Search

After the accident at the Fukushima Daiichi Nuclear Power Plant, artificial radionuclides such as radioactive cesium and iodine were released into the environment. It caused great anxiety not only in the vicinity of the Fukushima Daiichi Nuclear Power Plant but also in other regions of the world. Some members of the Japan Health Physics Society (JHPS), a leading academic society in Japan in the field of radiation protection, volunteered to establish a website called “Question and Answer (Q&A) about radiation in daily life” shortly after the accident to help reduce the residents’ anxiety about the health effects of radiation. In August 2011, “Committee for Q&A about radiation in daily life” was established in JHPS, making the website-related activities a responsibility of JHPS. The Q&A website continued to respond to the questions from the general public with expertise and sincerity until February 2013 when the Committee members decided to end the activities because the number of questions received had gradually decreased with the passage of time. This paper aims to introduce the following: the activities of the Q&A website during the two years (2011–2013), the stance chosen for the activities, the information related to the website activities and the analysis of Twitter data. Building on the experience and the knowledge obtained from the activities, it also discusses issues and experiences that can be utilized in the initial response to emergencies for radiation protection experts as well as those in other fields.

Event popularity quantification is essential in the determination of current trends in events on social media and the internet. Particularly, it is important during a crisis to ensure appropriate information transmission and prevention of false-rumor diffusion. Here, we propose Net-TF-SW - a noise-robust and explainable topic popularity analysis method. This method is applied to tweets related to COVID-19 and the Fukushima Daiichi Nuclear Disaster, which are two significant crises that have caused significant anxiety and confusion among Japanese citizens. The proposed method is compared to existing methods, and it is verified to be more robust with respect to noise.

Information spreading on social media is a crucial issue to build a safe society. In particular, during emergencies, misinformation and uncertain information can lead to social disruption and cause significant damage to our lives. Here we built a retweet network from 24 million radiation-related tweets by 1.3 million accounts in the immediate aftermath of the Fukushima nuclear power plant accident in 2011. Then we simulated the information spreading on the network to explore ways to spread scientifically accurate information. Our simulation replicated the reality in which the number of scientific evidence-based tweets experienced a gradual decline while the number of emotional tweets increased. We also showed that increasing new direct retweets from the influencers could effectively spread scientific evidence-based information in our hypothetical simulations.

The ASACUSA (Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration plans to measure the ground-state hyperfine splitting of antihydrogen in a beam at the CERN Antiproton Decelerator with initial relative precision of 10-6 or better, to test the fundamental CPT (combination of charge conjugation, parity transformation and time reversal) symmetry between matter and antimatter. This challenging goal requires a polarised antihydrogen beam with a sufficient number of antihydrogen atoms in the ground state. The first measurement of the quantum state distribution of antihydrogen atoms in a low magnetic field environment of a few mT is described. Furthermore, the data-driven machine learning analysis to identify antihydrogen events is discussed., 18 pages, 10 figures

BACKGROUND Rural physician undersupply is a universal concern, leading to sudden physician absenteeism or unavailability on occasion. While media and social networking services may help mitigate these emergencies, information is lacking about their actual contribution in times of physician absenteeism. On December 30, 2016, the director and sole physician of Takano Hospital in Fukushima, Japan, died. The physician’s passing placed many hospitalized patients in danger. This sudden case of physician unavailability, named the Takano Hospital Crisis, provoked massive attention from the general public, in the media and on social media networks such as Twitter. OBJECTIVE The aim of this study was to analyze newspaper articles, tweets and Twitter accounts relating to Takano Hospital Crisis. METHODS Newspaper articles and tweets were searched for keywords associated with Takano Hospital Crisis and its former director between October 2016 and June 2017. We first evaluated the chronological change in the number of articles and tweets, and the number of characters and relevant keywords in the articles. Then tweets and influencers who were popular on the Twitter platform from December 30, 2016 to February 28, 2017, were categorized. RESULTS We assessed 151 newspaper articles and 67,006 tweets. The results show that number of newspaper articles and tweets steeply increased and then diminished within the first month of the incident. The median number of characters in newspapers articles was 436 and the most frequent keyword was medical doctor. There were 753 original tweets that were retweeted more than four times from December 30, 2016 to February 28, 2017. Of these, 245 (32.5%) expressed concern. Notable influencers were journalists, news media outlets, and healthcare professionals that helped with fund raising and providing clinical service in the hospital. CONCLUSIONS Twitter could temporarily function in cases of sudden physician absenteeism to attract volunteers and funding, however, this would not be a long-term solution. In a more general context, a long-term effort of supports from the hospitals themselves and the government will be required to manage the persistent state of physician absenteeism.

