Double-sided Silicon Strip Detectors Research Articles

Measurements of proton beam attenuation radiographs at a clinical facility

In recent years, a proton computed tomography (pCT) demonstrator was installed and tested at the MedAustron facility in Wiener Neustadt, Austria. It consists of four double-sided silicon strip detectors (DSSDs) for particle tracking and a range telescope to obtain the residual range of the protons that passed through the object to be imaged. Besides conventional pCT, which uses the energy loss information of the single ions, the tracker of the demonstrator also allows for other imaging modalities such as beam attenuation imaging (also referred to as fluence loss imaging). When a proton beam passes through a medium, a certain fraction of the incident primary particles gets absorbed due to the inelastic scattering with the atomic nuclei of the material. Recent studies investigating proton imaging based on inelastic nuclear scattering at clinical energies with single-particle tracking used Monte Carlo simulations and lack additional experimental validation. In this work, proton radiographs based on beam attenuation were measured at clinical beam energies (100.4 MeV, 145.4 MeV) and, for the first time, at 800 MeV. As phantom, an aluminum stair profile was imaged at two different rotation angles to investigate material thicknesses between 2 mm and 10 mm. The recorded beam attenuation was compared to existing reference data from prior measurements and the inelastic nuclear cross sections as incorporated in the Geant4 database. Furthermore, the measurement at 800MeV could be compared to an existing measurement of the inelastic nuclear cross section of aluminum at a similar energy (792.9 MeV).

Absolute mass calibration of fission product distributions measured with the E-[formula omitted] method

The mass calibration of fission product distributions measured with the energy–velocity (E-υ) method constitutes a technical challenge. The energy loss of the fission fragments in the various dead layers of the spectrometer and other sources of pulse-height defects of the energy detectors are a significant source of systematic uncertainty in the mass calculations used to determine the measured fission product yields. In this study, the absolute calibration of the fission mass distributions is accomplished by measuring prompt γ-rays in coincidence with the fission fragments. This allows for the direct calibration of the mass spectra and eliminates any dependence on potentially complicated energy corrections. The first test measurement was performed at the Los Alamos Neutron Science Center employing the SPectrometer for Ion DEtermination in fission Research (SPIDER). SPIDER is a 2E-2υ spectrometer designed for measuring independent fission product yields from neutron-induced fission. In this test, the single-arm SPIDER (E-υ) system and an array of 252Cf sources were used. The single-arm system consisted of two time pick-off detectors for measuring the time-of-flight of the fission fragments and a double-sided silicon strip detector (DSSD) for measuring the kinetic energy. Characteristic γ-rays from fission fragments were detected using three high-purity germanium (HPGe) detectors. For the mass calibration, γ–mass coincidence events from twelve product isotopes were used. The measured FPYs from 252Cf spontaneous fission were found to be in excellent agreement with the evaluated data after applying the absolute mass calibration. From the γ–mass coincidence events, the mass resolution of the system was also extracted. An average mass resolution of ∼1.4 AMU (FWHM) for the light fragments and ∼2.4 AMU (FWHM) for the heavy fragments were found. This was the first in-situ calibration and characterization of the SPIDER spectrometer, which paves the way for high-quality FPY measurements with this instrument.

Design of the Front-End Electronics for Silicon Beam Profilometer Prototype for Light Ions at the BM@N Experiment

Baryonic matter at nuclotron (BM@N) is the fixed-target experiment at the Nuclotron based Ion Collider fAcility (NICA) complex [the Joint Institute for Nuclear Research (JINR), Dubna]. Two beam profilometer planes will be placed inside the beam pipe and used for a beam tuning during the initial stage in the BM@N experiment. According to the physics program of the experiment, beam ions are foreseen from carbon to gold. Due to the wide input charge range, two versions of front-end electronics (FEEs) for the beam profilometer will be used—for light and heavy ions. The article presents the first stage of a beam profilometer development—the design of a prototype for light ions based on a double-sided silicon strip detector and FEE application-specific integrated circuits (ASICs).

