Gesellschaft Fur Schwerionenforschung Research Articles

Superheavy research in Japan

At RIKEN (The Institute of Physical and Chemical Research) in Japan, we have performed experiments to study the productions and decays of the heaviest elements produced by one-neutron emission channels of 208Pb and 209Bi based heavy-ion-induced fusion reactions. A gas-filled-type recoil separator has been used for collecting evaporation residues of the reactions separating them from high intensity beam particles. The reactions studied were 208Pb( 58Fe,n) 265Hs, 208Pb( 64Ni,n) 271Ds, 209Bi( 64Ni,n) 272Rg, 208Pb( 70Zn, n) 277112, and 209Bi( 70Zn,n) 278113. In studies of the first four reactions we have provided the independent confirmations of the productions and their decays of the isotopes, 265Hs, 271Ds, 272Rg, and 277112, as well as the decay properties of their decay daughters, previously studied by Hofmann et al., a group of Gesellschaft für Schwerionenforschung (GSI), Germany. In the last reaction, we observed two decay chains originated from the isotope 278113, assigned firstly by generic correlation of the alpha decay chains connected into the previously known decay of 266Bh and 262Db via previously unknown alpha decays of 278113, 274Rg and 270Mt.

Studies of high-energy density states using isochoric heating of matter by intense heavy ion beams: the HEDgeHOB Collaboration

During the past decade, substantial progress has been made in the technology of highly focused, strongly bunched intense beams of energetic ions. These developments have lead to a new concept of studying high energy density (HED) states in matter by isochoric and uniform heating of samples of matter by these intense particle beams. Existing accelerator facilities and those planned for the future, make the Gesellschaft für Schwerionenforschung (GSI), Darmstadt, a unique laboratory worldwide to carry out novel studies in this important field of research. Over the past few years, extensive theoretical work has been carried out to design novel experiments to study the thermophysical properties of HED matter. An overview of this work is presented in this paper highlighting the salient features of this new approach.

Search for oscillation of the electron-capture decay probability of 142Pm

We have searched for time modulation of the electron capture decay probability of 142Pm in an attempt to confirm a recent claim from a group at the Gesellschaft für Schwerionenforschung (GSI). We produced 142Pm via the 124Sn(23Na, 5n)142Pm reaction at the Berkeley 88-Inch Cyclotron with a bombardment time short compared to the reported modulation period. Isotope selection by the Berkeley Gas-filled Separator is followed by implantation and a long period of monitoring the 142Nd Kα x-rays from the daughter. The decay time spectrum of the x-rays is well-described by a simple exponential and the measured half-life of 40.68(53) seconds is consistent with the accepted value. We observed no oscillatory modulation at the proposed frequency at a level 31 times smaller than that reported by Litvinov et al. [Y.A. Litvinov, et al., Phys. Lett. B 664 (2008) 162]. A literature search for previous experiments that might have been sensitive to the reported modulation uncovered another example in 142Eu electron-capture decay. A reanalysis of the published data shows no oscillatory behavior.

In-beam PET measurement of 7Li3+ irradiation induced β+-activity

At present positron emission tomography (PET) is the only feasible method of an in situ and non-invasive monitoring of patient irradiation with ions. At the experimental carbon ion treatment facility of the Gesellschaft für Schwerionenforschung (GSI) Darmstadt an in-beam PET scanner has been integrated into the treatment site and lead to a considerable quality improvement of the therapy. Since ions other than carbon are expected to come into operation in future patient treatment facilities, it is highly desirable to extend in-beam PET also to other therapeutic relevant ions, e.g. 7Li. Therefore, by means of the in-beam PET scanner at GSI the β+-activity induced by 7Li3+ ions has been investigated for the first time. Targets of PMMA, water, graphite and polyethylene were irradiated with monoenergetic, pencil-like beams of 7Li3+ with energies between 129.1 A MeV and 205.3 A MeV and intensities ranging from 3.0 × 107 to 1.9 × 108 ions s−1. This paper presents the measured β+-activity profiles as well as depth dependent thick target yields which have been deduced from the experimental data. The β+-activity induced by 7Li ions was found to be a factor of 1.76 higher than the one induced by 12C ions at the same physical dose and particle range.

