A. Fenyvesi

Pulse height distribution and radiation tolerance of CVD diamond detectors

The paper reviews measurements of the radiation tolerance of CVD diamond for irradiation with 24 GeV/c protons, 300 MeV/c pions and 1 MeV neutrons. For proton and neutron irradiation, the measured charge signal spectrum is compared with the spectrum calculated by a model. Irradiation by particles causes radiation damage leading to a decrease of the charge signal. However, both the measurements and the outcome from the model shows that for tracker applications this drawback is at least partly counterbalanced by a narrowing of the distribution curve of the charge signal. In addition, we observed after proton irradiation at the charge signal spectrum a decrease of the number of small signals. As a result, the efficiency of a CVD diamond tracker is less affected by irradiation than the mean charge signal. (11 refs).

Radiation-hardness studies of high OH- content quartz fibres irradiated with 500 MeV electrons

We investigated darkening of nine fiber types while irradiated with 500 MeV electrons of the Linac injector of LEP (LIL) at CERN. The transmission of Xe light by irradiated fibers was measured in-situ in 350-750 nm range. The induced attenuation at 450 nm is typically (1.52 + 0.15) dB/m for a 100 Mrad absorbed dose. Two-parameter fits for darkening and recovery are presented. After irradiation the tensile strength of the samples remain essentially unchanged. A tensile strength of (4.94 + 0.37) GPa was measured for Polymicro quartz fibers.

On the differences between high-energy proton and pion showers and their signals in a non-compensating calorimeter

Abstract We present the results of experimental studies of hadron showers in a copper/quartz-fiber calorimeter, based on the detection of Cherenkov light. These studies show that there are very significant differences between the signals from protons and pions at the same energies. In the energy range between 200 and 375xa0GeV, where these studies were performed, the calorimeter’s response to protons was typically 10% smaller than the response to pions. On the other hand, the energy resolution was about 25% better for protons. In addition, the protons had a Gaussian line shape, whereas the pion response curve was asymmetric. These differences can be understood from the requirements of baryon number conservation in the shower development. They are expected to be present in any non-compensating calorimeter, to a degree determined by the e / h value.

Improvement of the dosimetric properties of chemical-vapor-deposited diamond films by neutron irradiation

The performance of chemical-vapor-deposited (CVD) diamond films as on-line dosimeters has been substantially improved after irradiation with fast neutrons up to a fluence of 5×1014u2009n/cm2. This is correlated to a decrease of more than one order of magnitude in the concentration of deep levels with activation energy in the range 0.9–1.4 eV, as observed by thermally stimulated current and photoinduced current transient spectroscopy. As a consequence, a fast and reproducible dynamic response is observed during irradiation with a 6 MV photon beam from linear accelerator and with a Co60 source. A quasilinear dependence of the current on the dose rate is obtained in the range of interest for clinical applications (0.1–10 Gy/min). The resulting sensitivity is definitely higher than that of standard ionization chambers, and compares favorably with those of standard silicon dosimeters and of best-quality natural and CVD diamond devices.

Validation of neutron data libraries by comparison of measured and calculated neutron leakage spectra

Abstract Neutron spectra from the 2H(d,n)3He and 9Be(d,n)10B neutron source reactions and a Pu–Be source were measured by a pulse height response spectrometer behind slabs of water, graphite, sand, Pb, Al and Fe up to 20xa0cm thicknesses. A comparison of the measured and the calculated data has given new results for the validation of different data libraries.

New cross-sections for production of 103Pd; review of charged particle production routes

Production cross-sections of (103)Ag obtained by irradiating (nat)Pd and (nat)Cd with 70 MeV protons are presented and compared with ALICE-IPPE model calculations. Production of (103)Ag is of interest for the generation of (103)Pd widely used in brachytherapy. The investigated energy range of the (103)Rh(d,2n)(103)Pd reaction was extended up to 40 MeV and the results were compared with the curves of ALICE-IPPE, EMPIRE-II and GNASH theoretical codes. Thick target yields were calculated. An overview and analysis of the most important charged particle induced production routes of (103)Pd is presented. An explanation of the apparent discrepancy in the activity measurements for (103)Rh based on X- or gamma-ray is given.

