Instruments, Volume 3, Issue 1 (March 2019) – 23 articles

Open-source Multiwavelength Analytical Ultracentrifugation (MWL-AUC) detection systems have been evolving for over a decade. Continual advances emerging out of several research groups have brought the instrumentation technology to increasingly higher levels of performance. The capabilities of MWL-AUC have been documented in many publications, demonstrating the applicability of broad spectrum absorbance acquisitions in analytical ultracentrifugation to a wide array of scientific fields. Despite numerous examples of the usefulness and unique advantages of MWL-AUC, the adoption of the technology by more research groups has been slow. The complexity of the hardware, integration within an ultracentrifuge platform and lack of practical construction and operational information is the likely source of reluctance. Here, we clearly describe the challenges facing a researcher considering adopting MWL-AUC technology in their own laboratories, and provide the information necessary to implement and operate a MWL-AUC system. The discussion includes details of detector assembly, optical alignment, and acquisition parameter settings necessary to achieve high quality experimental results. Full article

Dedicated high-beta optics are used to make forward proton scattering measurements possible at the LHC. Following a short general introduction and history of special high-beta optics and running conditions, we describe the two types of special high-beta runs planned for 2018. A run at top energy at ${\beta }_y^{*}=90\mathrm{m}$ for elastic and diffractive scattering, and a low energy run to measure the rho-parameter in the Coulomb interference region. Full article

Magnetron sputtering is proposed here as an innovative method for the deposition of a material layer onto an appropriate backing plate for cyclotron solid targets aimed at medical radioisotopes production. In this study, a method to deposit thick, high-density, high-thickness-uniformity, and stress-free films of high adherence to the backing was developed by optimizing the fundamental deposition parameters: sputtering gas pressure, substrate temperature, and using a multilayer deposition mode, as well. This method was proposed to realize Mo-100 and Y-nat solid targets for biomedical cyclotron production of Tc-99m and Zr-89 radionuclides, respectively. The combination of all three optimized sputtering parameters (i.e., 1.63 × 10⁻² mbar Ar pressure, 500 °C substrate temperature, and the multilayer mode) allowed us to achieve deposition thickness as high as 100 µm for Mo targets. The 50/70-µm-thick Y targets were instead realized by optimizing the sputtering pressure only (1.36 × 10⁻² mbar Ar pressure), without making use of additional substrate heating. These optimized deposition parameters allowed for the production of targets by using different backing materials (e.g., Mo onto copper, sapphire, and synthetic diamond; and Y onto a niobium backing). All target types tested were able to sustain a power density as high as 1 kW/cm² provided by the proton beam of medical cyclotrons (15.6 MeV for Mo targets and 12.7 MeV for Y targets at up to a 70-µA proton beam current). Both short- and long-time irradiation tests, closer to the real production, have been realized. Full article

This work presents a simple method for determining the energy of the proton beam in biomedical cyclotrons, using no additional experimental set-up and only materials from radioisotope routine productions that are therefore available on-site. The developed method requires neither absolute efficiency calibration nor beam current measurements, thus avoiding two major sources of uncertainty. Two stacks composed of natural titanium thin foils, separated by an energy degrader of niobium, were mounted in a commercial target and irradiated. The resulting activities of ⁴⁸V were assessed by a HPGe spectrometer. Full article

The possibility of performing proton radiography by using the proton angular spread due to Coulomb multiple scattering was investigated, for the first time, with an emulsion film detector. Two different phantoms were irradiated with the therapeutic proton beam at the Paul Scherrer Institut (PSI) in Villigen, Switzerland. The first one is a simple polymethylmethacrylate (PMMA) block having two different thicknesses (4 cm and 3 cm), and the second one is a PMMA cube with five aluminum rods embedded along a diagonal. Only one emulsion film was needed to perform the radiography, an important issue as the analysis of this kind of detector is time-consuming. Furthermore, the method showed an enhanced contrast when high atomic-number materials are traversed. This gives an advantage, when compared to proton range radiography. Full article

