Pixel Chamber Research Articles

Pixel Chamber: A solid-state active-target for 3D imaging of charm and beauty

The Pixel Chamber project purpose is the production of the first solid state active target capable of performing continuous, high-resolution (O(μm)) 3D tracking. The aim is to create a bubble chamber-like high-granularity stack of hundreds of very thin monolithic active pixel sensors (MAPS) glued together. In this paper, the R&D to develop the first prototypes with ALPIDE sensors, designed for the ALICE experiment at the CERN LHC, will be presented. Tracking and vertexing algorithms were developed to reconstruct tracks and vertices inside Pixel Chamber. They were tested on Monte Carlo simulations which show that it is possible to obtain a high efficiency for the reconstruction of hadronic tracks, and for the primary and secondary vertices inside the detector. The tracking algorithm has been tested on test beam data to reconstruct long tracks produced in a single ALPIDE sensor parallel to a beam. Results show that it is possible to obtain very good performances in long track reconstruction on a single ALPIDE. Among the possible applications, Pixel Chamber used as an active target, has the potential to allow precision measurements of charm and beauty production. Even more interesting are possible medical and astrophysical applications. The usage of the Pixel Chamber as scatterer detector in Compton Cameras would reduce by orders of magnitude the numbers of gammas required for performing a precise source imaging, both for in vivo monitoring during hadron therapy and for astrophysics measurements.

Lines-based rotating beam profiling algorithm using pixel ionization chamber with dead pixels

In a pencil beam scanning proton therapy system, critical beam parameters, including the spot size, spot center position, and tilt angle, are monitored for security by beam profile detectors such as two-dimensional (2D) pixel-segmented ionization chambers. A method, named lines-based beam profiling (LBBP), is proposed to identify the five geometric parameters μx,μy,σx,σy,θ of rotating elliptical beam profiles using several lines (rows and columns) in the 2D detector data. The method provides solid results even in the presence of dead pixels, which can be located using a wavelet analysis. Simulation experiments were used to define the number of lines used by the LBBP method and to characterize its performance as a function of the signal-to-noise (SNR). For SNR greater than 30, the root mean square errors (RMSEs) of the beam spot size, spot center position, and rotation angle obtained with the LBBP method are less than 0.16 mm, 0.05 mm, and 0.78 degrees, respectively. The LBBP method was applied to the data collected by a pixel chamber illuminated by an X-ray source, demonstrating the capability of identifying dead pixels and providing more accurate measurements of the beam spot size and center position than the standard Gaussian fitting.

Pixel chamber: a solid-state active-target for 3D imaging of charm and beauty

The aim of the pixel chamber project is to develop the first “solid-state bubble chamber” for high precision measurement of charm and beauty. In this paper we will describe the idea for the first silicon active target conceived as an ultra-high granular stack of hundreds of very thin monolithic active pixel sensors (MAPS), which provides continuous, high-resolution 3D tracking of all of the particles produced in proton-silicon interactions occurring inside the detector volume, including open charm and beauty. We will also discuss the high-precision tracking and vertexing performances, showing that the vertex resolution can be up to one order of magnitude better than state-of-the-art detectors like the LHCb one.

Direction-sensitive dark matter search with the low-background gaseous detector NEWAGE-0.3b”

Abstract NEWAGE is a direction-sensitive dark matter search using a low-pressure gaseous time projection chamber. A low alpha-ray emission rate micro pixel chamber had been developed in order to reduce background for dark matter search. We conducted the dark matter search at the Kamioka Observatory in 2018. The total live time was 107.6 d, corresponding to an exposure of 1.1 kg$\>$d. Two events remained in the energy region of 50–60 keV, which was consistent with the expected background of 2.5 events. A directional analysis was carried out and no significant forward–backward asymmetry derived from the WIMP-nucleus elastic scatterings was found. Thus a 90$\%$ confidence level upper limit on the spin-dependent WIMP-proton cross-section of 50 pb for a WIMP mass of 100 GeV$\>c^{-2}$ was derived. This limit is the most stringent yet obtained from direction-sensitive dark matter search experiments.

Development and performance tests of μ-PIC with DLC electrodes

Micro pixel chambers (μ-PIC) with resistive cathodes have been developed as particle tracking/imaging detectors in high-rate high ionizing particle (HIP) environments. A main target of their development is as a forward muon detector in the ATLAS phase-2 upgrade. The cathode is made from DLC (diamond-like carbon) thin foil by the liftoff method. Using the resistive cathodes, the discharge (spark) probability within the HIP environment was reduced (10-1000 times) and two-dimensional readouts for the incident particles are available using a 400-micron pitch separated pixel array. We measured the tracking performances for the charged particles using a 140 GeV muon beam in CERN’s H4 beam line and also measured the imaging properties of 8 keV X-rays. Two-dimensional fine position resolutions (< 100 micron) were obtained. These results show that the resistive μ-PIC is one of strong candidate for forthcoming high-rate particle experiments.