Track recognition for the [formula omitted] telescopes with silicon strip detectors

For the high granularity and high energy resolution, Silicon Strip Detector (SSD) is widely applied in assembling telescopes to measure the charged particles in heavy ion reactions. In this paper, we present a novel method to achieve track recognition in the SSD telescopes of the Compact Spectrometer for Heavy Ion Experiment (CSHINE). Each telescope consists of a single-sided silicon strip detector (SSSSD) and a double-sided silicon strip detector (DSSSD) backed by 3 × 3 CsI(Tl) crystals. Detector calibration and track reconstruction are implemented. Special decoding algorithm is developed for the multi-track recognition procedure to deal with the multi-hit effect convoluted by charge sharing and the missing signals with certain probability. It is demonstrated that the track recognition efficiency of the method is approximately 90% and 80% for the DSSSD-CsI and SSSSD–DSSSD events, respectively.

The SFiNx Detector System

A new detector system for investigating the properties of spontaneous fission of short-lived transuranium nuclei has been created. This system consists of an assembly of double-sided silicon strip detectors surrounded by 116 proportional neutrons counters filled with 3He. The neutron registration efficiency is 54.7 ± 0.1%. The detector system is tested in an experiment investigating the characteristics of spontaneous fission of the 252No isotope. The experimental data on neutron yields are compared with previously published results. The average number of neutrons per fission act ( $$\bar {\nu }$$ = 4.25 $$ \pm $$ 0.09) and the multiplicity distribution of prompt neutrons are obtained. The true form of the neutron distribution is reconstructed via a statistical regularization.

Stopping power measurement for proton therapy by combining proton radiography and X-ray CT

Exact information on the relative stopping power (RSP) of the high-energy proton in the human body is necessary to precisely control radiation dose and position in proton beam therapy. RSP has been estimated by converting the X-ray computed tomography (CT) information. However, it causes up to 5% uncertainty in the RSP measurements because of the fundamental difference between the X-ray and proton interaction. Therefore, this study investigates a scheme of the RSP distribution measurement in the human body with a combination of X-ray CT and proton radiography with beam injection to a single direction. We studied the accuracy of the RSP measurement using GEANT4 simulation with silicon trackers, crystal calorimeter, and proton beam. The RSP accuracy has been generally measured below 1% from the reference values for simple objects with multi cylindrical shapes. The simulation results present the requirements of a proton tracking system on the spatial resolution and the acquisition rate. We developed a tracking detector prototype consisting of double-sided silicon strip detectors and amplifier–shaper–discriminator LSI chips. We evaluated the performance with an 80 MeV proton beam in Cyclotron and Radioisotope Center, Tohoku University. It succeeded in reconstructing a proton trajectory with 160 kHz and fulfilled the requirements to realize the proposed scheme. Furthermore, this study describes the detailed study of the scheme of the RSP measurement and the beam test of the tracking system prototype.

Different radiographic imaging modalities with a proton computed tomography demonstrator

Proton computed tomography aims at improving proton-beam therapy, which is an established method to treat deep-seated tumours in cancer therapy. In treatment planning, the stopping power (SP) within a patient, describing the energy loss of a proton in a tissue, has to be known with high accuracy. However, conventional computed tomography (CT) returns Hounsfield units (HU), which have to be converted to SP values to perform the required treatment planning, thus introducing range uncertainties in the calculated dose distribution. Using protons not only for therapy but also for the preceding planning CT enables the direct measurement of the SP. Hence, this imaging modality eliminates the need for further conversion and therefore offers the possibility to improve treatment planning in proton therapy. In order to examine the principles of such a proton CT (pCT) setup, a demonstrator system, consisting of four double-sided silicon strip detectors and a range telescope, was built. The performance of the pCT demonstrator was tested with measurements at the MedAustron facility in Wiener Neustadt, Austria. In this paper, 2D imaging modalities going beyond the idea of a standard proton radiography, will be discussed. Namely, fluence loss imaging and scattering radiography results obtained with the demonstrator will be shown. The advantage of these modalities is that they do not rely on an additional energy measurement and can therefore be conducted only with the tracker of the demonstrator.