With recent impressive clinical results of targeted alpha therapy using ²²⁵Ac, significant effort has been directed towards providing a reliable and sufficient supply of ²²⁵Ac to enable widespread using of ²²⁵Ac-radiopharmaceuticals. TRIUMF has begun production of ²²⁵Ac via spallation of thorium metal with 480 MeV protons. As part of this program, a new ²²⁵Ac-production target system capable of withstanding the power deposited by the proton beam was designed and its performance simulated over a range of potential operating parameters. Special attention was given to heat transfer and stresses within the target components. The target was successfully tested in two irradiations with a 72–73 µA proton beam for a duration of 36.5 h. The decay corrected activity at end of irradiation (average ± standard deviation) was (524 ± 21) MBq (14.2 mCi) and (86 ± 13) MBq (2.3 mCi) for ²²⁵Ac and ²²⁵Ra, respectively. These correspond to saturation yields of 72.5 MBq/µA for ²²⁵Ac and 17.6 MBq/µA for ²²⁵Ra. Longer irradiations and production scale-up are planned in the future. Full article

A closed-loop technology aiming at recycling the highly ¹⁰⁰Mo-enriched molybdenum target material has been developed in the framework of the international research efforts on the alternative, cyclotron-based ^99mTc radionuclide production. The main procedure steps include (i) ¹⁰⁰Mo-based target manufacturing; (ii) irradiation under proton beam; (iii) dissolution of ¹⁰⁰Mo layer containing ^9×Tc radionuclides (produced by opened nuclear reaction routes) in concentrated H₂O₂ solution; and (iv) Mo/Tc separation by the developed radiochemical module, from which the original ¹⁰⁰Mo comes as the “waste” alkaline aqueous fraction. Conversion of the residual ¹⁰⁰Mo molybdates in this fraction into molybdic acids and MoO₃ has been pursued by refluxing in excess of HNO₃. After evaporation of the solvent to dryness, the molybdic acids and MoO₃ may be isolated from NaNO₃ by exploiting their different solubility in water. When dried in vacuum at 40 °C, the combined aqueous fractions provided MoO₃ as a white powder. In the last recovery step MoO₃ has been reduced using a temperature-controlled reactor under hydrogen overpressure. An overall recovery yield of ~90% has been established. Full article

A new solid target system for the TRIUMF TR13 cyclotron that can accommodate target discs with a 1-2-mm thickness and a 28-mm diameter has been developed. The target system design is based on a modified clamping mechanism of a KF-40 vacuum connector, and comprises an easy and quick ejection mechanism for the target plate. The new quick-release target system decreases the retrieval time of the irradiated target to less than 1 minute and is expected to reduce the radiation burden to operating staff by a factor of ~10. Full article

Silicon photomultipliers (SiPMs) are single-photon sensitive solid-state detectors that are becoming popular for several applications, thanks to massive performance improvements over the last years. Starting as a replacement for the photomultiplier tube (PMT), they are now used in medical applications, big high-energy physics experiments, nuclear physics experiments, spectroscopy, biology and light detection and ranging (LIDAR) applications. Due to different requirements in terms of detection efficiency, noise, etc., several optimizations have been introduced by the manufacturers; for example, spectral sensitivity has been optimized for visible light, near ultraviolet, vacuum ultraviolet, and near infrared light. Each one of them require specific processes and structural optimization. We present in this paper recent improvements in SiPM performance, owing to a higher cell fill-factor, lower noise, improved silicon materials, and deep trench isolation. We describe issues related to the characterization of analog SiPM, particularly due to the different sources of correlated noise, which have to be distinguished from each other and from the primary pulses. We also describe particular analyses and optimizations conducted for specific applications like the readout of liquid noble gas scintillators, requiring these detectors to operate at cryogenic temperatures. Full article

A significant number of medical radioisotopes use solid, often metallic, parent materials. These materials are deposited on a substrate to facilitate the cooling and handling of the target during placing, irradiation, and processing. The processing requires the transfer of the target to a processing area outside the irradiation area. In this new approach the target is processed at the irradiation site for liquid only transport of the irradiated target material to the processing area. The design features common to higher energy production target systems are included in the target station. The target is inclined at 14 degrees to the beam direction. The system has been designed to accept an incident beam of 15 to 16 mm diameter and a beam power between 2 and 5 kW. Thermal modeling is presented for targets of metals and compounds. A cassette of five or 10 prepared targets is housed at the target station as well as a target dissolution assembly. Only the dissolved target material is transported to the chemistry laboratory so that the design does not require additional irradiation area penetrations. This work presents the design, construction, and modeling details of the assembly. A full performance characterization will be reported after the unit is moved to a cyclotron facility for beam related measurements. Full article

