Lars-Olov Norlin

Properties of the YAG:Ce scintillator

Abstract Light yield, light pulse shape due to γ-rays and α-particles, energy resolution and time resolution of the new YAG:Ce scintillator were studied using a light readout by means of the XP2020Q photomultiplier and the S3590-03 photodiode. The light yield of 20 300 ± 2000 photons/MeV was determined using three independent methods. The light pulse produced by γ-rays consists of two components with the decay time constants of 87.9 ns and 302 ns respectively. The light pulse measured for α-particles exhibits a faster and less intense fast component with the decay time constant of 68.4 ns. The energy resolution obtained was 11.1% and 11.7% for the 662 keV γ-rays from a 137 Cs source as measured with the photomultiplier and the photodiode readout, respectively. A time resolution of 1.3 ns was observed for 60 Co γ-rays (at 100 keV threshold) with the crystal coupled to the XP2020Q photomultiplier. The YAG:Ce scintillator with the peak emission at 550 nm is a good candidate to replace CsI(T1) and BGO scintillators in detection of light charged particles when photodiode readout is of importance. The observed difference in the light pulse shape due to γ-rays and α-particles suggests good performance of the crystal in the pulse shape discrimination method for the particle identification.

Advantages and limitations of LSO scintillator in nuclear physics experiments

Light yield, light pulse shape due to /spl gamma/-rays and /spl alpha/-particles, energy and time resolutions for three different samples of the LSO scintillator were studied using an XP2020Q photomultiplier and an S3590-03 photodiode. Light yields of 4200/spl plusmn/200 phe/MeV and 18500/spl plusmn/900 e-h pair/MeV were measured for the PM tube and the photodiode, respectively. The light pulse shape exhibits a pure exponential decay with a time constant of 47.2/spl plusmn/1.3 ns for both /spl gamma/-rays and /spl alpha/-particles. Energy resolutions of 10% and 14.6% for the 662 keV /spl gamma/-rays from a /sup 137/Cs source were obtained for the photomultiplier and the photodiode readout, respectively. A time resolution of 180 ns was observed for /sup 60/Co /spl gamma/-rays at 1 MeV threshold and 400 ps for 100 keV threshold. The study confirmed a number of advantages of the LSO scintillator for nuclear physics experiments, however, for small size samples. For larger volumes the natural radioactivity of the LSO, about 300 counts/s/cm/sup 3/, may limit possible applications. The high number of e-h pairs produced in the photodiodes makes LSO very attractive for small compact scintillation probes. >

Fabrication of an integrated ΔE-E-silicon detector by wafer bonding using cobalt disilicide

Abstract The problem concerning mechanical stability of thin self-supporting ΔE detector in a ΔE-E semiconductor detector telescope, has been solved by integrating both detectors into one unit. We show here a low-cost method to integrate the detectors by wafer bonding using cobalt disilicide. The ΔE-detector has a thickness of 6.5 μm and the E detector 290 μm with an area of 24.8 mm2. The system was characterized with secondary ion mass spectroscopy (SIMS), scanning electron microscopy (SEM), electrical measurement, particle measurement and two-dimensional electrical simulation.

Studies of scintillation light nonproportionality of ZnSe(Te), CsI(Tl) and YAP(Ce) crystals using heavy ions

The scintillation light yield for ZnSe(Te), CsI(Tl) and YAP(Ce) crystals have been studied with alpha particles, 12 C and 81 Br in the energy region 2.8–42.2 MeV. A nonproportional behavior was observed, mostly pronounced for alpha particles on YAP(Ce). The results are understood in terms of d-rays effect. r 2001 Elsevier Science B.V. All rights reserved. PACS: 29.40.Mc

Lifetimes of the metastable and levels in measured by laser probing of a stored ion beam

A laser probing method has been used in an ion storage ring to measure the lifetimes of the metastable and levels in . The lifetimes obtained were s for and s for . The most accurate results from ion trap measurements differ by 10% from each other. Our value for supports the longer lifetime value reported from Werths group. For the level, the new measurement is consistent with previous results.

The FERRUM project: transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes

Context. Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbi ...

Metastable levels in Sc II: lifetime measurements and calculations

The lifetime of the metastable level 3d(21)G(4) in a singly charged scandium has been experimentally investigated at the ion storage ring CRYRING. A laser probing technique has been used for the studies. We also report calculated lifetimes and transition rates for 10 metastable levels in Sc II, including the 3d(21)G(4) state, by calculations using configuration interaction wave functions. The lifetime of the (1)G(4) level is experimentally determined to be tau(exp) = 2.64 +/- 0.18 s and is in good agreement with the theoretical calculation tau(th) = 2.84 s.

The FERRUM project: Experimental and theoretical transition rates of forbidden [Sc II] lines and radiative lifetimes of metastable Sc II levels

Context. In many plasmas, long-lived metastable atomic levels are depopulated by collisions (quenched) before they decay radiatively. In low-density regions, however, the low collision rate may allow depopulation by electric dipole (E1) forbidden radiative transitions, so-called forbidden lines (mainly M1 and E2 transitions). If the atomic transition data are known, these lines are indicators of physical plasma conditions and used for abundance determination. Aims. Transition rates can be derived by combining relative intensities between the decay channels, so-called branching fractions (BFs), and the radiative lifetime of the common upper level. We use this approach for forbidden [Sc II] lines, along with new calculations. Methods. Neither BFs for forbidden lines, nor lifetimes of metastable levels, are easily measured in a laboratory. Therefore, astrophysical BFs measured in Space Telescope Imaging Spectrograph (STIS) spectra of the strontium filament of Eta Carinae are combined with lifetime measurements using a laser probing technique on a stored ion-beam (CRYRING facility, MSL, Stockholm). These quantities are used to derive the absolute transition rates (A-values). New theoretical transition rates and lifetimes are calulated using the CIV3 code. Results. We report experimental lifetimes of the Sc II levels 3d(2) a(3)P(0,1,2) with lifetimes 1.28, 1.42, and 1.24 s, respectively, and transition rates for lines from these levels down to 3d4s a(3)D in the region 8270-8390 angstrom. These are the most important forbidden [Sc II] transitions. New calculations for lines and metastable lifetimes are also presented, and are in good agreement with the experimental data.

Lifetimes of metastable levels of singly ionized titanium : theory and experiment

This paper presents new theoretical lifetimes of metastable levels in singly ionized titanium, Ti II. Along with the lifetimes, transition probabilities for several decay channels from these metast ...

Lifetime Measurements by Laser Probing in CRYRING – Recent Experimental Developments

A laser probing technique for lifetime measurements of long-lived metastable levels has been developed at the ion storage ring CRYRING. The method has been in use for about eight years and it has been applied to various ions. Levels with radiative lifetimes from a few milliseconds up to 28 s have been measured. The method has been continuously developed and this article is focused on recent experimental developments of the method in order to widen its applicability and to increase its efficiency and accuracy.