In recent disaster situations, social media platforms, such as Twitter, played a major role in information sharing and widespread communication. These situations require efficient information sharing, therefore, it is important to understand the trends in popular topics and the underlying dynamics of information flow on social media better. Developing new methods to help us in these situations, and testing their effectiveness so that they can be used in future disasters is an important research problem. In this study, we proposed a new model, &ldquo, topic jerk detector.&rdquo, This model is ideal for identifying topic bursts. The main advantage of this method is that it is better fitted to sudden bursts, and accurately detects the timing of the bursts of topics compared to the existing method, topic dynamics. Our model helps capture important topics that have rapidly risen to the top of the agenda in respect of time in the study of specific social issues. It is also useful to track the transition of topics more effectively and to monitor tweets related to specific events, such as disasters. We attempted three experiments that verified its effectiveness. First, we presented a case study applied to the tweet dataset related to the Fukushima disaster to show the outcomes of the proposed method. Next, we performed a comparison experiment with the existing method. We showed that the proposed method is better fitted to sudden burst accurately detects the timing of the bursts of the topic. Finally, we received expert feedback on the validity of the results and the practicality of the methodology.

The measurement of the ground state hyperfine structure of muonic helium has the potential to improve the precision of the mass of the negative muon by a factor of 50 or more. The mass of the negative muon is very important because it enables us to test the CPT theorem by comparison with positive muon mass. We aim to measure the hyperfine structure of muonic helium with a precision 1000 times higher than previous experiments [1,2] using the highintensity muon beam at J-PARC and have already obtained results better than the current precision in zero-field measurements in a test experiment in March 2021. To further improve the precision, we plan to measure in a high magnetic field and incorporate a technique that can produce highly polarized muonic helium atom [3]. In this paper, we will report on these developments.

Social media has been extensively and effectively deployed to share information and communicate during emergencies, such as the 2011 Fukushima Daiichi nuclear power plant accident in Japan. It is important to provide information during crises on social media and find the most effective way to transmit information in such situations. It is necessary to carefully preprocess Twitter data because it includes a considerable amount of noise. However, compared to other resources, such as government statistics and newspapers, Twitter provides varied information and is distinguished by its immediacy. We can also regard Twitter data as data that reflect human behaviors, thoughts, and intentions across different domains by characteristics of the platform. We propose an expansion model of Topic Dynamics for tracking the trend and detecting the moments of the occurrences of influential tweets on the Fukushima disaster. Using this method, we obtained the list of bursting words at different periods over a long duration following the Fukushima disaster.

Muonium is one of the best probes for the test of the bound-state QED, owing to the absence of the effect from the internal structure of nucleons. The recent establishment of intense pulsed muon beams at Japan Proton Accelerator Research Complex (J-PARC) paves the way to improved measurement of the muonium ground-state hyperfine structure (MuHFS). The measurement of MuHFS also determines the muon magnetic moment precisely, which is an important input parameter for the measurements of muon g-2, which is known for the 3-sigma discrepancy between the experiment and the theory. Muonium Spectroscopy Experiment Using Microwave (MuSEUM) collaboration aims to improve the precursor MuHFS experiment by a factor of ten. We present the status of the project and the prospect.

In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning- Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected.