This paper describes a design approach to a control system of power supply for high-voltage electrochemical processes such as plasma electrolytic oxidation (PEO) or high-voltage anodising (HVA), which require alternating polarisation pulses up to 750 V and a typical current density of 50–500 mA/cm². Complex characteristics of the electrochemical system response on applied polarisations (positive or negative) cause necessity of precise control of polarising pulse shapes for better process operation and its understanding. A device performs cycle-by-cycle pulse-width modulation (PWM) control, including feedback based on digital analysis of the instantaneous current and/or voltage output, and the desired pulse waveform stored in memory for each output polarity. The output stage has four states corresponding to positive or negative pulses, as well as open- or short-circuit conditions, with respect to an electrochemical cell. A fully programmable controller allows one to generate arbitrary waveforms, as well as their sequences, by means of “regime designer” software. Moreover, a smart feedback system can provide adaptation of the next pulse parameter from analysis of the process prehistory. For instance, this approach allows one to separate main electrochemical process (coating formation) and diagnosis of the phenomenon through introduction of high-voltage triangular voltage sweep pulse within a pause of the main process, which is normally carried out under a current control. Full article

A 3D-printed metal solid target using additive manufacturing process is a cost-effective production solution to complex and intricate target design. The initial proof-of-concept prototype solid target holder was 3D-printed in cast alloy, Al–7Si–0.6Mg (A357). However, given the relatively low thermal conductivity for A357 (κ_max, 160 W/m·K), replication of the solid target holder in sterling silver (SS925) with higher thermal conductivity (κ_max, 361 W/m·K) was investigated. The SS925 target holder enhances the cooling efficiency of the target design, thus achieving higher target current during irradiation. A validation production of ⁶⁴Cu using the 3D-printed SS925 target holder indicated no loss of enriched ⁶⁴Ni from proton bombardment above 80 µA, at 11.5 MeV. Full article

In solid targets for radioisotope production, the parent materials—mostly metallic—are usually attached to a substrate (metal part, often copper or silver) to support it during handling and irradiation and to facilitate liquid or gas cooling to remove the heat generated by the particle beam. This cladding process is most frequently done by electroplating. One of the biggest challenges of preparing solid, high-current, ¹⁰⁰Mo targets is the difficulty of cladding the substrate with molybdenum—metal that cannot be electroplated. A number of cladding techniques are used with varying degrees of complexity, success, and cost. A simple cladding process, especially suitable for the production of radioisotope targets, was developed. The process uses a metal slurry (metal powder and binder) painted on the substrate and heated in a hydrogen atmosphere where the metal is sintered and diffusion-bound to the substrate in a single step. Full article

Gallium-68 is a popular radioisotope for positron emission tomography. To make gallium-68 more accessible, we developed a new solid target for medical cyclotrons. Fused zinc targets promise a new, efficient, and reliable technique without the downsides of other commonly used time-consuming methods for solid target fabrication, such as electroplating and sputtering. We manufactured targets by fusing small pressed zinc pellets into a recess in aluminum backings. Using a simple hotplate, the fusing could be accomplished in less than two minutes. Subsequently, the targets were cooled, polished, and used successfully for test irradiations at E_p = 12.8 MeV and up to 20 µA proton current. Full article

A new Center for Radiopharmaceutical Cancer Research was established at the Helmholtz-Zentrum Dresden-Rossendorf in order to centralize radionuclide production, radiopharmaceutical production and the chemical and biochemical research facilities. The newly installed cyclotron is equipped with two beamlines, two target selectors and several liquid, gas and solid target systems. The cyclotron including the target systems and first results of beam characterization measurements as well as results of the radionuclide production are presented. The produced radionuclides are automatically distributed from the targets to the destination hot cells. This process is supervised and controlled by an in-house developed system. Full article

Boron nitride nanotubes (BNNTs) were investigated as a target media for cyclotron production of ¹¹C for incident beam energy at or below 11 MeV. Both the ¹¹B(p,n)¹¹C and ¹⁴N(p,α)¹¹C nuclear reactions were utilized. A sweep gas of nitrogen or helium was used to collect recoil escape atoms with a desired form of ¹¹CO₂. Three prototype targets were tested using an RDS-111 cyclotron. Target geometry and density were shown to impact the saturation yield of ¹¹C and percent of yield recovered as carbon dioxide. Physical damage to the BNNT target media was observed at beam currents above 5 μA. Additional studies are needed to identify operating conditions suitable for commercial application of the method. Full article

