The use of nuclear emulsions to record tracks of charged particles with an accuracy of better than 1 micron is possible in large physics experiments thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated microscopes.
The European Scanning System (ESS) is a fast automatic system developed for the mass scanning of the emulsions of the OPERA experiment, which requires microscopes with scanning speeds of about 20 cm$^2$/h. Recent improvements in the technique and measurements with ESS are reported.
The use of nuclear emulsions in very large physics experiments is now possible thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated microscopes. In this paper the hardware performances of the European Scanning System (ESS) are described. The ESS is a very fast automatic system developed for the mass scanning of the emulsions of the OPERA experiment, which requires microscopes with scanning speeds of about 20 cm^2/h in an emulsion volume of 44 micron thickness.
Automatic nuclear emulsion readout systems have seen remarkable progress since the original idea was developed almost 40 years ago. After the success of its full application to a large-scale neutrino experiment, OPERA, a much faster readout system, the hyper-track selector (HTS), has been developed. HTS, which has an extremely wide-field objective lens, reached a scanning speed of 4700 cm$^2$/h, which is nearly 100 times faster than the previous system and therefore strongly promotes many new experimental projects. We will describe the concept, specifications, system structure, and achieved pe…
This paper describes the recent development of a novel automatic computer-controlled manipulator for emulsion film placement and removal at the microscope object table (also called stage). The manipulator is designed for mass scanning of emulsion films for the OPERA neutrino oscillation experiment and provides emulsion changing time shorter than 30 seconds with an emulsion film positioning accuracy as good as 20 microns RMS.
Nuclear emulsion, a tracking detector with sub-micron position resolution, has played a successful role in the field of particle physics and the analysis speed has been substantially improved by the development of automated scanning systems. This paper describes a newly developed automated scanning system and its application to the analysis of nuclear fragments emitted almost isotropically in nuclear evaporation. This system is able to recognize tracks of nuclear fragments up to |tanθ|< 3.0 (where θ is the track angle with respect to the perpendicular to the emulsion film), while existing syst…
The possibility of a three-dimensional visualisation/reconstruction of tracks in nuclear emulsion films using X-ray imaging is described in this paper. The feasibility of the technique is established with experimental results.
The OPERA neutrino oscillation experiment is based on the use of the Emulsion Cloud Chamber (ECC). In the OPERA ECC, nuclear emulsion films acting as very high precision tracking detectors are interleaved with lead plates providing a massive target for neutrino interactions. We report on studies related to the effects occurring from the contact between emulsion and lead. A low radioactivity lead is required in order to minimize the number of background tracks in emulsions and to achieve the required performance in the reconstruction of neutrino events. It was observed that adding other chemica…
New methods for efficient and unambiguous interconnection between electronic counters and target units based on nuclear photographic emulsion films have been developed. The application to the OPERA experiment, that aims at detecting oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is reported in this paper. In order to reduce background due to latent tracks collected before installation in the detector, on-site large-scale treatments of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd) packages, each made of a doublet of emulsion films, have bee…
The OPERA experiment, designed to conclusively prove the existence of $\rm ν_μ\to ν_τ$ oscillations in the atmospheric sector, makes use of a massive lead-nuclear emulsion target to observe the appearance of $\rm ν_τ$'s in the CNGS $\rm ν_μ$ beam. The location and analysis of the neutrino interactions in quasi real-time required the development of fast computer-controlled microscopes able to reconstruct particle tracks with sub-micron precision and high efficiency at a speed of 20 cm^2 / h. This paper describes the performance in particle track reconstruction of the European Scanning System, a…
We propose an innovative method for proton radiography based on nuclear emulsion film detectors, a technique in which images are obtained by measuring the position and the residual range of protons passing through the patient's body. For this purpose, nuclear emulsion films interleaved with tissue equivalent absorbers can be used to reconstruct proton tracks with very high accuracy. This is performed through a fully automated scanning procedure employing optical microscopy, routinely used in neutrino physics experiments. Proton radiography can be used in proton therapy to obtain direct informa…
Proton therapy is nowadays becoming a wide spread clinical practice in cancer therapy and sophisticated treatment planning systems are routinely used to exploit at best the ballistic properties of charged particles. The information on the quality of the beams and the range of the protons is a key issue for the optimization of the treatment. For this purpose, proton radiography can be used in proton therapy to obtain direct information on the range of the protons, on the average density of the tissues for treatment planning optimization and to perform imaging with negligible dose to the patient…