Development of a μ-PIC with glass substrate aiming at high gas gain

Micro pixel chambers (μ-PICs), which are a type of the micro-pattern gas chambers, are usually manufactured using the printed-circuit-board (PCB) technology. However, recent application projects have begun to require higher gas gains and finer position resolution than those obtainable with current μ-PICs. It is difficult to improve the electrode structure to achieve these improvements because PCB technology limits the precision of electrode fabrication and the thickness of the substrate. We have therefore adopted micro-electro-mechanical-systems (MEMS) technology and developed the first prototype of a through-glass-via (TGV) μ-PIC. This prototype TGV μ-PIC worked well, achieving a maximum gain of approximately 20,000 and an energy resolution of 20.6% (FWHM) at 5.9 keV over the whole 5 × 5 cm2 detection area.

Development of the Micro Pixel Chamber with DLC cathodes

We developed a novel design of a Micro Pixel Chamber (μ-PIC) with resistive electrodes for a charged particle tracking detector in high rate applications. Diamond Like Carbon (DLC) thin film is used for the cathodes. The resistivity can be controlled flexibly (105−7Ω/sq.) with high uniformity. The fabrication process was greatly improved and the resistive μ-PIC could be operated with an area of 10 × 10 cm2. Resistors for the HV bias and capacitors for the AC coupling were completely removed by applying PCB and carbon sputtering techniques, and the resistive μ-PIC became a very compact detector. The performance of our new resistive μ-PIC was measured in various ways. Consequently, it was possible to attain high gas gains (>104), high detection efficiency, and position resolution better than 100 μm. The spark probability was reduced, and the new resistive μ-PIC was operated stably under fast neutrons irradiation. These features offer solutions for a charged particle tracking detector in future high rate applications.

Development of the micro pixel chamber based on MEMS technology

Micro pixel chambers (μ-PIC) are gaseous two-dimensional imaging detectors originally manufactured using printed circuit board (PCB) technology. They are used in MeV gamma-ray astronomy, medicalimaging, neutron imaging, the search for dark matter, and dose monitoring. The position resolution of the present μ-PIC is approximately 120 μm (RMS), however some applications require a fine position resolution of less than 100 μm. To this end, we have started to develop a μ-PIC based on micro electro mechanical system (MEMS) technology, which provides better manufacturing accuracy than PCB technology. Our simulation predicted the gains of MEMS μ-PICs to be twice those of PCB μ-PICs at the same anode voltage. We manufactured two MEMS μ-PICs and tested them to study their behavior. In these experiments, we successfully operated the fabricatedMEMS μ-PICs and we achieved a maximum gain of approximately 7×103 and collected their energy spectra under irradiation of X-rays from 55Fe. However, the measured gains of the MEMS μ-PICs were less than half of the values predicted in the simulations. We postulated that the gains of the MEMS μ-PICs are diminished by the effect of the silicon used as a semiconducting substrate.

Development of μ-PIC with resistive electrodes using sputtered carbon

The Micro Pixel Chamber (μ-PIC) has been developed for a hadron-collider experiment. The main purpose is detecting Minimum Ionizing Particles (MIP) under high-rate Highly Ionizing Particles (HIP) environment. In such an environment, sufficient gain to detect MIP is needed, but continuous sparks will be caused by high-rate HIP. To reduce sparks, cathodes are made of resistive material. In this report, sputtered carbon was used as a new resistive cathode. Gas gain &gt;104 was achieved using an 55Fe source. This value is sufficient to detect MIP without GEM or other floating structures. Also, thanks to production improvement, pixels are well aligned in the entire detection area.

NEWAGE - Direction-sensitive Dark Matter Search Experiment

NEWAGE is a direction-sensitive WIMP search experiment using micro pixel chamber. After our first underground measurement at Kamioka in 2009, we constructed a new detector, which was designed to have a twice larger target volume with low background material, a lowered threshold of 50 keV, an improved data acquisition system. In 2013, dark matter search in Kamioka underground laboratory was performed. We have succeeded to lower the background level by about one order of magnitude.