The Test Bench for BM@N Forward Silicon Tracker Front-End Electronics and Silicon Modules

The forward silicon tracker (FST) is an integral part of the central tracker located in the analyzing magnet of the Baryonic Matter at Nuclotron (BM@N) experiment setup to improve the efficiency and accuracy of the particle tracks and primary vertex reconstructions. The FST consists of three planes based on 42 double-sided silicon strip detector modules. To meet the experiment requirements, each front-end electronics (FEE) printed circuit board (PCB) and the silicon module should be effectively tested before installation to the FST subsystem. This task was solved by designing and producing a test bench. The test bench consists of special testing boxes for FEE PCBs, silicon modules, power supply, slow controls, and data acquisition subsystems. The data acquisition subsystem uses an field-programmable gate array (FPGA)-based control unit, and data storage and analysis subsystems to control the data flows in the test bench during measurements. All measurements are managed, stored, and analyzed automatically. The test bench provides a user-friendly web interface inside the local network for the raw and analyzed data and individual test reports for each device. The test bench structure, testing procedures, data analysis algorithms, and test results are described in detail.

Prototype readout electronics of a double-sided silicon strip detector for space exploration.

Double-sided silicon strip detectors (DSSDs) have been widely used in interplanetary exploration. In this study, the prototype readout electronics of a DSSD for space exploration is presented. It mainly includes a front-end readout module (FEM) and a data acquisition module (DAM). The FEM is responsible for acquiring the charge of the DSSD signals based on an application-specific integrated circuit and polarity inverter circuits. The DAM with a field programmable gate array is employed to perform online calculations of the position and energy as well as data packaging and transfer. Test results show that the electronics has dynamic ranges of 6-2500 and -6 to -2500 fC with an integral nonlinearity of no more than 0.5%, while the root-mean-square noise level is less than 1.9 fC. Joint tests with the DSSD indicate that a full width at half maximum energy resolution of 3.25% at 5.486 MeV and a position resolution of 1.19 mm were achieved.

A Novel Method of Analyzing a Reaction Using the Data from Particle and Gamma-ray Detectors

The radioactive isotope beam (RIB) of 25Na at 5MeV/u energy in maximum 3x107 pps intensity was fired on a deuterated polyethylene (CD2) to investigate mainly (d,p gamma) reaction. However, there were other reaction possibilities, which were arisen from the same collision, to be eliminated wisely. As to a particle detector and a gamma-ray detector, highly selective double-sided silicon strip detectors (DSSSD) and high purity germanium detectors (HPGe) were employed to make delicate selections of distinctive energies of experimentally populated excited states of 26Na. The motivation of this work was to show how to combine the information coming out of two different types of detectors in terms of energies to reach out a new unobserved data. This study was a part of the experiment with Silicon Highly-segmented Array for Reactions of Coulex (SHARC) and TRIUMF-ISAC Gamma-ray Escape-Suppressed Spectrometry (TIGRESS) in Canada.

A Compact Spectrometer for Heavy Ion Experiments in the Fermi energy regime

A Compact Spectrometer for Heavy IoN Experiments (CSHINE) has been recently built for the studies of heavy ion reactions at intermediate energies. CSHINE consists of a Si-Si-CsI telescope array and a parallel plate avalanche counter (PPAC) array. Each telescope consists of a thin single-sided silicon strip detector and a thick double-sided silicon strip detector backed by a 3 × 3 CsI(Tl) crystal hodoscope. The thicknesses of the silicon detectors are optimized in order to identify various types of light charged particles in a wide energy range. PPAC is a large-area two-dimensional position-sensitive gas detector, which records fission fragments with the intrinsic efficiency of approximately 100% but filters out light charged particles at properly selected working conditions. In the phase-II run, four Si-Si-CsI telescopes and three PPACs have been installed and operated in the beam experiment with 25 MeV/u Kr+Pb reactions. Particle identification for isotopes from Hydrogen to Boron has been achieved with the Si-Si-CsI telescopes, while excellent timing and position resolution have been achieved with the PPACs.

