Beam Diagnostics Research Articles

Diagnostics of Spin-Polarized Ions at Storage Rings

Polarized heavy ions in storage rings are seen as a valuable tool for a wide range of research, from the study of spin effects in relativistic atomic collisions to the tests of the Standard Model. For forthcoming experiments, several important challenges need to be addressed to work efficiently with such ions. Apart from the production and preservation of ion polarization in storage rings, its measurement is an extremely important issue. In this contribution, we employ the radiative recombination (RR) of polarized electrons into the ground state of initially hydrogen-like, finally helium-like, ions as a probe process for beam diagnostics. Our theoretical study clearly demonstrates that the RR cross section, integrated over photon emission angles, is highly sensitive to both the degree and the direction of ion polarization. Since the (integrated) cross-section measurements are well established, the proposed method offers promising prospects for ion spin tomography at storage rings.

KALYPSO LGAD — a MHz repetition rate line camera based on trenchisolated low gain avalanche detector

Designed for accelerator beam diagnostics and photon science applications, KALYPSO is a line array camera that stands out for its high-speed performance with the ability to operate at rates up to 12 Mfps in continuous readout mode while maintaining full occupancy. In this contribution, the KALYPSO system with sensor based on TI-LGAD is presented. The latest version of this system is employed as a beam diagnostic imaging sensor to measure radiation profiles of the particle beam at the KIT accelerator, KARA. The system's key features will be presented, including its linearity, sensitivity, and dynamic range.

Fluorescent nanodiamond scintillators for beam diagnostics of EUV and soft X-ray in photolithographic applications.

Extreme ultraviolet (EUV) lithography is a cutting-edge technology in contemporary semiconductor chip manufacturing. Monitoring the EUV beam profiles is critical to ensuring consistent quality and precision in the manufacturing process. This study uncovers the practical use of fluorescent nanodiamonds (FNDs) coated on optical image sensors for profiling EUV and soft X-ray (SXR) radiation beams. We employed a positive electrospray ion source to deposit 100 nm FNDs onto indium tin oxide (ITO)-coated substrates, forming 1 μm thick films. The scintillation films exhibited approximately 50% transparency in the visible region and could emit red fluorescence from neutral nitrogen-vacancy (NV0) centers in the FNDs when exposed to EUV/SXR radiation. We evaluated the performance of a device featuring an FND coating on a fiber optic plate (FOP) attached to the sensor of a complementary metal-oxide semiconductor (CMOS) camera using synchrotron radiation across the 80-1400 eV energy range. At 91.8 eV (or a wavelength of 13.5 nm), the fiber-coupled device exhibited a noise-equivalent power density of 0.25 μW cm-2 Hz-1/2, approximately eight times lower than that of an f/1.0 lens-coupled system. This enhanced sensitivity makes the FND/FOP-based detection system useful for beam profiling of various EUV/SXR radiation sources. Our results highlight the promising potential of electrosprayed FND scintillators as a cost-effective and versatile diagnostic tool for advancing next-generation photolithography.

Determination of the XUV Frequency Chirp at the Free-Electron Laser FLASH via THz Streaking and Electron Beam Diagnostics

Free-electron lasers (FELs) operating in the extreme ultraviolet (XUV) and X-ray regions deliver ultrashort pulses with unprecedented intensity, enabling groundbreaking research across various scientific disciplines. A potential chirp (frequency change within the pulse) of these pulses influences their spectral properties, directly impacting the experimental outcomes and FEL performance. The accurate characterization of the chirp is, therefore, important for optimizing FEL operation and interpreting experimental results. This study presents a comprehensive comparison of two techniques determining the chirp of the XUV pulses at FLASH by directly measuring the XUV pulses with THz streaking and by detecting the chirp of the electron bunches by a Transverse Deflection Structure (PolariX TDS) to infer the XUV chirp. We conducted simultaneous measurements using both techniques at FLASH2 while tuning the FEL to produce various energy chirps on the electron bunch.

