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Summary form only received as follows: A system of three dimensional raster scanning carbon beams used for cancer therapy has been designed and built at GSI and has been in operation since the end of 1998. The front-end real-time system is based on VME boards with DSPs designed and built at GSI. The system is operated in two modes: first, the treatment mode. The beam is steered automatically according the patient's treatment plan. During the treatment a real-time visualization of the scanning process is required without any possibility of distortion. Therefore all needed data measured by the front-ends is sent from one of the DSPs via a separate bus to a sufficiently big memory located in a different VME crate. A processor in this crate sends the data as it arrives in the memory via TCP to the monitor program running on an AIX machine where it is displayed in nearly real-time. In experimental mode the same system is used for quality control of the beam before the treatment. The measured beam positions and shapes are sent through the same data channel to an analysis package developed at GSI. Both, monitoring and analysis, use IDL from Research Systems Inc. for visualization.

The unique combination of an intense heavy ion beam accelerator and a high energy laser opens the possibility of exploring new physics taking advantage of the synergy of both facilities. A variety of new fields can be addressed with this combination in plasma physics, atomic physics, nuclear- and astro-physics as well as material research. In addition, using CPA-technology, laser pulses with a pulse power of up to a petawatt opens the door to explore the regime of fully relativistic plasmas. Therefore the Gesellschaft fuer Schwerionenforschung is augmenting the current high intensity upgrade of the heavy ion accelerator facility with the construction of PHELIX. Designed with two pulse-generating front ends and send to multiple experimental areas PHELIX will serve as a highly versatile laser system for various applications. In this report, we present the design of the laser system and some key experiments that can be performed with this combination for the first time.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Evaporation residues from the heavy-ion fusion reaction50Ti on209Bi were investigated. They were separated from the projectile beam by the velocity filter SHIP and identified after implantation into an array of position-sensitive surface-barrier detectors by analyzing theirα-decay chains. Spontaneous fission was also observed.

Results of experiments to synthesize the heaviest elements are reported. Surprising is the high stability against fission not only of the odd and odd-odd nuclei but also of even isotopes of even elements. Alpha decay data gave an increasing stability of nuclei by shell effects up to 266 109, the heaviest known element. Theoretically, the high stability is explained by an island of nuclei with big quadrupole and hexadecapole deformations around Z = 109 and N = 162. Future experiments will be planned to prove the island character of these heavy nuclei.

The longitudinal polarization of electrons from theΒ-decay of210Bi has been measured near the endpoint energy using MOller-scattering. The valuePL=(−0.718±0.0244)v/c obtained from this experiment has much smaller uncertainty than previous data and allows a more accurate redetermination of the nuclear parametersx1=Cv∫α,x2=Cv∫ir/R,x3=CA∫/gs×r/R. In addition, an improved determination of the parametersX andY defined by Fujita under the assumption of the validity of the CVC theory has been performed. The results are compared with various shell-model predictions.

Evaporation residues from the fusion reactions 48 Ca+ 206,208 Pb and 50 Ti + 207,208 Pb, 209 Bi were investigated using the velocity filter SHIP. Four new isotopes 258,257 105 and 254,253 Lr were identified and α decay of 255 104 and 256 104 was observed for the first time. A hindrance to complete fusion by a factor of about 30 at bombarding energies close to the classical barrier was deduced from a measured excitation function for 50 Ti + 208 Pb. The mass extents for 256 104 and 260 106, obtained from their α-decay energies, were used to determine the ground-state shell effects and a semi-empirical description of the half-life T SF for even-even nuclei. The abrupt decrease in T SF for elements from nobelium to element 104 was found to be correlated with a decrease in the fission barrier width, which we regard as confirmation of the expected drop in the outer fission barrier to below the ground state. The total kinetic energies released in SF of 256 104 and 258 104 were measured and found to be 207 ± 13 MeV and 220 ± 15 MeV respectively. These values agree with those predicted from empirical systematics.

A search for superheavy elements was made in bombardments of $^{248}\mathrm{Cm}$ with $^{48}\mathrm{Ca}$ ions performed at projectile energies close to the interaction barrier in order to keep the excitation energy of the compound nucleus $Z=116$, $A=296$ as low as possible. No evidence for superheavy nuclei was obtained in a half-life region from 1 \ensuremath{\mu}s to 10 yr with a production cross section greater than ${10}^{\ensuremath{-}34}$ to ${10}^{\ensuremath{-}35}$ ${\mathrm{cm}}^{2}$.

