Drift Tube Research Articles

Development of a readout electronic prototype system for the MWDC at the ETF in HIRFL-CSR

This paper proposes and implements a readout electronic prototype system for a Multi-Wire Drift Chamber (MWDC) detector. This system includes Front-End Electronics (FEE), Sub_Data Acquisition (Sub_DAQ), and Common Data Acquisition Unit (CDAU). Based on a self-developed Application-Specific Integrated Circuit (ASIC) chip, the FEE amplifies and reshapes the detector signals before transmitting them via a high-density micro-coaxial cable to the Sub_DAQ. The Sub_DAQ, based on a Field-Programmable Gate Array (FPGA), was designed to process MWDC signals. The Sub_DAQ can perform an analogue-to-digital conversion, online data processing, and package transmission before transmitting the data to the CDAU via a high-speed optical fibre link. The CDAU gathered data, online processed the data, and then transmitted the data to the computer via the PCIe 3.0 interface. This paper will discuss the design process, the implementation, and the initial test results of the readout electronic prototype system.

Specific moments in detection of superheavy nuclei: DGFRS-2 spectrometer

In this paper, we present the results of the first beam tests of the detection system at the focal plane of the Dubna Gas-Filled Recoil Separator-2 (DGFRS-2), which receives beams from the DC-280 FLNR cyclotron. The high beam intensity of 48Ca+10 heavy ions from the cyclotron enables us to obtain a number of superheavy recoils sufficient to compare both the measured and calculated spectra of superheavy recoils implanted into a silicon detector. A real-time algorithm to search for an Evaporation Residue (ER) — α correlated sequences is described in brief. It should be noted that the DGFRS-2 spectrometer operates in conjunction with the 48 × 128 strip DSSD (Double-sided Silicon Strip Detector; 48 × 226 mm2) detector and a low-pressure pentane-filled gaseous detector (1.2 Torr; 80 × 230 mm2). A block-diagram of the spectrometer and the event format are also presented. Special attention is paid to the response of a low-pressure pentane-filled ΔE multiwire proportional chamber for recoils of Fl, synthesized in the 242Pu + 48Ca → 287Fl + 3n complete fusion nuclear reaction. Some actual parameters of the detection system have also been extracted from natYb + 48Ca, 232Th + 48Ca, 243Am + 48Ca, 238U + 48Ca reactions. The effect of neighbor strip charge sharing for the ohmic side of the DSSD detector is also under consideration.

Physics design, fabrication, RF measurement and beam commissioning of a dual beam drift tube linac

A novel type dual-beam drift tube linac (DB-DTL) prototype was firstly designed to prove the feasibility of the multi-beam type DTL at the institute of modern physics. The physics design, cavity fabrication, low-power RF measurement, RF conditioning and beam commissioning of the DB-DTL cavity were completed and presented in this paper. Operating at 81.25 MHz, the DB-DTL was designed to accelerate 10 mA proton from 0.56 MeV to 2.5 MeV. The field distribution of the DB-DTL cavity were measured at low RF power level and particle tracing using measured field were done, which both agree well with the physics design. The measured Q 0 value and the shunt impedance are 11606 and 172 MΩ/m, respectively. The RF conditioning and the first beam commissioning of the DB-DTL cavity were completed. The beam experiment platform was built at the Lanzhou university due to the academy research cooperation between the institute of modern physics, Sun Yat-sen university and Lanzhou university. Based on the existing experiment condition, 2.5 MeV proton acceleration and measurement were successfully achieved at 42 kW (0.85*Q 0)) RF power of the DB-DTL cavity, which match the physics design very well.