β-decay and isospin symmetry breaking

<p indent=0mm>The elegant concept of isospin symmetry is of fundamental importance in nuclear and elementary particle physics. As a β-decay process changes an up quark to a down quark or <italic>vice versa</italic>, studies of nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, can be a powerful means to probe isospin symmetry breaking. A series of β-decay experiments of sd-shell nuclei near the proton drip line produced by projectile fragmentation were performed at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou (HIRFL-RIBLL1) using a silicon array with a high detection efficiency and a low detection threshold. The secondary ions were identified by the combination of Δ<italic>E</italic>-TOF and magnetic rigidity (<italic>Bρ</italic>) in which the time of flight (TOF) was measured by two plastic scintillators at the second and fourth focal planes of the RIBLL1 and the energy loss (Δ<italic>E</italic>) was measured by two silicon detectors in the front of the silicon array. Double-sided silicon strip detectors (DSSDs) in the center of the array served to measure the residual energies of secondary ions on an event-by-event basis and study their decay properties with an implantation-decay correlation. Several quadrant silicon detectors (QSDs) placed behind DSSDs were used for anticoincidences of the penetrating fragments and light particles coming along with the beam, and measurements of β particles and high-energy protons. The β-delayed proton peaks with known energies and their corresponding absolute intensities were used for the energy and detection efficiency calibrations of the DSSDs. The system allows us to measure protons with energies down to about <sc>200 keV</sc> without obvious β background in the proton spectrum and was successful to measure the energies, time, and positions of implanted ions and decay protons efficiently, supporting researchers to study the decay properties of nuclei towards the proton drip line. The β-decay data, together with the large-scale shell-model calculations, allows detailed investigations on the mirror-nuclei systems resulting in the systematic study of isospin symmetry breaking in the sd-shell nuclear region. It was found that the mirror asymmetry parameters become larger due to the smaller separation energies while approaching the proton drip line for the extremely proton-rich sulfur nuclei ^27,28,29S and the Coulomb forces and other isospin-symmetry nonconserving forces acting between protons would lead to extended proton wave functions and cause mirror asymmetries. The properties of ²²Si β-decay for the transitions to the low-lying states of ²²Al were measured, and the reduced transition probabilities were determined. Comparing with the data on the β-decay of the mirror nucleus ²²O, we found a mirror asymmetry of <italic>δ</italic>=209(96)% in the transition to the first 1⁺ excited state of the respective daughters. This is by far the largest value of <italic>δ</italic> observed in the low-lying states. Shell-model calculations with isospin-nonconserving forces, including the <italic>T</italic>=1,<italic> J</italic>=2, 3 interactions related to the s_1/2 orbit that introduces explicitly the isospin-symmetry breaking force and describes the loosely bound nature of the wave functions of the s_1/2 orbit, can reproduce the observed data well and demonstrate that this dramatically large mirror asymmetry is attributed to the significant proton occupation and loosely bound nature of the wave functions of the s_1/2 orbit, which suggests that ²²Al is a proton-halo nucleus.

Systematic study of the [formula omitted]([formula omitted],p)[formula omitted] reaction for NRA applications

The differential cross sections of the first two proton groups of the 12C(3He,p)14N reaction were determined within the 3He energy range 1.34–2.86 MeV and for backward angles from 107o107o to 164o with 2o steps using two double sided silicon strip detectors. The results are presented in graphical form and they are also given as tables in the Appendix. Aiming to assist in the enrichment of the reaction database and the improvement of the differential cross section data quality, the determined cross sections were benchmarked with the measurement of thick target reaction yields from a pure glassy carbon target at two 3He energies, 2.0 and 2.7 MeV. Furthermore, the data were accompanied by R-Matrix theory calculations, allowing for cross section data interpolation with sufficient accuracy.