Elasticα-scattering angular distributions have been measured atEα=36.2 MeV, 39.6 MeV, 42.6 MeV, 49.5 MeV, 61.0 MeV for40Ca and atEα=36.2 MeV, 42.6 MeV, 49.5 MeV and 61.0 MeV for44Ca, respectively. At backward angles the data display an oscillatory structure forEα 12 than forL

An experiment to synthesize element 109 is presented. Decay patterns characteristic of complete fusion products were searched for in an irradiation of209Bi targets with58Fe projectiles at specific incident energies of 4.95, 5.05, and 5.15 MeV/u. A total dose of 7 ×1017 particles was obtained. The experimental method involves in-flight separation of forward peaked reaction products with a static-field velocity filter, their passage through a time-of-flight device and their final implantation into position sensitive solid state detectors to measure their kinetic energy, approximate mass and their time and position of incidence. The subsequent decay of the narrowly localised reaction products by cascades of alpha particles and/or spontaneous fission is also registered in terms of the energies and times of all the emitted particles. One outstanding decay sequence that started with the emission of two alpha particles within subsequent time intervals of 5 ms and 22 ms and ended with spontaneous fission after 13 s was found at 5.15 MeV/u. The first alpha particle had a kinetic energy of (11.10±0.04) MeV. A detailed analysis of all the alternative interpretations of this observation, such as a purely random correlation of signals, the decay of a product from a transfer reaction or of any of the various energetically possible evaporation residues, shows that the isotope with mass 266 of element 109, i.e. the one neutron evaporation channel after complete fusion, is the statistically most significant assignment. The outlook for new element synthesis is also briefly discussed.

The experiment having led to the discovery of first isotopes of element 108, as published previously in Short Notes to this Journal [1, 2] are described and discussed in a final paper.

In irradiations of207Pb and208Pb, respectively, with54Cr theα-decay of the isotopes259106,260106, and261106 could be observed for the first time. For260106 a spontaneous fission branch of (50 −20 +30 )% was observed. The isotopes were identified by genetic relationships of α-decay after separation in-flight with the velocity filter SHIP and implantation into a position-sensitive silicon surface-barrier detector. The measured partial fission halflife of the doubly even isotope260106 of (7.2 −2.7 +4.8 )ms exceeds the predicted values by at least a factor of 40. This result could be explained by the high shell corrections of the ground state mass, derived from the measured α-decay energies. The experimental results show evidence for an island of purely shell stabilized nuclei in the region of deformed isotopes beyond the actinides.

The elasticα-scattering from40Ca has been studied betweenE α=7.035 MeV and 7.405 MeV. Angular distributions and excitation functions have been measured in 5 keV steps. The data display a resonance atE α=7.26 MeV which by its width and angular correlation is clearly distinguished from strong Ericson fluctuations in this region. From the analysis of the angular distributions and excitation functions a spinJ π=1− is assigned to this resonance. The resonance parameters areΓ α=31 KeV,Γ total=51keV. By its spin and excitation energy this state is interpreted as a member of a quasimolecular band in44Ti the higherl-members of which are known from401Ca(α, α) scattering betweenE α=18 MeV and 50 MeV. The experimental data are compared with recent microscopic calculations within a fully antisymmetrized reaction theory.

Attempts were made to identify new elements in heavy ion fusion reactions. After an effective separation by the velocity filter SHIP the ions passed a pair of thin secondary electron detectors and were finally implanted into position sensitive Si-detectors. With these techniques the odd elements 105, 107, and 109 have been investigated in the years 1981 and 1982. The even elements 106 and 108 have been studied in the year 1984, and in 1985 attempts were made to produce element 110. So far in most experiments 208Pb and 209Bi targets have been irradiated with beams of 50Ti, 54Cr, 58Fe, and 64Ni. In a recent experiment (April/May, 1986) the decay of the ee nucleus 264108 was measured. This isotope was produced in the reaction 58Fe+207Pb with a cross section of (3.2 -2·6 +6·1 ) pb. The nucleus 264108 decays by α emission with a half-life of (76 -35 +365 ) μs. A deduced α energy is (10.8 -0·3 +0·1 ) MeV. Also 260106 is decaying by a emission with a branching of 50%. The decay sequence 264108(α) → 260106(α) → 256104(sf) demonstrates that the heavier element isotopes 264108 and 260106 are more stable against fission than the lighter element isotope 256104. The mass excesses of 264108 and 260106 are (120.0±0.3) MeV and (106.58+0.10) MeV, respectively. The values are obtained by α chain summation. The investigated isotopes are situated near the center of a shell stabilized region of deformed nuclei. The fission barriers for the discovered isotopes are mainly due to shell correction energies. Values as large as 5 MeV have been deduced from the data.