The production of ⁹⁷Ru, a potential Single Photon Emission Computed Tomography (SPECT) radioisotope, was studied at ARRONAX. The cross-section of ^natMo(α,x)⁹⁷Ru reaction was investigated in the range of 40–67 MeV irradiating the ^natMo and Al stacked-foils. The activities of ⁹⁷Ru and other radioactive contaminants were measured via gamma spectroscopy technique. A global good agreement is observed between obtained cross-section results, previously reported values and TENDL-2017 predictions. Additionally, Radionuclide Yield Calculator, a software that we made available for free, dedicated to quickly calculate yields and plan the irradiation for any radioisotope production, was introduced. The yield of investigated nuclear reactions indicated the feasibility of ⁹⁷Ru production for medical applications with the use of α beam and Mo targets opening the way to a theranostic approach with ⁹⁷Ru and ¹⁰³Ru. Full article

Cyclotrons are an important tool for accelerator sciences including the production of medical isotopes for imaging and therapy. For their successful and cost-efficient operation, the planned and unplanned down time of the cyclotron needs to be kept at a minimum without compromising reliability. One of the often required maintenance activities is the replacement of the filament in the ion source. Here, we are reporting on a new ion source filament tested on a medical cyclotron and its prolonging effect on the ion source operation. Full article

Accurate knowledge of the beam energy distribution is crucial for particle accelerators, compact medical cyclotrons for the production of radioisotopes in particular. For this purpose, a compact instrument was developed, based on a multi-leaf Faraday cup made of thin aluminum foils interleaved with plastic absorbers. The protons stopping in the aluminum foils produce a measurable current that is used to determine the range distribution of the proton beam. On the basis of the proton range distribution, the beam energy distribution is assessed by means of stopping-power Monte Carlo simulations. In this paper, we report on the design, construction, and testing of this apparatus, as well as on the first measurements performed with the IBA Cyclone 18-MeV medical cyclotron in operation at the Bern University Hospital. Full article

Microwave SQUID (Superconducting QUantum Interference Device) multiplexing is a suitable technique for reading a large number of detector channels, using only a few connecting lines. In the HOLMESexperiment, this is based on inductively coupled rf-SQUIDs fed by TES (Transition Edge Sensors). Operation of the whole rf-SQUID chain is achieved with a single transmission line, by means of the recently introduced flux-ramp modulation technique—a sawtooth signal which allows signal reconstruction while operating the rf-SQUIDs in an open loop condition. Due to the crucial role of the sawtooth signal, it is very important that it does not suffer from ground-loop disturbances and electromagnetic interference (EMI). Introducing a transformer between the sawtooth source and the SQUID is very effective in suppressing disturbances. The sawtooth signal has both slow and fast components, and the frequency can vary between a few kHz up to a MHz, depending on the TES signal and SQUID characteristics. A transformer able to handle such a broad range of conditions must have very stringent characteristics and needs to be custom designed. Our solution exploits standard commercial and inexpensive transformers for LAN networks, stacked in a user-selectable number, to better fit the bandwidth requirements. A model that allows handling of the low- and high-frequency operating range has been developed. Full article

Long-term installation of ultrasonic transducers in high temperature environments allows for continuous monitoring of critical components and processes without the need to halt industrial operations. Transducer designs based on the high-Curie-point piezoelectric material lithium niobate have been shown to both be effective and stable at extreme temperatures for long-term installation. In this study, several brazing techniques are evaluated, all of which aim to provide both mechanical bonding and acoustic coupling directly to a bare lithium niobate piezoelectric element. Two brazing materials—a novel silver-copper braze applied in a reactive air environment and an aluminum-based braze applied in a vacuum environment—are found to be suitable for ultrasound transmission at elevated temperatures. Reliable wide-bandwidth and low-noise ultrasound transmission is achieved between room temperature and 800 °C. Full article

Knowledge of the beam properties in proton therapy through beam monitoring is essential, ensuring an effective dose delivery to the patient. In clinical practice, currently used interceptive ionisation chambers require daily calibration and suffer from a slow response time. A new non-invasive method for dose online monitoring is under development based on the silicon multi-strip sensor LHCb VELO (VErtex LOcator), originally used for the LHCb experiment at CERN. The proposed method relies on proton beam halo measurements. Several changes in the system setup were necessary to operate the VELO module as a standalone system outside of the LHC environment and are described in this paper. A new cooling, venting and positioning system was designed. Several hardware and software changes realised a synchronised readout with a locally constructed Faraday Cup and the RF frequency of a medical cyclotron with quasi-online monitoring. The adapted VELO module will be integrated at the 60 MeV proton therapy beamline at the Clatterbridge Cancer Centre (CCC), UK and the capability as a beam monitor will be assessed by measuring the beam current and by monitoring the beam profile along the beamline in spring 2019. Full article