Highly Efficient Ion Manipulator for Tandem Ion Mobility Spectrometry: Exploring a Versatile Technique by a Study of Primary Alcohols

In this work, we present a tandem ion mobility spectrometer (IMS) utilizing a highly efficient ion manipulator allowing to store, manipulate, and analyze ions under high electric field strengths and controlled ion-neutral reactions at ambient conditions. The arrangement of tandem drift regions and an ion manipulator in a single drift tube allows a sequence of mobility selection of precursor ions, followed by storage and analysis, mobility separation, and detection of the resulting product ions. In this article, we present a journey exploring the capabilities of the present instrument by a study of eight different primary alcohols characterized at reduced electric field strengths E/N of up to 120 Td with a water vapor concentration ranging from 40 to 540 ppb. Under these conditions, protonated alcohol monomers up to a carbon number of nine could be dissociated, resulting in 18 different fragmented product ions in total. The fragmentation patterns revealed regularities, which can be used for assignment to the chemical class and improved classification of unknown substances. Furthermore, both the time spent in high electrical field strengths and the reaction time with water vapor can be tuned precisely, allowing the fragment distribution to be influenced. Thus, further information regarding the relations of the product ions can be gathered in a standalone drift tube IMS for the first time.

Cryogenic ion mobility-mass spectrometry for the study of conformations of host-guest complexes

Variable-temperature cryogenic ion mobility-mass spectrometry (VT-Cryo-IM-MS) was developed to examine the conformations of host-guest complexes. The VT-Cryo-IM-MS consists of an electrospray ionization source, a quadrupole ion trap, a cryogenic ion drift tube, and a time-of-flight mass spectrometer. The ion drift tube was cooled to 83 K with liquid nitrogen. Two sets of ion funnels are installed at the source and the drift tube to focus the ion beam. We used Li+-encapsulated fullerene (Li+@C60) as a reference ion to examine the ion-mobility resolution of the VT-Cryo-IM-MS apparatus because this ion has a rigid structure with a single conformer. The temperature dependence of collision cross section (CCS) of Li+@C60 and the resolution of the apparatus were determined at each temperature. We examined the conformations of host-guest complexes of a series of metal ions (M = Ca2+, Na+, Ag+, K+, Rb+, and Cs+) with dibenzo-24-crown-8 (DB24C8) by Cryo-IM-MS. All CCS distributions were fitted with two Gaussian functions which are assigned to closed and open conformers. These closed and open conformers have different distances between the two benzene rings of DB24C8. The abundance ratio of closed conformers for these M(DB24C8) complex ions depends on the guest M ion with an order, Ca2+ < Na+ < Ag+ < Cs+ < Rb+ < K+. The stability of the closed conformer of K+(DB24C8) originates from the benzene ring positional relationship which is quite close to that of the free benzene dimer. This special benzene dimer-like conformation produces the strong π-π interaction between the benzene rings of K+(DB24C8).

Ion-Neutral Collision Cross Section as a Function of the Static Dipole Polarizability and the Ionization Energy of the Ion.

Ion mobility spectrometry is becoming more and more popular as a fast, efficient, and sensitive tool for the separation and identification of ionized molecules in the gas phase. An ion traveling through a drift tube at atmospheric pressure under the influence of an electric field collides with the buffer gas molecules. The mobility of the ion depends inversely on the ion-neutral collision cross section. In the simplest hard-sphere approximation, the collision cross section is the area of the conventional geometric cross section. However, deviations are expected because of the physical interactions between the colliding species. More than a century ago, Langevin described a model for the interaction between a point-charge ion and a polarizable atom (molecule). Since then, the model has been modified many times to include better approximations of the interaction potential, usually preserving the point-charge nature of the ion. Although more advanced approaches allow for considering polarizable ions with dissimilar sizes and shapes, still explicit analytical dependencies on the properties of the ion remain elusive. In this work, an extended version of the Langevin model is proposed and solved using algebraic perturbation theory. A simple analytical expression of the collision cross section depending explicitly on both the static dipole polarizability and the ionization energy of the ion is found. The equation is validated using ion mobility data. Surprisingly, even low-level calculations of the polarizability tensors produce results that are consistent with the experimental observations. This fact makes the equation very attractive for helping applications in different areas, such as the deconvolution of mobilograms of protomers, ion-molecule chemical kinetics, and others.