Our group “ASACUSA MUSASHI” has established an efficient way for accumulating antiprotons and extracting them as intense ultra-slow mono-energetic beams at the CERN-AD facility. This novel beam opens new frontiers for investigating a variety of physics. For realizing H spectroscopy and the test for charge-parity-time symmetry, we have also developed the cusp trap, a combination of an anti-Helmholz superconducting coil and a multi-ring electrode trap, for trapping both antiprotons and positrons and then synthesizing antihydrogens. Recently, the cusp trap was practically used to accumulate antiprotons. The last piece for synthesizing antihydrogens in the cusp trap is the positron accumulator. We have developed a compact system to effectively accumulate positrons based on N2 gas-buffer scheme with a specially designed high precision cylindrical multi-ring electrode trap. The recent progress of the developing work is an important milestone for upcoming antihydrogen science of ASACUSA MUSASHI.

The antiproton is a unique projectile in the study of atomic collision physics. With an aim to produce an antiproton beam at atomic-physics energies for ‘pure’ collision experiments, we have so far developed techniques to decelerate, cool and confine antiprotons in vacuo. Our recent success in stable extraction of the beam has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. We have prepared a powerful supersonic helium gas jet to be crossed with the antiproton beam. The reaction rate is of the order of 10 − 4, and rigorous identification of particles is required for reduction of huge background counts. The reaction events are recognized by an electron signal followed by antiproton annihilation with an appropriate interval in the time of flight. Our design and strategy of the experiment are presented.

Hiroyuki A. Torii1 on behalf of MuSEUM Collaboration∗. H. A. Torii1, M. Aoki2, Y. Fukao3, Y. Higashi1, T. Higuchi1, H. Iinuma3, Y. Ikedo3, K. Ishida4, M. Iwasaki4, R. Kadono3, O. Kamigaito4, S. Kanda5, D. Kawall6, N. Kawamura3, A. Koda3, K. M. Kojima3, K. Kubo7, Y. Matsuda1, T. Mibe3, Y. Miyake3, T. Mizutani1, K. Nagamine4, K. Nishiyama3, T. Ogitsu3, R. Okubo3, N. Saito3, K. Sasaki3, K. Shimomura3, P. Strasser3, M. Sugano3, M. Tajima1, K. S. Tanaka1,4 D. Tomono4†, E. Torikai8, A. Toyoda3, K. Ueno3, Y. Ueno1, A. Yamamoto3, and M. Yoshida3. 1Graduate School of Arts and Sciences, University of Tokyo; 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan 2Osaka University; Toyonaka, Osaka 560-0043, Japan 3KEK; 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan 4RIKEN; 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 5Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 6University of Massachusetts Amherst; MA 01003-9337, USA 7International Christian University (ICU); Mitaka, Tokyo 181-8585, Japan 8University of Yamanashi; Kofu, Yamanashi 400-8511, Japan †Current affiliation: Kyoto University; Kyoto 606-8501, Japan ∗The collaboration name MuSEUM stands for “Muonium Spectroscopy Experiment Using Microwave.” E-mail: torii@radphys4.c.u-tokyo.ac.jp

Antiprotons produced by a proton synchrotron are decelerated and cooled first to 5.3 MeV by stochastic cooling and electron cooling in the Antiproton Decelerator (AD) ring, then to 111 keV by a Radio Frequency Quadrupole Decelerator (RFQD). After the deceleration of the RFQD, antiprotons are degraded by thin PET foils and injected into the Multi-Ring electrode Trap(MRT). Electrons are preloaded in the MRT to cool the antiprotons to subelectron volt energy region. Ramping up the trapping potential slowly allows ultra-slow antiprotons of 10-500eV to be extracted from the strong magnetic field region. Positrons from 22Na are cooled by N2 gas or by electrons to form a cold positron plasma. A rotating electric field is used to radially compress the plasma.

We have observed photons in the visible light range emitted from slow (2.0 keV/amu) highly charged Ar6+ ions which have captured one electron and transmitted through a Ni microcapillary target. Observed lines were identified by comparing with an ab initio calculation based on the multi-configuration Hartree-Fock method. (C) 2003 Elsevier Science B.V. All rights reserved.