We previously developed an automatic track scanning system which enables the detection of large-angle nuclear fragments in the nuclear emulsion films of the OPERA experiment. As a next step, we have investigated this system's track recognition capability for large-angle minimum ionizing particles $(1.0 \leq |tan θ| \leq 3.5)$. This paper shows that, for such tracks, the system has a detection efficiency of 95$\%$ or higher and reports the achieved angular accuracy of the automatically recognized tracks. This technology is of general purpose and will likely contribute not only to various analys…
A nuclear emulsion film is a three-dimensional tracking device that is widely used in cosmic-ray and high energy physics experiments. Scanning with a wide angle acceptance is crucial for obtaining track information in emulsion films. This study presents a new method developed for wide angle acceptance and high-speed track recognition of nuclear emulsion films for neutrino-nucleus interaction measurements. The nuclear emulsion technique can be used to measure tracks of charged particles from neutrino interactions with a low momentum threshold. The detection of the particles with a wide angle ac…
A new method of momentum measurement of charged particles through Multiple Coulomb Scattering (MCS) in the OPERA lead emulsion target is presented. It is based on precise measurements of track angular deviations performed thanks to the very high resolution of nuclear emulsions. The algorithm has been tested with Monte Carlo (MC) pions. The results are found to describe within the expected uncertainties the data obtained from test beams. We also report a comparison of muon momenta evaluated through MCS in the OPERA lead emulsion target with those determined by the electronic detectors for neutr…
The OPERA experiment aims at measuring the ν_μ -> ν_τ oscillation through the ν_τ appearance in an almost pure ν_μ beam (CNGS). For the direct identification of the short-lived τ lepton, produced in ν_τ CC interactions, a micrometric detection resolution is needed. Therefore the OPERA detector makes use of nuclear emulsion films, the highest spatial resolution tracking device, combined with lead plates in an emulsion cloud chamber (ECC) structure called 'brick'. In this paper the nuclear emulsion analysis chain is reported; the strategy and the algorithms set up will be described together with…
The use of emulsions as particles detector has a long and successful life. The recent development of fast automatized analysis systems has allowed the use of huge amount of emulsions films with no precedence in the history of particle physics. The OPERA experiment, running in the underground Laboratori Nazionali del Gran Sasso (LNGS), for the confirmation of the neutrino oscillation in the $ν_μ\toν_{tau}$ channel, is "the major" of these experiments. The experimental technique, the strategy and the first results of the experiment are presented.
We propose to build and operate a detector based on the emulsion film technology for the measurement of the gravitational acceleration on antimatter, to be performed by the AEgIS experiment (AD6) at CERN. The goal of AEgIS is to test the weak equivalence principle with a precision of 1% on the gravitational acceleration g by measuring the vertical position of the anni- hilation vertex of antihydrogen atoms after their free fall in a horizontal vacuum pipe. With the emulsion technology developed at the University of Bern we propose to improve the performance of AEgIS by exploiting the superior …
Precise neutrino--nucleus interaction measurements in the sub-multi GeV region are important to reduce the systematic uncertainty in future neutrino oscillation experiments. Furthermore, the excess of ${ν_e}$ interactions, as a possible interpretation of the existence of a sterile neutrino has been observed in such an energy region. The nuclear emulsion technique can measure all the final state particles with low energy threshold for a variety of targets (Fe, C, H${_2}$O, and so on). Its sub-$μ$m position resolution allows measurements of the ${ν_e}$ cross-section with good electron/gamma sepa…
The measurement of environmental neutrons is particularly important in the search for new physics, such as dark matter particles, because neutrons constitute an often-irreducible background source. The measurement of the neutron energy spectra in the sub-MeV scale is technically difficult because it requires a very good energy resolution and a very high $γ$-ray rejection power. In this study, we used a super-fine-grained nuclear emulsion, called Nano Imaging Tracker (NIT), as a neutron detector. The main target of neutrons is the hydrogen (proton) content of emulsion films. Through a topologic…
The existence of the coherent neutrino-nucleus scattering reaction requires to evaluate, for any detector devoted to WIMP searches, the irreducible background due to conventional neutrino sources and at same time, it gives a unique chance to reveal supernova neutrinos. We report here a detailed study concerning a new directional detector, based on the nuclear emulsion technology. A Likelihood Ratio test shows that, in the first years of operations and with a detector mass of several tens of tons, the observation of the supernova signal can be achieved. The determination of the distance of the …
The OPERA experiment was designed to observe ${ν_μ}$ ${\rightarrow}$ ${ν_τ}$ oscillations through ${ν_τ}$ appearance at a baseline of 730 km in the CNGS beam. Newly developed emulsion analysis technology allows to measure ${ν_e}$, ${ν_μ}$ and ${ν_τ}$ interactions with the largest emulsion detector ever made. OPERA has detected five ${ν_τ}$ candidates, allowing to reject the background-only hypothesis at 5.1 $σ$. The parameters for standard and non-standard oscillations are measured and constrained.
