E. Conti

Measurement of the light yield of infrared scintillation in xenon gas

Abstract The infrared scintillation yield from gaseous xenon excited by an α source has been measured in the wavelenght range 0.7–1.6xa0μm. The infrared light yield has been found to be ≥2.1×104xa0ph/ MeV.

A first study of the infrared emission in argon excited by ionizing particles

Abstract We report on the study of infrared emission from gaseous argon excited by MeV protons in the wavelength range 0.7–1.8xa0μm. The dependence of the light yield on the applied electric field has been measured at different pressures. At zero field (prompt emission) the yield does not depend on pressure. When a field is applied the light emission increases linearly with the field strength above a critical value (drift emission) and a dependence from pressure is observed. Prompt and drift emission are consistent with transitions between the lowest atomic states of neutral argon. Drift emission is generated by electrons which gain energy from the electric field and excite atoms through collisions.

Argon purification in liquid phase

Abstract A new purification method for liquid argon has been developed. The electronic capture mechanism has been exploited, the electrons being generated by a strong gamma-ray source. High purity level and stability, comparable to those obtained with standard gaseous-phase procedures, have been reached.

Infrared scintillation in liquid Ar and Xe

Abstract Infrared emission induced by ionizing particle has been observed in liquid Ar and liquid Xe. The phenomenon seems to be similar to the one recently observed in dense noble gases.

Time behaviour of the scintillation light in mixtures of liquid argon and xenon

Abstract We have measured the time evolution of the scintillation light in mixtures of liquid argon and xenon at different concentrations of xenon. The xenon shifts the scintillation light wavelength from 125 to 175 nm, even at concentration as low as 114 ppm. The time shape of the light has been found to be dependent on the xenon concentration. At a few percent xenon concentration the decay time is some tens nanosecond long. The light shape is understandable assuming that the primary excitation is transferred from the Ar to the Xe atoms via both radiative and non-radiative (collisional) processes.

CsI(Tl) infrared scintillation light yield and spectrum

Abstract Infrared emission from CsI(Tl) excited by ∼70 keV electrons was detected with an InGaAs PIN photodiode. Some parameters of infrared scintillation were studied. The emission spectrum is located between 1.55 and 1.70 μm with a maximum at 1.60 μm . The light yield of infrared scintillation is (4.9±0.3)×10 3 photons / MeV . Infrared scintillation caused by 3 MeV α-particles is detected as well.

Performance of a liquid xenon time projection chamber for low-energy γ-rays detection

Abstract We detected the ionization charge and the scintillation light produced in liquid xenon by the interactions of γ-rays emitted by radioactive sources. We could distinguish the multiple interactions of the photons and, by using the prompt scintillation signal, determine the distance of the tracks from the anode. Applying an electric field of 0.4 kV/cm, we obtained an intrinsic energy resolution of (8.4 ± 0.9)% at 1 MeV and found that the free-ion yield is 4.24 ± 0.43 independent on the photon energy within few percent in the explored range between 500 keV and 2 MeV. The experimental spectra are the sum of the total energy peaks and the Compton continuum. By selecting the γ-rays with multiple interactions we could strongly reduce the Compton background and enhance the total energy peaks. All the spectra were consistent with a Monte Carlo simulation of the apparatus. With a sensitive volume of about 200 cm 3 we measured a peak-to-total ratio ranging from almost 100% (500–600 keV γ-rays) to more than 60% for 2 MeV photons.

Preliminary results on the feasibility of a liquid methane detector for fast neutrons

Abstract We have developed a purification system for methane which allows us to reach an electron attenuation length in the liquid > 1 m. With such a purity level, we carry out a systematic study of the electron drift velocity. Our results confirm the feasibility for a neutron liquid methane detector.

Electron multiplication in liquid argon on a tip array

Abstract We have carried out a systematic study of the electron multiplication in liquid argon on an array of 52 sharp tips. We found a multiplication factor for a single tip of at least 100 and a plateau region in the counting-rate vs tip-voltage curve of about 150 V. The results make us hopeful in exploiting such mechanism for a new kind of detectors.

New measurement of the π → μνγ decay

Abstract We have measured the branching ratio of the radiative decay π → μνγ . The energies of the gamma-ray and of the muon were both measured and the Dalitz-plot distribution of the decay was obtained. The data agree well with the theoretical prediction (QED internal bremsstrahlung) down to a γ-ray energy of 1 MeV. The discrepancy reported in a previous experiment is not confirmed.