To detect weak X-rays with a high-resolution spectrometer, a charge-coupled device was operated in a single X-ray photon detection mode. A procedure to effectively identify single X-ray was established. In the case of 2.3 keV/u N7+ and Ne9+ incidence, X-rays emitted from ions transmitted through a Ni microcapillary target were measured with the spectrometer using the procedure of the single event mode. The signal-to-noise ratio was improved by using the single photon counting method.

Proton sputtering from H-terminated Si(1 0 0) surfaces bombarded with Xeq+ (q=4–12, E=2–5 keV) were experimentally studied. Proton sputtering yields and two-dimensional (2D) distribution of protons were measured employing a time-of-flight technique with a 2D position sensitive detector. It was found that the q dependence of the proton sputtering yield from Si(1 0 0)–(2×1)H surface with Xeq+ was the same (∼q5) as that from an untreated surface, although the absolute yield was about 1/30. The yield from Si(1 0 0)–(1×1)H surface was about 10 times larger than that from the Si(1 0 0)–(2×1)H surface. The mean energy of emitted protons from Si(1 0 0)–(2×1)H and Si(1 0 0)–(1×1)H surfaces were 1.2 and 5.9 eV, respectively.

The frequency shift of the center-of-mass oscillation, known as the (1,0) mode, of a trapped electron plasma and, furthermore, its time evolution were observed during the cooling of an injected antiproton beam for the first time. Here, antiprotons mixed with the electrons did not follow faster electron oscillations but contributed to the modification of the effective potential. The time evolution of the plasma temperature, deduced from the frequency shift of the excited (3,0) mode, suggested that there was an abnormal energy deposition of the antiproton beam in the electron plasma before thermalization.

Antihydrogen, a positron bound to an antiproton, is the simplest antiatom. Its counterpart—hydrogen—is one of the most precisely investigated and best understood systems in physics research. High-resolution comparisons of both systems provide sensitive tests of CPT symmetry, which is the most fundamental symmetry in the Standard Model of elementary particle physics. Any measured difference would point to CPT violation and thus to new physics. Here we report the development of an antihydrogen source using a cusp trap for in-flight spectroscopy. A total of 80 antihydrogen atoms are unambiguously detected 2.7 m downstream of the production region, where perturbing residual magnetic fields are small. This is a major step towards precision spectroscopy of the ground-state hyperfine splitting of antihydrogen using Rabi-like beam spectroscopy., Comparing hydrogen and antihydrogen—its antimatter counterpart—provides important tests of fundamental symmetries in the Standard Model. Kuroda et al. present a source of antihydrogen atoms that may provide high-precision in-flight measurements of their ground-state hyperfine splitting.

We have performed laser spectroscpy of metastable antiprotonic helium atoms (or “atomcules”) ( p He + ) and have observed a density dependence of the resonance vacuum wavelengths for the known transitions (n, l) = (39,35) → (38,34) and (37,34) → (36,33). They showed linear red-shifts of 0.61 ± 0.01 GHz and 0.22 ± 0.02 GHz per 1 g/l, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits, yielding λ0 = 597.2570 ± 0.0003 nm and λ0 = 470.7220 ± 0.0006 nm, respectively. These values were compared with the result of recent theoretical calculations on the energy of the Coulombic three-body system. including relativistic corrections and the Lamb shift. The agreements between our experimental values and the calculations have become as good as 2 × 10−6. This sets a severe constraint on the antiproton charge (−Q p ) and mass (M p ) that |Q p −Q p |/e −7 |M p −M p /M p × 5 × 10 −7 , under a more precisely known constraint on the charge-to-mass ratio. Thus we have opened a new possibility of measuring fundamental constants of the antiproton.