Measurement of the Cross Section for the Neutron-Induced Fission of 238U Nuclei in the Energy Range of 0.3–500 MeV

The cross section for the neutron-induced fission of 238U nuclei has been measured using the time-of-flight spectrometer of the GNEIS neutron complex at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute, in the neutron energy range of 0.3–500 MeV. Fission fragments have been detected by low-pressure position-sensitive multiwire proportional counters. The cross section for 238U(n, f) fission has been measured with respect to the cross section for 235U(n, f) fission, which is an accepted international standard. Data on the energy dependence of the anisotropy of the angular distribution of fragments of neutron-induced 238U nuclei are also presented. The data obtained have been compared to previous experiments carried out using both similar and significantly different methods.

The light charged particle detector array at the CSNS Back-n white neutron source

The Back-n white neutron source at the China Spallation Neutron Source (CSNS) provides neutrons in the continuous energy region from 0.5 eV to 200 MeV. A spectrometer named Light charged Particle Detector Array (LPDA) is designed for the study of (n, lcp) reactions at Back-n. The main detector of the LPDA spectrometer, a 16-unit ΔE-ΔE-E telescope array, is composed of two arrays of 8-unit ΔE-ΔE-E telescope. Each telescope unit consists of a Low-Pressure Multi-Wire Proportional Chamber (LPMWPC), a Si-PIN detector, and a CsI(Tl) scintillator detector. In 2021, a neutron-proton (n-p) scattering reaction cross-section measurement experiment was accomplished as the first experiment of the telescope array. Protons can be clearly identified in the ΔE-E spectrum (LPMWPC + Si-PIN) and the ΔE-E spectrum (Si-PIN + CsI(Tl)). Cross sections of the n-p scattering reaction in the neutron energy range of several MeV are extracted. The ΔE-E method also provides new measurement opportunities for many-body neutron induced light charged-particle emission reactions.

Effect of geometric parameters of two-section axisymmetric overdimensional relativistic diffraction generators on their output characteristics

The effect of variation the length of drift tube of two-section structure of axisymmetric relativistic diffraction generator on its output power operation and sustainability of generation is considered. A comparison is made of the electromagnetic field strength distribution for structures with two types of discontinuity: sinusoidal corrugation and half-torus on pedestal.

Detecting Hexafluoroisopropanol Using Soft Chemical Ionization Mass Spectrometry and Analytical Applications to Exhaled Breath

Here we explore the potential use of proton transfer reaction/selective reagent ion-time-of-flight-mass spectrometry (PTR/SRI-ToF-MS) to monitor hexafluoroisopropanol (HFIP) in breath. Investigations of the reagent ions H3O+, NO+, and O2+• are reported using dry (relative humidity (rH) ≈ 0%) and humid (rH ≈ 100%)) nitrogen gas containing traces of HFIP, i.e., divorced from the complex chemical environment of exhaled breath. HFIP shows no observable reaction with H3O+ and NO+, but it does react efficiently with O2+• via dissociative charge transfer resulting in CHF2+, CF3+, C2HF2O+, and C2H2F3O+. A minor competing hydride abstraction channel results in C3HF6O+ + HO2• and, following an elimination of HF, C3F5O+. There are two issues associated with the use of the three dominant product ions of HFIP, CHF2+, CF3+, and C2H2F3O+, to monitor it in breath. One is that CHF2+ and CF3+ also result from the reaction of O2+• with the more abundant sevoflurane. The second is the facile reaction of these product ions with water, which reduces analytical sensitivity to detect HFIP in humid breath. To overcome the first issue, C2H2F3O+ is the ion marker for HFIP. The second issue is surmounted by using a Nafion tube to reduce the breath sample's humidity prior to its introduction into drift tube. The success of this approach is illustrated by comparing the product ion signals either in dry or humid nitrogen gas flows and with or without the use of the Nafion tube, and practically from the analysis of a postoperative exhaled breath sample from a patient volunteer.

