D. M. Seliverstov

Mass measurements in the vicinity of the r p-process and the nu p-process paths with the Penning trap facilities JYFLTRAP and SHIPTRAP

The masses of very neutron-deficient nuclides close to the astrophysical r p- and {nu} p-process paths have been determined with the Penning trap facilities JYFLTRAP at JYFL/Jyvaeskylae and SHIPTRAP at GSI/Darmstadt. Isotopes from yttrium (Z=39) to palladium (Z=46) have been produced in heavy-ion fusion-evaporation reactions. In total, 21 nuclides were studied, and almost half of the mass values were experimentally determined for the first time: {sup 88}Tc, {sup 90-92}Ru, {sup 92-94}Rh, and {sup 94,95}Pd. For the {sup 95}Pd{sup m}, (21/2{sup +}) high-spin state, a first direct mass determination was performed. Relative mass uncertainties of typically {delta}m/m=5x10{sup -8} were obtained. The impact of the new mass values has been studied in {nu} p-process nucleosynthesis calculations. The resulting reaction flow and the final abundances are compared with those obtained with the data of the Atomic Mass Evaluation 2003.

Mass Measurements and Implications for the Energy of the High-Spin Isomer in 94Ag

Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Isotope Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag have been deduced. When combined with the data from the one-proton- or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in 94Ag, -46 370(170) or -44 970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively.

Fine-mesh photodetectors for CMS endcap electromagnetic calorimeter

The behaviour of fine-mesh vacuum phototriodes (VPTs) with the external diameters of 21 and 25 mm has been investigated in an axial magnetic field up to 4 T in view of their applications as readout devices for CMS Endcap Electromagnetic Calorimeter. The measured VPT parameters are: the photocathodes sensitivity and its homogeneity, the gain in zero and 4 T magnetic field at tilt angles corresponding to the pseudorapidity range of CMS ECAL Endcap 1.48–3.0 as a function of fine-mesh cell dimensions, excess noise factor and the stability of the photocathode response under the illumination by light emission diodes (LED) and the irradiation by 14 MeV neutrons. Phototriodes with 100 lines per mm fine-mesh and 25 mm external diameter are found to be the best candidates for coupling with rear PbWO4 crystals by dimensions of 30×30 mm, proposed to be used in CMS ECAL Endcaps. VPTs provide a gain of the order (6–8) in a 4 T magnetic field and an excess noise factor of 2–2.5 under illumination of a full photocathodes area.

Beta-decay half-lives of 70Kr and 74Rb

Abstract Beta-decay half-lives of two nuclei close to N = Z line, 70 Kr and 74 Rb, have been measured at the ISOLDE mass-separator facility at CERN. Importance of these half-lives on two ingredients explaining existence and development of the Universe, the astrophysical nucleosynthesis and the Standard Model, are discussed.

Performance and testing of Russian mesh photomultiplier tubes for high magnetic field environments

Abstract Future experiments on RHIC and LHC require the performance of photodetectors with stable operation in strong magnetic fields, 0.5 T for the STAR (RHIC) Time of Flight system (TOF) and more than 3 T for the CMS (LHC) electromagnetic calorimeter. Such photodetectors have to possess a good energy and time resolution, for TOF measurements less than 100 ps [1] simultaneously being radiation hard up to some Mrad. Fine mesh dynode proximity photomultiplier tubes FMPMT developed and produced in recent years by Hamamatsu are the most promising detectors for the above specified goals. Different kinds of PMT were tested by some experimental groups in axial magnetic field up to 1.5 T [2–4]. The obtained PMT time resolution in beam test together with Bicron scintillator was better than 100 ps [1].

Vector and tensor analyzing powers of theH1(d→,γ)He3capture reaction

Precise measurements of the deuteron vector analyzing power A(y)(d) and the tensor analyzing power A(yy) of the H-1(d(-<),gamma)He-3 capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.Precise measurements of the deuteron vector analyzing power A{sub y}{sup d} and the tensor analyzing power A{sub yy} of the {sup 1}H (d(vector sign),{gamma}){sup 3}He capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.

Vector and tensor analyzing powers of the ¹H (d⃗,γ)³He capture reaction

Precise measurements of the deuteron vector analyzing power A(y)(d) and the tensor analyzing power A(yy) of the H-1(d(-<),gamma)He-3 capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.Precise measurements of the deuteron vector analyzing power A{sub y}{sup d} and the tensor analyzing power A{sub yy} of the {sup 1}H (d(vector sign),{gamma}){sup 3}He capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.

Vector and tensor analyzing powers of the {sup 1}H (d(vector sign),{gamma}){sup 3}He capture reaction

Precise measurements of the deuteron vector analyzing power A(y)(d) and the tensor analyzing power A(yy) of the H-1(d(-<),gamma)He-3 capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.Precise measurements of the deuteron vector analyzing power A{sub y}{sup d} and the tensor analyzing power A{sub yy} of the {sup 1}H (d(vector sign),{gamma}){sup 3}He capture reaction have been performed at deuteron energies of 29 MeV and 45 MeV. The data have been compared to theoretical state-of-the-art calculations available today. Due to the large sensitivity of polarization observables and the precision of the data light could be shed on small effects present in the dynamics of the reaction.

Studying exotic nuclides close to the N = Z line at the HIGISOL facility

The ion guide [1, 2] for heavy-ion fusion-evaporation reactions (HIGISOL) which was developed by Beraud et al. [3] has been implemented at the IGISOL facility in Jyvaskyla [4]. This system was modified over the past 5 years. Figure 1 shows the present set-up. The HIGISOL takes advantage of the different angular distributions of primary beam and reaction products: the primary beam is stopped in front of the stopping chamber and the reaction products enter the stopping chamber through a thin foil passing the beam stop. This so called “shadow” method removes the plasma effect since the primary beam is not ionising the stopping gas. In order to improve ion optical properties, mainly to reduce the energy spread, the normal skimmer system was replaced by a sextupole ion guide, SPIG. The mass resolving power (MRP) for a 219Rn ion beam was measured to be 1100, independent of the helium pressure and SPIG DC voltage level relative to the stopping chamber [6]. The MRP measured earlier with the skimmer was 250 for 219Xe [4].

Isomeric state of 80Y and its role in the rp-process

The HIGISOL facility has been used to investigate carefully the isomeric transition 228.5 keV in 80Y. We have measured the electron internal conversion coefficient for this transition αK = 0.50 ± 0.07 which gives the value for half-life of “bare” isomeric state T 1/2 = 6.8 ± 0.5 s. The isomeric state should play an important role in the rp-process calculations.