Drift Tube Research Articles

FPGA-based fast track reconstruction for the conceptual design of STCF MDC trigger

The Super Tau-Charm Facility (STCF) is a future high luminosity electron-positron collider proposed in China, with a peak luminosity greater than 0.5× 1035 cm2s-1 at center-of-mass energy of 4.0 GeV. The main drift chamber (MDC) is designed as the central tracker, which provides the charged particle information for the level-1 trigger. This paper presents an FPGA-based fast trigger algorithm with the function of finding the charged particle tracks and reconstructing their transverse momentum and azimuthal angle. It adopts a two-stage lookup-table-based pattern matching architecture. The prototype trigger logic was implemented in a Xilinx XCKU060 FPGA. Test results with simulated data suggest that the trigger efficiency of J/Ψ events is better than 96%, and the resolution in the reconstructed track's azimuthal angle at the interaction point is better than 12 mrad. The overall dead time is 24 ns and the total latency is 339 ns. All these performances meet the requirements of the MDC trigger in the current conceptual design stage of STCF project.

An Efficient Vircator With High Output Power and Less Drifting Electron Loss by Forming Multivirtual Cathodes

Multi virtual cathodes (MVCs) were created in an axial vircator utilizing two dielectric reflectors (DRs). The wall charge of drifting electrons on the surface of DRs led to the creation of VC2 and VC3 in the downstream area of drift tube, according to phase space simulations. The microwave generated by VC1 interacted with the charge of VC2 and VC3 to raise the power amplitude, resulting in an increase in output power from 284 MW to 1028 MW. The use of two dielectric reflectors was proven to have a remarkable impact in reducing electron loss, increasing output power, and improving efficiency. The suggested vircator’s efficiency with MVCs improved from 7.9 % to 28.6 %. The findings indicate important signs of progress in vircator research to decrease electron losses and boost beam–wave interaction, which might lead to the advancement of high-efficiency vircators.

Construction and testing of sMDT tubes at the University of Michigan for the ATLAS Muon Spectrometer upgrade

This paper reports on the design and construction of infrastructure and test stations for small-diameter monitored drift tube (sMDT) assembly and testing at the University of Michigan (UM) to prepare for the ATLAS Muon Spectrometer upgrade for the high-luminosity program of the Large Hadron Collider. Procedures of the tube assembly and quality assurance and control (QA/QC) tests are described in detail. More than 99% of the tubes meet the tube QA/QC specifications based on 2100 tubes built at UM. The UM test stations are also used for QA/QC testing on the tubes constructed at Michigan State University. These tubes are being used to construct the sMDT chambers which will replace the current MDT chambers of the barrel inner station of the Muon Spectrometer.

Wire Tension Test Bench for Wire Chambers

Wire Tension Test Bench for Wire Chambers

Increased Sensitivity in Proton Transfer Reaction Mass Spectrometry by Using a Novel Focusing Quadrupole Ion Funnel.

Sensitivity enhancement in proton transfer reaction mass spectrometry (PTR-MS) is an important development direction. We developed a novel drift tube called a focusing quadrupole ion funnel (FQ-IF) for use in PTR-MS to improve the sensitivity. The FQ-IF consists of 20 layers of stainless steel electrodes, and each layer has 4 quarter rings. The first 6 layers have a constant inner hole diameter of 22 mm; the latter 14 layers taper the inner diameter down to 8 mm. The FQ-IF drift tube can also operate in the direct current (DC) mode (similar to a conventional drift tube) and ion funnel (IF) mode (similar to a conventional ion funnel drift tube) by changing the voltage loading method. The simulation results show that the transmission efficiency of the FQ-IF is significantly improved compared to that of the other two modes. Further experiments show that the product ions of limonene tend to convert into smaller m/z fragment ions at higher voltages for the DC and IF modes. However, unlike the DC and IF modes, the distribution of product ions is stable at higher voltages for the FQ-IF. In other words, a higher RF voltage for the FQ-IF will not increase the collision energy of ions. In addition, the improvements in sensitivity for the FQ-IF range from 13.8 to 87.9 times compared to the DC mode and from 1.7 to 4.8 times compared to the IF mode for the 12 test compounds. The improvements in the limit of detection (LOD) for the FQ-IF range from 2.7 to 35.7 times compared to the DC mode. The FQ-IF provides a valuable reference for improving the sensitivity of PTR-MS and other mass spectrometers.

A High-Throughput Ion Mobility Spectrometry-Mass Spectrometry Screening Method for Opioid Profiling.

