L. Mårtensson

Model-based pulse shape correction for CdTe detectors

Abstract We present a systematic method to improve energy resolution of CdTe-detector systems with full control of the efficiency. Sampled pulses and multiple amplifier data are fitted by a model of the pulse shape including the deposited energy and the interaction point within the detector as parameters. We show the decisive improvements of spectral resolution and photo-peak efficiency that is obtained without distortion of spectral shape. The information concerning the interaction depth of individual events can be used to discriminate between beta particles and gamma quanta.

Isospin resolved double pion production in the reaction p+d→3He+2π

Abstract Neutral and charged two-pion production in p+d→ 3 He+2 π reactions has been studied at CELSIUS at a proton beam energy of 477 MeV. The total cross section for double pion production is 0.22±0.03 μ b. The ratio of the cross sections for the production of charged pion pairs with isospin T =1 and T =0 was determined to be σ ( π + π − ; T =1)/ σ ( π + π − ; T =0)=1.4±0.4.

Status of the Milano neutrino mass experiment with arrays of AgReO4 microcalorimeters

Abstract In this paper we report on the status of the Milano calorimetric neutrino mass experiment. We have performed a first 3.5 month run with 8 AgReO 4 detectors to measure the β-decay of 187 Re. In the following we present the preliminary results of the analysis of the collected data.

Digital pulse-shape processing for CdTe detectors

Abstract CdTe detectors suffer from low photo-peak efficiency and poor energy resolution. These problems are due to the drift properties of charge carriers in CdTe where particularly the holes have small mobility and trapping time. This is reflected in the amplitude and the shape of the detector output. To improve this situation a digital method is introduced where a sampling ADC is used to make a detailed measurement of the time evolution of the pulse. The measured pulse shape is fitted with a model. For the detector under study a model taking hole trapping into account significantly improves the photo-peak efficiency. The description of the hole component is, however, not fully satisfactory since for pulses with a large hole contribution a broadening of the full-energy peak occurs. Allowing for inhomogeneities in the detector material within the model partially remedies this deficiency.

Pionic fusion to a halo state, the d(α,6Li∗)π0 reaction studied close to threshold

Abstract The d(α,6Li ∗ 3.56 )π0 reaction has been studied at Ec.m.=1.2 and 1.9 MeV above threshold with an alpha-particle beam incident on a deuterium cluster-jet target in CELSIUS. Complete differential cross sections were measured at both energies, integrated to σ=228±6+70 nb and 141±12+42 nb respectively. Observed large anisotropies are discussed in relation to the cluster structure of the 6Li ∗ halo.

Using a CdTe detector for 125Te Mössbauer Spectroscopy: Application to the f-factor in Mg3TeO6

Abstract An apparatus for Mossbauer spectroscopy has been developed with a cadmium telluride (CdTe) γ-ray detector. Complete data regarding γ-ray energy, source velocity, temperature and real time are stored for off-line analysis. The apparatus has been used to study the spectrum of 125Te in Mg3TeO6 at room temperature. The 35.5 keV transition of 125Te in Mg3TeO6 was found to have a recoil-free fraction f=0.392(5) corresponding to a Debye temperature θ=352(3) K.

Pionic Fusion Study of the Halo Nucleus 6He in the Reaction d + 14N -g 6He + pi+ at CELSIUS

The halo nucleus 6He has been studied in a pionic fusion experiment at the CELSIUS storage ring facility in Uppsala. The 6He nuclei were produced in reactions with a deuteron beam incident on a 4He jet target 0.9–5.4 MeV above threshold in the center-of-mass frame. The 6He ions were detected in a ΔE-E solid-state detector telescope inserted into the CELSIUS ring. The aim of the experiment was to investigate, in particular, the high-momentum part of the halo wave function by measuring the total and differential cross sections of the reaction d+4He→6He+π+.

Effects of inhomogeneous material properties on CdTe detector pulse-shape processing

Abstract Pulse-shape processing for CdTe detectors is described using sampled pulse shape data that are fitted with a detailed model. We show that in order to obtain satisfactory results it is necessary to take into account inhomogeneities in the detector material.