We have performed laser spectroscpy of metastable antiprotonic helium atoms (or “atomcules”) (\({\bar p}\)He+) and have observed a density dependence of the resonance vacuum wavelengths for the known transitions (n,l)=(39,35)→(38,34) and (37,34)→(36,33). They showed linear red-shifts of 0.61±0.01 GHz and 0.22±0.02 GHz per 1 g℞, respectively. With the shift parameters above, the transition vacuum wavelengths were extrapolated to zero-density limits, yielding λ0 = 597.2570± 0.0003 nm and λ0 = 470.7220±0.0006 nm, respectively. These values were compared with the result of recent theoretical calculations on the energy of the Coulombic three-body system, including relativistic corrections and the Lamb shift. The agreements between our experimental values and the calculations have become as good as 2×10-6. This sets a severe constraint on the antiproton charge (\(- Q_{\bar p} \)) and mass (\(M_{\bar p} \)) with |Q p - \(Q_{\bar p} \)|/e < 5 × 10-7 and |M p - \(M_{\bar p} \)|/M p < 5 × 10-7, under a more precisely known constraint on the charge-to-mass ratio. Thus we have opened a new possibility of measuring fundamental constants of the antiproton.

Recently, the production of low energy anti-hydrogen atoms in the cusp trap with the use of 150eV antiproton beams from the MUSASHI trap was reported. The purpose of producing low energy anti-hydrogen atoms in a cusped magnetic field is to extract a polarized anti-hydrogen beam to a field free region, so that the hyperfine structure of anti-hydrogen atoms can be measured.

Department of Physics, Tokyo University of Science, Shinjuku, Tokyo 168-8601, Japan(Received 13 July 2011; published 17 February 2012)TheASACUSA collaborationdeveloped an ultraslowantiproton beam source, monoenergetic ultraslowantiproton source for high-precision investigation (MUSASHI), consistingof an electromagnetic trapwitha liquid He free superconducting solenoid and a low energy antiproton beam transport line. TheMUSASHI was capable of trapping and cooling more than 1 10

We report here the first successful synthesis of cold antihydrogen atoms employing a cusp trap, which consists of a superconducting anti-Helmholtz coil and a stack of multiple ring electrodes. This success opens a new path to make a stringent test of the CPT symmetry via high precision microwave spectroscopy of ground-state hyperfine transitions of antihydrogen atoms.

We report here the radial compression of a large number of antiprotons ($\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{5}$) in a strong magnetic field under ultrahigh vacuum conditions by applying a rotating electric field. Compression without any resonant structures was demonstrated for a range of frequencies from the sideband frequency of 200 kHz to more than 1000 kHz. The radial compression achieved is a key technique for synthesizing and manipulating antihydrogen atoms and antiprotonic atoms.

Antiprotonic helium is a unique atomic three-body system which is a mixture of particles and an antiparticle and yet shows metastability with lifetimes of a few microseconds before annihilation of the constituent antiproton. Using the antiprotons provided from the Antiproton Decelerator facility at CERN, Geneva, we the ASACUSA collaboration (standing for Atomic Spectroscopy And Collisions Using Slow Antiprotons) has been pursuing high precision in laser spectroscopy of this exotic atom, to test CPT invariance between matter and antimatter. Recently, we have measured 12 different transition frequencies with fractional precisions in the order of a ppb. A femtosecond optical frequency comb has found application here in measurement of absolute frequencies of a continuous-wave pulse-amplified laser light ranging from blue to infrared. Comparison with three-body QED calculations yielded an antiproton-to-electron mass ratio and antiproton-to-proton mass ratio with a precision of a few ppb, contributing to the precise determination of the fundamental constant and to the test of CPT. As a pioneering work of atomic physics with low-energy antiprotons, we have developed techniques of electromagnetic trapping of antiprotons in ultra-high vacuum and produced ultra-slow antiproton beams at energies ranging from 10 eV to 20 keV. (Note the great orders of magnitude of deceleration and cooling from the GeV energies at which antiprotons are produced at accelerator facilities.) This unique beam is used for our research on atomic collision dynamics between an antiproton and an ordinary atom, and also for future production and microwave spectroscopy of cold antihydrogen atoms.