In 2017, the United States Department of Health and Human Services declared the widespread misuse and abuse of prescription and illicit opioids an epidemic. However, this epidemic dates back to the 1990s when opioids were extensively prescribed for pain management. Currently, opioids are still recommended for pain management, and given their abuse potential, rapid screening is imperative for patient treatment. Of particular importance is assessing pain management patient compliance, where evaluating drug use is crucial for preventing opioid abuse and potential overdoses. In this work, we utilized drift tube ion mobility spectrometry coupled with mass spectrometry (DTIMS-MS) to develop a rapid screening method for 33 target opioids and opioid urinary metabolites. Collision cross section values were determined for all target molecules using a flow-injection DTIMS-MS method, and clear differentiation of 27 out of the 33 opioids without prior chromatographic separation was observed when utilizing a high resolution demultiplexing screening approach. An automated solid phase extraction (SPE) platform was then coupled to DTIMS-MS for 10 s sample-to-sample analyses. This SPE-IMS-MS approach enabled the rapid screening of urine samples for opioids and presents a major improvement in sample throughput compared to traditional chromatographic analyses coupled with MS, which routinely take several minutes per sample. Overall, this vast reduction in analysis time facilitates a faster turn-around for patient samples, providing great benefits to clinical applications.

Simulation study of inverse diffusion counterbalance method for super-resolution ion mobility spectrometry.

Ion mobility spectrometer (IMS) is a powerful chemical composition analysis tool working at atmospheric pressure that can be used to separate complex samples and study molecular structures. Resolution is a key parameter for evaluating the performance of IMS. However, for the pulsed sampling technique used by drift tube IMS, there is an upper limit to the resolution due to the diffusion between ions and the drift gas. In this work, an inverse diffusion counterbalance method is proposed to break the resolution limit. The method is inspired by the stimulated emission depletion (STED). In optical microscopy systems, STED is used to break the optical diffraction limit by a ring of depleted light to counteract diffraction effects of the excited light. We modified this strategy and applied it to an IMS system for counteracting the diffusion effect of the pulsed ion packet. The method can increase the resolution up to 1.55 times through theoretical analysis, and the improvement is verified by simulations. The simulation results find that the initial width of the ion packet has an influence on the effectiveness of the method, and the narrower the initial width, the better the effect. The proposed inverse counterbalance strategy may also be applied to other spectral analysis instruments to break the resolution limit.

Finite element analysis of beam optics, high voltage ceramic seal and focusing magnet for CEPC C-band 80 MW klystron

For CEPC LINAC, the first 80 MW class klystron at C-band (5720 MHz) has been proposed to accelerate a high-current beam at an acceleration gradient of 45 MV/m. This paper discusses the design and simulation of beam optics, beam envelope, drift tube, and solenoid of the klystron. Space charge beam current of 390 A at an acceleration potential of 410 kV is obtained with average cathode loading of less than 6.0 A/cm2. The maximum surface electric field at the beam optics and high voltage ceramic seal have been evaluated less than 22 kV/mm and 4.50 kV/mm, respectively. The electron beam with an average beam radius of 5.40 mm has successfully been transported to the interaction cavity with beam ripple rate around 4.0% with low scalloping factor and a fill factor of 0.670. 2-D, DGUN & POISSON simulations results are validated by the 3-D CST simulation and found in agreement.

Clinical Application of Peritoneal Dialysis Catheterization without Capsular Puncture Technique.

Objective To summarize the advantages of peritoneal dialysis (PD) catheters without capsular puncture (only one pneumoperitoneum needle) puncture technique conducted by our center. Methods The study examines the clinical data of PD patients (including the general situation of patients, intraoperative and postoperative characteristics, and complications) undergoing pneumoperitoneum needle catheterization from January 2019 to May 2021 in the Department of Nephrology at the First Affiliated Hospital of Hebei North University (the largest peritoneal dialysis center in Zhangjiakou). Results A total of 153 surgical cases were collected. There were 91 males and 62 females. The mean (± standard deviation) age was 56.1 ± 18.6 years, and the mean (± standard deviation) follow-up time was 16.7 ± 8.2 months. The average operation time was 30.33 minutes with a standard deviation of 14.80 minutes. The length of abdominal incision is 2.38 ± 0.42 cm, and the blood loss was about 26.3 ± 9.2 ml, including 2 cases of laparoscopic reposition of drift tube, 0 case of pipe blockage, 3 cases of fluid leakage, 1 case of peritoneal dialysis catheter tunnel infection, 4 cases of outlet infection, 12 occurrences of peritonitis, 121.3 patient months in peritonitis, and 0 times in omentum wrapping without bladder injury, incisional hernia, or intestinal injury. Conclusion Relative to open operation, the peritoneal dialysis (PD) catheters with pneumoperitoneum needle puncture technique has the following advantages: simpler operation, shorter operation time, less bleeding, less injury, less complications, and higher safety. Moreover, there are no additional costs compared with open operation. Thus, the technique is recommended for clinical applications.