Progress using collective Thomson scattering of microwave radiation to detect fast ions and plasma instabilities at the GDT open magnetic trap

For the big mirror magnetic trap (Gas-Dynamic Trap, Budker Institute, Russia), a system for recording of collective Thomson scattering spectra of microwave radiation has been developed to focus on the study of velocity distribution function of fast ions. A diagnostic complex includes a high-power 450 kW/54.5 GHz gyrotron as a source of probing radiation, two independent highly sensitive radiometers operating in the range of 54.47 ± 0.55 GHz for simultaneous registration of scattered radiation in two orthogonal geometries, and quasi-optical systems for focusing the probing and diagnostic microwave beams. We report the results of the last experimental campaign of 2023 with plasma heating by neutral beams, in which the scattering signals from the fast ions have been detected accompanied by high-frequency instability of plasma.

Performance assessment of ionization chambers in standard diagnostic radiology beams through the determination of calibration coefficients

Dosimetry laboratories use reference ionization chambers (ICs) as their primary instruments for measuring radiation doses. The ICs are designed to have defined and accurate response characteristics, making them suitable for calibrating radiation detectors in specific beam qualities. This study assesses six ionization chambers (Radcal 10X6-3CT, Radcal 10X6-M, Radcal 10X6-10, Radcal 10X6-6, Exradin A4, and FC-65-G1) in standard International Electrotechnical Commission (IEC) defined diagnostic beams [RQR, RQA, RQT, and RQR-M (W + Al)] at the Secondary Standard Dosimetry Laboratory (SSDL). Calibration coefficients were estimated to evaluate energy dependency and relative response deviations of the ICs. Results showed that most ICs tested had limited energy dependency in RQR, RQA, and RQT beams, with deviations under 5%, confirming their suitability for clinical dosimetry and reference calibration at the SSDL. The Radcal 10X6-M performed well in mammography beams, while the other ICs showed significant deviations (6%–107%) in RQR-M (W + Al), limiting their mammography use. A key finding is the extended applicability of certain ICs beyond their specified energy ranges, particularly the Radcal 10X6-3CT, Radcal 10X6-M, and Radcal 10X6-10, which performed well in a broader range of diagnostic beam energies. This study provides essential data for optimizing IC selection and calibration, and highlights the need for further development of energy-independent ICs for enhanced versatility across clinical settings.

Rate-induced aging effects on Parallel-Plate Avalanche Counter (PPAC) caused by heavy ion beams

The Facility for Rare Isotope Beams (FRIB) is one of the premier scientific user facilities for nuclear science with radioactive beams, capable of producing most (approximately 80%) of the isotopes expected to exist, from oxygen to uranium, at energies up to 200 MeV/u. With the increase in beam power from the present 10 kW to the planned 400 kW, FRIB experiments are about to enter a new era. An unprecedented rate capability as well as stable performance of all the planned instrumentation intended for beam diagnostics and beam tuning is required at the expected high beam intensities (>1 MHz). A summary of aging phenomena at high heavy-ion beam rates observed in the Advanced Rare Isotope Separator (ARIS) detectors for beam diagnostics, including Parallel Plate Avalanche Counters (PPAC) and plastic scintillation for time-of-flight measurements, is discussed. Current research and development project to mitigate rate-induced aging are presented.

GaAs-based antenna-coupled field effect transistors as direct THz detectors across a wide frequency range from 0.2 to 29.8 THz

High-power coherent terahertz (THz) radiation from accelerator facilities such as free-electron lasers (FELs) is frequently used in pump-probe experiments where the pump or probe (or both) signals are intense THz pulses. Detectors for these applications have unique requirements that differ from those of low-power table-top systems. In this study, we demonstrate GaAs antenna-coupled field effect transistors (FETs) as a direct THz detector operating across a broad frequency spectrum ranging from 0.2 THz to 29.8 THz. At approximately 0.5 THz, the maximum current responsivity (ℜ I ) of 0.59 mA/W is observed, signifying a noise equivalent power (NEP) of 2.27 nW/√Hz. We report an empirical roll-off of f−3 for an antenna-coupled GaAs TeraFET detector. Still, NEP of 0.94 μW/√Hz and a current responsivity ℜ I = 1.7μA/W is observed at 29.8 THz, indicating that with sufficient power the FET can be used from sub-mm wave to beyond far-infrared frequency range. Current and voltage noise floor of the characterized TeraFET is 2.09 pA and 6.84 μV, respectively. This characteristic makes GaAs FETs more suitable for applications requiring higher frequencies, ultra-broadband capabilities and robustness in the THz domain, such as beam diagnostics and alignment at particle accelerators.