Shell effect driven fission modes in fragment mass and total kinetic energy distribution of Hg*192

Background: Asymmetric fission in sublead nuclei, especially mercury and platinum isotopes, has generated keen interest in studying fission in $A&lt;200$ mass region. The role of proton and neutron shells on asymmetric fission in these nuclei is still under test and requires more investigation.Purpose: This paper presents measurements aimed at studying the fission modes of $^{192}\mathrm{Hg}$ formed in the reaction $^{32}\mathrm{S}+^{160}\mathrm{Gd}$ in the excitation energy range 54--74 MeV.Method: Mass distributions have been determined from the fission fragments' (FF) time of flight (TOF). Two multiwire proportional chambers were placed symmetrically on opposite sides of the beam to cover the folding angle for symmetric fission. The measured TOF of the fission fragments was used to obtain their velocities, and after clean separation of compound nuclear fission events, the velocities were further used to obtain the fission fragment mass and total kinetic energy (TKE) distribution.Results: The fission fragment mass distributions at all beam energies were found to be characteristically flat topped, which deviates significantly from a single Gaussian behavior. The distinctive features of mass and energy distributions happen to be explained by the presence of a symmetric fission mode and three asymmetric fission modes, manifested by different total kinetic energies in varying mass regions. These asymmetric fission modes are a consequence of the stabilization role of proton shells at $Z\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}$ 36, $Z\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}$ 46, and $Z$ = 28/50. The most probable mass of light and heavy fragments are found to be around 86 and 106 u, respectively. The symmetric yield is found to increase with the excitation energy.Conclusions: The present study indicates a mixture of symmetric and asymmetric modes in the fission of $^{192}\mathrm{Hg}$ nuclei and points out the relevance of deformed proton shells at $Z\phantom{\rule{4pt}{0ex}}\ensuremath{\approx}$ 36 and 46.

A Comparison of the Performance of Modular Standalone Do-It-Yourself Ion Mobility Spectrometry Systems.

As the spectrum of ion mobility spectrometry (IMS) applications expands and more experimental configurations are developed, identifying the correct platform for an experimental campaign becomes more challenging for researchers. Additionally, metrics that compare performance (Rp, for example) often have nuanced differences in definition between platforms that render direct comparisons difficult. Here we present a comparison of three do-it-yourself (DIY) drift tubes that are relatively low cost and easy to construct, where the performance of each is evaluated based on three different metrics: resolving power, the ideality of resolving powers, and accuracy/precision of K0 values. The standard PCBIMS design developed by Reinecke and Clowers (Reinecke, T.; Clowers, B. H. HardwareX 2018, 4, e00030) provided the highest resolving power (>90) and the highest ideality of resolving power ratios (>90% at best) of the three systems. However, the flexible tube (FlexIMS) construction as described by Smith et al. (Smith, B. L. Anal. Chem. 2020, 92 (13), 9104-9112) exhibited the highest degree of precision of K0 values (relative standard deviation of <0.42%). Depending on the application, the drift tube variants presented and evaluated here offer a low-cost alternative to commercial drift-tube systems with levels of performance that approach theoretical maxima.