Disentangling Electronic Spectra of Linear and Cyclic Hydrogenated Carbon Cluster Cations, C2n+1H+ (n = 3-10).

Electronic spectra are measured for protonated carbon clusters (C2n+1H+) containing between 7 and 21 carbon atoms. Linear and cyclic C2n+1H+ isomers are separated and selected using a drift tube ion mobility stage before being mass selected and introduced into a cryogenically cooled ion trap. Spectra are measured using a two-color resonance-enhanced photodissociation strategy, monitoring C2n+1+ photofragments (H atom loss channel) as a function of excitation wavelength. The linear C7H+, C9H+, C11H+, C13H+, C15H+, and C17H+ clusters, which are predicted to have polyynic structures, possess sharp 11Σ+ ← X̃1Σ+ transitions with well-resolved vibronic progressions in C-C stretch vibrational modes. The vibronic features are reproduced by spectral simulations based on vibrational frequencies and geometries calculated with time-dependent density functional theory (ωB97X-D/cc-pVDZ level). The cyclic C15H+, C17H+, C19H+, and C21H+ clusters exhibit weak, broad transitions at a shorter wavelength compared to their linear counterparts. Wavelengths for the origin transitions of both linear and cyclic isomers shift linearly with the number of constituent carbon atoms, indicating that in both cases, the clusters possess a common structural motif.

Control of virtual cathode dynamics under collective acceleration of protons in a Luce diode

The dynamics of propagation of the virtual cathode (VC) during the collective acceleration of protons in the Luce diode has been measured by observing prompt signals of electron currents emitted by the VC with a series of five collimated sensors set normally along the diode axis, as well as by recording signals of Bremsstrahlung and γ-rays generated in a B4C target placed at 25 cm distance from the anode. It has been found that the VC, after the acceleration phase to the optimal distance of about 12 cm, further propagates in the direction of the target with a nearly constant velocity. It has been shown that the generation of the high-energy γ-rays in the target corresponds to the moment the VC arrives at the target position, which indicates the acceleration of protons by the VC and the synchronism of their joint motion. It has been proposed that the acceleration of the VC towards the target is mainly due to the ionization of the residual atmosphere of the drift chamber by the accelerated protons. The ionization efficiency decreases with an increase in the energy of the accelerated protons, which ultimately limits the possibility of their further acceleration.

Revealing the differences in collision cross section values of small organic molecules acquired by different instrumental designs and prediction models

The number of open access databases containing experimental and predicted collision cross section (CCS) values is rising and leads to their increased use for compound identification. However, the reproducibility of reference values with different instrumental designs and the comparison between predicted and experimental CCS values is still under evaluation.This study compared experimental CCS values of 56 small molecules (Contaminants of Emerging Concern) acquired by both drift tube (DT) and travelling wave (TW) ion mobility mass spectrometry (IM-MS). The TWIM-MS included two instrumental designs (Synapt G2 and VION). The experimental TWCCSN2 values obtained by the TWIM-MS systems showed absolute percent errors (APEs) < 2% in comparison to experimental DTIMS data, indicating a good correlation between the datasets. Furthermore, TWCCSN2 values of [M − H]- ions presented the lowest APEs. An influence of the compound class on APEs was observed.The applicability of prediction models based on artificial neural networks (ANN) and multivariate adaptive regression splines (MARS), both built using TWIM-MS data, was investigated for the first time for the prediction of DTCCSN2 values. For [M+H]+ and [M − H]- ions, the 95th percentile confidence intervals of observed APEs were comparable to values reported for both models indicating a good applicability for DTIMS predictions.For the prediction of DTCCSN2 values of [M+Na]+ ions, the MARS based model provided the best results with 73.9% of the ions showing APEs below the threshold reported for [M+Na]+. Finally, recommendations for database transfer and applications of prediction models for future DTIMS studies are made.