Numerical and Experimental Simulation of Supersonic Gas Outflow into a Low-Density Medium

This study is aimed at developing methods for the experimental and numerical simulation of the outflow of underexpanded gas jets into a rarefied medium. The numerical method is based on using Navier–Stokes equations in the continuum flow regime and the direct simulation Monte Carlo method in the transitional flow regime. The experimental method includes the modeling of jet flows in the LEMPUS-2 gas-dynamic setup with electron beam diagnostics for the jet density measurements. The results of the experimental modeling for the nozzles of various diameters confirm that a key parameter determining the jet structure is the Reynolds number based on the characteristic length ReL. The results of the numerical simulations agree well with the experimental data both for the maximum values of the ReL considered (approximately 30) when a barrel jet structure with Mach disks is formed and for the minimum values (approximately 4) when no Mach disks are formed. In the entire range of parameters, significant thermal nonequilibrium is observed at all jet segments where the measurements are performed.

Development of a low energy loss micro-channel plate based position-sensitive detector for the Rare Radio-Isotope Ring

A position-sensitive micro-channel plate type detector has been developed for use in the Rare Radio-Isotope Ring at RIKEN, Japan. It uses secondary electrons emitted from a conversion foil and deflected at 90° to create a position signal. Design constraints included operation in a high-vacuum, a large area to cover the ring acceptance and low beam interaction to reduce energy loss. It must achieve a precision sufficient to measure the in-ring dispersion and perform position diagnostics for tuning the injection. Reducing the time-of-flight of secondary electrons was principal in improving resolution as it reduces their final Gaussian spread. This was implemented by compacting the geometry of the detector and raising the acceleration potential. Electric field homogeneity was also improved by decreasing the electrostatic grid wire pitch from 2 mm to 1 mm. Offline tests with alpha sources and online tests with a 200 MeV/u 84Kr beam were conducted, reaching a final average position resolution of σ = 1.3 mm. This is sufficient for conducting beam diagnostics in the storage ring.

Development of a compact neutron spectrometer based on multi-element activation

In recent years, due to the introduction of accelerator-based facilities, the interest of the medical and scientific communities in the Boron Neutron Capture Theraphy (BNCT) dramatically increased. As far as beam diagnostics is concerned, the availability of spectrometry techniques adapted to BNCT is required for quality assurance and daily control measurements. This work aims to present a novel compact spectrometer with an isotropic response called Neutron Capture Therapy- Activation Compact Spectrometer (NCT-ACS), funded by INFN, highly sensitive in the energy interval ranging from thermal to 100 keV and suitable for in-phantom irradiation. The detector characteristics and the experimental results collected at the Torino neutron facility are shown.

Use of the Nanogate‑38 Camera for Beam Diagnostics at the VEPP‑2000 Collider

Use of the Nanogate‑38 Camera for Beam Diagnostics at the VEPP‑2000 Collider

Diagnostic Challenges and Management of Non-Odontogenic Toothache: A Case of Unilateral Pansinusitis Mimicking Dental Pain