One detector, all the light elements – Low-background NRA, RBS and ERDA for the quantification of elements from hydrogen to fluorine

Presented is a review of the accomplishments, of the light-element program, conducted at the Lund Ion-Beam Analysis Facility. A detailed account is given of the current experimental setup at the total Ion-Beam Analysis Chamber, which is equipped with two Double-Sided Silicon Strip Detectors for charge particle detection, a silicon drift detector for PIXE analysis, an electrostatic deflection system for charge measurement and implements a Nuclear Micro-Probe. A summary of the work conducted to date on the quantification of low Z elements is presented on a case by case basis. Details of the current work efforts and an overview of the advances which are intended in the near future are given.

Sub-threshold states in Ne19 relevant to F18(p,α)O15

Classical novae result from thermonuclear explosions producing several $\gamma$-ray emitters which are prime targets for satellites observing in the MeV range. The early 511 keV gamma-ray emission depends critically on the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate which, despite many experimental and theoretical efforts, still remains uncertain. One of the main uncertainties in the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate is the contribution in the Gamow window of interference between sub-threshold $^{19}$Ne states and known broad states at higher energies. Therefore the goal of this work is to clarify the existence and the nature of these sub-threshold states. States in the $^{19}$Ne compound nucleus were studied at the Tandem-ALTO facility using the $^{19}$F($^3$He,t)$^{19}$Ne charge exchange reaction. Tritons were detected with an Enge Split-pole spectrometer while decaying protons or $\alpha$-particles from unbound $^{19}$Ne states were collected, in coincidence, with a double-sided silicon strip detector array. Angular correlations were extracted and constraints on the spin and parity of decaying states established. The coincidence yield at $E_x$ = 6.29 MeV was observed to be high spin, supporting the conclusion that it is indeed a doublet consisting of high spin and low spin components. Evidence for a broad, low spin state was observed around 6 MeV. Branching ratios were extracted for several states above the proton threshold and were found to be consistent with the literature. R-matrix calculations show the relative contribution of sub-threshold states to the astrophysically important energy region above the proton threshold. The levels schemes of $^{19}$Ne and $^{19}$F are still not sufficiently well known and further studies of the analogue assignments are needed. The tentative broad state at 6 MeV may only play a role if the reduced proton width is large.

Towards background-free studies of capture reaction in a heavy-ion storage ring

Stored and cooled, highly-charged ions offer unprecedented capabilities for precision studies in the realm of atomic, nuclear structure and astrophysics[1]. After the successful investigation of the 96Ru(p,7)97Rh reaction cross section in 2009[2], the first measurement of the 124Xe(p,7)125Cs reaction cross section has been performed with decelerated, fully-ionized 124Xe ions in 2016 at the Experimental Storage Ring (ESR) of GSI[3]. Using a Double Sided Silicon Strip Detector, introduced directly into the ultra-high vacuum environment of a storage ring, the 125Cs proton-capture products have been successfully detected. The cross section has been measured at 5 different energies between 5.5AMeV and 8AMeV, on the high energy tail of the Gamow-window for hot, explosive scenarios such as supernovae and X-ray binaries. The elastic scattering on the H2 gas jet target is the major source of background to count the (p,7) events. Monte Carlo simulations show that an additional slit system in the ESR in combination with the energy information of the Si detector will enable background free measurements of the proton-capture products. The corresponding hardware is being prepared and will increase the sensitivity of the method tremendously.