Background in the CMS drift tubes: measurements with LHC collision data and implications for detector longevity at HL-LHC

Drift Tubes (DT) are installed in the barrel region of the CMS muon spectrometer. They are used for offline tracking of muons and provide standalone trigger capabilities. Though an upgrade of the DT system electronics is foreseen for the High Luminosity LHC (HL-LHC), the present DT chambers will not be replaced, hence they will be called to operate enduring integrated doses far beyond what they were initially designed for. Together with accelerated aging studies, accurate measurements of the background-induced hit rates and currents observed over Run-2 are critical to assess the longevity of the DT chambers and to make projections of the expected performance of the system throughout HL-LHC. This report presents the state of the art of the studies on the background affecting the DT system, and connects them to results from longevity studies performed at the CERN high-intensity gamma irradiation facility (GIF++). Moreover, it describes all measures that have been put in place, by the end of Run-2 and over LS2, to mitigate aging and, where possible, reduce background level, with the aim of maximizing the performance of the DT muon detector throughout HL-LHC.

Comparability of Steroid Collision Cross Sections Using Three Different IM-HRMS Technologies: An Interplatform Study

Steroids play key roles in various biological processes and are characterized by many isomeric variants, which makes their unambiguous identification challenging. Ion mobility-mass spectrometry (IM-MS) has been proposed as a suitable platform for this application, particularly using collision cross section (CCS) databases obtained from different commercial IM-MS instruments. CCS is seen as an ideal additional identification parameter for steroids as long-term repeatability and interlaboratory reproducibility of this measurand are excellent and matrix effects are negligible. While excellent results were demonstrated for individual IM-MS technologies, a systematic comparison of CCS derived from all major commercial IM-MS technologies has not been performed. To address this gap, a comprehensive interlaboratory comparison of 142 CCS values derived from drift tube (DTIM-MS), traveling wave (TWIM-MS), and trapped ion mobility (TIM-MS) platforms using a set of 87 steroids was undertaken. Besides delivering three instrument-specific CCS databases, systematic comparisons revealed excellent interlaboratory performance for 95% of the ions with CCS biases within ±1% for TIM-MS and within ±2% for TWIM-MS with respect to DTIM-MS values. However, a small fraction of ions (<1.5%) showed larger biases of up to 7% indicating that differences in the ion conformation sampled on different instrument types need to be further investigated. Systematic differences between CCS derived from different IM-MS analyzers and implications on the applicability for nontargeted analysis are critically discussed. To the best of our knowledge, this is the most comprehensive interlaboratory study comparing CCS from three different IM-MS technologies for analysis of steroids and small molecules in general.

A novel L-band metamaterial slow wave structure with low space charge effect and high field uniformity

A novel L-band metamaterial slow wave structure with a weak space charge effect and high field uniformity is proposed. The slow wave structure is composed of two identical all-metal resonant elements. In order to weaken the space charge effect, a long drift tube is adopted as a metal joint, connecting the front periodic unit with the rear one. Moreover, the novel metamaterial structure exhibits higher field uniformity by rotating one of the resonant elements 45° relative to the other. Electromagnetic calculation indicates that the average fluctuation in the electric field dropped from 3% to 0.5%. Based on the novel metamaterial slow wave structure, an L-band Cerenkov oscillator model is built, and a preliminary particle-in-cell simulation is carried out. Under the condition of an acceleration voltage of 500 kV, beam current of 8 kA, and magnetic field of 1 T, a 1.64 GW average output microwave power at 1.30 GHz is obtained. The corresponding conversion efficiency is 41%. The simulation results prove the advantages of the metamaterial Cerenkov oscillator, such as low magnetic field, low impedance, miniaturization, and high conversion efficiency.

Gas electron tracking detector for beta decay experiments

For identification and 3D-tracking of low-energy electrons a new type of gas-based detector was designed that minimizes scattering and energy loss. The current version of the detector is a combination of a plastic scintillator, serving as a trigger source and energy detector, and a hexagonally structured multi-wire drift chamber (MWDC), filled with a mixture of helium and isobutane gas. The drift time information is used to track particles in the plane perpendicular to the wires, while a charge division technique provides spatial information along the wires. The gas tracker was successfully used in the miniBETA project as a beta spectrometer for a measurement of the weak magnetism form factor in nuclear beta decay. The precision of the three-dimensional electron tracking, in combination with low-mass, low-Z materials and identification of backscattering from scintillator, facilitated a reduction of the main systematics effects. The results originate from performance studies with cosmic muons and low-energy electrons (<2 MeV) conducted for several pressures (300–700 mbar) and isobutane content in the gas mixture (10–50%). At certain conditions, a spatial resolution better than 0.5 mm was obtained in the plane perpendicular to the wires, while resolutions of about 6 mm were achieved along wires. Thanks to precise tracking information, it is possible to eliminate electrons and other particles not originating from the desired decay with high efficiency. Additionally, using the coincidence between MWDC and scintillator, background from gamma emission typically accompanying radioactive decays, was highly suppressed. An overview of different event topologies is presented together with the tracker’s ability to correctly recognize them. The analysis is supported by Monte Carlo simulations using Geant4 and Garfield++ packages. Finally, the preliminary results from the 114In spectrum study are presented.