We present the design and calibration measurements of a scanning tunneling microscope setup in a 3He ultrahigh-vacuum cryostat operating at 400 mK with a hold time of 10 days. With 2.70 m in height and 4.70 m free space needed for assembly, the cryostat fits in a one-story lab building. The microscope features optical access, an xy table, in situ tip and sample exchange, and enough contacts to facilitate atomic force microscopy in tuning fork operation and simultaneous magneto-transport measurements on the sample. Hence, it enables scanning tunneling spectroscopy on microstructured samples whi…
We demonstrate a cryogenic scanned probe microscope (SPM) that has been modified to be controlled with a haptic device, such that the operator can `feel' the surface of a sample under investigation. This system allows for direct tactile sensation of the atoms in and on top of a crystal, and we simulate, by using different SPM modalities, a sensation that is representative of the relevant atomic forces controlling the SPM. In particular, we operate the microscope in modes of (1) conventional STM feedback, (2) energy-dependent electron density imaging, (3) q-plus AFM frequency and amplitude base…
A transimpedance amplifier has been designed for scanning tunneling microscopy (STM). The amplifier features low noise (limited by the Johnson noise of the 1 GΩ feedback resistor at low input current and low frequencies), sufficient bandwidth for most STM applications (50 kHz at 35 pF input capacitance), a large dynamic range (0.1 pA--50 nA without range switching), and a low input voltage offset. The amplifier is also suited for placing its first stage into the cryostat of a low-temperature STM, minimizing the input capacitance and reducing the Johnson noise of the feedback resistor. The ampl…
The OPERA experiment aims at the direct confirmation of the leading oscillation mechanism in the atmospheric sector looking for the appearance of $ν_τ$ in an almost pure $ν_μ$ beam (the CERN CNGS beam). In five years of physics run the experiment collected $17.97 \times 10^{19}$ p.o.t. The detection of $τ$s produced in $ν_τ$ CC interactions and of their decays is accomplished exploiting the high spatial resolution of nuclear emulsions. Furthermore OPERA has good capabilities in detecting electron neutrino interactions, setting limits on the $ν_μ \rightarrow ν_{e}$ oscillation channel. In this …
The Scanning Tunneling Microscope is a powerful tool for studying the electronic properties at the atomic level, however it's relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting on conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies.
We present the design and performance of a cryogenic scanning tunneling microscope (STM) which operates inside a water-cooled Bitter magnet, which can attain a magnetic field of up to 38 T. Due to the high vibration environment generated by the magnet cooling water, a uniquely designed STM and vibration damping system are required. The STM scan head is designed to be as compact and rigid as possible, to minimize the effect of vibrational noise as well as fit the size constraints of the Bitter magnet. The STM uses a differential screw mechanism for coarse tip - sample approach, and operates in …
We describe a scanning tunneling microscope (STM) that operates at magnetic fields up to 22 Tesla and temperatures down to 80 mK. We discuss the design of the STM head, with an improved coarse approach, the vibration isolation system, and efforts to improve the energy resolution using compact filters for multiple lines. We measure the superconducting gap and Josephson effect in Aluminum and show that we can resolve features in the density of states as small as 8\,$μ$eV. We measure the quantization of conductance in atomic size contacts and make atomic resolution and density of states images in…
We describe the construction and performance of a scanning tunneling microscope (STM) capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful the…
Material thermal properties characterization at nanoscales remains a challenge even if progresses were done in developing specific characterization techniques like the Scanning Thermal Microscopy (SThM). In the present work, we propose a detailed procedure based on the combined use of a SThM probe characterization and its Finite Element Modeling (FEM) to recover in-operando 3omega measurements achieved under high vacuum. This approach is based on a two-step methodology: (i) a fine description of the probe s electrical and frequency behaviors in out of contact mode to determine intrinsic parame…
We present a Scanning Hall Probe Microscope operating in ambient conditions. One of the unique features of this microscope is the use of the same stepper motors for both sample positioning as well as scanning, which makes it possible to have a large scan range (few mm) in x and y directions, with a scan resolution of 0.1 $μ$m. Protocols have been implemented to enable scanning at different heights from the sample surface. The z range is 35 mm. Microstructured Hall probes of size 1-5 $μ$m have been developed. A minimum probe-sample distance \textless{} 2 $μ$m has been obtained by the combinatio…
We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 uV, approaching low enough photon population (N~1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and …
The key to optimizing spatial resolution in a state-of-the-art scanning transmission electron microscope is the ability to precisely measure and correct for electron optical aberrations of the probe-forming lenses. Several diagnostic methods for aberration measurement and correction with maximum precision and accuracy have been proposed, albeit often at the cost of relatively long acquisition times. Here, we illustrate how artificial intelligence can be used to provide near-real-time diagnosis of aberrations from individual Ronchigrams. The demonstrated speed of aberration measurement is impor…
We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350mK and in magnetic fields up to 9T, with thin film deposition and in-situ cleaving capabilities. The main focus lies on the simple design of STM head allowing top loading of the sample and innovative sample holder design that allows us to get spectroscopic data on superconducting thin films grown in-situ on insulating substrates. Other design details on sample transport, chamber and vibration isolation scheme are also described. We demonstrate the capability of o…