Numerical Calculations of the Magnetic Field of Bent Dipole Magnets

The high-energy storage ring (HESR) to be established as a part of the future facility for antiproton and ion research (FAIR) at gesellschaft fur schwerionenforschung (GSI) in Darmstadt (Germany) will be dedicated to studies with antiprotons in the momentum range from 1.5 GeV/c to 15 GeV/c. It will comprise 32 superconducting dipole magnets based on the RHIC DO design, yet with a radius of curvature of 15.279 m. The introduction of a finite radius is motivated by considerations both of field homogeneity along the particle path and available space for the HESR. On the other hand field distortions arise due to the curvature, which may compromise the advantage of the improved exploitation of the good-field region. This detrimental effect on our magnets has been quantified in this publication.

A Mole for Measuring Pulsed Superconducting Magnets

The facility for antiproton and ion research (FAIR) at Gesellschaft fur Schwerionenforschung (GSI) will build two superconducting synchrotrons requiring fields of up to up to 2 T at 4 T/s (SIS 100) and 6 Tesla at 1 T/s (SIS 300). The magnets of these rings will be measured using a mole which is currently under development. The main component of the field must be measured with a precision of 250 ppm and the higher order harmonics with a precision better than 100 ppm for DC and pulsed operation. This paper is focused on the pulse measurement using the "step by step" method.

Experiments on searching for the heaviest elements

At the Institute of Physical and Chemical Research (RIKEN) a series of experiments studying the productions and their decays of the heaviest elements have been performed by using a gas-filled recoil ion separator GARIS. Results on the isotope of the 112th element, 277112, and on that of the 113th element, 278113, are reviewed. Tow decay chains which are assigned to be ones originating from the isotope 277112 were observed in the 208Pb( 70Zn, n) reaction. Both chains consisted of four consecutive alpha decays followed by a spontaneous fission. The results provide a confirmation of the production and decay of the isotope 277112 reported by a research group at Gesellschaft für Schwerionenforschung (GSI), Germany, produced via the same reaction by using a velocity filter. Tow decay chains, both consisted of four consecutive alpha decays followed by a spontaneous fission, were observed also in the reaction 209Bi( 70Zn, n). Those are assigned to be the convincing candidate events of the decays of the isotope of the 113th element, 278113, and its daughter nuclei, 274Rg, 270Mt, 266Bh, and 262Db.

Effect of thermal annealing on pore density, pore size and pore homogeneity of polycarbonate NTFs

When an energetic and electrically charged beam of particles penetrates a nonconducting material, like crystal, polymer, etc., a permanent change in the nature of the chemical matrix along its path occurs giving rise to damaged sites known as latent tracks having diameter of the order of 10 nm. These tracks show an enhanced chemical reactivity as compared to the surrounding material; and, on etching, the damaged sites are enlarged forming nuclear track filters (NTFs). The NTFs so formed find applications in the fields as nuclear physics, geology, radiation dosimetry, material research, medicine and environmental studies. The pore density and pore size homogeneity are important traits of NTFs. These NTFs are also employed for the production of micro/nanostructures through template synthesis which finds various applications for the fabrication of sensors, devices and in the field of opto-electronics. The pore size of the NTF is generally not uniform due to various reasons like material defects in solid state nuclear track detectors (SSNTDs), nonuniform flux density of irradiating beam, variation in the angle of exposure during irradiation, temperature gradient in the etching solution, etc. The present work reports the development of NTFs and study of the effect of pre-etch thermal annealing of irradiated polycarbonate thin films (SSNTDs) on the density and homogeneity of etched pores in developed NTFs. NTFs were developed by irradiating Makrofol (KG) with heavy-ion beam at the UNILAC, Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany and then chemically etching of annealed and unannealed irradiated samples. The pore size, pore density and pore size homogeneity of the NTFs were compared for annealed and unannealed samples. The study indicates decrease in pore size, pore density and increase in homogeneity of pores with post-irradiation and pre-etch thermal annealing. The uniformity of the pores of NTF will lead to uniformity of micro/nanostructures fabricated by using the pores as templates. These uniform micro/nanostructures can act as excellent charge sprayers in the cold cathode emitters.

Heavy-Ion Beam Pumped UV Laser

Accelerators are mainly built to study collisions between the projectiles and individual particles in the target. There is, however, also an application of heavy ion accelerators where collective effects in the target such as heating, heat induced expansion, and compression of the target material is studied. Such experiments are for example performed by the plasma physics group at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany [1]. The experiment described here is closely related to these experiments and aims at the production of high population densities of electronically excited species in gas targets. It benefits from the efforts to produce high energy density in matter because it also requires pulsed high intensity ion beams with excellent beam quality. One particular goal is to study conditions where the target is not in thermodynamic equilibrium, and a clear indication that such a situation is obtained is the observation of laser effect from the target.