Elimination of self-oscillation between three cascaded reflectors in an X-band triaxial klystron amplifier

Self-oscillation of three cascaded reflectors easily occurs in a triaxial klystron amplifier (TKA) since the TEM mode leakage cannot be cut off by a coaxial waveguide. To solve this issue, we propose a non-uniform reflector to obtain an optimal external quality factor, which indicates its minimum TEM mode leakage. The self-oscillation of three non-uniform reflectors is then suppressed by selecting a specific drift tube length between them. Moreover, different eigenfrequencies are chosen for the three improved reflectors to enhance the tolerance of the drift tube length between them. With these methods, the self-oscillation of three cascaded reflectors can be successfully eliminated, and a TKA with high output efficiency is capable of achieving a long pulse output.

A compact coaxial relativistic klystron amplifier with three cascaded single-gap bunching cavities for efficient output

A compact coaxial relativistic klystron amplifier (RKA) with three cascaded bunching cavities is investigated to obtain high efficiency output in this paper. When the injection power and drift tube length are both decreased for the compactness of the initial coaxial RKA, the conversion efficiency of this device decreases to only 20%, which is mainly due to the insufficient modulation of intense relativistic electron beam (IREB). To solve this issue, three cascaded bunching cavities are designed to strengthen the modulation of IREB, and each bunching cavity is designed to a non-uniform single-gap cavity with a high external quality factor. Moreover, a specific drift tube length is chosen for minimizing the TEM mode leakage between every two adjacent cavities. With these methods, the self-oscillation between input and three cascaded bunching cavities can be successfully suppressed without loading any reflectors. The proposed three cascaded single-gap bunching cavities are further examined in a Ku-band coaxial RKA, and the output efficiency of this device increases to 44%, which is more than twice that of the initial coaxial RKA. Furthermore, the injection power and axial length of the propagating IREB in the improved coaxial RKA are reduced to only 5 kW and 10 wavelengths, respectively.

Investigation of Vacuum Arc Droplets From Copper, Titanium, and Tungsten by Means of Light Scattering

Studies of molten droplets emitted from cathode spots of vacuum arcs on copper, tungsten, and titanium have been carried out using a time-of-flight measurement procedure. In the arrangement, two light barriers at different distances from the cathode surface are used. When particles traverse the barriers, the appearance of scattered light can be used to establish the flight time and, thereby, the velocity of particles. Simultaneously, the intensity of scattered light provides a measure of the size of the particle by applying the Mie-scattering theory together with calibrations. By turning the cathode surface with respect to the drift tube axis, an angular resolution of the parameters was achieved. Algorithms were developed for automated processing of the measured data to identify particles arriving from the arc spot unobstructed. Distributions of the particle sizes, a statistical relation between the sizes and the emission velocities of particles, and other properties are discovered for all three cathode materials.

A System for Magnetic Measurement of the Triplet Quadrupoles for DTL

The Institute of Modern Physics (IMP) has developed a magnetic measurement system of the triplet quadrupoles in drift tube linac (DTL), based on the rotating coil method. The most important measurement requirement of the triplet in DTL is the deviation between the machinery axis of the cavity and the magnetic axis of the triplet quadrupoles, which is less than 0.1 mm, the angle deviation is less than 1 mrad. The magnetic field quality is also measured. There are two aspects to be considered when designing the system, one is the mechanical adjustment mechanisms for the three quadrupoles respectively, another is the specialized compensated coil consisting of two sets of windings which can be connected to measure the magnetic center and the high order harmonic errors. Simultaneously, optimizing the testing process is also crucial. Based on the results obtained on the two triplets in two tanks for a Heavy Ion Medical Machine with Linear Accelerator (HIMM-LINAC), the magnetic measurement system could meet the requirements