The development of techniques to decelerate, cool and confine antiprotons in vacuo with an electromagnetic trap has opened a new research field of atomic physics of 'cold' antiprotons, including synthesis of antihydrogen atoms. At the Antiproton Decelerator (AD) facility at CERN, we the MUSASHI group of ASACUSA collaboration have so far achieved efficient confinement of millions of antiprotons in a Multi-Ring electrode Trap (MRT) installed in a superconducting magnet of 2.5 T, by a sequential combination of the AD (down to 5.3 MeV), an RFQD (Radio-Frequency Quadrupole Decelerator; down to 50–120 keV) and the MRT. Antiprotons, cooled to energies less than an electronvolt by preloaded electrons in the trap, was then extracted out of the magnetic field and transported along a 3-m beamline as a monoenergetic beam of 10–500 eV. With this unique ultra-low-energy antiproton beam, we are now planning the first atomic collision experiments under single collision conditions, to measure ionization and atomic capture cross sections of antiprotons against helium atoms. A supersonic atomic gas-jet target is prepared and crossed with the antiproton beam. Antiprotons as well as electrons emitted during the reaction will be detected by a microchannel plate (MCP) while the antiproton annihilation will be recognized by detection of annihilation products—mostly pions—by surrounding scintillation counters. When the antiproton is captured, it forms a neutral antiprotonic helium atom, some in a metastable state whose level structures have been well studied with spectroscopic methods. Severe identification of particles and atoms plays an essential role in the design of the experiment, to distinguish the small number of reaction events out of a huge pile of background events. Our strategies for our near-future experiments are discussed.

The Trap group of ASACUSA collaboration has decelerated and confined millions of cooled antiprotons in an electromagnetic trap, 50 times more efficiently than conventional methods. They were then extracted out of the magnetic field of 2.5 T and transported at 10–500 eV. This unique ultra‐slow antiproton beam from our apparatus named MUSASHI is expected to open up a new field of atomic and nuclear physics.

This paper describes measurements of the hyperfine structure of two antiprotonic atoms that are planned at the Antiproton Decelerator (AD) at CERN. The first part deals with antiprotonic helium, a three-body system of alpha-particle, antiproton and electron that was previously studied at LEAR. A measurement will test existing three-body calculations and may - through comparison with these theories - determine the magnetic moment of the antiproton more precisely than currently available, thus providing a test of CPT invariance. The second system, antihydrogen, consisting of an antiproton and a positron, is planned to be produced at thermal energies at the AD. A measurement of the ground-state hyperfine splitting, which for hydrogen is one of the most accurately measured physical quantities, will directly yield a precise value for the magnetic moment of the antiproton, and also compare the internal structure of proton and antiproton through the contribution of the magnetic size of the antiproton to the ground state hyperfine splitting., Comment: Proceedings of the Hydrogen II workshop, Castiglione della Pescaia, June 1 --3, 2000, 15 pages, 8 figures

Laser is a powerful tool for precise spectroscopy and has been used in many different fields of physics. In this paper we present interesting and important examples of laser spectroscopy applied in the field of atomic physics involving an exotic particle `antiproton'. We have performed laser spectroscopy of metastable antiprotonic helium atoms (or atom-molecules) (pHe+) and have observed a density dependence of the resonance vacuum wavelengths for the known transitions (n,1) equals *(39,35) yields (38,34) and (37,34) yields (36,33).© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Antiproton, the antiparticle of proton, is a unique projectile in the study of atomic collision physics, which can be treated theoretically either as a 'negative proton' or a 'heavy electron'. Atomic capture of an antiproton will result in formation of a highly excited exotic atom. Antiprotonic helium atom has been studied intensively by means of precision laser spectroscopy, which has led to a stringent determination of antiproton mass and charge to a level of ppb. Comparison of these values with those of proton gives one of the best tests of CPT invariance, the most fundamental symmetry in physics. However, the dynamic processes of antiproton capture remain unclarified. With an aim to produce an antiproton beam at atomic-physics energies for 'pure' collision experiments, we have so far developed techniques to decelerate, cool and confine antiprotons in vacuo, using a sequential combination of the Antiproton Decelerator (AD) at CERN, a Radio-Frequency Quadrupole Decelerator (RFQD), and an electromagnetic trap. Our recent success in stable extraction of monoenergetic ultra-slow antiprotons, about 3 × 10 5 in number available every 5 minutes, has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom under the single collision condition. Our design and strategy of the cross-beam experiments are presented, together with technical challenges in the detection system to identify the rare events with a reaction rate of 10 −4 .