Jian-zhi Ruan

A new scintillation material: Pure CsI with 10 ns decay time

Abstract The properties of pure CsI have been studied with respect to its application as a scintillation material.

A new type of luminescence mechanism in large band-gap insulators: Proposal for fast scintillation materials

Abstract Luminescence components of BaF 2 (180–230 nm), CsF (220–500 nm), CsCl (200–300 nm), CsBr (220–280 nm), and RbF (200–450 nm) have been investigated at room temperature by using synchrotron radiation as a light source. These luminescence components have excitation thresholds at the energy differences from the outermost Ba 2+ 5p, or M + m p ( m = 4 and 5 for M = Rb and Cs, respectively) core state to the conduction band, and are attributeted to the radiative decay of electrons in the X − n p halogen valence bands ( n = 2, 3, and 4 for X = F, Cl and Br, respectively) to the outermost-core hole states. Single bunch operation of synchrotron radiation has been used to determine the lifetime of the above luminescence. The measured lifetimes in ns are: BaF 2 : 0.88±0.02; CsF: 2.9±0.1; CsCl: 0.88±0.07; CsBr: 0.07±0.03; and RbF: 1.3±0.1 From the above results, it is proposed that insulators having large band-gap energy compared to the energy difference between the valence band and the outermost-core state are candidates for fast scintillation materials, for example, CsCl, CsBr, RbF, KF, BaCl 2 , BaBr 2 , and BaI 2 .

Liquid and solid argon, krypton and xenon scintillators

Abstract The time dependence of uv emission in liquid and solid argon, krypton and xenon excited by 207Bi internal conversion electrons and alpha particles has been investigated. Decay curves in the solid are similar to those for the liquid. For the case of solid or liquid xenon excited by electrons, a drastic decrease in a slow component was observed with an applied electric field of about 1 kV/cm. Variation of scintillation decay in liquid argon or xenon excited by electrons and by alpha particles has been observed. The relative intensities of the fast component increase with increasing ionization density, which is contrary to the effect in organic scintillators. The ratios (Lα/Eα)/(Le/Ee) of the intensity per unit energy excited by alpha particles to that by electrons are 1.08, 1.02 and 1.15 for liquid argon, krypton and xenon, respectively. The decay curves for xenon, nitrogen or carbon dioxide doped liquid argon scintillators have been investigated.

Emission spectra from ArXe, ArKr, ArN2, ArCH4, ArCO2 and XeN2 gas scintillation proportional counters

Abstract Emission spectra from gas scintillation proportional counters have been measured from the wavelength region of 110–650 nm for the gas mixtures mentioned in the title for argon or xenon pressures of about 760 Torr. The spectra showed a second continuum emission with fwhm of about 10 nm at wavelengths of 128 nm for argon, 148 nm for krypton and 171 nm for xenon. The second continuum spectrum from Ar2∗ was almost quenched with an addition of Kr(0.2 Torr), Xe(0.1 Torr), N2(10 Torr), CH4(1 Torr), or CO2(0.1 Torr). Emission resulting in energy transfer from Ar2∗ and/or Ar∗ states is observed mainly in the wavelength region of 145–190 nm for Xe-admixture, 125–155 nm for Kr-admixture and 330–370 nm for N2 admixture. No photons are observed in the visible wavelength region for ArCH4, ArCH4 and XeN2 gas mixtures.

Search for Weak Gamma-Rays of 47V

The decay of 47 V has been investigated by using a two-directional focusing beta-ray spectrometer and NaI scintillators (2 in. 3 mm thickness). Two weak gamma-rays of 1.54 and 1.87 MeV have been found and their intensities are 1.4 and 0.9 percent of the positron decay, respectively. The upper limit for 0.16 MeV gamm-ray is 0.08 percent of the positron decay. The maximum energy of the positrons from 47 V is 1.90±0.04 MeV.

Time dependence of the recombination luminescence from high-pressure argon, krypton and xenon excited by alpha particles

Abstract The time dependence of the luminescence due to the recombination process of electrons and ions in high-pressure argon, krypton and xenon excited by 210Po alpha-particles has been studied by considering the difference in the decay curves observed at zero field and at such a high field that all electrons are free from recombination. For argon of pressure p × 103 Torr, the decay is well represented by the formula e−t/τ − e2t/Tr for t Tr, Where T r = 6 × 10 4 p −2.7±0.3 s , τ ≊ 3 μ s , and p is in Torr. For krypton 4 × 103 300 ns, where Tr = 104p−2.6±0.5 s. For xenon 4 × 103 t0, where typical Tr and t0 values are 2.0 μs and 1.6 μs, respectively, for 1.5 × 104 Torr, and 5.6 μs and 5 μs for 4.4 × 103 Torr. It is shown that the Coulomb interaction between the thermalized electrons and the ions in the track is strong enough to prevent electron diffusion, which results in the ambipolar diffusion. A bried consideration is given on the track structure relevant to the recombination luminescence.

Liquid and solid argon, and nitrogen-doped liquid and solid argon scintillators

Abstract The scintillation decay of nitrogen-doped liquid and solid argon excited by 207Bi internal conversion electrons has been studied by a single-photon counting technique. Two exponential decays are observed for [N2] Ar 2 ★ ( 3 Σ u + ) → 2 Ar + hν( uv ) and Ar 2 ★ ( 3 Σ u + ) → 2 Ar + hν( uv ) . The Ar 2 ★ ( 3 Σ u + ) state are quenched by doped nitrogen in liquid argon but not in the solid phase for [N2]

Precision measurements of gamma-ray intensities IV. Low energy region: 75Se and 133Ba

Abstract Relative intensities of gamma rays were measured in Hiroshima and Nagoya in the region of 122–356 keV. Two Ge(Li) detectors were calibrated with four kinds of standard sources and a cascade gamma-ray source. The disintegration rates of the standard sources were determined by means of the coincidence method. Relative intensities of 75 Se and 133 Ba were obtained with estimated errors less than 1% for strong gamma rays. Gamma-ray intensities per decay were also extracted.

Response of BaF2, BaF2-plastic, and BGO scintillators to neutrons with energies between 15 and 45 MeV

The response of BaF2, BaF2-plastics (BPS), and BGO scintillators to neutrons was studied in the energy range En = 15 to 45 MeV. The detection efficiencies of the BaF2 and BGO scintillators become large with increasing neutron energy, whereas the one of the0 BPS shows a weak energy dependence. Around En = 45 MeV, these scintillators have about the same efficiencies (per unit thickness) as that of the NE213 liquid scintillator.

The new scintillation material CsI and its application to position sensitive detectors

Abstract The new scintillation material CsI has been investigated for a position sensitive detector which is used together with CsI(Tl) coupled to a common PMT. Spatial resolution has been achieved with a simple pulse shape discriminator. Combinations of CsIBGOCsI(T1) and CsIBaF 2 CsI(T1) are also shown to be useful as position sensitive detectors.