In-beam PET measurements of biological half-lives of 12C irradiation induced β+-activity

One of the long-standing problems in carbon-ion therapy is the monitoring of the treatment, i.e. of the delivered dose to a given tissue volume within the patient. Over the last 8 years, in-beam positron emission tomography (PET) has been used at the experimental carbon ion treatment facility at the Gesellschaft für Schwerionenforschung (GSI) Darmstadt and has become a valuable quality assurance tool.In order to determine and evaluate the correct delivery of the patient dose, a simulation of the positron emitter distribution has been compared to the measurement. One particular effect is the blurring as well as the reduction of the measured activity distribution via washout.The objective of this study is the investigation of tissue dependent effective half-lives from patient data. We find no significant dependence of the effective half-life on the Hounsfield unit but on the local dose. The biological half-life within the high dose region is longer than in the low dose region. Furthermore, the influence of the overall treatment time on the kinetics of the positron emitter is reported. There are indications for a metabolic response of the tissue on the irradiation. Taking into account the biological half-life in the simulation leads to an improvement of the quality of the PET-images in some cases.

Electrodeposition methods in superheavy element chemistry

To prepare electrodeposition experiments with superheavy elements (SHE), their homologs were investigated. In the experiments, various electrode materials and electrolytes were used. Critical potentials (E crit ) where the electrodeposition starts and potentials for the deposition of 50% of the atoms in solution (E 50% ) were determined. Underpotential deposition was observed in most cases. An electrolytic cell for a fast electrochemical deposition was developed and the time for the deposition of 50% of the atoms in solution (t 50% ) was determined. Short lived α-emitting isotopes were produced at Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, transferred to the aqueous phase with ALOHA (Automated Liquid Online Heavy element Apparatus), transported to an electrolytic cell and deposited on a palladinated Ni tape. It was shown that the coupling of devices for collection, electrodeposition, and α-spectroscopy is feasible and might be of great use in SHE chemistry.

4D treatment planning for scanned ion beams

At Gesellschaft für Schwerionenforschung (GSI) more than 330 patients have been treated with scanned carbon ion beams in a pilot project. To date, only stationary tumors have been treated. In the presence of motion, scanned ion beam therapy is not yet possible because of interplay effects between scanned beam and target motion which can cause severe mis-dosage. We have started a project to treat tumors that are subject to respiratory motion. A prototype beam application system for target tracking with the scanned pencil beam has been developed and commissioned.To facilitate treatment planning for tumors that are subject to organ motion, we have extended our standard treatment planning system TRiP to full 4D functionality. The 4D version of TRiP allows to calculate dose distributions in the presence of motion. Furthermore, for motion mitigation techniques tracking, gating, rescanning, and internal margins optimization of treatment parameters has been implemented. 4D calculations are based on 4D computed tomography data, deformable registration maps, organ motion traces, and beam scanning parameters.We describe the methods of our 4D treatment planning approach and demonstrate functionality of the system for phantom as well as patient data.

Numerical modeling of heavy ion induced stress waves in solid targets

AbstractThis paper presents numerical simulations of thermodynamic and hydrodynamic response for solid targets that are irradiated with strongly bunched, highly focused, intense beams of energetic uranium ions. The main purpose of this work is to study the behavior of thermal stress waves induced in such targets by the incident ion beam. These theoretical studies will complement the experimental investigations that will be carried out in the near future at the Gesellschaft für Schwerionenforschung (GSI) plasma physics experimental area. These experiments will be performed using the existing heavy ion synchrotron, SIS18, which delivers 4 × 109 uranium ions in a single bunch with a length of about 125 ns. Other time structures, for example, a pulse that consists of a series of bunches, are also possible. The particle energy is on the order of 400 MeV/u and the beam can be focused to sub millimeter radius. This information concerning material response under intense beam loading will have important implications on designing a viable production target for the superconducting fragment separator, Super-FRS, which is going to be constructed at the future facility for antiproton and ion research (FAIR), Darmstadt, Germany, for the production and separation of exotic nuclei.