A search for superheavy elements which are expected to occur around the predicted nuclear shell closures at atomic number 114 and neutron number 184 was made in bombardments of 248 Cm with 48 Ca ions. We have carried out this search at energies close to the Coulomb barrier to keep the excitation energy of the compound nucleus Z = 116, A = 296 as low as possible. The experiments were performed at the accelerators SUPERHILAC (Lawrence Berkeley Laboratory (LBL)) and UNILAC (GSI) and used a variety of improved physical and chemical techniques for the isolation and detection of superheavy elements to increase the sensitivity relative to earlier experiments. The small-angle separator system (SASSY) at LBL and the separator for heavy-ion reaction products (SHIP) at GSI were used for shortlived nuclides, and several radiochemical techniques were applied for longer half-lives. Although a broad range of half-lives, 10 −6 to 10 8 s, and excitation energies, 16 to 40 MeV, has been examined, no evidence for the formation of superheavy elements with cross sections greater than 10 −34 to 10 −35 cm 2 was found.

Electron spectra have been measured for elastic and dissipative U + Au collisions at 8.6 MeV/u and analysed within a simple schematic model which describes γ-ray emission in the presence of a nuclear contact time and a total kinetic energy loss (TKEL). A nearly linear dependence of the mean nuclear contact time τ and TKEL was found, reaching τ = 1.1 * 10-21 s with a variance σ = ±0.4 * 10-21 s for a TKEL of (400 ± 50) MeV.

The major problems in the investigation of the heaviest elements at the upper end of the periodic table are the small formation cross sections which are far below the nanobarn region and their short halflives of the order of milliseconds. The heaviest elements known up to now were I07 and I09. Two a-emitting odd-odd isotopes of these elements were identified by a-chains to known daughter isotopes /1,2/. Element I08 could not be observed so far /3,4/. Our aim was to produce element 108 by complete fusion of S'Fe with 2~ followed by evapora- tion of one neutron which leads to the odd mass isotope '6sI08. To allow an unambiguous identi- fication of the new element in case of its a-decay, we had also to investigate the unknown daughter isotope 2~I06.

We have observed the decay of one atom of the doubly even isotope 108. We observed α-decay with a halflife, of (76 −36 +364 ) Μs. The full α-decay energy could not be measured, as the α escaped the detector. With the knowledge of the halflife, an estimate on the α-decay energy can be made. From the formula of Rasmussen9 and a reduced α-width of 1, a value which has been measured for260106 and also for the doubly even isotones of N=156, we obtain Q=(11.0 −0.3 +0.1 MeV. This value is higher than given by Moeller10 (10.35 MeV), and agrees with that of Uran and Zeldes11 (10.9 MeV). A hindrance factor wα of 0.5 increases the Qα-value by 0.14 MeV. The mass excess of264108 follows as (120.0±0.3) MeV. The groundstate shell effect amounts to (−5.0±0.3) MeV using the macroscopic mass values of Ref. 10. The formation cross section of (3.2 −2.6 +6.1 ) pb overlaps with the value of ∼ 5 pb from Dubna for the 6 ms sf-activity mentioned initially but is considerably lower than an extrapolation from the reaction58Fe (208Pb,n)265108 which gave 10 pb with the lower limit of 4 pb.

The reactions58Ni+102Pd→160W and58Ni+106Cd→164Os were investigated to search for new decay data of neutron deficient nuclei. Excitation energies of the compound nuclei covered a range from 47 to 89 MeV. Velocity separation of the evaporation residues and position time correlations with the a decays of the implanted nuclei were used. The following new decay data were measured:162Os (Eα=(6611 ±30) keV, T1/2=(1.9±0.7) ms);158W (T1/2=(0.9±0.3) ms);158mW (E=1.88 MeV, Eα=(8280±30) keV, T1/2=(0.01-1) ms);155mLu (Eα=(5575±10) keV); β decay of156Ta (T1/2 > 10 ms) to the 8+ yrast isomer in156Hf. A cross section of 5μb was measured for the new isotope156Ta produced in a p3n evaporation channel from160W at 64 MeV excitation energy.