This case report details the diagnostic challenge and subsequent management of a 38-year-old male patient who presented with severe, sharp, and non-localized pain in the right maxillary distal area. Initial¬ly unresponsive to non-steroidal anti-inflammatory drugs and antibiotics, the patient’s symptoms deviat¬ed from typical odontogenic pain characteristics. Comprehensive dental examinations revealed minimal pathologies, challenging initial assumptions of dental-origin pain. Advanced diagnostic imaging, including Orthopantomography and Cone Beam Computed Tomography (CBCT), was pivotal in identifying unilat¬eral pansinusitis, with notable obstruction in the maxillary, ethmoid, and frontal sinuses. Further microbi¬ological analysis confirmed a Staphylococcus aureus and anaerobic infection, refocusing the diagnosis to a non-odontogenic source. The patient underwent a targeted 14-day complex antibiotic regimen, supple¬mented with local treatments including Nasonex nasal spray and saline nasal irrigations. This integrative approach resulted in marked symptom improvement and was instrumental in the patient’s recovery. This case highlights the critical need for thorough evaluation in distinguishing between odontogenic and non-od¬ontogenic sources of orofacial pain, ensuring accurate diagnosis and effective treatment.

Characterising Sinonasal Pneumatization in Patients with Nasal Septal Deviation: A CBCT-Based Study.

This study aimed to investigate the presence and correlation of paranasal sinus pneumatization among patients with and without nasal septal deviations (NSD), to enhance clinical understanding of sinonasal anatomical variations. It is descriptive, retrospective study under a monocentric, utilizing institutional archives. 30 subjects with NSD and 30 without NSD were selected. Inclusion criteria required diagnostic quality Cone Beam Computed Tomography (CBCT) images, while exclusion criteria included developmental anomalies, central pathology, previous sinonasal surgery, fractures, and non-diagnostic images. The Assessment of Pneumatization of the Paranasal Sinuses (APPS) score was used to evaluate anatomical variations in paranasal sinuses based on CBCT scans. Statistical analysis was performed using the Chi-square test and independent t-test via SPSS version 23. A significant association between NSD and certain anatomical variations was observed. Notably, higher prevalence rates of variations such as pneumatization of the maxillary floor, middle turbinate concha bullosa, and superior frontal sinus wall were found in subjects with NSD. Statistical significance was confirmed in seven out of nine parameters, with p-values < 0.001 for most comparisons. The left side exhibited greater pneumatization than the right. The total APPS scores showed strong statistical significance between groups (p < 0.001). The study reveals a significant relationship between nasal septal deviation and paranasal sinus pneumatization, suggesting that septal deviations may influence the extent of pneumatization in the sinonasal complex.

Conditional guided generative diffusion for particle accelerator beam diagnostics

Advanced accelerator-based light sources such as free electron lasers (FEL) accelerate highly relativistic electron beams to generate incredibly short (10s of femtoseconds) coherent flashes of light for dynamic imaging, whose brightness exceeds that of traditional synchrotron-based light sources by orders of magnitude. FEL operation requires precise control of the shape and energy of the extremely short electron bunches whose characteristics directly translate into the properties of the produced light. Control of short intense beams is difficult due to beam characteristics drifting with time and complex collective effects such as space charge and coherent synchrotron radiation. Detailed diagnostics of beam properties are therefore essential for precise beam control. Such measurements typically rely on a destructive approach based on a combination of a transverse deflecting resonant cavity followed by a dipole magnet in order to measure a beam’s 2D time vs energy longitudinal phase-space distribution. In this paper, we develop a non-invasive virtual diagnostic of an electron beam’s longitudinal phase space at megapixel resolution (1024 × 1024) based on a generative conditional diffusion model. We demonstrate the model’s generative ability on experimental data from the European X-ray FEL.

A conditional latent autoregressive recurrent model for generation and forecasting of beam dynamics in particle accelerators

Particle accelerators are complex systems that focus, guide, and accelerate intense charged particle beams to high energy. Beam diagnostics present a challenging problem due to limited non-destructive measurements, computationally demanding simulations, and inherent uncertainties in the system. We propose a two-step unsupervised deep learning framework named as Conditional Latent Autoregressive Recurrent Model (CLARM) for learning the spatiotemporal dynamics of charged particles in accelerators. CLARM consists of a Conditional Variational Autoencoder transforming six-dimensional phase space into a lower-dimensional latent distribution and a Long Short-Term Memory network capturing temporal dynamics in an autoregressive manner. The CLARM can generate projections at various accelerator modules by sampling and decoding the latent space representation. The model also forecasts future states (downstream locations) of charged particles from past states (upstream locations). The results demonstrate that the generative and forecasting ability of the proposed approach is promising when tested against a variety of evaluation metrics.