A Method for System Matrix Construction and Processing for Reconstruction of In-Beam PET Data

At the experimental heavy ion therapy facility at the Gesellschaft fur Schwerionenforschung Darmstadt, Germany an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The fixed dual-head PET scanner, which is completely integrated into the treatment facility, registers the annihilation gamma-rays following the decay of minor amounts of beta+-radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. As the quality assurance monitoring using an in-beam PET can profit significantly from a rapid reconstruction, it is highly desirable to perform one using a fast converging algorithm, like OSEM. An influence of the quality of the system matrix calculation on the reconstruction results has to be evaluated. The method of system matrix calculation currently in use computes the system matrix on-the-fly using on-line intra-channel Monte Carlo simulation and delivers a rough approach. A new method for a precise calculation of the system matrix has been developed. By exploiting the system symmetries, in combination with an optimized interpolation and approximation strategies, the proposed method delivers the system response function in a continuous 3D image space with a high accuracy. The influence of the accuracy of the system matrix calculation on the results of MLEM and OSEM reconstructions has been evaluated for real treatment data.

Measurement of the fluence response of the GSI neutron ball dosemeter in the energy range from thermal to 19 MeV

At high-energy particle accelerators, area monitoring needs to be performed in a wide range of neutron energies. In principle, neutrons occur from thermal energies up to the energy of the accelerated ions, which is for the present GSI (Gesellschaft für Schwerionenforschung) accelerator facility approximately 1-2 GeV per nucleon. There are no passive dosemeters available, which are designed for the use at high-energy accelerators. At GSI, a neutron dosemeter was developed, which is suitable for the measurement of high-energy neutron radiation by the insertion of a lead layer around Thermoluminescence (TL) detection elements (pairs of TL 600/700) at the centre of the dosemeter. The design of the sphere was derived from the construction of the extended range rem-counters for the measurement of ambient dose equivalent H(10). In this work, the dosemeter fluence response was measured in the quasi-monoenergetic neutron fields of the accelerator facility of the PTB in Braunschweig and in the thermal neutron field of the GKSS research reactor FRG-1 in Geesthacht. For the accelerator measurements, the reactions (7)Li(p,n)(7)Be, (3)H(p,n)(3)He and (2)H(d,n)(3)He were used to produce neutron fields with energy peaks between 144 keV and 19 MeV. The measured fluence responses are 27% too low for thermal energies and show an agreement with approximately 14% for the accelerator produced neutron fields related to the computed fluence responses (MCNP, FLUKA calculations). The measured as well as the computed fluence responses of the dosemeter are compared with the corresponding conversion coefficients.

Measurement of the fluence response of the GSI neutron ball in high-energy neutron fields produced by 500 AMeV and 800 AMeV deuterons

Experiments were performed in Cave C of GSI (Gesellschaft für Schwerionenforschung) using the LAND (Large Area Neutron Detector) in combination with the deflection magnet ALADIN (A LArge DIpol magNet) in front of the LAND where charged particles and neutrons can be separated. This arrangement is used to create high-energetic neutron fields by irradiation of a thick lead target (5 cm) with deuteron beams with the energies of 500 or 800 MeV per nucleon. In break-up reactions the neutron is separated from the proton which is deflected in the magnetic field of the ALADIN. The produced neutron radiation, which has a pronounced peak at the nucleon energy, is used to measure the fluence response of the GSI neutron ball. A thermoluminescence (TL) based spherical neutron dosemeter was developed for the area monitoring for the quantity H(10) at high-energy accelerators. In the same experiment, the spectral neutron fluence Phi(E) is measured with the LAND in the energy range from 100 MeV to 1 GeV. The measured fluence responses are compared with results of FLUKA calculations and the corresponding fluence-to-dose conversion coefficients. The measured dosemeter responses are too high in comparison to the calculated ones (up to approximately 50%), the dosemeter reading gives dose values which are too high by a factor of 1.1-2.2 related to the corresponding fluence-to-dose conversion factors.

Experiment on Synthesis of an Isotope 277112 by 208Pb+70Zn Reaction

The production and decay of 277 112 have been investigated using a gas-filled recoil ion separator in irradiations of 208 Pb targets with a 70 Zn beam at 349.5 MeV. We have observed two α-decay chains that can be assigned to subsequent decays from 277 112 produced in the 208 Pb( 70 Zn,n) reaction. After emitting four consecutive α-particles, both the chains terminate by spontaneous fission decays of 261 Rf, and the decay energies and decay times of both the chains obtained in the present work agree well with those reported by a group at Gesellschaft fur Schwerionenforschung (GSI), Germany. The present result gives the first clear confirmation of the discovery of 277 112 and its α-decay product 273 Ds reported previously.