Track-based alignment for the BESIII CGEM detector in the cosmic-ray test

The Beijing Electron Spectrometer III (BESIII) is a multipurpose detector operating on the Beijing Electron Positron Collider II (BEPCII). After more than ten years operation, the efficiency of the inner layers of the Main Drift Chamber (MDC) decreased significantly. To solve this issue, the BESIII collaboration is planning to replace the inner part of the MDC with three layers of Cylindrical triple Gas Electron Multipliers (CGEM).The transverse plane spatial resolution of CGEM is required to be 120μm or better. To meet this goal, a careful calibration of the detector is necessary to fully exploit the potential of the CGEM detector. In all the calibrations, the detector alignment plays an important role to improve the detector precision. The track-based alignment for the CGEM detector with the Millepede algorithm is implemented to reduce the uncertainties of the hit position measurement. Using the cosmic-ray data taken in 2020 with the two layers setup, the displacement and rotation of the outer layer with respect to the inner layer is determined by a simultaneous fit applied to more than 160000 tracks. A good alignment precision has been achieved that guarantees the design request could be satisfied in the future. A further alignment is going to be performed using the combined information of tracks from cosmic-ray and collisions after the CGEM is installed into the BESIII detector.

Evaluation of IMS drift tube temperature on the peak shape of high boiling fragrance compounds towards allergen detection in complex cosmetic products and essential oils

Gas chromatography-ion mobility spectrometry (GC-IMS) has recently gained increasing attention for the analysis of volatile compounds due to its high sensitivity, selectivity, and robust design. Peak shape distortion, including peak tailing or broadening, are well known challenges in chromatographic analysis that result in peak asymmetry and decreased resolution. However, in IMS analysis peak tailing, which is independent on the column separation technique, have also been observed. As high boiling substances, such as monoterpenes, are mainly affected by enlarged peak tailing in GC-IMS, we propose that condensation or adsorption effects within the “cold” IMS cell, which is commonly operated at 45 °C–90 °C, are the root cause. To avoid condensation and to decrease peak tailing, we used a prototypic high temperature ion mobility spectrometry (HTIMS) in this work, which allows an increase of the IMS drift tube temperature up to 180 °C. This HTIMS was coupled to a GC column separation and used to analyse the peak shape of homologues series of ketones, alcohols, aldehydes, as well as high boiling fragrance compounds, such as monoterpenes and phenylpropanoids. While we were able to show that an increased IMS drift tube temperatures correlates well with improved peak shapes, the GC parameters of the HS-GC-HTIMS method, however, were found to have little effect on the peak shapes in IMS spectra. In particular monoterpenes, which display intense peak tailing at lower IMS drift tube temperatures, show significant improvement of the peak shape at higher IMS drift tube temperatures. This leads to the assumption that high boiling substances indeed undergo condensation effects within the IMS cell at low drift tube temperatures. For many separation tasks, such as the separation of the phenylpropanoids eugenol and isoeugenol, comparably low IMS temperatures of 120 °C are already sufficient to achieve a resolution above 1.5. However, the optimal drift tube temperature is dependent on the substance class. While the aspect ratio increases steadily for most monoterpenes, phenylpropanoids and aldehyde monomer peaks investigated, an optimal aspect ratio was found for ketones between 140 °C and 160 °C and alcohols between 120 °C and 140 °C. Lastly, the change of the reduced mobility K0 with the increase of drift tube temperature was analysed. Compounds with similar chemical structure, such as the alcoholic monoterpenes citronellol and geraniol or the phenylpropanoids eugenol and isoeugenol show similar shifts of the K0 value. Substances which differ in their chemical structure, such as the aldehyde monoterpenes citral and cinnamal have substantially different shifts of the K0 value. With a future large substance database, the temperature dependant slope of the K0 value of a substance could be used to identify the substance groups of unknown molecules. Furthermore, substances with the same drift time but different chemical composition could be separable through a change in drift tube temperature.

Metabolic signature of HepaRG cells exposed to ethanol and tumor necrosis factor alpha to study alcoholic steatohepatitis by LC-MS-based untargeted metabolomics.