Evaluation of the measurement accuracy and uncertainty of a solid-state detector under diagnostic x-ray beam conditions.

An accurate measurement of x-ray beams is expected to reduce the uncertainties associated with estimating radiation risk to patients in clinical settings. To perform assessment tasks based on the readings of a solid-state detector (SSD) using semiconductor technology, the characteristics of the detector should be elucidated. In this study, we evaluated the measurement accuracy of a new SSD under diagnostic x-ray beam conditions in terms of air kerma, tube voltage, and half-value layer (HVL). The performance of the SSD was then compared with those of reference instruments. The tube voltage was varied within the range of 50-120kV in steps of 10kV and the thickness and materials of additional filters were concurrently changed (several combinations were tested). In addition, the dose rate and energy dependence of the SSD were also investigated. These effects were analyzed based on statistical significance tests. Furthermore, the expanded uncertainties in the series of measurements were meticulously calculated. The results showed average relative differences of -3.26±1.33%, 0.44±1.01%, and -2.60±3.31% for air kerma, tube voltage, and HVL, respectively. Furthermore, air kerma did not exhibit any dependence on dose rate and energy, in contrast to tube voltage and HVL measurements. The measurement values of the SSD fall within the acceptable range of uncertainty, highlighting its measurement accuracy and reliability. Furthermore, based on the characteristics elucidated by this study, valuable insights are provided concerning the assurance of appropriate measurement values in clinical settings.

5D tomographic phase-space reconstruction of particle bunches

We propose a new beam diagnostics method to reconstruct the phase space of charged particle bunches in five dimensions, which consist of the horizontal and vertical positions and divergences as well as the time axis. This is achieved by combining a quadrupole-based transverse phase-space tomography with the adjustable streaking angle of a polarizable X-band transverse deflection structure. We demonstrate with detailed simulations that the method is able to reconstruct various complex phase-space distributions and that the quality of the reconstruction depends on the number of input projections. This method allows for the identification and visualization of previously unnoticed detailed features in the phase-space distribution and can thereby be used as a tool toward improving the performance of particle accelerators or performing more accurate simulation studies. Published by the American Physical Society 2024

Charge exchange recombination spectroscopy on the alkali beam of Wendelstein 7-X.

Measurements of ion temperature profiles are required to assess the energy and particle transport processes in the Wendelstein 7-X stellarator. This device is equipped with a diagnostic alkali beam, which can be utilized to determine local impurity temperatures and densities by Charge Exchange Recombination Spectroscopy (CXRS). It could provide such profiles in the edge plasma, where other diagnostics are less efficient. With this contribution, first results of CXRS measurements on the sodium beam from the scientific operation phase OP2.1 are presented. The spectroscopic system was in commissioning phase lacking some of the final optical components. Thus, the aim of the diagnostics during this campaign was to explore the measurement capabilities. Based on the processed spectra, the prospects of C5+ and C6+ ion temperature and concentration measurements are discussed. The results indicate that with the final optical setup under installation, the diagnostics could provide ion temperature profiles in the edge with 3mm radial resolution and at least 1s temporal resolution.

Feasibility of using optical Cherenkov radiation for non-relativistic ion beam diagnostics

In this paper, we propose to use quasi-monochromatic Cherenkov spectral lines for ion beam diagnostics. As representatives of light and heavy ions, we use C12 and Au197 ions, respectively. First, using the Geant4 toolkit, we determine the ionization lost energy as a function of the radiator penetration depth. After that, we use those data in the polarization currents method to compare the theoretical spectral lines with and without ionization losses. We also use the real-beam polarization currents method to analyze real-beam and setup parameters affecting the accuracy of the beam diagnostics. We emphasize that the precision of refractive index measurement might be a source of inaccuracy in ion beam diagnostics. Nevertheless, according to the provided data, we can expect that the method for measuring Cherenkov quasi-monochromatic spectral lines should be applicable for beam-diagnostics purposes, especially for lighter ions.