Quantification of β+ activity generated by hard photons by means of PET

Positron emission tomography (PET) as a method for quality assurance in radiotherapy is well investigated in the case of therapy with carbon ion beams and successfully applied at the Heavy Ion Medical Accelerator at Chiba (HIMAC), Japan, and the Gesellschaft für Schwerionenforschung (GSI), Germany. By measuring the β+ activity distribution during the irradiation (in-beam PET), valuable information on the precision of the dose deposition can be obtained. To extend this efficient technique to other radiation treatment modalities may be worthwhile. For example, since positron emitters are generated by high-energy photons with energies above 20 MeV due to (γ, n) reactions (predominantly 11C and 15O in tissue), in-beam PET seems to be feasible for radiation therapy with high-energy photons as also shown in Geant4 simulations. Quantitative results on the activation of tissue-equivalent materials at hard photon beams were obtained by performing off-beam PET experiments. Homogeneous PMMA phantoms as well as inhomogeneous phantoms were irradiated with high-energy bremsstrahlung. After the irradiation the distributions of the generated positron emitters in the phantoms were measured using a conventional PET scanner. Furthermore, the depth–dose distributions were determined by means of optically stimulated luminescence detectors. In the experiments an activity per dose comparable to that produced in a typical patient irradiation with carbon ions could be achieved for 34 MV bremsstrahlung. In addition, a high contrast in the PET images for materials with different density and stoichiometry could be detected. Thus, further research concerning the development of in-beam PET seems to be worthwhile.

Effectiveness of Carbon Ion Radiotherapy in the Treatment of Skull-Base Chordomas

The aim of this study was to evaluate the effectiveness and toxicity of carbon ion radiotherapy in chordomas of the skull base. Between November 1998 and July 2005, a total of 96 patients with chordomas of the skull base have been treated with carbon ion radiation therapy (RT) using the raster scan technique at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany. All patients had gross residual tumors. Median total dose was 60 CGE (range, 60-70 CGE) delivered in 20 fractions within 3 weeks. Local control and overall survival rates were calculated using the Kaplan-Meier method. Toxicity was assessed according to the Common Terminology Criteria (CTCAE v.3.0) and the Radiation Therapy Oncology Group (RTOG) / European Organization for Research and Treatment of Cancer (EORTC) score. Mean follow-up was 31 months (range, 3-91 months). Fifteen patients developed local recurrences after carbon ion RT. The actuarial local control rates were 80.6% and 70.0% at 3 and 5 years, respectively. Target doses in excess of 60 CGE and primary tumor status were associated with higher local control rates. Overall survival was 91.8% and 88.5% at 3 and 5 years, respectively. Late toxicity consisted of optic nerve neuropathy RTOG/EORTC Grade 3 in 4.1% of the patients and necrosis of a fat plomb in 1 patient. Minor temporal lobe injury (RTOG/EORTC Grade 1-2) occurred in 7 patients (7.2%). Carbon ion RT offers an effective treatment option for skull-base chordomas with acceptable toxicity. Doses in excess of 75 CGE with 2 CGE per fraction are likely to increase local control probability.

Photorecombination studies of highly charged ions at the storage ring ESR: a progress report

In this contribution, we report on photorecombination measurements of highly charged ions (HCI) that were performed using the electron cooler of the heavy-ion storage ring ESR of the Gesellschaft für Schwerionenforschung (GSI) as a target of free electrons. The experimental technique of resonance reaction spectroscopy by means of dielectronic recombination (DR) was employed in two new ways:The determination of isotope shifts in the DR resonance spectrum of few-electron heavy ions is a novel method with unique properties for investigations at the interface between electrons and the atomic nucleus, e.g., charge radii and hyperfine effects. First results from a pilot experiment with the two isotopes A = 142 and A = 150 of Li-like neodymium ANd57+ are discussed.Until very recently, electron-ion collision experiments at high relative energies of more than a few keV were not accessible at the electron coolers of storage rings. Such high energies are needed to access DR processes that involve the K-shell electrons of very heavy ions. The novel approach of DR measurements with a stochastically (pre-)cooled ion beam resolves this problem. Results for the photorecombination of hydrogen-like U91+ in the energy range (63 keV - 74 keV) of the KLL-DR process are presented.