measured beam sizes in the ion-optical system of the accelerator. The dimensions are measured during photographic recording of a luminous trace of a corpuscular flow in the ion-optical system. The results of applying the non-contact method for measuring the emittance of a particle beam flow are presented.

Review of Transverse Beam Profile Measurements Using Synchrotron Radiation

Abstract –Synchrotron radiation (SR) is a tool for non-destructive beam diagnostics since its characters are substantially related to those of the source beam. The spectrum of SR is extremely intense and extends over a broad energy range from the infrared through the visible and ultraviolet, into the soft and hard X-ray regions of the electromagnetic spectrum. The visible light (400 – 800 nm) and X-ray (0.05 – 0.3 nm) regions are used in the beam instrumentation. In the visible light region, transverse beam profile or size diagnostics can be done by an interferometer (light is observed as a wave). Meanwhile, in the submicron beam size measurements, the X-ray SR monitor is commonly used. This paper reports the review of transverse beam profile measurements using SR covering principles and practical experiences with the technique at some accelerator facilities such as Photon Factory, Diamond Light Source, CesrTA, and SuperKEKB. Key words: accelerator, beam instrumentation, transverse beam profile, synchrotron radiation, X-ray, visible light