Despite the high prevalence of alcoholic liver disease, its identification and characterization remain poor, especially in early stages such as alcoholic fatty liver disease and alcoholic steatohepatitis. This latter implies diagnostic difficulties, few therapeutic options and unclear mechanisms of action. To elucidate the metabolic alterations and pinpoint affected biochemical pathways, alcoholic steatohepatitis was simulated in vitro by exposing HepaRG cells to ethanol (IC10, 368mM) and tumor necrosis factor alpha (TNF-α, 50ng/mL) for 24h. This combined exposure was compared to solely ethanol-exposed as well as -nonexposed cells. Four different metabolomics platforms were used combining liquid chromatography, high-resolution mass spectrometry and drift tube ion mobility to elucidate both intracellular and extracellular metabolic alterations. Some of the key findings include the influence of TNF-α in the upregulation of hepatic triglycerides and the downregulation of hepatic phosphatidylethanolamines and phosphatidylcholines. S-Adenosylmethionine showed to play a central role in the progression of alcoholic steatohepatitis. In addition, fatty acyl esters of hydroxy fatty acid (FAHFA)-containing triglycerides were detected for the first time in human hepatocytes and their alterations showed a potentially important role during the progression of alcoholic steatohepatitis. Ethoxylated phosphorylcholine was identified as a potential new biomarker of ethanol exposure.

Breath-by-breath measurement of exhaled ammonia by acetone-modifier positive photoionization ion mobility spectrometry via online dilution and purging sampling

Exhaled ammonia (NH3) is an essential noninvasive biomarker for disease diagnosis. In this study, an acetone-modifier positive photoionization ion mobility spectrometry (AM-PIMS) method was developed for accurate qualitative and quantitative analysis of exhaled NH3 with high selectivity and sensitivity. Acetone was introduced into the drift tube along with the drift gas as a modifier, and the characteristic NH3 product ion peak of (C3H6O)4NH4+ (K0 = 1.45 cm2/V·s) was obtained through the ion-molecule reaction with acetone reactant ions (C3H6O)2H+ (K0 = 1.87 cm2/V·s), which significantly increased the peak-to-peak resolution and improved the accuracy of exhaled NH3 qualitative identification. Moreover, the interference of high humidity and the memory effect of NH3 molecules were significantly reduced via online dilution and purging sampling, thus realizing breath-by-breath measurement. As a result, a wide quantitative range of 5.87–140.92 μmol/L with a response time of 40 ms was achieved, and the exhaled NH3 profile could be synchronized with the concentration curve of exhaled CO2. Finally, the analytical capacity of AM-PIMS was demonstrated by measuring the exhaled NH3 of healthy subjects, demonstrating its great potential for clinical disease diagnosis.

A high deposition efficiency method for wire arc additive manufacturing

In this study, single wire arc additive manufacturing (SWAAM) and multi wire arc additive manufacturing (MWAAM) were used to fabricate the TC11 alloy. Microstructure and mechanical properties of TC11 alloy were studied. The results showed that the microstructure of MWAAM TC11 alloy composed of α and β phase, and the proportion of β phase increased slightly than that of SWAAM TC11 sample. Compared with the SWAAM TC11 sample, the microhardness of MWAAM TC11 alloy sample increased from 382 to 407 HV, and average ultimate tensile strength of MWAAM TC11 alloy sample increased from 922.01 to 934.56 MPa. The results indicate that the addition of wires can significantly improve both manufacturing efficiency and mechanical properties of TC11 alloy components.

Charged particle reconstruction in CLAS12 using Machine Learning

In this work, we present studies of track parameter reconstruction from raw information in CLAS12 detector's Drift Chambers, using Machine Learning (ML). We study the resolution of tracks reconstructed with different types of ML models/algorithms, including Multi-Layer Perceptron (MLP), Extremely Randomized Trees (ERT) and Gradient Boosting Trees (GBT) using simulated data. The resulting ML model is capable of reconstructing track parameters (particle momentum, and polar and azimuthal angles) with accuracy similar to Hit Based (HB) tracking code, but 150 times faster. Moreover, physics reactions can be identified using the particles reconstructed by the neural network in real-time (with a rate of about 34kHz) during experimental data collection. The developed model can be used in numerous applications, such as triggering specific physics reactions in real-time, detector performance monitoring, and real-time detector calibration.