Beam background study for the Belle II Silicon Vertex Detector

The Belle II experiment aims to accumulate 50ab−1 of e+e− collision data at the SuperKEKB asymmetric energy collider (Tsukuba, Japan). The first physics data using all Belle II detectors were taken in spring 2019.In the vast physics program of the Belle II experiment, the vertex detector plays a crucial role for the determination of the B-meson decay vertices. It consists of two inner layers of pixelated silicon detectors and four outer layers of double-sided silicon strip detectors (SVD).To achieve a design luminosity of 8×1035cm−2s−1, 40 times higher than the recorded luminosity of its predecessor, the SuperKEKB collider squeezes the beams to a vertical size of 50 nm (“nano-beam scheme”) and doubles the beam currents.Therefore, the detectors are required to tolerate intense beam induced background due to the very high luminosity. During the 2019 spring run we measured the occupancy rate in the SVD to estimate the level of the beam induced background. With the low initial luminosity, the observed beam induced background mostly originated from Touschek processes and beam-gas scattering within individual beams. Since these different background contributions depend differently on accelerator conditions, such as the beam current, beam size and pressure, they can be disentangled. We estimate the background rate of each contribution and compare them with simulated ones. The results enable us to predict the background levels at increased beam currents and luminosity in the coming years. They also hint at background mitigation measures for running at higher luminosity. In this proceeding we present the results of our study of the beam induced background in the SVD and the prospects for future operation.

Imaging with protons at MedAustron

Ion beam therapy has become a frequently applied form of cancer therapy over the last years. The advantage of ion beam therapy over conventional radiotherapy using photons is the strongly localized dose deposition, leading to a reduction of dose applied to surrounding healthy tissue. Currently, treatment planning for proton therapy is based on X-ray computed tomography, which entails certain sources of inaccuracy in calculation of the stopping power (SP). A more precise method to acquire the SP is to directly use high energy protons (or other ions such as carbon) and perform proton computed tomography (pCT). With this method, the ions are tracked prior to entering and after leaving the patient and finally their residual energy is measured at the very end. Therefore, an ion imaging demonstrator, comprising a tracking telescope made from double-sided silicon strip detectors and a range telescope as a residual energy detector, was set up. First measurements with this setup were performed at beam tests at MedAustron, a center for ion therapy and research in Wiener Neustadt, Austria. The facility provides three rooms for cancer treatment with proton beams as well as one which is dedicated to non-clinical research.This contribution describes the principle of ion imaging with proton beams in general as well as the design of the experimental setup. Moreover, first results from simulations and recent beam tests as well as ideas for future developments will be presented.

On the [formula omitted]-detection efficiency of a combined Si and plastic stack detector for DESPEC

A Geant4 simulation has been carried out in order to determine the β-detection efficiency of a rare isotope beam implantation setup, for decay spectroscopy experiments, comprising a number of Double Sided Silicon Strip Detectors (DSSSDs) and two plastic scintillation detectors placed upstream and downstream. The absolute efficiency for the emitted β-particle detection from radioactive fragments implanted in the DSSSDs using fast-timing plastic-scintillator detector, is calculated. The detection efficiency of the setup has been studied with two different distances between the Si layers and plastics. The requirement for the thickness of the Si detector layers and its implication on the β-detection efficiency has been investigated for 1 mm and 300μm thickness of Si layers. The combined efficiency of DSSSD and plastic detectors were also simulated for two different thicknesses of the DSSSD.

Performance of the Belle II Silicon Vertex Detector

The Belle II experiment at the SuperKEKB collider of KEK (Japan) started recording physics data in spring 2019 with all its subdetectors installed and with the goal of accumulating 50ab−1 of e+e− collision events at the unprecedented instantaneous luminosity of 8×1035cm−2s−1, about 40 times larger than its predecessor. The Belle II vertex detector plays a crucial role in the broad Belle II physics program, especially for time-dependent CP measurements. It consists of two layers of DEPFET-based pixels and four layers of double-sided silicon strip detectors (SVD).The experience gained from the first period of SVD operation can be summarized as smooth and reliable running of the detector, with high stability of noise levels and calibration parameters obtained from local calibration runs. No major problem has been experienced. The detector even survived a few serious radiation accidents in which the beam was lost due to failure in the machine focusing quadrupoles without any notable damage. The SVD performance were carefully studied with these first physics data. The SVD showed excellent hit and tracking efficiency. Moreover, cluster energy and signal to noise ratio as well as the hit time and spatial resolutions measured on data showed a fair agreement with the expected performance.