Excitation function and thick target yield of the 40Ar(α,p)43K reaction: Production of 43K

Abstract The excitation function of the 40Ar(α,p)43K nuclear reaction has been measured via the activation technique using stacked gas cell targets. Absolute cross section values were deducted from the experimental data and were compared with theoretical predictions calculated by means of the STAPRE code. Thick target yields of 43K were calculated from the experimental data. A target system working in static (batch) or in recirculating gas flow mode has been developed to produce 43K.

Measurements and calculations of neutron leakage spectra from slabs irradiated with 9Be(d, n)10B 2H(d, n)3He and Pu-Be neutrons

Abstract The spectra of neutrons from the 9 Be(d, n) 10 B, 2 H(d, n) 3 He and Pu–Be sources passing through slabs of water, graphite, Al, Fe and Pb up to 20xa0cm in thickness were measured by a pulse height response spectrometer in the 1.5–15xa0MeV range. The measured leakage spectra have been compared with calculated results obtained using the three dimensional Monte-Carlo code MCNP-4A and point-wise cross sections from the ENDF/B-IV, ENDF/B-VI and JENDL-3.1 data files. A comparison of the measured and calculated data has shown that the MCNP-4A code with an appropriate library can reasonably approximate the measured leakage spectra.

Excitation Functions of natNe(3He,x)22,24Na and natNe(αr,x)22,24Na Processes: Investigation of Production of 22Na and 24Na at a Medium-Sized Cyclotron

Excitation functions were measured for Heand a-particle induced nuclear reactions on natural neon leading to the formation of ^̂ Na and Na from their respective thresholds up to 36 MeV in the case of He-particles and up to 27 MeV for a-particles. Use was made of the stacked-gas cell technique. A comparison of production yields of ^^Na and Na via various low energy (Eprojeciiie —40 MeV) routes is given. ^̂ Na can be produced at a low energy multiparticle accelerator using proton, Heor oparticle induced reactions on neon, the highest yield being provided by protons. For Na production, the ^^Mg(d,o) reaction is most suitable.

Seasonal and diurnal variability in sap flow intensity of mature sessile oak (Quercus petraea (Matt.) Liebl.) trees in relation to microclimatic conditions.

In this study sap flow dynamics of mature sessile oak trees (Quercus petraea) in a marginal sessile oak-turkey oak forest was investigated in 2009. That year spring was dry without significant rain in April and May and the driest month was August. Due to the extreme weather conditions the volumetric soil water content (SWC) of upper 30 cm was low on experimental days in May (0.13-0.14 cm3 cm-3) but it reached the lowest value in August (0.08 cm3 cm-3). Sap flow was measured in a dominant and a co-dominant tree by heat dissipation method from 26 March till 30 October. In the present paper several three-day long periods of the continuous seasonal recordings were chosen to represent the effects of typical weather conditions and different stages of canopy development on sap flow dynamics. The daily maximum sap flow density values of dominant and co-dominant trees were similar (0.30-0.32 cm3 cm-2 min-1) in moist period (July). Rains and transient increase of SWC after proceeding drought resulted in change of diurnal course of sap flow in experimental days of July. In this period dominant trees also showed considerable sap flow (0.19 cm3 cm-2 min-1) during night hours and short sap flow peaks in early morning (6:00 to 8:00 a.m.) indicating the refilling of desiccated tissues. After the progressive drought in August the daily maximum sap flow density decreased to 0.07 cm3 cm-2 min-1 in dominant tree and to 0.12 cm3 cm-2 min-1 in the co-dominant. Both trees exhibited gradual stomatal closure from morning hours.