Molecular and Structural Characterization of Isomeric Compounds in Atmospheric Organic Aerosol Using Ion Mobility-Mass Spectrometry.

Secondary organic aerosol (SOA) formed through multiphase atmospheric chemistry makes up a large fraction of airborne particles. The chemical composition and molecular structures of SOA constituents vary between different emission sources and aging processes in the atmosphere, which complicates their identification. In this work, we employ drift tube ion mobility spectrometry with quadrupole time-of-flight mass spectrometry (IM-MS) detection for rapid gas-phase separation and multidimensional characterization of isomers in two biogenic SOAs produced from ozonolysis of isomeric monoterpenes, d-limonene (LSOA) and α-pinene (PSOA). SOA samples were ionized using electrospray ionization (ESI) and characterized using IM-MS in both positive and negative ionization modes. The IM-derived collision cross sections in nitrogen gas (DTCCSN2 ) for individual SOA components were obtained using multifield and single-field measurements. A novel application of IM multiplexing/high-resolution demultiplexing methodology was employed to increase sensitivity, improve peak shapes, and augment mobility baseline resolution, which revealed several isomeric structures for the measured ions. For LSOA and PSOA samples, we report significant structural differences of the isomer structures. Molecular structural calculations using density functional theory combined with the theoretical modeling of CCS values provide insights into the structural differences between LSOA and PSOA constituents. The average DTCCSN2 values for monomeric SOA components observed as [M + Na]+ ions are 3-6% higher than those of their [M - H]- counterparts. Meanwhile, dimeric and trimeric isomer components in both samples showed an inverse trend with the relevant values of [M - H]- ions being 3-7% higher than their [M + Na]+ counterparts, respectively. The results indicate that the structures of Na+-coordinated oligomeric ions are more compact than those of the corresponding deprotonated species. The coordination with Na+ occurs on the oxygen atoms of the carbonyl groups leading to a compact configuration. Meanwhile, deprotonated molecules have higher DTCCSN2 values due to their elongated structures in the gas phase. Therefore, DTCCSN2 values of isomers in SOA mixtures depend strongly on the mode of ionization in ESI. Additionally, PSOA monomers and dimers exhibit larger DTCCSN2 values (1-4%) than their LSOA counterparts owing to more rigid structures. A cyclobutane ring is present with functional groups pointing in opposite directions in PSOA compounds, as compared to noncyclic flexible LSOA structures, forming more compact ions in the gas phase. Lastly, we investigated the effects of direct photolysis on the chemical transformations of selected individual PSOA components. We use IM-MS to reveal structural changes associated with aerosol aging by photolysis. This study illustrates the detailed molecular and structural descriptors for the detection and annotation of structural isomers in complex SOA mixtures.

A Beam Monitor for Ion Beam Therapy Based on HV-CMOS Pixel Detectors

Particle therapy is a well established clinical treatment of tumors. More than one hundred particle therapy centers are in operation world-wide. The advantage of using hadrons like protons or carbon ions as particles for tumor irradiation is the distinct peak in the depth-dependent energy deposition, which can be exploited to accurately deposit doses in the tumor cells. To guarantee this, high accuracy in monitoring and control of the particle beam is of the utmost importance. Before the particle beam enters the patient, it traverses a monitoring system which has to give fast feedback to the beam control system on position and dose rate of the beam while minimally interacting with the beam. The multi-wire chambers mostly used as beam position monitors have their limitations when a fast response time is required (drift time). Future developments such as MRI-guided ion beam therapy pose additional challenges for the beam monitoring system, such as tolerance of magnetic fields and acoustic noise (vibrations). Solid-state detectors promise to overcome these limitations and the higher resolution they offer can create additional benefits. This article presents the evaluation of an HV-CMOS detector for beam monitoring, provides results from feasibility studies in a therapeutic beam, and summarizes the concepts towards the final large-scale assembly and readout system.