Micro Pixel Chamber with resistive electrodes for spark reduction

The Micro Pixel Chamber (μ-PIC), a detector using resistive electrodes,has been developed and tested. The surface cathodes are made fromresistive material, which helps to reduce the electrical field in alarge flow of current. Two-dimensional readouts are provided byanodes and pickup electrodes, on which the signals are induced. Highgas gain ( > 6 × 104 ) was measured using a 55Fe (5.9 keV)source, and extensive spark reduction was attained with fast neutrons.The spark rate of the resistive μ-PIC was 10−4 times lowerthan that of the conventional μ-PIC at a gain of 104. Withthese developments, a new MPGD with a non-floating structure isachieved, offering the required levels of both gain and stability todetect MIP particles. In addition, by using resistive cathodes,μ-PIC can be operated with no HV applied on the anodes. NeitherAC coupling capacitors nor HV pull-up resistors are needed for anyanode. Consequently, the signal readout can be dramaticallysimplified by this configuration.

Simulation of gas avalanche in a micro pixel chamber using Garfield++

A micro pixel chamber (μ-PIC), the development of which started in 2000 as a type of a micro pattern gas detector,has a high gas gain greater than 6000 in stable operation, a large detection area of 900 cm2, and a fine position resolution of about 120 μm.However, for its development, simulation verification has not been very useful,because conventional simulations explain only part of the experimental data.On the other hand, some μ-PIC applications require precise understanding of the fluctuation of the gas avalanche and signal waveform for their improvement;therefore, there is a need to update the μ-PIC simulation.Hence, we adopted Garfield++, which is developed for simulating a microscopic avalanche in an effort to explain experimental data.The simulated avalanche size was well consistent with the experimental gas gain.Moreover, we calculated a signal waveform and successfully explained the pulse height and time-over-threshold.These results clearly indicate that the simulation of μ-PIC applications will improveand that Garfield++ simulation will easily facilitate the μ-PIC development.

Performance studies of Micro Pixel Chamber for the ATLAS upgrade

The Micro Pixel Chamber (μ-PIC) is being developed as a muon chamber of the ATLAS experiment in an HL-LHC environment. In the ATLAS muon system, a high flux of fast neutron background causes instability operation of the detectors. We performed neutron irradiation tests with μ-PIC to optimize the operation gas and detector structure. In addition, we studied neutron interactions with the detector, in order to understand the effect of fast neutrons.

Quantitative Measurement of Element Distributions using the Neutron-transmission Resonance-absorption Method

Abstract The imaging method known as Neutron Resonance Absorption (NRA) is very suitable for nondestructive analysis of element distributions in a sample. The purposes of this study are to perform NRA test experiments using the Micro Pixel Chamber (μPIC), developed by Kyoto University and to confirm the quantitative quality of the measurements of the system. The experiment was performed at NOBORU in J-PARC. The detector was located at 14.5 m from the moderator in the experimental room. The samples, consisting of thin Cobalt, Tantalum and Molybdenum foils, were placed individually at the upstream from the detector. In the experiment, the transmission spectra with the samples and no sample were obtained. Background components were not so small in these measurements. From the neutron transport simulation, it was surmised that the origin of this background was due to scattering of neutrons in the experimental room. Therefore, the assumed background components were subtracted from the measurement data. Finally, it was found that the difference between the measurement data and the nuclear data was within about 20%. Issues remaining to be solved include how to obtain precise background data quantitatively in the case of a large absorption cross section.

PRELIMINARY CHARACTERIZATION TESTS OF DETECTORS OF ON-LINE MONITOR SYSTEMS OF THE ITALIAN NATIONAL CENTER OF ONCOLOGICAL HADRON-THERAPY (CNAO)

Introduction Hadron-therapy is an effective technique used to treat tumors that are located between or nearby vital organs. The Italian National Center of Oncological Hadron-therapy (CNAO) has been realized as the first facility in Italy to treat very difficult tumors with protons and Carbon ions. The on-line monitor system for CNAO has been developed by the Department of Physics of the University of Torino and Italian National Institute of Nuclear Physics (INFN). The monitoring system performs the on-line checking of the beam intensity, dimension, and beam position. Materials and Methods The monitor system is based on parallel plate ionization chambers and is composed of five ionization chambers with the anodes fully integrated or segmented in pixels or strips that are placed in two boxes. A series of measurements were performed that involve the background current and the detectors have been characterized by means of a series of preliminary testes in order to verify reproducibility and uniformity of the chambers using an X-ray source. Results The measured background currents for StripX, StripY and Pixel chambers are five orders of magnitude smaller than the nominal treatment current. The reproducibility error of chambers is less than 1%. The analysis of the uniformity showed that the monitor devices have a spread in gain that varies, but only about 2%. Conclusion The reproducibility and the uniformity values are considered as a good result, taking into account that the X-ray energy range is several orders of magnitude smaller than the particle energies used at CNAO.

Design and characterization of the beam monitor detectors of the Italian National Center of Oncological Hadron-therapy (CNAO)

A new hadron-therapy facility implementing an active beam scanning technique has been developed at the Italian National Center of Oncological Hadron-therapy (CNAO). This paper presents the design and the characterization of the beam monitor detectors developed for the on-line monitoring and control of the dose delivered during a treatment at CNAO. The detectors are based on five parallel-plate transmission ionization chambers with either a single large electrode or electrodes segmented in 128 strips (strip chambers) and 32×32pixels (pixel chamber). The detectors are arranged in two independent boxes with an active area larger than 200×200mm2 and a total water equivalent thickness along the beam path of about 0.9mm. A custom front-end chip with 64 channels converts the integrated ionization channels without dead-time.The detectors were tested at the clinical proton beam facility of the Paul Scherrer Institut (PSI) which implements a spot scanning technique, each spot being characterized by a predefined number of protons delivered with a pencil beam in a specified point of the irradiation field. The short-term instability was measured by delivering several identical spots in a time interval of few tenths of seconds and is found to be lower than 0.3%. The non-uniformity, measured by delivering sequences of spots in different points of the detector surface, results to be lower than 1% in the single electrode chambers and lower than 1.5% in the strip and pixel chambers, reducing to less than 0.5% and 1% in the restricted 100×100mm2 central area of the detector.

NEWAGE

The NEWAGE project (NEw generation WIMP search with an Advanced Gaseous tracking device Experiment) is a direction-sensitive dark matter search experiment, searching for WIMPs (Weakly Interacting Massive Particle) via nuclear recoil. We adopted μ-PIC (micro PIxel Chamber) to our detector. Then, we first obtained and updated the direction-sensitive exclusion limit. In this paper, we introduce NEWAGE experiment.

Neutron beam tests for Micro Pixel Chamber (μ-PIC)

We have tested the Micro Pixel Chamber (μ- PIC) with a fast neutron source which is a candidate to replace the forward muon trigger system of the ATLAS experiment in the luminosity upgrade. We performed the test of the behavior of μ-PIC under a high neutron background environment, as is expected in ATLAS, using a 7 MeV neutron beam at Kobe University. In order to find the gas mixture with less sparks, spark rates were measured for several gas mixtures; Ar+C2H6, Ne+C2H6, and Ne+C2H6+CF4 gases. Using tungsten and nickel for the drift mesh, the effects of sparks from detector materials were also studied. In this paper, we concentrate on the setup for the neutron tests. The details of the experimental results can be found in [1].

SU-E-I-63: Performance Study of An Electron-Tracking Compton Camera for Medical Imaging.

Conventional gamma-ray detector, PET and SPECT, have the limitation of energy and field of view. These limitations are major problems of studying for a new medical imaging. Therefore, we have developed the new imaging detector which is an electron-tracking Compton camera (ETCC). A reconstruction method of Compton camera (CC) is using the physics principle. Because of using physics principle, CC can have a wide energy dynamic range and wide field of view. Conventional CC, however, cannot catch Compton recoil electron tracks, and this is one of the reasons of low imaging power. We have developed a time projection chamber (TPC) using micro pixel chamber (μPIC) as the new detector for ETCC. The μPIC is 2-dimensional gaseous detector and this position resolution is less than 400 μm. Using this detector, ETCC can get electron tracks which are generated from Compton scattering. In this paper, we show the prototype ETCC performance and imaging results. ETCC achieved a wide energy dynamic range (200-1300keV) and wide field of view (3 steradian). Also we succeeded in imaging new imaging reagents using mice as follows; (1) F-18-FDG (511 keV) and I-131-MIBG (364 keV) simultaneous imaging for double clinical tracer imaging, (2) Zn-65- porphyrin (1116 keV) imaging for high energy gamma-ray imaging and, (3) imaging of some minerals (Mn-54, Zn-65) in mice and so on. And we succeeded in 3-D imaging which has imaged only one direction using one head camera. We have developed the ETCC for new medical imaging device and succeeded in imaging the some imaging reagents. We started to develop the new ETCC which can image the mouse within 30 min. Thus, this detector has the possibility of new medical imaging.

Development of Micro Pixel Chamber with resistive electrodes

We developed and tested Micro Pixel Chambers (μ-PIC) using resistive materialsas electrodes. The μ-PIC is one MPGD without such floating devices as wire, mesh, or foil. It has been used around 104 of gas multiplication for MIP particles and X-rays. However, such highly ionizing particles as low energy protons or heavy ions create sparks between electrodes due to an excess of ionization electrons, which may destroy the electrodes. This problem is a very critical for using MPGD for intense hadron experiments, such as LHC. To overcome it, we have developed a new μ-PIC design. The cathode electrodes are covered by resistive materials that reduce the electric field between the anodes and the cathodes on the dense ionized particles. In our first prototype, gas gain was observed that exceeded 104. To overcome the remaining problems of the discharge, we tested several designs of materials and structures. In this paper, we reportthe results of tests and the progress of developing a new design.